Disease-related
Psychological
Social and environmental
Anorexia
Depression
Social instability
Dementia
Bereavement
Financial issues
Gastrointestinal symptoms
Mental illness
Social isolation
Pain
Psychosis
Access to shops
Co-morbidities, e.g. diabetes
Anxiety
Cooking and food storage facilities
Poor dentition
Apathy
Religion
Chewing difficulties
Poor motivation
Cultural meanings of illness and food
Swallowing problems
Loneliness
Support from family and informal carers
Altered taste and smell
Low self-esteem
Social networks
Medication
Dependence
Access to formal social care services
Impaired mobility
Substance abuse
Access to health services
Homelessness
Dyspraxia
Poor eyesight
Fatigue
Early satiety
Detection
Malnourished individuals, or those who have been identified as at medium or high risk of malnutrition, are more likely to benefit from nutritional intervention than those who are adequately nourished or at low risk of malnutrition [6]. On admission to hospital following a stroke, the focus should be on identifying those who are nutritionally vulnerable, i.e. malnourished or at medium/high risk of malnutrition. In clinical practice this can be accomplished by the routine use of nutrition screening tools. Nutrition screening using a validated tool has been recommended by a number of professional organisations in the USA and Europe, among them the American Society for Parenteral and Enteral Nutrition [38], the British Dietetic Association [39], the European Society for Parenteral and Enteral Nutrition [40], the British Association for Parenteral and Enteral Nutrition (BAPEN) [11], and the National Institute for Health and Clinical Excellence [7].
The role of a nutrition screening tool (NST) is to aid the identification of patients who are nutritionally vulnerable, i.e. currently malnourished or at risk of becoming malnourished, in order that they might be referred for further assessment and nutritional intervention if required [1]. NSTs are not designed to assess the nutritional status of patients, establish the severity of malnutrition, or identify the reasons for poor status; they simply indicate that a patient has actual or potential nutritional problems and requires further investigation. While providing a useful, structured aide memoire, NSTs support, but do not replace, clinical judgement. NSTs are usually completed by nursing staff or health-care assistants who are not nutrition specialists, and thus people identified as at medium or high risk of malnutrition during a screening procedure should be referred for a full nutritional assessment by a nutrition specialist such as a dietician. Similar to all screening tools, NSTs should be valid and reliable, and since they should be completed on all patients in a particular setting, they should be quick to administer, easy to use and to interpret, and acceptable to both patients and health-care professionals [41]. Examples of validated nutrition screening tools used in the UK and Europe include the Malnutrition Universal Screening Tool (MUST) [11], the Nutrition Risk Score-2002 (NRS-2002) [42], the Short Nutritional Assessment Questionnaire (SNAQ) [43], and the short-form Mini Nutritional Assessment (Short-form MNA) [44]. The majority of these screening tools require the measurement of height and weight to determine body mass index (BMI) and also require a record of recent weight change and/or change in dietary intake. People who eat almost nothing for 5 days lose about 5 % of their body weight, even in the absence of disease. Furthermore, minimal dietary intake for a few days in the presence of disease results in poor muscle function, increased risk of infection, and delayed wound healing, even in the absence of recorded weight loss [6]. Therefore, patients who are nil by mouth (or have minimal intake) for more than 5 days, e.g. due to dysphagia following a stroke, should be considered to be at nutritional risk, even if their nutritional status was adequate when they were admitted to hospital.
Recently, it was shown that a validated NST is a good predictor of poor outcome in patients who have had a stroke. In a study of 537 patients screened using MUST within 72 h of hospital admission for acute stroke, there was a strong positive correlation between risk of malnutrition and mortality rate which remained significant after adjustment for possible confounders [26]. At 6 months those patients who were at high risk of malnutrition on admission to hospital were twice as likely to die than those at low risk. Furthermore, for patients who survived there was a strong positive correlation between the risk of malnutrition and both length of hospital stay and hospitalisation costs, which again remained significant after adjustment for possible confounders [26]. Patients at high risk of malnutrition were likely to stay in hospital three times longer than those at low risk and cost nearly twice as much [26].
It is perhaps not surprising, therefore, that to aid the identification of at-risk and malnourished patients, the National Institute for Health and Clinical Excellence recommends that all patients should be screened routinely on admission to hospital and care homes, at regular intervals throughout their stay, during outpatient and GP visits, and on first contact with community care teams [7]. In England and in other countries, similar recommendations around the use of validated nutrition screening tools have been incorporated into recent guidelines for the management of acute stroke [45–47].
Assessment
Following nutrition screening, patients identified as malnourished or at medium/high risk of malnutrition should undergo a full nutritional assessment conducted by a health-care professional with specialist nutrition knowledge, usually a dietician [7]. Nutritional assessment establishes the nutritional status of an individual and explores the causes and duration of nutritional problems. The assessment forms the basis for determining treatment goals and the nature, mode, and duration of nutritional intervention.
A full nutritional assessment usually comprises five major components: anthropometry, i.e. measurements of weight, height, and body composition; a review of laboratory data; an assessment of clinical status; an assessment of dietary intake; and consideration of environmental factors. There are a number of validated nutrition assessment tools available, e.g. the Mini Nutritional Assessment (MNA) tool [22], Subjective Global Assessment (SGA) tool [23], and Patient-Generated SGA [48], all of which include at least some of the following components.
Anthropometry
Body weight is usually recorded routinely as part of the nutrition screening process and provides valuable information on both current and past nutritional status. While most clinicians will readily identify someone who is thin as either malnourished or at risk of malnutrition, individuals who are not thin may also be at risk of malnutrition, even if they look (or are) overweight or obese. Whereas low body mass index (BMI) reflects chronic malnutrition, recent weight loss reflects acute changes in nutritional status and suggests underlying physical or psychological illness or social issues. Regardless of BMI, unintentional weight loss greater than 10 % over 3–6 months, or more than 5 % in 1–3 months, is generally considered to be clinically significant because it is associated with loss of body function and poor clinical and functional outcomes [11].
In a recent study of 543 acute stroke patients, 109 (20 %) participants had unintentionally lost weight prior to hospital admission for a variety of reasons unrelated to their stroke, including gastrointestinal symptoms, excess alcohol intake, previous surgery, taste changes, loss of interest in food, and bereavement [49]. In this study those who had experienced pre-admission weight loss had a significantly higher risk of mortality and a significantly longer hospital stay at 6 months post-stroke, and cost significantly more (£8,416 versus £5,506 per patient) than those who had been weight stable prior to the stroke. Furthermore, those who had lost the most weight were at greatest risk of poor outcomes. A history of unintentional weight loss before admission should therefore send warning bells to any clinician who might be considering the nutritional needs of their patient, particularly if the patient has had a severe stroke and/or has dysphagia, and oral intake is likely to be compromised for more than a couple of days [7].
Since BMI provides useful information regarding nutritional status in both the malnourished and obese, the accurate measurement of height is an important component of a full nutritional assessment. Both in the outpatient and inpatient setting, health-care professionals have a role in ensuring that, wherever possible, all patients have their height measured and documented at least once in adulthood [7]. In those patients where height is not known, and where it cannot be measured safely due to mobility issues, surrogate measures for height such as ulna length [50], demi-span [51], or knee-height [52] can be used. All three of these techniques provide a reliable estimate of height, suitable for determining BMI, if undertaken by a trained practitioner.
During the first few days following a stroke, a small proportion of patients will be unsafe or unable to mobilise and it may not be possible to weigh them, either to obtain information for a weight history or to calculate BMI (although hoist scales should be available on most stroke units). In this case a measurement of mid-arm circumference (MAC) by a skilled practitioner may be used in the absence of weight to estimate BMI. Data collected from 1,561 hospitalised patients included in a nutrition intervention trial [53] suggest that those with a MAC less than 25.0 cm are likely to have a BMI less than 20 kg/m2 and those with a MAC less than 23.5 cm are likely to have a BMI less than 18.5 kg/m2 [53, 54].
Biochemistry
During a full nutritional assessment, laboratory data will be reviewed to help determine the patient’s hydration status, clinical condition, e.g. raised CRP, and low serum albumin levels indicating metabolic stress, and nutritional markers such as vitamin and trace element status. Some patients could be at risk of re-feeding syndrome [55, 56] if dietary intake has been poor for a prolonged period prior to (or during) hospital admission and phosphate, potassium, calcium, and magnesium levels should be reviewed prior to implementation of nutritional support in all patients with known re-feeding risk factors [7]. There are several published regimens for managing patients at risk of re-feeding syndrome. The lack of randomised controlled trials in this area, however, means that management is based on consensus and expert opinion rather than evidence [56]. Irrespective of which regimen is employed, the common principles are to prevent re-feeding syndrome by cautious re-introduction of energy and correction of biochemical abnormalities [7, 55]. It is likely that the problems associated with re-feeding are less likely to arise with oral nutritional support since illness is usually accompanied by a loss of appetite; however, care should be taken in the prescription of oral nutritional supplements in those at high risk of re-feeding syndrome [7].
Clinical
Quite apart from the direct impacts of a stroke, e.g. dysphagia, hemianopia, arm weakness, or neglect, patients who have had a stroke often present with a number of nutritionally relevant co-morbidities such as diabetes, hypertension, hyperlipidaemia, gastro-oesophageal reflux, or depression. All of these conditions will need to be taken into account when devising a nutrition action plan whether the patient is capable of consuming an oral diet or requires tube feeding.
Dietary
The onset of malnutrition is usually insidious, although in conditions of acute metabolic stress such as critical illness, nutritional depletion and weight loss can be very rapid and severe [6]. While there tends to be a focus on inadequate energy and protein intakes, it should be recognised that in people with a poor dietary intake, micronutrient intakes are also likely to be deficient [7]. It is also important to recognise that micronutrient intakes may be sub-optimal even in the presence of adequate macro-nutrient intakes, particularly if individuals follow a restricted diet or a diet of limited variety or poor quality [57].
Dietary assessment should take account not only current (i.e. inpatient) nutritional intake but also previous (prior to stroke) and likely future intakes (post-discharge). Dietary intake may be assessed in a number of different ways (and for varying lengths of time) depending on the nutrient or food of interest, the care setting, and the patient’s ability to provide valid and accurate information [58]. In the acute setting, dietary intake is usually estimated from data recorded by nursing staff on food record charts. Since food record charts are rarely fully or accurately completed [59], a dietician may also ask the patient (and/or their carer or nurse) to describe everything they have eaten and drunk in the previous 24 h (24-h recall method) [58]. In order to obtain information on a patient’s habitual intake, e.g. pre-admission, a diet history may be taken [58].
In patients who have had a stroke, dietary assessment aims to determine the patient’s actual and potential ability to meet their nutritional needs by normal texture diet via the oral route. In a significant proportion of patients, this will be unlikely (or unsafe) and alternative routes and methods of feeding will need to be considered. While it might be expected that patients who have had a stroke would have a poor dietary intake in hospital, very few studies exist that describe the nutritional intakes of hospitalised stroke patients. One study suggests that the energy intake of hospitalised stroke patients with adequate swallow is similar to that of other hospitalised patient groups, i.e. an average of 75 % of predicted energy requirements over 2 weeks [60]. One other study which examined energy and protein intakes following stroke reported that, on average, regardless of diet type (oral or non-oral) and texture (regular diet or texture modified because of swallowing impairment), hospitalised patients consumed an average of 85 % of their energy requirements, and 86 % of protein requirements, during the first 21 days following stroke [61]. While these deficits might appear relatively small, over time they are sufficient to result in weight loss and may have an adverse effect on outcome in malnourished or medium/high-risk patients. If not treated, this could have a profound impact on rehabilitation, functional recovery, and outcome, even in previously adequately nourished patients [6].
Environmental
This final part of the assessment aims to establish how well the patient functioned in their home environment with regard to food purchase, preparation, and cooking prior to admission. For example, was the patient coping alone, did they require practical help and support from family and friends, or were they in receipt of a package of care which included help with these activities? Since a stroke is likely to have an adverse impact on several aspects of a person’s physical, social, or psychological function, the dietician will need to assess whether or not the patient is going to be capable of undertaking these activities on discharge (or soon afterwards) and start to make appropriate arrangements prior to discharge. Together with the multi-disciplinary team, the dietician will assess the patient’s need for post-discharge support including intermediate care, sheltered housing, care home admission, home meal delivery, shopping, or befriending services.
Management
Observational studies have shown an association of reduced mortality after stroke with nutritional assessment [62] and adequate nutrition and hydration (with antiplatelet therapy if required) [63]; however, a recent systematic review seeking to evaluate the impact of nutritional supplementation versus no supplementation in non-dysphagic stroke patients showed little benefit from supplementation [64]. This review should, however, be interpreted with caution since, although eight RCTs were included (4,391 participants), all included studies except the FOOD trial [24] were small and of relatively short duration. The inclusion criteria for the review failed to examine both nutritional risk status at baseline and compliance with intervention, and included studies conducted in patients recruited at any time up to 6 months post-stroke. Furthermore, the included studies described a variety of different nutritional interventions (including one assessing antioxidant and ω-3 fatty acids and one that included some tube-fed patients) in a variety of stroke populations. It is impossible therefore to determine if the observed lack of effect was due to heterogeneity in the interventions and populations, the result of inadequate intake due to poor compliance, or to failure of the intervention per se.
The underlying causes of inadequate intake in patients who have had a stroke are multi-factorial and multi-disciplinary and may originate in any part of a health-care organisation from the strategic policy level down to the individual feeding of a patient. Therefore, in the management of malnutrition in the acute setting, it is necessary to take into account not only the patient-specific issues that might impact on nutritional status, e.g. nutrition risk status on admission, severity of stroke, or ability to swallow but also to consider the systems for food and drink provision as well as the ward environment and nutritional care procedures. As a result, some interventions may be targeted and tailored for individuals while others may be non-targeted and implemented at ward or unit level. The need for these latter interventions assumes that a significant proportion of the stroke unit population are nutritionally vulnerable, and prevention of nutritional deterioration is the key aim. Examples of such interventions include protected mealtimes, red trays, feeding assistance, food fortification, or altering the mealtime environment to encourage food and drink consumption [65].
Goals of Treatment
In patients who have had a stroke, the goals of nutritional treatment are likely to include one or more of the following:
Meeting all nutritional requirements (macro- and micronutrients and fluid) in patients who are nil by mouth
Meeting nutritional needs while minimising the risk of aspiration by provision of a texture-modified diet for patients with dysphagia
Nutritional support (supplementation) for patients who are not meeting their full nutritional requirements (for whatever reason)
Nutritional Requirements
One of the aims of devising a nutritional prescription is to provide a patient with their complete requirements either via a single route or any combination of oral, enteral, or parenteral nutrition, while avoiding the known complications associated with both under- and over-feeding [7]. The nutritional requirements of an individual following a stroke will depend on their nutritional status, clinical condition, physical activity level, nutritional goals, and likely duration of nutritional support [7]; however, the nutritional requirements of patients who have had a stroke have yet to be fully characterised. While evidence suggests there is a small, temporary increase (7–14 % above predicted resting energy expenditure) in metabolic rate post-ischaemic stroke [66, 67], there is conflicting evidence around the impact of haemorrhagic stroke on metabolic rate [68–70].
A recent review of the evidence around energy requirements in healthy and sick populations by the Scientific Advisory Committee in Nutrition [71] concluded that while acute illness may result in a temporary increase in basal metabolic rate, this is usually accompanied by a significant reduction in physical activity such that total energy expenditure is usually around the same, or a little less than, healthy populations of the same age and gender. In the absence of stroke-specific studies, an energy prescription of 20–30 kcal/kg body weight/day is likely to be adequate for the majority of patients, although those who are severely malnourished (at risk of re-feeding syndrome), or are acutely unwell, might need to commence feeding at lower levels, and specialist advice should be sought [7].
Together with the assessment of dietary intake (see above), estimated nutritional requirements will indicate if there are any nutritional deficits, e.g. low energy intake, sub-optimal micronutrient intake, inadequate fluid intake, that need to be taken into account when devising the nutritional prescription.
Feeding Route
Wherever possible, nutritional and fluid requirements should be met via the oral route [72, 73]. In those who are unable to meet all their nutritional needs via the oral route, tube feeding should be considered [7]. Parenteral nutrition to meet all, or a proportion, of nutritional needs in those patients with a non-functioning gastrointestinal tract who are unable or unsafe to meet their needs by any other route is very rarely used in patients who have had a stroke [7].
Nutritional Interventions
In the management of malnutrition, interventions targeted at individuals may comprise one, or any combination, of the following strategies:
1.
Dietary counselling where the patient and/or their carers are counselled to increase the frequency of food and/or fluid consumption and thus maximise energy and protein intake. Advice is tailored to a patient’s preferences and lifestyle, taking into account any clinical conditions such as diabetes, hyperlipidaemia, or renal insufficiency.
2.
Food fortification to increase the macro- and micronutrient density of food and/or drink, using energy and protein-rich ingredients such as milk powder, butter, and milk, or commercially available, prescribable powders and liquids, e.g. Pro-cal (Vitaflo, Liverpool, UK) or Duocal (Scientific Hospital Supplies, Liverpool, UK).
3.
The provision of prescribable oral nutritional supplements (ONS) (often known as sip feeds), e.g. Ensure (Abbott, Maidenhead, UK), Fortisip (Nutricia, Trowbridge, UK), or Resource (Novartis, Camberley, UK).
4.
Texture-modified diets to meet the nutritional needs of those patients who are unsafe to swallow food and drink of normal texture.
5.
Tube feeding to meet all, or a proportion, of nutritional needs in those patients with a functioning gastrointestinal tract who are unable or unsafe to meet their needs orally.
Dietary Counselling
The aim of dietary counselling is to improve the macro- and micronutrient intakes of individuals by providing patients and/or their carers with tailored advice and support, often accompanied by written information including suggested daily menus and recipe sheets. By tailoring advice to an individual’s nutritional requirements, preferences, symptoms, and lifestyle it may be possible to achieve good compliance. Furthermore, on cessation of intervention, dietary habits may have changed sufficiently to ensure maintenance of any weight gain and/or functional benefits. Advice may be provided on a variety of topics including food choice and preparation, altered meal patterns, snacks, and nourishing drinks and may include advice on how to manage specific symptoms (e.g. dry mouth, taste changes) or how to overcome anorexia or specific eating difficulties. The effectiveness of dietary counselling will depend on many factors, and in patients who have had a stroke, confusion, altered consciousness, or limited comprehension may make it difficult for some patients to comply with dietary advice in the acute setting. On discharge, people recovering from a stroke may have some difficulties with shopping and food preparation, and multi-disciplinary team input may be required to address these issues in discharge planning. To date there are no studies evaluating the impact of dietary counselling in patients who have had a stroke [73].
Food Fortification
The aim of food fortification is to increase the nutrient density of food and drink without increasing portion sizes. Thus, this strategy might be particularly useful in individuals with a poor appetite or early satiety, symptoms that frequently accompany acute illness. Food fortification advice can be provided for individuals and/or their carers but can also be implemented at ward or unit level for vulnerable populations. Studies that have measured the impact of providing energy-dense meals and snacks to hospitalised patients have reported increased energy and protein intakes [74–76], a significant increase in body weight [77], and a significantly shorter length of hospital stay in a subgroup of the intervention patients [78]. To date there are no studies that have investigated the impact of food fortification on other clinical outcomes or cost.
Oral Nutritional Supplements (ONS)
While the FOOD trial suggests there are no benefits in routine supplementation of stroke patients using ONS [24], there is evidence that ONS can be beneficial in terms of energy intake, weight gain, and functional status in other patient groups, in particular the elderly [78], if they are provided to those who are nutritionally at risk or malnourished [79]. Typically, ONS contain a mix of macro- and micronutrients and most provide around 300 kcal, 12 g protein, and a full range of vitamins and minerals per serving, although there is a wide range available. ONS are usually present in liquid form, but puddings and powders are also available. Like tube feeds, ONS are foods for special medical purposes (FSMPs), and as such their composition and labelling are regulated under the European Commission Directive 1999/21/EC. ONS can be prescribed in the community for the management of disease-related malnutrition (and a number of other indications) in accordance with the Advisory Committee on Borderline Substances (ACBS) guidelines. The cost of ONS in the community is, however, often a consideration, and recently there has been considerable emphasis on the use of care pathways to ensure their appropriate use, including the need for regular monitoring and follow-up [80].
Texture-Modified Diets
In patients with dysphagia, a texture-modified diet may be prescribed after a full swallow assessment, usually by a speech and language therapist. Several studies have reported that patients requiring thickened fluids are less likely to meet fluid requirements [81, 82] and that texture-modified diets are often nutritionally inadequate [83, 84]. Since people who are nil by mouth (or have minimal intake) for more than 5 days are considered nutritionally at risk, patients may require oral nutritional supplements and/or supplementary tube feeding in order to meet their nutritional requirements [7].
The aims of dysphagia management are as follows [81, 85]:
Minimise risk of malnutrition
Minimise risk of dehydration
Minimise risk of aspiration pneumonia
Maintain oral intake
It is considered good clinical practice to maximise the nutritional intake of patients on texture-modified diets, but currently there is a lack of evidence around how best to achieve this [7]. In clinical practice it appears difficult to achieve consistent supplementation of texture-modified food and drinks, in part due to organisational constraints, but also due to issues around achieving the correct texture when adding thickeners at ward level, and the observation that people on these diets tend not to consume very much and frequently fail to meet their nutritional and fluid requirements [81–84]. Currently, it is not possible to discriminate between the impact of the food’s unappetising appearance, diluted flavour, and altered texture; patient-specific factors such as poor appetite, impaired mobility, or depression; and organisational issues such as limitations on the provision of a choice of attractive meals of the correct texture.
Tube Feeding
In those with a functioning gastrointestinal tract, tube feeding should be considered not only for those who are nil by mouth due to unsafe swallow, but also for those who are unable to meet their nutritional needs by the oral route alone, especially if they are already malnourished [7]. It should be noted that even in stroke populations, dysphagia is not the only reason that people fail to meet their nutritional requirements by the oral route alone. In general, people should be fed via a tube into the stomach unless there is upper gastrointestinal dysfunction. Where there is evidence of upper gastrointestinal dysfunction, or an inaccessible upper gastrointestinal tract, post-pyloric (duodenal or jejunal) feeding should be considered. For people being fed into the stomach, bolus or continuous methods should be considered, taking into account patient preference, convenience, and drug administration [7]. Those requiring post-pyloric feeding should, however, receive continuous rather than bolus feeding [7]. People who are unable to swallow safely or take sufficient nutrition orally should have an initial 2- to 4-week trial of tube feeding, and those who require longer term support should be considered for gastrostomy feeding [7, 47].
For a full discussion of the role of tube feeding in the management of stroke please see below.
Mealtime Improvements and Optimising Nutritional Care
At any time on a stroke unit there is likely to be a high proportion of patients experiencing significant feeding difficulties, either as a result of their stroke or due to pre-existing malnutrition. In recognition of this, it would appear to be good clinical practice to ensure ward-based systems and procedures are implemented that maximise the dietary intake of all patients, rather than targeting only those who are already malnourished. A number of strategies have been recommended as good clinical practice (Table 7.2) by national and international organisations including BAPEN and the European Commission, and professional bodies including the Royal College of Nursing and the Royal College of Physicians, although currently there is a lack of good-quality evidence to support their use [65]. At ward level the provision of food and drink is considered a nursing responsibility; however, it could be argued that strategies that aim to improve the mealtime environment and the patient meal experience require support from clinicians and other health-care professionals at all levels if they are to be effective.
Table 7.2
Strategies to improve nutritional care at mealtimes and the mealtime environment
Strategy | |
|---|---|
Periods on a hospital ward or in a care home when all non-urgent clinical activity stops; people are made ready to eat and provided with a pleasant environment that encourages eating; provision of physical assistance with eating and drinking; verbal encouragement; observation and recording of meal completion | |
Red trays [88] | Patients requiring assistance with eating and drinking are identified, e.g. nutritional risk, confusion, poor vision; food is provided on a red tray to ensure those requiring assistance receive it |
Patients are assisted to eat and drink, including provision of adapted crockery and cutlery if required; opening of packets; food is placed where patient is able to reach it easily; food may be cut up; patients may be fed if required; verbal encouragement | |
Family-style meals; communal eating in a homey room; table dressing; menu choice; quiet and pleasant environment; lack of distractions |
Monitoring and Evaluation
The main objective of monitoring is to ensure nutritional support is provided safely and effectively. Monitoring also permits clinicians to assess the extent to which nutritional goals have been met and to detect and treat clinical complications as early and effectively as possible. Should any complications occur, or nutritional goals not be met, monitoring and evaluation will allow clinicians to alter the type of nutrition support, or amend the regimen, to improve its effectiveness or to minimise or prevent complications. To achieve these objectives, monitoring protocols should include a variety of observations and measurements (Table 7.3) [7].
Table 7.3
Nutritional, anthropometric, and clinical monitoring
Parameter | Frequency | Rationale |
|---|---|---|
Nutritional intake (from oral, enteral, or parenteral nutrition) | Daily initially, then twice weekly when stable | To ensure patient meets daily nutritional requirements |
Fluid balance | Daily initially, then twice weekly when stable | To ensure patient meets daily fluid requirements (not over- or under-hydrated) |
Weight | Weekly, then monthly (daily if there are concerns regarding fluid balance) | To monitor ongoing nutritional status and determine if nutritional goals have been met |
Mid-arm circumference and triceps skinfold thickness | Monthly (if weight cannot be obtained) | To monitor ongoing nutritional status and determine if nutritional goals have been met |
Gastrointestinal function, e.g. diarrhoea, constipation, abdominal bloating | Daily initially, then twice weekly | To ensure tolerance of feed and to determine potential causes of gastrointestinal dysfunction |
Clinical condition, e.g. temperature, blood pressure, consciousness, swallowing ability | Daily initially, then twice weekly when stable | To ensure that the feeding route, methods, and goals of nutritional treatment remain appropriate |
Drug therapy | Daily initially, then monthly when stable | To prevent/reduce drug nutrient interactions |
Laboratory data | Daily initially, then twice weekly when stable | To monitor clinical status, fluid status, and assess for re-feeding risk |
Psychological and social status | Daily initially, then twice weekly when stable | To determine potential impact on nutritional intake and/or status |
The type and frequency of monitoring will depend on the extent and severity of the stroke, the presence of any co-morbidities that might complicate nutritional management, e.g. diabetes, in patients receiving enteral tube feeding, whether previous results were abnormal, the type of nutrition support used, the setting of the nutritional care, and the expected duration of nutrition support.
While not currently recommended for use in routine clinical practice in hospitalised patients who have had a stroke, serial triceps skinfold thickness (TSF) measurements can be a useful way to measure changes in fat mass over time (weeks or months) in patients who are likely to be followed up in the long term, e.g. in outpatient clinic. Together with MAC (see previously), TSF measurements can be used to determine mid-arm muscle circumference (which provides an estimate of lean body mass), and thus regular measurements of both TSF and MAC over time can indicate changes in body composition, i.e. lean body mass and fat mass. In clinical practice, this can be useful if the aim is to measure the impact of nutritional intervention either alone or together with physical and/or other therapies, such as might occur during rehabilitation after stroke. Since both the measurements of MAC and TSF are prone to large inter- and intra-observer error, all such anthropometric measurements should be undertaken by the same skilled practitioner on each occasion [93]. Similarly, hand-grip strength can be used to measure the impact of nutritional interventions over time on skeletal muscle function [94].
Observational studies show that documentation regarding nutritional status, body weight, appetite, and food intake is generally poor [95–98], yet nutritional intervention cannot be managed safely or effectively without adequate standards of both monitoring and documentation [7]. This would seem particularly pertinent with the decreases in length of hospital stay observed in recent years. With average hospital stays as short as 4 or 5 days, it is perhaps unrealistic to expect that the full nutritional treatment plan will be implemented in time for the patient to be discharged. While it should be possible to ensure the patient undergoes nutrition screening and assessment while in hospital, the full treatment plan may not be fully implemented prior to discharge. In such cases, post-discharge monitoring and follow-up arrangements to ensure the patient’s nutritional status are evaluated effectively, and to measure the impact of nutritional intervention, are particularly necessary. However, evidence suggests that discharge documentation to GPs relating to nutrition is poor and that, as a result, only a small proportion of malnourished patients are followed up by a dietician [99]. The doctor’s role in communicating relevant nutritional information between hospital and community health-care professionals is pivotal in ensuring effective discharge planning and safe transfer of care with respect to nutrition. This will be accomplished usually in collaboration with a dietician and other members of the multi-disciplinary team such as speech and language therapists and physiotherapists.
Since eating and drinking can remain problematic for many months post-stroke, and stroke may result in changes in social and/or psychological status that might impact on dietary intake and/or nutritional status, patients should be screened for nutritional risk status whenever they attend outpatient clinics, including at 6- and 12-month reviews in stroke clinic, or when they come into contact with community-based health-care professionals [7]. All those identified as malnourished or at risk of malnutrition in the community should be referred for a full nutritional assessment and intervention if required [7, 80].
Overweight and Obesity
Epidemiology
Obesity, i.e. excess body weight, in particular excess fat mass, is associated with an increased risk of several conditions that may lead to stroke, including hypertension, hyperlipidaemia, and diabetes mellitus.
Since 1980 the prevalence of obesity has nearly doubled worldwide. In 2008, more than 1.4 billion adults (35 %) aged 20 years and older were overweight, and of these, over 500 million (11 %) were obese [3]. Overweight and obesity are the fifth leading risk for global deaths, and at least 2.8 million adults die each year as a result of being overweight or obese. In addition, 44 % of the diabetes burden, 23 % of the ischaemic heart disease burden, and between 7 and 41 % of certain cancer burdens are attributable to overweight and obesity [3]. By 2050 obesity is predicted to affect 60 % of adult men and 50 % of adult women in the UK, and the NHS costs attributable to overweight and obesity are projected to reach £9.7 billion, with wider costs to society estimated to reach £49.9 billion per year [100]. These factors combine to make the prevention of obesity a major public health challenge.
While it is recognised that overweight and obesity are associated with the incidence of first-ever stroke, it is still debatable whether or not this is an association with obesity alone or a reflection of the fact that overweight and obese individuals are more likely to have other conditions such as hypertension, diabetes, and hyperlipidaemias, that in themselves increase the risk of stroke and cardiovascular diseases. Most studies seem to show that obesity is a modifiable risk factor for ischaemic stroke, but that it is highly mediated through other risk factors, i.e. diabetes, hypertension, and hyperlipidaemia [101].
Aetiology
The fundamental cause of obesity and overweight is an imbalance between energy (calories) consumed and energy expended, i.e. more energy is consumed than the body burns. The excess energy is stored as adipose tissue.
The exact cause of obesity is not clear, and in any individual likely arises from a complex combination of factors. The Obesity Systems Map [102] was developed to provide an insight into the multiple factors contributing to the high prevalence of obesity in the UK. It shows a complex web of often reinforcing causal factors that range from genetic predisposition and individual psychology and physiology, through the culture and economics of food production, food consumption, and the built environment; to education on food and nutrition, and attitudes towards physical activity and lifestyle. It is not within the scope of this chapter to consider all of these factors, but it is worth noting that eating habits, physical activity, and psychological issues are considered modifiable, and therefore are most often targeted in weight-loss interventions.
Detection
Body mass index (BMI) is a simple index of weight for height that is commonly used to classify overweight and obesity in adults. It is defined as a person’s weight in kilograms divided by the square of their height in metres (kg/m2). BMI provides the most useful population-level measure of overweight and obesity, as it is the same for both sexes and for all ages of adults. It should be considered a rough guide however, since the same BMI may not correspond to the same degree of fatness or associated health risk in different individuals and populations. Acknowledging this, the World Health Organisation continues to recommend that using a standard definition allows for meaningful comparisons between individuals and populations and provides a firm basis for evaluating interventions [103].
Health-care professionals need to be aware, and inform their patients, that members of black, Asian, and other ethnic groups face an increased risk of chronic health conditions at a lower BMI than the white population (below BMI 25 kg/m2) [104]. This has been demonstrated mainly in relation to risk of type 2 diabetes, and more research is needed to find out if the increased risk at lower BMI in different ethnic groups holds for first-ever stroke and/or stroke recurrence. Table 7.4 shows the BMI thresholds for white European and other populations recommended by the World Health Organisation (WHO 2004) [104].
White European populations | Asian populations | Description |
|---|---|---|
<18.5 kg/m2 | <18.5 kg/m2 | Underweight |
18.5–24.9 kg/m2 | 18.5–23 kg/m2 | Increasing but acceptable risk |
25.0–29.9 kg/m2 | 23.0–27.5 kg/m2 | Increased risk |
≥30 kg/m2 | ≥27.5 kg/m2 | High risk |
More recently, it has become evident that the distribution of fat around the body is associated with different health risks. Abdominal obesity (also known as central adiposity) is associated with an increased risk of metabolic and cardiovascular diseases than an even or peripheral distribution of fat around the body [103]. Abdominal fat can vary dramatically within a narrow range of total body fat and BMI, which suggests the need for additional measures to assess the health risks associated with overweight and obesity [103]. Indeed, abdominal obesity has been shown to be a stronger risk factor for stroke than BMI [105, 106].
To detect central adiposity, it is possible to measure waist circumference [107], although there is considerable debate around the potential impact of measurement site on risk categorisation [108]. Waist circumference (WC), measured at the midpoint between the lower border of the rib cage and the iliac crest, is a convenient and simple method considered a good surrogate of visceral adiposity across a wide age range. It provides a measure of fat distribution that cannot be obtained by measuring BMI alone. Waist circumference is not recommended as a routine measure but may be used to give additional information on the risk of developing other long-term health problems [109]. It should be noted that the waist circumference cut-offs are different for the sexes and for different ethnic groups (Table 7.5) [110]. Since metabolic and cardiovascular risk plateaus at higher BMIs, there is no benefit to measuring waist circumference in those with a BMI greater than 35 kg/m2 [102].
Table 7.5
Waist circumference cut-offs for different ethnic groups
Population | Cut-offs | |
|---|---|---|
European | Males | ≥94 cm |
Females | ≥80 cm | |
South Asian, Chinese, Japanese | Males | ≥90 cm |
Females | ≥80 cm | |
South and Central American | Use south Asian recommendations until further data available | |
Sub-Saharan African | Use European recommendations until further data available | |
Eastern Mediterraneanand Middle East | Use European recommendations until further data available | |
To date there is a lack of evidence that weight reduction in overweight or obese individuals has an impact on the primary or secondary prevention of stroke [111]. However, being overweight or obese is associated with conditions that increase the risk of first-ever stroke, e.g. hypertension, diabetes, and hyperlipidaemia, and current guidelines therefore recommend that people who have had a stroke should be encouraged and supported to lose weight, at the same time as addressing other risk factors such as smoking, hypertension, diabetes, or physical inactivity [46, 47].
Assessment
Assessment should be focused on determining the degree of obesity, identification of risk factors for developing complications of obesity (cardiovascular disease and/or stroke), dietary intake, and contributing causes [109]. The degree of obesity can be established through measurements of weight and height to determine BMI, and the presence and extent of any central obesity may be established by a waist circumference measurement. Identification of other cardiovascular risk factors may be determined by blood pressure measurements [112] and through the biochemical assessment of blood glucose and a lipid profile. Other tests may be considered if appropriate, e.g. liver function tests or thyroid function tests.
Any medical conditions and co-morbidities that could increase the risk of developing complications of obesity should be discussed, e.g. family history of stroke and vascular disease, medical problems, medication, as should any psychological factors that might impact on, or be impacted by, obesity. An assessment of current dietary and alcohol intake should be made and should include an exploration of the patient’s knowledge about diet, and any previous dietary changes they have made in an attempt to lose weight or decrease alcohol intake. The assessment should also include identification of any environmental factors, e.g. social issues, smoking, physical activity, and exercise, that might impact on the risk of developing complications of obesity [109].
Management
The level of intervention should be determined based on the degree of obesity, waist circumference, and the presence of relevant co-morbidities and risk factors [109, 113]. Interventions should be escalated from general advice on healthy weight and lifestyle, through diet and physical activity tailored to the individual (often in combination with psychological interventions), to consideration of drug therapy or surgery [109].
In the face of many misleading articles in the lay media, it is important to set realistic targets for weight loss at the outset and to manage expectations. People should be made aware of national sources of accurate information and advice, such as NHS Choices and Change4life, and should be advised to lose a maximum of 0.5–1.0 kg per week [109]. Guidelines [109, 113] recommend that people should be advised to avoid “yo-yo” dieting (otherwise known as weight cycling), in which weight is repeatedly lost and regained over weeks, months, or years, since in some studies this has been shown to increase a person’s likelihood of developing fatal health problems more than if the weight had been lost gradually or not lost at all. More recent evidence however, suggests the impact of “yo-yo” dieting on morbidity and mortality is not consistent [114].
People should be made aware that the more weight they lose, the greater the health benefits, particularly if they lose more than 5 % of their body weight and maintain this for life [109, 113]. Furthermore, people should be reassured that even preventing future weight gain can lead to health benefits [109, 113]. Clinicians should acknowledge the effort required to lose weight, prevent weight regain, or avoid any further weight gain, and to maximise the chance of achieving weight loss, should take into account the person’s feelings about being overweight or obese, and their willingness and motivation to try to lose weight [109, 113].
Lifestyle Modification Programmes
Multi-component interventions are the treatment of choice [109], since dietary interventions are more likely to be successful in terms of reducing morbidity if they form one component of a lifestyle modification programme [109, 113].
Lifestyle modification programmes usually address dietary intake, physical activity, and behaviour change, and include input from a dietician, a physiotherapist, or qualified physical activity instructor and a psychologist. The focus of such programmes is on life-long lifestyle change and the prevention of future weight gain. Such programmes usually last at least 3 months, and sessions are offered at least weekly or fortnightly and include a “weigh-in” at each session. People attending lifestyle weight management programmes lose on average around 3 % of their body weight, but this varies considerably [109].
Dietary Intake
To date there appears to be no evidence to suggest that advice on losing weight while still in hospital following an acute stroke confers any benefits on overweight or obese individuals. The need to lose weight, however, is frequently addressed in outpatient clinics soon after hospital discharge following acute stroke.
The main requirement of a dietary approach to weight loss is that total energy intake should be less than energy expenditure. Dietary changes should be individualised, tailored to food preferences and lifestyle, and should allow for flexible approaches to reducing energy intake [109]. Diets that contain 600 kcal less per day than the person needs to stay the same weight are recommended for sustainable weight loss [115]. While low-calorie diets (1,000–1,600 kcal/day) may also be considered, they are less likely to be nutritionally complete [116]. Very low-calorie diets (less than 1,000 kcal/day) may be considered for a maximum of 12 weeks continuously, or intermittently with a low-calorie diet (for example for 2–4 days a week), by people who are obese and have reached a plateau in weight loss [109]. Guidelines recommend that diets of less than 600 kcal/day should be used only under clinical supervision when there is an urgent need for weight loss [109, 113].
People are more likely to maintain a healthy weight if they reduce their consumption of energy-dense diets containing fatty and/or sugary food and drinks and follow a lower energy, high-fibre diet; consuming fewer take-away meals; eating more fruit, vegetables, and whole grains; minimising alcohol intake; and consuming less confectionery and fewer sugary drinks [117]. While there is considerable debate around which macronutrients (fat or carbohydrate) are most likely to result in excess weight gain, a recent large RCT with follow-up to 2 years concluded that reduced energy diets result in clinically meaningful weight loss regardless of which macronutrients they emphasise [118].
People should be advised to avoid concentrating on reducing the intake of one or two foods, or one particular food group, e.g. fat or sugar, since this strategy is less likely to be successful in the long term than aiming to eat a well-balanced, varied diet including all food groups in the correct proportions [109, 113].
Different types of diets have been attempted in the prevention of cardiovascular disease and, to a lesser extent, stroke, e.g. Mediterranean diet, lipid-lowering diets, low-salt diets for hypertension. These diets were designed to alter macro- and micronutrient profiles to reduce risk factors and were not necessarily designed for weight loss. However, in controlling the intake of macronutrients, weight loss often accompanies any changes in risk factors such as reduced blood pressure and altered blood lipid profile [119].
Some people may prefer a commercial weight-loss programme such as Weight Watchers, although the effectiveness of these programmes is difficult to assess, since they vary widely in content, presentation, timing, and venues. Furthermore, drop-out rates can be very high [120]. However, programmes that emphasise realistic goals, gradual progress, sensible eating, and exercise can be very effective for some people [109, 113].
Physical Activity
There is consistent evidence that interventions combining diet and physical activity are more effective for weight loss than diet alone [109, 113]. People who have had a stroke should be encouraged to increase their physical activity as much as is safely possible, even if they do not lose weight as a result, because of the other health benefits physical activity can bring, such as reduced risk of type 2 diabetes and cardiovascular disease.
Recent guidelines [121] recommend that adults should be encouraged to do at least 30 min of moderate-intensity physical activity on 5 or more days a week. The activity can be in one session or several lasting 10 min or more. Moderate-intensity activity usually increases a person’s breathing rate and heart rate and makes them feel warm, and includes activities such as brisk walking, cycling, gardening, house cleaning, golf, and racquet sports.
To prevent obesity, most people should be advised they may need to do 45–60 min of moderate-intensity activity a day, particularly if they do not reduce their energy intake [121]. People who have been obese and have lost weight should be advised they may need to do 60–90 min of physical activity a day to avoid regaining weight [121].
Adults should be encouraged to build up to the recommended levels of physical activity for weight maintenance, using a managed approach with agreed goals. Any activity should take into account the person’s current physical fitness and ability. While guidelines recommend that people should be encouraged to reduce the amount of time they spend in sedentary activities such as watching television or using a computer [109, 113], and should be supported and encouraged to try other activities that may be locally available, e.g. community walking groups, gardening schemes, or dog walking, there is currently a lack of evidence to support this strategy.
Behavioural Interventions
Evidence suggests the combination of behavioural interventions with diet and exercise results in an even greater weight reduction than either intervention alone, and thus weight management programmes should include behaviour change strategies to increase people’s physical activity levels or decrease inactivity and improve eating behaviour with regard to the quality of the person’s diet and energy intake [109].
Behaviour therapy usually focuses on what and how much a person eats and may involve asking the patient to keep a food diary to help them better understand the nutritional content of foods. It may also involve changing grocery-shopping habits, timing of meals, or advising the person to slow down the rate at which they eat. The behaviour programme may also explore how a person responds to food, in an attempt to understand what psychological issues may underlie a person’s eating habits. For example, one person may binge eat when under stress, while another may use food as a reward. In recognising these psychological triggers, an individual can develop alternative coping mechanisms that do not focus on food. Involving family members (usually spouse/partner) in behavioural treatment programmes is generally more effective for weight loss than targeting the overweight individual alone [109].
Pharmacological Interventions
Drug treatment should be considered only after dietary, exercise, and behavioural approaches have been attempted and have failed to achieve the desired weight loss, or for those people who have reached a plateau on these interventions [109]. Currently, only one drug is specifically licensed for use in the treatment of obesity in the UK (Orlistat, Roche, Switzerland). A meta-analysis of 15 RCTs found that this drug, in combination with a weight-reducing diet, was more effective for weight loss maintenance than placebo and diet at 12 months. At the same time, use of Orlistat was associated with small decreases in total cholesterol, %Hb1Ac and both systolic and diastolic blood pressure [109]. Since Orlistat reduces the absorption of energy-dense fat by inhibiting pancreatic and gastric lipases, it is associated with increased rates of gastrointestinal symptoms that are usually mild and transient.
When drug treatment is prescribed, arrangements should be made for appropriate health-care professionals to offer information, support, and counselling on additional diet, physical activity, and behavioural strategies, and information on patient support programmes should also be provided [109]. Regular review is recommended to monitor the effect of drug treatment and to reinforce lifestyle advice and adherence.
If there is concern about the adequacy of micronutrient intake, a supplement providing the reference nutrient intake for all vitamins and minerals should be considered, particularly for vulnerable groups such as older people (who may be at risk of malnutrition) [109].
Surgical Interventions
Overall mortality is 29–40 % lower in the 7–10 years after surgery in patients receiving bariatric surgery compared with BMI-matched subjects not receiving surgery [122]. Bariatric surgery is therefore recommended as a treatment option for people with obesity if all of the following criteria are fulfilled [109]:
BMI ≥40 kg/m2, or 35–40 kg/m2 in the presence of other significant disease that have the potential to be improved by weight loss, e.g. type 2 diabetes or high blood pressure.
All appropriate non-surgical measures have been tried but have failed to achieve or maintain adequate, clinically beneficial weight loss for at least 6 months.
The person has been receiving or will receive intensive management in a specialist obesity service and the person recognises the need for long-term follow-up.
The person is generally fit for anaesthesia and surgery.
Regular, specialist postoperative dietetic monitoring is recommended [109], and should include information on the appropriate diet for the bariatric procedure; monitoring of the person’s micronutrient status; and individualised nutritional supplementation, support, and guidance to achieve long-term weight loss and weight maintenance. Patients may also benefit from information on national or local patient support groups.
Monitoring and Evaluation
Weight loss is very difficult to achieve in the long term, therefore most patients will require medium- to long-term monitoring, encouragement, and support [123, 124]. Monitoring should include records of weight change and changes in waist circumference [109, 113] and may include measurements of changes in body composition, e.g. fat mass and lean body mass, although current national guidelines do not recommend routine use of bioelectrical impedance analysis to achieve this [109]. An increase in physical activity level together with changes in diet will make it easier for people to alter their body composition in a positive way, i.e. increase lean body mass and decrease fat mass.
Perhaps more importantly, clinicians should monitor the impact of multi-component interventions on changes in risk factors such as hypertension (may respond to dietary salt reduction), blood lipid profile (may respond to changes in diet although people are more likely to receive statins), and blood glucose (will respond to changes in diet).
Changes in dietary intake can be assessed using a variety of methods, including 24-h dietary recall, 5-day dietary diary, or weighed food intakes [58], although it should be recognised that each method has its strengths and weaknesses and requires specialist training in order to obtain an accurate assessment of intake. Clinicians should also remember that people who are overweight or obese are those who are most likely to under-report dietary intake, particularly the energy and fat components of the diet, as well as other nutrients they perceive to be “bad” [125].
The Obesity “Paradox”
In stroke populations it has been shown that those with low BMI (<20 kg/m2) are more likely to suffer poor outcomes than those with a higher BMI, and indeed those who are overweight or obese have even better outcomes than those in the desirable range for BMI [126–129]. This paradoxical association between BMI and mortality after stroke is most effectively demonstrated in a large cohort study in Denmark using data collected as part of a national stroke registry [126]. In this study of 13,242 individuals, mortality was higher in underweight patients (i.e. BMI <20 kg/m2) compared with those who were in the healthy range BMI (i.e. 20–25 kg/m2), overweight (BMI 25–30 kg/m2), obese (BMI 30–35 kg/m2), or severely obese (BMI >35 kg/m2) [126]. More recently, a prospective study of 543 patients designed to examine the impact of BMI on outcomes post-stroke showed that those with BMI less than 18.5 kg/m2 (underweight) were more than twice as likely to die at 6 months than those who were overweight or obese [129]. In this study it was also shown that there were no significant differences in stroke recurrence rates between BMI categories at 6 months post-stroke (BMI <18.5 kg/m2 = 3.7 %; healthy BMI = 3.8 %; overweight = 4.5 %; obese = 2.8 %; p = 0.91).
This better survival of overweight and/or obese patients (and increased mortality of underweight patients), observed in both ischaemic and haemorrhagic strokes, suggests that weight management strategies targeting the optimal BMI range used for the healthy population may require further evaluation and individualisation in the secondary prevention of strokes. In the future, it would be important to evaluate other indicators of nutritional status and distribution of body fat, such as waist circumference, in order to explore this paradox and its effect on stroke recurrence and mortality.
Dysphagia
Swallowing
The process of swallowing has been described as the most complex of “all or non-reflex” [130, 131]; however, although the pharyngeal swallow is a basic reflex, feedback regarding bolus size and viscosity emanating from afferents in the mouth and pharynx [132] regarding bolus size and viscosity via the cortex will modify timings of various components of the swallow.
A normal swallow is difficult to define, but essentially it is a series of sequential coordinated events that ensures a safe passage of food or liquid from the mouth to the stomach [133]. As food is brought from the plate or cup towards the mouth, preparation to swallow begins.
There are essentially three functions to the oro-pharyngeal swallow. These are bolus preparation, airway protection (trachea and nasal), and bolus passage through the pharynx to the oesophagus; and three swallowing phases: oral, pharyngeal, and oesophageal (relaxation of the upper oesophageal sphincter). The relationship between these phases of timing and duration is dependent to some degree on bolus characteristics.
Bolus Preparation/Oral Phase
The oral phase of swallowing is under volitional control, in that it is personal choice how long food is chewed before the bolus is gathered together and transferred to the back of the mouth; this will be influenced by bolus viscosity, texture, volume, and personal preference [134, 135].
As the bolus approaches the lips, the hyoid bone moves forward and up pulling the larynx up against the base of the tongue [136, 137]. Once the bolus has been placed in the oral cavity, lips are closed; the bolus is prepared for swallowing, by chewing and mixing with saliva in the case of a solid bolus (e.g. meat). When ready, the bolus is collected on the tongue and trapped between the tongue and the hard palate, such that in the antero-posterior view it is said to resemble a Viking long boat. The bolus is then propelled backwards to the pharynx by a rippling movement of the tongue from anterior to posterior.
Passage Through the Pharynx
Passage of the bolus through the pharynx is not straightforward. Once the bolus has left the back of the tongue, it moves momentarily into the valleculae, before passing over or around the epiglottis [138, 139]. The bolus then divides and passes through the lateral food channels (pyriform sinus), before reforming to pass through the upper oesophageal sphincter (cricopharyngeus), which is relaxed and opened.
Airway Protection
The pharynx is an anatomical structure/“tube” that is shared by both respiration and swallowing. To swallow safely, there needs to be an interruption to the respiratory cycle [142, 143]. As a consequence, during swallowing there is a period of apnoea, followed by expiration, but this is not invariable and certainly after sequential swallowing, inhalation may occur [139]. Where apnoea is not possible, e.g. lung fibrosis, COPD, or heart failure, swallowing may be a problem, resulting in dysphagia.
Protection of the airway commences at the beginning of the swallow, with upward and forward laryngeal movement. Concurrently the false vocal cords begin to come together, followed closely by the true vocal cords and then the epiglottis. The real protection of the airway is not the epiglottis but the vocal cords. It is possible to swallow without the presence of an epiglottis [144] and in sequential swallows the epiglottis is frequently upright [139].
As the bolus moves to the back of the oral cavity, the soft palate elevates to close off the nasal passages, aided by the forward movement of the posterior pharyngeal wall (Passavant’s cushion) [133].
Commencement of the Pharyngeal Swallow
Original research had suggested that the pharyngeal swallow would commence once a bolus passed the base of the anterior faucial arches. Subsequent research has found that this is true in some cases, but for many others the swallow does not trigger until the bolus is in the pharynx itself [145, 146].
Neural Control of Swallowing
The pharyngeal swallow is triggered by the presence of the bolus in the pharynx. The exact point at which the swallow triggers is different in each person. Information regarding the bolus presence is referred to as the brainstem and cortex [147, 148] and a swallow is triggered. However, there is not one interneuron but a system of connections within the reticular formation of the medulla, near the inferior olive, which has an important role to play. At the same time, information regarding the bolus characteristics are conveyed via afferents (within cranial nerves V, VII, IX, X–XII) to the cortex, which then modulates the swallow to regulate how long the upper oesophageal sphincter remains open, the dimensions of the pharynx, and the control of respiration and airway closure [148].
Cortical control is complex and is detailed elsewhere [149], suffice to say that there is no single cortical or subcortical region that has ultimate control. The swallow is bilaterally, but asymmetrically, represented [150] within the cortex (motor cortex, supplementary motor cortex, amygdala, frontal cortex, and cerebellum). Two areas that appear to be critical for the coordination of swallowing are the nigrostriatal pathway and the anterior insula cortex. Within these areas are numerous neuro-transmitters including substance P, dopamine, and noradrenalin (see Fig. 7.1) [151, 152].
