Respiratory management in neurological rehabilitation

Chapter 15 Respiratory management in neurological rehabilitation





Introducton


Respiratory problems are not confined to respiratory patients. Every patient has the potential to develop respiratory dysfunction. This is particularly true for patients with neurological disorders. As well as problems with reduced central drive or neuromuscular weakness associated with pathology and trauma, many neurological patients are susceptible to respiratory infections through immobility or aspiration (see Table 15.1). As respiratory dysfunction can be life-threatening, it makes sense for every physiotherapist to be competent to conduct an assessment of the respiratory system, to be aware of the common problems with which patients present, and to have a basic toolkit of interventions designed to manage such problems. This chapter will cover the areas of respiratory assessment, problem recognition and respiratory physiotherapy management in neurological patients.


Table 15.1 Clinical course for some neurological conditions commonly associated with respiratory problems



























































Disorder Clinical Course Prevalence of Respiratory Involvement
CNS
Multiple sclerosis Relapsing Pulmonary function impaired in 63%; respiratory failure or infection causes death in 5%
Parkinson’s disease Slowly progressive Pneumonia accounts for 20% of deaths, possibly from bulbar or upper airway muscle involvement and impaired cough
Spinal cord
Trauma Permanent High lesions (C1–3) usually require long-term ventilation
Motor neurone
Postpolio syndrome Very slowly progressive Respiratory impairment usually only in those with initial respiratory muscle involvement
Motor neurone disease Progressive Death almost uniformly due to respiratory complications
Motor nerves
Guillain-Barré syndrome Slowly reversible Respiratory failure in 28%
Charcot–Marie–Tooth Very slowly progressive 96–100% have prolonged phrenic nerve conduction; 30% have vital capacity <80% predicted
Neuromuscular junction
Myasthenia gravis Reversible Aspiration pneumonia gives rise to crises with 6% mortality
Botulism Slowly reversible 8% mortality due to respiratory failure
Muscle
Duchenne muscular dystrophy Progressive Respiratory failure is major cause of death

(Adapted from Aboussouan 2005, with permission.)



Respiratory assessment


A comprehensive respiratory assessment as outlined in Box 15.1 is only possible in a patient in a stable situation. If any ‘red flags’ are noticed (see Box 15.2), the assessment may need to be adapted and shortened. Although it is generally recognized that neurological disease may result in respiratory dysfunction, its presentation in such patients may be atypical, because of wider effects of the underlying condition (Polkey et al., 1999). The tests starred (*) in Box 15.1 will now be described further in relation to neurological patients.







Vital capacity


Vital capacity (VC) is the volume change at the mouth between full inspiration and complete expiration (see Figure 15.1). VC can be measured using conventional spirometers or recorded from equipment used to measure static lung volumes and their subdivisions. Guidelines for measurement have been published by the American Thoracic Society/European Respiratory Society task force (Wanger et al., 2005).



Ideally, the VC manoeuvre is performed with the patient using a mouthpiece and wearing a nose clip. In patients with neuromuscular weakness, assistance may be required to provide a seal around the mouthpiece, or a facemask may be substituted. It is important that patients understand they must completely fill and empty their lungs. The largest value from at least three acceptable manoeuvres (with a rest of ≥1 minute between manoeuvres) is used.


Normal values are calculated from the patient’s age, height and gender. A normal VC, with no significant fall when supine, means that respiratory muscle weakness is unlikely. However, muscle weakness in conditions such as myasthenia gravis can fluctuate significantly. Generally, it is only when muscle force is reduced to less than 50% of predicted that a decrease in VC can be observed. A fall in VC by more than 15–20% when the patient lies supine specifically suggests weakness of the diaphragm.


In acute neuromuscular disorders the VC and oxygen saturation should be rechecked at frequent intervals. A VC <1 L in an adult (<15 mL/kg), a fall in VC by more than 50% on serial testing, or onset of bulbar palsy are all indications to involve the intensive care unit (Hutchinson & White, 2008). In chronic neuromuscular disorders, monitoring can be less frequent, but a serial fall in VC (particularly a fall below 1.2–1.5 L or <40–50% of predicted) indicates a need for further respiratory assessment (Hutchinson & Whyte, 2008).



Peak cough flow


A normal cough requires the ability to generate sufficient inspiratory and expiratory power and a functional glottis.Ability to cough effectively is therefore compromised by either inspiratory or expiratory muscle weakness. However, expiratory muscle weakness has greater impact as mild to moderate expiratory muscle weakness can result in a weak cough, even if inspiration is normal (Boitano, 2006). In some neurological disorders, such as bulbar type motor neurone disease (MND; see Ch. 8), a functional glottis may be absent. Formal cough assessment requires the insertion of gastric balloons and is conducted in specialized laboratories, but cough strength can be assessed at the bedside using peak cough flow (PCF). PCF is a measure of maximal airflow generated during a cough manoeuvre. It provides a global indicator of cough strength that correlates well with the ability to clear secretions.


The recent joint guidelines from the British Thoracic Society (BTS) and Association of Chartered Physiotherapists in Respiratory Care for respiratory physiotherapy (Bott et al., 2009), include a guide for recording PCF in patients with neuromuscular weakness. It can be measured through either a mouthpiece or face mask attached to a peak flow meter and expressed in litres/minute or litres/second. The patient should be instructed to breathe in as deeply as possible and cough hard into the device. PCF is expected to be higher than peak expiratory flow, but in patients with bulbar dysfunction, this difference is not seen – potentially offering a way to monitor the onset of bulbar involvement (Boitano, 2006).


PCF is dependent on effort and lung volume, with cooperation being essential. The largest value from at least three acceptable attempts is usually recorded. Normal PCF is around 360 to 840 L/minute (Hutchinson & Whyte, 2008). Airway clearance becomes impaired and the risk of serious infection increases when PCF<160 L/minute, so in chronic progressive conditions, airway clearance techniques should be taught before these levels are approached (Tzeng & Bach, 2000). It has been suggested that any neuromuscular patients with a PCF<270 L/minute should be considered at risk of respiratory complications.



Inspiratory/expiratory pressures


Guidelines for testing the respiratory muscles have been published by the American Thoracic Society (2002). Inspiratory and expiratory pressures are recorded to assess respiratory muscle strength, but should be viewed as indices of global respiratory muscle output rather than as direct measures of their contractile properties (ATS, 2002). Mouth and nasal pressures can be recorded at the bedside using hand-held pressure meters. These volitional bedside tests are simple, portable and inexpensive; but their accuracy and reliability has been questioned because of their dependence on maximal effort and their significant learning effect. Non-volitional tests such as phrenic nerve stimulation are more reliable, but are expensive and confined to specialist centres.


Measurement of the maximum static inspiratory pressure generated at the mouth (PImax), or the maximum static expiratory pressure (PEmax), are the classic volitional tests of respiratory muscle strength. PImax can be more sensitive to respiratory muscle weakness than VC, because decreases in respiratory muscle strength occur before decreases in lung volume can be identified.


Patients are normally seated and noseclips are not required. Careful instruction and encouraged motivation are essential. Measurements require maximal inspiratory or expiratory efforts against a quasi occlusion. The pressure must be maintained for at least 1.5 seconds, so that the maximum pressure sustained for 1 second can be recorded. The maximum value of three manoeuvres that vary by less than 20% is usually recorded, but some authors have recommended that more measures are needed to reach a true maximum, and even low variability between measures may not guarantee that maximal efforts have been made (Aldrich & Spiro, 1995). Although simple in principle, the manoeuvres are difficult for many patients and require a good seal around the mouthpiece. Low values may therefore be due to true muscle weakness, or a submaximal effort, or air leaks, e.g. in the case of facial muscle weakness. The sniff is an alternative manoeuvre that is more natural and easier for most patients (see section on Sniff test).


The normal ranges for PImax and PEmax are wide, so that values in the lower quarter of the normal range are compatible both with normal strength and with mild or moderate weakness. In adults a PImax of more than 80 cmH2O in males, or 70 cmH2O in females, excludes clinically significant respiratory muscle weakness (Hutchinson & Whyte, 2008).



Sniff test


A sniff is a short, sharp voluntary inspiratory manoeuvre involving contraction of the diaphragm and other inspiratory muscles. Sniff nasal inspiratory pressure (SNIP) has been proposed as a volitional, non-invasive measure of inspiratory muscle strength. Peak nasal pressure is measured in one occluded nostril during a maximal sniff, performed from relaxed end-expiration through the other open nostril. Portable commercial systems are available for measuring SNIP at the bedside. Patients should be encouraged to make maximal efforts, with a rest between sniffs. Most patients achieve a plateau within 5–10 attempts. A sniff test is not suitable in patients with nasal congestion, which leads to falsely low values (Fitting, 2006). The sniff is easily performed by most patients, requires little practice and is relatively reproducible. It is therefore a useful voluntary test for evaluating diaphragm strength in the clinical setting, giving equal or greater pressures than PImax. However, SNIP and PImax are not interchangeable and should be considered as complementing one another for the assessment of inspiratory muscle strength.


There are reference values for SNIP in adults (Uldry & Fitting, 1995) and children (Rafferty et al., 2000). Surprisingly, SNIP is similar in children and adults, despite a large difference in respiratory muscle mass. Values of maximal SNIP greater than 70 cmH2O (males) or 60 cmH2O (females) are unlikely to be associated with significant inspiratory muscle weakness (Hutchinson & Whyte, 2008). The SNIP test appears particularly suited to neuromuscular weakness because it obviates the use of a mouthpiece and because it is easily mastered by most patients. However, assessment of severe muscle weakness should not rely on SNIP alone, but should include other tests such as PImax, vital capacity, nocturnal oximetry or ABGs (Fitting, 2006).

< div class='tao-gold-member'>

Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Jul 2, 2016 | Posted by in NEUROLOGY | Comments Off on Respiratory management in neurological rehabilitation

Full access? Get Clinical Tree

Get Clinical Tree app for offline access