Adjunct
Liters per minute (LPM)
FiO2 provided
Nasal cannula
Up to 6
Up to 50%
Simple face mask
Up to 10
Up to 60%
Venturi mask
Up to 12
Up to 60%
Non-rebreather mask
Up to 15
Up to 95%
High-flow nasal cannula
Up to 60
Up to 100%
It is suggested that this adjunct can provide positive end expiratory pressure (PEEP) of up to 7.4 cm H2O, but this is dependent on a closed system; an open mouth diminishes effective PEEP is diminished.
If all adjuncts have been exhausted, noninvasive positive pressure ventilation (NIPPV) can be the last attempt to adequately ventilate a patient prior to making the decision to intubate. This modality maintains positive pressure by using a tight-fitting mask over the nose and mouth, creating a closed circuit with effective PEEP. The continuous positive airway pressure (CPAP) mode of provides positive pressure throughout the respiratory cycle, while bilevel positive airway pressure (BiPAP) provides two levels of positive pressure, the higher giving assistance in inspirations and the lower preventing airway closure. Pressures run from 5 to 20 cm H2O. An important caveat to this adjunct is that the patient must have an adequate mental status as well as a gag reflex in order to avoid aspiration or mechanically pushing air into the stomach. The presence of copious secretions should be an exclusion to the use of NIPPV. BiPAP is preferred over CPAP in patients who develop pulmonary edema or hypercapnic respiratory failure (especially in patients with underlying COPD). NIPPV can also be used to treat nocturnal hypoventilation in patients with neuromuscular disorders.
End-tidal CO2 is a very useful adjunct in all phases of airway management. A simple probe inserted into the airway circuit in an intubated or non-intubated patients will provide a real-time CO2 level along with a waveform that provides useful information. Interpretation of CO2 level interpretation and waveform analysis provide important information such as ventilator status, cardiac output, apnea, and airway obstruction. This adjunct provides important information for the neurocritically ill patient, in light of the acute sensitivity of the brain to CO2 levels.
21.3 Decision to Intubate
Is the patient oxygenating adequately? If, after all adjuncts are employed, oxygenation is still not adequate, intubation may be indicated. Is the patient ventilating adequately? If pCO2 is elevated, this may be due to a central or metabolic cause and intubation with closed circuit mechanical ventilation may be required. In the neurologic patient, CO2 parameters are important, as they can affect cerebrovascular tone and ICP. If pCO2 is low, this may be due to hyperventilation from pain, toxins, or a central neurogenic cause. If it is not possible to mitigate the cause of hyperventilation with analgesia or sedation without compromising respiratory drive, endotracheal intubation with the assistance of medications (analgesic, sedating, or paralytic) may be needed in order to maintain adequate pCO2.
Is the patient able to protect his/her airway? Many critically ill neurologic patients can maintain airway patency and protection from aspiration in spite of neurologic deficits. This is a judgment call; if the patient has a diminished gag reflex, or otherwise is unable to protect his/her airway due to a diminished GCS or global neurologic obtundation, it may be appropriate to endotracheally intubate and mechanically ventilate. If this is a temporary situation that is likely to resolve as the patient recovers, extubation may be anticipated. However, if this is a permanent condition, early tracheostomy should be considered.
Does the patient have adequate inspiratory effort? Some neurologic illnesses, such as Guillain-Barre syndrome or Myasthenia Gravis, are associated with diminished inspiratory effort, resulting in inadequate tidal volumes and/or negative inspiratory flow. This patient will require endotracheal intubation if parameters of inspiratory effort and tidal volume are not met, and depending on the severity of the disease, may require prolonged mechanical ventilation and tracheostomy.
In general, prolonged endotracheal intubation increases the risk of subglottic stenosis and oropharyngeal erosion. Tracheostomy, which is typically more comfortable for the patient, should be considered after roughly 2 weeks of orotracheal intubation. This provides easier access to suctioning and the ability to easily remove and replace mechanical ventilation by simply removing or replacing the ventilator tubing without needing to intubate with laryngoscopy.
21.4 Intubation
The intubation procedure consists of preparation, execution, and post-intubation assessment and care. Preparation is quite possibly the most important part of the procedure, as excellent preparation will provide ample reserve and easily accessible backup, while poor preparation may lead to an emergency situation with poor decision-making.
21.4.1 Preoxygenation
Every intubation should be preceded by at least 3 min of oxygenation by nasal cannula at 15 lpm (higher than used in maintenance) and face mask. If the patient is obese, has OSA history or habitus, or poor reserve, NIPPV may be considered if no contraindications exist. When the patient is induced, the face mask can be removed for bag valve mask access, but the nasal cannula should be maintained to continue oxygenation.
21.4.2 Positioning
The patient should be positioned with the ear at the same horizontal level as the sternal notch. If the patient is obese, the head of the bed should be elevated to 30–45 degrees to facilitate this positioning, and in obese patients, may also help by taking the pressure from abdominal and thoracic girth off of the diaphragm and upper airway. This will help immensely during the mechanical component of intubation.
21.4.3 Equipment Preparation
Suction device
Oxygenation device
Airway tree for each oxygenation device
Bag-valve-mask device
Oropharyngeal airway
Laryngoscope (direct or video)
Endotracheal tube with smaller size backup, both cuff tested and prepared with 10 cc syringe attached and stylet inserted and shaped to preferred form
Bougie
Monitoring equipment (EtCO2, SpO2, ECG, NIBP or arterial line, clamped ventriculostomy)
Medications
21.4.4 Medications
Having the appropriate medications available is key for intubation success. The following medications should be immediately available in push dose format:
Fentanyl for pretreatment (50–100 mcg)
Sedation (etomidate, ketamine, propofol, depending on critical illness and blood pressure requirements)
Paralysis (rocuronium, vecuronium, succinylcholine)
Ongoing sedation (propofol, midazolam, dexmedetomidine)
Intravenous fluids, with pressure bag ready
Vasoactive agents (phenylephrine, norepinephrine, propofol, nicardipine, labetalol, esmolol), Blood pressure-lowering agents (propofol, nicardipine, labetalol)
21.4.5 Personnel
Adequate personnel should be at the bedside, and each should have one should have a specific role. The procedural plan should be reviewed with the entire group prior to implementation. Duties assigned to personnel may include medication administration, monitoring and alerting the room to blood pressure and SaO2 levels, backup medication administration or runner, intubation and post-intubation assessment, assistant to intubation, ventilation, and endotracheal tube fixation.
21.4.6 Direct Laryngoscopy (DL) Versus Videolaryngoscopy (VL)
Since the advent of videolaryngoscopy, there has been much discussion over which method should be utilized for intubation. There are many considerations to this decision, but patient safety is the most important factor.
DL provides visualization of the cords via manipulation of the mandible, which in some cases may be challenging due to an extreme anterior cord anatomy, small mouth opening, or excessive posterior pharyngeal tissue. In the case of vomiting or blood in the airway, the DL view can be enhanced with suctioning. With DL, a curved blade is typically used, but the challenge of excessive posterior pharyngeal tissue can be overcome by employing a straight blade method of lifting the epiglottis manually to reveal a view of the vocal cords.
VL provides indirect visualization of the cords, especially helpful with anterior cord anatomy, via a hyperacute angled blade. This approach makes placement of the endotracheal tube challenging, as it must navigate around the sharply angled blade. This is facilitated by the rigid stylet, and as the most difficult component of VL intubation, should be practiced in order to overcome mechanical pitfalls. If the patient has excessive vomiting or blood in the airway, the camera view of the VL may be obliterated and thereby not useful in real time. VL by definition includes the use of electronic equipment, which may be subject to failure, including battery power. In this way, it requires a dependable backup.
There are many new laryngoscopic tools available, some of which combine videolaryngoscopy with straight and curved as well as hyperacute curved blades, which resolves the issue of obtaining a view in different challenging situations. These are expensive, and it is the opinion of the authors that the medical professional doing the procedure should be familiar with both DL and VL.
The details of the intubation procedure are outside of the scope of this chapter, but this procedure can be lifesaving or life-threatening and should be practiced under the supervision of an experienced professional before practicing without backup. It is always optimal to have anesthesia personnel available as backup in case of need.
21.5 Post-intubation Assessment and Care
Successful intubation should be assessed by multiple methods: visualization of the tube going through the cords, auscultation of breath sounds over both lung fields and none over the gastrum, end-tidal capnography confirming CO2 levels and appropriate waveform, end-tidal capnometry with confirmed color change, pulse oximetry, fog on the endotracheal tube fogging, and chest x-ray. The patient’s hemodynamic and oxygenation status should be monitored closely, including pre, peri and post-intubation to assess for any needed medications to maintain adequate blood pressure and CO2 levels. If long-acting paralytics are used, it is vitally important to start an infusion for sedation, as the paralytic effect will likely outlast the effect of sedation used for intubation. Chest x-ray should be viewed to confirm endotracheal tube placement as well as to assess for other complications such as pneumothorax.
21.6 Modes of Ventilation [6, 10]:
There are many different modes of mechanical ventilation. Each institutional preference may vary, depending on the type of ventilator and previous experience of respiratory therapists and clinical staff. There are four conventional modes of ventilation, volume assist-control mode (VAC), synchronized intermittent mechanical ventilation (SIMV), pressure control ventilation (PCV), and pressure support ventilation (PSV).
21.6.1 Volume Assist-Control Mode
Volume assist-control (VAC) mode is most often used at the start of mechanical ventilation (Hasan). In VAC the clinician sets a respiratory rate (RR) and tidal volume (TV). In general the RR is set for normal breathing (12–16 breaths per minute), and the TV is set anywhere between 6 and 10 ml/kg of ideal body weight. Lower tidal volumes reduce the risk of barotrauma on the lungs. The clinician should set the RR and TV to generate a normal minute ventilation (6–8 L/min). If the ventilator is set with an RR of 12 and a TV of 500 ml, the patient will receive 12 breaths with associated TV of 500 ml every minute. If able, the patient can breathe at an RR greater than 12, and in this ventilation mode, every breath will still be delivered at a TV of 500 ml. Most patients who have intact brainstem function will be able to independently regulate minute ventilation. With VAC ventilation, the clinician can guarantee the minute ventilation by setting the RR and TV, and limit the work of breathing, which is ideal for chemically paralyzed or high spinal cord injury patients with limited or no diaphragm function. There are some disadvantages associated with VAC, including the possibility of barotrauma in patients with decreased compliance, and muscle atrophy due to minimal respiratory effort in patients with prolonged course of mechanical ventilation.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
