There are a number of confounders that make airway management of the patient with asthma or chronic obstructive pulmonary disease (COPD) challenging. These patients are often hypoxic, desaturate quickly, and can be hemodynamically unstable. Unlike many other clinical conditions, intubation itself does not resolve the primary problem, which is obstruction of the small, distal airways. The actual intubation may be the easiest part of the resuscitative sequence because postintubation ventilation may be extremely difficult with persistent or worsening respiratory acidosis, barotrauma, or worsening hypotension caused by high-intrathoracic pressures with diminished venous return. Thus, the decision to intubate must be made carefully, and the appropriate technique must be chosen to facilitate the best possible outcome.

Severe asthma often presents one of the most difficult airway management cases encountered in the emergency department. Diaphoresis is a particularly ominous sign, and the diaphoretic asthmatic patient who cannot speak full sentences, appears anxious, or is sitting upright and leaning forward to augment the inspiratory effort must not be left unattended until stabilized.

Standard initial management of acute severe asthma exacerbation includes reversal of dynamic bronchospasm using continuous β₂-agonist nebulization therapy (Albuterol 10-15 mg per hour) and anticholinergic nebulization therapy (ipratropium bromide 0.5 mg every 20 minutes for three doses). In addition, oral or intravenous (IV) steroids are indicated for the treatment of the inflammatory component. If the patient is severely bronchospastic and cannot comply with a nebulized treatment, subcutaneous epinephrine or terbutaline 0.3 to 0.5 mg may be of benefit. The use of IV terbutaline is controversial; and has no proven benefit in adults. However, if selected, it should be initiated in the child at 10 µg per kg over 30 minutes followed by a continuous infusion of 0.1-0.4 µg/kg/minute. For severe, refractory asthma, administration of IV magnesium sulfate 2 g in adults and 25-75 mg per kg (up to a maximum of 2 g) in children may be of benefit, although evidence supporting this is mixed. The addition of inhaled or IV anticholinergic agents (atropine or glycopyrrolate), titrated doses of IV ketamine, or inhalational helium/oxygen mixture is controversial but also may be considered in severe cases (Fig. 33-1).

In COPD, much of the obstruction is fixed, comorbidity (especially cardiovascular disease) plays a greater role, and the prognosis (even with short-term mechanical ventilation) is worse. In the patient with COPD, anticholinergic therapy may be as important as β₂-agonist therapy. Steroids are again important to attenuate underlying inflammation. As is the case for many asthma patients, it is progression of fatigue, not worsening bronchospasm that leads to respiratory failure and arrest. The intubated COPD patient may have a prolonged, difficult course, and weaning from the ventilator is not assured. Therefore, unless the patient’s condition forces early or immediate intubation, a trial of noninvasive ventilation is recommended. Noninvasive ventilation (bi-level positive airway pressure [BL-PAP] or continuous positive airway pressure) is of proven value in certain COPD patients and may help avoid intubation (see Chapter 6). As for the asthmatic patient, mechanical ventilation after intubation in COPD is notoriously difficult to manage. Ventilation pressures often are high, and breath stacking (automatic positive end-expiratory pressure [auto-PEEP]) is common, even with excellent ventilator management. Increased intrathoracic pressures induced by mechanical ventilation, combined with volume depletion from the patient’s work of breathing before intubation, coexisting cardiovascular disease, and hemodynamic changes related to decreased sympathetic tone after intubation makes the peri-intubation period highly dynamic and unstable. Ventilator management is discussed below. There is no role for IV aminophylline in the management of either acute severe asthma or acute severe COPD exacerbation, before or after intubation.

Despite this vast array of noninvasive treatment modalities, 1% to 3% of acute severe asthma exacerbations will require intubation. These patients are usually fatigued and have reduced functional residual capacity, so it is difficult (if not impossible) to preoxygenate them optimally, and rapid desaturation
must be anticipated. Because most of these patients have been struggling to breathe against severe resistance, usually for hours, they have little if any residual physical reserve, and mechanical ventilation will be required. In fact, the need for mechanical ventilation is the indication for tracheal intubation; the airway itself is almost invariably patent and protected. This fact argues strongly for rapid sequence intubation (RSI), which often is the preferred method even if a difficult airway is identified on preintubation assessment (the “forced to act” scenario; see Chapters 2 and 3). If the patient has a difficult airway, the operator might plan intubation even earlier than for the nondifficult patient, in an attempt to have the best conditions and greatest amount of time possible for an awake technique.

After the patient is successfully intubated and proper tube position has been confirmed, sedation and analgesia are titrated according to a sedation scale (see Chapter 19). Neuromuscular blockade may be required during the first few hours of mechanical ventilation to prevent asynchronous respirations, promote total relaxation of fatigued respiratory muscles, decrease the production of carbon dioxide, and allow optimal ventilator settings. Often, though, these same goals are achieved using a proper balance of sedation and analgesia. Prolonged neuromuscular blockade is not required and may worsen the patient’s overall course of management. Meticulous ventilator management is critical in achieving the best patient outcome. Additional ketamine, as well as continuous in-line albuterol and other pharmacologic adjuncts, may also be given.