Treatment Complications
H.3 Sleep Disorders

Acute respiratory failure, (ARF), is a severe complication in the patient with COPD. ARF is broadly defined as an acute worsening of blood gases to a degree that represents a threat to life. The exact definition may vary but usually consists of a significant and sudden change from the baseline arterial blood gas values to a pco2 >50 mm Hg with a pH of <7.30 and/or a po2 <50 mm Hg.

Diagnosis

ARF presents as a deterioration in clinical status, usually the onset or worsening of respiratory symptoms such as cough and dyspnea. However, central nervous system symptoms, including irritability or drowsiness, may be the most prominent. Presenting symptoms may also reflect the acute condition which precipitates the ARF. For example, complications caused by a respiratory infection can include an exacerbation of bronchitis or pneumonia. A variety of other conditions, including congestive heart failure or any systemic condition which increases metabolic demands, may contribute. Once the diagnosis is suspected, it should be confirmed by obtaining arterial blood gases analyses.

Prognosis

The prognosis of ARF in the COPD patient is better than commonly believed. Approximately 90% of patients survive the acute episode. Prognosis following ARF depends on the underlying lung function and is no different for a patient who has had ARF compared to one who has not, provided that their fev1 values are the same.

Treatment

Patients with ARF generally require hospitalization, but less severe exacerbations can be treated in the outpatient setting according to the steps described in Section G. The treatment of ARF in any patient has four objectives: 1) The correction of physiologic abnormalities–with the correction of hypoxemia using supplemental oxygen being especially important; 2) aggressive treatment of airflow obstruction, including bronchodilator therapy, administration of corticosteroids, and the removal of airway secretions; 3) treatment for the factor precipitating ARF; and 4) the prevention of complications. In addition to these, mechanical ventilation may be required in a minority of patients. Important points regarding these aspects of management are summarized in Table 6.

Correcting life-threatening hypoxemia is particularly important. The goal of oxygen therapy is to achieve an arterial oxygen saturation above 90%, which generally means an arterial PO2 of approximately 60 mm Hg. Usually a small amount of supplemental oxygen (1 to 2 liters per minute via nasal prongs) will suffice to provide this level of oxygenation. Higher amounts of supplemental oxygen may be necessary if the patient has a significant right-to-left shunt, which may be associated with pneumonia or congestive heart failure. Although progressive respiratory acidosis can complicate oxygen administration in ARF, the incidence of this complication has been overemphasized. More importantly, if O2 therapy is prudently administered and monitored by repeated measurements of arterial blood, the therapeutic goal can be achieved without a significant CO2 increase in nearly all patients.

Treating a potentially reversible component of airflow obstruction is one of the most important aspects of therapy. Even when a patient has not responded to bronchodilation during their stable state, he or she may display a reversible obstructive component during ARF. Therefore, inhaled bronchodilators should be given aggressively and should include inhaled ipratropium bromide and an inhaled beta-agonist. Corticosteroids should be given, initially intravenously as methylprednisolone sodium succinate, at least 125 mg/day in divided doses. Oral prednisone may be given later (60 mg/day with a gradual taper from that dose) once it is assured that the patient is able to eat and does not have an ileus. Intravenous aminophylline should be given in an average maintenance dose of 0.6 mg/kg/hr in patients already receiving oral theophylline. If the patient has not significantly improved within 12 to 24 hours with inhaled bronchodilators and intravenous corticosteroids and has not been receiving oral theophylline, intravenous theophylline should be added in a loading dose of 3 to 5 mg/kg to be followed by the above-described maintenance dose.

Also, since most patients with acute respiratory failure have problems with retained secretions, these should be addressed therapeutically. Treatment for retained secretions consists primarily of adequate hydration (not overhydration) and encouraging the patient to cough (sitting upright in a position that enhances the ability to cough) following a dose of inhaled bronchodilators.

Specific treatment for any recognized precipitating factors should be given. Broad-spectrum antibiotics are required when there is even the slightest suspicion of bacterial bronchitis or if pneumonia is diagnosed, as discussed in Section H.1.

Mechanical ventilation may be needed in a minority (approximately 10%) of COPD patients with ARF. The decision to use mechanical ventilation is based primarily on clinical grounds rather than any particular level of blood gas abnormalities. Worsening mental status with an onset of lethargy, confusion, and somnolence– despite aggressive administration of the above therapies –is the primary indication. If one is not experienced in supervising mechanical ventilation, consultation with a pulmonary specialist is warranted. Some aspects of mechanical ventilation of particular importance in the COPD patient are outlined in Table 7. Alternatives to intubation and mechanical ventilation (e.g., noninvasive ventilation using a face mask) are currently being explored and should be considered only if expertise with these techniques is locally available.

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Table 7 Management of Acute Respiratory Failure

Management of Acute Respiratory Failure in Selected Patients Requiring Mechanical Ventilation

Institute Mechanical Ventilation If Mental Status Deteriorates

A. Prevent barotrauma and impaired cardiac output because of intrinsic PEEP on mechanical ventilation.

1. Use modest tidal volume (7 to 8 mL/kg).
2. Minimize VE, peak, and mean airway pressures.

B. If intrinsic PEEP develops, attempt to:

1. Decrease respiratory rate.
2. Increase inspiratory flow rate (approximately 5 to 6 x VE).
3. Decrease tidal volume.
4. Try pressure support.

PEEP=Positive end expiratory pressure

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The possibility of endotracheal intubation and mechanical ventilation should be discussed with each patient with severe COPD and his or her family while stable (as an outpatient) to establish directives regarding the patient's wishes. If there is an acute precipitating cause which is potentially reversible, then prognosis with mechanical ventilation is favorable. Frequently, however, no readily reversible component can be identified, but even then patients may respond favorably. Therefore, it is recommended that you discuss whether or not to withdraw support if the patient does not improve after many days of aggressive treatment. This option allows the chance for successful treatment for ARF, but also allows patients to avoid a situation that many fear: that they will require prolonged mechanical ventilation that may not be compatible with an acceptable quality of life. If the decision is made to withdraw mechanical ventilatory support, the goal of treatment becomes patient comfort. Narcotics should be given as needed.

Noninvasive Mechanical Ventilation

In recent years, the technique of noninvasive mechanical ventilation has begun to replace more invasive mechanical ventilation with intubation. Thus, with tight-fitting, comfortable face masks, and practical, safe, home mechanical ventilators, noninvasive positive pressure breathing is commonly used both in hospitals and within the home, in the short-term to deal with exacerbations of COPD. Some patients can achieve rest and restoration of respiratory muscle function during short periods of nocturnal mechanical ventilation during either positive pressure breathing or non-invasively, without a mask, with negative pressure mechanical ventilation using body wrap or cuirass-type ventilators. It is stressed that noninvasive mechanical ventilation only assists the patient’s efforts in breathing, and cannot be used to take over the complete ventilatory support of patients. Nonetheless, non-invasive mechanical ventilation will replace intubation with mechanical ventilation in an increasing number of patients in the future, as techniques improve.

References

Albert RK, Martin TR, Lewis SW. Controlled clinical trial of methylprednisolone in patients with chronic bronchitis and acute respiratory insufficiency. Ann Int Med 1980; 92:753-758. This well-controlled clinical trial showed an objective improvement in fev1 with corticosteroid use compared with placebo. The differences were small but statistically significant.

American Thoracic Society. Withholding and withdrawing life sustaining therapy. Am Rev Respir Dis 1989;140 (Part 2):S1-S107. This is a detailed report of a nih-sponsored workshop, “Withholding and Withdrawing Mechanical Ventilation.”

Chevrolet JC, Jolliet P, Abajo B, et al. Nasal positive pressure ventilation in patients with acute respiratory failure. Difficult and time-consuming procedure for nurses. Chest 1991; 100:775-782. This report on the use of a noninvasive method of mechanical ventilation found it time consuming and not effective in interstitial fibrosis.

Curtis JR, Hudson LD. Emergent assessment and management of acute respiratory failure in COPD. Clin Chest Med 1994;15:481-500. This is a state-of-the-art review of contemporary strategies for the management of acute respiratory failure.

Derenne J, Fleury B, Pariente R. Acute respiratory failure of chronic obstructive pulmonary disease. Am Rev Respir Dis 1988; 138:1006-1033. This is a complete review of the pathophysiology and treatment of acute respiratory failure in COPD.

Karpel JP. Bronchodilator responses to anticholinergic and beta-adrenergic agents in acute and stable COPD. Chest 1991; 99:871-876. This study showed that ipratropium and metaproterenol were equally effective in the doses used.