Chapter 39

• Acute-on-chronic respiratory failure (ACRF) occurs when relatively minor, although often multiple, insults cause acute deterioration in a patient with chronic respiratory insufficiency.
• ACRF is usually seen in patients known to have severe chronic obstructive pulmonary disease (COPD), but occasionally it manifests as cryptic respiratory failure or postoperative ventilator dependence in a patient with no known lung disease.
• The wide variety of causes of ACRF may be compartmentalized into causes of incremental load, diminished neuromuscular competence, or depressed drive, superimposed on a limited ventilatory reserve.
• Intrinsic positive end-expiratory pressure (PEEPi) is a central contributor to the excess work of breathing in patients with ACRF.
• The most important therapeutic interventions are administration of oxygen, bronchodilators, and corticosteroids, and noninvasive positive pressure ventilation (NIPPV).
• NIPPV can be used in most patients to avoid intubation and has been shown to improve survival.
• The decision to intubate a patient with ACRF benefits from clinical judgment and a bedside presence. Hypotension and severe alkalemia commonly complicate the immediate periintubation course, but they are usually avoidable.
• Ventilator settings should mimic the patient's breathing pattern, with a relatively rapid rate (e.g., 20/min) and small tidal volume (e.g., 450 mL); some positive end-expiratory pressure (e.g., 5 cm H2O) should be added.
• Prevention of complications such as gastrointestinal hemorrhage, venous thrombosis, and nosocomial infection is a crucial component of the care plan.
• The key to liberating the patient from the ventilator is to increase neuromuscular competence while reducing respiratory system load.
• In selected patients, extubation to NIPPV despite failed spontaneous breathing trials reduces ventilator and ICU days and further improves survival.

In the past three decades, mortality from chronic obstructive pulmonary disease (COPD) has risen dramatically, making COPD the fourth leading cause of death in 2000.1 Compared with people with normal lung function, subjects with severe COPD (forced expiratory volume in 1 second [FEV1] <50% predicted) followed for 22 years as part of the National Health and Nutrition Examination Survey (NHANES I) had a 2.7-fold increased risk of death (95% CI 2.1 to 3.5) in an adjusted analysis.2 This trend is apparent in men and women, more prominent in black Americans, and clearly related to cigarette smoking. For the first time, in 2000 more women than men died of COPD in the U.S.1 Admissions to ICUs for exacerbations of COPD account for a substantial portion of bed-days,3 since these patients often require prolonged ventilatory support. In surgical ICUs, COPD is an important problem as well, since it is one of the more common reasons for a prolonged postoperative recovery. An approach to this disease is an essential component of the intensivist's armamentarium.

This chapter describes the pathophysiology and management of patients with chronic pulmonary disease (most with COPD) who require intensive care for decompensation of their normally precariously balanced ventilatory state. This acute deterioration superimposed on stable disease is termed acute-on-chronic respiratory failure (ACRF). Patients may present to the ICU with worsening dyspnea, deteriorating mental status, or respiratory arrest. Especially when there is a preexisting diagnosis of lung disease, the diagnosis of ACRF can be made easily. However, it is important to remember that not all patients ...

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