Respiratory failure is defined as respiratory dysfunction resulting in abnormalities of oxygenation or ventilation (CO2 elimination) severe enough to threaten the function of vital organs. Arterial blood gas criteria for respiratory failure are not absolute but may be arbitrarily established as a PO2 under 60 mm Hg (7.8 kPa) or a PCO2 over 50 mm Hg (6.5 kPa). Acute respiratory failure may occur in a variety of pulmonary and nonpulmonary disorders (Table 9–27). Only a few selected general principles of management will be reviewed here.
Table 9–27.Selected causes of acute respiratory failure in adults. ||Download (.pdf) Table 9–27. Selected causes of acute respiratory failure in adults.
Acute exacerbation of chronic bronchitis or emphysema
Obstruction of pharynx, larynx, trachea, mainstem bronchus, or lobar bronchus by edema, mucus, mass, or foreign body
Increased hydrostatic pressure
Left ventricular dysfunction (eg, myocardial ischemia, heart failure)
Left atrial outflow obstruction (eg, mitral stenosis)
Volume overload states
Increased pulmonary capillary permeability
Acute respiratory distress syndrome
Acute lung injury
Negative pressure (inspiratory airway obstruction)
Parenchymal lung disorders
Interstitial lung diseases
Diffuse alveolar hemorrhage syndromes
Pulmonary vascular disorders
Amniotic fluid embolism
Chest wall, diaphragm, and pleural disorders
Abdominal distention and abdominal compartment syndrome
Neuromuscular and related disorders
Primary neuromuscular diseases
Drug- or toxin-induced
Neuromuscular blocking agents
Spinal cord injury
Phrenic nerve injury or dysfunction
Central nervous system disorders
Drugs: sedatives, hypnotics, opioids, anesthetics
Brainstem respiratory center disorders: trauma, tumor, vascular disorders, hypothyroidism
Central nervous system infections
Increased CO2 production
Hyperalimentation with excess caloric and carbohydrate intake
Symptoms and signs of acute respiratory failure are those of the underlying disease combined with those of hypoxemia or hypercapnia. The chief symptom of hypoxemia is dyspnea, though profound hypoxemia may exist in the absence of complaints. Signs of hypoxemia include cyanosis, restlessness, confusion, anxiety, delirium, tachypnea, bradycardia or tachycardia, hypertension, cardiac dysrhythmias, and tremor. Dyspnea and headache are the cardinal symptoms of hypercapnia. Signs of hypercapnia include peripheral and conjunctival hyperemia, hypertension, tachycardia, tachypnea, impaired consciousness, papilledema, and asterixis. The symptoms and signs of acute respiratory failure are both insensitive and nonspecific; therefore, the clinician must maintain a high index of suspicion and obtain arterial blood gas analysis if respiratory failure is suspected.
Treatment of the patient with acute respiratory failure consists of (1) specific therapy directed toward the underlying disease, (2) respiratory supportive care directed toward the maintenance of adequate gas exchange, and (3) general supportive care. Only the last two aspects are discussed below.