Diagnostic Considerations
Respiratory failure is a common and a life-threatening condition that demands prompt diagnosis and assessment and appropriate management.
Failure to visualize an obvious abnormality on chest radiographs in hypoxemic respiratory failure suggests the possibility of right-to-left shunting.
The vast majority of patients in acute respiratory failure due to cardiogenic pulmonary edema respond to measures to reduce preload and afterload. Those with acute respiratory distress syndrome (ARDS) require early elective intubation because the duration of respiratory failure is longer.
Hypercapnic respiratory failure occurs secondary to a variety of causes, including an increased respiratory muscle load, impaired neuromuscular function, and decreased respiratory drive caused by central nervous system (CNS) depression.
Differential Diagnoses
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Bilateral airspace infiltrates on chest radiograph film secondary to acute respiratory distress syndrome that resulted in respiratory failure.
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Extensive left-lung pneumonia caused respiratory failure; the mechanism of hypoxia is intrapulmonary shunting.
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A 44-year-old woman developed acute respiratory failure and diffuse bilateral infiltrates. She met the clinical criteria for the diagnosis of acute respiratory distress syndrome. In this case, the likely cause was urosepsis.
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This patient developed acute respiratory failure that turned out to be the initial presentation of systemic lupus erythematosus. The lung pathology evidence of diffuse alveolar damage is the characteristic lesion of acute lupus pneumonitis.
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A Bilevel positive airway pressure support machine is shown here. This could be used in spontaneous mode or timed mode (backup rate could be set).
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Headgear and full face mask commonly are used as the interface for noninvasive ventilatory support.
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Bilevel positive airway pressure (BiPAP) and inspiratory positive airway pressure (IPAP) settings are shown. IPAP or expiratory positive airway pressure (EPAP) and frequency can be preset.
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Noninvasive ventilation with bilevel positive airway pressure for acute respiratory failure secondary to exacerbation of chronic obstructive pulmonary disease.
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Wave forms of a volume-targeted ventilator: Pressure, flow, and volume waveforms are shown with square-wave flow pattern. A is baseline, B is increase in tidal volume, C is reduced lung compliance, and D is increase in flow rate. All 3 settings lead to increase in peak airway pressures. Adapted from Spearman CB et al.
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The cause of respiratory failure may be suggested by spirometry.
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A 65-year-old man developed chronic respiratory failure secondary to usual interstitial pneumonitis. Loss of normal architecture is seen upon biopsy. Also seen are varying degrees of inflammation and fibrosis.
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Lung biopsy from a 32-year-old woman who developed fever, diffuse infiltrates seen on chest radiograph, and acute respiratory failure. The lung biopsy shows acute eosinophilic pneumonitis; bronchoscopy with bronchoalveolar lavage also may have helped reveal the diagnosis.
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Lung biopsy on this patient with acute respiratory failure and diffuse pulmonary infiltrates helped yield the diagnosis of pulmonary edema. Therefore, cardiogenic pulmonary edema should be excluded as the cause of respiratory failure prior to considering lung biopsy.
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Pressure-volume curve of a patient with acute respiratory distress syndrome (ARDS) on mechanical ventilation can be constructed. The lower and the upper ends of the curve are flat, and the central portion is straight (where the lungs are most compliant). For optimal mechanical ventilation, patients with ARDS should be kept between the inflection and the deflection point.
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Surgical lung biopsy was performed in the patient described in Image 3. The histology shows features of diffuse alveolar damage, including epithelial injury, hyperplastic type II pneumocytes, and hyaline membranes.
