Critical Care Medicine
This patient most likely has severe air trapping with significant auto-positive end-expiratory pressure (PEEP)/intrinsic PEEP (iPEEP). iPEEP will reduce venous return and therefore also cardiac output and blood pressure. The resistance to expiration may result in significant iPEEP with hemodynamic compromise. The iPEEP and/or the exhaled tidal volumes must be measured in all patients to avoid significant air trapping. A low inspiratory-expiratory ratio (long expiration) should always be used. Permissive hypoventilation may be required in patients with severe airway obstruction. Extrinsic PEEP should be avoided in asthmatic patients because it has not been shown to increase alveolar ventilation; it may also increase air trapping. iPEEP can be diminished by either decreasing the ventilator rate or increasing the flow. The latter step, however, may increase the peak airway pressure. The low dynamic compliance results in high airway pressures with attendant risk of barotrauma.
- Reduce the respiratory rate.
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