A 32-year-old man is intubated and mechanically ventilated after an opioid drug overdose. He is sedated and passive. The ventilator triggers 14 breaths per minute, each delivering 500 mL of tidal volume at a peak flow rate of 60 L/min. An inspiratory hold is performed for 2 seconds following delivery of the tidal volume, and the airway pressure is measured to be 30 cm H₂O. The measured pressure most likely reflects which of the following?

Question

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Measurement of airway pressures can be useful in mechanically ventilated patients. The peak airway pressure (the maximum pressure measured as the tidal volume is being delivered) equals the sum of the resistive pressure (flow x resistance) and the plateau pressure. Peak airway pressure = resistive pressure + plateau pressure The plateau pressure is the pressure measured during an inspiratory hold maneuver, when pulmonary airflow and thus resistive pressure are both 0. It represents the sum of the elastic pressure and positive end-expiratory pressure (PEEP). Plateau pressure = elastic pressure + PEEP Elastic pressure is the product of the lung's elastance and the volume of gas delivered. Because elastic recoil is inversely related to lung compliance, the elastic pressure can be calculated as tidal volume/compliance. Decreased compliance (eg, pulmonary fibrosis) causes stiffer lungs and higher elastic pressure. Increased peak pressure associated with an unchanged plateau pressure suggests a pathological process causing increased airway resistance, such as bronchospasm, mucus plug, or endotracheal tube obstruction (Choice B). Elevation of both peak and plateau pressures indicates a process causing decreased pulmonary compliance, such as pulmonary edema, atelectasis, pneumonia, or right mainstem intubation. 11ec25c8_d4bb_ff8f_bc81_69b896fc2121_MD0003_00 (Choice A) It is not possible to calculate upper airway resistance when a patient has an endotracheal tube in place as the tube bypasses the upper airway. (Choice D) Expiratory muscle strength is determined by measuring the patient's forced vital capacity and maximum expiratory pressure. (Choice E) The alveolar end-expiratory pressure is typically equal to the atmospheric pressure. In obstructive lung disease, however, the alveoli cannot empty completely, resulting in higher than normal end-expiratory pressures. This is called intrinsic, or auto-, PEEP. The end-expiration hold maneuver measures auto-PEEP. Educational objective: Peak airway pressure is the sum of airway resistance and plateau pressure. The plateau pressure is the sum of the elastic pressure and positive end-expiratory pressure (PEEP) and is calculated by performing the end-inspiratory hold maneuver. PEEP is calculated with the end-expiratory hold maneuver.

A 32-Year-Old Man Is Intubated and Mechanically Ventilated After an Opioid