A patient develops acute hypercapnic respiratory failure due to muscle fatigue. Which of the fol-lowing modes of ventilatory support would you consider for this patient?

1. Assist-control ventilation with adequate backup
2. Continuous positive airway pressure
3. Intermittent mandatory ventilation with adequate backup rate
4. Bilevel pressure support by mask
a. 2 and 4 only
b. 3 and 4 only
c. 1, 2, and 3 only
d. 1, 3, and 4 only

ANS: D
Noninvasive positive-pressure ventilation can improve hypoxemia and hypercarbia by several mechanisms including but not limited to (1) compensating for the inspiratory threshold load im-posed by intrinsic positive end-expiration pressure, (2) supplementing a reduced tidal volume, (3) partial or complete unloading of the respiratory muscles, (4) reducing venous return and left ven-tricular afterload, and (5) alveolar recruitment.