دانلود کتاب پرسش و پاسخ مراقبت های ویژه جراحی و جراحی اورژانسی

1- In a patient who develops ARDS, the addition of PEEP in optimizing ventilatory support has which of the following effects?

A Maximal alveolar recruitment with inspiration.
B Decreasing mean airway pressure.
C Decreased right ventricular afterload.
D Improvement of functional residual capacity (FRC).
E Increasing left ventricular afterload.

The use of positive end-expiratory pressure (PEEP) as part of the ARDS ventilatory strategy has been shown to improve the functional residual capacity (FRC) above the closing pressure of alveoli, thereby preventing alveolar collapse. PEEP maximizes alveolar recruitment at end expiration, not inspiration. The addition of PEEP increases inflation pressure, thereby increasing peak alveolar pressure and ultimately mean airway pressure. Increased PEEP increases pulmonary vascular resistance impeding right vascular stroke volume and thereby left ventricular filling. It also decreases the transmural pressure – the pressure needed to be overcome in order to eject stroke volume – thereby decreasing left ventricular afterload.