During inspiration, alveolar pressure exceeds pleural pressure. The pressure gradients of normal breathing are reversed. During inspiration, pressure in the alveoli increases. During inspiration, pleural pressure decreases. Which of the following occur with positive-pressure ventilation (PPV)? 1. 1, 2, and 3 ANS: C Gas flows into the lungs because pressure at the airway opening (Pawo) is positive and alveolar pressure (Palv) is initially zero or less positive.
In which of the following types of ventilation is alveolar expansion during inspiration due to an increase in alveolar pressure? 1. Thus, gas flows from the relatively high pressure at the airway opening (zero) to the relatively low pressure in the alveoli (negative).
Because the airway opening remains exposed to atmospheric pressure during NPV, a transairway pressure gradient is created. Negative pressure at the body surface (Pbs) is transmitted first to the pleural space and then to the alveoli (Palv). NPV decreases pleural pressure (Ppl) during inspiration by exposing the chest to sub-atmospheric pressure. 1, 3, and 4 only ANS: B Mechanical NPV is similar to spontaneous breathing. NPV decreases pressure at the body surface. Expiration during NPV is by passive recoil. Airway (mouth) pressure during NPV is zero. Which of the following statements are true about negative-pressure ventilation (NPV)? 1. 1, 2, and 3 ANS: C NPV decreases pleural pressure (Pp1) during inspiration by exposing the chest to sub-atmospheric pressure. In which of the following types of ventilation is alveolar expansion during inspiration due to a decrease in pleural pressure? 1.
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