title: Inspiration: expiration ratio. Is mean airway pressure the difference?
abstract: Mechanical ventilation with different ratios of inspiratory to expiratory times (I:E ratio) and levels of positive end-expiratory pressure (PEEP) were applied to 9 dogs after the aspiration of fresh water and then were compared. The dogs were ventilated with an I:E ratio of 2:1 with 0 PEEP; an I:E ratio of 2:1 with 5 torr PEEP; and an I:E ratio of 1:2 with 5 torr PEEP. Peak airway pressures were regulated to maintain a mean airway pressure of 13 mm Hg. Arterial oxygenation was better with an I:E ratio of 1:2 with PEEP than with an I:E ratio of 2:1 either with or without PEEP (60 +/- 15 torr as compared with 42 +/- 11 torr and 43 +/- 10 torr). Cardiac index was depressed with all ventilatory modes, but oxygen delivery did not significantly differ among all the modes of ventilation. A ratio of prolonged I:E was not seen to benefit blood gas tension.
mesh_terms: D000403:Airway Resistance; D000818:Animals; D001274:Atmospheric Pressure; D002302:Cardiac Output; D004285:Dogs; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011175:Positive-Pressure Respiration / Q000379:methods*; D012121:Respiration, Artificial / Q000379:methods*
chemical_list: D010100:Oxygen