Effect of prone position without PEEP on oxygenation and complacency in an experimental model.
OBJECTIVE
To observe the effects of the prone position and the need for positive end-expiratory pressure (PEEP) to improve oxygenation.


METHODS
Sixteen rats were anesthetized and ventilated at a tidal volume of 8 mL/kg, respiratory rate of 60 rpm and PEEP = 0 cmH(2)O (ZEEP), in the supine position for 30 minutes. Lung injury was then induced by means of intratracheal instillation of hydrochloric acid. Once the injury was established, rats were placed in the prone position for a further 30 minutes and randomized into two groups: in group 1 PEEP = 5 cmH(2)O was added; while group 2 was kept on ZEEP. Measurements of pulmonary mechanics, arterial blood gas analysis and mean arterial pressure were taken at the end of each phase.


RESULTS
In group 1, oxygen partial pressure increased significantly from 98.7+/-26.5 to 173.9+/-58.4 mmHg between injury and prone phases; in group 2 it was unchanged, varying from 99.6+/-15.4 to 100.5+/-24.5 mmHg. Group 1 also exhibited significant improvement in complacency, from 0.20+/-0.01 to 0.23+/-0.02 mL/cmH(2)O, while, once more, group 2 did not exhibit improvement, going from 0.21+/-0.02 to 0.22+/-0.01 mL/cmH(2)O. Mean arterial blood pressure measurements did not change significantly in either group at any point during the experiment.


CONCLUSIONS
The prone position only resulted in improved oxygenation and respiratory mechanics when combined with PEEP = 5 cmH(2)O. The prone position did not cause hemodynamic compromise with or without PEEP = 5 cmH(2)O.
Yagui
Ana Cristina Z
AC
Universidade Federal de São Paulo - Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, SP, Brazil. anac.yagui@gmail.com
Beppu
Oswaldo S
OS
D000818:Animals; D004195:Disease Models, Animal; D008297:Male; D010100:Oxygen / Q000097:blood*; D011175:Positive-Pressure Respiration; D016684:Prone Position; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy; D014109:Total Lung Capacity / Q000502:physiology*
D010100:Oxygen