Effect of peak inspiratory flow on gas exchange, pulmonary mechanics, and lung histology in rabbits with injured lungs.
OBJECTIVE
The aim of this study was to evaluate, using a rabbit model, the little-known effect of different levels of peak inspiratory flow on acutely injured lungs.


METHODS
Fourteen male rabbits (body weight, 2,711 +/- 146 g) were anesthetized and their lungs were injured by alveolar overstretch with mechanical ventilation until Pa(O(2)) was reduced below 300 mmHg. Injured animals were randomly assigned to: the P group-to receive pressure-regulated volume-control ventilation (PRVCV; n = 7); and the V group-to receive volume-control ventilation (VCV; n = 7). Other ventilator settings were: fraction of inspired oxygen (FI(O(2)), 1.0; tidal volume, 20 ml x kg(-1); positive end-expiratory pressure (PEEP) 5 cmH(2)O; and respiratory rate, 20 min(-1). The animals were thus ventilated for 4 h. Throughout the protocol, ventilatory parameters and blood gas were measured every 30 min. After the protocol, the lung wet-to-dry ratio and histological lung injury score were evaluated in the excised lungs.


RESULTS
Throughout the protocol, peak inspiratory flow and mean inspiratory flow values in the P group were significantly higher than those in the V group (26.7 +/- 5.0 l x min(-1) vs 1.2 +/- 0.2 l x min(-1), and 4.3 +/- 0.3 l x min(-1) vs 1.1 +/- 0.1 l x min(-1); P < 0.05). The wet-to-dry ratio in the P group was also significantly higher than that in the V group (7.7 +/- 0.9 vs 6.3 +/- 0.5; P < 0.05). More animals in the P group than in the V group had end-of-protocol Pa(O(2))/FI(O(2)) ratios below 200 mmHg (43% vs 0%; P = 0.06).


CONCLUSIONS
In rabbits with injured lungs, high peak inspiratory flow with high tidal volume (V(T)) reduces the Pa(O(2))/FI(O(2)) ratio and increases the lung wet-to-dry ratio.
Fujita
Yasuki
Y
Intensive Care Unit, Osaka University Hospital, 2-15 Yamadaoka, Suita 565-0871, Japan.
Maeda
Yoshiko
Y
Fujino
Yuji
Y
Uchiyama
Akinori
A
Mashimo
Takashi
T
Nishimura
Masaji
M
D000818:Animals; D001784:Blood Gas Analysis; D001831:Body Temperature / Q000502:physiology; D005260:Female; D008168:Lung / Q000473:pathology*; D055370:Lung Injury; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D011659:Pulmonary Gas Exchange; D011817:Rabbits; D012121:Respiration, Artificial / Q000009:adverse effects*; D015656:Respiratory Mechanics / Q000502:physiology*