Large tidal volume mechanical ventilation induces vascular dysfunction in rats.
BACKGROUND
Experimental studies have shown that mechanical ventilation using high tidal volumes (V(T)) damages the lungs, causing pulmonary edema. We tested the hypothesis that high V(T) ventilation in rats induces major vascular dysfunction.


METHODS
Healthy Sprague-Dawley rats, weighing (mean +/- SD) 340 +/- 15 g, were ventilated with either V(T) = 9 mL/kg and positive end-expiratory pressure (PEEP) = 8 (n = 8) or V(T) = 35 mL/kg and PEEP = 0 (n = 8). The high V(T) used in the injurious ventilation group is in the V(T) range used in other studies to induce lung damage in a short period of time in rats. Lungs were removed for examination under light microscopy and vascular rings from the thoracic aorta were studied for isometric tension recording.


RESULTS
Relaxations to acetylcholine (p < 0.001) and sodium nitroprusside (p < 0.05) and contractions to norepinephrine were markedly decreased (p < 0.001) in the high V(T) group, as compared with the low V(T) group.


CONCLUSIONS
Injurious mechanical ventilation in normal rats is associated with vascular dysfunction characterized by decreased relaxation to an endothelium-dependent vasodilator and to a nitrous oxide donor and by decreased response to norepinephrine.
Nin
Nicolás
N
Servicio de Cuidados Intensivos, Hospital Universitario de Getafe, Madrid, Spain.
Valero
José A
JA
Lorente
José A
JA
de Paula
Marta
M
Fernández-Segoviano
Pilar
P
Sánchez-Ferrer
Alberto
A
Esteban
Andrés
A
D000704:Analysis of Variance; D000818:Animals; D001013:Aorta, Thoracic / Q000473:pathology*; D008168:Lung / Q000098:blood supply* / Q000473:pathology; D008297:Male; D010784:Photomicrography; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D013990:Tidal Volume; D014652:Vascular Diseases / Q000209:etiology* / Q000473:pathology