EFFECTS OF INTERMITTENT POSITIVE-PRESSURE VENTILATION ON LUNGS OF NORMAL RABBITS

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 61  (3) , 315-323
Abstract
Ten healthy young rabbits were ventilated with warm, moist air at 20 cm H2O peak airway pressure. Their pulmonary histology was compared to that of 10 controls. Histological changes were analyzed using the Leitz Texture Analysis System. High-power fields (400) (240 .times. 240 .mu.m) were scanned from each section and the mean proportions of air space, interstitium and edema determined. Calculated bicarbonate decreased significantly in both groups (P < 0.05); this was accompanied by a modest decrease in pHa [arterial pH] in the ventilated group. PaO2 [arterial O2 pressure] and PaCO2 [arterial CO2 pressure] were maintained within the normal range. The blood pressure decreased in both groups. Of 10 ventilated rabbits, 7 had interstitial widening while only 1 of 10 controls had a similar lesion (.chi.2 = 5.21, P = < 0.05). The area occupied by insterstitium ranged from 26 to 46% (mean 37.6%) in controls and 18 to 81% (mean 45.4%) in ventilated rabbits. There was a lack of correlation between clinical and histopathological findings. While 6 of 10 ventilated rabbits had intra-alveolar edema and a decrease in air space to less than 50% of total area, none developed hypoxemia. Two of these 6 rabbits also had pHa less than 7.35 by the end of the study, yet all were clinically stable. Apparently, intermittent partial pressure ventilation with warm, moist air may result in pulmonary parenchymal damage within 6 h in healthy rabbits.