Effect of High-frequency Ventilation on the Development of Alveolar Edema in Premature Monkeys at Risk for Hyaline Membrane Disease

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Abstract
High-frequency oscillatory ventilation (HFOV) permits adequate gas exchange but avoids the large phasic pressure-volume excursions of conventional mechanical ventilation (CMV); such avoidance may reduce the lung injury associated with hyaline membrane disease (HMD). We hypothesized that premature monkeys ventilated from birth with HFOV would have reduced lung injury compared to those assigned to CMV. Macaca nemestrina were delivered at 134 days (80% of term gestation) and ventilated from the first breath with either HFOV (n = 10) or CMV (n = 10). The mean airway pressure (Paw) was kept at 15 cm H2O pressure in HFOV animals; in CMV animals Paw was increased from 8 cm H2O at 2 h to 13 cm H2O at 6 h to prevent hypoxemia. At the conclusion of the 6-h experiment the HFOV animals had better oxygenation (p less than 0.05) and less evidence of HMD by chest radiograph (p less than 0.05). At 6 h of age a piece of the right middle lung lobe was removed, divided, and placed in fixatives for light and transmission electron microscopy. The lungs were subsequently inflated to 30 cm H2O pressure, and the right lower lobe was rapidly frozen in situ for morphometric studies. The proportion of peripheral lung tissue occupied by clear alveoli was greater in HFOV animals (66.3 +/- 14.8%) than in those assigned to CMV (44.2 +/- 16.9%, p less than 0.01); less alveolar debris and fluid was present in the HFOV animals (12.7 +/- 9.9%) compared with CMV animals (27.1 +/- 12.5%, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)