Rescue ventilation with high frequency oscillation in premature baboons with hyaline membrane disease

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Abstract
We tested the hypothesis that high‐frequency oscillatory ventilation can be efficacious in hyaline membrane disease (HMD) even after lung injury is established. We compared high frequency oscillatory ventilation (HFOV) rescue (n = 8; 15 Hz; I:E = 1:2) after 8 hours of positive pressure ventilation (PPV) with positive end‐expiratory pressure, to continued PPV (control, n = 7) in premature baboons with HMD over a 24 hour period. Ventilator settings and physiologic parameters were recorded hourly. At necropsy (24 hours), lung status pressure‐volume curves, alveolar phospholipids (PL), platelet activating factor‐like activity (PAF), and lung water were determined. Roentgenographic and morphologic differences in lung inflation were quantified by standard techniques. No intergroup differences were found in heart rate, blood pressures, ventilator settings, FiO2, blood gases, or chest radiographs during the first 8 hours. Both groups had progressive physiologic disease. At 8 hours, HFOV‐rescue animals, in contrast to controls, had immediate significant time‐related improvements in Pa/AO2 (at the same Paw) and in oxygenation index (Pa/AO2/Paw) lasting for 16 hours. No significant intergroup differences in lung/body weight, lung water, lung mechanics, PL, PAF, or frequency of moderate to severe roentgenographic changes existed at 24 hours. Although all animals had morphologic evidence of HMD, saccular aeration was more uniform and airway dilatation less evident in HFOV rescue (P < 0.0001). Based on the improved gas exchange, we conclude that HFOV rescue was efficacious in the “late” treatment of HMD, presumably because of the more uniform saccular aeration. Though HFOV rescue did not appear to reverse lung injury incurred during the first 8 hours of PPV, it may have interrupted the progression of injury, as seen in the PPV control group.