Abstract
Because of high airway resistance and low lung compliance in severe RDS, it has been suggested that a respirator able to produce a square pressure waveform may provide better oxygenation & ventilation. To test this hypothesis we made a study of 15 neonates with severe RDS. Two most commonly used infant respirators, one a time-cycled, continuous flow, generating modified sine ware with slow ascending inspiratory limb and slow descending expiratory limb (I), and a second, generating a square wave with rapid inspiratory and expiratory limb (II) were used. Neonates were stabilized for a period of 6-8 hrs on respirator I when pH, PaO2 and PaCO2 were determined before switching to respirator II. Respirators were matched for FiO2, Peak Inspiratory Pressure, End Expiratory Pressure, I:E ratio and Duration of Positive Pressure (DPP) or the area under the curve of respiratory waveform. After 20 minutes on respirator II pH and blood gases were done before switching back to respirator I, and again, after 20 min, pH and blood gases were obtained. Values were compared for the two variables of equal DPP and equal area under the curve. Statistically significant differences were found for PaO2 (71±16vs62±16 Torr, p<0.05 for equal DPP; and 71±16vs52±14 Torr, p< 0.005 for equal area under the curve) but not for pH or PaCO2 for either variable. This study reveals that respirators generating modified sine wave respiratory waveform provide better oxygenation in severe RDS. This may be due to an increase in alveolar recruitment when low compliant lungs are gradually inflated and deflated
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Modanlou, H., Nelson, P. 1211 RELATIONSHIP BETWEEN RESPIRATOR WAVEFORM AND OXYGENATION-VENTILATION IN RESPIRATORY DISTRESS SYNDROME (RDS). Pediatr Res 12 (Suppl 4), 565 (1978). https://doi.org/10.1203/00006450-197804001-01217
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DOI: https://doi.org/10.1203/00006450-197804001-01217