Lung volume and the response to high volume strategy, high frequency oscillation

Abstract

Background: Infants with severe respiratory failure are frequently transferred to high volume strategy, high frequency oscillation (HFO). Mean airway pressure (MAP) is then elevated, the aim being to open up atelectatic lungs and hence improve gas exchange. Aim: To test the hypothesis that lung volume prior to transfer would predict the response to high volume strategy HFO and identify which factors related to poor outcome (death). Methods: Lung volume was assessed by measurement of functional residual capacity (FRC) and the response to HFO determined by the change in the alveolar arterial gradient (AaDO2) on transfer from conventional mechanical ventilation (CMV) to the optimal MAP on high volume strategy HFO. Patients: Forty-two infants with a median gestational age of 28 (range 23 to 40) wk were studied. Results: FRC prior to transfer correlated significantly with the change in MAP necessary to optimize oxygenation (p = 0.012), but not the change in AaDO2 in response to HFO. There were no significant differences in the lung volumes of survivors and non-survivors, but those who died were more immature (p = 0.0009) and had a smaller response to HFO (p = 0.035). Conclusion: Lung volume prior to transfer to high volume strategy HFO might be helpful to guide oscillatory settings, but is a poor predictor of the response to high volume strategy HFO.