Predicting outcome in children with severe acute respiratory failure treated with high-frequency ventilation.

OBJECTIVES

a) To demonstrate the effect of high-frequency ventilation on gas exchange in children with severe acute respiratory failure unresponsive to conventional ventilation; b) to identify patients at high risk of death early after institution of high-frequency ventilation.

SETTING

Tertiary care pediatric intensive care unit in a university hospital.

DESIGN

A cross-sectional, observational study with factorial design.

PATIENTS: Thirty-one patients with severe acute respiratory failure defined as a Pao2/F1o2 of < 150 torr (< 20 kPa) with a positive end-expiratory pressure of > or = 8 cm H2O and/or Paco2 of > 60 torr (> 8 kPa) with an arterial pH < 7.25.

INTERVENTIONS: Patients received either high-frequency oscillation or jet ventilation if respiratory failure was unresponsive to conventional ventilation and if the underlying disease process was deemed reversible.

MEASUREMENTS AND MAIN

RESULTS

Thirty-one children were managed with high-frequency ventilation, 11 children with jet and 20 children with oscillator. Arterial blood gases and level of ventilatory support were recorded before and at 6, 24, 48, 72, and 96 hrs after institution of high-frequency ventilation. There was an improvement in an arterial pH, Paco2, Pao2, and Pao2/FID2 6 hrs after institution of high-frequency ventilation (p < .01). This improvement, along with decreased need for oxygen, was sustained through the subsequent course. Twenty-three (74%) of 31 children treated with high-frequency ventilation survived. Survivors showed an increase in an arterial pH, Pao2, Pao2/FIO2, and a decrease in Paco2 within 6 hrs, whereas nonsurvivors did not. Oxygenation index was the best predictor of outcome. A combination of an initial oxygenation index of > 20 and failure to decrease the oxygenation index by > 20% by 6 hrs after initiation of high-frequency ventilation predicted death with 88% (7/8) sensitivity and 83% (19/23) specificity, with an odds ratio of 33 (p = .0036, 95% confidence interval 3-365).

CONCLUSIONS

In patients with potentially reversible underlying diseases resulting in severe acute respiratory failure that is unresponsive to conventional ventilation, high-frequency ventilation improves gas exchange in a rapid and sustained fashion. The magnitude of impaired oxygenation and its improvement after high-frequency ventilation can predict outcome within 6 hrs.