High Frequency Oscillation Ventilation in the Treatment of Paediatric Acute Hypoxaemic Res-piratory Failure - Analysis of the Years 1994 - 1998

Summary

Objective:
There were two objectives of the submitted investigation: 1. To demonstrate the effect of highfrequency oscillation on the gas exchange in children with severe respiratory failure (ARDS) where conventionalmechanical ventilation had failed. 2. To attempt identification of patients where failure of high frequencyoscillation is very probable and thus there is a great risk of death.Type of study: Retrospective analysis of a group. Site: ARO and ECMO Centre of the Children™s HospitalBrno.Patients: 26 patients above 1 month of age with severe hypoxaemic respiratory failure and ARDS. Mean age3.66 years (three adults - 17, 19 and 24 years), maximum body weight 70 kg, 17 boys, 9 girls. Fifteen patients died,84.6% patients suffered from some internal disease, mean PRISM score on admission 22. Nine patients met theECMO criteria, in two ECMO was not necessary, in another five patients ECMO was contraindicated, two patientswere connected with ECMO. To four patients during HFO iNO was administered, in two moreover partial liquidventilation was used.Method: The patients were connected to a PCV or PRVC regime with a limited peak pressure and permissivehypercapnia. If PaCO2 > 10.0 kPa and/or pH < 7.20 was recorded, continuous tracheal gas insufflation was used.When FiO2 > 0.6 and Paw > 15 cm H2O for peripheral blood saturation to a minimum of 90% had to be used orin case of persisting hypercapnia and/or acidosis in CMV with TGI the patients were switched to HFO. The HFOstrategy was —High Volume Strategyii - recruitment of alveoli and achievement of the optimal pulmonary volume.For switching back to CMV the patient had to meet the following criteria: Paw 15 - 20 cm H2O, FiO2 < 0.6 withoutan air leak and/or improvement of the X-ray finding without desaturation during aspiration of the airways. Thepatient was considered detached if he met the following criteria: saturation > 90%, FiO2 < 0.4, Paw < 15 cm H2O,normal pH at a respiration rate (RR) < 30/min. and PIP < 35 cm H2O. In addition to demographic data (sex, age,body weight, PRISM score on admission) and period of ventilation (CMV before HFO, HFO, CMV after HFOand total ventilation period) the following were assessed: pH, PaO2, PaCO2, AaDO2, oxygenation index andhypoxaemic score (PaO2/FiO2).Results: Within several hours the oxygenation improved, CO2 was eliminated and the ventilation-perfusionstate returned to normal in all patients. This improvement was permanent. Between surviving and not survivingpatients there are significant differences in the investigated parameters, moreover there were marked differencesin the CMV before HFO. 42% patients survived. If the PaO2/FiO2 increases by 55% during the sixth hour of HFOit may be assumed with a 83% sensitivity and 92% specificity that the patient will survive. When OI declines by30% during the 6th hour of HFO the prediction of survival is with a 86% sensitivity and 82% specificity.Conclusion: HFO was effective in all patients where CMV failed, CO2 elimination and oxygenation improved,42% patients survived. It is possible that early HFO administration can reduce the mortality of acute hypoxaemicrespiratory failure in children.

Key words:
high frequency oscillation (HFO), respiratory failure, children, conventional mechanical ventilation