The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Elizabeth Rohrs, Jason Zurba; Respiratory Therapy, Royal Columbian Hospital, New Westminster, BC, Canada

High frequency Oscillatory ventilation (HFOV) has been heralded as the ideal lung protective ventilation strategy. It theoretically limits baro/volutrauma using sub-deadspace tidal volumes and limits atelectrauma using higher mean airway pressures. Unfortunately small randomized controlled trials have not shown an improvement in survival rates, and may show an increase the risk of intra-ventricular haemorrhage in neonatal patients. One plausible explanation for the lack of mortality benefit is the lack of direct control over tidal volume, where much of the theoretical lung protection may be lost because the assumed sub-deadspace tidal volumes may approach conventional ventilating volumes at higher HFOV settings. This lack of tidal volume control also translates into a lack of precise control of carbon dioxide (CO2) removal resulting in fluctuating arterial CO2 levels, along with an inability to predict the magnitude of CO2 changes due to ventilator setting changes. Case Summary We describe a case of a 26 week gestation baby with bronchopulmonary displasia ventilated on high frequency oscillation with volume guarantee (VG) in our neonatal intensive care. The CO2 variance during the period of HFOV with no VG was 237.80, with a mean of 77.40. This was compared to a variance of 78.00 and a mean of 64.69 for the period when VG was active. The higher CO2 variance before VG was activated showed two episodes of hypercapnia, putting the patient at risk for PVL and IVH Discussion HFOV + VG allows for control of high frequency tidal volume independently of hertz and amplitude, allowing the return of autonomy of rate control to the hertz setting. Changes in hertz no longer cause an over-estimation or under-estimation in ventilating volume that would impact CO2 removal, resulting in serious long term consequences. This brings the ventilation strategy in high-frequency in line with conventional ventilation strategy and eliminates some of the ‘guess work’ out of the process. Using VG required a change in our high frequency oscillation protocol and strategy. Overall the team felt that they had better control over ventilation and were better able to mitigate the sequelae of hypocapnea and hypercapnea. Sponsored Research - None