The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Craig D. Smallwood1, Camille Gomez-Laberge2,3, Gerhard K. Wolf2,3, John H. Arnold2,3; 1Respiratory Care, Boston Children’s Hospital, Boston, MA; 2Critical Care, Perioperative and Pain Medicine, Boston Children’s Hospital, Boston, MA; 3Harvard Medical School, Boston, MA

INTRODUCTION: Apart from enhanced patient-ventilator synchrony, the specific mechanisms by which neurally adjusted ventilatory assist (NAVA) may benefit subjects who are breathing spontaneously is poorly understood. This study was conducted in order to compare the regional distribution of ventilation differences between NAVA and pressure support ventilation (PSV). METHODS: A randomized cross-over design was implemented during which patients received 4 hours of PSV and 4 hours of NAVA. CO2 elimination (VCO2) and oxygen consumption (VO2) were recorded. Regional distribution of ventilation was recorded by electrical impedance tomography (EIT) using a 16 electrode belt. The belt was connected to the EIT Evaluation Kit 2 (Drager Medical, Lubeck, Germany). Data was recorded and later analyzed offline using EIT Data Review software (V5.1, Drager Medical, Lubeck, Germany) and SPSS statistical software. The lung region was divided into 4 equally sized regions of interest (ROI) along the ventral-dorsal axis. A repeated measures ANOVA utilizing Bonferroni corrected paired T-Tests was used to compare the proportions of ventilation in each ROI between NAVA and PSV and overall in order to compare homogeneity. RESULTS: Three patients with a mean age (± SD) of 11.2 ± 6.8 years were enrolled in the study. All subjects completed the investigation. VCO2 was similar between NAVA and PSV. Although not reaching significance, VO2 was lower during NAVA (184.1 ± 86.0 vs. 212.5 ± 105.5 ml/min). Statistically significant increases in ventilation in ROI 1 and 4, with decreases in ROI 2 and 3 were observed during NAVA (see Table.). Overall distribution of ventilation was more homogenous during NAVA (P < 0.001). The image is a reconstruction of tidal breath impedance changes during PSV and NAVA for subject 1 along the transverse plane of the caudal lung region and shows a homogenous distribution of ventilation during NAVA. CONCLUSIONS: In these critically ill children, we observed an increase in ventilation in the most ventral and dorsal lung regions during NAVA and a more homogenous distribution of ventilation compared to PSV. Although not statistically significant, a modest decrease in oxygen consumption during NAVA was observed and could represent reduced oxygen cost of breathing. Because the number of patients reported in this investigation is small, further research is necessary to validate these findings. Sponsored Research - A portion of this research was funded by an unrestricted research grant from Maquet Critical Care.