Physiological effects of trans-nasal humidified rapid insufflation ventilatory exchange (THRIVE) on lung volume dynamics during controlled apnea in patients with obesity: a randomized controlled trial.
BACKGROUND Obese patients are prone to rapid oxygen desaturation during induction of general anesthesia due to reduced functional residual capacity and atelectasis formation. Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) prolongs safe apnea time; however, its effects on lung volume dynamics during apnea remain unclear. METHODS In this single-center randomized controlled trial, adults with body mass index ≥35 kg/m2 undergoing elective surgery were assigned to apneic oxygenation with THRIVE or facemask oxygen following induction of general anesthesia. Electrical impedance tomography was used to assess changes in end-expiratory lung impedance (ΔEELI), a surrogate of lung volume. The primary outcome was mean global ΔEELI during an early apneic window (2-6 min). RESULTS Thirty-two patients were analyzed. Mean global ΔEELI during early apnea was significantly better preserved with THRIVE than with facemask oxygen (-0.22 ± 0.03 vs. -0.89 ± 0.07; mean difference 0.67, 95% CI 0.55-0.80; P < 0.001). THRIVE attenuated the rate of ΔEELI decline and was associated with greater preservation of lung volume, particularly in mid-ventral and mid-dorsal regions. Safe apnea time was significantly prolonged in the THRIVE group (median 600 vs. 319 s). CONCLUSIONS In obese patients, THRIVE transiently preserves lung volume during early apnea by slowing the decline in end-expiratory lung volume. These findings provide physiological insight into the mechanisms underlying improved oxygenation during apneic oxygenation.