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Transnasal humidified rapid insufflation ventilatory exchange versus standard facemask for preoxygenation in pregnant patients: a prospective, randomized, non-inferiority trial
Abstract Number: F3B-2
Abstract Type: Original Research
Transnasal humidified rapid insufflation ventilatory exchange (THRIVE) has been shown to provide effective preoxygenation and prolong apneic time during intubation attempts in non-pregnant patients.[1,2] These characteristics are beneficial in parturients undergoing general anesthesia. We hypothesized that in parturients, THRIVE preoxygenation would achieve similar mean end-tidal oxygen concentration (EtO2) after 3 min of tidal volume (TV) breathing compared to standard tight-fitting facemask.
With ethics approval and informed consent, 40 healthy, term, non-laboring parturients were randomized 1:1 to preoxygenation with 100% oxygen (O2) via Optiflow™ THRIVE or facemask (control). All patients were placed in a ramped position with left uterine displacement. Baseline values were recorded after 30s of TV breathing of 21% O2 at 12L/min. THRIVE patients continued TV breathing of 100% O2 with THRIVE applied at 30L/min and increased gradually to 70L/min over 30s; control patients continued TV breathing of 100% O2 at 15L/min via facemask. After 3 min we recorded EtO2. Following an additional 5 min O2 washout period on room air, both groups repeated 30s TV breathing and then 8 vital capacity (VC) breaths. The primary outcome was EtO2 after 3 min of TV breathing and analyzed using a non-inferiority analysis with a non-inferiority margin of 10%. Secondary outcomes were EtO2 with VC breathing and patient satisfaction.
After 3 min TV breathing (Fig 1), the EtO2 means (SD) were THRIVE 87.4% (7.0%), control 91% (5.0%); mean difference (MD) 3.7% (95% CI: -0.5, 7.8). After 8 VC breaths, the EtO2 means (SD) were THRIVE 85.9% (5.3%), control 91.8% (3.4%); MD 5.9% (95% CI: 2.8, 8.9). Both TV and VC EtO2 were within the non-inferiority margins. The mean (SD) durations for VC breathing were THRIVE 1.44 min (0.31), control 1.63 min (0.45). Comfort and acceptability were not significantly different.
We conclude that THRIVE preoxygenation is non-inferior to standard tight-fitting facemask in achieving similar EtO2 in healthy parturients after 3 min TV breathing and 8 VC breaths. In addition, THRIVE was well tolerated, even at 70L/min. This study was conducted under ideal conditions. The impact of THRIVE in non-ideal conditions (e.g. high body mass index or emergencies) and its ability to provide apneic oxygenation in obstetric patients warrant further study.
1. Patel A et al. Anaesthesia 2015
2. Mir F et al. Anaesthesia 2017