Carbon Dioxide Changes during High-flow Nasal Oxygenation in Apneic Patients: A Single-center Randomized Controlled Noninferiority Trial

Abstract

Background Anesthesia studies using high-flow, humidified, heated oxygen delivered via nasal cannulas at flow rates of more than 50 l · min–1 postulated a ventilatory effect because carbon dioxide increased at lower levels as reported earlier. This study investigated the increase of arterial partial pressure of carbon dioxide between different flow rates of 100% oxygen in elective anesthetized and paralyzed surgical adults before intubation. Methods After preoxygenation and standardized anesthesia induction with nondepolarizing neuromuscular blockade, all patients received 100% oxygen (via high-flow nasal oxygenation system or circuit of the anesthesia machine), and continuous jaw thrust/laryngoscopy was applied throughout the 15-min period. In this single-center noninferiority trial, 25 patients each, were randomized to five groups: (1) minimal flow: 0.25 l · min–1, endotracheal tube; (2) low flow: 2 l · min–1, continuous jaw thrust; (3) medium flow: 10 l · min–1, continuous jaw thrust; (4) high flow: 70 l · min–1, continuous jaw thrust; and (5) control: 70 l · min–1, continuous laryngoscopy. Immediately after anesthesia induction, the 15-min apnea period started with oxygen delivered according to the randomized flow rate. Serial arterial blood gas analyses were drawn every 2 min. The study was terminated if either oxygen saturation measured by pulse oximetry was less than 92%, transcutaneous carbon dioxide was greater than 100 mmHg, pH was less than 7.1, potassium level was greater than 6 mmol · l–1, or apnea time was 15 min. The primary outcome was the linear rate of mean increase of arterial carbon dioxide during the 15-min apnea period computed from linear regressions. Results In total, 125 patients completed the study. Noninferiority with a predefined noninferiority margin of 0.3 mmHg · min–1 could be declared for all treatments with the following mean and 95% CI for the mean differences in the linear rate of arterial partial pressure of carbon dioxide with associated P values regarding noninferiority: high flow versus control, –0.0 mmHg · min–1 (–0.3, 0.3 mmHg · min–1, P = 0.030); medium flow versus control, –0.1 mmHg · min–1 (–0.4, 0.2 mmHg · min–1, P = 0.002); low flow versus control, –0.1 mmHg · min–1 (–0.4, 0.2 mmHg · min–1, P = 0.003); and minimal flow versus control, –0.1 mmHg · min–1 (–0.4, 0.2 mmHg · min–1, P = 0.004). Conclusions Widely differing flow rates of humidified 100% oxygen during apnea resulted in comparable increases of arterial partial pressure of carbon dioxide, which does not support an additional ventilatory effect of high-flow nasal oxygenation. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Noninvasive ventilation in children: A review for the pediatric anesthesiologist

“…Since then, the application of HFNO in adults and children during anesthesia is referred to as transnasal humidified rapid‐insufflation ventilatory exchange (THRIVE). The alleged ventilatory effect of THRIVE is absent in both apneic adults 28 and children 29,30 . The use of the acronym THRIVE should be abandoned in favor of HFNO.…”

Apneic oxygenation in pediatric anesthesia

“…In adults, the use of HFNO in apneic patients was called ‘THRIVE’ (Transnasal Humidified Rapid Insufflation Ventilatory Exchange) [6], implying that HFNO supports the elimination of carbon dioxide (CO 2 ). Studies in children did not show such a ventilatory effect during apneic oxygenation [7 ▪ ,8,9 ▪▪ ,10]. Therefore, we stay with the original term HFNO.…”

Can We Finally Take the “VE” Out of THRIVE?

“…As noted in the study by Riva et al, despite the demonstrated lack of a ventilatory component, high-flow nasal oxygenation in combination with a patent airway is an effective means of providing apneic oxygenation in the operating room during preoxygenation, induction of anesthesia, intubation, and awake flexible optic intubation, as well as for other purposes. 9 What implications might the study by Riva et al have in the context of high-flow nasal oxygenation in the intensive care unit? A joint panel of experts from the European Society of Intensive Care Medicine conducted systematic reviews of the literature to synthesize an evidence-based clinical practice guideline that was released in November 2020.…”

“…Their study and the studies of high-flow nasal oxygen in children suggest we can finally take the "V ̇e" (which is generally equated with carbon dioxide clearance) out of THRIVE. 7,9,10 The main limitation of the study is its generalizability-with its single-center design and extensive exclusion criteria, how applicable is it to the more general (i.e., less healthy) adult surgical population that we commonly encounter? On the other hand, how feasible is a prospective, randomized, controlled, five-armed, multicenter study that may result in as many as 15 min of apnea in higher-risk patients (e.g., those with known coronary heart disease or body mass index greater than 35 kg/m 2 )?…”

“…The authors' interpretation of their results, along with refuting earlier studies' claims of ventilatory exchange in THRIVE, are attributed to sole use of end-tidal carbon dioxide concentration sampling and use of historical controls from much earlier studies. 6,9 While the focus of the study by Riva et al was carbon dioxide clearance, the oxygenation findings are noteworthy. A patent airway and preoxygenation to an end-tidal oxygen concentration greater than 90% are remarkably effective in a healthy adult: only 6 of 125 patients (5%) met the oxygen desaturation termination criterion during the 15-min period of apnea.…”