Effect of Different-Flow High-Flow Nasal Cannula Versus Traditional Face Mask Oxygenation on Safe Apnea Time in Obese Patients

Condition(s) studied

Investigational drug(s) / intervention(s)

Face Mask: Face mask preoxygenation delivered via a tight-fitting mask (appropriate size selected based on facial dimensions) with oxygen flow at 15 L/min, FiO₂ = 1.0 (100% oxygen), for 3 minutes during tidal breathing.

High-Flow Nasal Cannula: High-flow nasal oxygen delivered via a dedicated nasal cannula (size selected based on nostril size), with FiO₂ = 1.0 (100% oxygen), gas heated and humidified (37°C, 100% relative humidity), for 3 minutes with mouth closed and nasal breathing. Flow rates are 45 L/min for the HF45 group and 70 L/min for the HF70 group.

Study summary

Obesity is a growing global health problem, and patients with obesity are at higher risk of hypoxemia during induction of general anesthesia. This is because excess body weight reduces the lungs' oxygen storage capacity, causing blood oxygen saturation to decline faster than in normal-weight individuals once breathing stops. Currently, the most common preventive method is preoxygenation with a face mask delivering 100% oxygen for several minutes before anesthesia induction. However, face masks often fail to seal properly in obese patients, potentially compromising preoxygenation effectiveness.

High-flow nasal oxygen therapy is a newer technique that delivers heated and humidified oxygen at high flow rates through nasal cannulae. It not only provides effective preoxygenation but may also continue to supply oxygen during apnea (apneic oxygenation), thereby prolonging the safe apnea time. Nevertheless, it remains unclear which flow rate is most effective and whether high-flow nasal oxygen is truly superior to conventional face masks.

This prospective randomized controlled trial will enroll 147 obese patients (BMI ≥ 28kg/m²) scheduled for elective surgery at Lianyungang First People's Hospital. Participants will be randomly assigned to one of three groups: (1) traditional face mask preoxygenation at 15 L/min, (2) high-flow nasal oxygen at 45 L/min, or (3) high-flow nasal oxygen at 70 L/min. All patients will receive 100% oxygen for 3 minutes. The primary outcome is safe apnea time - the duration from cessation of breathing until SpO₂ drops to 93%. Secondary outcomes include arterial blood gas values, patient comfort during preoxygenation, tolerance rate, and hemodynamic stability.

The study hypothesis is that high-flow nasal oxygen at 70 L/min will provide a longer safe apnea time than both traditional face mask preoxygenation and high-flow nasal oxygen at 45 L/min in obese patients. The results will provide high-quality evidence for optimizing perioperative preoxygenation strategies in this population.

Eligibility

Primary outcome measure(s)

• Safe Apnea Time — From apnea onset to first SpO2 decrease to 93%, assessed up to 10 minutes (600 seconds) after apnea onset; censored if ventilation resumes before SpO2 reaches 93%.
  Safe apnea time is defined as the duration from the onset of apnea (cessation of ventilation after complete neuromuscular blockade following rocuronium administration) to the first decline of peripheral oxygen saturation (SpO₂) to 93%, measured in seconds. Apnea is confirmed by visual assessment by a study team member. Oxygen delivery is discontinued upon confirmation of apnea. The patient remains apneic with the endotracheal tube open to atmosphere until the SpO₂ threshold is reached, at which point mechanical ventilation is initiated and the apnea period is terminated.

Trial sites (1)

More The First People's Hospital of Lianyungang trials in China

Other trials for the same condition