Obesity
Conditions
Keywords
Obesity, Preoxygenation, High-Flow Nasal Oxygen, Airway Management
Brief 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.
Detailed description
Obesity is a growing global health issue, and obese patients have higher rates of difficult airway and faster desaturation during apnea due to reduced functional residual capacity, decreased lung compliance, and increased oxygen consumption. Traditional face mask preoxygenation (FiO₂ = 1.0) is widely used but often compromised by poor mask seal and patient intolerance. High-flow nasal cannula (HFNC) delivers heated, humidified high-flow oxygen, maintains airway pressure, and enables apneic oxygenation, potentially prolonging safe apnea time. However, evidence remains limited due to small sample sizes, inconsistent desaturation thresholds, and non-standardized flow protocols. This study aims to compare three preoxygenation strategies in obese patients. This is a prospective, randomized, open-label, three-arm parallel trial at a single center. Enrollment runs from July 2026 to May 2027. We plan to include 147 adults (18-65 years, ASA I-III, BMI ≥ 28) undergoing elective surgery with general anesthesia and tracheal intubation. Key exclusions are severe cardiac or pulmonary disease, pregnancy, current smoking, baseline SpO₂ \< 95%, severe nasal obstruction, known difficult airway, or recent trial participation. All patients fast routinely and receive standard monitoring plus radial artery cannulation. Preoxygenation lasts 3 minutes with mouth closed: FM group - face mask 15 L/min; HF45 - nasal high-flow 45 L/min; HF70 - nasal high-flow 70 L/min. Anesthesia is induced with propofol, sufentanil, and rocuronium (dosed by predicted body weight). After loss of consciousness, an oropharyngeal airway and jaw thrust maintain patency. On confirmed apnea, oxygen is stopped. Intubation is performed with video laryngoscope within 45-60 seconds. After tube placement, patients remain apneic with tube open to air until SpO₂ reaches 93%, when mechanical ventilation starts. The primary outcome is safe apnea time (seconds from apnea onset to SpO₂ = 93%). Secondary outcomes are arterial blood gases at multiple time points, VAS comfort score (0-10), tolerance rate, and hemodynamic variables (blood pressure, heart rate) at pre-induction, post-induction, and intubation. Sample size calculation: based on prior meta-analysis (mean difference \ 60 sec, SD \ 90 sec, effect size 0.67), with α = 0.05 (two-sided), power 0.80, and Bonferroni correction for two primary comparisons (α' = 0.025), \ 44 per group are needed. With 10% dropout, total 147 (49 per group). Statistical analysis uses independent t-tests or Mann-Whitney U with Bonferroni correction for continuous variables, and Fisher's exact or chi-square for categorical variables, with multiple comparison adjustments as appropriate. Data are recorded, double-entered, and verified. Equipment is calibrated regularly. The ethics committee approved the protocol. Written informed consent is obtained from all participants, who may withdraw anytime. Results will be published irrespective of outcome.
Interventions
DEVICEFace 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.
DEVICEHigh-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.
Sponsors
The First People's Hospital of Lianyungang
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
* Age 18 to 65 years * American Society of Anesthesiologists (ASA) physical status I \~ III * Scheduled for elective surgery under general anesthesia with endotracheal intubation * Body mass index (BMI) ≥ 28 kg/m² * Willing and able to provide written informed consent
Exclusion criteria
* Cardiac disease including ischemic heart disease, heart failure (New York Heart Association class ≥ 2), current arrhythmia, or pulmonary hypertension * Severe asthma or moderate to severe chronic obstructive pulmonary disease * Pregnancy * Current smoker or former smoker who quit less than 1 year prior to enrollment * Baseline peripheral oxygen saturation (SpO₂) \< 95% * Severe nasal obstructive disease that affects nasal ventilation or intubation * Known or anticipated difficult airway * Participation in another interventional clinical trial within 30 days prior to enrollment
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Arterial Blood Gas Measurements During Preoxygenation and Apnea | From baseline (before preoxygenation) to apnea termination (first SpO2 decrease to 93% or ventilation resumption), assessed up to approximately 13 min (780 sec; preoxygenation up to 3 min + apnea up to 10 min). | Arterial blood gases are measured at the following time points: (1) at baseline (before preoxygenation), (2) during preoxygenation (at 1 minute and 2 minutes and 3 minutes), (3) immediately at the onset of apnea, (4) during apnea (at 1-minute intervals), and (5) immediately at termination of apnea when SpO₂ reaches 93%. Parameters measured include PaO₂, PaCO₂, pH, and other standard blood gas variables. |
| Preoxygenation Comfort Visual Analog Scale Score | Single assessment at 2.5 minutes after start of preoxygenation, during the 3-minute preoxygenation period. | Patient comfort during the 3-minute preoxygenation period is assessed using a visual analog scale (VAS) ranging from 0 to 10, where 0 represents no discomfort and 10 represents extreme discomfort. Patients are asked to indicate their score using a finger marker at approximately 2.5 minutes after the start of preoxygenation. |
| Preoxygenation Tolerance Rate | From start of preoxygenation to end of preoxygenation, assessed up to 3 minutes. | Preoxygenation tolerance rate is defined as the proportion of patients who complete the full 3-minute preoxygenation period without refusal or requiring adjustment of the intervention. Patients who discontinue or request modification of the preoxygenation method during the 3-minute period are recorded as intolerance events. |
| Systolic blood pressure (SBP) | Baseline (before induction), immediately after induction, and immediately after intubation; assessed up to immediately after intubation. | Systolic blood pressure measured by invasive radial artery monitoring at three time points: (1) baseline before anesthesia induction; (2) immediately after induction (after loss of consciousness following propofol and sufentanil); and (3) immediately after endotracheal intubation. |
| Diastolic blood pressure (DBP) | Baseline (before induction), immediately after induction, and immediately after intubation; assessed up to immediately after intubation. | Diastolic blood pressure measured by invasive radial artery monitoring at three time points: (1) baseline before anesthesia induction; (2) immediately after induction (after loss of consciousness following propofol and sufentanil); and (3) immediately after endotracheal intubation. |
| Mean arterial pressure (MAP) | Baseline (before induction), immediately after induction, and immediately after intubation; assessed up to immediately after intubation. | Mean arterial pressure measured by invasive radial artery monitoring at three time points: (1) baseline before anesthesia induction; (2) immediately after induction (after loss of consciousness following propofol and sufentanil); and (3) immediately after endotracheal intubation. |
| Heart rate (HR) | Baseline (before induction), immediately after induction, and immediately after intubation; assessed up to immediately after intubation. | Heart rate measured by invasive radial artery monitoring at three time points: (1) baseline before anesthesia induction; (2) immediately after induction (after loss of consciousness following propofol and sufentanil); and (3) immediately after endotracheal intubation. |
Countries
China
Contacts
CONTACTXiaobao Zhang
Outcome results
None listed