An interventional study of Heated and Humidified Oxygen Therapy and Room-Temperature Oxygen Therapy in Hypoxemia, Postoperative Complications and Anesthesia Recovery Period, sponsored by Second Affiliated Hospital of Xi'an Jiaotong University. Not yet recruiting at 8 sites in China. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-01.
Sponsored by Second Affiliated Hospital of Xi'an Jiaotong University · Not applicable, Interventional, and Prevention
This study aims to determine whether heated and humidified oxygen therapy, compared with conventional room-temperature oxygen therapy, reduces the incidence of early hypoxemia in adult patients recovering from general anesthesia in the Post-Anesthesia Care Unit (PACU).
Hypoxemia is a common and potentially life-threatening complication during PACU recovery, resulting from residual anesthetics, decreased upper airway muscle tone, atelectasis, and suppression of hypoxic pulmonary vasoconstriction (HPV). Heated and humidified oxygen may offer benefits by preserving optimal HPV function, protecting airway mucosa, and reducing respiratory resistance.
This is a prospective, multicenter, randomized, superiority trial with a parallel-group design. A total of 2,000 adult patients (ASA class I-III) undergoing general anesthesia will be enrolled and randomly assigned in a 1:1 ratio to receive either heated and humidified oxygen (37°C, 5 L/min via face mask) or room-temperature oxygen (room temperature, 5 L/min via face mask).
The primary outcome is the incidence of hypoxemia, defined as SpO₂ ≤ 90% lasting ≥ 5 seconds, within 10 minutes after initiation of the intervention. Secondary outcomes include severe hypoxemia (SpO₂ ≤ 85%), requirement for airway interventions, lowest SpO₂ value, PACU length of stay, postoperative shivering, and agitation. Safety outcomes include nasal discomfort, epistaxis, and device-related adverse events.
BACKGROUND Hypoxemia is one of the most common and potentially life-threatening complications in the Post-Anesthesia Care Unit (PACU) during recovery from general anesthesia. Patients are particularly vulnerable due to residual anesthetic effects, diminished upper airway muscle tone, atelectasis, and suppression of hypoxic pulmonary vasoconstriction (HPV). Hypoxemia can precipitate arrhythmias, hemodynamic instability, prolonged PACU stay, increased unplanned ICU admissions, and in severe cases, cardiac arrest or hypoxic brain injury. Accordingly, optimizing respiratory management strategies in the PACU to prevent hypoxemia is of considerable clinical importance.
Heated and humidified oxygen therapy delivers inhaled gas at near-core body temperature (37°C) with adequate humidification. The theoretical rationale includes: (1) maintaining optimal HPV function, as hypothermia inhibits HPV and exacerbates intrapulmonary shunting; (2) preserving airway mucociliary clearance and preventing secretion retention; (3) reducing respiratory resistance by minimizing airway irritation; and (4) supporting core temperature maintenance to stabilize cardiopulmonary function.
This study is the first to systematically apply heated and humidified oxygen therapy in a prospective, standardized manner during the immediate short-term recovery period in the PACU, specifically to evaluate its preventive effect on early hypoxemia. The large sample size (2,000 patients) will provide sufficient statistical power for prespecified subgroup analyses.
STUDY DESIGN This is a prospective, multicenter, randomized, superiority trial with a parallel-group design (1:1 allocation ratio). Patient blinding is achieved through a sham-device design: all patients are connected to identical heating devices and circuits, with the device switched off in the control group. Outcome assessors and statistical analysts remain blinded to group allocation.
SAMPLE SIZE Based on an estimated control group hypoxemia rate of 8.0% and an expected 50% relative reduction in the experimental group (4.0%), with α = 0.05 (two-sided), power = 90%, and accounting for approximately 10% dropout, the calculated sample size was 1,752. This was expanded to 2,000 patients (1,000 per group) to enhance subgroup analysis power and overall evidence quality, achieving >95% power for the primary analysis.
INTERVENTIONS All patients receive oxygen at 5 L/min via face mask with the head of the bed elevated to 30°. Experimental group: oxygen heated to 36-37°C using a dry-heat blood/fluid warmer with a flexible heating sleeve, with temperature measured every 5 minutes. Control group: same device but switched off (sham), with simulated temperature measurements recorded as room temperature.
OUTCOME MEASURES Primary outcome: incidence of hypoxemia (SpO₂ ≤ 90% for ≥ 5 seconds) within 10 minutes of intervention initiation.
Secondary outcomes: severe hypoxemia (SpO₂ ≤ 85%), need for airway interventions, lowest SpO₂ value, SpO₂ drop >4%, PACU length of stay, postoperative shivering, and agitation.
Safety outcomes: nasal discomfort, epistaxis, device-related adverse events, and hemodynamic instability.
STATISTICAL ANALYSIS Primary analysis will be performed on the intention-to-treat (ITT) population using Poisson regression with robust error variance, adjusting for study center, to calculate relative risk (RR) and 95% confidence intervals. Subgroup analyses are prespecified for age, sex, BMI, smoking status, ASA class, surgery type, Mallampati class, and intraoperative opioid use. Interim analyses are planned at 25%, 50%, and 75% enrollment, reviewed by an independent Data Safety Monitoring Board (DSMB) using O'Brien-Fleming boundaries to control type I error.
DATA MONITORING An independent Data Safety Monitoring Board (DSMB) will review unblinded data at each interim analysis. All serious adverse events will be reported to the Principal Investigator within 24 hours. The study has received ethical approval from the Medical Ethics Committee of the Second Affiliated Hospital of Xi'an Jiaotong University .
1,076 studies on the registry are indexed under Hypoxia; 213 are open to participants now.
This study's planned enrollment of 2,000 is above the median of 45 across 769 interventional studies indexed under Hypoxia.
Browse Hypoxia studies →Second Affiliated Hospital of Xi'an Jiaotong University is the lead sponsor of 70 studies on the registry; 16 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients receive oxygen heated to 36-37°C at 5 L/min via face mask using a dry-heat blood/fluid warmer with a flexible heating sleeve. Temperature is measured every 5 minutes to ensure stability within the target range.
Device: Heated and Humidified Oxygen Therapy
Patients receive room-temperature oxygen at 5 L/min via face mask through a bubble humidifier. The same heating device is connected but switched off (sham) to maintain patient blinding. Simulated temperature measurements are recorded as room temperature.
Device: Room-Temperature Oxygen Therapy
Oxygen heated to 36-37°C using a dry-heat blood/fluid warmer with a flexible heating sleeve, delivered at 5 L/min via face mask. Temperature measured every 5 minutes.
Room-temperature oxygen delivered at 5 L/min via face mask through a bubble humidifier. Same heating device but switched off (sham), with simulated temperature measurements recorded as room temperature.
Incidence of Hypoxemia Within 10 Minutes
Hypoxemia is defined as SpO₂ ≤ 90% lasting for ≥ 5 seconds during the 10-minute period immediately after initiation of the study intervention. Only events occurring during normal waveform quality are counted.
Time frame: Within 10 minutes after intervention initiation
Incidence of Severe Hypoxemia
Severe hypoxemia is defined as SpO₂ ≤ 85% lasting for ≥ 5 seconds within 10 minutes of intervention initiation.
Time frame: Within 10 minutes after intervention initiation
Lowest SpO₂ Value
The lowest SpO₂ value recorded during the 10-minute period after intervention initiation, based on continuous monitoring.
Time frame: Within 10 minutes after intervention initiation
Significant SpO₂ Drop >4% From Baseline
Proportion of patients with a decline in SpO₂ of more than 4% from baseline within 10 minutes of intervention initiation.
Time frame: Within 10 minutes after intervention initiation
Need for Airway Interventions
Proportion of patients requiring jaw thrust, increase in oxygen flow rate (\>5 L/min), or bag-mask ventilation during the entire PACU stay.
Time frame: From enrollment to PACU discharge, up to 6 hours
PACU Length of Stay
Time from PACU admission until meeting discharge criteria (modified Aldrete score ≥ 9).
Time frame: From enrollment to PACU discharge, up to 6 hours
Incidence of Postoperative Shivering
Proportion of patients experiencing objective shivering during the entire PACU stay.
Time frame: From enrollment to PACU discharge, up to 6 hours
Incidence of Postoperative Agitation
Proportion of patients with Riker Sedation-Agitation Scale score ≥ 5 during the entire PACU stay.
Time frame: From enrollment to PACU discharge, up to 6 hours
Device-Related Adverse Events
Incidence of nasal discomfort, epistaxis, condensed water aspiration, device overheating/alarm malfunction, and hemodynamic instability events during the PACU stay.
Time frame: From enrollment to PACU discharge, up to 6 hours
Plan to share: No
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Second Affiliated Hospital of Xi'an Jiaotong University