Transnasal Microstream EtCO2 Reduces Hypoxemia During Emergence in Aged Post-Abdomen Surgery

Effect of Transnasal Microstream Capnography on Incidence of Hypoxemia During Emergence From General Anesthesia in Elderly Patients After Abdominal Surgery: A Prospective Randomised Controlled Trial

This prospective, randomized controlled study aims to investigate whether transnasal microstream end-tidal carbon dioxide (EtCO₂) monitoring in the post-anesthesia care unit (PACU) reduces the incidence of postoperative hypoxemia in elderly patients (65-80 years, ASA I-III, BMI 18-30 kg/m²) undergoing elective laparoscopic surgery under general anesthesia with endotracheal intubation. A total of 324 patients will be randomized 1:1 to either the control group (standard SpO₂ monitoring and clinical observation with oxygen delivery at 2 L/min via sampling line) or the experimental group (same oxygen delivery plus continuous real-time transnasal microstream EtCO₂ monitoring). The primary outcome is the incidence of hypoxemia (SpO₂ < 90% for >15 seconds) after extubation in the PACU. Secondary outcomes include severe hypoxemia (SpO₂ < 85%), lowest SpO₂ during PACU stay, vital signs at specified time points, PACU length of stay, and other adverse events. Statistical analysis will use chi-square or Fisher's exact test for the primary outcome, with a sample size calculated to detect a reduction in hypoxemia from 33% (control) to 18% (experimental group) (α=0.05, power=80%, plus 20% dropout).

Study Overview

• Status: Not yet recruiting
• Conditions: Laparoscopic Surgery; Elderly Patients; Capnography; Postoperative Hypoxemia
• Intervention / Treatment: Other: Routine Monitoring; Device: EtCO₂ Monitoring

Detailed Description

Study Title:

Effect of Transnasal Microstream End-Tidal Carbon Dioxide Monitoring on the Incidence of Postoperative Hypoxemia in Elderly Patients Undergoing Laparoscopic Surgery under General Anesthesia with Endotracheal Intubation: A Prospective, Randomized Controlled Study

Principal Investigator: Wu Jianbo Department: Anesthesiology and Perioperative Medicine

Background & Objective:

Postoperative hypoxemia is a common respiratory complication in the post-anesthesia care unit (PACU). Conventional pulse oximetry (SpO₂) has a delayed response to hypoventilation, especially during supplemental oxygen therapy. This study aims to investigate whether adding transnasal microstream end-tidal carbon dioxide (EtCO₂) monitoring in the PACU reduces the incidence of hypoxemia in elderly patients after laparoscopic surgery under general anesthesia.

Study Design:

Prospective, randomized, controlled, interventional study.

Participants:

324 elderly patients (age 65-80 years, ASA I-III, BMI 18-30 kg/m²) scheduled for elective laparoscopic surgery under general anesthesia with endotracheal intubation.

Interventions:

Control group (n=162): Routine monitoring with SpO₂ and clinical observation; oxygen delivery at 2 L/min via sampling line without EtCO₂ monitoring.

Experimental group (n=162): Same oxygen delivery plus continuous real-time transnasal microstream EtCO₂ monitoring.

Primary Outcome:

Incidence of postoperative hypoxemia (SpO₂ < 90% for >15 seconds) after extubation in the PACU.

Secondary Outcomes:

Incidence of severe hypoxemia (SpO₂ < 85% for >15 seconds) Lowest SpO₂ during PACU stay Vital signs at predefined time points

PACU length of stay (Steward Recovery Score ≥ 4)

Other adverse events (e.g., nausea, vomiting, agitation, shivering)

Safety Monitoring:

Device-related adverse events (nasal irritation, bleeding), respiratory events (bradypnea, apnea, airway obstruction), and serious adverse events (e.g., need for advanced airway, cardiovascular events) will be recorded and managed according to a stepwise intervention protocol.

Randomization and Blinding:

1:1 randomization using block randomization (SAS 9.4) with allocation concealment (sealed, opaque envelopes). Partial blinding: participants, outcome assessors, and statisticians blinded; anesthesiologists/operators unblinded.

Sample Size Calculation:

Based on pilot data (expected hypoxemia rate: 33% in control vs. 18% in experimental group), α=0.05, power=80%, plus 20% dropout → 162 patients per group (total N=324).

Statistical Analysis:

SPSS 22.0 will be used. Continuous variables (normal distribution) will be compared using t-test; non-normally distributed variables using Mann-Whitney U test. Categorical variables (e.g., hypoxemia incidence) will be compared using chi-square or Fisher's exact test.

Expected Significance:

This study will provide high-level evidence on whether transnasal microstream EtCO₂ monitoring in the PACU can enhance respiratory safety in elderly patients recovering from laparoscopic surgery, potentially reducing hypoxemia and related complications.

• Study Type: Interventional
• Enrollment (Estimated): 324
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jianbo WU; Phone Number: 18560083793; Email: jianbowu@sdu.edu.cn

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 65-80 years;
• ASA physical status I-III;
• BMI 18-30 kg/m²;
• Participants scheduled for elective laparoscopic surgery under general anesthesia with endotracheal intubation;
• Willing to participate in the study and provide written informed consent

Exclusion Criteria:

• Patients with nasal bleeding, nasal mucosal injury, nasal cavity occupancy, or other conditions that preclude transnasal carbon dioxide monitoring;
• Patients undergoing emergency surgery;
• Participants requiring postoperative assisted ventilation via endotracheal intubation or tracheostomy;
• Presence of any disease or condition that may cause abnormal end-tidal carbon dioxide waveforms or abnormal baseline pulse oximetry (e.g., congenital heart disease or chronic lung disease);
• Severe cardiac insufficiency (≤4 Metabolic Equivalents [MetS]);
• Severe renal insufficiency (acute kidney injury [AKI] or chronic kidney disease [CKD] stage 4 or higher);
• Severe hepatic insufficiency (Child-Pugh class C or worse);
• Allergy to study medications;
• Daily alcohol intake ≥60 grams;
• History of psychiatric disorders such as depression, severe central nervous system depression, Parkinson's disease, basal ganglion lesions, schizophrenia, epilepsy, Alzheimer's disease;
• Participation in another related clinical study within the past 3 months.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Control Group (Routine Monitoring Group); After endotracheal extubation, the sampling end of the sampling line is placed between the patient's mouth and nose, and oxygen is delivered at 2 L/min via the sampling line. The patient receives only routine monitoring (including continuous pulse oximetry and clinical observation) and is not connected to the end-tidal carbon dioxide (EtCO₂) monitoring device.	Other: Routine Monitoring; After extubation, the sampling line is placed between the patient's mouth and nose to deliver oxygen at 2 L/min. The patient receives routine monitoring including continuous pulse oximetry (SpO₂) and clinical observation, but is not connected to the EtCO₂ monitoring device.
Experimental: Experimental Group (EtCO₂ Monitoring Group); After endotracheal extubation, the sampling end of the sampling line is placed between the patient's mouth and nose, and oxygen is delivered at 2 L/min via the sampling line. At the same time, the sampling line is connected to the monitor to initiate continuous real-time transnasal microstream end-tidal carbon dioxide monitoring.	Device: EtCO₂ Monitoring; After extubation, the sampling line is placed between the patient's mouth and nose to deliver oxygen at 2 L/min. The sampling line is connected to a patient monitor (RespArrayTM) to initiate continuous real-time transnasal microstream end-tidal carbon dioxide (EtCO₂) monitoring throughout the post-anesthesia care unit (PACU) stay.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of post-extubation hypoxemia (SpO₂ < 90% for >15 seconds)	Closely monitor vital signs, and record the number of episodes of hypoxemia (defined as SpO₂ < 90% lasting for >15 seconds) following tracheal extubation after the patient is transferred from the operating room to the PACU.more than 15 seconds	During the period in the post-anesthesia care unit (PACU) (up to 1 days)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of severe hypoxemia: proportion of patients with SpO₂ < 85% lasting > 15 seconds	Closely monitor the patient's vital signs, and record the proportion of patients with severe hypoxemia (SpO₂ < 85% lasting >15 seconds) following tracheal extubation after transfer from the operating room to the PACU	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
Lowest SpO₂ value during PACU stay Lowest SpO₂ value during PACU stay Lowest SpO₂ value during PACU stay	Observe and record the lowest SpO₂ value during the patient's stay in the PACU	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
PACU length of stay	time from entering the PACU until achieving a Steward recovery score >4, meeting the criteria for discharge	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
Other adverse events	Record adverse events occurring during the entire PACU stay	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
Record the changes in heart rate following the patient's admission to the PACU	Record the patient's heart rate at T0 (on PACU admission), T1 (1 min post-extubation), T2 (5 min post-extubation), T3 (10 min post-extubation), T4 (15 min post-extubation), T5 (20 min post-extubation), and T6 (on PACU discharge)	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
Record the patient's blood pressure after admission to the PACU	Record the patient's blood pressure values at T0 (on PACU admission), T1 (1 min post-extubation), T2 (5 min post-extubation), T3 (10 min post-extubation), T4 (15 min post-extubation), T5 (20 min post-extubation), and T6 (on PACU discharge)	During the period in the post-anesthesia care unit (PACU) (up to 1 days)
Record the changes in the patient's SpO₂ values after admission to the PACU	Record the patient's SpO₂ values at T0 (on PACU admission), T1 (1 min post-extubation), T2 (5 min post-extubation), T3 (10 min post-extubation), T4 (15 min post-extubation), T5 (20 min post-extubation), and T6 (on PACU discharge)	During the period in the post-anesthesia care unit (PACU) (up to 1 days)

Collaborators and Investigators

• Sponsor: Jianbo Wu
• Investigators: Principal Investigator: Jianbo WU, Doctoral, Shandong First Medical University

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): July 1, 2028
• Study Completion (Estimated): October 1, 2028

Study Registration Dates

• First Submitted: June 5, 2026
• First Submitted That Met QC Criteria: June 16, 2026
• First Posted (Actual): June 17, 2026

Study Record Updates

• Last Update Posted (Actual): June 17, 2026
• Last Update Submitted That Met QC Criteria: June 16, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Other Study ID Numbers: YXLL-KY-2026(147)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No