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 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
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
TRIPLE
Enrollment
324
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.
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.
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
Time frame: During the period in the post-anesthesia care unit (PACU) (up to 1 days)
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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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)
Time frame: 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)
Time frame: 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)
Time frame: During the period in the post-anesthesia care unit (PACU) (up to 1 days)
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