Optimal Interval for Periodic Alveolar Recruitment Maneuvers Achieving 90% Lung Re-expansion During Intraoperative Ventilation

Optimal Interval for Periodic Alveolar Recruitment Maneuvers Achieving 90% Lung Re-expansion During Intraoperative Mechanical Ventilation: A Randomized Biased-Coin Sequential Trial

This study aims to determine the optimal interval for periodic alveolar recruitment maneuvers (PARM) that can achieve effective lung re-expansion in 90% of patients undergoing intraoperative mechanical ventilation during abdominal laparoscopic surgery in the low Trendelenburg position. Identifying the most effective frequency of PARM is crucial for establishing lung-protective ventilation strategies, with the ultimate goal of reducing intraoperative atelectasis, decreasing postoperative pulmonary complications, and accelerating recovery.

Patients are randomized using a biased-coin sequential design. PARM is initially applied every 0.5 hours, and the effectiveness of lung re-expansion is evaluated before the end of surgery. The primary outcome is the effectiveness of recruitment, assessed by a combination of lung ultrasound scores and shunt fraction. Secondary outcomes include mechanical power at the end of surgery, time-weighted average mechanical power during ventilation, postoperative P/F ratio, dead space fraction, air test results, intraoperative adverse events, incidence of respiratory failure in the PACU and postoperative period, and postoperative length of stay.

This trial is expected to provide robust evidence for defining the optimal RM interval in protective ventilation protocols for patients undergoing laparoscopic abdominal surgery, thereby contributing to improved perioperative respiratory outcomes.

Study Overview

• Status: Enrolling by invitation
• Conditions: Major Abdominal Surgery; Atelectasis; Postoperative Pulmonary Complications; Lung Ultrasound Score; Lung-protective Ventilation
• Intervention / Treatment: Procedure: Different interval of PARM

Detailed Description

This study is designed to evaluate the optimal interval of periodic alveolar recruitment maneuvers (PARM) to achieve effective lung re-expansion (defined as LUS ≤1 and shunt fraction <10%) in 90% of elderly patients undergoing laparoscopic anterior resection in low Trendelenburg position. This is a single-arm, biased-coin sequential design study. The initial PARM interval is 30 min, adjusted in 10 min increments based on response. The primary outcome is recruitment efficacy. Secondary outcomes include intraoperative mechanical power, P/F ratio, postoperative pulmonary complications, and length of hospital stay. This study aims to inform optimal RM intervals in protective ventilation protocols.

• Study Type: Interventional
• Enrollment (Estimated): 52
• Phase: Not Applicable

Contacts and Locations

Study Locations

• China
  • Guangdong
    • Guangzhou, Guangdong, China, 510600
      • SixthSunYetSen

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 65-80 years
• Undergoing elective laparoscopic anterior resection (expected mechanical ventilation duration 2-5 hours)
• Intermediate risk for postoperative pulmonary complications
• Room air SpO₂ ≥94%

Exclusion Criteria:

• History of pneumonia within 1 month or mechanical ventilation ≥1 hour
• Preoperative 12-zone LUS with any single zone score ≥2
• Preoperative shunt fraction ≥10%
• Progressive neuromuscular disease
• Severe emphysema/COPD or subpleural bullae ≥2 cm
• Intracranial hypertension
• Participation in other studies or refusal to participate

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: N/A
• Interventional Model: Sequential Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: PARM

Procedure: Different interval of PARM; The initial time interval of PARM was 0.5 hours/time, and the different interval of PARM was assigned by random partial coin sequential method.If the previous patient did not respond to postoperative assessment of lung opening, the interval between expansion of the lungs was shortened by 10 minutes for the next patient; If lung opening is effective, there is an 11% chance that the next patient will have an 10-minute expansion interval and an 89% chance that the time interval will remain unchanged.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The effectiveness of recruitment	The effectiveness of recruitment assessed by a combination of lung ultrasound scores and shunt fraction。At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver), a lung ultrasound examination was performed. Lung re-expansion was considered effective if the 12-zone lung ultrasound score (LUS) was ≤1 per zone and the shunt fraction was <10%.	Intraoperative

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Postoperative hospitalization days	The duration between the operation date and the actual discharge date.	Day 0 to 30 after surgery
Death from any cause	Intraoperative or postoperative death from any cause	Day 0 to 30 after surgery
Unexpected admission to ICU	It does not include the patients who enter ICU at the request of surgeons but have normal spontaneous breathing, stable circulation and no disturbance of consciousness.	within 30 days after surgery
Mechanical power at the end of surgery	Mean or median mechanical power	With the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver
Time-weighted average mechanical power during surgery	Mechanical power per ventilation time	During intraoperative mechanical ventilation
The P/F ratio at the end of surgery,	P/F ratio = PaO₂ / FiO₂.Statistical measure: Incidence of P/F ratio ≤400. The P/F ratio is an objective research parameter, and a P/F ratio ≤400 indicates the presence of atelectasis.	At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Dead space rate	Arterial carbon dioxide partial pressure (PaCO2); partial pressure of carbon dioxide in end expiratory gas (PetCO2); Dead space fraction = (PaCO2-PetCO2)/ PaCO2.	At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Air-breathing test	After completion of ultrasound and arterial blood gas measurements, the inspired oxygen concentration was adjusted to 21%. SpO₂ was observed and recorded after 5 minutes.The incidence of a positive air-breathing test, defined as SpO₂ ≤96%, was recorded	At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Intraoperative hypotension	Defined as mean arterial pressure (MAP) <60 mmHg from any cause, lasting for more than 3 minutes。	During mechanical ventilation in the intraoperative period.
Intraoperative vasopressor use.	Defined as any episode of MAP <60 mmHg during mechanical ventilation requiring the administration of catecholamine vasopressors, including dopamine, epinephrine, or norepinephrine. Occurrence of such an event was recorded as positive.	During intraoperative mechanical ventilation
Intraoperative mild hypoxemia	SpO₂ ≤96% lasting for more than 3 minutes	During intraoperative mechanical ventilation
Intraoperative severe hypoxemia	SpO₂ ≤92% lasting for more than 3 minutes	During intraoperative mechanical ventilation
Lung ultrasound score (LUS) in the post-anesthesia care unit (PACU)	The 12-zone lung ultrasound score (LUS) ranges from 0 to 3 per zone (total 0-36). Higher scores indicate more severe atelectasis.	Awake with spontaneous breathing before discharge from the PACU
Rate of respiratory failure at post-anesthesia care unit (PACU)	PaO₂/FiO₂ <300 mmHg, or PaO₂ <60 mmHg or SpO₂ <90% while awake and breathing room air.	Stay in the PACU for at least 20 minutes and at most 3 hours; assessed at 5 to 10 minutes before leaving PACU
Rate of postoperative respiratory failure	PaO₂/FiO₂ <300 mmHg, or PaO₂ <60 mmHg or SpO₂ <90% while awake and breathing room air.	Day1 to 5 after surgery
Rate of sustained hypoxaemia	Sustained hypoxaemia, hypoxaemia at any two consecutive days; hypoxaemia: during a follow-up visit when the patient was awake and breathing room air, SpO2 ≤ 92% or the change of SpO2 (ΔSpO2, preoperative SpO2 minus postoperative SpO2) ≥ 5%.	Day 1 to 5 after surgery
Postoperative pulmonary complications, Grades 1-4	Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 1 to 4.	Day 0 to 5 after surgery
Postoperative pulmonary complications, Grades 2-4	Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 2 to 4	Day 0 to 5 after surgery
Pneumothorax	Defined as the presence of air within the pleural cavity, with the visceral pleura not being surrounded by a vascular pattern.	Day 0 to 7 after surgery

Collaborators and Investigators

• Sponsor: Sixth Affiliated Hospital, Sun Yat-sen University

Study record dates

Study Major Dates

• Study Start (Actual): December 10, 2025
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: September 25, 2025
• First Submitted That Met QC Criteria: November 18, 2025
• First Posted (Actual): November 20, 2025

Study Record Updates

• Last Update Posted (Actual): May 15, 2026
• Last Update Submitted That Met QC Criteria: May 13, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Major abdominal surgery; Mechanical ventilation; Laparoscopy; Trendelenburg position; Respiratory function; Lung ultrasound score; Lung-protective ventilation; Periodic recruitment maneuvers; Lung recruitment strategy; Effective concentration for 90% (EC90)
• Additional Relevant MeSH Terms: Pathologic Processes; Respiratory Tract Diseases; Lung Diseases; Respiration Disorders; Pathological Conditions, Signs and Symptoms; Respiratory Aspiration; Pulmonary Atelectasis
• Other Study ID Numbers: E2025034

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