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NCT Number: NCT07239557

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

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.

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Key information

Conditions

Major Abdominal Surgery Atelectasis Lung Diseases Lung Ultrasound Score Lung-protective Ventilation Pathologic Processes Pathological Conditions, Signs and Symptoms Postoperative Pulmonary Complications Pulmonary Atelectasis Respiration Disorders Respiratory Aspiration Respiratory Tract Diseases

Age range

65 year–80 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

SixthSunYetSen

Guangzhou, Guangdong, 510600, China

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Different interval of PARM

Procedure

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.

Primary outcomes

  1. The effectiveness of recruitment

    Time frame: Intraoperative

    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%.

Secondary outcomes

  1. Mechanical power at the end of surgery

    Time frame: 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

    Mean or median mechanical power

  2. Time-weighted average mechanical power during surgery

    Time frame: During intraoperative mechanical ventilation

    Mechanical power per ventilation time

  3. The P/F ratio at the end of surgery,

    Time frame: 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)

    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.

  4. Dead space rate

    Time frame: 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)

    Arterial carbon dioxide partial pressure (PaCO2); partial pressure of carbon dioxide in end expiratory gas (PetCO2); Dead space fraction = (PaCO2-PetCO2)/ PaCO2.

  5. Air-breathing test

    Time frame: 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)

    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

  6. Intraoperative hypotension

    Time frame: During mechanical ventilation in the intraoperative period.

    Defined as mean arterial pressure (MAP) <60 mmHg from any cause, lasting for more than 3 minutes。

  7. Intraoperative vasopressor use.

    Time frame: During intraoperative mechanical ventilation

    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.

  8. Intraoperative mild hypoxemia

    Time frame: During intraoperative mechanical ventilation

    SpO₂ ≤96% lasting for more than 3 minutes

  9. Intraoperative severe hypoxemia

    Time frame: During intraoperative mechanical ventilation

    SpO₂ ≤92% lasting for more than 3 minutes

  10. Lung ultrasound score (LUS) in the post-anesthesia care unit (PACU)

    Time frame: Awake with spontaneous breathing before discharge from the PACU

    The 12-zone lung ultrasound score (LUS) ranges from 0 to 3 per zone (total 0-36). Higher scores indicate more severe atelectasis.

  11. Rate of respiratory failure at post-anesthesia care unit (PACU)

    Time frame: Stay in the PACU for at least 20 minutes and at most 3 hours; assessed at 5 to 10 minutes before leaving PACU

    PaO₂/FiO₂ <300 mmHg, or PaO₂ <60 mmHg or SpO₂ <90% while awake and breathing room air.

  12. Rate of postoperative respiratory failure

    Time frame: Day1 to 5 after surgery

    PaO₂/FiO₂ <300 mmHg, or PaO₂ <60 mmHg or SpO₂ <90% while awake and breathing room air.

  13. Rate of sustained hypoxaemia

    Time frame: Day 1 to 5 after surgery

    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%.

  14. Postoperative pulmonary complications, Grades 1-4

    Time frame: Day 0 to 5 after surgery

    Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 1 to 4.

  15. Postoperative pulmonary complications, Grades 2-4

    Time frame: Day 0 to 5 after surgery

    Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 2 to 4

  16. Pneumothorax

    Time frame: Day 0 to 7 after surgery

    Defined as the presence of air within the pleural cavity, with the visceral pleura not being surrounded by a vascular pattern.

  17. Postoperative hospitalization days

    Time frame: Day 0 to 30 after surgery

    The duration between the operation date and the actual discharge date.

  18. Unexpected admission to ICU

    Time frame: within 30 days after surgery

    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.

  19. Death from any cause

    Time frame: Day 0 to 30 after surgery

    Intraoperative or postoperative death from any cause

Sponsors and collaborators

Lead sponsor

Sixth Affiliated Hospital, Sun Yat-sen University

Other

Registry information

Official study title

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

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Nov 20, 2025
Registry last updated
May 15, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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