Trunk Inclination, Positive End-expiratory Pressure, and Lung Recruitability
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Specific lung recruitment maneuvers and decremental PEEP steps.
- Who it may be relevant to
- Registry conditions: Acute Respiratory Distress Syndrome (ARDS). Basic parameters: from 18 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- China
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
Unsure about the terms? Read our patient guide →
Official title
Impact of Trunk Inclination on Lung Mechanics According to PEEP and Reruitability
Overview
This multicenter, physiological, observational study hypothesizes that in moderate to severe ARDS, trunk inclination unloads the chest wall, but its impact on lung mechanics depends on PEEP levels and lung recruitability.
Detailed description
There is near-universal agreement among caregivers that head-up positioning is beneficial for mechanically ventilated patients. In most intensive care units, a semi-recumbent position (head of bed elevated 30-45°) has therefore become standard practice, except when absolutely contraindicated. This widespread adoption is driven primarily by robust clinical evidence showing that trunk inclination reduces the incidence of ventilator-associated pneumonia. In patients under general anesthesia, physiological studies showed a clear mechanistic benefit: the vector of abdominal weight shifts caudally, increasing resting lung volume and thereby decreasing the tendency for atelectasis formation.
In patients with acute respiratory distress syndrome (ARDS), however, the physiological consequences of trunk inclination remain undecided. Here, the descent of the diaphragm in the head-up position increases transpulmonary pressure (PL) at end-expiration, which tends to recruit previously collapsed lung units. Yet the "baby lung" of ARDS, the markedly reduced aerated lung volume, operates on widely different segments of its pressure-volume curve (i.e. the lower flat portion, the steep linear portion, or the upper flat portion). Consequently, the net effect of the rise in end-expiratory PL depends on whether recruitment of additional units outweighs overdistension of those already open.
Theoretically, for example, in patients with high lung recruitability but insufficient PEEP, trunk inclination should tilt the balance toward recruitment; in the same patients receiving excessive PEEP, the same maneuver may instead promote overdistension. To date, however, neither the overall effect of trunk inclination nor the modulating roles played by PEEP level and lung recruitability have been adequately assessed. Previous studies have almost invariably assessed trunk inclination at a single fixed PEEP without quantifying lung recruitability, thereby limiting the generalizability of their findings and leaving unresolved the complex interactions among posture, PEEP, chest-wall mechanics, and recruitability.
To address these critical gaps, the investigators designed this multicenter, physiological, observational study. The investigators hypothesized that, in moderate to severe ARDS, trunk inclination unloads the chest wall and that its net impact on lung mechanics is fundamentally determined by the prevailing PEEP level and the individual level of lung recruitability.
Interventions
- Other Specific lung recruitment maneuvers and decremental PEEP steps
Specific lung recruitment maneuvers will be performed to measure the potential for lung recruitment. Followed by a decremental PEEP steps to determine lung mechanics at different PEEP levels. These process will be repeated when patients change to another position. Electrical impedance tomography signals, synchronized signals of airway pressure and flow, esophageal pressure will be recorded continuously.
Primary outcome measures
- Transpulmonary driving pressure (ΔPL) [Time frame: 2 hour]
Secondary outcome measures (6)
- Percentage of overdistension and collapse [Time frame: 2 hours]
- Lung compliance (Clung) [Time frame: 2 hours]
- Respiratory system compliance (Crs) [Time frame: 2 hours]
- Chest wall compliance (Ccw) [Time frame: 2 hours]
- Recruitment-to-inflation (R/I) ratio [Time frame: 2 hours]
- Lung recruitability (ΔCollapse24-6) [Time frame: 2 hours]
Eligibility criteria
Inclusion criteria
- Intubated moderate and severe ARDS according to the Berlin definition (PaO2/FiO2 ratio <= 200 mmHg)
- Under continuous sedation with or without paralysis
Exclusion criteria
- Age <18 years
- Bronchopleural fistula
- Pure COPD exacerbation
- Contraindication to EIT monitoring (e.g. burns, pacemaker, thoracic wounds limiting electrode belt placement)
- Hemodynamic instability (Systolic BP < 75 mmHg or MAP < 60 mmHg despite vasopressors and/or heart rate < 55 bpm)
- Contraindications to mobilization (e.g., intracranial hypertension, spinal cord injury)
- Intra-abdominal hypotension (IAP≥12mmHg)
- Pregnancy
- Attending physician deems the transient application of high airway pressures to be unsafe
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Observational model
- Other
Study locations
China · 3 centers
- Zhongda Hospital, Southeast University — Nanjing
- The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Q — Jinan
- West China Hospital of Sichuan University — Chengdu
Identifiers
NCT: NCT07504731 · 2026