Study Goal The goal of this observational, multicenter study is to evaluate how positive end-expiratory pressure (PEEP) affects right ventricular (RV) function in patients with acute respiratory distress syndrome (ARDS) who are receiving mechanical ventilation. Researchers will assess the Recruitment-to-Inflation (R/I) ratio, a measurement used to determine whether increasing PEEP helps open the lungs or causes harmful effects on the heart and circulation.
Main Study Questions
This study aims to answer the following questions:
1. How does PEEP affect right heart function in ARDS patients?
2. Can the R/I ratio predict whether PEEP will have a beneficial or harmful impact on the heart?
3. Which echocardiographic parameters best detect changes in right ventricular function caused by PEEP?
Who Can Participate?
Patients will be included in the study if they meet the following criteria:
* Age: 18 to 80 years.
* Condition: Diagnosed with moderate-to-severe ARDS, with a PaO₂/FiO₂ ratio <200 mmHg (an indicator of severe breathing difficulty).
* Mechanical Ventilation: Receiving invasive ventilation with at least 5 cmH₂O of PEEP and in deep sedation (fully dependent on the ventilator).
* Cardiac Monitoring: Equipped with a MostCare Up or equivalent device for continuous heart function monitoring.
* Informed Consent: Given directly by the patient or through a legal representative.
Patients will not be included in the study if they:
* Have severe pulmonary hypertension (high pressure in the lungs, ≥70 mmHg).
* Have a tricuspid valve prosthesis or other implanted cardiac devices that interfere with echocardiographic imaging.
* Have undergone recent heart surgery (within the past month).
* Have severe tricuspid valve disease that makes it difficult to assess right heart function.
* Are hemodynamically unstable, requiring high doses of medication to maintain blood pressure.
* Have poor ultrasound imaging conditions that prevent accurate heart scans.
* Have recently had a pulmonary embolism or have known blockages in the pulmonary arteries.
* Are receiving extracorporeal membrane oxygenation (ECMO) support.
Study Procedures
Participants will undergo a series of tests to measure the impact of PEEP on lung and heart function:
1. Initial Airway Closure Test: Patients will be evaluated while on a low PEEP level of 5 cmH₂O for 10 minutes to confirm eligibility.
2. Recruitment-to-Inflation (R/I) Ratio Assessment:
* PEEP will be adjusted between low (5 cmH₂O) and high (15 cmH₂O) levels.
* Researchers will measure changes in lung mechanics and heart function using ultrasound.
3. Echocardiographic Heart Function Assessment:
* Transthoracic echocardiography (TTE) will be performed at each PEEP level to assess the right ventricle (RV) and circulation in the lungs.
* Researchers will measure RV strain, size, and blood flow to determine how the heart reacts to PEEP changes.
4. Data Collection:
oKey respiratory and hemodynamic parameters will be recorded, including heart strain, cardiac output, pulmonary artery pressure, and venous congestion.
Primary and Secondary Study Outcomes
* Primary Outcome: The study will evaluate how RV function changes in response to different PEEP levels, using 2D RV strain measurements as a key indicator.
* Secondary Outcomes: Researchers will assess:
* How accurately echocardiographic measurements (e.g., TAPSE, FAC, VExUS score) detect changes in RV function.
* The relationship between the VExUS score (a marker of venous congestion) and RV strain changes.
* The sensitivity and specificity of echocardiographic findings in predicting heart function shifts under different PEEP levels.
Statistical Analysis
* Researchers will compare echocardiographic heart function results at high PEEP vs. low PEEP using statistical models.
* The relationship between the R/I ratio and RV function will be analyzed using correlation tests and logistic regression.
* Receiver Operating Characteristic (ROC) analysis will be used to determine which echocardiographic parameter best detects RV dysfunction when the R/I ratio is low.
Study Size and Impact The study aims to enroll 60 patients (30 per group) to ensure that results are reliable. This sample size was calculated to detect at least a 10% change in RV strain, with a 90% probability of identifying significant effects.
Expected Benefits of the Study This study will help critical care doctors better understand how to adjust PEEP settings to balance lung recruitment and heart function in ARDS patients. By identifying the best methods to detect right heart dysfunction early, this research could lead to improved ventilation strategies and better survival outcomes for patients with severe lung injury.m
