Recruitment manoeuvres in critically ill patients
Research type
Research Study
Full title
An observational study of the relationship between pressure-volume curves and recruitability of the lung in mechanically ventilated critically ill patients with respiratory failure
IRAS ID
306692
Contact name
Jessica Souza Luiz
Contact email
Sponsor organisation
University of Oxford
Duration of Study in the UK
2 years, 0 months, 1 days
Research summary
Research Summary:
Diseases of the lungs can be life-threatening. When these organs fail to adequately work, treatments to support their function are offered, often in Intensive Care Units (ICU). Respiratory failure patients may need sedation and placement of a tube in their windpipe so that a mechanical ventilator can take over their breathing until they have recovered enough to breathe again on their own.
One problem that occurs in patients under mechanical ventilation is that parts of the lung tissue tend to collapse (atelectasis), reducing the amount of the lung that is able to transfer oxygen and carbon dioxide effectively and even progressing to pneumonia.
To address this problem, ICU doctors often perform a procedure named ‘recruitment manoeuvre’, which involves briefly inflating the patient’s lungs with enough pressure to try to open up the collapsed areas of lung. However, fundamental aspects of the change in the functioning of the heart and lungs that occur during and after such manoeuvre are not fully understood.
In this study, funded by the University of Oxford, we wish to study patients with respiratory failure who are receiving mechanical ventilation. Patients will be recruited at the ICU of the Royal Berkshire Hospital having their cardiopulmonary data collected over the course of a day. During this period, some patients will be assessed to determine whether they may benefit from a recruitment manoeuvre using a pressure-volume curve. As this assessment is not perfect, we wish to study which features of this curve predict a successful recruitment. We will do this by evaluating the volume of the lung before and after the recruitment manoeuvre is performed using a device named Optical Gas Analyser.
A better understanding of the effects of the recruitment manoeuvre will help us to determine how and when such manoeuvres should be performed in critically ill patients.Summary of Results:
: In this study, we aimed to better understand how the lungs behave in critically ill patients who require mechanical ventilation, and in particular what happens when a procedure called a recruitment manoeuvre is used to try to open up collapsed parts of the lung.
To do this, we used a new bedside monitoring technique to measure how much air is present in the lungs at the end of a breath (sometimes called functional residual capacity or end-expiratory lung volume), and how evenly air is distributed within the lungs.
WHAT WE FOUND:
1. We were able to measure lung volumes reliably at the bedside.
- The new measurement technique worked well in patients on intensive care. It provided consistent and repeatable measurements of lung volume without interrupting routine care. This shows that it is possible to monitor these important lung measurements directly in critically ill patients.2. The effects of recruitment manoeuvres varied greatly between patients.
- When recruitment manoeuvres were performed, the change in lung volume was very different from one patient to another: some patients showed a clear increase in lung volume, suggesting that previously collapsed areas of lung had reopened; others showed little change; a small number showed a decrease in lung volume after the manoeuvre.
- In some patients, any improvement was not sustained over time, with the lung partially collapsing again after the manoeuvre.
- Overall, this shows that recruitment manoeuvres do not have the same effect in all patients.3. Existing methods did not reliably predict who would benefit Before performing a recruitment manoeuvre, clinicians often use measurements from the ventilator (such as pressure–volume curves) to try to predict whether a patient’s lungs will respond.
- In this study, these commonly used measures did not reliably predict how much the lung volume would actually increase.
- This suggests that current bedside methods may not be sufficient to guide when recruitment manoeuvres should be used.4. The amount of lung recruited during the manoeuvre did not always match lasting benefit
- The increase in lung volume seen during the manoeuvre itself did not always reflect how much improvement remained afterwards.
- This means that short-term changes seen during the procedure may overestimate its true benefit.5. Lung “inhomogeneity” (uneven ventilation) generally did not improve
- We also measured how evenly air was distributed within the lungs.
- Most patients had uneven ventilation at baseline, and this did not significantly improve after recruitment manoeuvres.
- This suggests that even when lung volume increases, the overall function of the lung may not improve in a meaningful way.WHAT THESE RESULTS MEAN:
This study shows that:
- It is now possible to measure important lung function directly at the bedside in critically ill patients.
- Recruitment manoeuvres have highly variable effects, and are not beneficial for all patients.
- Current methods used to decide when to perform these manoeuvres may not be reliable.Overall, the findings suggest that treatments like recruitment manoeuvres should be used more carefully and tailored to the individual patient, rather than applied routinely.
WHY THIS MATTERS:
A better understanding of how the lungs respond to these interventions may help improve future care for patients on intensive care. In particular, it may support the development of more personalised approaches to mechanical ventilation, with the aim of improving outcomes and avoiding unnecessary or potentially harmful treatments.
REC name
South Central - Oxford C Research Ethics Committee
REC reference
22/SC/0127
Date of REC Opinion
7 Jun 2022
REC opinion
Further Information Favourable Opinion