Research digest: Protecting the lungs with LFV during cardiopulmonary bypass

The use of low frequency ventilation (LFV) during cardiopulmonary bypass (CPB) for patients undergoing valvular surgery is feasible and safe, a new study has concluded.

LFV led to better postoperative lung function and improved exercise ability in patients undergoing surgery for heart valve disorders.

Researchers randomly assigned 63 patients with severe mitral or aortic valve disease undergoing surgery to LFV or usual care (33 LFV vs 30 usual care). The mean age of patients was 66.8 years and 30% were female.

Patients were assessed for generic inflammatory and vascular biomarkers and the lung‐specific biomarker soluble receptor for advanced glycation end-products (sRAGE) up to 24 hours after surgery. They then undertook pulmonary function tests and six‐minute walking tests up to eight weeks after discharge.

Overall, patients who received LFV showed better preservation of lung function and respiratory health, the researchers said.

Some 10 minutes after surgery, patients who received LFV showed elevated sRAGE levels, approximately three times above base level (geometric mean ratio, 3.05; [95% CI, 1.13– 8.24], suggesting damage to the lungs.

However, sRAGE levels gradually reduced over 24 hours, with measurements of 1.07, 0.84, 0.67 and 0.62 at two, four, six, 12 and 24 hours post-CPB, respectively, showing an overall reduction in lung injury and recovery over time. All results had a confidence level of 95%. The researchers observed no changes for any of the generic biomarkers tested.

Lung function tests highlighted significant improvement in lung function in patients who had LFV. The mean difference in FEV1/FVC ratio (forced expiratory volume in 1 second/forced vital capacity ratio) was improved by 0.050 six to eight weeks post-surgery for the LFV group, and forced vital capacity was also better preserved in the LFV group, with patients able to walk 63.2 metres further than those in the control group.

The researchers concluded that the use of LFV led to a significant improvement in exercise capacity and overall physical recovery.

A more extensive phase III trial will take place across the UK to allow the researchers to investigate further.

Reference
Roger, C et al. Low Frequency Ventilation During Cardiopulmonary Bypass to Protect Postoperative Lung Function in Cardiac Valvular Surgery: The PROTECTION Phase II Randomized Trial. Journal of the American Heart Association 2024; Sept 30: DOI: 10.1161/JAHA.124.035011.