What Researchers Did
Researchers measured lung function in 26 divers after they completed a single deep dive using a helium-oxygen mixture to depths of 80, 100, or 120 metres, taking measurements before, 30 minutes after, and 24 hours after the dives.
What They Found
After an 80-metre dive, the FEV₁/FVC ratio dropped from 89.2% to 87.1% and MEF₂₅ decreased from 2.57 L·s⁻¹ to 2.35 L·s⁻¹ at 30 minutes post-dive, though the FEV₁/FVC ratio returned to normal within 24 hours. Similarly, after a 120-metre dive, FEV₁/FVC decreased from 90.4% to 85.6% and MEF₇₅ from 8.05 L·s⁻¹ to 7.46 L·s⁻¹. These findings suggest that deep heliox dives cause a temporary reduction in certain lung function measures that typically recover within 24 hours.
What This Means for Canadian Patients
This study primarily concerns the physiological effects of deep diving on healthy individuals, not medical patients. Canadian recreational and professional divers should be aware that deep heliox dives may temporarily affect their lung function, though these changes appear to resolve within 24 hours.
Canadian Relevance
This study was not conducted by Canadian authors or in Canada. However, it explores aspects of diving physiology relevant to decompression, which is a Health Canada-recognized indication for hyperbaric oxygen therapy (decompression sickness).
Study Limitations
The study's main limitation is the small number of participants in the deeper dive groups (100 and 120 msw), which may have led to inconsistent findings.