Effect of simulated diving trips on pulmonary artery pressure in healthy men.

Background: Environmental stresses, such as immersion, cold, and venous gas microbubbles, have been shown to contribute to an increase in pulmonary artery pressure (PAP) after single SCUBA dives. This study was carried out to investigate PAP changes following a dry chamber dive.
Methods: 17 male divers [mean age 32 years, standard deviation (SD) 7 years, mean body mass index 26 kg m(-2) (SD 3 kg m(-2))] participated in the study. Heart disease was ruled out by ECG, stress-ECG and transthoracic echocardiography in all subjects. Echocardiographic assessment of PAP (peak gradient at pulmonary and tricuspid valve), acceleration time (AT), ejection time (ET) and the ratio AT/ET as an estimate of PAP was performed directly prior to, directly, and 20 and 80 min after a simulated dive (maximal pressure 600 kPa, duration 60 min).
Results: AT/ET decreased from 0.40 (SD 0.03) to 0.34 (SD 0.03) directly after the dive (p = <0.0001), which was statistically significant, whereas 80 min after decompression, AT/ET tended to return to baseline levels (0.36, SD 0.03; p = 0.001). Other echocardiographic indices, e.g. ET, systolic PAP, and heart rate, did not change significantly after the dive. No gas microbubbles were detected during or after decompression.
Conclusions: A transient decrease of both AT and AT/ET following a simulated hyperbaric dry chamber dive indicated an increase in mean PAP in healthy men. We speculate that factors other than immersion, cold, or gas microbubbles may contribute to an elevation of PAP after a single hyperbaric exposure.