Characteristics of the response to exercise in professional saturation divers

Exercise testing with measurements of expired minute ventilation (VE), oxygen uptake (VO2), and carbon dioxide elimination (VCO2) was done in 63 professional saturation divers, in the screening programs for selection of divers, to 10 different experimental and operational saturation dives. Their experience as divers averaged 9.8 yr (range 1-20), and they averaged 276 days (range 5-900) in saturation. The maximal pressure they had ever been exposed to averaged 2.01 MPa (range 0.8-5.1). The divers were compared with a control group of 47 offshore workers and policemen matched for age, height, and smoking habits and with reference values for the general healthy population. There were no significant differences in peak work load achieved, VO2peak and VCO2peak. VE at VO2peak and the corresponding ventilatory equivalents for oxygen uptake (VE(peak)/VO2peak) and carbon dioxide elimination (VE(peak)/VCO2peak) were significantly higher in divers (P less than 0.05), but VE, VE/VO2 and VE/VCO2 were not different at lower work loads. VE(peak)/VCO2peak correlated positively with years of diving experience when corrected for age (P less than 0.01). Divers had higher tidal volumes and lower breathing frequencies at ventilations lower than 40% of VE(peak), but maximal tidal volumes were not different. Tidal volume at a VE of 30 liter.min(-1) correlated negatively with FEV1 (P less than 0.05). The results are in agreement with the transient changes in pulmonary function and exercise tolerance demonstrated after a single saturation dive, and indicate that these changes may not be completely reversible.