Improved pulmonary function in working divers breathing nitrox at shallow depths.
BACKGROUND
There is limited data about the long-term pulmonary effects of nitrox use in divers at shallow depths. This study examined changes in pulmonary function in a cohort of working divers breathing a 46% oxygen enriched mixture while diving at depths less than 12 m.


METHODS
A total of 43 working divers from the Neutral Buoyancy Laboratory (NBL), NASA-Johnson Space Center completed a questionnaire providing information on diving history prior to NBL employment, diving history outside the NBL since employment, and smoking history. Cumulative dive hours were obtained from the NBL dive-time database. Medical records were reviewed to obtain the diver's height, weight, and pulmonary function measurements from initial pre-dive, first year and third year annual medical examinations.


RESULTS
The initial forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were greater than predicted, 104% and 102%, respectively. After 3 yr of diving at the NBL, both the FVC and FEV1 showed a significant (p < 0.01) increase of 6.3% and 5.5%, respectively. There were no significant changes in peak expiratory flow (PEF), forced mid-expiratory flow rate (FEF(25-75%)), and forced expiratory flow rates at 25%, 50%, and 75% of FVC expired (FEF25%, FEF50%, FEF75%). Cumulative NBL dive hours was the only contributing variable found to be significantly associated with both FVC and FEV1 at 1 and 3 yr.


CONCLUSIONS
NBL divers initially belong to a select group with larger than predicted lung volumes. Regular diving with nitrox at shallow depths over a 3-yr period did not impair pulmonary function. Improvements in FVC and FEV1 were primarily due to a training effect.
Fitzpatrick
Daniel T
DT
Sonny Carter Training Facility, Neutral Buoyancy Laboratory, NASA-Johnson Space Center, Houston, TX 77058-3696, USA. daniel.t.fitzpatrick1@jsc.nasa.gov
Conkin
Johnny
J
D000328:Adult; D015331:Cohort Studies; D004242:Diving / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D009584:Nitrogen / Q000494:pharmacology*; D016273:Occupational Exposure; D010100:Oxygen / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects*; D012129:Respiratory Function Tests; D012907:Smoking / Q000503:physiopathology; D013995:Time; D016526:Workload
C041364:nitrox; D009584:Nitrogen; D010100:Oxygen