HANA-KAI-II - 17-DAY DRY SATURATION DIVE AT 18.6 ATA .4. CARDIOPULMONARY FUNCTIONS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 4  (3) , 267-281
Abstract
Impedance plethysmography was used to measure resting cardiac stroke volume (SV) and thoracic conductive volume (TCV) in 4 divers at intervals during a prolonged dry saturation dive (17 days at 18.6 ATA [atmospheres absolute pressure] and 7 days'' decompression). Resting heart rate (HR), blood pressure (BP) and pulmonary minute ventilation (.ovrhdot.VE) were measured 4 times/day for the duration of the 30 day experiment. The vital capacity (VC) and its subdivisions IC [inspiratory capacity] and ERV [expiratory reserve capacity) were measured by spirometry every 3 days. In nonsmokers, VC fell significantly with time (r [correlation coefficient] = 0.64), while VC in smokers increased nearly 400 ml during the 1st wk at pressure before tending to fall with time. Compared to predive, the mean ERV was increased 629 ml at pressure, while .ovrhdot.VE and respiratory rate were not changed. The increased ERV did not persist postdive and was probably the result of the increased work of breathing a dense gas (4.1 g/l). Residual volume (RV) measured by N dilution before and after the dive increased 38% and remained significantly increased (22%) even after 1 yr in 4 divers. Hyperoxia (0.3 ATA PO2[O2 partial pressure]) combined with increased gas flow resistance caused the VC to fall and RV to increase. The major cardiovascular findings were a transient bradycardia associated with increased SV leading to a significant increase in resting cardiac output associated with an increased rate of rapid ventricular filling, TCV and BP [blood pressure] at depth. Lowering the ambient temperature for 3 days did not reestablish the bradycardia, suggesting that hyperbaric bradycardia was not due to a subtle cold stress.