THE USE OF HYDROGEN AS AN INERT GAS DURING DIVING: PULMONARY FUNCTION DURING HYDROGEN-OXYGEN BREATHING AT PRESSURES EQUIVALENT TO 200 FEET OF SEA WATER by

A review of the characteristics of hydrogen as an inert gas for use in diving is presented, with special emphasis on the extention of the respiratory limitation in diving by use of this least dense of all gases. Forced vital capacity (FVC), forced expiratory volume in one second (FEVi), forced expiratory volume in two seconds (FEV2). peak expiratory flow rate (PEFR), peak inspiratory flow rate (PIFR), and maximal voluntary ventilation (MVV) were measured on groups of subjects using the following gas mixtures, — all at the equivalent of 200 fsw: four subjects breathing 97% H2-3% O2; two subjects breathing 97% He-3% O2, and two divers using 97% N2-3% O2. The MVV on H2-O2 at 200 fsw was 14% better than on air at the surface, and was improved 40% compared with He-02 and 171% when compared with N2-O2 at 200 fsw. Similar findings were obtained for the following functions: FEVi, FEV2, PEFR, and PIFR. This is the first study in which pulmonary function has been measured during hydrogen-oxygen breathing. The values in this study for the relationship of relative gas density (p) to flow are in good agreement with both the theoretical and experimental values of Wood and Bryant which ranged from p-0.41 to p~°. This study showed relationships of p-0.41 for MVV, p~for PEFR, and p'for PIFR. 39 Clip and Mail Form for Change of Address: To: Commanding Officer, Naval Submarine Medical Research Laboratory, Attn: Code 03B Subj: Change of Address 1. I/We wish to continue to receive NavSubMedRschLab Reports, however, the following change of address should be noted: