Experimental Approaches To Problems Of The Heart And Lungs In Diving

Abstract

SummaryDivers face problems during their work due t o s t r e s s e s p l a c e d upon t h e r e s p i r a t o r y s y s t e m by t h e hyperbaric environment. In addition, both the r e s p i r a t o r y and cardiovascular systems may be injured during the course of decompression sickness. Work a t the Naval Medical Research Institute ( W I ) i s directed toward solving problems in both these areas. A system of magnetometers allows evaluation of the impact of s t r e s s e s from the underwater environment on t h e d i v e r ' s r e s p i r a t o r y s y s t e m w i t h o u t i n t e r f e r i n g w i t h h i s b r e a t h i n g . O t h e r r e s e a r c h d e s c r i b e d h e r e i n is e x p l o r i n g h i g h -f r e q u e n c y o s c i l l a t i o n (HFO) of a d i v e r ' s b r e a t h i n g g a s a s a means of l e s s e n i n g l i m i t a t i o n s imposed by increased gas density. F i n a l l y , r e c e n t a n d o n g o i n g r e s e a r c h d e s c r i b e d i n t h i s paper i s aimed a t u n d e r s t a n d i n g t h e n a t u r e and mechanisms of i n j u r y t o t h e h e a r t and lungs during decompression sickness, with the goal of improving prevention and treatment of this disorder.Divers working a t d e p t h i n c u r a l i m i t a t i o n on t h e i r e x e r c i s e p e r f o r m a n c e t h a t i s imposed by t h e respiratory system. This limitation can be magnified by breathing equipment designed without regard to the u n i q u e s t r e s s e s p l a c e d upon t h e r e s p i r a t o r y s y s t e m by the diver's environment.To s t u d y t h e e f f e c t s of t h e h y p e r b a r i c environment on t h e r e s p i r a t o r y s y s t e m , a system of magnetometers has been developed that allows monitoring of t h e d i v e r ' s v e n t i l a t i o n w i t h o u t i n t e r f e r i n g w i t h h i s b r e a t h i n g , and without concern for the dependence on d e n s i t y of standard flow measuring devices.A magnetometer consists of a p a i r o f w i r e C o i l s .A l t e r n a t i n g c u r r e n t i s passed through one of the c o i l s . This induces a c u r r e n t i n t h e s e c o n d c o i l t h a t i s p r o p o r t i o n a l t o t h e d i s t a n c e b e t w e e n t h e c o i l s . Using magnetometers t o measure the anteroposterior (AP) and l a t e r a l (L) dimensions of t h e abdomen (ab)and r i b c a g e ( r c ) , R o b e r t s o n e t a l . were a b l e t o c a l c u l a t e r e s p i r a t o r y v o l u m e . ' The method was automated off-line using a d i g i t a l computer and the following model f o r c a l c u l a t i n g pulmonary volume (V): (1) where (Arc) i s the area of the rib cage and (Aab) i s t h e a r e a o f t h e abdomen c a l c u l a t e d by assuming a h o r i z o n t a l o v a l t h r o u g h t h e r i b c a g e and another h o r i z o n t a l o v a l t h r o u g h t h e abdomen. The l e n g t h O f t h e a x i s of each oval i s measured by t h e a p p r o p r i a t e AP and L magnetometer p a i r , and the area is c a l c u l a t e d as fo...