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The relation between tidal volume and inspiratory and expiratory times during steady‐state carbon dioxide inhalation in man
Author(s) -
Gardner W. N.
Publication year - 1977
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1977.sp012062
Subject(s) - tidal volume , expiration , ventilation (architecture) , inhalation , mathematics , respiratory system , anesthesia , medicine , anatomy , chemistry , physics , thermodynamics
1. Ambiguities and discrepancies in the published descriptions of the patterns of breathing in man have been re‐investigated. Steady‐state hyperpnoea during rest was induced in normal subjects of both sexes by means of CO 2 inhalation, usually in high O 2 , but sometimes in low ( P A, O 2 ∼ 200 and 55 torr respectively). 2. The relations between mean tidal volume V̄ T and mean times for inspiration T̄ I and expiration T̄ E were satisfactorily divided into lower and upper parts (ranges 1 and 2) in nineteen out of thirty‐three experiments using an objective least‐squares method, and polynomials were fitted separately to each of the following pairs of variables V̄ T,lower , T̄ I ; V̄ T,lower , T̄ E ; V̄ T,upper , T̄ I ; V̄ T,upper , T̄ E . 3. The breakpoints occurred when V̄ T was about one third of vital capacity, but there was much variation between subjects. 4. In range 2, V̄ T was inversely related to both T̄ I and T̄ E and there appeared to be linkage between T̄ I and T̄ E , all as described by Clark & Euler (1972). The relation suggested by Hey, Lloyd, Cunningham, Jukes & Bolton (1966) over range 2 was not confirmed. 5. The main part of the relation described by Hey et al. (1966) is concerned with range 1. Here the relation between V̄ T and T̄ I was variable; slight, but significant negative correlation predominated. V̄ T was, on the other hand, strongly and inversely related to T̄ E , and plots of ( T̄ E — T̄ I ) against V̄ T over both ranges showed even less scatter. Hence ( a ) T̄ E is probably related to V̄ T through two mechanisms, one involving a link with T I and another prominent one being quite independent of T I , ( b ) most changes of respiratory frequency in normal man are brought about by change of T E rather than of T I , and ( c ) there is no region of constant frequency as implied by Clark & Euler (1972).