Mh. Liner et D. Linnarsson, INTRAPULMONARY DISTRIBUTION OF ALVEOLAR GAS-EXCHANGE DURING BREATH-HOLD DIVING IN HUMANS, Journal of applied physiology, 78(2), 1995, pp. 410-416
Expirograms for CO2 and O-2 obtained immediately after 75-s breath hol
ds (BHs) in thermoneutral conditions were studied in 10 subjects. BHs
were performed at normal atmospheric pressure in dry condition (dry su
rface BH), at normal atmospheric pressure submerged (wet surface BH),
and during a transient increase of ambient pressure to 3 atmospheres a
bsolute submerged (wet BH dive). Cardiac index was estimated by means
of impedance cardiography. Phase III (alveolar plateau) slopes for CO2
expirograms were lowest after wet surface BH. The greater slope obser
ved after dry surface BH was attributed mainly to intrapulmonary perfu
sion heterogeneity and the greater slope seen after wet BH dive to con
tinuing alveolar CO2 exchange during expiration. Cardiogenic oscillati
ons in phase III (evaluated by spectral analysis) were largest after d
ry surface BH, much reduced by wet surface BH, and further reduced by
wet BH dive. This was attributed to more even distribution of pulmonar
y perfusion during submersion and compression. Terminal changes of the
expirograms (phase IV) revealed a less even interregional pulmonary d
istribution of CO2 and a more even distribution of O-2 after wet BH di
ve compared with wet surface BH. This difference was attributed to imp
roved apical pulmonary perfusion at depth during the wet BH dives.