Carbon dioxide storage and nonbicarbonate buffering in the human body before and after an Himalayan expedition

Abstract

Before and 7-12 days after an Himalayan expedition CO2 equilibration curves were determined in the blood plasma of 12 mountaineers by in vitro and in vivo CO2 titration; in vivo osmolality changes (delta Osm x deltaPCO2(-1), deltaOsm x delta pH(-1), where PCO2 is the partial pressure of CO2) during the latter experiments yielded estimates of whole body CO2 storage. In vitro -delta[HCO3-] x delta pH(-1) [nonbicarbonate buffer capacity (beta) of blood] was increased 7 days after descent [before 31.3 (SEM 0.4) mmol x kgH2O(-1), after 38.3 (SEM 3.9) mmol x kgH2O(-1); P<0.05] resulting from an increased proportion of young erythrocytes; in additional experiments an augmented beta was found in young (low density cells) compared to old cells [<1.097 g x ml(-1): 0.216 (SEM 0.028) mmol x gHb(-1), >1.100 g x ml(-1): 0.145 (SEM 0.013) mmol x gHb(-1), where Hb is haemoglobin; P < 0.02]. In spite of increased Hb mass in vivo delta[CO2total] x deltaPCO2(-1) [0.192 (SEM 0.010) mmol x kgH2O(-1) x mmHg(-1)] and -delta[HCO3-] x delta pH(-1) [17.9 (SEM 1.0) mmol x kgH2O(-1)] as indicators of extracellular beta rose only slightly after altitude (7 days +16%, P<0.02; +7%, NS) because of haemodilution. The deltaOsm x deltaPCO2(-1) [0.230 (SEM 0.015) mosmol x kgH2O(-1) x mmHg(-1)] remained unchanged. Prealtitude differences in deltaOsm x delta pH(-1) between hypercapnia [-41 (SEM 5) mosmol x kgH2O(-1)] and hypocapnia [-20 (SEM 3) mosmol x kgH2O(-1); P<0.01] disappeared temporarily after return since the former slope was reduced. The high value during hypercapnia before ascent probably resulted from mechanisms stabilizing intracellular pH during moderate hypercapnia which were attenuated after descent.

Extracellular pH defense against lactic acid in normoxia and hypoxia before and after a Himalayan expedition

“…As derived in the preceding paper for resting conditions (BoÈ ning et al 1999), both an increased proportion of well buering young red cells as well as an increased total Hb mass (+14%) had augmented the total extracellular non-bicarbonate buer content in the 1st week after altitude exposure, by approximately one-third; b nbi , however, was increased only non-signi®cantly (by 7%), probably due to dilution of the buers in an augmented extracellular volume.…”

“…Whereas muscle buering capacity has been analyzed extensively (for a review see Sahlin 1978 andBoÈ ning et al 1999), only few observations of evaluations of blood or extracellular pH defense exist, in spite of there being a lot of experimental data. Usually, blood [La] ([La] blood ) is determined, which is lower than [La] plasma and is in¯uenced by Hct changes.…”

“…Twelve endurance-trained members of a German Medical Himalaya Expedition to Karakorum, Pakistan [ten males, two females, mean (SEM) age 30.8 (1.9) years, body mass 73.0 (2.8) kg, maximum oxygen uptake 61.0 (2.0) ml á kg )1 á min )1 for the males, 58.1 ml á kg )1 á min )1 and 48.0 ml á kg )1 á min )1 for the two females] took part in the study (for details see BoÈ ning et al 1997). Experiments were performed in accordance with the Helsinki Declaration of 1975 and after approval by the University Ethic Committee.…”

“…At high altitude the hemoglobin (Hb) mass increases (Weil et al 1968) and the [HCO À 3 ] in blood decreases (Dill et al 1937); since these eects remain detectable for at least 12 days after descent (BoÈ ning et al 1997), one might expect post-altitude changes in pH defense. Indeed, a short stay at moderate altitude has been shown to result in an increase in total extracellular buering capacity (BoÈ ning et al 1980).…”

Extracellular pH defense against lactic acid in untrained and trained altitude residents

“…b nbi is constant according to in vivo titrations with CO 2 (e.g. Böning et al 1999). Consequently the lines for the sum of all buffers (D[La] plasma vs. DpH nr -1 ) should be similarly curved as the bicarbonate buffer lines.…”