M. Cautero

New perspectives in breath-by-breath determination of alveolar gas exchange in humans

Abstract. Alveolar gas transfer over a given breath (i) was determined in ten subjects at rest and during steady-state cycling at 60, 90 or 120xa0W as the sum of volume of gas transferred at the mouth plus the changes of the alveolar gas stores. This is given by the gas fraction (FA) change at constant volume plus the volume change (ΔVAi) at constant fraction i.e. <I>V</I><SUB>A</SUB><I><SUB>i</SUB></I><SUB>-1</SUB>(<I>F</I><SUB>A</SUB><I><SUB>i</SUB></I>-<I>F</I><SUB>A</SUB><I><SUB>i</SUB></I><SUB>-1</SUB>)+<I>F</I><SUB>A</SUB><I><SUB>i</SUB></I>·Δ<I>V</I><SUB>A</SUB><I><SUB>i</SUB></I>, where VAi–1 is the end-expiratory volume at the beginning of the breath. These quantities, except for VAi–1, can be measured on a single-breath (breath-by-breath) basis and VAi–1 set equal to the subjects functional residual capacity (FRC, Auchincloss model). Alternatively, the respiratory cycle can be defined as the interval elapsing between two equal expiratory gas fractions in two successive breaths (Grønlund model G). In this case,

Alveolar oxygen uptake kinetics with step, impulse and ramp exercise in humans

nF_{t_{rm 1} } = F_{t_{rm 2} } n

Oxygen deficits and oxygen delivery kinetics during submaximal intensity exercise in humans after 14 days of head-down tilt-bed rest

n and thus the term VAi–1 (FAi–FAi–1) vanishes. In the present study, average alveolar O2 uptake (

Cardiac output, O2 delivery and V˙O2 kinetics during step exercise in acute normobaric hypoxia

nmathop Vlimits^ bullet {rm O}_{{rm 2}{rm ,A}} n

Pulmonary [Formula: see text] kinetics at the onset of exercise is faster when actual changes in alveolar O2 stores are considered.

n) and CO2 output (