![]() Oxygen saturation as measured by pulse oximetry Oxygen saturation of the hemoglobin of arterial blood The term formerly used ( A-a D O 2) is discouraged.Īlveolar-arterial tension ratio P aO 2: P AO 2 The term oxygen exchange index describes this ratio. All rights reserved.Inhaled air not part of gas exchange Blood gas, acid-base, and gas exchange terms P aO 2Īrterial oxygen tension, or partial pressureĪlveolar oxygen tension, or partial pressureĪrterial carbon dioxide tension, or partial pressureĪlveolar carbon dioxide tension, or partial pressureĪlveolar-arterial oxygen tension difference. n°: NCT02201875.Īlveolar ventilation Breathing instability Control of ventilation Dead space Exercise Hypoxia Periodic breathing.Ĭopyright © 2017 Elsevier B.V. It also points out that alveolar ventilation remains very close to metabolic needs and is not affected by an added dead space. This underlines opposite effects observed in heart failure patients and normal subjects, in which added dead space drastically reduced periodic breathing and sleep apneas. These results confirmed our previous model, showing an exacerbation of breathing instability by increasing dead space. ![]() aDS also increased V˙E (P<0.001), tidal volume (VT, P<0.001), and slightly augmented PETCO 2 (P<0.05) and the respiratory frequency (P<0.05). Ventilatory oscillations (V˙E peak power) were augmented by exercise, hypoxia and aDS (P<0.001, P<0.001 and P<0.01, respectively) whereas V˙E period was only shortened by exercise (P<0.001), with an 11-s period. Ten healthy subjects performed mild exercise on a cycloergometer in different conditions: rest/exercise, normoxia/hypoxia and no added dead space/added dead space (aDS). ![]() A mathematical model including mass balance equations confirmed the short period of ventilatory oscillations and pointed out an important role of dead space in the genesis of these phenomena. ![]() Recent studies have shown that normal subjects exhibit periodic breathing when submitted to concomitant environmental (hypoxia) and physiological (exercise) stresses. ![]()
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