Measurement of arterial blood gases at the transition from exercise to rest

Abstract

Arterial blood gas samples obtained 5-20 s after stair-climbing exercise were compared with samples taken during the last 30 s of exercise in 137 subjects. Arterial partial pressure of CO2 (PaCO2) did not change significantly, and in 110 subjects the two samples were within the analytical variation (+/- 2 Torr), supporting the cardiodynamic hypothesis of respiratory regulation. Exceptions to this response were 10 subjects who hyperventilated (PaCO2 less than 34) during exercise and 15 with severe obstruction [forced expiratory volume in 1 s (FEV1) less than 70% forced vital capacity (FVC), and FVC less than 70% of predicted] in whom PaCO2 increased significantly. Overall, arterial partial pressure of O2 (PaO2) increased an average of 3.49 Torr (P less than 0.001). In the two groups in which PaCO2 increased, postexercise PaO2 did not rise. In addition, duration of exercise affected PaO2 response. PaO2 increased significantly more after brief (less than 2 min) periods than after longer (4-6 min) exercise, and this difference increased only when subjects with normal or borderline ventilatory function were analyzed. In 13 subjects in whom a second sample was taken 30-45 s after exercise, the increase in PaO2 was progressive and again the difference between short and long exercise was evident. Regulation of respiration to maintain PaCO2 and changes in O2-CO2 kinetics, leading to an increase in the gas exchange ratio at the exercise-rest transition, are the most likely explanations of these data which establish that the usual response to stopping exercise in normal subjects and most patients is an unchanged PaCO2 and a variable increase in PaO2.

Increased physiological dead space at exercise is a marker of mild pulmonary or cardiovascular disease in dyspneic subjects

“…VD/Vt values in the No Disease group were high in comparison with previous reports [39]. Although the PaCO 2 kinetics immediately following maximal incremental exercise are not known, in a previous study PaCO 2 increased in 25 of 137 subjects following stair climbing exercise [40]. Thus, we suspect that slight asynchrony between the moment mean expired CO 2 was determined (i.e.…”

A Novel Non-invasive Index of Cardiopulmonary Reserve for the Prediction of Failure of Weaning From Mechanical Ventilation

“…We already know that partial pressure of mixed venous CO 2 (PvCO 2 ) is proportional to the VCO 2 [ 10 ]. The apparent question on the implementation of PvCO 2 instead of the veno-arterial CO 2 difference (PvCO 2 -PaCO 2 ) as an indicator of CO 2 production and exhalation (taking the place of VCO 2 in the ratio) is answered by previous data suggesting that the partial pressure of arterial CO 2 (PaCO 2 ) remains stable during exercise [ 11 ] in contrast with PvCO 2 and VCO 2 that steadily increase during exercise, to a total degree of two times and 16 times, respectively, from rest to peak exercise [ 9 ].…”

“…So the suggested modified index (Mod-RER) that we propose could be: Studies regarding blood partial pressures of O 2 and CO 2 during exercise showed that indeed PvCO 2 is steadily increased, both before and after the anaerobic threshold, following the increase in CO 2 production and expulsion [10]. PaO 2 is slightly increased immediately at the beginning of exercise [11] and as the effort escalates towards the maximum, the PaO 2 values return close to the rest levels [14]. And finally, PvO 2 values do decrease during exercise [15,16] stabilizing at the lowest levels before the advent of anaerobic metabolism without further reduction [17].…”