Comparison of arterial,end-tidal and transcutaneous PCO2 during moderate exercise and external C02 loading in humans |
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Authors: | U Hoffmann D Eßfeld J Stegemann |
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Institution: | (1) Physiologisches Institut der Deutschen Sporthochschule Köln, Carl-Diem-Weg 6, D-5000 Cologne 41, Germany |
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Abstract: | Summary Static relationships between arterial, transcutaneous/p] and end-tidal PCO2 (P
aCO2, P
tc
CO
2, P
etCO2) as well as the dynamic relationship between P
etCO2 and P
tcCO2 were studied during moderate bicycle ergometer exercise with and without external C02 loading. The exercise pattern consisted of 5-min intervals of constant power at 40 W and 100 W and 900 s of randomised changes between these two power levels. The external CO2 loading was achieved by means of controlled variations of inspiratory gas compositions aimed at a constant P
etCO2 of 6.5 kPa (49 mm Hg). The PetO2 was regulated at 17.3 kPa (130 mm Hg). Under steady-state conditions all PCO2 parameters showed close linear relationships. P
aCO2/P
tcCO2 was near to identity while the P
etCO2 systematically overestimated changes in P
aCO2. No relationship showed a significant influence of the exercise intensity. Transients of P
tcCO2 are considerably slower than P
etCO2 transients. The dynamic relationship between both parameters was found to be independent of whether internal or external C02 loadings were applied. It is concluded that the combination of P
etCO2 and P
tcCO2 measurements allows an improved non-invasive assessment of P
aCO2. While P
etC02 better reflects the transients, P
tcCO2 can be employed to determine slow changes of the absolute P
aCO2. |
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Keywords: | Arterial PCO2 Transcutaneous PCO2 End-tidal PCO2 Moderate exercise External C02 loading |
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