Difference between end-tidal and arterial PCO2 in exercise

1979 ◽  
Vol 47 (5) ◽  
pp. 954-960 ◽  
Author(s):  
N. L. Jones ◽  
D. G. Robertson ◽  
J. W. Kane
Keyword(s):  
Carbon Dioxide ◽  
Carbon Dioxide Tension ◽  
Infrared Analysis ◽  
Arterial Carbon Dioxide Tension ◽  
Arterial Pco2 ◽  
Response Characteristics ◽  
Co2 Output ◽  
End Tidal Carbon Dioxide ◽  
Power Outputs ◽  
End Tidal

The relation between end-tidal carbon dioxide tension (PETCO2) measured by infrared analysis and arterial carbon dioxide tension (PaCO2) during exercise was systematically examined in five healthy adults at two power outputs (25 and 50% VO2max) and at three frequencies of breathing (15, 30, and 45 breaths/min). PETCO2-PaCO2 varied between -2.5 and +9.1 Torr, was inversely related to the frequency of breathing (r = 0.475), and directly related to tidal volume (VT; r = 0.791) and CO2 output (r = 0.627). An equation was obtained by multiple regression analysis, to predict PaCO2 from PETCO2: PaCO2 = 5.5 +0.90 PETCO2 -0.0021 VT (r = 0.915). The equation was applied to measurements of PETCO2 obtained in two previous studies in 10 subjects in which PaCO2 had been measured, and was found to predict PaCO2 to within 1.04 Torr (+/- SD) for PaCO2 between 25 and 58 Torr (n = 56; r = 0.962). The effect of the response characteristics of the CO2 analyzer on the measurement of PETCO2 was also systematically examined by comparison with a fast-responding respiratory mass spectrometer.

scholarly journals End-tidal carbon dioxide tension reflects arterial carbon dioxide tension in the heat-stressed human with and without simulated hemorrhage

2011 ◽  
Vol 300 (4) ◽  
pp. R978-R983 ◽  
Author(s):  
R. Matthew Brothers ◽  
Matthew S. Ganio ◽  
Kimberly A. Hubing ◽  
Jeffrey L. Hastings ◽  
Craig G. Crandall
Keyword(s):  
Carbon Dioxide ◽  
Heat Stress ◽  
Lower Body Negative Pressure ◽  
Carbon Dioxide Tension ◽  
Arterial Carbon Dioxide Tension ◽  
Relevant Variable ◽  
Arterial Carbon Dioxide ◽  
End Tidal Carbon Dioxide ◽  
Simulated Hemorrhage ◽  
End Tidal

End-tidal carbon dioxide tension (PetCO2) is reduced during an orthostatic challenge, during heat stress, and during a combination of these two conditions. The importance of these changes is dependent on PetCO2 being an accurate surrogate for arterial carbon dioxide tension (PaCO2), the latter being the physiologically relevant variable. This study tested the hypothesis that PetCO2 provides an accurate assessment of PaCO2 during the aforementioned conditions. Comparisons between these measures were made: 1) after two levels of heat stress ( N = 11); 2) during combined heat stress and simulated hemorrhage [via lower-body negative pressure (LBNP), N = 8]; and 3) during an end-tidal clamping protocol to attenuate heat stress-induced reductions in PetCO2 ( N = 7). PetCO2 and PaCO2 decreased during heat stress ( P < 0.001); however, there was no group difference between PaCO2 and PetCO2 ( P = 0.36) nor was there a significant interaction between thermal condition and measurement technique ( P = 0.06). To verify that this nonsignificant trend for the interaction was not due to a type II error, PetCO2 and PaCO2 at three distinct thermal conditions were also compared using paired t-tests, revealing no difference between PaCO2 and PetCO2 while normothermic ( P = 0.14) and following a 1.0 ± 0.2°C ( P = 0.21) and 1.4 ± 0.2°C ( P = 0.28) increase in internal temperature. During LBNP while heat stressed, measures of PetCO2 and PaCO2 were similar ( P = 0.61). Likewise, during the end-tidal carbon dioxide clamping protocol, the increases in PetCO2 (7.5 ± 2.8 mmHg) and PaCO2 (6.6 ± 3.4 mmHg) were similar ( P = 0.31). These data indicate that mean PetCO2 reflects mean PaCO2 during the evaluated conditions.

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