, Volume 103, Issue 6, pp 727-732
Date: 03 Jun 2008

End-tidal pressure of CO2 and exercise performance in healthy subjects

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High arterial CO2 pressure (P aCO2) measured in athletes during exercise suggests inadequate hyperventilation. End-tidal CO2 pressure (P ETCO2) is used to estimate P aCO2. However, P ETCO2 also depends on exercise intensity (CO2 production, \( \dot V{\text{CO}}_2 \) ) and ventilation efficiency (being P ETCO2 function of respiratory rate). We evaluated P ETCO2 as a marker, which combines efficiency of ventilation and performance. A total of 45 well-trained volunteers underwent cardiopulmonary tests and were grouped according to P ETCO2 at respiratory compensation (RC): Group 1 (P ETCO2 35.1–41.5 mmHg), Group 2 (41.6–45.7) and Group 3 (45.8–62.6). At anaerobic threshold, RC and peak exercise, ventilation ( \( \dot V{\text{E}} \) ) was similar, but in Group 3, a greater tidal volume (Vt) and lower respiratory rate (RR) were observed. Peak exercise workload and \( \dot V{\text{O}}_2 \) were lowest in Group 1 and similar between Group 2 and 3. Group 3 subjects also showed high peak \( \dot V{\text{CO}}_2 \) suggesting a greater glycolytic metabolism. In conclusion, a high P ETCO2 during exercise is useful in identifying a specific respiratory pattern characterized by high tidal volume and low respiratory rate. This respiratory pattern may belong to subjects with potential high performance.