Source: Annual Congress 2002 - Monitoring respiratory parameters in critically ill patients
Disease area: Airway diseases, Respiratory critical care

Abstract

Purpose: To investigate the possibility of estimating PaCO₂ with the measurement of expired gas PCO₂ at end expiration using the prolonged expiration method in COPD patients. Sujects and methods: 16 severe COPD patients admitted into the hospital because of acute exacerbation were recruited for the study. Expired PCO₂ was measured with NOVAMETRIC CO₂ monitoring system (Novametric Co, USA). Immediately after measurement of PaCO₂, P_ETCO₂ was measured with tidal breathing (P_ETCO₂(T) )and prolonged expiration (more than 5 seconds) methods (P_ETCO₂(P)). The relationship between PaCO₂, P_ETCO₂(T) and P_ETCO₂(P) was analyzed. Follow-up measurements were repeated 4-7 days later in order to evaluate the relationship between the change in PaCO₂, and P_ETCO₂(P). Result: The P_ETCO₂ was dynamically related to the expiratory time in COPD. P_ETCO₂ at 5 seconds after the start of expiration was read as P_ETCO₂(P). The mean difference between the P_ETCO₂(T) and PaCO₂ was 11.7±]8.3mmHg (P<0.05); On the other hand, the mean difference between P_ETCO₂(P) and PaCO₂ was only 0.7±]2.7mmHg(P=0.89). The average PaCO₂ was 60.6±]14.6mmHg and P_ETCO₂(P) was 59.9±]13.9mmHg. By linear regression analysis, P_ETCO₂(P) was very closely related to PaCO₂ (Ratio=0.94, R=0.98, SD=2.6). In the follow-up measurement, the mean reduction of PaCO₂ was 3.0±]8.7mmHg and P_ETCO₂(P) was 5.9±]9.6mmHg. There was close correlation between the change of PaCO₂ and P_ETCO₂(P) (Ratio=0.77, R=0.86, SD= 4.65,P<0.0001). Conclusion: With prolonged expiration method, P_ETCO₂ (P) could reliably estimate the PaCO₂ and reflect the change of PaCO₂, which will provide an valuable non-invasive method for monitoring PaCO₂ in COPD patients.

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Citations should be made in the following way:
D. Li, Z. Zheng, P. Lin, X. Zhang, R. Chen (Guangzhou, China). Prolonged end expiration CO₂ measurement provides valuable estimation of PaCO₂ in COPD. Eur Respir J 2002; 20: Suppl. 38, 629

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