Dataset Information

End-tidal to arterial PCO₂ ratio: a bedside meter of the overall gas exchanger performance.

ABSTRACT:

Background

The physiological dead space is a strong indicator of severity and outcome of acute respiratory distress syndrome (ARDS). The "ideal" alveolar PCO₂, in equilibrium with pulmonary capillary PCO₂, is a central concept in the physiological dead space measurement. As it cannot be measured, it is surrogated by arterial PCO₂ which, unfortunately, may be far higher than ideal alveolar PCO₂, when the right-to-left venous admixture is present. The "ideal" alveolar PCO₂ equals the end-tidal PCO₂ (P_ETCO₂) only in absence of alveolar dead space. Therefore, in the perfect gas exchanger (alveolar dead space = 0, venous admixture = 0), the P_ETCO₂/PaCO₂ is 1, as P_ETCO₂, P_ACO₂ and PaCO₂ are equal. Our aim is to investigate if and at which extent the P_ETCO₂/PaCO₂, a comprehensive meter of the "gas exchanger" performance, is related to the anatomo physiological characteristics in ARDS.

Results

We retrospectively studied 200 patients with ARDS. The source was a database in which we collected since 2003 all the patients enrolled in different CT scan studies. The P_ETCO₂/PaCO₂, measured at 5 cmH₂O airway pressure, significantly decreased from mild to mild-moderate moderate-severe and severe ARDS. The overall populations was divided into four groups (~ 50 patients each) according to the quartiles of the P_ETCO₂/PaCO₂ (lowest ratio, the worst = group 1, highest ratio, the best = group 4). The progressive increase P_ETCO₂/PaCO₂ from quartile 1 to 4 (i.e., the progressive approach to the "perfect" gas exchanger value of 1.0) was associated with a significant decrease of non-aerated tissue, inohomogeneity index and increase of well-aerated tissue. The respiratory system elastance significantly improved from quartile 1 to 4, as well as the PaO₂/FiO₂ and PaCO₂. The improvement of P_ETCO₂/PaCO₂ was also associated with a significant decrease of physiological dead space and venous admixture. When PEEP was increased from 5 to 15 cmH₂O, the greatest improvement of non-aerated tissue, PaO₂ and venous admixture were observed in quartile 1 of P_ETCO₂/PaCO₂ and the worst deterioration of dead space in quartile 4.

Conclusion

The ratio P_ETCO₂/PaCO₂ is highly correlated with CT scan, physiological and clinical variables. It appears as an excellent measure of the overall "gas exchanger" status.

SUBMITTER: Bonifazi M

PROVIDER: S-EPMC8054233 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:The purpose of the study was to evaluate the behavior of the venous-to-arterial CO2 tension difference (ΔPCO2) over the arterial-to-venous oxygen content difference (ΔO2) ratio (ΔPCO2/ΔO2) and the difference between venous-to-arterial CO2 content calculated with the Douglas' equation (ΔCCO2D) over ΔO2 ratio (ΔCCO2D/ΔO2) and their abilities to reflect the occurrence of anaerobic metabolism in two experimental models of tissue hypoxia: ischemic hypoxia (IH) and hypoxic hypoxia (HH). We also aimed to assess the influence of metabolic acidosis and Haldane effects on the PCO2/CO2 content relationship. In a vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system, the oxygen delivery (DO2) was lowered in a stepwise manner to decrease it beyond critical DO2 (DO2crit) by lowering either arterial PO2 (HH-model) or flow (IH-model). Twelve anesthetized and mechanically ventilated dogs were studied, 6 in each model. Limb DO2, oxygen consumption ([Formula: see text]), ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 were obtained every 15 min. Beyond DO2crit, [Formula: see text] decreased, indicating dysoxia. ΔPCO2/ΔO2, and ΔCCO2D/ΔO2 increased significantly only after reaching DO2crit in both models. At DO2crit, ΔPCO2/ΔO2 was significantly higher in the HH-model than in the IH-model (1.82 ± 0.09 vs. 1.39 ± 0.06, p = 0.002). At DO2crit, ΔCCO2D/ΔO2 was not significantly different between the two groups (0.87 ± 0.05 for IH vs. 1.01 ± 0.06 for HH, p = 0.09). Below DO2crit, we observed a discrepancy between the behavior of the two indices. In both models, ΔPCO2/ΔO2 continued to increase significantly (higher in the HH-model), whereas ΔCCO2D/ΔO2 tended to decrease to become not significantly different from its baseline in the IH-model. Metabolic acidosis significantly influenced the PCO2/CO2 content relationship, but not the Haldane effect. ΔPCO2/ΔO2 was able to depict the occurrence of anaerobic metabolism in both tissue hypoxia models. However, at very low DO2 values, ΔPCO2/ΔO2 did not only reflect the ongoing anaerobic metabolism; it was confounded by the effects of metabolic acidosis on the CO2-hemoglobin dissociation curve, and then it should be interpreted with caution.

Dataset Information

End-tidal to arterial PCO₂ ratio: a bedside meter of the overall gas exchanger performance.

Background

Results

Conclusion

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Dataset Information

End-tidal to arterial PCO2 ratio: a bedside meter of the overall gas exchanger performance.

Background

Results

Conclusion

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

End-tidal to arterial PCO₂ ratio: a bedside meter of the overall gas exchanger performance.