Related Experiment Video
Updated: Jan 21, 2026

Continuous Venous-Arterial Doppler Ultrasound During a Preload Challenge
Published on: January 20, 2023
Comparison of End-Tidal, Arterial, Venous, and Transcutaneous PCO
Shota Fujimoto1, Manabu Suzuki2, Keita Sakamoto1
1Department of Respiratory Medicine, National Center for Global Health and Medicine, Tokyo, Japan.
Background:
We investigated the measurement of end-tidal partial pressure of carbon dioxide (PETCO ) with a capnometer in patients with respiratory failure, and we determined whether this technique could provide an alternative to measurement of PaCO using arterial blood gas analysis in the clinical setting.
Methods:
We measured PETCO in subjects with hypoxemic and hypercarbic respiratory failure using a capnometer. We simultaneously measured PaCO , venous partial pressure of carbon dioxide (Pv̄CO ), and transcutaneously measured partial pressure PCO (PtcCO ). We analyzed agreements among these parameters with Bland-Altman analysis. We obtained 30 samples from subjects with hypoxemic respiratory failure and 30 samples from subjects with hypercarbic respiratory failure.
Results:
Thirty subjects with hypoxemic respiratory failure and 18 subjects with hypercarbic respiratory failure participated in this study. Significant relationships were found between PETCO and PaCO , between PtcCO and PaCO , and between Pv̄CO and PaCO . Bland-Altman analysis of PETCO and PaCO in all subjects revealed a bias of 6.48 mm Hg (95% CI 4.93-8.03, P < .001) with a precision of 6.01 mm Hg. Bland-Altman analysis of PETCO and PaCO with hypoxemic respiratory failure revealed a bias of 5.14 mm Hg (95% CI 3.35-6.93, P < .001) with a precision of 4.80 mm Hg. Bland-Altman analysis of PETCO and PaCO in subjects with hypercarbic respiratory failure revealed a bias of 7.83 mm Hg (95% CI 5.27-10.38, P < .001) with a precision of 6.83 mm Hg.
Conclusions:
PETCO can be measured simply using a capnometer, and PETCO measurements can estimate PaCO . However, the limits of agreement were wide. Therefore, care providers must pay attention to the characteristics and errors of these devices. These results suggest that measurement of PETCO might be useful for screening for hypercarbic respiratory failure in the clinical setting.
Related Concept Videos
Tidal Forces
Venous Return
What is Venous Return?
Venous return refers to the rate at which blood flows back to the heart from the body's peripheral veins. It's an integral part of the circulatory system...
The Sense of Self: Reflected Self-Appraisal and Social Comparison
Venous Thrombosis I: Introduction
Multiple Comparison Tests
It would be easy to compare two samples using a significance alpha level of 0.05. In other words, there is only one sample pair to be compared. However, it would be difficult to identify a significantly different sample if the number...
Evolutionary Relationships through Genome Comparisons

