Abstract
Background: Exact and simultaneous measurements of mean pulmonary artery pressure (mPAP) and cardiac output (CO) are crucial to calculate pulmonary vascular resistance (PVR), which is essential to define pulmonary hypertension (PH). Simultaneous measurements of mPAP and CO are not feasible using the direct Fick (DF) method, due to the necessity to sample blood from the catheter-tip. We evaluated a modified DF method, which allows simultaneous measurement of mPAP and CO without needing repetitive blood samples.Methods: Twenty-four patients with pulmonary arterial or chronic thromboembolic PH had repetitive measurements of CO at rest and end-exercise during three phases of a crossover trial. CO was assessed by the original DF method using oxygen uptake, measured by a metabolic unit, and arterial and mixed venous oxygen saturations from co-oximetry of respective blood gases served as reference. These CO measurements were then compared with a modified DF method using pulse oximetry at the catheter- and fingertip.Results: The bias among CO measurements by the two DF methods at rest was −0.26 L/min with limits of agreement of ±1.66 L/min. The percentage error was 28.6%. At the end-exercise, the bias between methods was 0.29 L/min with limits of agreement of ±1.54 L/min and percentage error of 16.1%.Conclusion: Direct Fick using a catheter- and fingertip pulse oximetry (DFp) is a practicable and reliable method for assessing CO in patients with PH. This method has the advantage of allowing simultaneous measurement of PAP and CO, and frequent repetitive measurements are needed during exercise.Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT02755259, identifier: NCT02755259.
Highlights
In the absence of relevant lung diseases, the two major forms of precapillary pulmonary hypertension (PH) are pulmonary arterial and chronic thromboembolic pulmonary hypertension (PAH/CTEPH)
Direct Fick using a catheter- and fingertip pulse oximetry (DFp) is a practicable and reliable method for assessing cardiac output (CO) in patients with PH. This method has the advantage of allowing simultaneous measurement of PAP and CO, and frequent repetitive measurements are needed during exercise
The main aim of this study was to evaluate the precision and accuracy of CO measured by direct Fick (DF) using a catheter and fingertip pulse oximetry (DFp) in comparison to DF using oxygen saturation derived by co-oximetry from blood gases (DF), at rest and at end-exercise in patients with PH
Summary
In the absence of relevant lung diseases, the two major forms of precapillary pulmonary hypertension (PH) are pulmonary arterial and chronic thromboembolic pulmonary hypertension (PAH/CTEPH). To calculate the PVR, simultaneous measurement of cardiac output (CO) and mPAP is necessary [6]. Inaccuracy and imprecision of CO measurement techniques can lead to misdiagnosis or inadequate treatment decisions. These aspects highlight the relevance of reliable CO measurements at rest, and during vasoreactivity testing and exercise challenge at the time of diagnosis or during followup of patients with PH to evaluate effects of therapy and prognosis [8]. Exact and simultaneous measurements of mean pulmonary artery pressure (mPAP) and cardiac output (CO) are crucial to calculate pulmonary vascular resistance (PVR), which is essential to define pulmonary hypertension (PH). We evaluated a modified DF method, which allows simultaneous measurement of mPAP and CO without needing repetitive blood samples
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