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Pulmonary Physiology |

Correlation of Diffusion Capacity With Gas Exchange Parameters on Cardiopulmonary Exercise Testing in Obese Patients With Exertional Dyspnea

Aaron Glucksman, MD; Antranik Mangardich, MD; Debapriya Datta, MD
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University of CT Health Center, Farmington, CT


Chest. 2015;148(4_MeetingAbstracts):899A. doi:10.1378/chest.2270252
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Abstract

SESSION TITLE: Pulmonary Physiology Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM

PURPOSE: Obesity affects both resting and exercise-related respiratory physiology. Obese individuals may have impaired diffusing capacity (DLCO) but diffusion capacity adjusted for alveolar volume (DLCOalv), which is adjusted for weight, is usually normal. As V/Q relationships usually normalize during exercise in obese patients, exercise-related gas exchange parameters such as ventilatory equivalent for carbon dioxide (Ve/VCO2) or oxygen (VE/VO2) at anaerobic threshold and dead space-tidal volume ratio (Vd/Vt) are reported to be normal in obesity. How DLCO and DLCOalv correlate with gas exchange parameters during exercise in obesity has not been studied. The objective of this study was to compare DLCO and DLCOalv with VE/VO2, VE/VCO2, and Vd/Vt at rest and exercise during CPExT.

METHODS: Records of patients who underwent CPExT for evaluation of dyspnea in our exercise test laboratory were reviewed. Patients with BMI> 30, who had pulmonary function tests (PFTs) available, were included in the study. Parameters obtained from records included: age, gender, DLCO (%Predicted) and DLCOalv (%Predicted) from PFTs; VE/VO2, VE/VCO2; Vd/Vt at rest and exercise on CPExT. Correlation between DLCO and DLCOalv respectively with VE/VO2, VE/VCO2, Vd/Vt at rest and Vd/Vt with exercise was determined by using Pearson’s test for linear correlation. p < 0.05 was deemed statistically significant.

RESULTS: Of 58 patients with BMI > 30, who underwent CPExT, 57% were females; mean age was 55+ 13 years. Mean BMI was: 36+ 5 kg/sqm. Mean DLCO was75 + 20; mean DLCOalv was 108 + 26. The correlation coefficient (r) between studied parameters and their statistical significance are shown below: DLCO (%predicted) vs.Vd/Vt Rest ⇒ r = -0.088; p=0.5 DLCO (%predicted) vs. Vd/Vt Exercise⇒ r = -0.505; p = <0.001 DLCO (%predicted) vs.VE/VO2 ⇒r = -0.09; p = 0.5 DLCO (%predicted) vs.VE/VCO2 ⇒ r = -0.062; p = 0.68 DLCOalv (%predicted) vs.Vd/Vt Rest ⇒ r = -0.262; p=0.09 DLCOalv (%predicted) vs.Vd/Vt Exercise ⇒ r = -0.402; p=0.008 DLCOalv (%predicted) vs.VE/VO2 ⇒r = -0.377; p = 0.01 DLCOalv (%predicted) vs.VE/VCO2 ⇒ r = -0.419; p = 0.004.

CONCLUSIONS: In obese subjects, DLCOalv has a significant correlation with VE/VO2, VE/VCO2, and Vd/Vt at exercise. DLCO correlates only with Vd/Vt at exercise.

CLINICAL IMPLICATIONS: DLCOalv is a better indicator of gas exchange abnormalities than DLCO in obese patients.

DISCLOSURE: The following authors have nothing to disclose: Aaron Glucksman, Antranik Mangardich, Debapriya Datta

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