Dual Test Gas Pulmonary Diffusing Capacity Measurement During Exercise in Humans Using the Single-Breath Method

Summary

This protocol presents a method to assess pulmonary alveolar-capillary reserve measured by combined single-breath measurement of the diffusing capacity to carbon monoxide (D_L,CO) and nitric oxide (D_L,NO) during exercise. Assumptions and recommendations for using the technique during exercise form the foundation of this article.

Abstract

The combined single-breath measurement of the diffusing capacity of carbon monoxide (D_L,CO) and nitric oxide (D_L,NO) is a useful technique to measure pulmonary alveolar-capillary reserve in both healthy and patient populations. The measurement provides an estimate of the participant's ability to recruit and distend pulmonary capillaries. The method has recently been reported to exhibit a high test-retest reliability in healthy volunteers during exercise of light to moderate intensity. Of note, this technique permits up to 12 repeated maneuvers and only requires a single breath with a relatively short breath-hold time of 5 s. Representative data are provided showing the gradual changes in D_L,NO and D_L,CO from rest to exercise at increasing intensities of up to 60% of maximal workload. The measurement of diffusing capacity and evaluation of alveolar-capillary reserve is a useful tool to evaluate the lung's ability to respond to exercise both in the healthy population as well as in patient populations such as those with chronic lung disease.

Introduction

Exercise leads to a considerable increase in energy demand compared to the resting state. The heart and lungs respond by increasing cardiac output and ventilation resulting in an expansion of the alveolar-capillary bed, mainly the recruitment and distention of pulmonary capillaries¹. This ensures a sufficient pulmonary gas exchange, which can be measured by an increase in pulmonary diffusing capacity (D_L)^2,3,4. The first attempts to measure D_L during exercise date back more than a century^5,

Protocol

The Scientific Ethical Committee for the Capital Region of Denmark has previously approved the measurement of D_L,CO/NO at rest, during exercise, and in the supine position in both healthy volunteers and patients with chronic obstructive pulmonary disease (COPD) at our institution (protocols H-20052659, H-21021723, and H-21060230).

NOTE: Before D_L,CO/NO is measured during exercise, a dynamic spirometry, and a cardiopulmonary exercise test (CPET) must be performed. The dyna.......

Discussion

The protocol provides a standardized approach to the measurement of D_L,CO/NO during exercise using the dual test gas single-breath technique. Since the obtained D_L,CO/NO-metrics increase due to pulmonary capillary recruitment and distension, the method provides a physiologically meaningful measure of the alveolar-capillary reserve.

Critical steps in the protocol
The method requires an exhalation to residual volume followed by an inspiration to total.......

Materials

Name	Company	Catalog Number	Comments
HemoCue Hb 201+	HemoCue, Brønshøj, Denmark	Unkown	For measurements of hemoglobin
Jaeger MasterScreen PFT pro (Lung Function Equipment)	CareFusion, Höchberg, Germany	Unkown	For measurements of DLCO/NO
Mouthpiece	SpiroBac, Henrotech, Aartselaar, Belgium	Unkown	Used together with the Lung Fuction Equipment. (dead space 56 ml, resistance to flow at 12 L s−1 0.9 cmH2O)
Nose-clip	IntraMedic, Gentofte, Denmark	JAE-892895
Phenumotach	IntraMedic, Gentofte, Denmark	JAE-705048	Used together with the Lung Fuction Equipment
SentrySuite Software Solution	Vyaire's Medical GmbH, Leibnizstr. 7, D-97204 Hoechberg Germany	Unkown
Test gasses	IntraMedic, Gentofte, Denmark	Unkown	Concentrations: 0.28% CO, 20.9% O2, 69.52% N2 and 9.3% He