Abstract
RationaleThe diffusing capacity (DL) of the lung can be divided into two components: the diffusing capacity of the alveolar membrane (Dm) and the pulmonary capillary volume (Vc). DL is traditionally measured using a single-breath method, involving inhalation of carbon monoxide, and a breath hold of 8–10 seconds (DL,CO). This method does not easily allow calculation of Dm and Vc. An alternative single-breath method (DL,CO,NO), involving simultaneous inhalation of carbon monoxide and nitric oxide, and traditionally a shorter breath hold, allows calculation of Dm and Vc and the DL,NO/DL,CO ratio in a single respiratory maneuver. The clinical utility of Dm, Vc, and DL,NO/DL,CO in the pediatric age range is currently unknown but also restricted by lack of reference values.ObjectivesThe aim of this study was to establish reference ranges for the outcomes of DL,CO,NO with a 5 second breath hold, including the calculated outcomes Dm, Vc, and the DL,NO/DL,CO ratio, as well as to establish reference values for the outcomes of the traditional DL,CO method, with a 10 second breath hold in children.MethodsDL,CO,NO and DL,CO were measured in healthy children, of European descent, aged 5–17 years using a Jaeger Masterscreen PFT. The data were analyzed using the Generalized Additive Models for Location Scale and Shape (GAMLSS) statistical method.Measurements and Main ResultsA total of 326 children were eligible for diffusing capacity measurements, resulting in 312 measurements of DL,CO,NO and 297 of DL,CO, respectively. Reference equations were established for the outcomes of DL,CO,NO and DL,CO, including the calculated values: Vc, Dm, and the DL,NO/DL,CO ratio.ConclusionThese reference values are based on the largest sample of children to date and may provide a basis for future studies of their clinical utility in differentiating between alterations in the pulmonary circulation and changes in the alveolar membrane in pediatric patients.
Highlights
The transfer factor of the lung for a gas, is often called the diffusing capacity of the lung (DL)
DL,carbon monoxide (CO),NO5s and DL,CO,10s were performed according to current ATS/ERS guidelines [2], though we considered a ratio between inspiratory volume and FVC (VIN/FVC) .80% as sufficient, in contrast to a ratio .85%
This study is the first to create pediatric reference equations for the outcomes DL,CO,5s, DL,nitric oxide (NO), and the calculated outcomes DL,NO/DL,CO,5s, Vc, and Dm measured by DL,CO,NO,5s in healthy children and adults, of European descent
Summary
The transfer factor of the lung for a gas, is often called the diffusing capacity of the lung (DL). DL for an inhaled gas reactive with hemoglobin is the flow of that gas from the alveoli to the blood for a unit difference in pressure. DL can be divided into two components: the diffusing capacity of the pulmonary membrane (Dm) and the chemical reaction of the gas binding to the blood. The latter is determined by the specific conductance of blood for a given gas, H, and the capillary volume of the lung (Vc). The single-breath method was first introduced in 1915 [1]. The singlebreath DL of carbon monoxide (CO) using a breath-hold of 10 seconds (DL,CO,10s) is the most frequently used method with the current ATS/ERS methodological guidelines [2]
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