The Ability of Volumetric Capnography to Distinguish between Chronic Obstructive Pulmonary Disease Patients and Normal Subjects

Qi, Guang-sheng; Gu, Wenchao; Yang, Wenlan; Feng, Xiaoqin; Wu, Hao

doi:10.1007/s00408-014-9615-4

Cited by 15 publications

(6 citation statements)

References 30 publications

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“…The three additional parameters are also plausible from the pathophysiological point of view. As discussed above, the slope of phase 3 is closely related to the inhomogeneity of ventilation, which is linked to obstruction particularly in COPD [25, 26]. The same applied to the ratio of area to volume in phase 3, since, by definition, the area obtained by integrating the CO 2 concentration over volume represents a total amount of exhaled CO 2 due to inhomogeneity and thus the ratio to volume an average CO 2 concentration change due to inhomogeneity.…”

Section: Discussionmentioning

confidence: 99%

Diagnostic accuracy of capnovolumetry for the identification of airway obstruction – results of a diagnostic study in ambulatory care

et al. 2019

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Background One of the known weaknesses of spirometry is its dependence on patients’ cooperation, which can only partially be alleviated by educational efforts. Therefore, procedures less dependent on cooperation might be of value in clinical practice. We investigated the diagnostic accuracy of ultrasound-based capnovolumetry for the identification of airway obstruction. Methods Consecutive patients from a pulmonary outpatient clinic were included in the diagnostic study. As reference standard, the presence of airway obstruction was evaluated via spirometry and bodyplethysmography. Capnovolumetry was performed as index test with an ultrasound spirometer providing a surrogate measure of exhaled carbon dioxide. Receiver operating characteristic (ROC) analysis was performed using the ratio of slopes of expiratory phases 3 and 2 (s3/s2) ≥ 0.10 as primary capnovolumetric parameter for the recognition of airway obstruction. Logistic regression was performed as secondary analysis to identify further useful capnovolumetric parameters. The diagnostic potential of capnovolumetry to identify more severe degrees of airway obstruction was evaluated additionally. Results Of 1400 patients recruited, 1287 patients were included into the analysis. Airway obstruction was present in 29% of patients. The area under the ROC-curve (AUC) of s3/s2 was 0.678 (95% CI 0.645, 0.710); sensitivity of s3/s2 ≥ 0.10 was 47.7 (95% CI 42.7, 52.8)%, specificity 79.0 (95% CI 76.3, 81.6)%. When combining this parameter with three other parameters derived from regression analysis (ratio area/volume phase 3, slope phase 3, volume phase 2), an AUC of 0.772 (95% CI 0.743, 0.801) was obtained. For severe airway obstruction (FEV 1 ≤ 50% predicted) sensitivity of s3/s2 ≥ 0.10 was 75.9 (95% CI 67.1, 83.0)%, specificity 75.8 (95% CI 73.3, 78.1)%; for very severe airway obstruction (FEV 1 ≤ 30% predicted) sensitivity was 86.7 (95% CI 70.3, 94.7)%, specificity 72.8 (95% CI 70.3, 75.2)%. Sensitivities increased and specificities decreased considerably when the combined capnovolumetric score was used as index test. Conclusions Capnovolumetry by way of an ultrasound spirometer had a statistically significant albeit moderate potential for the recognition of airway obstruction in a heterogeneous population of patients typically found in clinical practice. Diagnostic accuracy of the capnovolumetric device increased with the severity of airway obstruction. Trial registration The study is registered under DRKS00013935 at German Clinical Trials Register (DRKS).

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Section: Discussionmentioning

confidence: 99%

Diagnostic accuracy of capnovolumetry for the identification of airway obstruction – results of a diagnostic study in ambulatory care

et al. 2019

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“…Most previous studies are based on limited information from the SBT CO 2 such as slope of Phase II and/or the slope of the alveolar plateau, Phase III. 11 , 19 – 21 Analysis of slope, the derivative of a mathematical function, is inherently sensitive to signal noise. The alveolar plateau is upward convex rather than linear and minor variation in the algorithm may lead to large variation in calculated slope.…”

Section: Discussionmentioning

confidence: 99%

The Efficiency Index (EFFi), based on volumetric capnography, may allow for simple diagnosis and grading of COPD

Jarenbäck

Tufvesson

Ankerst

et al. 2018

COPD

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BackgroundSpirometry, the main tool for diagnosis and follow-up of COPD, incompletely describes the disease. Based on volumetric capnography (VCap), an index was developed for the diagnosis and grading of COPD, aimed as a complement or alternative to spirometry.MethodsNine non-smokers, 10 smokers/former smokers without COPD and 54 smokers/former smokers with COPD were included in the study. Multiple breath washout of N2 and VCap were studied with Exhalyzer D during tidal breathing. VCap was based on signals for flow rate and CO2 and was recorded during one breath preceding N2 washout. Efficiency Index (EFFi) is the quotient between exhaled CO2 volume and the hypothetical CO2 volume exhaled from a completely homogeneous lung over a volume interval equal to 15% of predicted total lung capacity.ResultsEFFi increased with increased Global initiative for chronic Obstructive Lung Disease (GOLD) stage and the majority of subjects in GOLD 2 and all subjects in GOLD 3 and 4 could be diagnosed as having COPD using the lower 95% confidence interval of the healthy group. EFFi also correlated with N2 washout (r=−0.73; p<0.001), forced expiratory volume in 1 second (r=0.70; p<0.001) and diffusion capacity for carbon oxide (r=0.69; p<0.001).ConclusionEFFi measures efficiency of tidal CO2 elimination that is limited by inhomogeneity of peripheral lung function. EFFi allows diagnosis and grading of COPD and, together with FEV1, may explain limitation of physical performance. EFFi offers a simple, effortless and cost-effective complement to spirometry and might serve as an alternative in certain situations.

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“…This slope has been shown to reflect the inhomogeneity of alveolar ventilation, with increased values indicative of increased inhomogeneity [19,20]. Among the indices from body plethysmography and spirometry, it corresponded best to the ratio RV/TLC, a well-known measure of lung hyperinflation.…”

Section: Slope Of Expiratory Phasementioning

confidence: 99%

Correspondence between Capnovolumetric and Conventional Lung Function Parameters in the Diagnosis of Obstructive Airway Diseases

et al. 2020

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Background: Capnovolumetry is of interest as a method for the diagnosis of obstructive airway diseases, requiring little cooperation from the patient. Objective: To help in the interpretation of capnovolumetric parameters, we aimed to identify their correspondence to conventional lung function indices. Methods: We studied 978 patients from a diagnostic study with complete functional data and the clinical diagnosis of asthma, chronic obstructive pulmonary disease (COPD), or no respiratory disease. Using path analysis, four capnovolumetric parameters (slope of expiratory phase 3, ratio of slopes of phases 3 and 2, volume of phase 2, and the ratio area/volume of phase 3) previously identified as predictors of airway obstruction in terms of spirometry and body plethysmography, were analyzed regarding their relationship to each other and the diagnostic categories of asthma or COPD versus control, or obstruction versus no obstruction. We then identified four lung function parameters showing relationships as much as possible isomorphic to those between capnovolumetric parameters. Results: The four capnovolumetric parameters were related to COPD and obstruction via both direct and indirect influences, but only two of them to asthma. Regarding the correspondence to lung function parameters, the slope of expiratory phase 3 corresponded best to the ratio of residual volume to total lung capacity, the ratio of slopes of phases 3 and 2 to forced expiratory volume in 1 s, the volume of phase 2 to forced expired flow at 50% of vital capacity, and the ratio area/volume of phase 3 to forced vital capacity. Conclusions: Our results indicated an intricate relationship of capnovolumetric parameters to each other and to airway obstruction, asthma, or COPD. The correspondence to conventional lung function measures seemed to reflect the entities lung hyperinflation, overall ventilatory impairment, bronchoconstriction, and ventilated lung volume, in that order. These findings might be helpful for clinicians in the interpretation of capnovolumetry.

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The Ability of Volumetric Capnography to Distinguish between Chronic Obstructive Pulmonary Disease Patients and Normal Subjects

Cited by 15 publications

References 30 publications

Diagnostic accuracy of capnovolumetry for the identification of airway obstruction – results of a diagnostic study in ambulatory care

Diagnostic accuracy of capnovolumetry for the identification of airway obstruction – results of a diagnostic study in ambulatory care

The Efficiency Index (EFFi), based on volumetric capnography, may allow for simple diagnosis and grading of COPD

Correspondence between Capnovolumetric and Conventional Lung Function Parameters in the Diagnosis of Obstructive Airway Diseases

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