Relationship between the baseline alveolar volume‐to‐total lung capacity ratio and airway responsiveness
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Abstract Background and objective Ventilation heterogeneity ( VH ) has been linked to airway responsiveness ( AR ) based on various measures of VH involving inert gas washout, forced oscillation and lung imaging. We explore whether VH at baseline, as measured by the simple ratio of single breath alveolar volume to plethysmographically determined total lung capacity ( VA / TLC ), would correlate with AR as measured by methacholine challenge testing. Methods We analysed data from spirometry, lung volumes, diffusing capacity and methacholine challenge to derive the VA / TLC and the dose–response slope ( DRS ) of forced expiratory volume in 1 s ( DRS ‐ FEV 1) during methacholine challenge from 136 patients. We separated out airway closure versus narrowing by examining the DRS for forced vital capacity ( DRS‐FVC ) and the DRS for FEV 1/ FVC ( DRS ‐ FEV 1/ FVC ), respectively. Similarly, we calculated the DRS for s G aw ( DRS ‐s G aw) as another measure of airway narrowing. We performed statistical analysis using Spearman rank correlation and multifactor linear regression using a backward stepwise modelling procedure. Results We found that the DRS ‐ FEV 1 correlated with baseline VA / TLC (rho = −0.26, P < 0.01), and VA / TLC and FEV 1 were independently associated with DRS ‐ FEV 1 (R 2 = 0.14, P = 0.01). In addition, VA / TLC was associated with both airway narrowing and closure in response to methacholine. Conclusions These results confirm that baseline VA / TLC is associated with AR , and reflects both airway closure and airway narrowing following methacholine challenge.Keywords:
Methacholine
Vital capacity
BACKGROUND: It is most physiologic to measure the diffusing capacity of the lung by using oxygen, but it is so difficult to measure partial pressure of oxygen in the capillary blood of the lung that in clinical practice it is measured by using carbon monoxide, and single-breath diffusing capacity method is used most widely. However, since the process of withholding the breath for 10 seconds after inspiration to the total lung capacity is very hard to practice for patients who suffer from cough, dyspnea, etc, the intrabreath lung diffusing capacity method which requires a single exhalation of low-flow rate without such process was devised. In this study, we want to know whether or not there is any significant difference in the diffusing capacity of the lung measured by the single-breath and intra-breath methods, and if any, which factors have any influence. METHODS: We chose randomly 73 persons without regarding specific disease, and after conducting 3 times the flow-volume curve test, we selected forced vital capacity(FVC), percent of predicted forced vital capacity, forced expiratory volume within 1 second(FEV1), percent of forced expiratory volume within 1 second, the ratio of forced expiratory volume within 1 second against forced vital capacity(FEV1/FVC) in test which the sum of FVC and FEV1 is biggest. We measured the diffusing capacity of the lung 3 times in each of the single-breath and intra-breath methods at intervals of 5 minutes, and we evaluated which factors have any influence on the difference of the diffusing capacity of the lung between two methods[the mean values(ml/min/mmHg) of difference between two diffusing capacity measured by two methods] by means of the linear regression method, and obtained the following results: RESULTS: 1) Intra-test reproducibility in the single-breath and intra-breath methods was excellent. 2) There was in general a good correlation between the diffusing capacity of the lung measured by a single-breath method and that measured by the intra-breath method, but there was a significant difference between values measured by both methods(l.0l+/-0.35ml/min/mmHg, p<0.01) 3) The differnce between the diffusing capacity of the lung measured by both methods was not correlated to FVC, but was correlated to FEV1, percent of FEV1, FEV1/FVC and the gradient of methane concentration which is an indicator of distribution of ventilation, and it was found as a result of the multiple regression test, that the effect of FEV1/FVC was most strong(r=-0.4725, p<0.01) 4) In a graphic view of the difference of diffusing capacity measured by single-breath and intra-breath method and FEV1/FVC, it was found that the former was divided into two groups in section where FEV1/FVC is 50~60%, and that there was no significant difference between two methods in the section where FEV1/FVC is equal or more than 60% (0.05 +/-0.24ml/min/mmHg, p>0.1), but there was significant difference in the section, less than 60%(-4.5+/-0.34ml/min/mmHg, p <0.01). 5. The diffusing capacity of the lung measured by the single-breath and intra-breath method was the same in value(24.3 +/-0.68ml/min/mmHg) within the normal range(2%/L) of the methane gas gradient, and there was no difference depending on the measuring method, but if the methane concentration gradients exceed 2%/L, the diffusing capacity of the lung measured by single-breath method became 15.0+/-0.44ml/min/mmHg, and that measured by intra-breath method, 11.9+/-0.5 1ml/min/mmHg, and there was a significant difference between them(p<0.01). CONCLUSION: Therefore, in case where FEV1/FVC was less than 60%, the diffusing capacity of the lung measured by intra-breath method represented significantly lower value than that by single-breath method, and it was presumed to be caused largely by a defect of ventilation- distribution, but the possibility could not be excluded that the diffusing capacity of the lung might be overestimated in the single-breath method, or the actual reduction of the diffusing capacity of the lung appeared more sensitively in the intra-brerath method.
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Lung function measurements play an essential role in early diagnosis and monitoring of bronchial asthma in children. For clinical evaluation, measurements are commonly compared to reference values. However, these reference values are calculated based on measurements performed in groups of mostly older children and young adults two or three decades ago. In the present, cross-sectional study, lung function measurements were performed in 518 children (241 boys and 277 girls; mean age 6.0+/-0.3 years) at a regular medical check prior to school enrollment. Spirometry was done using the MasterScreen IOS (Cardinal Health, Wurzburg). We recorded forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)), maximal expiratory flow (PEF), and maximal expiratory flow at 75, 50, and 25% of vital capacity (MEF(75), MEF(50), MEF(25)). We found that FEV(1) and FVC corresponded to reference values (101.0+/-14.9% and 95.4+/-13.6%, in boys and girls, respectively). In maneuvers satisfying ATS/ERS criteria (T(E) >1 sec), forced expiratory (parameters (PEF, MEF(50)) reached only 68.9+/-13.6 and 75.9+/-26.6% of reference values, in boys and girls, respectively). There was no significant correlation of lung function parameters to BMI. In conclusion, the hitherto reference values largely overestimate the maximal flow rates of preschool children performing a forced spirometry with T(E) >1 sec. At the age of 6, forced expiratory flow values are not (yet) impaired by an increased BMI. Standardized spirometry starting in preschool children allows closely evaluating the individual development of lung function during follow-up measurements.
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The practicality of office spirometry has been established. Two basic parameters can be quickly and accurately measured in the physician's office or clinic: forced vital capacity (FVC) as a test of volume, indicative of restrictive lung disease, and forced expiratory volume in one second (FEV1) as a test of flow, indicative of obstructive lung disease. The ratio of FEV1 to FVC (FEV1/FVC%) is a valuable screening tool. Test results are compared with normal values, and abnormalities must be interpreted in the context of the individual patient's history and condition. Office spirometry provides a simple, noninvasive, inexpensive tool for assessing and managing respiratory disease.
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Seventy-five adult asthmatic patients with clinical remission underwent spirometry. Only 8.3% of the subjects demonstrated normal spirometry. The others had reduced vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), maximum mid-expiratory flow rate (MMF) and peak flow rate (PEFR). This study demonstrates that asthma can cause irreversible airflow obstruction and there is a poor relationship between symptoms in asthmatics and their respiratory function test results.
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Lung function measured at work is used to make important employment decisions. Improving its quality will reduce misclassification and allow more accurate longitudinal interpretation over time.To assess the amount by which lung function (forced expiratory volume in 1 second [FEV1] and forced vital capacity [FVC]) values will be underestimated if recommended spirometry testing guidance is not followed.Lung function was measured in a population of workers. Knowledge of the final reproducible FEV1 and FVC for each worker allowed estimation of the underestimates that would have occurred if less forced manoeuvres than recommended had been performed.A total of 667 workers (661 males, mean age 43 years, range 18-66) participated. Among them, 560 (84%) achieved reproducible results for both FEV1 and FVC; 470 (84%) of these did so after three technically acceptable forced expiratory manoeuvres, a cumulative total of 533 after four, 548 after five, 557 after six, 559 after seven and 560 after eight blows. If only one (or first two) technically acceptable blow(s) had been performed, mean underestimates were calculated for FEV1 of 115.1 ml (35.4 ml) and for FVC of 143.4 ml (42.3 ml).In this study, reproducible spirometry was achievable in most workers. Not adhering to standards underestimates lung function by clinically significant amounts.
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The accuracy of a simple, pneumatic, direct-recording spirometer suitable for office use was evaluated by comparing spirometry on a water-sealed, 13.5-liter, water-filled spirometer for 120 patients. Good correlation between the two spirometers was seen through a wide range of values for forced vital capacity, forced expiratory volume in one second, and forced expiratory flow during 25% to 75% of forced vital capacity, with coefficients of correlation being 988, 988, and 948, respectively. All correlations were significant. The pneumatic spirometer is accurate, simple to operate, and suitable for spirometry in the office and clinic. (JAMA240:2754-2755, 1978)
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The comparative ability to detect early abnormalities in smokers by commonly used lung function tests was studied. Sixty-five healthy male nonsmokers served as a reference group and provided standards for 1-sec forced expiratory volume, vital capacity, end-tidal spirometry, spirometric forced mid-and end-expiratory flows, single-breath diffusing capacity, static lung volumes (helium method), and single-breath N2 closing volume measurements, In the present series of 80 male smokers, the measurements of forced mid-expiratory flow and forced end-expiratory flow did not improve the ability of the more conventional indices, 1-sec forced expiratory volume and the ratio of 1-sec forced expiratory volume to vital capacity, to detect obstructive lung disease. In 71 smokers with normal 1-sec forced expiratory volume and ratio of 1-sec forced expiratory volume to vital capacity, the end-tidal spirometry, diffusing capacity, and residual volume indices revealed 14,20, and 21 per cent of abnormalities. respectively. The single-breath N2 closing volume test (Phase IV/vital capacity and slope of Phase III) detected the greatest number of subtle changes in lung function; this was abnormal in 32 per cent of smokers with normal conventional spirometry. In young or light smokers, Phase IV/vital capacity was more frequently increased than the slope of Phase III; an incerse trend was observed in older or heavier smokers. The single-breath N2 closing volume test also provided the greatest number of abnormal results when other indices were impaired in the same subjects.
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We aimed to ascertain the fit of the European Respiratory Society Global Lung Initiative 2012 reference ranges to contemporary Australasian spirometric data. Z-scores for spirometry from Caucasian subjects aged 4-80 years were calculated. The mean (SD) Z-scores were 0.23 (1.00) for forced expirtory volume in 1 s (FEV(1)), 0.23 (1.00) for forced vital capacity (FVC), -0.03 (0.87) for FEV(1)/FVC and 0.07 (0.95) for forced expiratory flows between 25% and 75% of FVC. These results support the use of the Global Lung Initiative 2012 reference ranges to interpret spirometry in Caucasian Australasians.
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Respiratory function was studied in 44 cases of sarcoidosis. Patients were classified into several groups depending on radiological findings. There was little correlation between functional abnormality and radiological change until advanced parenchymal infiltration occurred. The most common findings were lowered forced vital capacity, total lung capacity, diffusing capacity, and dynamic compliance. Significant correlations were found between diffusing capacity and forced vital capacity, diffusing capacity and total lung capacity, and between arterial oxygen tension and forced expiratory volume in 1 sec. There were no significant correlations between diffusing capacity and arterial oxygen tension or between diffusing capacity and dynamic compliance. Evidence of diffuse expiratory airway obstruction in 13 sarcoid patients who did not smoke is assumed to be due to peri-bronchiolar peripheral airway involvement
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