Identifying bronchoconstriction from the ratio of diaphragm EMG to tidal volume

BACKGROUND

A fall of ≥ 20 % in forced expiratory volume in the first second (FEV1) with a cumulative dose of histamine ≤ 7.8 μmol is considered to indicate bronchial hyperactivity, but no method exists for patients who cannot perform spirometry properly. Here we hypothesized that increases in respiratory central output measured by chest wall electromyography of the diaphragm (EMGdi-c) expressed as a function of tidal volume (EMGdi-c/VT) would have discriminative power to detect a 'positive' challenge test.

METHODS

In a physiological study EMGdi was recorded from esophageal electrode (EMGdi-e) in 16 asthma patients and 16 healthy subjects during a histamine challenge test. In a second study, EMGdi from chest wall surface electrodes (EMGdi-c) was measured during a histamine challenge in 44 asthma patients and 51 healthy subjects. VT was recorded from a digital flowmeter during both studies.

RESULTS

With histamine challenge test the change in EMGdi-e/VT in patients with asthma was significantly higher than that in healthy subjects (104.2 % ± 48.6 % vs 0.03 % ± 17.1 %, p < 0.001). Similarly there was a significant difference in the change of EMGdi-c/VT between patients with asthma and healthy subjects (90.5 % ± 75.5 % vs 2.4 % ± 21.7 %, p < 0.001). At the optimal cut-off point (29 % increase in EMGdi-c/VT), the area under the ROC curve (AUC) for detection of a positive test was 0.91 (p < 0.001) with sensitivity 86 % and specificity 92 %.

CONCLUSIONS

We conclude that EMGdi-c/VT may be used as an alternative for the assessment of bronchial hypersensitivity and airway reversibility to differentiate patients with asthma from healthy subjects.

Post-bronchodilator Reversibility of FEV1 and Eosinophilic Airway Inflammation in COPD

INTRODUCTION

The relationship between bronchodilator responsiveness and eosinophilic airway inflammation has not been well documented in COPD. It has been investigated in this retrospective study. This issue has grown in importance due to increasing interest in the asthma-COPD overlap syndrome.

METHODS

264 stable COPD patients with no past history of asthma were retrospectively analyzed. Correlation analyses between FEV₁ reversibility and sputum eosinophil levels were conducted. Sputum eosinophil levels were dichotomized using FEV₁ reversibility cut-off points (>0.4L and >15% vs. >0.2L and >12%) and compared. The effectiveness of FEV₁ reversibility to predict sputum eosinophilia (>3%) was analyzed with a logistic regression and a ROC analysis.

RESULTS

82 (31.1%) patients with higher FEV₁ reversibility values (0.14 vs. 0.11L, P=.01) presented sputum eosinophilia. FEV₁ reversibility was weakly correlated with the sputum eosinophil level (r=0.162, P=.008). Patients with FEV₁>0.4L and >15% increment had higher sputum eosinophil levels (6.11 vs. 1.02%, P=.049) whereas the level did not differ when dichotomized by FEV₁ increment >0.2L and >12%. Very positive FEV₁ reversibility (>0.4L and >15%) predicted sputum eosinophilia after adjustment forage, baseline FEV₁ and FVC (OR: 4.262, P=.029). In the ROC analysis, the AUC was 0.58 (P=.034), and FEV₁ increment>0.4L and >15% had a positive predictive value of 63.6% and an overall accuracy of 70.1%.

CONCLUSIONS

FEV₁ reversibility was weakly correlated with sputum eosinophil levels in COPD. Positive FEV₁ reversibility (>0.4L and >15%) is moderately successful in predicting sputum eosinophilia (>3%).

Inter-regional changes in the performance and interpretation of spirometry in Spain: 3E study

OBJECTIVES

This report shows the results of a nation-wide survey on spirometry to assess regional differences.

METHODS

Observational cross-sectional study conducted by means of a telephone survey in 805 primary care (PC) and specialized centers (SC) in all regions. The survey contacted technicians in charge of spirometry and consisted of 36 questions related to the test.

RESULTS

The results showed major differences between regions. Most centers had 1-2 spirometers. The number of spirometry tests per week ranged from 2 to 8.9 in PC and between 34.3 and 98.3 in SC. Some training had been given in most centers (63.6-100% in PC and 60.0-100% in SC) but not on a regular basis. Most centers used several short-acting bronchodilators for the bronchodilation test, but with insufficient inhalations (2.0-3.8 in PC and 2.0-3.3 in SC) and frequently incorrect waiting time (29.4-83.3% PC and 33.3-87.5% in SC). Daily calibration was not performed in all centers (0-100% in PC and 66.7-100% in SC). Significant inter-regional differences in spirometry quality criteria were observed, with 6 or more criteria met in 9.1-84.6% of PC centers and 37.5-100% in SC.

CONCLUSIONS

Our results show the current situation of spirometry in primary and specialized care in Spain, highlighting considerable variability and areas for improvement. This information should be considered by health officials to improve the quality and accessibility of such tests.

Bronchodilator Response of FEV6 and FEV3 as Surrogates of Forced Vital Capacity

BACKGROUND

Spirometry as a non-invasive and inexpensive test is widely used for occupational health evaluations. Bronchodilator test is used for the assessment of airflow limitation and increase in forced expiratory volume in 1 second (FEV1) or forced vital capacity (FVC) is considered as a positive response. This study was performed to assess the response of forced expiratory volume in 6 seconds (FEV6), forced expiratory volume in 3 seconds (FEV3), and forced expiratory time (FET) to bronchodilator administration.

MATERIALS AND METHODS

In this cross-sectional study, the response of FEV3, FEV6, FEV1/FEV3, FEV1/FEV6 and FET to bronchodilator administration was assessed in subjects referred to Yazd occupational medicine clinic regardless of their diagnosis. The average increase in spirometric parameters (i.e. FVC, FEV1, FEV1/FVC, FEV3, FEV6, FEV1/FEV3, FEV1/FEV6 and FET) was measured. The difference between baseline and post-bronchodilator spirometries was assessed by calculating absolute change and change from baseline as well. Data analysis was done by Student's t test, chi square test and Pearson's correlation test.

RESULTS

Totally 104 subjects were entered in the study. FEV1 showed the highest response to bronchodilator. FVC response to bronchodilator was correlated with FET, but such correlation was not observed for FEV6 and FEV3. The mean increase in FEV6, FEV3, and FET after bronchodilator administration was 50.90 ml (2.23%), 110.51 ml (3.08%) and -1.85 s, respectively.

CONCLUSION

FVE6 can be used as a substitute for FVC for the assessment of bronchodilator response without the need for FET adjustment.

Assessment of bronchodilator response in various spirometric patterns

BACKGROUND

Spirometry is a physiologic test that measures the volume of air an individual inhales or exhales and the rate at which the volume is changed as a function of time. Bronchodilator response, as a beneficial test for diagnosis of bronchial responsiveness is measured using the percent change from baseline and absolute changes in forced expiratory volume in 1 second and/or forced vital capacity. In this study we aimed to assess the increase in spirometric parameters in patients with symptoms of asthma regardless of spirometric pattern.

MATERIALS AND METHODS

In this cross-sectional study bronchodilator test was performed in individuals with dyspnea, cough or wheezing and the mean increase in various spirometric parameters was measured and compared among individuals with different spirometric patterns.

RESULTS

Among all individuals 24.5% responded to bronchodilator. Forced expiratory volume in 1 second was the parameter with the most frequent response to bronchodilator. Patients with mixed pattern had the highest frequency of response to bronchodilator. Response to bronchodilator was more than 50% in most mid flow volumes.

CONCLUSION

Some patients with symptoms of asthma may show restrictive or mixed pattern in spirometry which may respond to bronchodilator administration.

Severity staging of chronic obstructive pulmonary disease: differences in pre- and post-bronchodilator spirometry

PURPOSE

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines for chronic obstructive pulmonary disease (COPD) uses the post-bronchodilator spirometry for diagnosis and severity staging. We evaluated differences in the severity classification of COPD, based on pre- and post-bronchodilator spirometry.

MATERIALS AND METHODS

From 2000 to 2004, 207 COPD patients who underwent spirometry before and after inhalation of 400 microg of fenoterol were analyzed. A responder to the bronchodilator test (BDT) was defined by the American Thoracic Society (ATS) as an increase in forced expiratory volume in one second (FEV(1)) or forced vital capacity > or = 12% and > or = 200 mL, and by the European Respiratory Society (ERS) as an increase in FEV(1) > or = 10% of the predicted value. COPD severity was classified according to the 2008 GOLD guidelines.

RESULTS

For the entire study population, the FEV(1) increased by 11.8 +/- 12.5% of baseline after BDT and 41.1% and 27.1% of subjects were classified as responders using the ATS and ERS criteria, respectively. Based on pre-BDT spirometry, 55, 85, 58, and 9 patients were classified as Stage I-IV COPD, respectively. Sixty-seven (32.4%) patients changed severity staging after BDT, including 20.0%, 28.2%, 44.8%, and 66.7% of pre-BDT patients Stages I through IV, respectively. More ATS or ERS BDT-responders had a change in severity staging than non-responders (52.9% vs. 18.9% and 62.5% vs. 21.2%, both p < 0.001).

CONCLUSION

Our data suggest that the severity staging of COPD using pre-BDT spirometry might lead to significant differences as compared to staging, based on post-BDT spirometry, as recommended by the current GOLD guidelines.