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Communications to the Editor |

At Least Three FEV1 Blows Are Required at Each Time Point During the Assessment of Bronchial Hyperresponsiveness FREE TO VIEW

Ashwini Jantikar, MBBS; Sandeep Sewlikar, MBBS; Bill Brashier, MBBS DTCD; Manisha Maganji, MBBS; Trupti Bal; Sundeep Salvi, MD, PhD
Author and Funding Information

Affiliations: Chest Research Foundation, Pune, India,  Royal University Hospital, Saskatoon, SK, Canada

Correspondence to: Sundeep Salvi, MD, PhD, Chest Research Foundation, Marigold Premises, Survey No. 15 Kalyani Nagar, Pune, India; e-mail: sundeepsalvi@yahoo.com



Chest. 2005;128(1):469-470. doi:10.1378/chest.128.1.469
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To the Editor:

Bronchoprovocation tests are used routinely in clinical practice and research to detect and quantify the presence of bronchial hyperresponsiveness. Histamine, methacholine, and 5′-adenosine monophosphate (AMP) are some of the bronchoprovocative agents used to test bronchial hyperresponsiveness. After obtaining the baseline FEV1 value, subjects are asked to inhale increasing concentrations of bronchoprovocative agents with a dosimeter, until the postchallenge FEV1 drops by 20% from the baseline value (measured as provocative dose causing a 20% fall in FEV1 [PD20], or provocative concentration causing a 20% fall in FEV1). According to American Thoracic Society guidelines,1subjects are asked to perform at least three FEV1 maneuvers at each time point after administering the bronchoprovocative dose. This may mean performing up to 75 forced expiratory maneuvers over a period of 1 h, which can be very tiring to many patients undergoing this test. Cockcroft and colleagues3 have described test-shortening procedures for bronchial challenge, in which they have recommended a single forced expiratory maneuver at each time point following administration of the bronchoprovocative substance. However, because of wide variability between FEV1 values in the same subject when performed at the same time, using only one forced expiratory maneuver may not be reliable to obtain the highest FEV1 value.

We aimed to study whether three forced expiratory blows are really necessary at each time point following the bronchoprovocative challenge and whether the first or second forced expiratory maneuver gives the highest FEV1 value > 90% of the time. We conducted a study in 12 subjects who underwent two bronchoprovocation tests on separate days at least a week apart with AMP and determined how frequently the best FEV1 value was obtained during the first, second, and third forced expiratory maneuvers after sufficient motivation to give their best effort at each of the three blows. These were recorded as best, second best, and third best (highest to lowest FEV1 values), and their corresponding blow numbers were recorded (first blow, second blow, and third blow). The first blow produced the best FEV1 in 43.49% of the times, while the second and third blows produced the best FEV1 values 24.59% and 31.92% of the times, respectively. Using only one blow (as suggested by Cockcroft and colleagues) would have missed the best FEV1 value 56.51% of the times, while using two FEV1 blows would have missed the best FEV1 31.92% of the times. We therefore conclude that in order to obtain reliable FEV1 values during bronchoprovocation testing, at least three forced expiratory blows are required at each time point. Asking the subject to perform only one forced expiratory blow would give unreliable FEV1 values, which would likely give false PD20 values.

. American Thoracic Society (2000) Guidelines for methacholine and exercise challenge testing–1999.Am J Respir Crit Care Med161,309-329. [PubMed]
 
Cockcroft, DW, Marciniuk, DD, Hurst, TS, et al Methacholine challenge: test-shortening procedures.Chest2001;120,1857-1860. [CrossRef] [PubMed]
 
Cockcroft, DW, Davis, BE, Smycniuk, AJ Development of a methacholine challenge method to minimize methacholine waste.Chest2003;124,1522-1525. [CrossRef] [PubMed]
 
To the Editor:

We thank Jantikar et al for their interest in our publications. They raise some valid points regarding patient fatigue during methacholine challenge and the reproducibility of FEV1 maneuvers. Their points regarding the best FEV1 occurring on the first, second, or third attempt are valid. However, we cannot agree with their conclusions.

The use of a single technically acceptable spirogram at each time point (ie, 30 and 90 s following inhalation) was not introduced in the two publications outlined by these authors.12 It dates back to the original description of the method in 1977.3 For the majority of this almost 30-year period, we have further reduced patient fatigue by performing truncated spirograms to capture only the FEV1. This procedure requires an astute and well-trained technician or research assistant who can properly train the subjects prior to starting inhalations, and who can promptly identify unacceptable maneuvers, be it due to poor effort, coughing, or other conditions, and discard them. In such instances, which occur relatively infrequently, a repeat spirogram is performed within < 30 s. Although many look for the highest FEV1 at each time point, as outlined by these authors, we have historically used the lowest FEV1 for two reasons. First we are looking for the maximum effect of the bronchoconstricting agent and second, the time course of the response is relatively brief. A comparison of highest and lowest spirograms has revealed no significant difference.

While it is true that the best FEV1 may well occur on the second, third, or even later attempt, this issue per se is probably not relevant to the number of spirograms performed during bronchoprovocation. The more important issue is the magnitude of the difference between FEV1 attempts (ie, the repeatability of the FEV1). If the three determinations of FEV1 are, as we suspect, within ≤ 5%, then we would suggest that the additional time and effort required to obtain three maneuvers vs two maneuvers is of little advantage. Additional factors other than the number of FEV1 maneuvers and subject fatigue must be considered. It is important to maintain a consistent dosing interval to assure that any cumulative effect is constant. We13 and the American Thoracic Society5have recommended a 5-min interval between the start of one concentration and the start of the next concentration. One is therefore obtaining spirograms within about a 2-min window between 30 s after the completion of one inhalation and 30 s before the commencement of the next. It would be difficult to obtain six acceptable spirograms in a 2-min window. Additionally, consideration must be given to the potential effect of the maneuver on the measurement of the response. Total lung capacity inhalations may bronchodilate or bronchoprotect, thus inhibiting the response and potentially leading to the unnecessary administration of higher concentrations of bronchoconstricting stimuli. This situation is evident particularly in mildly responsive individuals,6 and represents the range that is most often seen in a diagnostic laboratory and could result in false-negative results or an underestimation of airway responsiveness. By contrast, repeated forced expiratory maneuvers may enhance bronchoconstriction, a feature that would be limited to subjects with more marked airway hyperresponsiveness.

In summary, we believe that, with meticulous attention to subject training and with the immediate recognition and disposal of technically unacceptable spirograms, single FEV1 measurements from a truncated spirogram at the two time points are adequate and preferable to the alternatives expressed here.

References
Cockcroft, DW, Marciniuk, DD, Hurst, TS, et al Methacholine challenge: test-shortening procedures.Chest2001;120,1857-1860. [CrossRef] [PubMed]
 
Cockcroft, DW, Davis, BE, Smycniuk, AJ Development of a methacholine challenge method to minimize methacholine waste.Chest2003;124,1522-1525. [CrossRef] [PubMed]
 
Cockcroft, DW, Killian, DN, Mellon, JJ, et al Bronchial reactivity to inhaled histamine: a method and clinical survey.Clin Allergy1977;7,235-243. [CrossRef] [PubMed]
 
Davis, BE, Cockcroft, DW Calculation of provocative concentration causing a 20% fall in FEV1: comparison of lowest vs. highest post-challenge FEV1.Chest2000;117,881-883. [CrossRef] [PubMed]
 
Crapo, RO, Casaburi, R, Coates, AL, et al Guidelines for methacholine and exercise challenge testing-1999: this official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999.Am J Respir Crit Care Med2000;161,309-329. [PubMed]
 
Todd, DC, Davis, BE, Hurst, TS, et al Dosimeter methacholine challenge: comparison of maximal versus submaximal inhalations.J Allergy Clin Immunol2004;114,517-519. [CrossRef] [PubMed]
 

Figures

Tables

References

. American Thoracic Society (2000) Guidelines for methacholine and exercise challenge testing–1999.Am J Respir Crit Care Med161,309-329. [PubMed]
 
Cockcroft, DW, Marciniuk, DD, Hurst, TS, et al Methacholine challenge: test-shortening procedures.Chest2001;120,1857-1860. [CrossRef] [PubMed]
 
Cockcroft, DW, Davis, BE, Smycniuk, AJ Development of a methacholine challenge method to minimize methacholine waste.Chest2003;124,1522-1525. [CrossRef] [PubMed]
 
Cockcroft, DW, Marciniuk, DD, Hurst, TS, et al Methacholine challenge: test-shortening procedures.Chest2001;120,1857-1860. [CrossRef] [PubMed]
 
Cockcroft, DW, Davis, BE, Smycniuk, AJ Development of a methacholine challenge method to minimize methacholine waste.Chest2003;124,1522-1525. [CrossRef] [PubMed]
 
Cockcroft, DW, Killian, DN, Mellon, JJ, et al Bronchial reactivity to inhaled histamine: a method and clinical survey.Clin Allergy1977;7,235-243. [CrossRef] [PubMed]
 
Davis, BE, Cockcroft, DW Calculation of provocative concentration causing a 20% fall in FEV1: comparison of lowest vs. highest post-challenge FEV1.Chest2000;117,881-883. [CrossRef] [PubMed]
 
Crapo, RO, Casaburi, R, Coates, AL, et al Guidelines for methacholine and exercise challenge testing-1999: this official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999.Am J Respir Crit Care Med2000;161,309-329. [PubMed]
 
Todd, DC, Davis, BE, Hurst, TS, et al Dosimeter methacholine challenge: comparison of maximal versus submaximal inhalations.J Allergy Clin Immunol2004;114,517-519. [CrossRef] [PubMed]
 
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