Bronchial Responsiveness to Dry Air Hyperventilati

Authors: Peter Blomstrand Susanne Ekedahl Birgitta Schmekel

Publish Date: 2013/01/25

Volume: 191, Issue: 2, Pages: 183-190

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Abstract

Disabling respiratory symptoms and rapid decline of lung function may occur in susceptible tobacco smokers Bronchial hyperresponsiveness BHR elicited by direct challenge methods predicts worse lung function outcomes The aim of this study was to evaluate whether BHR to isocapnic hyperventilation of dry air IHDA was associated with rapid deterioration in airway status and respiratory symptomsOne hundred twentyeight smokers and 26 age and sexmatched healthy individuals with no history of smoking were investigated All subjects completed a questionnaire Spirometry and impulse oscillometry IOS measurements were recorded before and after 4 min of IHDA The tests were repeated after 3 years in 102 smokers and 11 controlsEightyfive smokers 66  responded to the challenge with a ≥24Hz increase in resonant frequency F res the cutoff limit defining BHR as recorded by IOS They had higher F res at baseline compared to nonresponding smokers 128 ± 32 vs 115 ± 34 Hz p  005 and lower FEV1 83 ± 13 vs 89 ± 13 predicted p  005 Multivariable logistic regression analysis indicated that wheezing odds ratio = 37 p  001 and coughing odds ratio = 81 p  005 were significantly associated with hyperresponsiveness An increase in F res was recorded after 3 years in responding smokers but not in nonresponders or controls The difference remained when subjects with COPD were excludedTobacco smoking may result in significant limitation of physical performance in susceptible subjects Hindering symptoms such as dyspnea coughing and attacks of wheezing and airway obstruction may occur and some smokers may experience a fasterthannormal decline of lung function and ultimately chronic obstructive pulmonary disease COPD a disorder characterized by systemic and airway mucosal inflammation 1 2 3 Although bronchial hyperresponsiveness BHR may occur in many diseases 4 it is most common in patients with inflammatory disorders of the airway mucosa It has been reported in smokers with COPD that subjects with a fasterthannormal decline of lung function may be identified by hyperresponsiveness to methacholine or histamine 5 6 BHR is also an independent predictor of mortality in patients with COPD 7 An extensive search for surrogate markers capable of predicting outcomes in terms of lung function in smokers has been conducted and numerous studies on serum or sputum markers of inflammation as well as on various tests of BHR have been published BHR usually evaluated by inhalation of methacholine or histamine has been found to occur in up to 85  of smokers with COPD 5 8 9 In contrast BHR elicited by indirect challenge methods such as isocapnic hyperventilation of cold or dry air IHDA was reported to occur much less frequently only 16  of smokers were reported to respond to IHDA with increased airway tonus 10 11Responses to bronchial challenges have been measured mostly in terms of forced expiratory volume in 1 second FEV1 a technique that requires considerable patient cooperation A deep inhalation preceding and/or a forced expiration during a FEV1 maneuver may alter bronchial tone for time periods up to 6 min this may reduce the ability of tests to correctly identify BHR 12 13 Impulse oscillometry IOS is an alternative technique to measure airway status that requires minimal patient cooperation IOS is particularly suitable for serial measurements such as those required during a bronchial challenge 14 15 Airway resistance reactance and resonant frequency F res are the outcome data values of F res are closely related to those of airway resistance and are defined by the frequency at which inertial forces are equal and opposite to elastic forces ie reactance is zeroThe aim of this study was to evaluate whether BHR to IHDA as measured by means of IOS was associated with deterioration in airway status relative to baseline in a 3year followup study We also examined whether the presence of BHR was associated with subjectively perceived respiratory symptoms or reduced pulmonary function in smokers

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