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M. van Oosten1, M. Gudjonsdottir2, A. Johnsen3, B. Magnusson4
1University of Iceland, Public Health, Reykjavík, Iceland, 2Reykjalundur Rehabilitation Centre, Reykjalundur, Cardiopulmonary Laboratory, Mosfellsbaer, Iceland, 3University of Iceland, Faculty of Medicine, Reykjavík, Iceland, 4Health Care Institution of South Iceland, Department of Internal Medicine, Selfoss, Iceland
Background: In the efforts to improve asthma control, clinical guidelines recommend breathing retraining as an adjuvant treatment to correct dysfunctional breathing. These therapies are mainly evaluated subjectively by using questionnaires. However, these therapies are rarely objective in assessing ventilatory parameters, as measuring these parameters can be challenging.
Purpose: To compare measurements of resting ventilation and the threshold of dyspnoeic sensation in asthma patients and healthy subjects and to evaluate the stability of these measurements over time.
Methods: Thirty patients with physician-diagnosed asthma who used inhaled short-acting beta2-agonist during the four weeks before admission (at least once a week in the last four weeks) and 23 healthy controls were evaluated twice, at M1 and M2, with a time interval range of 16.71 till 50.86 weeks. Ventilation measures, including ventilation (VE), end-tidal carbon dioxide (PETCO2), respiratory rate (RR), tidal volume (VT) and carbon dioxide output (VCO2) were sampled at utmost rest in an upright position for 10 minutes with a facemask while listening to relaxing recording. The average of the last 4 minutes for these parameters was used for statistics. The threshold of dyspnoeic sensation was evaluated with breath-holding time (BHT), being the post expiratory period with no respiratory sensation, measured before spirometry by the average of three and with one-minute intervals. The ventilatory equivalent for CO2 (VE/VCO2) and breathing pattern (RR/VT) were calculated, and the asthma control test questionnaire (ACT) was administered for patients.
Results: At M1, 30 asthma patients, 45 ± 14 years old and 23 matched healthy subjects, 44 ± 15 years (p = 0.85), were found to have similar ventilatory parameters (FEV1/FVC 74.4 ± 11 vs. 81 ± 6, p = 0.084; VE 6.0 [5.6,7.7] vs. 6.0 [5.6,7.6], p = 0.921; PETCO2 33.6 ± 3.41 vs. 34.8 ± 2.8, p = 0.06; VE/VCO2 47 [43.55] vs 41 [39,47], p = 0.085; RR/VT 23 [15.35] vs 20 [12,24] p = 0.214 and ACT 16.23 ± 4.61 vs.18.53 ± 5.04 at M2, p = 0.0219) and kept it consistent within a time interval of 28.7 ± 7.3 weeks at M2, except for BHT which was shorter in the patients (14.2 ± 8.0 sec. vs.19.0 ± 7.3 sec, p < 0.05) and increased over time in both groups.
Conclusion(s): Resting ventilation was similar and stable over time in both groups. Still, the threshold of dyspnoeic sensation was lower in the patients as indicated by shorter breath-holding time. A learning effect was observed in the BHT measurements as it increased in both groups over time without changes in any other ventilatory parameters.
Implications: Breath-holding time could be an easy-to-perform measurement in physiotherapy praxis to evaluate the effect of breathing retraining, but the learning effect observed in the breath-holding time measurements should be taken into account.
Funding, acknowledgements: This study was supported by the [country blinded for review] Asthma-and Allergy Association, the [country blinded for review] Physiotherapy Association.
Keywords: Asthma, Breath-holding time, Resting ventilation
Topic: Cardiorespiratory
Did this work require ethics approval? Yes
Institution: The National Bioethics Committee of Iceland
Committee: The National Bioethics Committee of Iceland
Ethics number: VSNb2012010044/03.7
All authors, affiliations and abstracts have been published as submitted.
