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Copyright ©ERS Journals Ltd 2007
Benefits of a modified spirometry technique
Dept of Pulmonary, Allergy, and Critical Care Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA.
To the Editors:
We applaud the American Thoracic Society (ATS) and the European Respiratory Society for their continuing efforts to optimise pulmonary function testing practice through disseminating guidelines, such as the recent spirometry guidelines 1. In reviewing this document, we wish to point out a spirometry practice that, although mentioned (but not endorsed) in the guidelines, can, in our experience, substantially improve and streamline the performance of spirometry by pulmonary function laboratories 2. Specifically, we point out the benefits of a modified spirometry technique in which the expiratory effort is relaxed after the first 3 s of expiration. As evaluated and reported in a small, randomised, controlled, crossover trial of two expiratory techniques and in our subsequent experience 2, four lines of reasoning support the benefits of using this modified spirometry technique to obtain high-quality measurements, as follows.
1) Enhanced satisfaction of spirometric end-of-test criteria. In the original report 1, ATS end-of-test criteria were met significantly more frequently with the modified expiratory technique (58.3 versus 18.7% of sessions; p<0.001). More recent experience in our laboratory, in which we have routinely used this technique since 1994 3, confirms this initial experience, leading us to recommend this technique to others and for consideration to include in future guidelines. For example, using this technique in recent years, the mean expiratory time for patients with obstruction in our laboratory is 12.4±3 s.
2) Patient preference for this modified technique. In our initial comparison of techniques and subsequent experience, patients tested with both techniques preferred the modified technique. In our original report, although comparative subjective ratings did not achieve statistical significance, trends toward more comfort and less lightheadedness with the modified technique were evident.
3) Fewer adverse effects associated with spirometry performance using the modified technique. The frequency of pre-syncope and syncope, although low even with the standard technique of sustained forced expiration, seems yet lower using the modified expiratory technique. Before 1994, when the standard "push as hard as you can for as long as you can" expiratory technique was used, we observed an annual mean of 
13 episodes of pre-syncope or syncope during spirometry. Since adopting the modified technique as our standard approach in 1994, we have observed no episodes of pre-syncope or syncope during spirometry in the context of performing >15,000 testing sessions yearly in our laboratory.
4) Streamlined spirometry technique. Our experience suggests that the difference between forced vital capacity (FVC) and slow vital capacity (SVC) most often relates to the patient's inability to sustain a forced expiration rather than true physiological air-trapping. A review of our laboratory database shows the mean difference between SVC and FVC from the same testing session in patients with airflow obstruction is 0.13 L, with 23% of patients showing a slightly higher FVC than SVC. As introduction of this modified technique has lessened the difference between FVC and SVC, we no longer routinely perform the SVC manoeuvre during spirometry and measure SVC only when determining lung volumes, thereby shortening the standard spirometry procedure considerably. On this basis as well, we recommend the modified expiratory technique to others.
Overall, in the context of our favourable experience with this modified expiratory technique in our initial report and over the subsequent 14 yrs, we recommend it to others and favour consideration of its endorsement in forthcoming official recommendations and guidelines as a useful strategy along with others (e.g. measuring the forced expiratory volume in six seconds 4) to optimise spirometry measurements.
REFERENCES
- Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J 2005;26:319–338.
[Abstract/Free Full Text] - Stoller JK, Basheda S, Laskowski D, Goormastic M, McCarthy K. Trial of standard versus modified expiration to achieve end-of-test spirometry criteria. Am Rev Respir Dis 1993;148:275–280.[Web of Science][Medline] [Order article via Infotrieve]
- Stoller JK, Buist AS, Burrows B, et al. Quality control of spirometry testing in the registry for patients with severe alpha1-antitrypsin deficiency. Alpha-1 Antitrypsin Deficiency Registry Study Group. Chest 1997;111:899–909.[Web of Science][Medline] [Order article via Infotrieve]
- Swanney MP, Jensen RL, Crichton DA, Beckert LE, Cardno LA, Crapo RO. FEV6 is an acceptable surrogate for FVC in the spirometric diagnosis of airway obstruction and restriction. Am J Respir Crit Care Med 2000;162:917–919.
[Abstract/Free Full Text]
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