Study design and subject description
This is a retrospective, observational, longitudinal, follow-up study. The CLE test was developed by our institution in 2002, and reliability and validity in relation to EILO has been assessed in later studies [7, 12]. Since 2002, a majority of patients presenting with the symptoms of inspiratory stridor during exercise have been offered examination with this test. Patients with confirmed EILO were given information about their condition including a review of the video recording from their test. All the patients were given standardized treatment advise focusing mainly on breathing techniques during exercise, hereafter called conservative treatment (CT) [8, 9].
In the period 2003–2008, patients who demonstrated severe supraglottic EILO were offered laser supraglottoplasty as previously described, hereafter called as surgical treatment (ST). Instructive figures to illustrate our approach have been published previously . The selection of patients for surgery was based on the airflow limitation through the laryngeal inlet due to abnormal anatomy and/or inexpedient motion of the aryepiglottic folds during forced respiration. Patients were offered surgical treatment based on the following criteria: presence of any anatomical abnormality, e.g. prominent cuneiform tubercles in the aryepiglottic folds, and or severe obstruction of the laryngeal inlet, as well as the severe EILO caused-symptoms and motivation for treatment.
Subjects showing only a slight inward collapse of supraglottic structures, but no glottic adduction during maximal exercise were considered as non-EILO patients based on the observations from previous studies and, therefore, not included in this study [1, 7, 11, 12].
In total, 114 patients were diagnosed with EILO by the CLE test between 2002 and 2008. Among these, 20 showed predominantly glottic adduction, whereas 94 showed predominantly supraglottic adduction either alone or followed by a glottic adduction. As surgery was only done among the subjects in this latter group, these 94 were included in the present follow-up study performed 2–5 years (mean 3.6) after the primary diagnosis. Of these patients, 23 were treated with ST, while 71 were given only CT. All these patients were invited to answer a questionnaire considering the current level of respiratory distress during exercise, level of athletic activity, changes in activity since diagnosis, change of respiratory symptoms since the first CLE test, as well as the present consequences for social interaction. Indicated response categories were given in a five step Likert scale. A visual analogue score (VAS) was also used to respond to questions about symptom severity.
A subgroup of 23 CT patients, diagnosed 2002–2005, was offered a second CLE test 2–5 years after the first CLE test. Most of these patients were first examined with CLE test before ST was introduced, and may, thus, be considered as natural course historical controls. Fourteen of these patients were re-tested at average of 52 months after the diagnostic CLE test. They matched the surgically treated patients relatively well with respect to age, gender and primary CLE score. Figure 1 gives an overview. Asthma was either ruled out or treated adequately before entering the study .
The study was approved by the Committee on Medical Research Ethics of Western Norway, and informed written consent was obtained from all the patients.
Classification and grading of EILO according to CLE test score
Videos from all CLE tests were presented randomly and unidentifiable to an experienced laryngologist and scored by the CLE-score method as previously described by Maat et al. . In short, adduction of supraglottic and glottic structures of the larynx were scored ranging from normal (0) to maximal adduction (3) twice during test; i.e. at moderate, and maximal effort. This creates four sub-scores labelled A through D and a sum score E. Glottic adductions are represented by A (moderate effort) and C (maximal effort), whereas supraglottic adductions are represented by B (moderate effort) and D (maximal effort). We have defined EILO by CLE test sum score E > 2, whereas glottic EILO was defined by C > D and supraglottic EILO was defined by D ≥ C .
In order to compare the observations between the two groups ANOVA analyses of variance were used. Confounding variables, i.e. age, gender, and CLE score were added as co-variables. Comparison of CLE scores before versus after surgery and the first versus second CLE test was analyzed by repeated measure t tests. The Wilcoxon Sign Rank test and the Mann–Whitney test were used in order to validate t test statistics. The calculations were performed with the statistical program SPSS 17.0 (SPSS Science, Chicago, IL, USA). P values <0.05 were considered significant.