Reliability of phonation maximum time and capacity in slow vital healthy subjects

Introduction: The measurement of slow vital capacity (SVC) is important to investigate the occurrence of airway obstruction, assist in preventing and assessing the clinical outcome of respiratory diseases. However, it is necessary to use high cost equipment, as spirometer, whose presence can be scarce in health facilities, emerging the need to seek alternative methods that allow this action in the absence of equipment. Aims and objectives: To evaluate the reliability of maximum phonation time using the counting techniques (CT) and vowel "a" sustained, and compare it to the gold standard by spirometry. Methods: This was a cross-sectional study conducted in healthy students, crossover, where the choice of techniques (spirometry, count technique and vowel "a") was randomly. Data were collected by two examiners on the same day and after a week, to evaluate the test-retest. Results: The study included 30 healthy subjects, 26 (87%) women and 4 (13%) men. The intraclass correlation (ICC) between the days to the first reviewer was 0.906, 0.917 and 0.950 (p <0.005) for the vowel "a", the counting technique and the SVC respectively, and for the second evaluator was 0.910, 0.858 and 0.972 (p <0.005). The ICC between the examiners on the same day and after a week for the vowel "a", the CT and the SVC was 0.913, 0.955, 0.988 (p <0.005) and 0.955, 0.946, 0.962 (p <0.005) respectively. Conclusions: This study found that the phonation techniques with the vowel "a" and counting technique as well as SVC, have excellent reliability, between different examiners and with the same examiners on different days, would be an alternative in the absence of equipment specific.