Test of incremental respiratory endurance (TIRE) in patients with cardiovascular disease: agreement, reliability and validity analysis

Abstract

Purpose To assess agreement among three instruments for maximal inspiratory pressure (MIP) measurement; evaluate intra- and inter-rater reliability of inspiratory performance measures using Test of Incremental Respiratory Endurance (TIRE); examine their convergent validity; and analyze associations between inspiratory performance and peak oxygen consumption (VO(2)peak) in individuals with CVD. Materials and methods This cross-sectional study included 51 individuals with CVD (mean age 62.0 +/- 9.9 years; 56% male; 70% ischemic etiology). Participants underwent clinical evaluation, body composition via dual-energy X-ray absorptiometry, transthoracic echocardiography, cardiopulmonary exercise testing, spirometry, and inspiratory muscle performance testing. Agreement, reliability, and validity analyses were conducted using standardized rest intervals. Results No significant differences in MIP mean values were observed among the three devices (p = 0.22). Agreement analysis demonstrated good concordance between devices, with intraclass correlation coefficients(ICC) ranging from 0.84 to 0.88 across device pairs (p < 0.001). TIRE showed good to excellent intra- and inter-rater reliability (ICC: 0.76-0.97) and strong convergent validity (r = 0.66-0.88, p < 0.001). SMIP showed a stronger correlation with VO(2)peak (r = 0.60, p = 0.001) than MIP. Conclusions TIRE is a reliable and valid tool for assessing inspiratory muscle strength and performance. SMIP may serve as a functional marker of aerobic capacity in individuals with CVD.