Functionally relevant threshold of inspiratory muscle strength in patients with chronic obstructive pulmonary disease. (November 2021)

• Record Type: Journal Article
• Authors: Iwakura, Masahiro; Wakasa, Masahiko; Okura, Kazuki; Kawagoshi, Atsuyoshi; Sugawara, Keiyu; Takahashi, Hitomi; Shioya, Takanobu
• Is Part Of: Respiratory medicine. Volume 188(2021)
• Publication Date: 2021-11
• Subjects: Chronic obstructive -- Exercise tolerance -- Muscle strength -- Pulmonary disease -- Respiratory muscles; Chest -- Diseases -- Periodicals; Chest -- Diseases -- Great Britain -- Periodicals; Respiratory organs -- Diseases -- Periodicals; Respiratory Tract Diseases -- Periodicals; Appareil respiratoire -- Maladies -- Périodiques; Thorax -- Maladies -- Périodiques; Appareil respiratoire -- Maladies -- Traitement -- Périodiques; Electronic journals; 616.2
• DOI: 10.1016/j.rmed.2021.106625
• Languages: English
• ISSNs: 0954-6111

Abstract

Abstract : Objectives: We aimed to identify the inspiratory muscle strength thresholds below which exercise capacity is compromised in men with chronic obstructive pulmonary disease (COPD). Methods: We measured the maximum static inspiratory mouth pressure (PImax) and the percentage of predicted values (%PImax) in 113 patients with COPD. Six-minute walk distance (6-MWD) was measured as an indicator of functional exercise capacity, and a 6-MWD of <350 m was defined as functional exercise intolerance. Thresholds were determined as values with high specificity (>0.90) and maximal sensitivity. Statistical significance was set at P < 0.01. Results: The data of 96 patients (74 ± 6 years old; forced expiratory volume in 1-s [FEV1 ], 56.5 ± 26.2% predicted) were analyzed; three women and 14 participants with missing data were excluded. Multivariate logistic regression models identified significant associations of PImax (odds ratio at 99% confidence interval [CI]: 0.95 [0.92–0.98]) and %PImax (odds ratio at 99% CI: 0.97 [0.95–0.99]) with 6-MWD, after adjustments for height and FEV1 . C-statistics showed that the area under the curves (99% CI) of PImax and %PImax were comparable (0.87 [0.77–0.96] and 0.83 [0.72–0.94]). The thresholds of PImax and %PImax were 45.1 cmH2 O and 66%; PImax and %PImax also had moderate positive likelihood ratios of 4.44 and 5.00. Conclusions: Thresholds of inspiratory muscle strength in men with COPD could help clinicians evaluate whether their patient's inspiratory muscle strength is inadequate to achieve a 6-MWD of ≥350 m, and identify patients who should be targeted for inspiratory muscle training. Highlights: Inspiratory muscle weakness was associated with poor 6-MWD of <350 m in COPD. Functional exercise tolerance was compromised below PImax threshold 45.1 cmH2 O. PImax <45.1 cmH2 O implied post-test probability of poor 6-MWD in most COPD cases. PImax threshold identifies COPD patients targeted for inspiratory muscle training. PImax threshold can be used as a screening tool for exercise capacity assessment.