We measured the oxygen cost of breathing (VO2resp) in 13 patients with cardiorespiratory disease requiring artificial ventilation as the difference between the oxygen consumption during spontaneous respiration (VO2tot) and that during artificial ventilation (VO2nonresp). Average VO2tot was 312 +/- 90 ml/min (mean +/- 1 SD), whereas VO2nonresp was 246 +/- 38 ml/min (p less than 0.01). Average VO2resp was 75 +/- 82 ml/min (range, 8 to 286), representing 24% of VO2tot or 8.7 +/- 8.9 ml O2/L ventilation. In normal resting adults, VO2resp in 5 to 10 ml/min, about 1 to 3% VO2tot, or 0.25 to 2.5 ml O2/L ventilation. The VO2resp had an exponential relationship with FEV1 (r = 0.97) in 6 patients who had had prior spirometry. Because minute ventilation was normal in our patients (8.8 +/- 2.2 L/min), the elevated VO2resp represented an increase in the work of breathing as well as a decrease in the efficiency of the respiratory muscles. These results suggest that, where O2 transport is compromised, artificial ventilation may release substantial quantities of oxygen for use by other body systems.
PMID: 7091914 DOI: 10.1164/arrd.1982.126.1.9

The contribution of muscle strength to symptom intensity and work capacity was examined in normal individuals and patients with cardiorespiratory disorders. Respiratory muscle strengths (maximal inspiratory and expiratory pressures) and peripheral muscle strengths (leg extension, leg flexion, seated bench press, and seated row) were measured in 4,617 subjects referred for clinical exercise testing. Subjects then rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain (Borg scale) during an incremental exercise task (100 kpm/min each minute) to capacity on a cycle ergometer. Subjects were classified into groups on the basis of pulmonary function, drug therapy for cardiac disorders, and the presence of chest pain during exercise with electrocardiographic changes indicative of myocardial ischemia. Respiratory and peripheral muscle strengths, normalized for differences in age, sex, and height, were significantly reduced in patients with cardiorespiratory disorders compared with normal individuals. Muscle strength was a significant contributor to symptom intensity and work capacity in both health and disease; a two-fold increase in muscle strength was associated with a 25 to 30% decrease in the intensity of both leg effort and dyspnea and a 1.4- to 1.6-fold increase in work capacity. These results emphasize the need for an integrative approach in the assessment and therapeutic management of exercise intolerance, which considers the contribution of muscle weakness to excessive symptoms and reduced work capacity, in addition to the contribution of ventilatory, gas exchange, and circulatory impairments.
PMID: 8520771 DOI: 10.1164/ajrccm.152.6.8520771

骨格筋の機能不全はCOPD患者に活動の低下をもたらす。COPDの必要な管理として、肺リハビリテーション（PR）は呼吸困難と疲労の軽減、運動耐性と健康な生活の改善、さらに、COPD患者の入院と死亡を減らすことができる。運動はPRの重要な要素であり、運動評価や訓練療法で構成されている。臨床診療におけるPRの応用を評価するために、この論文はCOPD患者のための運動測定と運動トレーニングの一般的な方法を要約した。運動評価では、患者の症状、持久力、筋力、及び健康的な生活の質を計算するべきである。計算後、具体的な訓練療法を開発する必要がある。その中に、持久力、筋力、及び呼吸訓練などが含まれる。このレビューでは、各モダリティの運動トレーニングの詳細について説明する。COPD患者に様々なPRの方法や療法が使用されてきたが、個別化のトレーニング処方が目標である。各段階でCOPD患者に対する運動トレーニングの長期的な利益の効果を検証し、その証拠を裏付けるために、より多くの研究が保証されている。
PMCID: PMC6027710 PMID: 29983556 doi: 10.2147/COPD.S167098

Skeletal muscle dysfunction leads to reduction in activity in patients with COPD. As an essential part of the management of COPD, pulmonary rehabilitation (PR) alleviates dyspnea and fatigue, improves exercise tolerance and health-related quality of life, and reduces hospital admissions and mortality for COPD patients. Exercise is the key component of PR, which is composed of exercise assessment and training therapy. To evaluate PR’s application in clinical practice, this article summarizes the common methods of exercise measurement and exercise training for patients with COPD. Exercise assessments should calculate patients’ symptoms, endurance, strength, and health-related quality of life. After calculation, detailed exercise therapies should be developed, which may involve endurance, strength, and respiratory training. The detailed exercise training of each modality is mentioned in this review. Although various methods and therapies of PR have been used in COPD patients, developing an individualized exercise training prescription is the target. More studies are warranted to support the evidence and examine the effects of long-term benefits of exercise training for patients with COPD in each stage.
Indian Journal of Respiratory Care | Volume 7 | Issue 2 | July-December 2018
PMCID: PMC6027710 PMID: 29983556 doi: 10.2147/COPD.S167098

RATIONALE: Respiratory muscle weakness is common in critically ill patients; the role of targeted inspiratory muscle training (IMT) in intensive care unit rehabilitation strategies remains poorly defined.
OBJECTIVES: The primary objective of the present study was to describe the range and tolerability of published methods for IMT. The secondary objectives were to determine whether IMT improves respiratory muscle strength and clinical outcomes in critically ill patients.
METHODS: We conducted a systematic review to identify randomized and nonrandomized studies of physical rehabilitation interventions intended to strengthen the respiratory muscles in critically ill adults. We searched the MEDLINE, Embase, HealthSTAR, CINAHL, and CENTRAL databases (inception to September Week 3, 2017) and conference proceedings (2012 to 2017). Data were independently extracted by two authors and collected on a standardized report form.
RESULTS: A total of 28 studies (N = 1,185 patients) were included. IMT was initiated during early mechanical ventilation (8 studies), after patients proved difficult to wean (14 studies), or after extubation (3 studies), and 3 other studies did not report exact timing. Threshold loading was the most common technique; 13 studies employed strength training regimens, 11 studies employed endurance training regimens, and 4 could not be classified. IMT was feasible, and there were few adverse events during IMT sessions (nine studies; median, 0%; interquartile range, 0-0%). In randomized trials (n = 20), IMT improved maximal inspiratory pressure compared with control (15 trials; mean increase, 6 cm H2O; 95% confidence interval [CI], 5-8 cm H2O; pooled relative ratio of means, 1.19; 95% CI, 1.14-1.25) and maximal expiratory pressure (4 trials; mean increase, 9 cm H2O; 95% CI, 5-14 cm H2O). IMT was associated with a shorter duration of ventilation (nine trials; mean difference, 4.1 d; 95% CI, 0.8-7.4 d) and a shorter duration of weaning (eight trials; mean difference, 2.3 d; 95% CI, 0.7-4.0 d), but confidence in these pooled estimates was low owing to methodological limitations, including substantial statistical and methodological heterogeneity.
CONCLUSIONS: Most studies of IMT in critically ill patients have employed inspiratory threshold loading. IMT is feasible and well tolerated in critically ill patients and improves both inspiratory and expiratory muscle strength. The impact of IMT on clinical outcomes requires future confirmation."
Keywords: artificial respiration, weaning, respiratory muscles, physical therapy, inspiratory muscle training
Annals of the American Thoracic Society. 2018 Jun; 15(6): 735–744.
PMCID: PMC6137679 PMID: 29584447 doi: 10.1513/AnnalsATS.201712-961OC