A new method for rating dyspnea during exercise in patients with chronic obstructive pulmonary disease.

BACKGROUND: The Borg scale is most commonly used to measure dyspnea in China. However, many patients that find it is difficult to distinguish the labeled numbers corresponding to different dyspnea scores. We developed a new method to rate dyspnea, which we call the count scale (CS). It includes the count scale number (CSN) and count scale time (CST). The aims of the present study were to determine the reproducibility and sensitivity of the CS during exercise in patients with chronic obstructive pulmonary disease (COPD). METHODS: Fourteen male patients with COPD (aged 58.00 ± 7.72 years) participated in this study. A progressive incremental exercise and a 6-minute constant work exercise test were performed every 2 to 3 days for a total of 3 times. The CS results were evaluated at rest and at 30% and 70% of maximal workload (Wmax) and Wmax. The Borg scales were obtained during exercise. RESULTS: No significant differences occurred across the three trials during exercise for the CS and Borg scores. The CSN and CST were more varied at Wmax (coefficient of variation (CV) = (22.28 ± 16.96)% for CSN, CV = (23.08 ± 19.11)% for CST) compared to 30% of Wmax (CV = (11.92 ± 8.78)% for CSN, CV = (11.16 ± 9.96)% for CST) and 70% of Wmax (CV = (9.08 ± 7.09)% for CSN, CV = (12.19 ± 12.32)% for CST). Dyspnea ratings with either CSN or CST tended to decrease at the higher workload compared to the lower workload. CSN and CST scores were highly correlated (r = 0.861, P < 0.001). CSN was negatively correlated with Borg scores (r = -0.363, P = 0.001). Similar results were obtained for the relationship between CST and Borg scores (r = -0.345, P = 0.003). CONCLUSION: We concluded that the CS is simple and reproducible when measuring dyspnea during exercise in patients with COPD.

Upper airway fat tissue distribution in subjects with obstructive sleep apnea and its effect on retropalatal mechanical loads.

OBJECTIVE: To validate the hypothesis that fat tissue accumulation adjacent to the upper airway contributes to a predisposition to obstructive sleep apnea (OSA), irrespective of body mass index (BMI), as well as investigate the effect of the volume of fat tissue on pharyngeal mechanical loads. METHODS: Fourteen subjects and 14 controls were enrolled in this study. Pharyngeal anatomy (the fat tissue volume in the retropalatal region and retroglossal region) were evaluated using magnetic resonance imaging. Whether the subjects had a segmental closing pressure higher than atmospheric pressure was determined by pharyngoscopy under general anesthesia. The difference in fat tissue distribution between subjects with OSA and BMI-matched controls was investigated. Fat tissue distributions in subjects with positive or negative segmental closing pressure were also compared. RESULTS: Significant differences occurred between controls and subjects with OSA in volumes of parapharyngeal fat pad (P = .001), fat of soft palate (P = .01), as well as proportion of the parapharyngeal fat pad to the volume of total lateral pharyngeal soft tissues (P = .004). The volume of pharyngeal cavity, neck circumference, and volume of subcutaneous fat tissues were not significantly different statistically. Volume of fat in soft palate (odds ratio 5.893) and parapharyngeal fat pad in retropalatal and retroglossal region (odds ratios 1.781 and 1.845) were significant predictors of OSA. The volume of fat in the soft palate (P = .003) and parapharyngeal fat pad (P = .002) was higher in participants with positive retropalatal closing pressure; participants with positive retroglossal closing pressure had increased volumes of the tongue (P = .02) and the parapharyngeal fat pad (P = .004). CONCLUSIONS: Patients with OSA have more fat tissue adjacent to the pharyngeal cavity than BMI-matched controls. Fats deposited around the upper airway may contribute to the collapsibility of retropalatal and retroglossal airway in both patients and controls.

Anatomic predictors of retropalatal mechanical loads in patients with obstructive sleep apnea.

BACKGROUND: The retropalatal airway is one of the most collapsible sites during sleep in patients with obstructive sleep apnea (OSA). The primary anatomical contributors to increased collapsibility in the retropalatal segment remain unclear. OBJECTIVES: This study seeks to investigate how the balance between pharyngeal soft tissues and the bony enclosure influences retropalatal mechanical loads in patients with OSA. METHODS: The segmental mechanical load of the retropalatal pharynx was determined by the region's critical closing pressure in 30 anesthetized, paralyzed and intubated subjects with OSA. The volumetric anatomical parameters of the retropalatal airway were evaluated using magnetic resonance imaging, and their associations with retropalatal closing pressures were analyzed. RESULTS: Increased retropalatal closing pressure was associated with the increased proportion of volumetric pharyngeal soft tissues to the surrounding cervicomandibular bony frame (r = 0.791, p < 0.001), enlarged soft tissues of the lateral wall (r = 0.752, p < 0.001) and soft palate (r = 0.726, p < 0.001). The decreased volume of the nasopharynx (r = -0.650, p < 0.001) and pharyngeal cavity (r = -0.653, p < 0.001) indicated a relatively higher retropalatal closing pressure. The multivariate linear regression model demonstrated that the proportion of retropalatal soft tissues to the bony frame and volume of the soft palate predicted 69.4% of the variability in closing pressure (F = 30.674, p < 0.001). CONCLUSIONS: The increased volumetric proportion of pharyngeal soft tissue to the bone enclosure may be an important contributor to increased retropalatal mechanical loads.

Cardiac response and N-terminal-pro-brain natriuretic peptide kinetics during exercise in patients with COPD.

BACKGROUND: COPD increases the risk of cardiovascular problems. Dyspnea on exertion can be associated with COPD or heart failure or both. N-terminal-pro-brain natriuretic peptide (NT-pro-BNP) is a marker of cardiac dysfunction, and exercise testing can identify subtle heart abnormalities. OBJECTIVE: To determine whether cardiac dysfunction adds to the mechanism of dyspnea caused primarily by impaired lung function in patients with mild to moderate COPD. METHODS: With 19 COPD patients and 10 healthy control subjects we measured physiologic variables and collected venous blood samples before and during incremental and constant-work-rate exercise, and measured NT-pro-BNP. RESULTS: Peak oxygen uptake and constant-work exercise time were significantly lower in the COPD group than in the control group (16 ± 4 mL/min/kg vs 19 ± 6 mL/min/kg, P = .04, and 7.8 ± 6.5 min vs 14.8 ± 7.3 min, P = .02). Between the groups there were no significant differences in anaerobic threshold, oxygen pulse (oxygen uptake divided by heart rate), or heart-rate reserve (difference between predicted and measured maximum heart rate). Both at rest and during constant-work exercise, NT-pro-BNP was not significantly higher in the COPD group than in the control group. In the COPD patients there was no significant correlation between constant-work exercise time and NT-pro-BNP at rest or during exercise. CONCLUSIONS: Heart failure did not contribute to exercise intolerance in patients with mild to moderate COPD.