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The article discusses the role of pulmonary function tests (PFTs) in managing connective tissue diseases (CTDs) that affect the respiratory system. PFTs can help recognize respiratory involvement and assist in the management of CTDs. The most common respiratory complications of CTDs are interstitial lung disease (ILD) and pulmonary hypertension, but other manifestations such as airway disease, pleurisy, and respiratory muscle weakness can also occur. Different CTDs have specific patterns of respiratory involvement, and routine PFTs are recommended to assess progression in CTD-ILD. The article emphasizes the importance of interpreting testing results in conjunction with clinical, laboratory, and imaging findings. [Extracted from the article]

Rationale: Ventilatory demand-capacity imbalance, as inferred based on a low ventilatory reserve, is currently assessed only at peak cardiopulmonary exercise testing (CPET). Peak ventilatory reserve, however, is poorly sensitive to the submaximal, dynamic mechanical ventilatory abnormalities that are key to dyspnea genesis and exercise intolerance. Objectives: After establishing sex- and age-corrected norms for dynamic ventilatory reserve at progressively higher work rates, we compared peak and dynamic ventilatory reserve for their ability to expose increased exertional dyspnea and poor exercise tolerance in mild to very severe chronic obstructive pulmonary disease (COPD). Methods: We analyzed resting functional and incremental CPET data from 275 controls (130 men, aged 19-85 yr) and 359 Global Initiative for Chronic Obstructive Lung Disease patients with stage 1-4 obstruction (203 men) who were prospectively recruited for previous ethically approved studies in three research centers. In addition to peak and dynamic ventilatory reserve (12[ventilation / estimated maximal voluntary ventilation]3100), operating lung volumes and dyspnea scores (0-10 on the Borg scale) were obtained. Results: Dynamic ventilatory reserve was asymmetrically distributed in controls; thus, we calculated its centile distribution at every 20 W. The lower limit of normal (lower than the fifth centile) was consistently lower in women and older subjects. Peak and dynamic ventilatory reserve disagreed significantly in indicating an abnormally low test result in patients: whereas approximately 50% of those with a normal peak ventilatory reserve showed a reduced dynamic ventilatory reserve, the opposite was found in approximately 15% (P,0.001). Irrespective of peak ventilatory reserve and COPD severity, patients who had a dynamic ventilatory reserve below the lower limit of normal at an isowork rate of 40W had greater ventilatory requirements, prompting earlier attainment of critically low inspiratory reserve. Consequently, they reported higher dyspnea scores, showing poorer exercise tolerance compared with those with preserved dynamic ventilatory reserve. Conversely, patients with preserved dynamic ventilatory reserve but reduced peak ventilatory reserve reported the lowest dyspnea scores, showing the best exercise tolerance. Conclusions: Reduced submaximal dynamic ventilatory reserve, even in the setting of preserved peak ventilatory reserve, is a powerful predictor of exertional dyspnea and exercise intolerance in COPD. This new parameter of ventilatory demand-capacity mismatch may enhance the yield of clinical CPET in the investigation of activity-related breathlessness in individual patients with COPD and other prevalent cardiopulmonary diseases. [ABSTRACT FROM AUTHOR]

BACKGROUND: Continuous monitoring of ... throughout the 6-min walk test (6MWT) unveiled that some patients with respiratory diseases may present values across the test lower than ... measured at the end of the test. Nevertheless, it remains unclear whether this approach improves the yield of walk-induced desaturation detection in predicting mortality and hospitalizations in patients with COPD. METHODS: Four hundred twenty-one subjects (51% males) with mild2very severe COPD underwent a 6MWT with continuous measurement of .... Exercise desaturation was defined as a fall in ... ≥ 4%. All-cause mortality was assessed up to 6 y of follow-up and the rate of hospitalizations in the year succeeding the 6MWT. RESULTS: One hundred forty-nine subjects (35.4%) died during a mean (interquartile) follow-up of 55.5 (30.2-64.1) months. Desaturation was observed in 299/421 (71.0%). ... along the test was < end ... (88 [82-92]% vs 90 [84293]%, P < .001). Desaturation detected only during (but not at the end of) the test was found in 81/421 (19.2%) participants. Multivariate Cox regression model adjusted for sex, body composition, FEV1, residual volume/total lung capacity ratio, walk distance, O2 supplementation during the test, and comorbidities retained the presence of desaturation either at the end (1.85 [95% CI 1.0-23.36]) or only along the test (2.08 [95% CI 1.09-4.01]) as significant predictors of mortality. The rate of hospitalizations was higher in those presenting with any kind of desaturation compared to those without exercise desaturation. Logistic regression analysis revealed that walking interruption and diffusing capacity of the lung for carbon monoxide predicted desaturation observed only during the test. CONCLUSIONS: O2 desaturation missed by end-exercise ... but exposed by measurements during the test was independently associated with all-cause mortality and hospitalizations in subjects with COPD. [ABSTRACT FROM AUTHOR]

Blood flow requirements of the respiratory muscles (RM) increase markedly during exercise in chronic heart failure (CHF). We reasoned that if the RM could subtract a fraction of the limited cardiac output (QT) from the peripheral muscles, RM unloading would improve locomotor muscle perfusion. Nine patients with CHF (left ventricle ejection fraction = 26 [+ or -] 7%) undertook constant-work rate tests (70-80% peak) receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes ([DELTA]%) in deoxy-hemoglobyn, oxi-Hb ([[O.sub.2]Hb]), tissue oxygenation index, and total Hb ([Hb.sub.TOT]], an index of local blood volume) in the vastus lateralis were measured by near infrared spectroscopy. In addition, QT was monitored by impedance cardiography and arterial [O.sub.2] saturation by pulse oximetry [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. There were significant improvements in exercise tolerance (Tlim) with PAV. Blood lactate, leg effort/Tlim and dyspnea/Tlim were lower with PAV compared with sham ventilation (P < 0.05). There were no significant effects of RM unloading on systemic 02 delivery as [Q.sub.T] and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] at submaximal exercise and at Tlim did not differ between PAV and sham ventilation (P > 0.05). Unloaded breathing, however, was related to enhanced leg muscle oxygenation and local blood volume compared with sham, i.e., higher [DELTA][[O.sub.2]Hb]% and [DELTA][[Hb.sub.TOT]]%, respectively (P < 0.05). We conclude that RM unloading had beneficial effects on the oxygenation status and blood volume of the exercising muscles at similar systemic [O.sub.2] delivery in patients with advanced CHF. These data suggest that blood flow was redistributed from respiratory to locomotor muscles during unloaded breathing. blood flow; cardiac failure; cardiovascular physiology; hemodynamics; muscle; oxygen consumption

Objective: Impaired respiratory mechanics and gas exchange may contribute to sleep disturbance in patients with COPD. We aimed to assess putative associations of different domains of lung function (airflow limitation, lung volumes, and gas exchange efficiency) with polysomnography (PSG)-derived parameters of sleep quality and architecture in COPD. Methods: We retrospectively assessed data from COPD 181 patients ≥ 40 years of age who underwent spirometry, plethysmography, and overnight PSG. Univariate and multivariate linear regression models predicted sleep efficiency (total sleep time/total recording time) and other PSG-derived parameters that reflect sleep quality. Results: The severity of COPD was widely distributed in the sample (post-bronchodilator FEV1 ranging from 25% to 128% of predicted): mild COPD (40.3%), moderate COPD (43.1%), and severe-very severe COPD (16.6%). PSG unveiled a high proportion of obstructive sleep apnea (64.1%) and significant nocturnal desaturation (mean pulse oximetry nadir = 82.2% ± 6.9%). After controlling for age, sex, BMI, apnea-hypopnea index, nocturnal desaturation, comorbidities, and psychotropic drug prescription, FEV1 /FVC was associated with sleep efficiency (β = 25.366; R2 = 14%; p < 0.001), whereas DLCO predicted sleep onset latency (β = −0.314; R2 = 13%; p < 0.001) and rapid eye movement sleep time/ total sleep time in % (β = 0.085; R2 = 15%; p = 0.001). Conclusions: Pulmonary function variables reflecting severity of airflow and gas exchange impairment, adjusted for some potential confounders, were weakly related to PSG outcomes in COPD patients. The direct contribution of the pathophysiological hallmarks of COPD to objectively measured parameters of sleep quality seems to be less important than it was previously assumed. [ABSTRACT FROM AUTHOR]