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Background Despite a lack of evidence, ambulatory oxygen therapy is frequently prescribed for patients with interstitial lung disease (ILD) and exertional desaturation. Patients often prefer portable oxygen concentrators to oxygen cylinders. This study aimed to examine the feasibility of conducting a clinical trial of ambulatory oxygen delivered via portable concentrators in patients with ILD. Research Question Is it feasible to conduct a clinical trial of ambulatory oxygen delivered via portable concentrators in patients with ILD? Study Design and Methods In this randomized, triple-blinded, sham-controlled trial, 30 participants with ILD and isolated exertional desaturation to Results Study recruitment was completed within 18 months, with six withdrawals. Participant blinding was successful, with the Bang’s Blinding Index being 0 (95% CI, −0.40 to 0.40) for the oxygen group and 0 (95% CI, −0.42 to 0.42) for the sham group. No significant difference in 6MWD was seen between groups at week 12 (mean difference of −34 m [95% CI, −105 to 36], P = .34). For secondary outcomes, compared with the sham group, the oxygen group had a significantly higher Leicester Cough Questionnaire psychological domain score, indicating better cough-related quality of life (mean difference of 0.9 [95% CI, 0.2 to 1.6], P = .01), but a shorter duration of moderate-to-vigorous activities (mean difference of −135 [95% CI, −267 to −3], P = .04) at week 12. Interpretation Based on the results of this pilot study, a definitive randomized controlled trial with a longer intervention duration is warranted to clarify therapeutic impacts of ambulatory oxygen in patients with ILD. Trial Registry Australian New Zealand Clinical Trials Registry; No.: ACTRN12617000054314; URL: www.anzctr.org.au/

Despite a lack of evidence, ambulatory oxygen therapy is frequently prescribed for patients with interstitial lung disease (ILD) and exertional desaturation. Patients often prefer portable oxygen concentrators to oxygen cylinders. This study aimed to examine the feasibility of conducting a clinical trial of ambulatory oxygen delivered via portable concentrators in patients with ILD.Is it feasible to conduct a clinical trial of ambulatory oxygen delivered via portable concentrators in patients with ILD?In this randomized, triple-blinded, sham-controlled trial, 30 participants with ILD and isolated exertional desaturation to 90% on 6-minute walk tests were randomized to 12-week ambulatory oxygen or air delivered via portable concentrators, with assessments performed at baseline and weeks 4, 12, and 18. Primary outcomes were trial feasibility and the change in 6-minute walk distance (6MWD) on room air at week 12.Study recruitment was completed within 18 months, with six withdrawals. Participant blinding was successful, with the Bang's Blinding Index being 0 (95% CI, -0.40 to 0.40) for the oxygen group and 0 (95% CI, -0.42 to 0.42) for the sham group. No significant difference in 6MWD was seen between groups at week 12 (mean difference of -34 m [95% CI, -105 to 36], P = .34). For secondary outcomes, compared with the sham group, the oxygen group had a significantly higher Leicester Cough Questionnaire psychological domain score, indicating better cough-related quality of life (mean difference of 0.9 [95% CI, 0.2 to 1.6], P = .01), but a shorter duration of moderate-to-vigorous activities (mean difference of -135 [95% CI, -267 to -3], P = .04) at week 12.Based on the results of this pilot study, a definitive randomized controlled trial with a longer intervention duration is warranted to clarify therapeutic impacts of ambulatory oxygen in patients with ILD.Australian New Zealand Clinical Trials Registry; No.: ACTRN12617000054314; URL: www.anzctr.org.au/.

The 6-min walk distance (6MWD), a widely used test of functional capacity, has limited evidence of construct validity among patients surviving acute respiratory failure (ARF) and ARDS. The objective of this study was to examine construct validity and responsiveness and estimate minimal important difference (MID) for the 6MWD in patients surviving ARF/ARDS.For this secondary data analysis of four international studies of adult patients surviving ARF/ARDS (N = 641), convergent and discriminant validity, known group validity, predictive validity, and responsiveness were assessed. MID was examined using anchor- and distribution-based approaches. Analyses were performed within studies and at various time points after hospital discharge to examine generalizability of findings.The 6MWD demonstrated good convergent and discriminant validity, with moderate to strong correlations with physical health measures (|r| = 0.36-0.76) and weaker correlations with mental health measures (|r| = 0.03-0.45). Known-groups validity was demonstrated by differences in 6MWD between groups with differing muscle strength and pulmonary function (all P.01). Patients reporting improved function walked farther, supporting responsiveness. 6MWD also predicted multiple outcomes, including future mortality, hospitalization, and health-related quality of life. The 6MWD MID, a small but consistent patient-perceivable effect, was 20 to 30 m. Findings were similar for 6MWD % predicted, with an MID of 3% to 5%.In patients surviving ARF/ARDS, the 6MWD is a valid and responsive measure of functional capacity. The MID will facilitate planning and interpretation of future group comparison studies in this population.

and study objectives: Patients with end-stage cystic fibrosis (CF) develop respiratory failure and hypercapnia. In contrast to COPD patients, altered electrolyte transport and malnutrition in CF patients may predispose them to metabolic alkalosis and, therefore, may contribute to hypercapnia. The aim of this study was to determine the prevalence of metabolic alkalosis in adults with hypercapnic respiratory failure in the setting of acute exacerbations of CF compared with COPD.Levels of arterial blood gases, plasma electrolytes, and serum albumin from 14 consecutive hypercapnic CF patients who had been admitted to the hospital with a respiratory exacerbation were compared with 49 consecutive hypercapnic patients with exacerbations of COPD. Hypercapnia was defined as a PaCO(2) ofor = 45 mm Hg.Despite similar PaCO(2) values, patients in the CF group were significantly more alkalotic than were those in the COPD group (mean [+/- SD] pH, 7.43 +/- 0.03 vs 7.37 +/- 0.05, respectively; p0.01). A mixed respiratory acidosis and metabolic alkalosis was evident in 71% of CF patients and 22% of COPD patients (p0.01). The mean concentrations of plasma chloride (95.1 +/- 4.9 vs 99.8 +/- 5.2 mmol/L, respectively; p0.01) and sodium (136.5 +/- 2.8 vs 140.4 +/- 4.5 mmol/L, respectively; p0.01) were significantly lower in the CF group, and the levels of serum albumin were significantly reduced (27.4 +/- 5.8 vs 33.7 +/- 4.8 mmol/L, respectively; p0.01).Metabolic alkalosis contributes to hypercapnic respiratory failure in adults with acute exacerbations of CF. This acid-base disturbance occurs in conjunction with reduced total body salt levels and hypoalbuminemia.

Background Tidal expiratory flow limitation (EFL) contributes to chronic dyspnea and exercise intolerance in COPD patients. It can be assessed with the negative expiratory pressure (NEP) technique and is expressed as either the percentage of the tidal volume over which EFL occurs (EFL%V t ) or according to more detailed three-point or five-point scoring systems. The aim of this study was to evaluate the reproducibility of the NEP technique in COPD patients. Methods Tidal EFL was evaluated with NEP in 18 subjects with stable COPD (FEV 1 range, 18 to 75% predicted) on two occasions (mean retest interval, 8.2 days) by the same rater. Agreement between testing occasions was assessed with the κ statistic for the 3-point and 5-point EFL scores, and with the coefficient of repeatability for EFL%V t . Results On the first testing occasion, nine subjects had no EFL, four subjects had EFL in the supine position, and five subjects had EFL in the sitting and the supine position. Using the 3-point score, agreement was present in 14 of 18 subjects at time 2 (κ = 0.66), indicating substantial agreement. Using the 5-point score, agreement was seen in 13 of 18 subjects (κ = 0.61), also indicating substantial agreement. The reproducibility of EFL%V t measurements was lower than that required to reliably detect clinical change in both the sitting and supine positions (coefficient of repeatability, 37% and 58%, respectively). Conclusions The 3-point and 5-point scores provide a reproducible assessment of EFL in COPD patients. The classification of EFL as a percentage of tidal volume is less reproducible, and large changes are required to be confident that real clinical change has occurred.