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Background: Persistent bronchodilator response (BDR) following diagnosis of asthma is an underrecognized treatable trait, associated with worse lung function and asthma control. The forced oscillation technique (FOT) measures respiratory system impedance, and BDR cutoffs have been proposed for healthy adults; however, the relevance in asthma is unknown. We compared BDR cutoffs, using FOT and spirometry, in asthma and the relationship with asthma control.Methods: Data from patients with asthma who withheld bronchodilator medication for at least 8 h before a tertiary airway clinic visit were reviewed. All subjects performed FOT and spirometry before and after salbutamol administration, and completed the Asthma Control Test. FOT parameters examined included respiratory system resistance (R5) and reactance (X5) at 5 Hz, and area under the reactance curve (AX). BDR was defined by standard recommendations for spirometry and based on the 95th percentile of BDR in healthy adults for FOT.Results: Fifty-two subjects (18 men; mean age, 53 ± 18 years) were included. BDR was identified more frequently by FOT than spirometry (54% vs 27% of subjects). BDR assessed by X5 and AX, but not R5, was associated with spirometric BDR (χ2, P < .01) and correlated with asthma control (X5: rs = -0.36, P < .01; AX: rs = 0.34, P = .01). BDR measured by reactance parameters identified more subjects with poor asthma control than did spirometry (AX, 69% vs spirometry, 41%).Conclusions: BDR assessed by FOT can identify poor asthma control. Reactance parameters were more sensitive in identifying poor asthma control than spirometry, supporting the use of FOT to complement spirometry in the clinical management of asthma. [ABSTRACT FROM AUTHOR]

Background: Limited data are available comparing air travel with the hypoxia inhalation test (HIT) in passengers with COPD. The aim of this study was to assess the predictive capability of the HIT to in-flight hypoxemia in passengers with COPD. Methods: Thirteen passengers (seven female passengers) with COPD (mean [+/- SD], FEV(1)/FVC ratio, 44 +/- 17%) volunteered for this study. Respiratory function tests were performed preflight. Pulse oximetry, cabin pressure, and dyspnea were recorded in flight. The HIT and a 6-min walk test were performed postflight. The in-flight oxygenation response was compared to the HIT results and respiratory function parameters. Results: All subjects flew without the use of oxygen, and no adverse events were recorded in-flight (mean cabin altitude, 2,165 m; altitude range, 1,892 to 2,365 m). Air travel caused significant desaturation (mean preflight oxygen saturation, 95 +/- 1%; mean in-flight oxygen saturation, 86 +/- 4%), which was worsened by activity (nadir pulse oximetric saturation [Spo(2)], 78 +/- 6%). The HIT caused mean desaturation that was comparable to that of air travel (84 +/- 4%). The mean in-flight partial pressure of inspired oxygen (Pio(2)) was higher than the HIT Pio(2) (113 +/- 3 mm Hg vs 107 +/- 1 mm Hg, respectively; p < 0.001). The HIT Spo(2) showed the strongest correlation with in-flight Spo(2) (r = 0.84; p < 0.001). Conclusion: Significant in-flight desaturation can be expected in passengers with COPD. The HIT results compared favorably with the air travel data, with differences explainable by Pio(2) and physical activity. The HIT is the best widely available laboratory test to predict in-flight hypoxemia. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Lung density changes with growth and inflation," by R. H. Brown and colleagues in the October 2015 issue.