Endoscopic lung volume reduction (ELVR) in COPD: Changes in lung mechanics with ELVR using the forced oscillation technique (FOT)

This paper examines potential physiological mechanisms responsible for improvement after lung volume reduction surgery (LVRS). In 25 patients (63 ± 9 yr; 11 men, 14 women), spirometry [forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC)], lung volumes [residual volume (RV) and total lung capacity (TLC)], small airway resistance, recoil pressures, and respiratory muscle contractility (RMC) were measured before and 4–6 mo after LVRS. Data were interpreted to assess how changes in each component of lung mechanics affect overall function. Among responders (ΔFEV1 ≥ 12%; 150 ml), improvement was primarily due to an increase in FVC, not to FEV1-to-FVC ratio. Among nonresponders, FEV1, FVC, and RV/TLC did not change after surgery, although recoil pressure increased in both groups. Both groups experienced a reduction in RMC after LVRS. In conclusion, LVRS improves function in emphysema by resizing the lung relative to the chest wall by reducing RV. LVRS does not change airway resistance but decreases RMC, which attenuates the potential benefits of LVRS that are generated by reducing RV/TLC. Among nonresponders, recoil pressure increased out of proportion to reduced volume, such that no increase in vital capacity or improvement in FEV1 occurred.

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Early onset of airway derecruitment assessed using the forced oscillation technique in subjects with asthma

Journal of Applied Physiology ◽

10.1152/japplphysiol.00534.2018 ◽

2019 ◽

Vol 126 (5) ◽

pp. 1399-1408 ◽

Cited By ~ 3

Author(s):

Kris Nilsen ◽

Francis Thien ◽

Cindy Thamrin ◽

Matt J. Ellis ◽

G. Kim Prisk ◽

...

Keyword(s):

Lung Volume ◽

Forced Oscillation ◽

Lung Mechanics ◽

Control Group ◽

Forced Oscillation Technique ◽

Rapid Reduction ◽

Control Subjects ◽

Volume Curve ◽

Volume Relationship ◽

Highly Correlated

Derecruitment of air spaces in the lung occurs when airways close during exhalation and is related to ventilation heterogeneity and symptoms in asthma. The forced oscillation technique has been used to identify surrogate measures of airway closure via the reactance (Xrs) versus lung volume relationship. This study used a new algorithm to identify derecruitment from the Xrs versus lung volume relationship from a slow vital capacity maneuver. We aimed to compare two derecruitment markers on the Xrs versus volume curve, the onset reduction of Xrs (DR1vol) and the onset of more rapid reduction of Xrs (DR2vol), between control and asthmatic subjects. We hypothesized that the onset of DR1vol and DR2vol occurred at higher lung volume in asthmatic subjects. DR1vol and DR2vol were measured in 18 subjects with asthma and 18 healthy controls, and their relationships with age and height were examined using linear regression. In the control group, DR1vol and DR2vol increased with age ( r2 = 0.68, P < 0.001 and r2 = 0.71, P < 0.001, respectively). DR1vol and DR2vol in subjects with asthma [76.58% of total lung capacity (TLC) and 56.79%TLC, respectively] were at higher lung volume compared with control subjects (46.1 and 37.69%TLC, respectively) ( P < 0.001). DR2vol correlated with predicted values of closing capacity ( r = 0.94, P < 0.001). This study demonstrates that derecruitment occurs at two points along the Xrs-volume relationship. Both derecruitment points occurred at significantly higher lung volumes in subjects with asthma compared with healthy control subjects. This technique offers a novel way to measure the effects of changes in airways/lung mechanics. NEW & NOTEWORTHY This study demonstrates that the forced oscillation technique can be used to identify two lung volume points where lung derecruitment occurs: 1) where derecruitment is initiated and 2) where onset of rapid derecruitment commences. Measurements of derecruitment increase with age. The onset of rapid derecruitment was highly correlated with predicted closing capacity. Also, the initiation and rate of derecruitment are significantly altered in subjects with asthma.

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