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Updated: Jan 6, 2026
Normothermic Negative Pressure Ventilation Ex Situ Lung Perfusion: Evaluation of Lung Function and Metabolism
Published on: February 14, 2022
[Expiratory flow limitation detected by negative expiratory pressure in patients with chronic obstructive pulmonary
Ai-huan Chen1, Rong-chang Chen, Jun-mei Li
1Guangzhou Institute of Respiratory Diseases, First Affiliated Hospital, Guangzhou Medical College, Guangzhou 510120, China.
Objective:
To evaluate the relationship between expiratory flow limitation (EFL) and chronic dyspnea and the effect of bronchodilator on EFL in patients with chronic obstructive pulmonary disease (COPD).
Methods:
Thirty-three ambulatory patients with COPD (46 - 78 yrs; male 31, female 2) were included in this study. The severity of chronic dyspnea was rated according to the dyspnea scale proposed by the Medical Research Council (MRC). EFL was measured by applying negative pressure at the mouth during tidal expiration before and after bronchodilation test (inhalation of 400 microg salbutamol).
Results:
EFL was detected in 12 (36%) of the 33 COPD patients in both seated and supine positions and in 11 (33%) only in supine position. There was a significant difference in the percent predicted forced expired volume in one second (FEV(1%)pred) between subgroups of the patients with or without EFL (t = 7.601, P < 0.01). The mean values of FEV(1%)pred in non-EFL group and EFL group was (66 +/- 16)% and (31 +/- 10)%, respectively, and the value was lowest in patients who showed EFL both in seated and supine positions [(24 +/- 7)%]. Both three-point EFL and five-point EFL were significantly correlated with FEV(1) (r = -0.836 and -0.818, respectively, all P < 0.01). There was a significant correlation between MRC dyspnea scale and three-point EFL and five-point EFL (r = 0.903 and 0.912, respectively, all P < 0.01). In the multiple regression analysis, five-point EFL was a better predictor of dyspnea than FEV(1) (regression coefficient was 0.679 and -0.265, respectively, P < 0.01 and 0.029, respectively). EFL persisted after salbutamol in all of the 23 patients with EFL under baseline conditions.
Conclusions:
EFL as measured by negative expiratory pressure (NEP) technique may be more useful in the evaluation of dyspnea in COPD patients than routine lung function measurements. The EFL in COPD patients is irreversible after bronchodilator administration.
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