Dynamic expiratory tracheal collapse in morbidly obese COPD patients.

Morbid obesity may influence several aspects of airway function. However, the effect of morbid obesity on expiratory tracheal collapse in COPD patients is unknown. We thus prospectively studied 100 COPD patients who underwent full pulmonary function tests (PFTs), 6-minute walk test (6MWT), Saint George's Respiratory Questionnaire (SGRQ), and low-dose CT at total lung capacity and during dynamic exhalation with spirometric monitoring. We examined correlations between percentage dynamic expiratory tracheal collapse and body mass index (BMI). The association between tracheal collapse and BMI was compared to a control group of 53 volunteers without COPD. Patients included 48 women and 52 men with mean age 65 ± 7 years; BMI 30 ± 6; FEV1 64 ± 22% predicted and percentage expiratory collapse 59 ± 19%. Expiratory collapse was significantly associated with BMI (69 ± 12% tracheal collapse among 20 morbidly obese patients with BMI ≥ 35 compared to 57 ± 19% in others, p = 0.002, t-test). In contrast, there was no significant difference in collapse between healthy volunteers with BMI ≥ 35 and < 35. COPD patients with BMI ≥ 35 also demonstrated shorter 6MWT distances (340 ± 139 m vs. 430 ± 139 m, p = 0.003) and higher (worse) total SGRQ scores (48 ± 19 vs. 36 ± 20, p = 0.013) compared to those with BMI < 35. In light of these results, clinicians should consider evaluating for excessive expiratory tracheal collapse when confronted with a morbidly obese COPD patient with greater quality of life impairment and worse exercise performance than expected based on functional measures.

Dynamic expiratory tracheal collapse in COPD: correlation with clinical and physiologic parameters.

BACKGROUND: COPD has been described as a risk factor for excessive expiratory tracheal collapse, but its prevalence and clinical correlates have not been fully determined. The purpose of this study is to prospectively determine the prevalence of excessive expiratory tracheal collapse among patients with COPD and to test the hypothesis that clinical and/or physiologic parameters will correlate with the presence of excessive tracheal collapse. METHODS: We studied 100 adults meeting GOLD (Global Initiative for Obstructive Lung Disease) criteria for COPD, who underwent full pulmonary function tests (PFTs), 6-min walk test (6MWT), St. George's Respiratory Questionnaire (SGRQ), and low-dose CT scan at total lung capacity and during dynamic exhalation with spirometric monitoring. We examined correlations between percentage dynamic expiratory tracheal collapse and PFTs, 6MWT distance, and SGRQ scores. RESULTS: Patients included 48 women and 52 men with mean age 65 ± 7 years, FEV1 64% ± 22% predicted, and percentage expiratory collapse 59% ± 19%. Twenty of 100 participants met study criteria for excessive expiratory collapse. There was no significant correlation between percentage expiratory tracheal collapse and any pulmonary function measure, total SGRQ score, or 6MWT distance. The SGRQ symptom subscale was weakly correlated with percentage collapse of the mid trachea (R = 0.215, P = .03). CONCLUSIONS: Excessive expiratory tracheal collapse is observed in a subset of patients with COPD, but the magnitude of collapse is independent of disease severity and does not correlate significantly with physiologic parameters. Thus, the incidental identification of excessive expiratory tracheal collapse in a general COPD population may not necessarily be clinically significant.

Effect of therapeutic hyperoxia on maximal oxygen consumption and perioperative risk stratification in chronic obstructive pulmonary disease.

BACKGROUND: Maximal consumption of oxygen ( ̇VO(2)max) during exercise is used in patients with chronic obstructive pulmonary disease (COPD) to stratify perioperative risk. However, the impact of therapeutic hyperoxia (i.e., use of supplemental oxygen to prevent hypoxemia during exercise) on ( ̇VO(2)max and other ventilatory parameters during maximal exercise in the resting normoxic COPD population is poorly defined. METHODS: A randomized, double-blind crossover study was performed in which resting normoxic subjects (n=16) with COPD underwent two standard symptom-limited, ramped-protocol bicycle ergometry cardiopulmonary exercise tests >5 days apart with FiO(2) of 0.21 (control) and ~0.28 (therapeutic hyperoxia). ̇VO(2)max and other ventilatory parameters were compared using a paired two-sample t-test. RESULTS: Therapeutic hyperoxia significantly increased ̇VO(2)max (12.2 ± 2.9 vs. 13.6 ± 3.8 ml/kg/min, P = 0.03), partial pressure of end-tidal carbon dioxide, and oxygen saturation and significantly decreased ̇VE-̇VCO(2) slope, but it did not affect exercise time, maximum watts achieved, maximum minute ventilation, or change in end-expiratory lung volume. Three of four subjects with ̇VO(2)max <10 ml/kg/min without supplemental oxygen increased ̇VO(2)max to ≥10 ml/kg/min on therapeutic hyperoxia and potentially changed perioperative risk category. CONCLUSIONS: Therapeutic hyperoxia in a resting normoxic COPD population significantly improves ̇VO(2)max and may change perioperative risk stratification by conventional criteria. Further studies are needed to determine if this change in stratification is appropriate.