Qualitative aspects of exertional dyspnea in patients with interstitial lung disease

We compared qualitative and quantitative aspects of perceived exertional dyspnea in patients with interstitial lung disease (ILD) and normal subjects and sought a physiological rationale for their differences. Twelve patients with ILD [forced vital capacity = 64 +/- 4 (SE) %predicted] and 12 age-matched normal subjects performed symptom-limited incremental cycle exercise tests with measurements of dyspnea intensity (Borg scale), ventilation, breathing pattern, operational lung volumes, and esophageal pressures (Pes). Qualitative descriptors of dyspnea were selected at exercise cessation. Both groups described increased "work and/or effort" and "heaviness" of breathing; only patients with ILD described "unsatisfied inspiratory effort" (75%), "increased inspiratory difficulty" (67%), and "rapid breathing" (58%) (P < 0.05 patients with ILD vs. normal subjects). Borg-O2 uptake (VO2) and Borg-ventilation slopes were significantly greater during exercise in patients with ILD (P < 0.01). At peak exercise, when dyspnea intensity and inspiratory effort (Pes-to-maximal inspiratory pressure ratio) were similar, the distinct qualitative perceptions of dyspnea in patients with ILD were attributed to differences in dynamic ventilatory mechancis, i.e., reduced inspiratory capacity, heightened Pes-to-tidal volume ratio, and tachypnea. Factors contributing to dyspnea intensity in both groups were also different: the best correlate of the Borg-VO2 slope in patients with ILD was the resting tidal volume-to-inspiratory capacity ratio (r = 0.58, P < 0.05) and in normal subjects was the slope of Pes-to-maximal inspiratory pressure ratio over VO2 (r = 0.60, P < 0. 05).

Vocal cord paralysis and respiratory muscle weakness: an unusual presentation of chronic polyneuropathy

A case of chronic polyneuropathy that manifested with an unusual combination of vocal cord paralysis and respiratory muscle weakness is reported. In addition, results of an exercise test carried out to assess the severity and mechanisms of exertional breathlessness in this unique condition with combined obstructive and restrictive disorders are described.

Qualitative aspects of exertional breathlessness in chronic airflow limitation: pathophysiologic mechanisms

We compared qualitative aspects of the sensory experience of exertional breathlessness in normal subjects and in patients with chronic airflow limitation (CAL) and sought a physiologic rationale for these. Twelve patients (66 +/- 2 yr of age, mean +/- SEM) with severe CAL (FEV1 = 37 +/- 5% predicted) and 12 age-matched normal subjects (FEV1 = 103 +/- 5% predicted) were studied. Perceived inspiratory difficulty (BorgIN), inspiratory effort (esophageal pressure expressed as a fraction of maximal esophageal pressure at isovolume [Pes/PImax]), breathing pattern, and operational lung volumes (end-expiratory/inspiratory lung volumes [EELV/EILV]) were measured during symptom-limited incremental cycle exercise testing and compared at a standard VO2 of 50% predicted maximum in normal subjects and in patients with CAL. Qualitative descriptors of breathlessness were selected immediately after exercise. Breathlessness was qualitatively different between normal subjects and patients with CAL. Both normal subjects and patients with CAL chose descriptors of increased "work/effort" and "heaviness" of breathing; however, only patients with CAL consistently chose descriptors denoting "increased inspiratory difficulty" (75%), "unsatisfied inspiratory effort" (75%), and "shallow breathing" (50%). Stepwise regression analysis identified the ratio of Pes/PImax to VT/predicted VC as the strongest correlate of standardized BorgIN (n = 24, r = 0.86, p < 0.001). This latter measurement, which reflects the relationship between effort and ventilatory output, correlated strongly with dynamic EELV/TLC at isotime (r = 0.78, p < 0.001). In conclusion, the qualitatively discrete respiratory sensations of exertional inspiratory difficulty peculiar to patients with CAL may have their origins in thoracic hyperinflation and the resultant disparity between inspiratory effort and ventilatory output.

Mechanisms of relief of exertional breathlessness following unilateral bullectomy and lung volume reduction surgery in emphysema

STUDY OBJECTIVE

To explore mechanisms of relief of exertional breathlessness following surgery to reduce thoracic gas volume in patients with emphysema.

MATERIALS AND METHODS

We studied 8 patients with emphysema (FEV1 = 39 +/- 3% predicted; residual volume [RV] = 234 +/- 12% predicted; mean +/- SEM) who were severely breathless despite optimal pharmacotherapy and who underwent unilateral bullectomy for giant bullae (greater than one third hemithorax); 4 of these also had ipsilateral lung reduction (pneumectomy). Pulmonary function and cycle exercise performance (n = 6) were evaluated before and 13 +/- 3 weeks after surgery. Chronic breathlessness was measured with the Baseline Dyspnea Index and the Medical Research Council dyspnea scale. Exertional breathlessness was measured using Borg ratings at a standardized work rate (BorgSTD).

RESULTS

FEV1, FVC, and maximal inspiratory pressures increased postsurgery by 29 +/- 7% (p < 0.05), 24 +/- 10% (p = 0.06), and 39 +/- 12% (p < 0.01), respectively. Plethysmographic total lung capacity, RV, and functional residual capacity fell by 14 +/- 2%, 30 +/- 4%, and 18 +/- 3%, respectively (p < 0.001). All measures of chronic breathlessness improved significantly (p < 0.05). During exercise at a standardized work rate, BorgSTD fell 45% (p < 0.05), end-expiratory lung volume (EELV) fell 22% (p < 0.01), and breathing frequency (F) fell 25% (p = 0.08). By multiple stepwise regression analysis, 99% (p = 0.007) of the variance in symptom relief (delta BorgSTD) was explained by the combination of decreased ratio of the end-expiratory lung volume to total lung capacity, decreased F, and diminished mechanical constraints on tidal volume (tidal volume to vital capacity ratio).

CONCLUSION

Reduced exertional breathlessness at a given workload after volume reduction surgery was attributed to a combination of reduced thoracic hyperinflation, reduced F, and reduced mechanical constraints on lung volume expansion.