Effect of Dynamic Airway Compression on Breathing Pattern and Respiratory Sensation in Severe Chronic Obstructive Pulmonary Disease^1–3

Abstract

Patients with severe COPD are frequently flow-limited during expiration at rest. When expiratory flow is at its maximum, application of negative pressure at the mouth should accentuate dynamic compression downstream from the flow-limiting segment (FLS) without substantially affecting flow or pressure upstream. The purpose of this study was to determine the ventilatory response to such intervention and to determine its effect on respiratory sensation. Such responses should reflect the effect of airway receptors downstream from the FLS. Nine patients with severe COPD (FEV, ± SE = 27 ± 3% predicted) breathed into a closed-circuit apparatus that incorporated a rolling-seal spirometer. The spirometer was fitted with a linear actuator that caused mouth pressure to become negative in proportion to expiratory flow (expiratory assistance, EA). Ventilatory responses were measured during 4 min of EA (-9.7 cm H20/L/s) and were compared with those during control periods (4 min each) before and after this (Ct and C2). Sense of breathing effort was assessed at 1-min intervals by asking the subject to point to a category scale of 1 to 5, with 1 being minimal effort and 5 indicating that breathing was very difficult. There were small but significant (p < 0.05) decreases in Ti (mean ± SE, -0.2 ± 0.05 s) and TE (-0.3 ± 0.07 s), with increases in breathing frequency (+2.25 ± 0.7) and ventilation (+1.5 ± 0.6 L/min). No significant changes were observed in tidal volume or end-expiratory volume. The EA caused a highly significant ( p < 0.001) increase in the sense of breathing effort. We conclude that dynamic compression of the airways caused a mild tachypnea and resulted in an unpleasant respiratory sensation. Such findings lend support to the hypothesis that upper airway mechanoreceptors actively modulate ventilatory control and may contribute to the sensation of dyspnea in patients with COPD. AM REV RESPIR DIS 1987; 135:912-918

Comportamento da hiperinsuflação dinâmica em teste em esteira rolante em pacientes com DPOC moderada a grave

“…(2,(6)(7)(8)(9)(10) Dyspnea can also be induced by EFL per se, probably through reflexes originating from the dynamic compression of the intrathoracic airways. (27) The findings of the present study corroborate the concept that DH plays an important role as an etiological factor for exercise limitation in patients with moderate to severe COPD. Therefore, two thirds of the patients evaluated in the present study were unequivocally DH+ (Table 2), and the extent of that phenomenon correlated with exercise intolerance and the consequent dyspnea (Figure 1).…”

Physiological techniques for detecting expiratory flow limitation during tidal breathing

“…The finding of O'DONNELL et al [49] that application of -9.7 cmH 2 O?L -1 ?s -1 of expiratory assistance for 4 min during inspiration and expiration caused unpleasant respiratory sensation can be attributed to negative pressure application differences. NEP, usually set at -5 cmH 2 O level, is applied only during expiration at five-to 10-breath intervals.…”

Effect of salbutamol on dynamic hyperinflation in chronic obstructive pulmonary disease patients

“…Dynamic hyperinflation is associated not only with increased inspiratory work due to PEEPi [7] but also with impaired inspiratory muscle function [8]. This, together with flow-limiting dynamic compression during tidal breathing, may contribute to dyspnoea in flow-limited COPD patients [9,10]. Indeed, in a study by ELTAYARA et al [9], the severity of chronic dyspnoea was found to correlate much more closely with flow limitation than with usual spirometric indices.…”