Tidal expiratory flow limitation induces expiratory looping of the alveolar pressure-flow relation in COPD patients

Abstract

<jats:p> In stable chronic obstructive pulmonary disease (COPD) patients spontaneously breathing at rest, tidal expiratory flow limitation is the major determinant of the occurrence of expiratory looping in the plethysmographic flow-alveolar pressure diagram. In these patients the magnitude and the characteristics of the loop can be used as predictors of the presence of tidal expiratory flow limitation. </jats:p>

Diagnostic Insights from Plethysmographic Alveolar Pressure Assessed during Spontaneous Breathing in COPD Patients

“…Interestingly, induction of bronchoconstriction in asthmatic patients resulted in small changes in the shape and extension of the expiratory loops. These data are compatible with the notion that tEFL is the major determinant of the expansion of the expiratory P alv - loop as previously suggested [ 21 , 31 ], and it is tempting to speculate that the “openers” and “non-openers” of Topalovic et al were patients with or without tEFL. In addition, the limited changes of the expiratory loops in asthmatics after methacholine are in line with this concept: indeed, most of stable asthmatic patients are not flow-limited, and only in a minority of them tEFL appears when methacholine is administered [ 35 ].…”

“…The role of tEFL in the genesis of P alv - loops was specifically investigated in 60 stable COPD patients, stratified according to the absence or presence of tEFL assessed with the negative expiratory pressure (NEP) technique [ 30 ], and studied before and after bronchodilation (BD) [ 31 ]. Before BD, A exp was markedly larger (360%) in patients with tEFL relative to those without tEFL.…”

“…It should be underlined that the study by Pecchiari et al [ 31 ] was not a validation study and was not powered to detect small differences in the predictive ability of the various parameters, especially when this was rather high. Nevertheless, the plethysmographic method for tEFL detection appears a novel and non-invasive tool to characterize the mechanical abnormalities of COPD patients, which does not require additional dedicated devices.…”

“…On the other hand, the FOT method infers the presence of tEFL from a within-breath difference between inspiratory and expiratory reactance [ 56 ]. Despite the potential lack of specificity which may arise from the indirectness of these measurements, both the plethysmographic and the FOT methods have shown an acceptable degree of agreement with the NEP technique for the purpose of tEFL detection [ 31 , 57 ].…”

Factors influencing self-selected walking speed in fibrotic interstitial lung disease

“…This finding is similar to the results of results of a recent study on patients with COPD 10 . The increased cost of breathing observed in respiratory diseases seems to not be enough to impact the overall metabolic cost of walking 35 . These results support previous findings showing that the walking economy behavior in ILD resembles that observed in obstructive pulmonary disorders 10 .…”