Significance of Loop Formation in Pressure/Flow Diagrams of Chronic Obstructive Lung Diseases

Abstract

This paper tries to examine pathophysiologic factors causing loop formations in pressure/flow diagrams recorded by a body plethysmograph. An account is given of pressure/flow traces in a survey of 564 patients suffering from chronic obstructive lung diseases. 34 % of the patients have shown a looped appearance in the traces. It can be demonstrated that the compressibility of gas not taking part in ventilation will cause phase shift in pressure/flow diagrams in cases of some defined factors like increased breathing rate, enlarged intrathoracic gas volume, increased airway resistance and high absolute pressure at resting mid-position in non-ventilated gas spaces. In case of elliptic loop formation in pressure/flow patterns, work (blind work) caused by compression and decompression of non-ventilated gas volumes can be determined from corresponding pressure/volume diagrams. The conclusion emphasizes that blind work can dramatically influence dynamics of breathing in advanced chronic obstructive lung diseases.

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

“…Earlier studies attributed the appearance of expiratory looping to abnormal compression and collapse of the airways during expiration (2) or to compression of nonventilated air spaces (16). On the other hand, airway compression does not necessarily lead to airway collapse.…”

Plethysmographic Loops: A Window on the Lung Pathophysiology of COPD Patients

“…Previous investigations were focused on the qualitative study of the shape and magnitude of the P alv – loop in relation to the underlying respiratory disease ( Islam and Ulmer, 1971 ; Matthys, 1972 ), and only airway resistance ( Kostianev and Ivanova, 1993 ), or the phase shift between P alv and ( Huckauf and Hüttemann, 1972 ) were numerically characterized. Notably, some of these studies were performed during rebreathing of gas mixtures in BTPS conditions, a dismissed procedure in clinical practice.…”