Regional ventilation distribution: effects of lateral posture and airway clearance techniques in healthy and individuals with COPD.

Lateral positioning is commonly used in respiratory physiotherapy to optimize ventilation and promote secretion clearance. However, little is known about how different airway clearance techniques (ACTs) affect regional ventilation in this posture, particularly in older adults and individuals with chronic obstructive pulmonary disease (COPD). Healthy adults and individuals with COPD underwent a 20-min session consisting of five 2-min respiratory maneuvers in the right lateral posture, each separated by 2-min rest periods. The first maneuver involved spontaneous tidal breathing, whereas the order of the remaining four was randomized and included: 1-L tidal breaths; expiration against positive expiratory pressure (PEP), slow expiration with open glottis (ELTGOL) without physiotherapy assistance (ELTGOLAuto); ELTGOL with manual physiotherapy assistance (ELTGOLPhysio). Regional ventilation distribution was assessed using electrical impedance tomography by calculating the proportion of tidal impedance variation (TIV%) in the right and left lungs, from which the difference (ΔTIV%) was derived. Thirty-two participants (16/groups, aged 69 ± 7 yr) were analyzed and averaged, as there was no significant between-group difference. During spontaneous breathing, ventilation was preferentially distributed to the right lung (ΔTIV% = 21 ± 28%). All four maneuvers significantly reduced this asymmetry (P < 0.05). ELTGOLAuto and ELTGOLPhysio elicited the largest decrease (ΔTIV%: -24.5 ± 23.8% and -23.7 ± 27.6%, respectively; P < 0.001), followed by PEP (-15.1 ± 31%, P = 0.009). The redistribution was mainly due to a relative increase in ventilation in the nondependent lung in both groups, though effects tended to be more attenuated in COPD. These findings contribute to a better understanding of how common physiotherapeutic maneuvers influence lung ventilation patterns.NEW & NOTEWORTHY This study provides the first direct evaluation of regional ventilation distribution during airway clearance techniques (ACTs) in the lateral posture using electrical impedance tomography. We show that the intended increase in dependent-lung ventilation is not achieved; instead, ventilation shifts toward a more homogeneous right-left ventilation distribution, particularly during slow expiration with open glottis, in both healthy and chronic obstructive pulmonary disease (COPD) individuals. These findings refine the physiological understanding of ACTs and their potential optimization in clinical practice.