Influence of posture, sex, and age on breathing pattern and chest wall motion in healthy subjects

•Aging reduces rib cage contribution and increase abdominal contribution.•Aging increases end-inspiratory and end-expiratory chest wall volumes.•Sitting position might benefit patients who present reduced tidal volume.•Posture influences all variables of breathing pattern and chest wall motion, except respiratory rate and duty cycle.•Women present higher thoracic contribution to the tidal volume. We evaluated the effects of posture, sex, and age on breathing pattern and chest wall motion during quiet breathing in healthy participants. Eighty-three participants aged 42.72 (SD=21.74) years presenting normal pulmonary function were evaluated by optoelectronic plethysmography in the seated, inclined (with 45° of trunk inclination), and supine positions. This method allowed to assess the chest wall in a three dimensional way considering the chest wall as three compartments: pulmonary rib cage, abdominal rib cage and abdomen. Posture influenced all variables of breathing pattern and chest wall motion, except respiratory rate and duty cycle. Chest wall tidal volume and minute ventilation were reduced (p