Breath Stacking: Acute Effects on Cough Peak Flow and Chest Wall Volumes of Healthy Subjects

<b>Objectives:</b> The aim of this study was to investigate the acute physiological effects of the BS on CPF and chest wall volumes in healthy individuals, comparing two body positions: supine and 45° trunk inclination. <b>Methods:</b> Observational, analytical, and cross-sectional study conducted with 14 healthy individuals (7 males) who underwent the BS in two different body positions. CPF, tidal chest wall volumes and the contribution of thoracoabdominal compartments were assessed using Optoelectronic Plethysmography. Statistical analyses included two-way ANOVA and Bonferroni post hoc tests, with a significance level of 5%. <b>Results:</b> A significant increase in CPF was observed after the BS in the inclined position (<i>p</i> < 0.05), with no relevant changes in the supine position. Tidal chest wall volumes also increased in both positions, with a more pronounced effect in the 45° inclination (<i>p</i> < 0.05). The volume increase was predominantly thoracic, with a ventilatory redistribution favouring the pulmonary rib cage compartment, especially in the inclined posture. <b>Conclusions:</b> The BS produced immediate beneficial physiological effects in healthy individuals, with greater efficacy in the inclined position, enhancing expiratory flow and thoracic ventilation. These findings support the clinical applicability of BS as a physiotherapeutic strategy even in populations without respiratory dysfunction.