Voluntary induced alterations in regional ventilation in normal humans

We tested the hypothesis that voluntary changes of thoraco-abdominal shape can influence regional ventilation via altering regional pleural pressure swings (Ppl). Regional ventilation was measured simultaneously with regional Ppl during tidal volume breathing maneuvers in five normal subjects while they were performing one of three thoracoabdominal patterns of breathing normal, preferential intercostal (IC), or preferential diaphragmatic (DIA). In every subject, the lower lung region's ¹³³Xe washout rate was faster than the upper region's, regardless of the pattern of thoracoabdominal breathing adopted. Although IC breathing tended to make regional ventilation more homogeneous. DIA breathing tended to augment regional ventilation inhomogenities. On the average, the Ppl values were greatest in the lower lung region, regardless of the thoracoabdominal pattern adopted; however, IC breathing reduced and DIA breathing increased regional Ppl inhomogenities. When the ratios of the Ppl (lower/upper) was plotted vs. the ratios of the regional ¹³³Xe washout decay constants (lower/upper), a significant positive correlation was found. These data suggest that a causal relation between regional tidal Ppl and regional ventilation exist, thus supporting the concept that thoracoabdominal shape changes can influence regional ventilation.