Abstract
Objective: Our hypothesis is that the afferent information from lung receptors takes part in the control mechanism of ventilation and compensatory capacity of the respiratory system at obstructive lung disease with central hypervolemia.
Methods: Head-down tilt (HDT) that increase central venous pressure due to fluid shifts within the entire body was used as model for simulating central hypervolemia. The experiments were performed in vagaly intact or vagotomized, anesthetized rats. Tidal volume (VT), breathing frequency (f), minute lung ventilation (VE), esophageal pressure (Pes), inspiratory occlusion pressure (P0.1), functional residual capacity (FRC), lung compliance (C), central venous pressure (CVP) were examined at supine (baseline) and after 30 min HDT.
Results: HDT increase of CVP, decrease of FRC and C. There were significant decreases in VT by 18%, VE by 14% after 30 min exposure in HDT relative to supine. Increases resistive and elastic component of respiratory resistance were found. On the other hand rising Pes by 116% wasseen which reflects an increase in inspiratory muscle output occurs when respiratory load increases. After bilateral vagotomy Pes rose only to 65% in comparison to vagal intact animals. Inspiratory occlusion pressure evoked increase P0.1 in both supine and HDT. In supine this value rose to 536% (P<0.01), whereas in HDT by 320% (P<0.05).
Conclusions: One of the possible mechanism of compensatory response respiratory system is the vagal afferent, presumably originating from slowly adapting lung stretch receptors due to decreased lung volume.
- © 2014 ERS