Intercostal muscle oxygenation and expiratory loaded breathing at rest: Respiratory pattern effect

In patients with airway obstruction, an increase in breathing frequency at rest is commonly associated with a dynamic hyperinflation (DH). In such a situation, intercostal muscle oxygenation may be disturbed. This hypothesis was examined in a context of simulated airway obstruction in healthy subjects. After a control period of 5 min, twelve participants (20 +/- 2 years) breathed at rest through a 20-cmH(2)O expiratory threshold load, either by increasing or reducing their respiratory rate (F-ETL(+) or F-ETL(-)). Tissue saturation index (TSI) and concentration changes in oxyhaemoglobin (oxy[Hb+Mb]) were measured as well as cardiorespiratory variables. Inspiratory capacity was decreased in F-ETL(+) (p < 0.001) and correlated with dyspnea. An increase in oxy[Hb+Mb] occurred in F-ETL(+) that was higher than in F-ETL(-) (p < 0.01). TSI was not different between conditions. In healthy subjects at rest, an increase in respiratory rate during a simulated obstruction with an expiratory threshold load resulted in paradoxical response with DH emergence while intercostal muscle oxygenation was preserved.

Automated summary

In patients with airway obstruction, an increase in breathing frequency at rest is commonly associated with dynamic hyperinflation. This study simulated airway obstruction in healthy subjects and found that an increase in respiratory rate during obstruction led to a paradoxical response with dynamic hyperinflation emergence while intercostal muscle oxygenation was preserved.