Prestretched airway smooth muscle response to length oscillation

Airway smooth muscle ( ASM ) hyperconstriction is the cause of many respiratory diseases including asthma. In vitro testing has demonstrated that the active forces of ASM are reduced by length oscillation ( LO ) mimicking tidal breathing. In a previous study, we demonstrated that this force reduction can be further enhanced when superimposing oscillations (with certain frequencies and amplitudes) on this LO . In contrast, it has been reported that pressurizing the lung may help in relieving asthmatic airway constrictions. Ultimately, this pressurizing stretches the ASM and may disturb the acto‐myosin cross‐bridges in a manner similar to LO ; however, it is of a static rather than dynamic nature. This research investigates the effect of combining both prestretch‐ and LO ‐applications on contracted porcine ASM . Isolated porcine ASM relaxation was tested with a 0.56%, 2%, or 4% stretch of its reference length ( L ref ) in addition to LO . These oscillations are composed of a main wave mimicking the normal breathing (frequency of 0.33 Hz and amplitude of 4% L ref ) and superimposed oscillations (frequencies of 20, 30, 40, 60 and 80 Hz and amplitude of 1% L ref ). The oscillations were maintained for 10 min. The results demonstrate that a prestretch of 0.56% and 2% L ref does enhance the contracted ASM relaxation at certain superimposed length oscillations frequencies while of 4% L ref does not.