Pv. Romero et al., Frequency characteristics of lung tissue strip during passive stretch and induced pneumoconstriction, J APP PHYSL, 91(2), 2001, pp. 882-890
To investigate the frequency-dependent changes of lung tissue mechanics dur
ing pneumoconstriction, we studied guinea pig subpleural lung strips submit
ted to a multisinusoidal deformation composed of five equal-amplitude discr
ete frequencies ranging between 0.2 and 3.1 Hz. Strips were submitted to gr
aded step stretch changes (SS) and to graded histamine stimulation (HS) in
organ bath. Elastance, resistance, and hysteresivity were calculated at eac
h frequency. The model accounting for the relationship between the complex
Young's modulus and the angular frequency showed that the constant-phase hy
pothesis was satisfied in SS condition. However, HS modified all parameters
in the model, and the constant-phase hypothesis could be rejected for HS o
f 10(-5) and 10(-3) M. The hysteresivity time course changed with angular f
requency, but differently in the HS and SS conditions. Our results agree wi
th a serial disposition of the connective matrix and contractile system in
lung tissue. We conclude that pneumoconstriction induced significant struct
ural changes at the level of the connective matrix.