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Maximal methacholine-induced constriction in rabbit lung: interactions between airways and tissue?
1Meakins-Christie Laboratories, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|March 1, 1991
Summary
Tissue viscance (Vti) significantly impacts total lung resistance (RL) in rabbits, especially during methacholine-induced airway constriction. This suggests lung tissue mechanics play a crucial role in limiting airway narrowing.
Area of Science:
- Respiratory Physiology
- Pulmonary Mechanics
Background:
- Methacholine challenges are used to assess airway hyperresponsiveness.
- Lung resistance comprises airway resistance and tissue resistance.
Purpose of the Study:
- To investigate the contribution of tissue viscance (Vti) to total lung resistance (RL) during methacholine-induced bronchoconstriction.
- To explore the relationship between airway resistance (Raw) and Vti in a rabbit model.
Main Methods:
- Open-chest rabbits were mechanically ventilated and challenged with increasing concentrations of methacholine.
- Tracheal and alveolar pressures, and flow were measured to calculate RL, Vti, and lung elastance.
- Airway resistance (Raw) was derived by subtracting Vti from RL.
Main Results:
- Tissue viscance (Vti) constituted the majority of total lung resistance (RL) both before and after methacholine exposure.
- A significant negative correlation was observed between changes in Raw and Vti during plateau response.
- Vti was positively correlated with lung elastance.
Conclusions:
- Lung tissue mechanics, specifically tissue viscance, are a major determinant of total lung resistance, even during significant airway constriction.
- The findings support a model of lung interdependence, where parenchymal constriction limits airway narrowing.