Interaction between left and right intercostal muscles in airway pressure generation

The interactions between the different rib cage inspiratory muscles in the generation of pleural pressure remain largely unknown. In the present study , we have assessed in dogs the interactions between the parasternal interco stals and the interosseous intercostals situated on the right and left side s of the sternum. For each set of muscles, the changes in airway opening pr essure (Delta Pao) obtained during separate right and left activation were added, and the calculated values (predicted Delta Pao) were then compared w ith the Delta Pao values obtained during symmetric, bilateral activation (m easured Delta Pao). When the parasternal intercostals in one or two intersp aces were activated, the measured Delta Pao was commonly greater than the p redicted value. The difference, however, was only 10%. When the interosseou s intercostals were activated, the measured Delta Pao was nearly equal to t he predicted value. These observations strengthen our previous conclusion t hat the pressure changes produced by the rib cage inspiratory muscles are e ssentially additive. As a corollary, the rib cage can be considered as a li near elastic structure over a wide range of distortion.