Medical Chest Wall Compliance: Effects on Lung Volumes?

[nokia8650]

I was wondering what the changes would be if the a) the lung compliance decreased and b) the chest wall compliance decreased. Am i correct in thinking both would result in a fall in FRC, or would that only be for a fall in lung compliance? In addition, what would happen to other lung volumes?

Many Thanks

 

[SW VandeCarr]

The usual term is "Forced Vital Capacity" (FVC) which refers to the total lung capacity less residual volume (RV). I'm not sure exactly what you mean by FRC in this context.

In restrictive lung disease of any kind, tidal volume is not affected unless the condition is very severe. All other lung function parameters are likely to be reduced to varying degrees depending on disease severity. The most sensitive would be FVC and, I believe, FEV2 or FEV3. One might generate normal peak flow (PF) in less severe restrictive conditions.

EDIT: Peak flow, and other parameters, are likely to be more sensitive to chest wall restriction than lung compliance depending on the particular condition. For example, a broken rib could influence all parameters possibly including tidal volume. It's more reasonable to talk about how decreased lung compliance, or any particular restrictive condition, affects lung function.

Functional Residual Capacity (FRC) is a parameter of obstructive lung disease and is defined as expiratory reserve capacity (ERC or ERV) plus residual volume. In obstructive disease, the volumes are often normal to increased (ERV) and lung compliance may paradoxically increase.