by Pablo V. Romero MD , PhD
Diagnosing the functional status of the lung and respiratory system generally requires several tests that measure or evaluate different aspects of respiratory system function. The ensemble of parameters provided by respiratory function tests composes a matrix of data. These data have their own meaning (usually in relation to predicted values) but also a meaning derived from internal relationships in the context of our pathophysiological knowledge, in opposition to numeric (or calculation) dependence. Therefore, functional changes in disease hardly ever affect a single parameter but, on the contrary, the whole functional situation is depicted by a more or less characteristic distortion of the functional matrix. The more complete the functional study, the more precise the functional diagnosis. Each parameter is, therefore, a piece in a complex puzzle with no predicted pattern, but one that we compose in order to make the pieces fit into a functional picture.
To interpret the function status of lung and respiratory system in disease, several aspects of pulmonary function can be studied, depending on the aim of the study. The most relevant being
- Ventilatory dysfunction
- Distribution or (V/Q) troubles
- Respiratory exchange impairment
- Pulmonary hemodynamics
- Response to exercise
- Bronchial Hyperresponsiveness
which are usually complemented by other measurements that increase the precision of diagnosis. As diseases are classified in terms of clinical, pathological or morphological findings, these functional troubles generate patterns of dysfunction that are almost never characteristic or specific of a particular disease, but compose the FUNCTIONAL DIAGNOSIS by themselves.
In successive articles we will develop these and other ideas relative to functional diagnosis and how the normality or abnormality of a given parameter does not depend solely on its value relative to the predicted range, but also to the changes observed in other parameters by a process that we call pathophysiological coherence.