Ventilometry: a new assessment of respiratory function based on tidal breathing

We present a new method to characterize the morphology of tidal breathing airflow profiles, aiming at characterizing the way the tidal volume is manipulated as the result of global ventilation mechanics. We use the term “Ventilometry” in order distinguish it from standard “Spirometry”. Attempts to define quantitatively morphological markers of airflow profile failed so far, for lack of fundamental adequate tools to access this information. We exploit a new disruptive fundamental theory of the anharmonicity of periodic signals. A record of tidal breathing cycles is segmented into individual cycles. The morphology of each cycle is defined accurately by 9 parameters: Amplitude, Asymmetry, Anharmonicity and Position for inspiration and expiration and global “orientation”. We define the “Personal Respiratory Profile” (PRP) as a morphological average of these parameters along with cycle-to-cycle variability. We have measured the PRP of 33 healthy people. We confirm the stability of the profile of a given person. The “orientation” parameter is related to the passive character of expiration. Through clustering in the multi-dimensional space of morphological markers we identify several typical morphologies, thus providing a way to define a “breathing personality”, but also a way to characterize abnormal morphologies. The 33 individuals were distributed in 5 clusters. This new “test” is soft and requires very little cooperation from the patient allowing home use. Ventilometry has been successfully used to characterise the bronchodilato response of COPD patients, in telemonitoring of severe asthmatics and lung transplants. The results of these studies will be soon published.