LUNG VENTILATION TELEMETRY USING A BIOIMPEDANCE METHOD

V. M Bolshov, V. I. Lebedev*, and. N. N. Tratkevich**
"Medas" Medical-Engineering Center (Moscow, Russia);
*Biotelemetry Laboratory (Kislovodsk, Russia);
**"Pulsar" Medical-Engineering Center (Saint Petersburg , Russia)

METHOD. Lung ventilation parameters are usually measured by pneumotachometry or spirometry. However, these methods are not suitable for those situations when the patients under examination are in the state of long-time motor activity. Much has been done to solve this problem through an electrical impedance pneumography method, without any noticeable success, though.

The paper puts forward a pneumographic method which uses sets of electric lung impedance measurement and anthropometric data to establish a correct relation between these data and ventilation parameters. A telemetric system has been developed based on this approach.

The patient-borne compact unit converts the thorax impedance parameter between the measuring electrodes to an electric signal which is transmitted to a receiver by means of a frequency-pulse modulation technique.

At the receiver output the signal is processed by a computer which solves the following multiple regression equation:

                    V = D Z(23.176 - 0.103P - 0.059M + 0.053B), where

V is the lung ventilation volume (l);
D Z is the pneumographic curve impedance swing (Ohm);
P is the height of the patient (cm);
M is the weight of the patient;
B is the age of the patient (years).

RESULTS. The studies were made on three groups of patients, a total of 56 persons (32 male and 24 female). The first group consisted of healthy people (30 persons), the second had obstructive lung ventilation disturbances, and the third one were patients with restrictive or combination impairments.

The mean error in lung ventilation examinations in all the groups did not exceed 5.7% to suggest the validity of the principle thus established, as expressed by the above equation.

DISCUSSION. If some restrictions are imposed on the patients' motor activity, the method described above ensures lung ventilation parameters measurement to an accuracy suitable for the clinical practice.