Results

The system measurement of lung resistivity was found to be reproducible within 2% for healthy subjects (figure 2).


Figure 2 – an example for measurement reproducibility. Measurements 1, 2 and 3 were conducted in an interval of about 1 month from each other. Each one consisted of 5 successive measurements. The percentages indicate the standard deviation of the lung resistivity within each measurement.


The system's estimations for lung resistivity were proven to be not correlated to various anthropometric parameters (age, height, weight, BMI and BSA) for a group of N=33 healthy subjects (table 1).

In a preliminary clinical study, 33 healthy volunteers and 34 CHF patients were measured with the system during tidal respiration, and the ability to monitor the respective lung resistivity values was assessed. A significant (p<2•10-7) separation between the two groups with respect to reconstructed lung resistivity values was found (figure 3).


Figure 3 - A scatter plot of right vs. left-lung resistivity reconstruction values for control (diamonds) and CHF (squares) groups.


In addition, a long-term monitoring of a patient during diuretics treatment was also shown (figure 4).

Figure 4 – Monitoring CHF patient during diuretics treatment. Left (circles) and right (triangles) lung resistivity reconstructions as a function of measurement number


Short-term monitoring of diuretics induced patients was performed in a clinical study for a group of N=9 CHF patients. The results show a consistent increase in lung resistivity following treatment, indicating a smaller amount of lung fluids (figure 5).

Figure 5 – Left (upper), right (middle) and average (lower) lung resistivity measurements before (blue) and following (red) diuretics treatment.