[Electrical impedance tomography: standardizing the procedure in pneumology]. / Tomografía por impedancia eléctrica. Estandarización del procedimiento para su aplicación en neumología.

The following conditions are optimal for obtaining an adequate number of informative images by electric impedance tomography: a) patient seated or standing with hands at the nape of the neck; b) breathing at rest; c) recording of at least 300 images (at a frequency of 10 Hz), and d) readings taken at the sixth intercostal space.

Assessment of the unilateral pulmonary function by means of electrical impedance tomography using a reduced electrode set.

The usefulness of electrical impedance tomography (EIT) to assess ventilation-related phenomena in the thorax has already been demonstrated, especially in controlled environments. We focus on our developments in the assessment of the unilateral pulmonary function (UPF) in real clinical environments. The impact of the reduction of the number of electrodes used is analysed theoretically and experimentally with different approaches. Sixteen-electrode EIT measurements were performed on a group of lung cancer patients (19 M, 2 F, ages 25-77 years). Results are compared with those obtained from ventilation scintigraphy. Eight-electrode measurements were synthesized from the 16-electrode ones. The Bland and Altman analysis indicates an agreement of about +/- 1 percent points in the estimation of UPF. On five of these patients real 8-electrode measurements were performed, obtaining differences from 0.2 percent to 6 percent points. It is concluded that reducing the number of electrodes does not adversely affect the assessment of UPF, but there is a reproducibility issue affecting all the techniques which needs further study.

Use of electrical impedance tomography (EIT) for the assessment of unilateral pulmonary function.

We describe a fully automatable quantification process for the assessment of unilateral pulmonary function (UPF) by means of EIT and propose a measurement protocol for its clinical implementation. Measurements were performed at the fourth and sixth intercostal levels on a first group of ten healthy subjects (5M, 5F, ages 26-48 years) to define the proper protocol by evaluating the most common postures and ventilation modes. Several off-line processing tools were also evaluated, including the use of digital filters to extract the respiratory components from EIT time series. Comparative measures were then carried out on a second group consisting of five preoperatory patients with lung cancer (4M, IF, ages 25-77 years) scheduled for radionuclide scanning. Results show that measurements were best performed with the subject sitting down, holding his arms up and breathing spontaneously. As regards data processing, it is best to extract Fourier respiratory components. The mean of the healthy subject group leads to a left-right division of lung ventilation consistent with literature values (47% left lung, 53% right lung). The comparative study indicates a good correlation (r = 0.96) between the two techniques, with a mean difference of (-0.4+/-5.4)%, suggesting that the elimination of cardiac components from the thoracic transimpedance signal leads to a better estimation of UPF.