Abstract:
|
: Electrical impedance tomography measures changes in lung impedance, which
are mainly related to changes in lung volume. We used electrical impedance tomography to inves-
tigate the effects of high-flow nasal cannula (HFNC) and body position on global and regional
end-expiratory lung impedance variation (
EELI). METHODS: Prospective study with 20 healthy
adults. Two periods were defined: the first in supine position and the second in prone position. Each
period was divided into 3 phases. In the first and the third phases the subjects were breathing
ambient air, and in the second HFNC was implemented. Four regions of interest were defined: 2
ventral and 2 dorsal. For each respiratory cycle, global and regional
EELI were measured by
electrical impedance tomography and were expressed as a function of the tidal variation of the first
stable respiratory cycle (units). RESULTS: HFNC increased global EELI by 1.26 units (95% CI
1.20–1.31,
P
<
.001) in supine position, and by 0.87 units (95% CI 0.82–0.91,
P
<
.001) in prone
position. The distribution of
EELI was homogeneous in prone position, with no difference between
ventral and dorsal lung regions (
0.01 units, 95% CI
0.01 to 0,
P
.18), while in supine position
a significant difference was found (0.22 units, 95% CI 0.21–0.23,
P
<
.001) with increased EELI in
ventral areas. CONCLUSIONS: HFNC increased global EELI in our population, regardless of body
position, suggesting an increase in functional residual capacity. Prone positioning was related to a
more homogeneous distribution of
EELI, while in supine position
EELI was higher in the
ventral lung regions. |