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Respir Care. 2013 Apr;58(4):589-96. doi: 10.4187/respcare.02086.

Effect of high-flow nasal cannula and body position on end-expiratory lung volume: a cohort study using electrical impedance tomography.

Author information

1
Critical Care Department, Vall d'Hebron Research Institut, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain. jorriera@vhebron.net

Abstract

BACKGROUND:

Electrical impedance tomography measures changes in lung impedance, which are mainly related to changes in lung volume. We used electrical impedance tomography to investigate the effects of high-flow nasal cannula (HFNC) and body position on global and regional end-expiratory lung impedance variation (ΔEELI).

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 ΔEELI 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 ΔEELI 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 ΔEELI, while in supine position ΔEELI was higher in the ventral lung regions.

KEYWORDS:

body position; electrical impedance tomography; high-flow nasal cannula; lung volume; oxygen therapy; prone position

PMID:
23050520
DOI:
10.4187/respcare.02086
[Indexed for MEDLINE]
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