PT  - JOURNAL ARTICLE
AU  - Spooner, Amy J
AU  - Corley, Amanda
AU  - Sharpe, Nicola A
AU  - Barnett, Adrian G
AU  - Caruana, Lawrence R
AU  - Hammond, Naomi E
AU  - Fraser, John F
TI  - Head-of-Bed Elevation Improves End-Expiratory Lung Volumes in Mechanically Ventilated Subjects: A Prospective Observational Study
AID  - 10.4187/respcare.02733
DP  - 2014 Oct 01
TA  - Respiratory Care
PG  - 1583--1589
VI  - 59
IP  - 10
4099  - http://rc.rcjournal.com/content/59/10/1583.short
4100  - http://rc.rcjournal.com/content/59/10/1583.full
AB  - BACKGROUND: Head-of-bed elevation (HOBE) has been shown to assist in reducing respiratory complications associated with mechanical ventilation; however, there is minimal research describing changes in end-expiratory lung volume. This study aims to investigate changes in end-expiratory lung volume in a supine position and 2 levels of HOBE. METHODS: Twenty postoperative cardiac surgery subjects were examined using electrical impedance tomography. End-expiratory lung impedance (EELI) was recorded as a surrogate measurement of end-expiratory lung volume in a supine position and at 20° and then 30°. RESULTS: Significant increases in end-expiratory lung volume were seen at both 20° and 30° HOBE in all lung regions, except the anterior, with the largest changes from baseline (supine) seen at 30°. From baseline to 30° HOBE, global EELI increased by 1,327 impedance units (95% CI 1,080–1,573, P < .001). EELI increased by 1,007 units (95% CI 880–1,134, P < .001) in the left lung region and by 320 impedance units (95% CI 188–451, P < .001) in the right lung. Posterior increases of 1,544 impedance units (95% CI 1,405–1,682, P < .001) were also seen. EELI decreased anteriorly, with the largest decreases occurring at 30° (−335 impedance units, 95% CI −486 to −183, P < .001). CONCLUSIONS: HOBE significantly increases global and regional end-expiratory lung volume; therefore, unless contraindicated, all mechanically ventilated patients should be positioned with HOBE.