Submitted on October 19, 2006
Accepted on May 9, 2007
Raising end expiratory volume relieves air hunger in mechanically ventilated healthy adults
Andrea Vovk1* and Andrew Paul Binks2
1 Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States
2 Biological Science, University of New England, Portland, Maine, United States; , United States; Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States
* To whom correspondence should be addressed. E-mail: avovk{at}ufl.edu.
Air hunger is an unpleasant urge to breathe and a distressing respiratory symptom experienced by cardiopulmonary patients. Increasing tidal volume (VT) relieves air hunger possibly by increasing pulmonary stretch receptor (PSR) cycle amplitude. The purpose of this study was to determine whether an increase in end expiratory volume (EEV) also relieves air hunger. Six healthy volunteers (3 females; 31±4 yrs) were mechanically ventilated via a mouthpiece (12 breaths/min; constant end-tidal PCO2) at high VE (12±2 L/min, control) and low VE (6±1 L/min to generate air hunger). EEV was raised to approximately 150, 400, 725 and 1000 mL by increasing positive end expiratory pressure (PEEP) to 2, 4, 6 and 8 cmH2O respectively for 1 min during high and low VE. The protocol was repeated in the seated and supine positions to test for the effect of shifting baseline EEV. Air hunger intensity was rated at the end of each breath on a visual analogue scale (VAS). The increase in EEV was the same between body positions, however air hunger was reduced by a greater degree in the seated position (13, 30, 31 and 44% seated vs. 3, 9, 23 and 27% supine at 2, 4, 6 and 8 cmH2O of PEEP, respectively, p<0.05). Removing PEEP produced a slight increase in air hunger that was greater than pre-PEEP levels (p<0.05). Air hunger is relieved by increasing EEV and VT (presumably via an increase in mean PSR activity and cycle amplitude, respectively).
