Am. J. Respir. Crit. Care Med.,
Volume 157, Number 2, February 1998, 415-420
Self-Control and External Control of Mechanical
Ventilation Give Equal Air Hunger Relief
ELISABETH
BLOCH-SALISBURY,
CHRISTINA M.
SPENGLER,
ROBERT
BROWN,
and
ROBERT B.
BANZETT
Physiology Program, Harvard School of Public Health; Department of Medicine, Harvard Medical School; and Pulmonary and
Critical Care Medicine Section, Brockton/West Roxbury Veterans Affairs Medical Center, Boston, Massachusetts
Elevated end-tidal partial pressure of CO2 (PETCO2) causes air hunger; this sensation becomes intense
with a relatively small rise in PETCO2 if ventilation is held constant. Spontaneously breathing subjects
increase ventilation in response to CO2, thereby greatly diminishing air hunger. In healthy subjects
and ventilator-dependent patients, experimenter-induced increases in ventilator tidal volume (VT) relieve air hunger even if PETCO2 is kept elevated. We addressed two questions: (1) Can paralyzed, ventilator-dependent patients use the sensation of air hunger to effectively control ventilator VT using
nonrespiratory motor pathways; and (2) Do subjects obtain more relief when in control of their own
ventilator? Four subjects were trained to increase ventilator VT using a mouth-operated switch. Subjects' ratings of air hunger intensity in response to elevated PETCO2 were compared during three conditions: (1) constant VT; (2) subject-controlled VT; and (3) experimenter-controlled VT. When given
control of their ventilator, all subjects increased VT in response to increased PETCO2, thereby relieving
air hunger. Air hunger relief was similar when the experimenter mimicked these VT changes. These
results suggest that: (1) ventilator-dependent patients can use sensation, conscious decisions, and
nonrespiratory motor pathways to achieve an appropriate respiratory response to increased PCO2 and
(2) control of one's own ventilation is unimportant in these circumstances. Bloch-Salisbury E, Spengler CM, Brown R, Banzett RB. Self-control and external control of mechanical ventilation
give equal air hunger relief.
