Am. J. Respir. Crit. Care Med., Vol 155, No. 5, 05 1997, 1552-1559.
Effect of chest wall vibration on dyspnea during hypercapnia and exercise in chronic obstructive pulmonary disease
LM Cristiano and RM Schwartzstein
The Charles A. Dana Research Institute and Harvard-Thorndike Laboratory of Beth Israel Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Vibration of chest wall inspiratory muscles during inspiration (in- phase)
reduces breathlessness associated with hypercapnia and resistive loading in
normal subjects and in patients with chronic obstructive pulmonary disease
(COPD) at rest. To evaluate further the effect of chest wall vibration on
breathlessness ("breathing discomfort") in patients, we studied 10 subjects
52 to 79 yr of age with severe dyspnea (mean FEV1, 0.75 L, 27% predicted).
On a single day, we used two separate stimuli to produce mild to moderate
breathlessness (BR): Protocol 1, steady-state hypercapnia; Protocol 2,
exercise with a lower extremity ergometer. During each protocol, we applied
in-phase chest wall vibration (CW) randomly alternating with one of two
controls: deltoid vibration (DV) or no vibration (NV). During hypercapnia,
CW significantly reduced BR (DV, 2.9 +/- 2.1; CW, 2.3 +/- 1.4; p < 0.05;
NV, 3.3 +/- 2.1; CW, 2.6 +/- 2.0; p < 0.01) without significant changes
in ventilation. During exercise, CW did not significantly alter BR relative
to controls. These findings may be explained by the effect of vibration on
the sense of respiratory effort and/or by improvement of the match between
efferent motor commands and afferent information from the respiratory
system. The lack of effect during exercise on BR suggests there may be a
"therapeutic window" or range of conditions within which CW is effective in
reducing dyspnea in patients with COPD.
