Reduction in ventilatory response to CO2 with relaxation feedback during CO2 rebreathing for ventilator patients.
BACKGROUND
Previous studies have shown that relaxation biofeedback reduced the amount of time spent receiving ventilation for difficult-to-wean patients.


OBJECTIVE
The present study was begun to test the hypothesis that the underlying mechanism of biofeedback ventilator weaning was the reduction of neural respiratory drive (NRD).


METHODS
Prospective.


METHODS
Pulmonary Medicine division in a Veterans Affairs hospital and the St. Louis Regional Medical Center.


METHODS
Twenty-four patients who were receiving mechanical ventilation were randomly assigned to either the biofeedback group or the control group.


METHODS
Respiratory relaxation feedback (RFB) was administered while a single variable, PaCO(2), was input to the respiratory control system and the output was measured. While rebreathing 7% CO(2)/93% O(2), the biofeedback group received a CO(2) trial session and a CO(2) RFB session, and the control group received a CO(2) trial session and a CO(2) no-feedback (NFB) session.


RESULTS
There was a significant (p < 0.05) reduction in respiratory and EEG parameters for the RFB group at maximal end-tidal CO(2) (mean [+/- SE], 70 +/- 0.2 mm Hg) between the CO(2) trial and the CO(2) RFB session compared to the control group where there was no significant difference between the results of the CO(2) trial and the CO(2) NFB session. The mean values for the CO(2) trial and CO(2) RFB session for the biofeedback group were as follows: occlusion pressure 0.1 s from the onset of inspiration, 8.42 +/- 1.08 and 6.48 +/- 0.78 cm H(2)O (which reflects NRD), respectively; minute inspiratory ventilation, 15.84 +/- 0.81 and 13.91 +/- 0.72 L/min, respectively; mean inspiratory flow, 670 +/- 2.28 and 581 +/- 35 mL/s, respectively; respiration rate, 32 +/- 2.28 and 31.2 +/- 2.58 breaths/min, respectively; and chest background electromyography, 4.89 +/- 0.71 and 3.54 +/- 0.54 microV, respectively. The mean electroencephalograph outputs for the CO(2) trial and CO(2) RFB session for the biofeedback group were as follows: mean EEG frequency, 14.78 +/- 0.98 and 13.06 +/- 0.59 Hz, respectively; and beta EEG power, 3.1 +/- 0.03 and 2.39 +/- 0.19, microV(2), respectively; and gamma EEG power, 2.96 +/- 0.34 and 2.24 +/- 0.24 microV(2), respectively.


CONCLUSIONS
We conclude that the decrease in respiratory parameters reflecting NRD induced by RFB represents a key mechanism for the previously demonstrated effectiveness of biofeedback in reducing weaning time from mechanical ventilation.
Holliday
Jerome E
JE
Medical Services, Veterans Affairs Medical Center, St. Louis MO 63106, USA. HoillidayJEH@msn.com
Lippmann
Michael
M
D002245:Carbon Dioxide / Q000008:administration & dosage*; D004569:Electroencephalography; D025461:Feedback, Physiological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000187:drug effects*; D012119:Respiration; D012121:Respiration, Artificial
D002245:Carbon Dioxide