Reduction in ventilator response to CO2 with relaxation feedback during CO2 rebreathing in normal adults.

BACKGROUND

Previous studies have shown that relaxation biofeedback reduced time on the ventilator for the difficult-to-wean patients.

OBJECTIVE

To test the hypothesis that the underlying mechanism of biofeedback ventilator weaning was the reduction of neural respiratory drive (NRD).

DESIGN

Prospective, linear regression analysis.

SETTING

Critical care medicine department in tertiary health care hospital.

SUBJECTS

Fifteen healthy adult volunteers were randomly assigned to the biofeedback group, and 15 healthy adult volunteers were randomly assigned to a control group.

INTERVENTIONS

Relaxation feedback was administered while a single variable, PaCO2, was inputted to the respiratory control system and the output measured. While rebreathing 7% CO2/93% O2, the biofeedback group received a baseline session and a relaxation feedback session and the control group received a baseline session and a no feedback session.

MEASUREMENTS AND RESULTS

During relaxation feedback, there was a significant (p < 0.001 to p < 0.05) reduction in the slope of minute ventilation (VI), mean inspiratory flow (VT/TI), occlusion pressure in 0.1 s from onset of inspiration (P100), respiration rate (RR), and diaphragm (DA) EMG compared to baseline. We also found the above breathing parameters decreased significantly for relaxation feedback (p < 0.001-0.05), compared to baseline, at maximum end-tidal CO2 (64 +/- 1.2 mm Hg) (all data are expressed as mean +/- SE). The decrease for VI = -4.65 +/- 1.17 L/min, DA EMG = -0.4 +/- 0.21 microV, P100 = -1.13 +/- 0.56 cm H2O, VT/ TI = -144 +/- 82.91 ml/s, and RR = -3.1 +/- 0.79 breaths/min. No significant changes occurred in these parameters for the control group.

CONCLUSIONS

We conclude that the addition of the behavioral input of relaxation feedback results in decreasing the values of respiratory parameters that reflect NRD.