Background: Previous studies have shown that relaxation
biofeedback reduced time on the ventilator for the difficult-to-wean
Objective: To test the hypothesis that the
underlying mechanism of biofeedback ventilator weaning was the
reduction of neural respiratory drive (NRD).
Prospective, linear regression analysis.
Critical care medicine department in tertiary health care
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 (V̇i), 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 V̇i = −4.65 ± 1.17
L/min, DA EMG = −0.4 ± 0.21 μV,
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.
BK = background; DA = diaphragm; EMG = electromyogram;
ETCO2 = end-tidal CO2; FB = feedback;
HR = heart rate; NRD = neural respiratory drive;
P100 = occlusion pressure 0.1 sec from onset of
inspiration; RR = respiration rate; SOB = shortness of breath;
T = threshold line; V̇i = inspired minute
ventilation; Vt/Ti = mean
inspiration flow; Vt = tidal volume; μV = microvolt