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Clinical Investigations: CONTROL OF BREATHING |

Reduction in Ventilator Response to CO2 With Relaxation Feedback During CO2 Rebreathing in Normal Adults*

Jerome E. Holliday, PhD; Chris Veremakis, MD
Author and Funding Information

*From the Department of Critical Care Medicine, St. John’s Mercy Medical Center, St. Louis, MO.

Correspondence to: Jerome E. Holliday, PhD, VA Medical Center, Medicine Service 111-JC, 915 N Grand Blvd, St. Louis, MO 63106



Chest. 1999;115(5):1285-1292. doi:10.1378/chest.115.5.1285
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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 (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.

Abbreviations: 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

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