A nonlinear mathematical model of the CO2 control system was used to examine a number of issues concerning the regulation of PaCO2 during rest and exercise. To gain insight to the regulatory properties of the respiratory system, the open loop gain (GL) and closed loop sensitivities SI = delta PaCO2/delta PICO2 and SV = delta PaCO2/delta VCO2 were calculated. GL indicates the ability of a control system to regulate the controlled variable, PaCO2 in the model. SI and SV represent the change in PaCO2 to unit changes in PICO2 and VCO2, respectively. Model predications were obtained for rest and various intensities of exercise for the following challenges to the respiratory system: (a) CO2 inhalation, (b) i.v. CO2 loading, (c) application of an external dead space, and (d) a shift in the resting operating point. Increasing exercise intensity produced a substantial decrease in GL and increase in SI consistent with the hypothesis that exercise degrades the ability of the respiratory system to regulate PaCO2. However, SV decreased indicating that the respiratory system would actually be better able to regulate PaCO2 if there were fluctuations in VCO2. Thus, GL does not completely describe the regulatory characteristics of the respiratory control system. It is demonstrated that the regulatory characteristics of the respiratory system as described by GL, SI, and SV are complex and depend on the nature of the challenge. Techniques for systematically describing the regulatory properties of the CO2 control system are described.

Carbon Dioxide↗

PubMedDate not supplied

The quota system in burn rehabilitation.

This article describes the quota system as a treatment for the helplessness behaviors and depressive symptoms that develop in some patients with burn injuries. With an A-B single-case design, the quota system was implemented for a patient who had sustained a particularly severe burn injury. A series of baseline behaviors were measured for 3 days, and then 80% of the patient's average performance on each of the targeted behaviors was computed and used as the initial quota value. The behavioral quotas were increased systematically and gradually by approximately 5% to 10% every day. The results suggest that the quota system may have been effective in decreasing an overall trend toward passivity, in increasing 3 of 4 targeted rehabilitation behaviors, and in reducing depressive symptoms in a patient with a particularly devastating injury.

Adult↗

PubMedDate not supplied

Behavioral systems analyzed.

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Adolescent↗