Respiratory control in presenile dementia

To evaluate the role of the cerebral cortex in the response to externally added inspiratory flow-resistive load, we studied 7 patients manifesting clinical presenile dementia of the Alzheimer's type. All subjects exhibited diffuse cerebral cortical atrophy on computerized tomography of the brain. The mean age of the group was 45.6 yr. The rebreathing technique was used to assess minute ventilation (VE) and occlusion pressure (P100) responses to progressive hypercapnia. Rebreathing runs were performed before and during the addition of an inspiratory flow-resistive load of 18 cm H2O.L-1.s. The respiratory control data of these patients were compared with data obtained by similar techniques in a matched normal volunteer control group. In the patient group, with the addition of load, the VE/PCO2 response slope decreased (p less than 0.005), whereas the P100/PCO2 response slope did not significantly change. In the control group, P100/PCO2 response slope increased with load to maintain ventilation. These results suggest that in presenile dementia, during added inspiratory load, the drop in VE is associated with an inadequate increase in respiratory neuromuscular output. This lack of load compensation in patients with presenile dementia suggests a role for the cerebral cortex in the response to externally added load.