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Cerebral blood flow and cerebral oxygen consumption in patients with COPD on mechanical ventilation
Objective:
To investigate the effect of PaCO2 on cerebral blood flow (CBF) in chronic obstructive pulmonary disease (COPD).
Design:
Before-after trial.
Setting:
General ICU in a regional hospital.
Patients:
7 patients undergoing mechanical ventilation because of an exacerbation of COPD.
Intervention:
CBF and cerebral metabolic rate of oxygen (CMRO2) of COPD were measured before and after hyperventilation and were compared by those of normal patients. CBF was measured by the Kety-Schmidt technique using 15% N2O.
Measurements/Results:
Hyperventilation produced a significant reduction in CBF in COPD with no concomitant change in CMRO2. CMRO2 in COPD was significantly lower than those in normal patients. The regression equation was shifted significantly more to the right in COPD.
Conclusion:
The sensitivity of CBF in CO2 remained but CMRO2 was reduced markedly in COPD patients.