抄録
The physiological significance of the chemical regulation of respiration for blood gas homeostasis is reviewed. In particular, its role in the state of impaired gas exchange is considered.
For the quantitative evaluation of the ventilatory activities of the driving system, ΔV50 and D were examined by the withdrawal test and by the CO2 response curve during hyperoxia for peripheral and central chemoreceptor activities, When ΔV50 and D plotted against PaCO2 and PaO2 were observed at rest in 37 patients with pulmonary disease, these indices were significantly decreased in patients with PaO2 lower than 70mmHg and PaCO2 higher than 50mmHg. Depression of ventilatory response to chemical drives was more pronounced in the patients with higher PaCO2 than low PaO2.
Steady state response to hypoxia was found to be higher than ΔV50. This may be attributed to the fact that hypoxic drive via the peripheral chemoreceptors is integrated, modified or even depressed in the brain stem respiratory centers. Evidence of medullary depression during hypoxia was present in a patient with bilateral carotid chemoreceptor resection over 20 years previously.
Electro-physiological studies on the ventral surface of the medulla oblongata where the central chemosensitive areas are supposed to be located are presented. Cells with specifically H+ dependent membrane potential were detected. We at present suspect that this potential varies in accordance with extracellular K+ concentration which is released by chemoreceptive cell excitation. Unsolved problems related to central chemosensitivity mechanisms are discussed.
