<原著>慢性呼吸不全にたいする Doxapram の有効性について

Abstract

The effect of doxapram hydrochloride as the carotid body stimulant was studied in 14 respiratory failure patients (11, post-tuberculosis; 3, Chronic Obstructive Lung Disease (COLD), with the arterial partial pressure of carbon dioxide (PaCO_2) more than 50 torr; 36 studies in total). Arterial blood gas was analyzed i) while the patient was breathing room air, ii) 30 min. after the initiation of oxygen administration (24 percent oxygen by a Ventimask), and iii) after doxapram infusion for 1 hour (1-2 mg/kg/hour) with oxygen administration. The patients responded to oxygen as follows : Group I : Elevation of PaCO_2 exceeding 5 torr, 23 studies/8 patients. Group II : Change in PaCO_2 within 5 torr, 12 studies/10 patients. Group III : Decrease in PaCO_2 greater than 5 torr, 1 study/1 patient. In Group I elevation of PaCO_2 by oxygen administration was lowered by more than 4 torr by infusion of doxapram (22/23 studies). Group II was divided into two subgroups depending on the mode of response to doxapram (Group IIA and Group IIB). In Group IIA (6 studies/5 patients) PaCO_2 was lowered by more than 4 torr by doxapram and in Group IIB (6 studies/5 patients), PaCO_2 change was within 4 torr on infusion of doxapram. Considering the relative contributions of respiratory regulation and mechanical limitation of lung-thorax to hypercapnia, doxapram can be expected to show an effect only when considerable abnormalities exist in respiratory regulation. In Group I the disturbance of respiratory regulation was aggravated by loss of hypoxic drive in the carotid bodies caused by initiation of oxygen administration in the presence of carbon dioxide-insensitivity in the respiratory center. The decrease in PaCO_2 by doxapram administration in Group IIA suggested that the respiratory regulation system does not fully operate in response to mechanical limitation. In Group IIB, alveolar ventilation was maintained in proportion to mechanical limitation and was not increased by doxapram to lower