High Frequency Jet VentilationとMethylprednisoloneの肺水腫治療効果—Oleic Acid肺水腫犬の呼吸機能と循環動態

Synergistic effects of methylprednisolone and high frequency jet ventilation on oleic acid induced pulmonary edema

　高頻度jet換気（high frequency jet ventilation；HFJV）は，Klain^1）らによって名づけられた高頻度人工呼吸法（high frequency ventilation；HFV）の一方式である。従来の持続陽圧換気（continuous positive pres—sure ventilation；CPPV）に比べ気道内圧を低く保持しつつ，適正換気を維持できることにより循環機能の抑制やbaro-traumaを生じやすい重症呼吸不全患者に対する新しい換気の一手段となりうる呼吸法といわれている。さらにわれわれはHFVがCPPVに比し，オレイン酸肺水腫犬の呼吸管理に有効であることを報告した^2）。

　本報告は肺水腫犬を用いてHFVにメチルプレドニゾロンを併用することによりさらに呼吸機能に改善が得られるか否かを呼吸機能と循環機能の面から検討したものである。

　Pulmonary edema was produced in mongrel dogs by injecting oleic acid (0.2ml/kg) to determine synergistic effects of methylprednisolone (MP) and high-frequency jet ventilation (HFJV) on the cardiopulmonary functions and the survival rate.

　Eighteen dogs, weighing 9.1±1.8kg (mean±SD), were divided into 3 groups of 6 each. In Group I (G₁), respiration was maintained with HFJV after pulmonary edema was produced. In Groups II (G₂) and III (G₃), MP was intravenously given 1 hour after and 1 hour before the oleic acid injection, respectively, in addition to the maintenance of respiration with HFJV. Two other dogs that were left to spontaneous respiration succumbed to pulmonary edema 1 hour after the oleic acid injection. HFJV was set at 3 Hz with 0.50 of inspired oxygen fraction and the driving pressure was adjusted to keep the mean airway pressure at 5 mmHg. Measurements were made before and at 1, 3, 6, and 12 hours after the oleic acid injection.

　The survival rates at 12 hours after the oleic acid injection were 33% in G₁, 50% in G₂, and 83% in G₃, with no statistical differences among them.

　G₃ demonstrated marked improvement in Qs/Qt at 1 hours, arterial pH at 1 hours, peak airway pressure at 6 hours, PaCO₂ at 12 hours, with significant differences from G₁. Also, compared with significant hemodynamic improvement was observed in G₈ in mean pulmonary arterial pressure at 6 and 12 hours, pulmonary capillary wedge pressure at 12 hours and right ventricular stroke work index at 12 hours.

　It can be concluded from this study that MP, when prophylactically given, is effective in minimizing the noxious effects of oleic acid on the lung and the heart in experimental animals and that the therapeutic effects of MP is reduced when its administration is delayed.