酸素吸入療法の自動制御システム

抄録

To maximally avoid ventilatory depression and the iatrogenic disorders such as oxygen pneumonitis in patients with respiratory failure, an automatic control system of oxygen inhalation was developed for increasing to, and then maintaining at, predetermined levels of arterial oxygen tension (PaO₂).
Inspiratory oxygen tension (PIO₂) was changed at a ramp function (0.4% O₂/min) by the Oxygen Blender. End tidal oxygen tension (PeO₂) obtained by a mass spectrometer was utilized to estimate PaO₂ during the oxygen inhalation since the PeO₂ to PaO₂ ratio remained constant for a wide range of PIO₂.
PeO₂ was detected by two peak-hold circuits operating alternately every 10 sec. Recognition time of 15 sec was set to avoid error signals such as transient deep breath (sigh) enter into the control circuit. The interface between the patient and oxygen supply was either mouthpiece, mask or oxygen tent. In 18 patients, PaO₂ was well maintained at the preset levels within a physiological variation. Serious deteriorations in PaCO₂ and pH were not seen during inhalation except for a patient with very severe respiratory failure.
These results indicate that the automatic control system can be used in clinical practice as a safe and reliable therapeutic tool for patients with respiratory failure.