An optimally controlled respirator was developed so as to maintain arterial
PCO2 constant. It has three main features : 1) ventilation is controlled by the patient's metabolic rate from continuously measured CO
2 output, 2) physiologic dead space approximated as a linear function of tidal volume is used to estimate alveolar ventilation, and 3) respiratory rate is computed to minimize ventilatory work.
The control system of the respirator was designed, subject to the analytical results of the ventilatory response of the man-respirator system obtained with a digital computer.
Anesthetized dogs were ventilated by the respirator for periods exceeding 24 hours. Arterial
PCO2 and
PO
2, were maintained within permissible ranges.
The respirator was applied to dogs when the metabolic rate was changed by intravenous CO
2 loading. Arterial
PCO2 returned to the original level within 10 minutes after the CO
2 loading began. Following initial CO
2 loading, the arterial
PCO2 was observed to exceed the normal range for about three minutes. After the CO
2 loading stopped, arterial
PCO2 decreased slightly and then increased to the same level as before CO
2 loading.
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