Abstract
A microcomputer feedback system has been developed which adjusts the inspired minute volume of a ventilator based on the patient's end-tidal CO2 concentration. The feedback controlled ventilator was evaluated in 6 dogs (18–20 kg). Arterial PCO2 was monitored continuously while end-tidal CO2 concentration was controlled by the microcomputer system and the following perturbations introduced: [1] NaHCO3 was infused IV, [2] a pulmonary artery was occluded, [3] one lumen of a double lumen endobronchial tube was occluded, and [4] an air embolism was given. The end-tidal PCO2 controller kept PaCO2 within 1.2 mm Hg of the desired value when CO2 production increased by as much as 44%. Changing the ventilation/perfusion ratios caused differences as large as 22 mm Hg between the arterial and end-tidal PCO2 and the controller was not effective in keeping PaCO2 at the desired level. Closed loop control of ventilation based on end-tidal PCO2 measurements successfully compensated for increases in CO2 production keeping PaCO2 constant. The controller did not, however, keep PaCO2 at the desired level when significant changes occurred in the distribution of blood flow to ventilation.
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Cadzow, J.A. and H.R. Martens.Discrete-Time and Computer Control Systems. Englewood Cliffs, New Jersey: Prentice-Hall, 1970.
Coles, J.R., W.A. Brown, and D.G. Lampard. Computer control of respiration and anesthesia.Med. Biol. Eng. 11: 262–267, 1973.
Coon, R.L., E.J. Zuperku, and J.D. Kampine. Systemic arterial blood pH servocontrol of mechanical ventilation.Anesthesiology 49: 201–204, 1978.
Frumin, M.J., N.A. Bergman, and D.A. Holaday. Carbon dioxide and oxygen levels with a carbon dioxide controlled artificial respiration.Anesthesiology 20:313–320, 1959.
Grodins, F.S. and S.M. Yamashira.Respiratory Function of the Lung and Its Control. New York, New York: Macmillan Publishing Co., 1978.
Holloman, G.H., H.T. Millhorn, and T.G. Coleman. A sampled data regulator for maintaining a constant alveolar CO2.J. Appl. Physiol. 25:463–468, 1968.
Mitamura, Y., T. Mikami, H. Sugawara, and C. Yoshimoto. An optimally controlled respirator.IEEE Trans. Biomed. Eng. 13:846–853, 1971.
Pearce, D.H. A system for measurement of oxygen consumption and control of inspired carbon dioxide.IEEE Trans. Biomed. Eng. 18:235–237, 1971.
Radford, E.P., B.G. Ferris, and B.C. Krietz. Clinical use of a nomogram to estimated proper ventilation during artificial respiration.N. Engl. J. Med. 251:877–884, 1954.
Severinghaus, J.W., and M. Stupfel. Alveolar dead space as an index of distribution of blood flow in pulmonary capillaries.J. Appl. Physiol., 10:335–348, 1957.
West, J.B.Respiratory Physiology—The Essentials, Baltimore, Maryland: Williams and Wilkins, 1974.
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This work was supported by Siemens-Elema, Biochem Int. and Shriners Childrens Hospital.
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Ohlson, K.B., Westenskow, D.R. & Jordan, W.S. A microprocessor based feedback controller for mechanical ventilation. Ann Biomed Eng 10, 35–48 (1982). https://doi.org/10.1007/BF02584213
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DOI: https://doi.org/10.1007/BF02584213