HST 583 - Fall 2004Assignment # 2Due 10/6/2004Apneic Oxygenation Discussion CaseFrumin, M.J.; Epstein, R.M.; Cohen, G. Apneic oxygenation in man. Anesthesiology, 1959 Nov-Dec:789-98Summary from paper verbatimApneic oxygenation was carried out in 8 human subjects for periods between 15 and 55 minutes. The mechanism by which oxygenation was maintained during the peeriod of increaseing respiratory acidosis was described. A moderate to severe arterial hypertension usually developed followed by a mild hypotension when artificial respiration was resumed. The increases in plasma sodium. potassium, epinephrine and norepinephrine concentrations during the apnea were described and their relationship to the hypertension and the electrocardiographic changes were discussed. The electrocardiographic patterns were usually unchanged during the production of profound acidosis with arrhythmias noted only twice, once after 7 minutes and once after 53 minutes of apnea. In the latter instance, ventricular tachycardia lasting one minute accompanied the institution of artificial respiration and carbon dioxide elimination. A severe metabolic acidosis accompanied the respiratory acidosis.Banzett’s Notes on this paper8 patients in for minor surgery. premed with 50-100mg meperidine and 0.4mg scoplomine. 5 min 100% O2, then hypnotic dose of thiopenthal and 100mg succinylcholine chloride. Intubated and bag ventilated with 100% O2 for 30 min. more thiopenthal and either succ or tubocurarine as needed. ET tube left connected to bag of O2 . Apnea allowed to persist for 30-55 min. Subj # apnea lowest SaO2 Lowest pHa highest PaCO2 Avg rate of rise of CO21 30 min 100 % - --2 45 100 - --3 55 100 - --4 45 100 6.88 160 Torr 3.0 Torr/min5 18 99 6.97 130 1.96 45 98 6.87 160 3.07 53 98 6.72 250 3.58 38 100 6.96 130 2.7QuestionConsider the failure of the alveolar gas equation in this case. Patients were apneic for up to 55 min. How long will internal body O2 supply last? We can assume they kept on metabolizing to stay alive (probably at 200 to 300 ml/min VO2 ) yet VE and thus VA = zero. How can this be? Hint: Try to solve the alveolar Fick's equations for O2 and CO2 assuming normal metabolic VO2 and VCO2 must continue. Why does the standard equation fail and what is the appropriate equation for this case? What is going on here physiologically?Other RefsTissue carbon dioxide stores: magnitude of acute change in the dog, 1964 S. F. Sullivan, R. W. Patterson, and E. M. Papper Am J Physiol 206: 887-890 Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York CityCarbon dioxide washout curves were determined in hyperventilated dogs. Direct measurement of mixed venous carbon dioxide tension allowed calculation of changes in whole-body CO2 stores. The average whole-body CO2 dissociation constant in ten studies was 3.73 ml/kg mm. The limitingfactor in reaching a new steady-state value was represented by a slow compartment in the washout curve. The average rate constant for this compartment was 0.062 min–1. The slowest compartment in this analysis has a 98% change in 1 hr, therefore the experimentally determined whole-body dissociation constant should closely approximate actual changes in tissue CO2 stores, excluding bone and fat.The Determination of Total Body Exchangeable O2 Stores. Carroll E. Cross, Bernard S. Packer, Michael Altman, J. Bernard L. Gee, H. Victor Murdaugh, Jr., and Eugene D. Robin, J Clin Invest. 1968 October; 47 (10): 2402–2410Department of Medicine, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15213A method is described for the measurement of total body exchangeable oxygen stores (TBO2). It is based on the dilution of the stable oxygen isotope, 18O2, by the body exchangeable oxygen stores under circumstances in which 18O2 steady-state equilibrium was evaluated simultaneously for botharterial and venous blood compartments. After evaluation of several simplifying assumptions, TBO2 values in dog, normal man, and anemic patients were measured. The magnitude of the exchangeable nonlung oxygen stores was 11.0 ± 3.1 ml/kg (SD) in 5 dogs, 11.9 ± 2.1 ml/kg in 10 normal subjects, and 7.0 ± 1.6 ml/kg in 8 patients with severe anemia (hematocrits of 25% or