Barbiturate-Curare-Induced Apnea for Artificial Respiration Studies on Normal Adults. I

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Abstract
Methods of artificial respiration were evaluated on approx. 50 normal adult male volunteers, rendered totally apneic with barbiturate-curare mixtures. Various amts. of intra-ven. barbiturates were used to produce optimal depression of the subjects. Then, large intraven. doses of curare products produced complete myoneural blockage with a resultant flaccid "muscular type" total apnea. In this state resuscitation studies were accomplished measuring ventilation, circulation, and air flow patterns. In the studies of ventilation (with a spirometer) and air flow patterns (with a pneumotachograph) cyclopropane-O2 mixtures were used intermittently to produce profound depth of anesthesia. The pneumotachograph study revealed that such subjects were in a state of complete respiratory control and muscular quiescence. No spontaneous respiratory movements appeared in the tracings and all variations were attributable to the artificial respiration manipulations. Each study on the circulatory effects of artificial respiration required approx. 1 hr., and apnea was maintained by repeated doses of curare and a constant intraven. infusion of 0.5% pentothal. In all cases, a standard cuffed endotracheal tube (coated with a water-soluble anesthetic lubricant) was inserted under direct visualization. Atropine or scopolamine was routinely used as a preanesthetic medication. In most instances a topical anesthetic was sprayed into the upper respiratory passages preceeding intubation. The doses of barbiturate varied up to 3.6 to 3.8 g.; the total curare was frequently in excess of 25 mg. dimethyl d-tubocurarine chloride and 10-20 mg. of the standard d-tubocurarine chloride. There were no complica-tions except for the occurrence of 3 cases of bronchospasm severe enough to render the Schafer method inadequate. N2O-O2 (80:20) mixtures were administered until spontaneous respirations returned. Those subjects receiving massive doses of either or both drugs required careful observation and detuba-tion to prevent sequellae. One man had a condition resembling myasthenia gravis for 36 hrs. following the procedure. Analeptics were rarely used. The method is recommended for the study of artificial or controlled respiration only by those with adequate training, experience and facilities.

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