In darkness, observers partially paralyzed with curare make large (greater thn 20 degrees) gaze- and dosage-dependent errors in visually localizing eye-level-horizontal and median planes, in matching the location of a sound to a light, and in pointing at a light. In illuminated, structured visual localization and pointing are accurate but errors in auditory-to-visual matches remain. Defects in extraretinal eye position information are responsible for all errors. The influence of extraretinal eye position information on visual localization is suppressed by a structured visual field but is crucial both in darkness and for intersensory localization if visual capture is prevented.
When rats are infused intravenously continuously with blood enriched in an extracorporeal system with 100% CO2, they are found to excrete the infused CO2 quantitatively. The excretion is accomplished by increasing ventilation in proportion to the infusion rate. Neither mean arterial pH nor Pco2 shows a statistically significant change. This constancy of composition is observed at CO2 infusion rates ranging from zero to an amount equal to six times the resting metabolic CO2 production. Similarity of this hyperpnea to the chief characteristics of the hyperpnea of exercise is notable. Increased oxygen uptake during this procedure is about 3.5 ml/l. of ventilation, a reasonable value for the oxygen cost of ventilation. Since, during this process the animal is quiescent and shows no other metabolic changes it is suggested that the effective signal for the regulation of arterial Pco2 is CO2 itself. The ability of the experimental animal to respond successfully to high rates of loading seems to be limited by failure to make appropriate circulatory adjustments. Removing CO2 by equilibrating blood with 100% o2 in the extracorporeal circuit decreases ventilation, but readily leads to an uncontrolled alkalosis. Submitted on April 13, 1960
Jet ventilation is often used during laryngoscopy to permit improved visualization of the larynx and to eliminate a potentially flammable endotracheal tube when laser surgery of the airway is performed. Observation of chest wall movement and blood gas analysis are the usual standards for assessing the adequacy of ventilation during jet ventilation. It is reasonable to hypothesize that measurement of end-tidal CO2 concentrations during jet ventilation can be used to assess the adequacy of ventilation during jet ventilation. To test this hypothesis, end-tidal CO2 concentrations were determined during mechanical ventilation through an endotracheal tube and during jet ventilation. At the time that each end-tidal measurement was obtained, a sample of arterial blood was also obtained for later blood gas analysis. For both mechanical ventilation and jet ventilation, well defined relationships between end-tidal CO2 and arterial CO2 tensions were obtained. However, the relationships are distinct: the difference in arterial to end-tidal CO2 tension during supraglottic jet ventilation at a conventional respiratory rate was found to be 13.4 +/- 6.8 mm Hg (mean +/- SD) compared with 5.7 +/- 5.2 mm Hg obtained during conventional ventilation through an endotracheal tube.
SummaryA randomised cross-over study was performed in 34 patients with no evidence of airway difficulties, following induction of general anaesthesia, to compare the efficacy of the Levitan FPS scope TM (LFPS) and the single-use bougie for tracheal intubation during simulated grade IIIa laryngoscopy. Success rates for intratracheal placement of the device, and the time required for insertion and tracheal intubation were recorded. Both devices were equally successful (31 ⁄ 34 for the LFPS vs 29 ⁄ 34 for the bougie) for insertion into the glottis. The mean insertion time for the LFPS was statistically longer than that for the bougie (4.4-12.5 s) but this difference was not clinically relevant. Intubation times were similar between the two devices. Major problems hindering successful intubation using the LFPS were the presence of a narrow epiglottic-pharyngeal wall space and copious secretions. An inability to maintain the desired shape was the principal cause of failure with the bougie.
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