Janet Tesler

MRI mapping of cerebrovascular reactivity using square wave changes in end-tidal PCO2.

Cerebrovascular reactivity can be quantified by correlating blood oxygen level dependent (BOLD) signal intensity with changes in end‐tidal partial pressure of carbon dioxide (PCO2). Four 3‐min cycles of high and low PCO2 were induced in three subjects, each cycle containing a steady PCO2 level lasting at least 60 sec. The BOLD signal closely followed the end‐tidal PCO2. The mean MRI signal intensity difference between high and low PCO2 (i.e., cerebrovascular reactivity) was 4.0 ± 3.4% for gray matter and 0.0 ± 2.0% for white matter. This is the first demonstration of the application of a controlled reproducible physiologic stimulus, i.e., alternating steady state levels of PCO2, to the quantification of cerebrovascular reactivity. Magn Reson Med 45:1011–1013, 2001.

A simple apparatus for accelerating recovery from inhaled volatile anesthetics

Hyperpnea increases anesthetic elimination but is difficult to implement with current anesthetic circuits without decreasing arterial Pco2. To circumvent this, we modified a standard resuscitation bag to maintain isocapnia during hyperpnea without rebreathing by passively matching inspired Pco2 to minute ventilation. We evaluated the feasibility of using this apparatus to accelerate recovery from anesthesia in a pilot study in four isoflurane-anesthetized dogs. The apparatus was easy to use, and all dogs tolerated being ventilated with it. Under our experimental conditions, isocapnic hyperpnea reduced the time to extubation by 62%, from an average of 17.5 to 6.6 min (P = 0.012), but not time from extubation to standing unaided. This apparatus may provide a practical means of applying isocapnic hyperpnea to shorten recovery time from volatile anesthetics.

Rescuer position for tracheal intubation on the ground

BACKGROUND Emergency oral tracheal intubations in the pre-hospital setting can be more difficult because the rescuers position with respect to a patient lying on the ground may not provide optimal conditions for intubation. Since optimal visualisation of the larynx often depends on the force generated during laryngoscopy, we measured the pressure required for intubation (P(i)) as well as the maximum pressure (P(max)) that can be generated with the laryngoscopy blade in seven intubator positions. METHODS Nineteen hospital personnel with intubation experience participated in this study. A modified #3 Macintosh laryngoscope blade was used to measure the pressure exerted on the tongue of a manikin placed on the ground during intubation. The following positions were studied: standard, sitting, prone, kneeling, left and right lateral decubitus and straddling. RESULTS Intubating in the straddling position required the lowest P(i), as a percent of P(max) (68+/-14%). This was significantly less than the prone, right lateral decubitus and sitting positions. (Tukeys W procedure, P<0.05) CONCLUSION The straddling position affords the intubator significantly more reserve force than the prone, right lateral decubitus or sitting position. We suggest that the straddling position may be an advantageous position for pre-hospital intubations especially when visualisation of the glottis is difficult.