Anesthesia and analgesia
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Anesthesia and analgesia · Feb 1996
Comparison of end-tidal PCO2 and average alveolar expired PCO2 during positive end-expiratory pressure.
The measurement of average alveolar expired PCO2 (PAECO2) weights each PCO2 value on the alveolar plateau of the CO2 expirogram by the simultaneous change in exhaled volume. PAECO2 can be determined from a modified analysis of the Fowler anatomic dead space (VDANAT). In contrast, end-tidal PCO2 (PETCO2) only measures PCO2 in the last small volume of exhalate. ⋯ This difference was significantly magnified during PEEP ventilation. The overestimation of PAECO2 by PETCO2 can result in a falsely high assessment of overall alveolar PCO2. Moreover, the use of PETCO2 to estimate alveolar PCO2 in the determination of the alveolar dead space fraction can result in falsely low and even negative values of alveolar dead space.
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Anesthesia and analgesia · Feb 1996
The effects of needle type, gauge, and tip bend on spinal needle deflection.
Although the use of fine-gauge spinal needles reduces the incidence of postdural puncture headache, they are associated with increased risk of placement failure as a result of deflection and bending. This in vitro study quantifies spinal needle deflection from the axis of insertion with respect to needle type, gauge, and tip bend. In addition to straight-tip needles, those with standardized 5 degrees and 10 degrees tip bends were studied. ⋯ Straight-tip Q needle deflection, but not W or S, was correlated with gauge and depth of insertion. Although there were differences within needle type groups, needle deflection was generally correlated with the degree of tip bend. We conclude that spinal needle deflection is dependent on the type of needle (W < S < Q), and that the magnitude of deflection is related to gauge (large < small) and tip bend (straight < 5 degrees < 10 degrees).