Journal of clinical monitoring
-
Comparative Study
Performance of erroneously filled sevoflurane, enflurane and other agent-specific vaporizers.
Erroneous filling of an agent-specific anesthesia vaporizer may result in concentration and potency outputs that are very different from those expected from the concentration dial setting. Enflurane and sevoflurane have relatively similar saturated vapor pressures (SVPs 175 mmHg and 160 mmHg, respectively, at 20 degrees C) and potencies (MACs 1.68% and 2%, respectively). We derived an equation to relate the vapor concentration output of an agent-specific vaporizer to the gas inflow splitting ratio (SR) created by the vaporizer and the SVP of the potent inhaled agent. ⋯ When an agent-specific variable bypass vaporizer is erroneously filled, the vapor concentration outputs can be predicted from the splitting ratio created by setting the vaporizer concentration dial and the SVP of the agent.
-
To assess the correlation and accuracy of end-tidal PCO2 (PetCO2) sampled via nasal cannulae in pediatric patients by comparison to the criterion standard PaCO2, and to identify sources of error during PetCO2 monitoring via nasal cannulae. ⋯ Several factors-some controllable and all recognizable-affect the accuracy of PetCO2 monitored via nasal cannulae in pediatric patients. When these factors are not present, PetCO2 correlates well with PaCO2 and appears to be a useful monitor of ventilatory status during conscious or deep sedation.
-
To test whether a neural network-based method could differentiate between tracheal and esophageal intubation in anesthetized patients by recognizing breathing circuit pressure and flow waveform patterns. ⋯ A neural network differentiated consistently tracheal from esophageal intubation when the ventilation test mode was used. The ventilation mode employed is feasible in most adult patients undergoing elective procedures under general anesthesia. Further research is required to train neural networks to recognize esophageal intubation in different age groups and when different ventilation modes are applied.
-
This study monitored somatosensory evoked potentials (SSEP) at the median and ulnar nerves in awake volunteers placed in a simulated position for prone surgery. Neurologic symptoms were used as a surrogate endpoint for position related peripheral nerve injury; the occurrence of these symptoms was correlated with the presence or absence of SSEP changes in median and ulnar nerves. ⋯ While all SSEP changes were associated with symptoms, the development of symptoms in 3 of 7 patients without SSEP changes suggests that SSEPs may be an imperfect monitor for the detection of positioning injury. The limited sensitivity of SSEPs in this study may be due to the duration of the monitoring, sample size, or the validity of symptoms as a surrogate for nerve injury.