Journal of clinical monitoring
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We quantitatively compared the acoustic characteristics of passage of an endotracheal tube into the trachea with those of passage into the esophagus by analyzing the loudness and frequency (90% spectral edge frequency) of the sounds when auscultated at the suprasternal notch. We found that there was a significant difference (P less than 0.01) in maximum loudness between esophageal and tracheal intubations (0.15 +/- 0.05 and 0.25 +/- 0.06 V, respectively). However, there were no significant differences between the 90% spectral edge frequencies. We conclude that, without directly comparing the maximal acoustic amplitude of tracheal intubation with that of esophageal in each patient, one cannot distinguish between the two types of intubation by means of auscultation.
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Since pulse oximetry is now an ASA standard for intraoperative monitoring, we sought to determine the intraoperative failure rate for this device. We prospectively evaluated the intraoperative failure rate of our pulse oximeters at the four University of Washington Hospitals (University of Washington Medical Center, Veterans Affairs Medical Center [VAMC], Children's Hospital and Medical Center, and Harborview Medical Center [HMC]) recorded from April 1989 to August 1989. We defined failure as the inability to obtain any oximetry reading for a cumulative period of more than 30 minutes during any anesthetic procedure after all equipment malfunctions had been eliminated. ⋯ When the device did fail in a patient, it did not function for 32% of the mean anesthesia time. We conclude that the intraoperative use of the pulse oximetry can provide information about blood oxygen saturation in most patients. However, in approximately 1% of the patients we studied in the operating room, mechanically functioning pulse oximeters failed to provide readings of blood oxygen saturations during routine operative use.
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Epinephrine is routinely used as a marker for intravascular injection during administration of regional anesthesia. The cardiovascular response of patients on beta-blockers to such a test dose has been reported to be unpredictable. ⋯ The lowest heart rate recorded was 28 beats/min. We conclude that, in middle-aged beta-blocked men, intravenous injection of a standard epinephrine-containing test dose will predictably cause significant hypertension followed by marked bradycardia.
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We continuously monitored spontaneous respiration after extubation by end-tidal CO2 tension (PETCO2) in 19 patients aged 20 to 72 years who had undergone major operations. The respiratory gas was sampled from the nasopharynx via a special nasal catheter and analyzed by a side-stream analyzer. In each case, optimal placement of the nasal catheter was determined by CO2 waveform and the capnograms were recorded for waveform analysis and trend monitoring. ⋯ While the mean values for PETCO2 and PaCO2 were similar, several patients had large differences for PaCO2 to PETCO2. The differences of the individual patients did not differ significantly between the various times of measurement. We conclude that this form of capnometry is well suited for continuous, noninvasive monitoring of respiration in nonintubated, spontaneously breathing patients.
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We describe and evaluate a new apparatus that monitors end-tidal carbon dioxide (PETCO2) and augments the inspired oxygen concentration in awake, sedated patients. The unit was evaluated for its effectiveness as an oxygenation device and its accuracy as a predictor of PaCO2 through the correlation of PaCO2 with PETCO2. Twenty cardiac surgical patients, physical status ASA 2-4, participated in this study. ⋯ The ratios of PETCO2 compared with PaCO2 were 0.98, 0.94, and 0.85, with correlation coefficients of r = 0.81, 0.85, and 0.63, respectively. The PaO2 values were 114, 154, and 183 mm Hg for the corresponding nasal oxygen flow rates of 2, 4, and 6 L/min, respectively. This study indicates that this modified nasal cannula provides supplemental oxygen adequately and yields a satisfactory reflection of the PaCO2 depending on the oxygen flow rate delivered.