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PURPOSE: Recent publications have suggested that pulse oximeters exhibit reduced accuracy in dark-skinned patients during periods of hypoxemia. Masimo SET® (Signal Extraction Technology®) has been designed, calibrated, and validated using nearly equal numbers of dark and light skinned subjects, with the goal of eliminating differences between pulse oximetry saturation (SpO2) and arterial oxygen saturation (SaO2) values due to skin pigmentation. The accuracy concerns reported in dark-skinned patients led us to perform a retrospective analysis of healthy Black and White volunteers.METHODS: Seventy-five subjects who self-identified as being racially Black or White underwent a desaturation protocol where SaO2 values were decreased from 100% to 70%, while simultaneous SpO2 values were recorded using Masimo RD SET® sensors.RESULTS: Statistical bias difference (mean error) and precision (standard deviation of error) were -0.20 + 1.40% for Black and -0.05 + 1.35% for White subjects. Plots of SpO2 versus SaO2 appear nearly identical for both races throughout the saturation range from 70% to 100%. Box plots grouped in 1% saturation bins, from 89-96%, and plotted against concomitant SaO2 values, show that occult hypoxemia (SaO2 < 88% when SpO2 = 92-96%) occurred in only 0.2% of White subject data pairs, but not in any Black subjects. CONCLUSIONS: There were no clinically significant differences in bias (mean difference of SpO2-SaO2) found between Black and White subjects. Occult hypoxemia was rare and did not occur in Black subjects. Masimo RD SET® is highly accurate and can be used with equal assurance in people with dark or light skin.

The measurement of hemoglobin concentration in the blood (Hb) plays a central role in the detection, evaluation, and management of chronic and acute anemia. The gold standard for laboratory determination of Hb is hemoglobin cyanide (HiCN).1 HiCN testing is not routinely used in hospitals due to its complexity, so cyanide-free central laboratory hematology analyzers (e.g., Coulter, Sysmex) have become the clinical standard.2 It is tempting to assume that satellite CO-Oximeters (e.g., ABL, Radiometer, Denmark; Nova, Nova Biomedical, Waltham, MA) used for arterial blood gas measurement in the operating room or critical care unit are interchangeable with hematology analyzers, but in fact they are not. Pulse CO-Oximetry is the multiwavelength technology contained in the first devices to have received Food and Drug Administration 510(k) clearance for the continuous, noninvasive monitoring of total hemoglobin (SpHb; Masimo, Irvine, CA). Generally speaking, SpHb monitoring is not yet as accurate as laboratory hemoglobin (lab-Hb), and it is therefore not intended today as a replacement for lab-Hb. The focus should instead be on the value-added benefits of supplementing intermittent, delayed lab-Hb values with continuous, real-time visibility of whether Hb is stable, increasing, or decreasing. The purpose of this article is to provide a perspective on the appropriate role and evaluation of SpHb and the value-added benefits of continuous Hb monitoring. We offer an alternative viewpoint to balance the 3 separate but similar opinions published earlier in Anesthesia & Analgesia by Drs. Rice, Gravenstein, and Morey.3–5 These authors propose “what is required of a noninvasive hemoglobin monitor and whether the conventional statistics adequately answer our questions about clinical accuracy.” In doing so, Rice et al. concluded that the accuracy of SpHb monitoring “is not good enough to make the (a) transfusion decision.” In the present article, clinical advisors to Masimo Corporation respond to these evaluations with a measured perspective on the value-added clinical decision process that this technology will bring to patient management and safety. It is also time to review and reassess the fundamental assumptions regarding lab-Hb and its use in making clinical decisions. Given that it is noninvasive and its ability to provide continuous, real-time data that can be correlated at bedside with events happening to the patient, SpHb monitoring offers a new paradigm and opens up new possibilities for improved patient care.

Background Respiration monitoring is necessary during sedation for dental treatment. Recently, acoustic respiration rate (RRa™), an acoustics-based respiration monitoring method, has been used in addition to auscultation or capnography. The accuracy of this method may be compromised in an environment with excessive noise. This study evaluated whether noise from the ultrasonic scaler affects the performance of RRa in respiratory rate measurement. Methods We analyzed data from 49 volunteers who underwent scaling under intravenous sedation. Clinical tests were divided into preparation, sedation, and scaling periods; respiratory rate was measured at 2-s intervals for 3 min in each period. Missing values ratios of the RRa during each period were measuerd; correlation analysis and Bland-Altman analysis were performed on respiratory rates measured by RRa and capnogram. Results Respective missing values ratio from RRa were 5.62%, 8.03%, and 23.95% in the preparation, sedation, and scaling periods, indicating an increased missing values ratio in the scaling period (P < 0.001). Correlation coefficients of the respiratory rate, measured with two different methods, were 0.692, 0.677, and 0.562 in each respective period. Mean capnography-RRa biases in Bland-Altman analyses were −0.03, −0.27, and −0.61 in each respective period (P < 0.001); limits of agreement were −4.84–4.45, −4.89–4.15, and −6.18–4.95 (P < 0.001). Conclusions The probability of missing respiratory rate values was higher during scaling when RRa was used for measurement. Therefore, the use of RRa alone for respiration monitoring during ultrasonic scaling may not be safe.

Introduction The interpretation and application of arterial blood-gas (ABG) data is a task that anesthesiologists must often perform under difficult circumstances. The time is 3:00 AM; we are fatigued and distracted by multiple other simultaneous tasks; we need to take action on these ABG results now. In this setting, which bears similarities to piloting an aircraft on instruments in bad weather, it is useful to have a simple algorithm or “check-list,” both to ensure consistency and obtain a correct answer within a short time. The purpose of this talk is to develop such an algorithm and apply it to specific clinical examples, wherein we shall interpret both oxygenation and acid-base status, and then prescribe appropriate treatment.

Background A new eight-wavelength pulse oximeter is designed to measure methemoglobin and carboxyhemoglobin, in addition to the usual measurements of hemoglobin oxygen saturation and pulse rate. This study examines this device's ability to measure dyshemoglobins in human volunteers in whom controlled levels of methemoglobin and carboxyhemoglobin are induced. Methods Ten volunteers breathed 500 ppm carbon monoxide until their carboxyhemoglobin levels reached 15%, and 10 different volunteers received intravenous sodium nitrite, 300 mg, to induce methemoglobin. All were instrumented with arterial cannulas and six Masimo Rad-57 (Masimo Inc., Irvine, CA) pulse oximeter sensors. Arterial blood was analyzed by three laboratory CO-oximeters, and the resulting carboxyhemoglobin and methemoglobin measurements were compared with the corresponding pulse oximeter readings. Results The Rad-57 measured carboxyhemoglobin with an uncertainty of +/-2% within the range of 0-15%, and it measured methemoglobin with an uncertainty of 0.5% within the range of 0-12%. Conclusion The Masimo Rad-57 is the first commercially available pulse oximeter that can measure methemoglobin and carboxyhemoglobin, and it therefore represents an expansion of our oxygenation monitoring capability.

Between February, 2000 and August, 2002 three surveys have been submitted to the program directors of the anesthesiology training programs in the United States (U.S.) to assess the departments' needs for faculty and financial support from their institutions. In this article we present the results of a fourth follow-up survey. This survey also asked questions regarding the need for additional support to meet the new 80-h workweek resident requirement and asked the average academic time offered to faculty. The average department has 40 faculty members with 3.7 open faculty positions in the 78% of departments with open positions. Only 25% of the departments planned to add personnel to comply with the 80-h resident workweek. Fifty-one percent of the departments had a positive financial margin of 15,908 dollars/full-time equivalent (FTE) faculty anesthesiologist (faculty FTE), whereas 34% had a negative margin of 42,603 dollars/faculty FTE. The overall institutional support was 85,607 dollars/faculty FTE, which is a 43% increase over the previous year. The average academic time provided to faculty was 13.8%, a decline from 20% in 2000. Twenty-five percent of departments have closed an anesthetizing location as a result of a lack of faculty in 2003. Open faculty positions in U.S. training programs have remained fairly constant at 8% to 10% from 2000 to 2003. Institutional support for training departments has more than doubled since 2000, reaching approximately 85,000 dollars/faculty in 2003.

UNLABELLED This article examines recent trends in the management of academic physician practice groups, and in particular the allocation of revenues and expenses to anesthesiology departments. The history of academic group practice is traced, beginning with the "corporate model," in which each department functioned in financial independence from the others. This evolved gradually into the "feudal system," in which departments were ostensibly independent, but paid variable and often large "assessments" to the central group. The final stage in this evolution is the "big bag," in which all clinical revenue is pooled by the central practice group, and then distributed by the group to departments or individuals according to some compensation plan formula. The advantages and disadvantages of each of these systems are discussed as they apply to anesthesiology departments. A productivity-based compensation plan formula under the big bag system is calculated for a typical anesthesiology department. This calculation shows that if the compensation formula is truly based on measured clinical productivity, anesthesiology departments may actually fare better under the big bag than under the feudal system. Finally, options for survival in the academic practice groups of the future are discussed. IMPLICATIONS The history, current status, and trends of finances in academic anesthesiology departments are reviewed. Knowledge of these issues will help departments develop funds allocation methods to ensure that they receive an appropriate share of their faculty practice group's clinical income.

In this lecture we review recent advances in the monitor- ing of patient oxygenation. The transport of oxygen from the atmosphere to the mitochondrion will be discussed, and monitors that function at each of four stages of the transport process will be described. These four stages in- clude respired gas, arterial blood, tissue, and venous blood. Respired gas monitors will be mentioned only briefly. Recent developments in pulse oximetry will be reviewed in detail. Continuous intraarterial blood-gas sensors will be contrasted with other arterial oxygen mon- itors. We will also cover tissue oxygen monitoring and mixed-venous oximetry.

Objective.To describe a new pulse oximetry technology and measurement paradigm developed by Masimo Corporation.Introduction.Patient motion, poor tissue perfusion, excessive ambient light, and electrosurgical unit interference reduce conventional pulse oximeter (CPO) measurement integrity. Patient motion frequently generates erroneous pulse oximetry values for saturation and pulse rate. Motion-induced measurement error is due in part to wide spread implementation of a theoretical pulse oximetry model which assumes that arterial blood is the only light-absorbing pulsatile component in the optical path. Methods.Masimo Signal Extraction Technology(SET®) pulse oximetry begins with conventional red and infrared photoplethysmographic signals, and then employs a constellation of advanced techniques including radiofrequency and light-shielded optical sensors, digital signal processing, and adaptive filtration, to measure SpO2 accurately during challenging clinical conditions. In contrast to CPO which calculates O2 saturation from the ratio of transmitted pulsatile red and infrared light, Masimo SET pulse oximetry uses a new conceptual model of light absorption for pulse oximetry and employs the discrete saturation transform (DST) to isolate individual “saturation components” in the optical pathway. Typically, when the tissue under analysis is stationary, only the single saturation component produced by pulsatile arterial blood is present.In contrast, during patient motion, movement of non-arterial components (for example, venous blood) can be identified as additional saturation components (with a lower O2 saturation). When conditions of the Masimo model are met, the saturation component corresponding to the highest O2 saturation is reported by the instrument as SpO2. Conclusion.The technological strategies implemented in Masimo SET pulse oximetry effectively permit continuous monitoring of SpO2 during challenging clinical conditions of motion and poor tissue perfusion.

To compare the performance of five pulse oximeters during hypoperfusion, probe motion, and exposure to ambient light interference.Prospective study.Laboratory facility at a university medical center.8 unanesthetized, ASA physical status I volunteers.We evaluated five common pulse oximeters with respect to three scenarios: (1) an operating room light was shone on oximeter probes, (2) a motion generator was used to generate 2 Hz and 4 Hz hand motion, and (3) a pneumatic compression device overlying the brachial artery was used to simulate hypoperfusion. Electrocardiographic (ECG) and arterial blood gas values were considered gold standards for heart rate (HR) and oxygen saturation (SpO2) respectively. SpO2 nondisplay and values greater than 4% from simultaneous arterial SaO2-oximeter values were defined as errors. Nondisplay of HR, or HR greater than 5% from ECG values, were also considered errors.The Ohmeda and Nellcor N200 with finger probe had the highest total failure rates with respect to both SpO2 and HR due to ambient light interference (p0.05). The Nellcor N200 with finger probe and N200 with C lock were the most accurate with regard to SpO2 during 2 Hz and 4 Hz motion (p0.05). However, all oximeters failed dramatically during 4 Hz motion when measuring HR. In the hypoperfusion model, the Nellcor N200 with finger probe and the Nellcor C Lock oximeters performed significantly better than all others in terms of both HR and SpO2 (P0.05), while the Criticare oximeter failed 100% of the time.There are significant differences in the accuracy of commercially available pulse oximeters during nonideal circumstances, with failure rates varying from approximately 5% to 50% depending on the oximeter and source of interference. Furthermore, no single oximeter performed the best under all conditions.

Background Pulse oximetry is considered a standard of care in both the operating room and the postanesthetic care unit, and it is widely used in all critical care settings. Pulse oximeters may fail to provide valid SpO2 data in various situations that produce low signal-to-noise ratio. Motion artifact is a common cause of oximeter failure and loss of accuracy. This study compares the accuracy and data dropout rates of three current pulse oximeters during standardized motion in healthy volunteers. Methods Ten healthy volunteers were monitored by three different pulse oximeters: Nellcor N-200, Nellcor N-3000, and Masimo SET (prototype). Sensors were placed on digits 2, 3, and 4 of the test hand, which was strapped to a mechanical motion table. The opposite hand was used as a stationary control and was monitored with the same pulse oximeters and an arterial cannula. Arterial oxygen saturation was varied from 100% to 75% by changing the inspired oxygen concentration. While SpO2 was both constant and changing, the oximeter sensors were connected before and during motion. Oximeter errors and dropout rates were digitally recorded continuously during each experiment. Results If the oximeter was functioning before motion began, the following are the percentages of time when the instrument displayed an SpO2 value within 7% of control: N-200 = 76%, N-3000 = 87%, and Masimo = 99%. When the oximeter sensor was connected after the beginning of motion, the values were N-200 = 68%, N-3000 = 47%, and Masimo = 97%. If the alarm threshold was chosen SpO2 less than 90%, then the positive predictive values (true alarms/total alarms) are N-200 = 73%, N-3000 = 81%, and Masimo = 100%. In general, N-200 had the greatest SpO2 errors and N-3000 had the highest dropout rates. Conclusions The mechanical motions used in this study significantly affected oximeter function, particularly when the sensors were connected during motion, which requires signal acquisition during motion. The error and dropout rate performance of the Masimo was superior to that of the other two instruments during all test conditions. Masimo uses a new paradigm for oximeter signal processing, which appears to represent a significant advance in low signal-to-noise performance.

Flap-valve obstruction to expiratory flow (V) in a major bronchus can result from inspissated secretions, blood, or foreign body. During inhalation, increasing airway caliber preserves inspired V past the obstruction ; during exhalation, decreasing airway diameter causes airflow obstruction and even frank gas trapping. We reasoned that the resultant sequential, biphasic exhalation of the lungs would be best detected by measuring exhaled V versus time. Accordingly, we designed an airway obstruction element in a mechanical lung model to examine flap-valve bronchial obstruction. A mechanical lung simulator was ventilated with a pressure-limited flow generator, where f = 10 /min, tidal volume = 850 mL, and respiratory compliance = 40 mL/cm H 2 O. Airway V (pneumotachometer) and pressure (P) were digitally sampled for 1 min. Then, the circumference of the diaphragm in a respiratory one-way valve was trimmed to generate unidirectional resistance to expiratory V. Measurement sequences were repeated after this flap-valve was interposed in the right main-stem bronchus. Integration of airway V versus time generated changes in lung volume. During flap-valve obstruction of the right bronchus, the V-time plot revealed preservation of peak expired flow from the normal lung, followed by retarded and decreased flow from the obstructed right lung. Gas trapping of the obstructed lung occurred during conditions of decreased expiratory time and increased expiratory resistance. Airway P could not differentiate between bronchial and tracheal flap-valve obstruction because P decreased abruptly in both conditions. The flow-volume loop displayed less distinctive changes than the flow-time plot, in part because the flow-volume loop was data (flow) plotted against its time integral (volume), with loss of temporal data. In this mechanical lung model, we conclude that bronchial flap-valve obstruction was best detected by the flow-time plot, which could measure the sequential emptying of the lungs.

This case report describes the successful treatment of chronic headache from intracranial hypotension with bilateral transforaminal (TF) lumbar epidural blood patches (EBPs). The patient is a 65-year-old male with chronic postural headaches. He had not had a headache-free day in more than 13 years. Conservative treatment and several interlaminar epidural blood patches were previously unsuccessful. A transforaminal EBP was performed under fluoroscopic guidance. Resolution of the headache occurred within 5 minutes of the procedure. After three months without a headache the patient had a return of the postural headache. A second transforaminal EBP was performed again with almost immediate resolution. The patient remains headache-free almost six months from the time of first TF blood patch. This is the first published report of the use of transforaminal epidural blood patches for the successful treatment of a headache lasting longer than 3 months.

Cm! 1 A 77-year-old white man was admitted with a left-sided pleura1 effusion. His past history included prolonged asbestos exposure and heavy smoking. He presented with dyspnea and wcight 10s~. Physical examination revealed a thin individual with a large barrel-shaped chest. Preoperative pulmonary function tests showed an FEVt of 1.2 L. A computerized tomography scan showed multiple pleura1 plaques and areas of thickening, especially along the mediastinal pleura. Because of the patient’s poor pulmonary status, flexible bronchoscopy and thoracoscopy were scheduled. The planned perioperative monitoring included indwelling arterial pressure, end-tidal CO1 (ETCO& and peripheral oxygen saturation (SpO$ Anesthesia was induced with thiamylal, fentanyl, and vecuronium. The trachea was intubated initially with a single-lumen endotracheal tube for flexible fiberoptic bronchoscopy. Following this, a double-lumen right-sided endobronchial tube was inserted. After confirmatory chest auscultation and flexible bronchoscopy, the patient was positioned in the right lateral decubitus position. Anesthetic maintenance included fentanyl, vecuronium, and isoflurane/air/oxygen. One-lung ventilation (OLV) was maintained during the thoracoscopic procedure. During diagnostic thoracoscopy, the stopcock of the cannula was left open to room air to maintain an open pneumothorax. Air insufflation pressures of 10 to 11 mmHg were used to attain better visibility. Hemodynamic monitoring and management included special attention to changes in blood pressure, heart rate and rhythm, end-tidal CO2 because of the potential for arrhythmias, fa11 in venous return and cardiac output, gas embolism, and direct compression of cardiac structures. The surgical procedure involved multiple pleura1 biopsies and

An elderly surgical patient acquired a life-threatening methemoglobinemia as a result of topical benzocaine spray to the oropharynx in preparation for awake endotracheal intubation. A new multiwavelength pulse oximeter, the Masimo Rad-57, detected this methemoglobinemia an hour before it was confirmed by laboratory CO-oximetry. The Rad-57 monitored the patient's methemoglobin levels during diagnosis and treatment with methylene blue, and the values it provided (as high as 33%) were very close to those of the laboratory CO-oximeter. The new pulse oximeter gave continuous readings of methemoglobin level at the bedside, whereas the laboratory values were delayed by up to an hour. This case demonstrates the clinical application of a multiwavelength pulse oximeter in the diagnosis and treatment of a life-threatening dyshemoglobinemia.

Transcutaneous oxygen tension (PtcO2) is often used to monitor neonates and infants in special care units and the operating room. The transcutaneous index (TCI = PtcO2/arterial oxygen tension [PaO2]) is known to depend both on age and on cardiac index but is assumed to be independent of other physiologic variables. In this study we have shown that TCI also depends upon arterial carbon dioxide tension (PaCO2). Five young pigs were anesthetized and paralyzed and their lungs mechanically ventilated while they were monitored with PtcO2 electrodes and serial arterial blood gas analyses. For a 45 degrees C PtcO2 sensor, the mean TCI during normocapnia was 0.78, whereas during hyperventilation (PaCO2 = 20 mmHg) the mean TCI was reduced 65%, to 0.27. The corresponding TCI values for a 43 degrees C sensor were 0.33 and 0.065, representing an 80% decrease in TCI during hyperventilation. Hypoventilation had little effect upon TCI as long as hypoxemia was avoided. Twelve awake adult volunteers with radial artery cannulas were monitored with PtcO2 sensors at several body sites and two sensor temperatures. For a 44 degrees C sensor on the chest, the mean TCI decreased from 0.77 at normocapnia to 0.60 at a PaCO2 of 17 mmHg, a 22% change. For the same sensor on the foot, TCI decreased from 0.63 to 0.32, a 49% change. For a 42 degrees C sensor under the same conditions, the corresponding TCI decreases were 51 and 64%. Six of the volunteers were also monitored with laser-Doppler skin blood flow probes located on the chest, hand, and foot.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent advances in pulse oximetry have made it possible to noninvasively measure total hemoglobin, as well as the two most common dyshemoglobins. This review will trace the development and clinical application of multiwavelength pulse oximetry.Until now, commercially produced pulse oximeters have utilized two wavelengths of light and could measure only the ratio of oxyhemoglobin to total hemoglobin, displayed as SpO2. Pulse oximeters using up to 12 light wavelengths have recently been developed by Masimo Corp. (Irvine, California, USA). These new 'Rainbow Pulse CO-oximeter' instruments can estimate blood levels of carboxyhemoglobin, methemoglobin, and total hemoglobin (SpHb), as well as the conventional SpO2 value. The accuracy of these new measurements has been studied in human volunteers and clinical trials. Some interesting case reports have documented the use of this new technology in diagnosis and treatment.The development of multiwavelength pulse oximeters, which can measure total hemoglobin as well as dyshemoglobins, should result in improved patient care.

Practice Advisory for the Prevention and Management of Operating Room Fires: An Updated Report by the American Society of Anesthesiologists Task Force on Operating Room Fires Jeffrey Apfelbaum;Robert Caplan;Steven Barker;Richard Connis;Charles Cowles;Jan Ehrenwerth;David Nickinovich;Donna Pritchard;David Roberson;Robert Caplan;Steven Barker;Richard Connis;Charles Cowles;Albert de Richemond;Jan Ehrenwerth;David Nickinovich;Donna Pritchard;David Roberson;Gerald Wolf; Anesthesiology

A new eight-wavelength pulse oximeter is designed to measure methemoglobin and carboxyhemoglobin, in addition to the usual measurements of hemoglobin oxygen saturation and pulse rate. This study examines this device's ability to measure dyshemoglobins in human volunteers in whom controlled levels of methemoglobin and carboxyhemoglobin are induced.Ten volunteers breathed 500 ppm carbon monoxide until their carboxyhemoglobin levels reached 15%, and 10 different volunteers received intravenous sodium nitrite, 300 mg, to induce methemoglobin. All were instrumented with arterial cannulas and six Masimo Rad-57 (Masimo Inc., Irvine, CA) pulse oximeter sensors. Arterial blood was analyzed by three laboratory CO-oximeters, and the resulting carboxyhemoglobin and methemoglobin measurements were compared with the corresponding pulse oximeter readings.The Rad-57 measured carboxyhemoglobin with an uncertainty of +/-2% within the range of 0-15%, and it measured methemoglobin with an uncertainty of 0.5% within the range of 0-12%.The Masimo Rad-57 is the first commercially available pulse oximeter that can measure methemoglobin and carboxyhemoglobin, and it therefore represents an expansion of our oxygenation monitoring capability.

Productivity measurements based on "per operating room (OR) site" and "per case" are not influenced by staffing ratios and have permitted meaningful comparisons among small samples of both academic and private-practice anesthesiology groups. These comparisons have suggested that a larger sample would allow for clinical groups to be compared using a number of different variables (including type of hospital, number of OR sites, type of surgical staff, or other organizational characteristics), which may permit more focused benchmarking. In this study, we used such grouping variables to compare clinical productivity in a broad survey of academic anesthesiology programs. Descriptive, billing, and staffing data were collected for 1 fiscal or calendar year from 37 academic anesthesiology departments representing 58 hospitals. Descriptive data included types of surgical staff (e.g., academic versus private practice) and hospital centers (e.g., academic medical centers and ambulatory surgical centers [ASCs]). Billing and staffing data included total number of cases performed, total American Society of Anesthesiologists units (tASA) billed, total time units billed (15-min units), and daily number of anesthetizing sites staffed (OR sites). Measurements of total productivity (tASA/OR site), billed hours per OR site per day (h/OR/d), surgical duration (h/case), hourly billing productivity (tASA/h), and base units/case were compared. These comparisons were made according to type of hospital, number of OR sites, and type of surgical staff. The ASCs had significantly less tASA/OR site, fewer h/OR/d, and less h/case than non-ASC hospitals. Community hospitals had significantly less h/OR/d and h/case than academic medical centers and indigent hospitals and a larger percentage of private-practice or mixed surgical staff. Academic staffs had significantly less tASA/h and significantly more h/case. tASA/h correlated highly with h/case (r = -0.68). This study showed that the hospitals at which academic anesthesiology groups provide care are not all the same from a clinical productivity perspective. By grouping based on type of hospital, number of OR sites, and type of surgical staff, academic anesthesiology departments (and hospitals) can be better compared by using clinical productivity measurements based on "per OR site" and "per case" measurements (tASA/OR, billed h/OR/d, h/case, tASA/h, and base/case).Organizational factors, including type of hospital, number of operating rooms, and type of surgical staff, influence the clinical productivity of academic anesthesiology departments. Reporting quartile data by focused grouping variables allows anesthesiology groups to compare their clinical productivity with groups practicing in similar clinical settings.

The results of study of a three-component (pH, PaCO2, PaO2) intra-arterial optode in patients undergoing surgical procedures are presented. Twenty-five surgical patients who required radial artery cannulation took part in this study. In each patient, the fiber-optic sensor (0.63 mm in diameter) was inserted into the arterial cannula. Results for the different cannula sizes are analyzed separately. A scatter plot of PoO2 versus PaO2 showing all data from the 18-gauge cannula patients and statistics for the three blood-gas variables and the two cannula sizes are presented and discussed. >

Several pulse oximeter manufacturers have recently developed instruments that are claimed to be resistant to the effects of patient motion. We performed a laboratory volunteer experiment to compare the performances of several of these instruments, as well as some older models, during combinations of motion and hypoxemia. Twenty oximeters were studied. A motorized table produced different hand motions, and each motion was studied during both room air breathing and hypoxemia. Pulse oximeters on the nonmoving hand were used to provide control measurements for comparison. The Masimo SET((R)) pulse oximeter exhibited the best overall performance, with a performance index (percentage of time in which the SpO(2) reading is within 7% of control value) of 94%. The Agilent Viridia 24C was next, with an 84% index, followed by the Agilent CMS (80%), the Datex-Ohmeda 3740 (80%), and the Nellcor N-395 (69%). For comparison with older oximeter technology, the Criticare 5040 had an index of 28%. Recent technology changes have significantly improved pulse oximeter performance during motion artifact, with the Masimo oximeter leading the way. IMPLICATIONS. New improvements in pulse oximeter technology have resulted in significantly better accuracy and reliability during patient motion. The Masimo pulse oximeter demonstrated the best performance of the 20 instruments tested.

In July, 1998 a fire occurred in an operating room (OR) at the University Medical Center in Tucson, AZ. A patient was burned on the face, neck, and shoulders by the fire, which started during cranial burr-hole placement under monitored anesthesia care. This paper describes the actual case in some detail. The incident was simulated as accurately as possible in a laboratory experiment, in an attempt to determine specific risk factors for this event. The experiment found that a specific combination of factors was required to produce a fire similar in appearance to the one in the OR. The risk factors determined in these experiments are discussed in the context of previous reports of OR fires. Although other reports demonstrate some common characteristics of these events, the fire at the University Medical Center appears to be unique within the literature regarding the specific chain of events that led up to it.A patient was seriously burned in a fire that occurred during surgery. We performed laboratory experiments to re-create the fire, and found some of the key factors that led to this event.

demonstrates that even today, theoperating room (OR) is not always a safe workingenvironment. Despite years of education on electricalsafety, combined with policies and precautions dictated bynational watchdog agencies such as the National FirePrevention Agency, a nurse sustained a serious, life-threatening electrical shock while performing her duties inthe OR. How could this happen, given our advancedunderstanding of both the physics and hazards of electric-ity? To understand and learn from this important casereport, we begin with a brief review of some relevantelectrical safety principles.Electricity can stimulate muscle cells to contract, and canthus be used therapeutically in devices such as pacemakersor defibrillators. Electrical current can also trigger grandmal seizures, and this effect is used beneficially in electro-convulsive therapy. However, contact with a large electri-cal current, whether alternating current (AC) or directcurrent, can lead to injury or death.Utility companies supply electrical energy in the form ofAC of 120 or 230 V at a frequency of 60 Hz (50 Hz in Europe).The60Hzreferstothenumberoftimesthatthecurrentcyclesper second. A typical power cord consists of two conductors.One designated as “hot” carries the current to the load; theother is neutral or “ground” and it returns the current to thesource. The root mean square potential difference betweenthe two is 120 V.To receive a shock, one must contact an electrical circuit attwo points, and there must be a potential difference thatcauses current to flow between those points. When an indi-vidual contacts a source of electricity, damage usually occursin one of two ways. First, the electrical current can disrupt thenormal electrical function of cells. Depending on its magni-tude, the current can contract muscles, paralyze respiration,cause seizures, or lead to ventricular fibrillation. The secondmechanism involves the dissipation of electrical energythroughout the tissues. An electrical current passingthrough any resistance increases the temperature of thatsubstance. The power dissipated as heat equals the squareof the current multiplied by the resistance (

Summary: Adverse neurological events during hypoxic episodes in high-risk patients or in patients not thought to be at risk while undergoing procedures increase morbidity and mortality. The ability to reliably monitor cerebral oxygenation could serve as an indicator for the need of therapeutic intervention and it's overall effect. This study was designed to verify the reliability of the only commercially available continuous noninvasive monitor, the INVOS 3100 (Somanetics Corp., Troy, MI), in subjects with varying levels of hypoxemia. Six adult volunteer subjects were enrolled. After placement of electrocardiogram (EKG), noninvasive blood pressure (NIBP), pulse oximeter (SpO2), cerebral oximeter (rSO2), a 20 g radial artery catheter, and a 4 F oximetric jugular bulb catheter, the subjects were given hypoxic mixtures to breathe to varying levels of desaturation. Arterial and mixed venous blood was drawn for blood-gas analysis at each level of O2 saturation. The cerebral hemoglobin saturation value from the cerebral oximeter was compared to the combined brain saturation using the formula: estimated field saturation between the light source and the detector (fSO2) = 0.25 × the arterial oxygen saturation (SaO2) + 0.75 × the jugular bulb venous oxygen saturation (SjvO2), (fSO2 = 0.25 SaO2 + 0.75 SjvO2). Statistical analysis demonstrated a correlation of 0.67 between rSO2 and fSO2 and a bias of -3.1% with a precision of 12.1%. Minimal bias of 0.38% and precision of 6.22% were calculated for transitional error. We concluded from the study that rSO2 may serve as a reliable indicator of changes in brain oxygenation induced by hypoxemia.

ECAUSE OF THE possibility of hypoxemia and hypoventilation during one-lung anesthesia, an accurate method of continuously monitoring both oxygenation and ventilation would be useful. Arterial blood gas (ABG) sampling is intermittent, expensive, and may result in delays in recognizing hypoxia, hypercarbia, and acidosis. Transcutaneous oxygen tension measurement and pulse oximetry have been recommended during one-lung ventilation (OLV), but both techniques have limitations and neither monitors ventilation.‘” The fiberoptic intraarterial optode makes use of the phenomenon of fluorescence quenching to determine blood gases and pH? The three-component optode (Cardiovascular Devices, Inc, Irvine, CA) is easily inserted through an 18-gauge radial artery catheter and allows continuous arterial pressure monitoring as well as access for blood sampling. The optode technology has also been applied to continuous blood gas monitoring in the extracorporeal circuit during cardiac surgery.6Z7 A case of OLV using continuous intraarterial optode measurement of pHa, PaOZ, and PaCO, is reported.

To compare pulse oximeter performance during induced hypoxemia.Prospective investigation in human volunteers.Laboratory facility at a university medical center.8 unanesthetized, healthy ASA physical status I volunteers.We evaluated the accuracy and response times of seven popular pulse oximeters during induced hypoxemia. Arterial blood fractional oxygen saturation (SaO2) measurements were performed simultaneously and considered a gold standard.All oximeters were accurate (+/-2%) while subjects were breathing room air. During maximal hypoxemia (induced by breathing a FIO2 = 10% in nitrogen), large differences were noted between oxygen saturation as measured by pulse oximetry (SpO2) and SaO2 values, with pulse oximeters consistently underreporting SpO2 when actual SaO2 values were 75% or less. The Ohmeda 3740 (Ohmeda, Boulder, CO) using an ear probe was the first to detect desaturation (change in SpO23%) in 4 of 8 subjects (p0.05), and the Nellcor N200 reflectance oximeter (Nellcor, Inc., Pleasanton, CA) was first in 3 of 8 subjects (p0.05). During resaturation (after administering 100% oxygen), the Novametrix Oxypleth (Novametrix, Wallingford, CT) was significantly faster than other oximeters (p0.05) to return to baseline (SpO2 = 98%).Most models of oximeters tested performed well when hemoglobin oxygen saturation was high, but all were inaccurate when SaO2 was approximately 75%. During induced hypoxemia, there were significant differences in the response times of oximeters tested, with no model demonstrably superior to others in all measures of performance.

Study Objective: To determine the incidence of new episodes of myocardial ischemia in patients undergoing transurethral resection of the prostate (TURP). Design: Prospective, nonrandomized study. Setting: Veterans Administration medical center. Patients: 39 patients undergoing elective TURP Interventions: None. Measurements and Main Results: Myocardial ischemia was detected with a 3-channel ambulatory ECG recorded. The ambulatory ECG recorder was applied preoperatively and removed when the patient left the recovery room. New myocardial ischemia was defined as a 1 mm or greater ST depression or a 2 mm or greater ST elevation from baseline, lasting for 1 minute or longer in at least one lead at the J point plus 60 msec unless this point fell within the T wave, in which case the J point 40 msec or greater was used. ST changes consistent with myocardial ischemia were confirmed by a cardiologist blinded to the patient's clinical course. Seven of 39 TURP patients (18%) had ST segment changes indicative of new myocardial ischemia. These seven patients had more prostate tissue resected and more blood loss than the 32 patients who did not have any myocardial ischemia (p Conclusions: Patients undergoing TURP have an 18% incidence of myocardial ischemia. Patients undergoing TURP with more prostate tissue resected and greater blood loss are at increased risk for perioperative myocardial ischemia.

Background Pulse oximetry is considered a standard of care in both the operating room and the postanesthetic care unit, and it is widely used in all critical care settings. Pulse oximeters may fail to provide valid pulse oximetry data in various situations that produce low signal-to-noise ratio. Motion artifact is a common cause of oximeter failure and loss of accuracy. This study compares the accuracy and data dropout rates of three current pulse oximeters during standardized motion in healthy volunteers. Methods Ten healthy volunteers were monitored by three different pulse oximeters: Nellcor N-200, Nellcor N-3000, and Masimo SET (prototype). Sensors were placed on digits 2, 3, and 4 of the test hand, which was strapped to a mechanical motion table. The opposite hand was used as a stationary control and was monitored with the same pulse oximeters and an arterial cannula. Arterial oxygen saturation rate varied from 100% to 75% by changing the inspired oxygen concentration. While pulse oximetry was both constant and changing, the oximeter sensors were connected before and during motion. Oximeter errors and dropout rates were digitally recorded continuously during each experiment. Results If the oximeter was functioning before motion began, the following are the percentages of time when the instrument displayed a pulse oximetry value within 7% of control: N-200 = 76%, N-3000 = 87%, and Masimo = 99%. When the oximeter sensor was connected after the beginning of motion, the values were N-200 = 68%, N-3000 = 47%, and Masimo = 97%. If the alarm threshold was chosen as pulse oximetry less than 90%, then the positive predictive values (true alarms/ total alarms) are N-200 = 73%, N-3000 = 81%, and Masimo = 100%. In general, N-200 had the greatest pulse oximetry errors and N-3000 had the highest dropout rates. Conclusions The mechanical motions used in this study significantly affected oximeter function, particularly when the sensors were connected during motion, which requires signal acquisition during motion. The error and dropout rate performance of the Masimo was superior to that of the other two instruments during all test conditions. Masimo uses a new paradigm for oximeter signal processing, which appears to represent a significant advance in low signal-to-noise performance.

Objective. The pulmonary elimination of the volume of CO2 per breath (VCO2/br, integration of product of airway flow ( $$\dot V$$ ) and PCO2 over a single breath) is a sensitive monitor of cardio-pulmonary function and tissue metabolism. Negligible inspired PCO2 results when the capnometry sampling site (SS) is positioned at the entry of the inspiratory limb to the airway circuit. In this study, we test the hypothesis that moving SS lungward will result in significant inspired CO2 (VCO2[I]), that needs to be excluded from VCO2/br.Methods. We ventilated a mechanical lung simulator with tidal volume (VT) of 800 mL at 10 breaths/min. CO2 production, generated by burning butane in a separate chamber, was delivered to the lung. Airway $$\dot V$$ and PCO2 were measured (Capnomac Ultima, Datex), digitized (100 Hz for 60 s), and stored by microcomputer. Then, computer algorithms corrected for phase diferences between $$\dot V$$ and PCO2 and calculated expired and inspired VCO2 (VCO2[E] and VCO2[I]) for each breath, whose difference equalled overall VCO2/br. The lung and Y-adapter (where the inspiratory and expiratory limbs of the circuit joined) were connected by the SS and a connecting tube in varying order.Results. During ventilation of the lung model (VT = 800 ml) with SS adjacent to the inspiratory limb, VCO2[E] was 16.8± 0.4 ml and VCO2[I] was 1.1 ±0.1 ml, resulting in overall VCO2/br (VCO2[E] —VCO2[I]) of 15.7 ± 0.4 ml. If VCO2[I] was ignored in the determination of VCO2/br, then the %error that VCO2[E] overestimated VCO2/br was 7.2± 0.3%. This %error significantly increased (p < 0.05, Student's t-test) when VT was decreased to 500 mL (%error = 12.4 ± 0.8%) or when SS was moved to the lungward side of a 60 mL connecting tube (VCO2[I] = 2.8 ± 0.2, %error = 18.2 ± 1.6) or a 140 mL tube (VCO2[I] = 5.9±03 mL, %error = 37.5±3.3).Conclusions. When the SS was moved lungward from the inspiratory limb, instrumental dead space (VDINSTR) increased and, at end-expiration, contained exhaled CO2 from the previous breath. During the next inspiration, this CO2 was rebreathed relative to SS (i.e. VCO2[I]), and contributed to VCO2[E]. Thus, VCO2[E] overestimated VCO2/br (%error) by the amount of rebreathing, which was exacerbated by largerVDINSTR (increased VCO2[I]) or smaller VT (increased VCO2[I]-to-VCO2/br ratio).