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At least 217 records · Page 12Linked to original sources
PubMed2004

Dystocia in nulliparous patients monitored with fetal pulse oximetry.

OBJECTIVE: A critical analysis of the United States randomized controlled trial of fetal pulse oximetry concluded that nonreassuring fetal heart rate patterns used for study entry may have been a marker for dystocia. We prospectively studied nulliparous women in labor whose progress was monitored with fetal pulse oximetry to examine the relationship between nonreassuring fetal heart rate patterns and operative delivery for dystocia. STUDY DESIGN: A prospective nonrandomized observational cohort study compared two distinct classes of nonreassuring fetal heart rate patterns (class I: intermittent, mildly nonreassuring; class II: persistent, progressive, and moderate to severely nonreassuring) among nulliparous patients with the use of fetal pulse oximetry to confirm fetal well-being. Definitions of dystocia included the cessation of labor progress in the first (3 hours) or second (2 hours) stage of labor, despite adequate uterine activity that was assessed with an intrauterine pressure catheter. Independent review confirmed the classification of nonreassuring fetal heart rate patterns and study entry criteria. RESULTS: Two hundred seventy-four patients met study criteria and had sufficient information for fetal heart rate tracing interpretation. Two hundred thirty-seven patients (86.5%) were class II, and 37 patients (13.5%) were class I. The two classes of patients were comparable in a variety of obstetric, demographic, and perinatal variables. Twelve percent of all patients were delivered for nonreassuring fetal status. Significantly more class II patients (22%) were delivered by cesarean for dystocia than were class I patients (8%). Higher doses and a longer number of hours of oxytocin were required among class II patients. Significantly more occiput posterior positions were noted among all patients who underwent cesarean delivery for dystocia compared with other modes of delivery. CONCLUSION: Significantly nonreassuring fetal heart rate patterns predict cesarean delivery for dystocia among nulliparous patients with normally oxygenated fetuses in a setting of a standardized labor management protocol. This confirms the observations in the randomized controlled trial of fetal pulse oximetry in the United States and may provide insight into the treatment of nonprogressive labor in contemporary practice.

Cesarean Section↗
PubMed1997

Assessment of anastomotic reliability with pulse oximetry in graded intestinal ischemia: an experimental study in dogs.

BACKGROUND/PURPOSE: Pulse oximetry has been proposed as an appropriate and feasible technique in the assessment of intestinal ischemia in recent years. In this study the authors aimed to assess the reliability of anastomoses in the dog small intestine in which there is graded irreversible ischemia as measured by pulse oxymeter. METHODS: In a control group of four dogs, without any devascularization, three small bowel anastomoses were formed in each dog. The study group consisted of 12 dogs. In each animal three intestinal segments with different levels of ischemia were created by ligating the marginal vessels proximally and distally in sequence beginning from the midpoint of the segmental vascular arcade. Preanastomotic pulse oximeter readings between 80% and 90% were assigned to mild ischemia, 70% and 80% to moderate, and 60% and 70% to severe ischemia group. Pulse oximetry measurements were obtained from probes applied to the antimesenteric serosal surfaces at the midpoint of small intestinal segments. A total of 48 intestinal segments (12 nonischemic in the control group and 36 with three different levels of ischemia in the study group) were transected in the midpoint and anastomosed in double layers. Postanastomotic SaO2 values were also noted. The anastomoses were evaluated 48 hours later macroscopically if there was any leakage, and biopsy specimens were obtained for histopathologic ischemic gradings. All results were studied statistically. RESULTS: Histopathologic grades between each group were statistically different (P < .01 for each comparison) except for control and mild ischemia groups (P > .05), worsening as the level of ischemia increased. Pre- and postanastomotic pulse oximetry measurements correlated very well with the histological gradings (r = -0.90, P < .001 and r = -0.93, P < 0.001 respectively). Number of anastomotic leakages were none in control, one in mild, nine in moderate, and 12 (all of the anastomoses) in severe ischemia groups. In the moderate ischemia group with an average preanastomotic pulse reading of 76.75%, each of the leaking anastomoses had a postanastomotic pulse measurement of lower than 70%. The finding that the difference between histopathologic grades of control and mild ischemia groups with average preanastomotic pulse measurements of 96% and 85%, respectively is not statistically significant enables us to suggest that a saturation of at least 85% is necessary for a reliable anastomosis. CONCLUSION: These results suggest clearly that anastomotic reliability can be predicted objectively with pulse oximetry.

Anastomosis, Surgical↗
PubMed1997

The safety of fetal pulse oximetry in parturients requiring fetal scalp blood sampling.

OBJECTIVE: To determine whether maternal or fetal morbidity is increased in association with fetal pulse oximetry monitoring using an atraumatic intrapartum transcervical fetal oxisensor. METHODS: In a prospective cohort study from January 1993 to June 1996, 196 fetuses were monitored during the intrapartum period with a fetal oximetry sensor placed between the uterine wall and the presenting fetal part. The oxisensors were in position for a median duration of 134 minutes. A total of 101 monitored fetuses underwent intrapartum fetal scalp blood sampling because of nonreassuring heart rate tracings. For a control group, we selected all cases during the same period in which fetal blood sampling was performed in the intrapartum period (n = 949) without pulse oximetry monitoring. Data for maternal and fetal morbidity were evaluated and tested for significant differences by the Mann-Whitney U test. RESULTS: There was no significant difference in gestational age, birth weight, duration of labor, fetal outcome parameters, cesarean rate, operative vaginal deliveries, episiotomy rate, or perineal injuries between the study and control groups. Similarly, the percentages of neonatal intensive care unit admissions, neonatal resuscitations, and neonatal infections were not statistically different in the two groups. A rare complication in the group with pulse oximetry monitoring was a transient impression of the oxisensor probe on the fetal cheek. The rates of postpartum maternal infections, anemia, or secondary wound disruptions were identical in both groups. CONCLUSION: There was no increased fetal or maternal morbidity associated with the use of an atraumatic intrapartum fetal pulse oxisensor.

Female↗
PubMed1994

Knowledge about pulse oximetry among medical and nursing staff.

Although pulse oximeters are increasingly used to monitor patients on medical and surgical wards, staff seem to receive no specific training in the operation of these devices. We investigated the knowledge of junior doctors and nursing staff about pulse oximetry as used on seriously ill patients in a District General Hospital in Exeter, UK. 30 medical or surgical preregistration house officers or senior house officers and 30 staff nurses answered a structured questionnaire. Questions were asked about the theory behind pulse oximetry, factors affecting readings, "normal" values in various patients, values in hypothetical clinical situations, and what training subjects had received. Responses were scored against standard answers from reference texts. 97% of doctors and nurses did not understand how a pulse oximeter worked and were confused about factors influencing readings. Respondents gave a wide range of acceptable saturation values (eg, 90-100% for a fit adult), thus demonstrating poor understanding of physiological principles. There were serious errors made in evaluating saturation readings in hypothetical clinical situations. Only 1 doctor had received formal training in the use of pulse oximetry. Our survey revealed that junior doctors and staff nurses were untrained in pulse oximetry, lacked knowledge of basic principles, and made serious errors in interpretation of readings. Training is needed for staff who use pulse oximeters.

Adult↗
PubMed1997

Effect of oximetry error on the diagnostic value of the Qp/Qs ratio.

As a quantitative assessment of the magnitude of shunting, the ratio of pulmonary to systemic blood flow (Qp/Qs) plays an important role not only in the oximetric diagnosis of intracardiac and great-vessel shunts but also in the treatment of the patient. However, the oxygen saturation measurements used to compute the Qp/Qs ratio contain errors due to physiological variability and measurement error of the oximeter used to analyze the blood samples. We have developed a mathematical model to describe the variability that oximetry errors contribute to the uncertainty in the Qp/Qs ratio. Using this model, we compute the probability of making an inappropriate recommendation regarding corrective surgery when a particular value of the ratio is the criterion for surgery, e.g. a Qp/Qs ratio >2. This report also contains a spreadsheet that readers can use to analyze their own oximetry data by computing confidence intervals for the Qp/Qs ratio. The results presented here support the following conclusions. First, because the Qp/Qs ratio is calculated from saturation measurements at four different sites, oximetry errors make the Qp/Qs ratio less effective at detecting the presence of a shunt than the conventional step-up method that depends on samples from only two sites. Second, although oximetry errors are equally likely to cause the calculated Qp/Qs ratio to overestimate the true Qp/Qs ratio as to underestimate it, the overestimations on average have greater magnitudes than the underestimations. Third, in comparison with an oximeter that has 2.5% measurement error, using an oximeter with 1% or less error greatly reduces the uncertainty in the Qp/Qs ratio and thus increases the probability of reaching the right decision regarding corrective surgery. Fourth, the variability in apparent Qp/Qs ratios is also greatly diminished by taking multiple blood samples from each of the four requisite sites and averaging them before calculating the Qp/Qs ratio. Although increasing the number of blood samples from each site can compensate for the error of an oximeter, this approach can be impractical, particularly if the oximeter error is 2.5% or greater.

Coronary Circulation↗
PubMed1991

Impact of portable pulse oximetry on arterial blood gas test ordering in an urban emergency department.

STUDY OBJECTIVE: To determine the impact of portable pulse oximetry on physician use of arterial blood gas tests (ABGs) in an urban emergency department. DESIGN: Prospective, controlled clinical trial. SETTING: The ED of the Regional Medical Center at Memphis, a publicly subsidized, 450-bed, acute care hospital staffed by residents and faculty of the University of Tennessee, Memphis. TYPE OF PARTICIPANTS: Rotating housestaff treating adult ED patients with a wide variety of medical and surgical problems. INTERVENTION: Introduction of a portable pulse oximeter for noninvasive measurement of blood oxygenation. MEASUREMENTS: Rates of ABG test ordering, housestaff reason(s) for ordering an ABG, and the incidence of adverse clinical outcomes before and after introduction of portable pulse oximetry. MAIN RESULTS: A total of 20,120 patient visits occurred during the four-month study. Before oximeter introduction, emergency physicians ordered 699 ABGs, 63% of which were indicated by explicit criteria. After oximeter introduction, 440 ABGs were ordered (a 37% decrease). Almost all of this decrease was due to fewer ABGs ordered to assess oxygenation (260 before vs 75 after; chi 2, P less than .001). These reductions were not explained by differences in total patient visits or case mix. Physicians decreased ordering of indicated ABGs by almost as great an extent as they reduced ordering of unindicated tests, suggesting they did not consistently distinguish between the two. However, decreased testing did not result in any serious adverse outcomes, defined as unanticipated respiratory or cardiac arrest in the ED, unanticipated arrest on the floor within 24 hours of admission, or death within two days of hospital discharge. CONCLUSION: Portable pulse oximetry can provide a simple, noninvasive way to determine oxygen saturation in the ED. Routine use of portable pulse oximetry may substantially reduce rates of ABG testing and associated patient charges without adversely affecting the quality of emergency care.

Adult↗
PubMed1991

An evaluation of pulse oximetry in prehospital care.

STUDY OBJECTIVES: We performed this study to evaluate the accuracy of pulse oximetry oxygen saturation (SpO2) against direct measurements of arterial oxygen saturation (SaO2) in the field. DESIGN: Prospective, cross-sectional, paired measurements of SpO2 against SaO2. SETTING: This evaluation was done in the prehospital setting. INTERVENTIONS: A pulse oximeter with digital probe was used to measure SpO2 in 30 patients. Arterial blood gases were drawn in the field while the pulse oximeter was in use, and oxygen saturation (HbO2) was measured by CO-oximetry. MAIN RESULTS: There was no significant difference between SpO2 (94.6 +/- 5.4%) and HbO2 (94.9 +/- 5.1%) (P = .495, beta less than .2). There was a strong correlation between SpO2 and HbO2 (r = .898). The bias between SpO2 and HbO2 was -0.3, with a precision of 2.4. When SpO2 was 88% or more, HbO2 was 90% or more in every case. Mean carboxyhemoglobin was 1.3 +/- 0.9%, and mean methemoglobin was 0.9 +/- 0.3%. There was no significant difference between the pulse oximeter heart rate and the ECG heart rate (P = .223, beta less than .2). CONCLUSION: We conclude that pulse oximetry is sufficiently accurate to be useful in the field when SpO2 is more than 88%. It is potentially useful in patients with clinical signs of acute hypoxemia and in patients receiving interventions that may produce acute hypoxemia. Further work is needed to evaluate the accuracy of pulse oximetry in the settings of elevated carboxyhemoglobin, methemoglobin, and very low saturations.

Aged↗
PubMed1995

Contribution of routine pulse oximetry to evaluation and management of patients with respiratory illness in a pediatric emergency department.

STUDY OBJECTIVE: To determine whether routine pulse oximetry in a pediatric emergency department can be used to identify patients with a low oxygen saturation (SaO2) that is unexpected on the basis of clinical evaluation. DESIGN: Prospective comparison of blinded, clinical evaluation by physicians with subsequent pulse oximetry readings. SETTING: Pediatric ED in an urban, university medical center. PARTICIPANTS: A convenience sample of 368 patients presenting to the pediatric ED with respiratory illnesses. METHODS: The history, physical examination, pediatric ED management, and therapy were recorded. Based on clinical assessment, the physician was asked whether the patient had a low SaO2 (< or = 92%). Room-air pulse oximetry was then obtained, with subsequent treatment and management plans recorded. RESULTS: Clinical assessment had a sensitivity of 33%, specificity of 86%, negative predictive value of 85%, and positive predictive value of 35% for detecting children with low SaO2. Unexpected low SaO2 usually led to a change in patient management or disposition. CONCLUSION: Clinical evaluation in a pediatric ED does not screen adequately for the detection of hypoxemia and should be supplemented by routine pulse oximetry in all patients with respiratory findings.

Child↗
PubMed2003

[Sequential use of nocturnal pulse oximetry and respiratory polygraphy (AutoSet) for diagnosing sleep apnea/hypopnea syndrome in high risk patients].

OBJECTIVE: To construct an algorithm for the diagnosis of sleep apnea/hypopnea syndrome (SAHS) based on the optimized sequential use of nocturnal pulse oximetry and respiratory polygraphy (AutoSet, AS) in patients suspected of SAHS. METHODS: Simultaneous performance of pulse oximetry and AS in 145 patients highly suspected of SAHS (at least two of the following signs or symptoms: chronic snoring, observations of repeated apneic events, and abnormal daytime drowsiness). SAHS was diagnosed when the apnea/hypopnea index (AHI) was greater than or equal to 10, based on AS findings. The diagnostic algorithm was obtained by calculating the prevalence of SAHS, calculating the best diagnostic cutoff point for a desaturation index greater than or equal to 4% (ID4%) based on the AHI; analyzing the positive predictive value (PPV) and negative predictive value (NPV) for the cutoff and the correlation and agreement between ID4% and the AHI depending on the presence and severity of SAHS. RESULTS: The overall prevalence of SAHS was 83.4%. The best cutoff point was obtained using ID4% greater than or equal to 10 (sensitivity 82%; specificity 83%). The PPV and NPV for the prevalence calculated were 0.95 and 0.29, respectively. The correlation between ID4% and AHI was 0.84; overall agreement was 0.93. For patients who did not have SAHS, the PPV was 0.49, and the NPV was 0.35; both gradually increased in cases of mild, moderate and severe SAHS (to 0.90 and 0.95, respectively, for severe SAHS). Using these data we created a diagnostic algorithm according to which an ID4% greater than or equal to 30 for nocturnal pulse oximetry (sensitivity 72%, specificity 100%) would indicate that AS testing would be unnecessary. An ID4% less than 30, on the other hand, would lead to further testing (AS, or polysomnography in the event of a negative AS), based on the high prevalence of SAHS in our series. CONCLUSIONS: The sequential use of nocturnal pulse oximetry and AS allows substantial savings of polysomnographic testing in groups at high risk of SAHS.

Airway Obstruction↗
PubMed1998

Effect of routine pulse oximetry measurements on ED triage classification.

Pulse oximetry is commonly used to rapidly determine oxygen saturation and is incorporated in emergency triage as a screening for potential cardiopulmonary complications. This study examined the effect of routine pulse oximetry measurements on emergency department (ED) triage classification. Using a portable pulse oximeter, oxygen saturation of 1,235 adults presenting to a university-based, urban ED was obtained and each patient was assigned a classification of severity based on a standard 1-to-4 scale before and after the measurement. According to data obtained, a small but statistically significant group (2.8%) benefitted from the routine use of pulse oximetry in an emergency triage system and only 40% of these patients required admission or extended care. Although this group is small in number, the potential consequences of missing a hypoxic condition could be devastating for the individual patient. Since pulse oximetry is presently an inexpensive technology, it would seem to be a worthwhile screening tool for emergency triage.

Adult↗
PubMed1999

Pulse oximetry: principles and limitations.

The pulse oximeter has become an essential tool in the modern practice of emergency medicine. However, despite the reliance placed on the information this monitor offers, the underlying principles and associated limitations of pulse oximetry are poorly understood by medical practitioners. This article reviews the principles of pulse oximetry, with an eye toward recognizing the limitations of this tool. Among these are performance limitations in the settings of carboxyhemoglobinemia, methemoglobinemia, motion artifact, hypotension, vasoconstriction, and anemia. The accuracy of pulse oximetry is discussed in light of these factors, with further discussion of applications for pulse oximetry in emergency medicine, including both oximetric and plethysmographic operation. The pulse oximeter is an invaluable instrument for emergency medicine practice, but as with any test the data it offers must be critically appraised for proper interpretation and utilization.

Artifacts↗
PubMed1987

[The value of monitoring arterial oxygenation saturation by pulse oximetry in neuroleptanalgesia].

Anaesthesia can induce hypoxaemia. Pulse oximetry gives continuous non invasive monitoring of arterial oxygen saturation. No arterial puncture is needed. Ninety-four patients were monitored by pulse oximetry during neuroleptanalgesia for colonoscopy. Eighteen patients showed desaturation episodes of less than 90%, eight linked to opioid-induced respiratory depression. In all patients, pulse oximetry gave clinicians an immediate awareness of the incident. Treatment was facilitated. Pulse oximetry made anaesthesia safer.

Blood Gas Monitoring, Transcutaneous↗
PubMed1996

Fetal pulse oximetry.

Fetal pulse oximetry provides a tool for the surveillance of the fetus at risk of hypoxia. The experience of 150 deliveries monitored by pulse oximetry and the analysis of data may allow preliminary recommendations for clinical use in cases of suspected fetal hypoxia based on a suspicious FHR. In most cases, saturation values above 33% suggest fetal well-being. Further fetal evaluation, for example by fetal blood samples or other means, is necessary to assess alterations of FHR pattern or decreases in saturation values. Pulse oximetry may allow a differentiation between cases that need further evaluation, such as scalp blood sampling, and those which do not. The number of repeated assessments may be reduced as long as the oxygen saturation and FHR pattern do not worsen. The effect of therapeutic measures on fetal oxygenation can be directly observed. The positive preliminary experiences with fetal pulse oximetry predominate even if high expectations of easy detection of fetal hypoxia have so far not been fulfilled.

Bias↗
PubMed2002

Reusable sensors in intrapartum foetal reflection pulse oximetry.

OBJECTIVES: To evaluate the accuracy of intrapartum foetal pulse oximetry (SO(2POX)) using reusable sensors and the effect of a sensor performance test on data quality. Furthermore, to assess the sensor-related costs by using reusable sensors and sensor performance test. METHODS: 36 reusable sensors were used for SO(2POX) during labour of 289 term foetuses. A sensor performance test device assessing the emitter and receiver capability and the firmness of attachment of the sensors had been developed and used in the last 134 measurements before each resterilisation. Oxygen saturation (SaO(2)) at birth was measured spectrophotometrically after cord blood sampling. The accuracy of SO(2POX) was evaluated by analysing its relationship to SaO(2). The valid SO(2POX) data, as confirmed by subsequent sensor test in the second group, was considered comparable with those with single sensor use. Sensor-related average cost (sensors, test device and sterilisation) of such measurements was compared with that of single sensor use. RESULTS: Eight sensors failed performance test despite valid pulse oximetry signal output during their last measurements. There were significant overall linear correlations between SO(2POX) and SaO(2) (r=0.45, P<0.0001). Separate analyses of regression in the group without sensor performance testing showed an r(2) of 0.41, whereas in the group with subsequent sensor performance testing, the r(2) was 0.52 (P<0.05). By reusing the sensors, the sensor-related cost per valid measurement was $18.9 and 71% lower compared to single use of sensors ($65). CONCLUSIONS: Pulse oximetry may reflect fetal oxygen saturation. Data quality may be compromised by insufficient sensor performance, even though the reflection signal quality is acceptable. If sensor performance is tested before each measurement, reusable sensors may reduce the costs of fetal pulse oximetry.

Equipment Reuse↗
PubMedDate not supplied

Prehospital use of pulse oximetry in rotary-wing aircraft.

A prospective study of 200 patients was conducted to evaluate the use of pulse oximetry as an adjunct to clinical monitoring of clinically ill patients transported by rotary-wing aircraft with non-pressurized cabins. Thirty-four subjects (17%) were found to have significant hemoglobin desaturation of less than 90%, as defined by pulse oximetry (SpO 2). Data were recorded continuously for later review. Desaturation often was noted prior to alterations in vital signs or clinical appearance. In 32 of 34 hypoxemic subjects (94%), therapeutic interventions corrected the low SpO 2. The use of pulse oximetry permitted measures for cardiorespiratory support to be instituted and assessed more rapidly than otherwise would have been possible. The availability of a continuous record of SpO 2 facilitated detailed review of case management. It is concluded that the use of pulse oximetry is a practical and valuable adjunct for monitoring critically ill patients transported by rotary-wing aircraft.

Adolescent↗
PubMed1998

Influence of pulse oximetry and capnography on time to diagnosis of critical incidents in anesthesia: a pilot study using a full-scale patient simulator.

OBJECTIVE: Many studies (outcome, epidemiological) have tested the hypothesis that pulse oximetry and capnography affect the outcome of anesthetic care. Uncontrollable variables in clinical studies make it difficult to generate statistically conclusive data. In the present study, we eliminated the variability among patients and operative procedures by using a full-scale patient simulator. We tested the hypothesis that pulse oximetry and capnography shorten the time to diagnosis of critical incidents. METHODS: A simulator was programmed to represent a patient undergoing medullary nailing of a fractured femur under general anesthesia and suffering either malignant hyperthermia, a pneumothorax, a pulmonary embolism or an anoxic oxygen supply. One hundred thirteen anesthesiologists were randomly assigned to one of two groups of equal size, one with access to pulse oximetry and capnography data and the other without. Each anesthesiologist was further randomized to one of the four critical incidents. Each anesthetic procedure was videotaped. The time to correct diagnosis was measured and analyzed. RESULTS: Based on analysis of 91 of the subjects, time to diagnosis was significantly shorter (median of 432 s vs. >480 s) for the anoxic oxygen supply scenario (p = 0.019) with pulse oximetry and capnography than without. No statistical difference in time to diagnosis was obtained between groups for the other three critical incidents. CONCLUSIONS: Simulation may offer new approaches to the study of monitoring technology. However, the limitations of current simulators and the resources required to perform simulator-based research are impediments to wide-spread use of this tool.

Anesthesia, General↗
PubMed1998

Reflectance pulse oximetry--principles and obstetric application in the Zurich system.

Transmission and reflectance are the two main modes of pulse oximetry. In obstetrics, due to the absence of a transilluminable fetal part for transmission oximetry, the only feasible option is the reflectance mode, in which sensor and detector are located on the same surface of the body part. However, none of the reflectance pulse oximeters developed for intrapartum use are fully satisfactory, as indicated by the fact that none have entered routine use. We have designed, developed, constructed and tested a reflectance pulse oximeter with the possibility to adjust the electronic circuits and signal processing in order to determine the effects of various parameters on signal amplitude and wave-form and to optimize the sensitivity and spatial arrangement of the optical elements. Following an explanation of the principles of reflectance pulse oximetry, we report our experience with the design, development, construction and field-testing of an in-house reflectance pulse oximetry system for obstetric application.

Adult↗
PubMed2004

The influence of larger subcutaneous blood vessels on pulse oximetry.

OBJECTIVE: Recent studies have renewed interest in reflectance pulse oximetry, specifically for monitoring the patient's forehead. Blood circulation on the forehead immediately above the eyebrow is fed by arteries that branch from the internal carotid artery and lack the vasoconstrictor response present in more peripheral regions. Some investigators question, however, the reliability of monitoring SpO2 on the forehead due to prior reported inaccurate readings with reflectance sensors. The present study evaluates pulse oximetry accuracy when reflectance sensors are placed over potentially pulsing or moving larger arterial vessels, or over more homogeneous microvasculature devoid of larger subcutaneous vessels. METHODS. Ten healthy adult volunteers were fitted with reflectance pulse oximetry sensors and exposed to a controlled desaturation to 70%. Sensors were placed immediately above the left and right eyebrows as well as over the temple. Additionally, numerical modeling was used to simulate light signals and photon migration through a homogeneous tissue bed with an added static or dynamic artery. RESULTS: Sensors placed above the eyebrows tracked one another with significantly better accuracy than when comparing temple with the brow placement (RMS of the Differences = 1.12% vs. 4.24%, respectively). Photon migration simulations indicate that the detected light bypasses the interior of larger vessels, while vessel presence affects the red and IR light pulse amplitudes independent of SaO2. CONCLUSIONS: Placement of reflectance pulse oximetry sensors directly over larger cardio-synchronously pulsing or moving vasculature can significantly degrade SpO2 reading accuracy. Reflectance sensors placed low on the forehead directly over the eyebrow and slightly lateral to the iris appear to avoid such vasculature and provide consistent and accurate estimates of SaO2.

Adult↗