Forehead is as sensitive as finger pulse oximetry during general anesthesia

A prospective study for an alternative probe site for pulse oximetry measurement in male patients with severe burn trauma: penile shaf

BACKGROUND

Authors widely use pulse oximetry in clinical monitoring of heart rate (HR) and peripheral oxygen saturation (SpO2) by attachment to the fingers; however, there can be a need for an alternative attachment site, especially for burned patients. We investigate the availability of a pulse oximeter probe attached to the penile shaft as an alternative site in pediatric male patients if all extremities became unavailable for pulse oximetry measurement due to severe burn and/or trauma.

METHODS

We designed a prospective comparative study in a training and research hospital. After local ethical committee approval, pediatric male cases eligible for penile and extremity pulse measurements were evaluated during general anesthesia for medical dressing and/or grafting due to severe burns. One probe was attached to the fingers of the unburned extremity, and the other was to the penile shaft. Furthermore, we recorded SpO2and HR values at 5-min intervals; 0th (baseline), 5th, 10th and 15th minutes. We compared HR and SpO2values measured by the finger probe with those measured by the penile probe.

RESULTS

Data of 51 patients (median age, 2.9 years (interquartile range, 2.0-5.0 years)) in whom the duration of dressing was at least 15min were analyzed. There was no significant difference either in comparisons of hemodynamic measurements (HR and SpO2 ) obtainedby finger probe and by a penile probe for each measurement time. The Bland-Altman plot analysis reveals agreement for penile and finger probes with a mean bias value between 0.20 and 0.37 on HR and between 0.43 and -0.20 on SpO2.

DISCUSSION

This clinical trial demonstrated that pulse oximetry measurement under nonhypoxic conditions we could perform confidently using penile probes in pediatric male patients whose extremities are unavailable for measurement.

Enabling Continuous Wearable Reflectance Pulse Oximetry at the Sternum

In light of the recent Coronavirus disease (COVID-19) pandemic, peripheral oxygen saturation (SpO₂) has shown to be amongst the vital signs most indicative of deterioration in persons with COVID-19. To allow for the continuous monitoring of SpO₂, we attempted to demonstrate accurate SpO₂ estimation using our custom chest-based wearable patch biosensor, capable of measuring electrocardiogram (ECG) and photoplethysmogram (PPG) signals with high fidelity. Through a breath-hold protocol, we collected physiological data with a wide dynamic range of SpO₂ from 20 subjects. The ratio of ratios (R) used in pulse oximetry to estimate SpO₂ was robustly extracted from the red and infrared PPG signals during the breath-hold segments using novel feature extraction and PPG_green-based outlier rejection algorithms. Through subject independent training, we achieved a low root-mean-square error (RMSE) of 2.64 ± 1.14% and a Pearson correlation coefficient (PCC) of 0.89. With subject-specific calibration, we further reduced the RMSE to 2.27 ± 0.76% and increased the PCC to 0.91. In addition, we showed that calibration is more efficiently accomplished by standardizing and focusing on the duration of breath-hold rather than the resulting range in SpO₂. The accurate SpO₂ estimation provided by our custom biosensor and the algorithms provide research opportunities for a wide range of disease and wellness monitoring applications.

Comparison of Transmittance and Reflectance Pulse Oximetry in Anesthetized Dogs

Objectives: The tongue is the standard site for placement of a pulse oximeter probe but is difficult to access during certain procedures such as dental and ophthalmic procedures and computerized tomography of the head. The aim of this study was to evaluate the performance of a new-generation reflectance pulse oximeter using the tail and tibia as sites for probe attachment.

Materials and Methods: A total of 100 client-owned dogs that underwent anesthesia for various reasons were premedicated with butorphanol (n = 50; 0.2 mg/kg; group BUT) or butorphanol and dexmedetomidine (n = 50; 5 μg/kg; group DEX), administered intravenously. Anesthesia was induced with propofol and maintained with sevoflurane. A transmittance pulse oximeter probe was placed on the tongue and served as the reference standard. A reflectance probe was randomly placed on the tail base or the proximal tibia, and the position changed after testing. Signals from three consecutive measurements were obtained at each position. Failure was defined as “no signal,” “low signal,” or a pulse difference >10/min compared with the ECG heart rate. Data were analyzed using chi-square test, Wilcoxon matched-pair signed-rank test, and Bland-Altman analysis. P < 0.05 was considered significant.

Results: In both groups (BUT and DEX), failure rate was higher when the tibia and tail were used as probe sites compared with the tongue. In both groups, the failure rate was higher for the tibia than for the tail. Dexmedetomidine-induced vasoconstriction increased failure rate at all probe positions.

Clinical Significance: The tail base, but not the tibia, is an acceptable position for reflectance pulse oximeter probes in dogs. The tongue remains the probe site of choice, if accessible.

First Evaluation of a Newly Constructed Underwater Pulse Oximeter for Use in Breath-Holding Activities

Studying risk factors in freediving, such as hypoxic blackout, requires development of new methods to enable remote underwater monitoring of physiological variables. We aimed to construct and evaluate a new water- and pressure proof pulse oximeter for use in freediving research. The study consisted of three parts: (I) A submersible pulse oximeter (SUB) was developed on a ruggedized platform for recording of physiological parameters in challenging environments. Two MAX30102 sensors were used to record plethysmograms, and included red and infra-red emitters, diode drivers, photodiode, photodiode amplifier, analog to digital converter, and controller. (II) We equipped 20 volunteers with two transmission pulse oximeters (TPULS) and SUB to the fingers. Arterial oxygen saturation (SpO₂) and heart rate (HR) were recorded, while breathing room air (21% O₂) and subsequently a hypoxic gas (10.7% O₂) at rest in dry conditions. Bland-Altman analysis was used to evaluate bias and precision of SUB relative to SpO₂ values from TPULS. (III) Six freedivers were monitored with one TPULS and SUB placed at the forehead, during a maximal effort immersed static apnea. For dry baseline measurements (n = 20), SpO₂ bias ranged between −0.8 and −0.6%, precision between 1.0 and 1.5%; HR bias ranged between 1.1 and 1.0 bpm, precision between 1.4 and 1.9 bpm. For the hypoxic episode, SpO₂ bias ranged between −2.5 and −3.6%, precision between 3.6 and 3.7%; HR bias ranged between 1.4 and 1.9 bpm, precision between 2.0 and 2.1 bpm. Freedivers (n = 6) performed an apnea of 184 ± 53 s. Desaturation- and resaturation response time of SpO₂ was approximately 15 and 12 s shorter in SUB compared to TPULS, respectively. Lowest SpO₂ values were 76 ± 10% for TPULS and 74 ± 13% for SUB. HR traces for both pulse oximeters showed similar patterns. For static apneas, dropout rate was larger for SUB (18%) than for TPULS (<1%). SUB produced similar SpO₂ and HR values as TPULS, both during normoxic and hypoxic breathing (n = 20), and submersed static apneas (n = 6). SUB responds more quickly to changes in oxygen saturation when sensors were placed at the forehead. Further development of SUB is needed to limit signal loss, and its function should be tested at greater depth and lower saturation.

A comparison of finger and forehead pulse oximeters in heart failure patients during maximal exercise

BACKGROUND

Pulse oximeters, clinically used to measure oxygen saturation (SpO₂), rely on adequate perfusion of the tissues over which they are placed. Heart failure (HF) patients can have impaired peripheral perfusion which may compromise the accuracy of a peripherally placed pulse oximeter. This decrease in peripheral perfusion may be especially apparent during exercise. The objective of this study was to determine if pulse oximeter accuracy is dependent on location in heart failure patients during peak exercise.

METHODS

20 participants with HF (7F, age 64.±11 yr) and 9 participants with coronary artery disease as controls (CAD: 3F, age 66±5 yr) performed a maximal exertion treadmill exercise stress test while wearing both finger and forehead pulse oximeters.

RESULTS

At peak exercise, the two pulse oximeters measurements of SpO₂ differed from each other by 3.8 ± 3.3% in the HF group (p<0.01) and 2.0 ± 1.4% in the CAD group (p = 0.065). The difference between the pulse rate from the pulse oximeters and the heart rate from the 12-lead ECG in the HF group was 12±20 BPM (p<0.01) for the finger pulse oximeter, and 2 ± 3 BPM (p = 0.162) for the forehead pulse oximeter.

CONCLUSIONS

Forehead pulse oximeters may be more reliable compared to finger pulse oximeters in obtaining SpO₂ measurements in HF patients during a treadmill maximal exercise test.

Evaluation of key design parameters for mitigating motion artefact in the mobile reflectance PPG signal to improve estimation of arterial oxygenation

OBJECTIVE

Pulse oximetry, a widely accepted method for non-invasive estimation of arterial oxygen saturation (SpO₂) and pulse rate (PR), is increasingly being adapted for mobile applications. Previous work in mitigating motion artefact, which corrupts the photoplethysmogram (PPG) used in pulse oximetry, has focused on reducing noise using signal processing algorithms or through sensor design that controlled only one variable at a time. In this work, we have investigated the effect of several variables such as sensor weight, relative motion, placement, and contact force against the skin that can impact motion artefact independently or by interacting with each other.

APPROACH

We have identified a unique combination of these variables that is most optimal in reducing motion artefacts using a full factorial design of experiments methodology and evaluated the effect of these factors on PPG readings with and without motion.

MAIN RESULTS

Data collected on 10 diverse subjects showed that placement (p  =  0.03), contact force (p  =  0.004), and sensor-to-skin adhesion or relative motion when combined with force (p  <  0.001) had the most significant effect on reducing the motion artefact signal. Sensor weight (p  =  0.822) by itself had no significant effect, however when combined with sensor adhesion (p  <  0.001) had a significant impact.

SIGNIFICANCE

This lays the foundation for future development of more robust sensors that can significantly reduce the effect of motion artefacts in reflectance-based pulse oximetry and could have great clinical value due to significant reduction of SpO₂ errors and false alarms associated with motion artefact, making wearable pulse oximetry more reliable in mobile applications.

Accuracy of pulse oximetry in detection of oxygen saturation in patients admitted to the intensive care unit of heart surgery: comparison of finger, toe, forehead and earlobe probes

Background

Heart surgery patients are more at risk of poor peripheral perfusion, and peripheral capillary oxygen saturation (SpO2) measurement is regular care for continuous analysis of blood oxygen saturation in these patients. With regard to controversial studies on accuracy of the current pulse oximetry probes and lack of data related to patients undergoing heart surgery, the present study was conducted to determine accuracy of pulse oximetry probes of finger, toe, forehead and earlobe in detection of oxygen saturation in patients admitted to intensive care units for coronary artery bypass surgery.

Methods

In this clinical trial, 67 patients were recruited based on convenience sampling method among those admitted to intensive care units for coronary artery bypass surgery. The SpO2 value was measured using finger, toe, forehead and earlobe probes and then compared with the standard value of arterial oxygen saturation (SaO2). Data were entered into STATA-11 software and analyzed using descriptive, inferential and Bland-Altman statistical analyses.

Results

Highest and lowest correlational mean values of SpO2 and SaO2 were related to finger and earlobe probes, respectively. The highest and lowest agreement of SpO2 and SaO2 were related to forehead and earlobe probes.

Conclusion

The SpO2 of earlobe probes due to lesser mean difference, more limited confidence level and higher agreement ration with SaO2 resulted by arterial blood gas (ABG) analysis had higher accuracy. Thus, it is suggested to use earlobe probes in patients admitted to the intensive care unit for coronary artery bypass surgery.

Trial registration

Registration of this trial protocol has been approved in Iranian Registry of Clinical Trials at 2018–03-19 with reference IRCT20100913004736N22. “Retrospectively registered.”

Comparison of nasal and forehead oximetry accuracy and pressure injury in critically ill patients

BACKGROUND

In critically ill patients, clinicians can have difficulty obtaining accurate oximetry measurements.

OBJECTIVE

To compare the accuracy of nasal alar and forehead sensor measurements and incidence of pressure injury.

METHODS

43 patients had forehead and nasal alar sensors applied. Arterial samples were obtained at 0, 24, and 120 hours. Oxygen saturations measured by co-oximetry were compared to sensor values. Skin was assessed every 8 hours.

RESULTS

Oxygen saturations ranged from 69.8%-97.8%, with 18% of measures < 90%. Measurements were within 3% of co-oximetry values for 54% of nasal alar compared to 35% of forehead measurements. Measurement failures occurred in 6% for nasal alar and 22% for forehead. Three patients developed a pressure injury with the nasal alar sensor and 13 patients developed a pressure injury with the forehead sensor (χ2 = 7.68; p = .006).

CONCLUSIONS

In this group of patients with decreased perfusion, nasal alar sensors provided a potential alternative for continuous monitoring of oxygen saturation.

Determination of saturation, heart rate, and respiratory rate at forearm using a Nellcor™ forehead SpO2-saturation sensor

Alterations in arterial blood oxygen saturation, heart rate (HR), and respiratory rate (RR) are strongly associated with intra-hospital cardiac arrests and resuscitations. A wireless, easy-to-use, and comfortable method for monitoring these important clinical signs would be highly useful. We investigated whether the Nellcor™ OxiMask MAX-FAST forehead sensor could provide data for vital sign measurements when located at the distal forearm instead of its intended location at the forehead to provide improved comfortability and easy placement. In a prospective setting, we recruited 30 patients undergoing surgery requiring postoperative care. At the postoperative care unit, patients were monitored for two hours using a standard patient monitor and with a study device equipped with a Nellcor™ Forehead SpO₂ sensor. The readings were electronically recorded and compared in post hoc analysis using Bland-Altman plots, Spearman's correlation, and root-mean-square error (RMSE). Bland-Altman plot showed that saturation (SpO₂) differed by a mean of -0.2 % points (SD, 4.6), with a patient-weighted Spearman's correlation (r) of 0.142, and an RMSE of 4.2 points. For HR measurements, the mean difference was 0.6 bpm (SD, 2.5), r = 0.997, and RMSE = 1.8. For RR, the mean difference was -0.5 1/min (4.1), r = 0.586, and RMSE = 4.0. The SpO₂ readings showed a low mean difference, but also a low correlation and high RMSE, indicating that the Nellcor™ saturation sensor cannot reliably assess oxygen saturation at the forearm when compared to finger PPG measurements.

Pulse oximetry and high-dose vasopressors: a comparison between forehead reflectance and finger transmission sensors

PURPOSE

Pulse oximetry (SpO(2)) measured at finger site via transmission mode may fail in situations of hypoperfusion. Forehead sensors using reflectance technology might be useful in these circumstances. We hypothesized that reflectance SpO(2) would be more accurate than finger SpO(2) in patients with severe shock.

METHODS

A prospective observational study was conducted in an intensive care unit of a university hospital of patients in shock who were treated with high norepinephrine and/or epinephrine doses (≥0.1 μg kg(-1) min(-1)). When blood gas determinations were requested, forehead SpO(2) and finger SpO(2) values were simultaneous recorded. Agreement between SpO(2) measurements with arterial saturation (SaO(2)), obtained by blood analysis with a co-oximeter, was assessed using the Bland-Altman method. The number of outliers, defined by the formula SaO(2) - SpO(2) > ±3 %, indicated the proportion of measurements considered to be clinically unacceptable.

RESULTS

Thirty-two patients were enrolled in the study. With the forehead sensor no reading failure occurred, and 140 paired data sets (forehead SpO(2) vs. SaO(2)) were obtained. Bias and precision were +1.0 and +2.5 %, respectively, and the limits of agreement ranged from -4.0 to 6.0 %. The finger sensor failed to give a value in four cases, thus providing 136 paired data sets (finger SpO(2) vs. SaO(2)) for analysis. Bias and precision were +1.4 and +4.8 %, respectively, and the limits of agreement ranged from -8.0 to 10.9 %. There were 21 (15 %) outliers for the forehead sensor and 43 (32 %) for the finger sensor (P < 0.001).

CONCLUSIONS

Forehead SpO(2) measurements were more accurate than finger SpO(2) when compared with SaO(2) in critically ill patients requiring high-dose vasopressor therapy and should therefore be the preferred method considered.

A comparison of transmittance and reflectance pulse oximetry during vascular surgery

BACKGROUND

New reflectance pulse oximetry probes placed on the forehead may be an improvement over transmittance probes placed on a finger, toe, or earlobe in patients with compromised perfusion. We compared the reliability and accuracy of the 2 types of probes in patients undergoing vascular surgery.

METHODS

Patients with peripheral vascular disease undergoing vascular surgery under general anesthesia were monitored with both a transmittance earlobe probe and a reflectance forehead probe. Spo(2) was recorded continuously from both probes, and arterial blood gas samples were analyzed when clinically indicated. The average values from both probes over each minute were compared using Bland-Altman analysis.

RESULTS

Twenty patients were included yielding a total of 3993 1-min averaged data pairs. Neither probe failed to report a value for more than 1 min. A Bland-Altman plot showed the limits of agreement between the probes of -4.0% to +2.6%. Twenty-eight arterial blood samples were analyzed for 14 patients and Sao(2) closely matched both Spo(2) probe values at the time of sampling. Compared with Sao(2), analysis demonstrated limits of agreement of -4.7% to 6.1% for ear and -3.3% to 3.4% for forehead sites.

CONCLUSIONS

The new reflectance forehead Spo(2) probe tested has acceptable agreement with the older transmittance probe placed on the earlobe for pulse oximetry within typical ranges of Spo(2) in patients undergoing vascular surgery.

Pulse oximetry in adults

Pulse oximetry, a straightforward method for estimating arterial oxygen saturation, can detect hypoxemia early; it's used often and in a variety of settings. But what's not always clear is how frequently-or even whether-patients should be monitored, and unless guidelines are understood and followed, pulse oximetry can be misused or overused. This article reviews the technology and its limitations and discusses current guidelines and their implications for nurses.

Evaluation of cerebral oxygenation during procedural sedation in children using near infrared spectroscopy

STUDY OBJECTIVE

We evaluate the utility of near infrared spectroscopy monitoring and its correlation to conventional respiratory monitors during changes in cardiorespiratory characteristics during pediatric procedural sedation.

METHODS

In this prospective observational study of 100 children, cerebral oxygenation (rSO(2)), pulse oximetry (SpO(2)), and end-tidal carbon dioxide (etco(2)) were monitored continuously. Values were manually recorded at least every 3 minutes from baseline until 30 minutes after sedative administration, resulting in 1,515 triplicate (simultaneous near infrared spectroscopy/etco(2)/SpO(2)) measurements. Correlations between conventional monitoring characteristics (SpO(2) and etco(2)) and rSO(2) were determined, with focus during adverse cardiorespiratory events.

RESULTS

Cerebral oxygenation remained normal in 1,483 of 1,515 measurements (97.9%). rSO(2) decreased significantly during 3 of 13 hypoxic events occurring in 13 patients and during 5 of 17 hypercarbic events occurring in 8 patients, with 15 measurements of greater than 20% decrease from baseline. Cerebral oxygenation increased transiently in 88% of children. During 31 cerebral desaturation recordings, 3 hypoxic recordings (9.3%, always in combination with hypercarbia) and 5 hypercarbic recordings (15.6%) were observed, whereas in 23 (74.2%), cardiorespiratory characteristics were unchanged. There was poor correlation between rSO(2) and both SpO(2) and etco(2), with correlation coefficients of 0.05 (95% confidence interval 0.04 to 0.07) and 0.01 (95% confidence interval -0.01 to 0.02), respectively.

CONCLUSION

Cerebral oxygenation as measured by near infrared spectroscopy demonstrated few significant negative changes during pediatric procedural sedation. Transient cardiorespiratory events seldom altered rSO(2), with hypercarbia having a greater effect than hypoxemia. However, cerebral desaturations frequently occurred without associated cardiorespiratory changes.

Comparison of finger and forehead oximetry sensors in postanesthesia care patients

We compared loss of pulse oximetry signal (dropout rates) for both finger and forehead sensors in postanesthesia patients. Pulse oximetry is a widely practiced method for measuring oxygen saturation. Several studies in various patient populations have demonstrated that low flow states, patient movement, and hypothermia may result in poor signal quality with the use of finger oximetry sensors. These clinical conditions are common in patients as they emerge from anesthesia. New forehead sensors may reduce signal dropout. A method-comparison design was used to compare finger and forehead oximetry signal dropout rates. Of 48 subjects studied, only three had a signal dropout. Overall, there were seven episodes of signal dropout; six of seven occurred with the finger sensor. Signal dropout occurred rarely in PACU subjects. Use of finger sensors for routine postanesthesia monitoring should be adequate in the majority of patients.

Comparison of forehead and digit oximetry in surgical/trauma patients at risk for decreased peripheral perfusion

OBJECTIVE

Measurement of pulse oximetry (Spo(2)) is often impaired in critically ill patients. Forehead reflectance oximetry, the Max-Fast (Nellcor, Pleasanton, CA), may be less susceptible to poor tissue perfusion and could improve accuracy of oxygen saturation measurement. The objective of this study was to evaluate the use of forehead oximetry measures in critically ill surgical/trauma patients.

METHODS

A prospective interventional study of 30 critically ill surgical/trauma patients at risk for decreased peripheral perfusion, as evidenced by need for vasopressor support (24 patients), transfusion of more than 6 unit packed cells in 24 hours (two patients), or an inability to obtain consistent saturation from a digit sensor (four patients), compared forehead and digit-based oximeter Spo(2) readings with co-oximetry (Sao(2)) measurements from arterial blood samples. Sao(2) values were converted to functional oxygen saturation (SO(2)) measurements for the final comparison. Patients were fitted with forehead (Nellcor Max-Fast) and digit (Nellcor Max A; digit 1) sensors connected to Nellcor OxiMax N-595 oximeters and a digit sensor (Nellcor Max A; digit 2) connected to a multiparameter monitor (Philips CMS [Andover, MA]). Three measurements of Sao(2) were obtained from each subject over a 24-hour time period, and simultaneous measurements of Spo(2) were recorded from the three monitors.

RESULTS

The three Spo(2) measurements (forehead, digit 1, and digit 2) were compared with SO(2) values using the Bland-Altman method to assess agreement. Forehead measurements demonstrated a mean bias of -1.39, whereas digit 1 was -2.61 and digit 2 was -3.84. Pearson correlations (r) for forehead, digit 1, and digit 2 with SO(2) were .834, .433, and .254, respectively. There were fewer unsuccessful measurements with the forehead oximetry technique.

CONCLUSIONS

Forehead sensors improve measurement of oxygen saturation in critically ill surgical/trauma patients at risk for decreased peripheral perfusion.

Evaluation of finger and forehead pulse oximeters during mild hypothermic cardiopulmonary bypass

OBJECTIVE

The purpose of this study was to examine and compare the four combination of pulse oximeters (POs) and monitoring sites, the Nihon Kohden BSS-9800 (N), the Masimo SET Radical (M), the Nellcor N550 D-25 (N-D) and the Nellcor N550 Max-Fast (N-MF) in patients with peripheral hypoperfusion.

METHODS

About 20 adult patients undergoing cardiac surgery using mild hypothermic cardiopulmonary bypass (CPB) were studied prospectively. PO sensors were applied on fingers in N, M and N-D, while on the forehead in N-MF.

RESULTS

PO failure was defined as failure to show no SpO2 value or incorrect SpO2 values. PO failure occurred in 12 patients with N, ten patients with M, four patients with N-D and ten patients with N-MF, respectively (p < 0.05 N-D vs. N, M, N-MF). The duration of PO failure was 19 +/- 30% of aortic cross-clamping with N, 29 +/- 33% with M, 10 +/- 26% with N-D and 43 +/- 57% with N-MF, respectively (p < 0.05 N-D vs. M and N-MF).

CONCLUSIONS

The results suggested that N-D is most useful among four combinations of POs and monitoring sites tested in this study for monitoring SpO2 during hypoperfusion. The superiority of N-MF during hypoperfusion was not evident in the present study.

Evaluation of a New Pulse Oximeter Sensor

• Background A new forehead noninvasive oxygen saturation sensor may improve signal quality in patients with low cardiac index.

• Objectives To examine agreement between oxygen saturation values obtained by using digit-based and forehead pulse oximeters with arterial oxygen saturation in patients with low cardiac index.

• MethodsA method-comparison study was used to examine the agreement between 2 different pulse oximeters and arterial oxygen saturation in patients with low cardiac index. Readings were obtained from a finger and a forehead sensor and by analysis of a blood sample. Bias, precision, and root mean square differences were calculated for the digit and forehead sensors. Differences in bias and precision between the 2 noninvasive devices were evaluated with a t test (level of significance P&lt;.05).

• Results Nineteen patients with low cardiac index (calculated as cardiac output in liters per minute divided by body surface area in square meters; mean 1.98, SD 0.34) were studied for a total of 54 sampling periods. Mean (SD) oxygen saturations were 97% (2.4) for blood samples, 96% (3.2) for the finger sensor, and 97% (2.8) for the forehead sensor. By Bland Altman analysis, bias ± precision was −1.16 ± 1.62% for the digit sensor and −0.36 ± 1.74% for the forehead sensor; root mean square differences were 1.93% and 1.70%, respectively. Bias and precision differed significantly between the 2 devices; the forehead sensor differed less from the blood sample.

• Conclusions In patients with low cardiac index, the forehead sensor was better than the digit sensor for pulse oximetry.

Recent findings in the use of reflectance oximetry: a critical review

PURPOSE OF REVIEW

Pulse oximetry is ubiquitous but detailed understanding of the technology is poor. This is illustrated by publications addressing knowledge of pulse oximetry and those warning against the use of transmission pulse oximeter sensors in a reflectance manner, unintended by the manufacturers, owing to the potential for iatrogenic problems. Reflectance oximetry sensors are distinct and their application rather specific. Users must adhere to the manufacturer's guidelines to be assured of approximating the claimed accuracy and other specifications. Moreover, a thorough understanding of the device's shortcomings will optimize performance and avoid misuse. Cautious skepticism is appropriate with use of any technology but particularly with indirect measures of vital signs.

RECENT FINDINGS

The studies of reflectance sensors described here illustrate a diversity of successful applications and opportunities for further research. The genesis of applications for some sensors, for example fetal sensors, has proven helpful in other clinical settings where low mean arterial pressure and need for accurate monitoring of a SpO2 of less than 80% is poorly provided by transmittance sensors. Reflectance sensors are more prone to placement over contaminating sources (for example arteries and pigmentation), but their more sophisticated design can provide greater versatility than transillumination methods.

SUMMARY

This invited review highlights recent developments and applications of reflectance oximetry with an emphasis on the potential clinical and research advantages.