Pulse Oximeter Measurements Research Articles

An unusual presentation of chronic cyanide toxicity from self-prescribed apricot kernel extract

Hypoxia under general anaesthesia is a potentially life-threatening condition. A seemingly well 67-year-old man appeared hypoxic with peripheral pulse oximetric measurement during routine anaesthesia. Postoperatively, the patient admitted to daily...

Optimizing Portable Pulse Oximeter Measurement Accuracy and Consistency During Exercise

Purpose: Monitoring oxygen saturation (SpO2) in some patient populations during exercise is vital. The objectives of this study were to determine whether under conditions of artificial hypoperfusion pulse oximeter performance during exercise was influenced by sensor type, attachment clip reinforcement, or a low pressure arm cuff. Methods: Six different portable oximeter models were tested on study participants at rest with a control (normothermic) and experimental (hypothermic) hand. Oximeters were then tested during treadmill walking at 1 and 2 mph with the experimental hand remaining hypothermic. Electrocardiographic measurements of heart rate were also taken simultaneously. Results: There were differences in SpO2 values between oximeter pairs following cold exposure at rest for most models (5 out of 6) but during walking for only 1 model. There were also differences between oximeter and electrocardiographic heart rate measurements for some models when study participants walked on a treadmill at 1 mph (1 out of 6) and 2 mph (3 out of 6). Conclusions: Results suggest that oximeter performance is better when measuring SpO2 than heart rate. Cold-induced hypoperfusion caused inaccuracies in SpO2 measurements, which were greater at rest than during exercise. Study results also suggest that some pulse oximeters perform better when the oximeter sensor attachment clip is reinforced with an elastic band.

Non-contact video-based vital sign monitoring using ambient light and auto-regressive models

Remote sensing of the reflectance photoplethysmogram using a video camera typically positioned 1 m away from the patient’s face is a promising method for monitoring the vital signs of patients without attaching any electrodes or sensors to them. Most of the papers in the literature on non-contact vital sign monitoring report results on human volunteers in controlled environments. We have been able to obtain estimates of heart rate and respiratory rate and preliminary results on changes in oxygen saturation from double-monitored patients undergoing haemodialysis in the Oxford Kidney Unit. To achieve this, we have devised a novel method of cancelling out aliased frequency components caused by artificial light flicker, using auto-regressive (AR) modelling and pole cancellation. Secondly, we have been able to construct accurate maps of the spatial distribution of heart rate and respiratory rate information from the coefficients of the AR model. In stable sections with minimal patient motion, the mean absolute error between the camera-derived estimate of heart rate and the reference value from a pulse oximeter is similar to the mean absolute error between two pulse oximeter measurements at different sites (finger and earlobe). The activities of daily living affect the respiratory rate, but the camera-derived estimates of this parameter are at least as accurate as those derived from a thoracic expansion sensor (chest belt). During a period of obstructive sleep apnoea, we tracked changes in oxygen saturation using the ratio of normalized reflectance changes in two colour channels (red and blue), but this required calibration against the reference data from a pulse oximeter.

AB0804 Effect of capillaroscopic microvascular changes on the pulse oximeter measurements in systemic sclerosis patients

BackgroundSystemic sclerosis (SSc) is a connective tissue disorder characterized by microangiopathy, autoimmunity and fibrosis. Capillaroscopy is a simple method for direct observation of microvasculature. The pulse oximeter is a noninvasive...

The effect of positive end-expiratory pressure and tripled tidal volume on pleth variability index during hypovolaemia in conscious subjects

The pulse oximeter measurement pleth variability index (PVI) can detect hypovolaemia during positive pressure ventilation. We studied whether PVI can detect a hypovolaemic state in spontaneously breathing humans and whether better discrimination is obtained by modifying the breathing patterns. Experimental study. Clinical physiology department in a university hospital. Fourteen healthy volunteers aged between 18 and 27 (mean 21) years. A hypovolaemic state was induced by lower body negative pressure (LBNP) of 40 mmHg (LBNP40) and 15 mmHg (LBNP15). Data were collected in four separate series with normal breathing and application of positive end-expiratory pressure (PEEP) 5 cmH2O, with and without tripling of the tidal volume. PVI (mean ± standard deviation), heart rate, arterial blood pressure and cardiac index (CI). Cardiac index decreased from 2.4 to 1.7 and 2.1 l min(-1) m(-2) at LBNP40 and LBNP15, respectively (P<0.001). The mean PVI for the four breathing modes increased with the degree of LBNP, from 23.5 ± 5.9% at baseline to 27.9 ± 9.3% at LBNP40, and to 25.2 ± 6.9% at LBNP15 (P<0.01). The greatest increase in PVI, to 31.7 ± 12.3%, was recorded for the PEEP and tripled tidal volume breathing mode when hypovolaemia was induced by LBNP40. However, there was considerable overlap between the LBNP levels. The PVI increased significantly for higher LBNP, but overlap was common regardless of breathing mode. The PVI can be used to indicate a hypovolaemic state during spontaneous breathing in groups but not in individuals. Clinicaltrials.gov identifier NCT01456559.

“New-Generation” Pulse Oximeters in Extremely Low-Birth-Weight Infants

The aim of this study was to evaluate the performance of "new-generation" pulse oximeters in extremely low-birth-weight ([ELBW] ≤ 1000 g) infants. In a prospective crossover observational study, the performance of pulse oximeters of 3 brands (Masimo, Nellcor, and Philips) was evaluated by dual SpO2 measurement in ELBW infants. Disposable probes of either equal or different brands were placed around both feet of the patient simultaneously for approximately 4 hours. Probes were switched between feet every hour. Absolute differences in SpO2 values (ΔSpO2) and the bias between brands were studied. Nine ELWB infants were included (gestational age: mean ± SD = 26(3)/7 ± 1 4/7 weeks). The median (range) ΔSpO2 was 2% (0%-26%). In 9% of the time, ΔSpO2 was 5% or more. The variance of the difference of the 3 pulse oximeter brands was not significantly different. No consequent bias between brands was found. Simultaneously obtained pulse oximeter measurements from the feet of ELBW infants differ from each other. Our results suggest that it is not the brand but the handling of the pulse oximeter in clinical practice, such as the place and positioning of the probe, that influences the performance of the pulse oximeter the most. Improvement in the accuracy of oxygen-monitoring techniques for ELBW infants is required.

Non‐invasive measurements of carboxyhemoglobin and methemoglobin in children with sickle cell disease

Assessment of oxyhemoglobin saturation in patients with sickle cell disease (SCD) is vital for prompt recognition of hypoxemia. The accuracy of pulse oximeter measurements of blood oxygenation in SCD patients is variable, partially due to carboxyhemoglobin (COHb) and methemoglobin (MetHb), which decrease the oxygen content of blood. This study evaluated the accuracy and reliability of a non-invasive pulse co-oximeter in measuring COHb and MetHb percentages (SpCO and SpMet) in children with SCD. We hypothesized that measurements of COHb and MetHb by non-invasive pulse co-oximetry agree within acceptable clinical accuracy with those made by invasive whole blood co-oximetry. Fifty children with SCD-SS underwent pulse co-oximetry and blood co-oximetry while breathing room air. Non-invasive COHb and MetHb readings were compared to the corresponding blood measurements. The pulse co-oximeter bias was 0.1% for COHb and -0.22% for MetHb. The precision of the measured SpCO was ± 2.1% within a COHb range of 0.4-6.1%, and the precision of the measured SpMet was ± 0.33% within a MetHb range of 0.1-1.1%. Non-invasive pulse co-oximetry was useful in measuring COHb and MetHb levels in children with SCD. Although the non-invasive technique slightly overestimated the invasive COHb measurements and slightly underestimated the invasive MetHb measurements, there was close agreement between the two methods.

Evaluation of a Pulse Oximeter Sensor Tester

The Lightman is intended to test the optical and electrical properties of a pulse oximeter probe including the wavelength of the light emitting diode by means of a micro spectrometer. The aim of this study was to evaluate the ability of the Lightman to detect faulty pulse oximeter finger probes by testing the accuracy of the wavelength of the light emitting diode in isolation from the monitor. The pulse oximeter measurements of arterial oxygen saturation from the "accurate" and "inaccurate" probes, as identified by the Lightman, were compared with arterial saturation determined by a co-oximeter. Data was analysed from 63 sets of measurements. In addition, we conducted a national survey to determine the testing procedures used by the Biomedical Engineering departments to evaluate the accuracy of pulse oximeter devices. The bias [95% limits of agreement] for accurate, over-reading and under-reading probes were 0.17% [3.6 to -3.3], 1.44% [5.4 to -2.5] and -1.6% [2.6 to -5.8] respectively. The response rate to the national survey was 75% (142/189); a pulse oximeter tester was used by 93/142 (65%) trusts. Our findings suggest that the Lightman can detect faulty probes and predict reasonably accurately the direction of the probe's error. The Lightman may be considered as a useful tool to assess the accuracy of pulse oximeters. The national survey highlighted a wide variation in the testing procedure utilised to evaluate the accuracy of pulse oximeters. Introduction of guidelines regarding the testing procedure would promote a uniform practice.

Pulse-Oximetric Measurement of Prilocaine-Induced Methemoglobinemia in Regional Anesthesia

Pulse-Oximetric Measurement of Prilocaine-Induced Methemoglobinemia in Regional Anesthesia

Pulse-Oximetric Measurement of Prilocaine-Induced Methemoglobinemia in Regional Anesthesia

The Masimo Radical 7(®) is a new pulse CO oximeter designed to measure methemoglobin. The device has not been evaluated in a clinical setting. In this prospective observational study we compared the arterial methemoglobin levels and the corresponding pulse CO-oximetric values of the Radical 7(®) in regional anesthesia with prilocaine. We analyzed 360 data pairs with methemoglobin values up to 6.6%. The mean bias and limits (± 1.96 sd) of the device were 0.27% (± 1.33%). We found a high degree of agreement in measurement of methemoglobin between the 2 methods.

Safety Evaluation of the Concomitant Use of Clozapine and Benzodiazepines: A Retrospective, Cross-Sectional Chart Review

Previously published case reports have noted severe adverse reactions such as cardiac arrest, respiratory arrest, and sudden death when clozapine (CLZ) and benzodiazepines (BZDs) are used concomitantly. As CLZ and BZD are both used regularly to treat psychiatric illness, it is important to have additional information concerning this potential interaction. The objective of this study was to contribute to the evolving literature by evaluating the occurrence of sudden deaths and cardiac or respiratory events leading to death in patients treated concurrently with CLZ and BZD. A retrospective chart review was conducted at a 240-bed New York State mental health facility. Most patients in this facility have been diagnosed with refractory schizophrenia, resulting in high rates of CLZ use. Electronic and hard copy records of the 490 patients who had been treated with CLZ in this facility at any time from 2001 to 2006 were selected, and the medication records of these patients were assessed for concomitant BZD use. Information on 152 patients who were treated with CLZ and a BZD concomitantly during this time period are included in this study. Data from the facility's mortality review committee were obtained to determine sudden deaths and cardiac or respiratory events leading to death in patients treated with CLZ and BZD concomitantly. Secondary parameters also recorded during the chart review included average duration of CLZ therapy, BZD therapy, and concomitant therapy; average doses of agents used; specific BZD used; number of patients treated with a specific BZD; psychiatric diagnosis; and use of other medications that depress the central nervous system. No deaths occurred as a result of concomitant BZD and CLZ use in the sample examined in this study, suggesting that CLZ and BZD may be safely used concomitantly in many cases. Further study is needed to determine patient characteristics or predisposing factors that might put patients at higher risk of death from this interaction. Our findings are limited by the small sample size and suboptimal frequency of side effect measurements (e.g., measurements of blood pressure and heart rate, reports of hypotensive episodes). Confounding variables that might also play a role in interactions between CLZ and BZDs, but which were not measured in this study, include other types of respiratory compromise, cognitive dysfunction, and organ dysfunction. Precautionary measures that may be used when initiating concomitant CLZ and BZD therapy include slow titration of CLZ, blood pressure monitoring, and/or nightly pulse oximeter measurements.

The Performance of Six Pulse Oximeters in the Environment of Neuronavigation

Although the use of pulse oximeters may be regarded a standard of care for monitoring anesthesia procedures, these monitors may be susceptible to various kinds of disturbances. Recently, it was suggested that neuronavigation equipment may interfere with pulse oximeter accuracy. In this study, we evaluated the effect of a neurosurgical image guidance system on the performance of six different pulse oximeters. Two simple shielding methods were evaluated. Twenty healthy, adult, nonsmoking volunteers were equipped with six different pulse oximeters on both hands. Baseline values for heart rate, arterial oxygen saturation, and signal quality were assessed. After activation of the Brain Lab VectorVision Neuronavigation System, the effects on signal quality and saturation recognition were evaluated. Measurements were repeated using two different shielding techniques, a cotton blanket and aluminum sheets. Activation of the image guidance system resulted in a significant disturbance of signal quality and saturation detection, which was partially reversible by both shielding techniques. Significant differences were noted among the six brands of pulse oximeters for signal quality (P < 0.001) and saturation recognition (P < 0.001), and for the response to shielding methods (P < 0.001). Coverage of the probes with aluminum foil resulted an in undisturbed saturation recognition in all subjects with almost all monitors. Infrared pulse waves from neurosurgical navigation equipment may interfere with pulse oximeter measurements. Shielding the probe with aluminum foil sufficiently eliminated the infrared interference.

An Evaluation of a New Combined Spo2/PtcCO2 Sensor in Very Low Birth Weight Infants

Recently, a new sensor for combined assessment of pulse oximetry oxygen saturation (Spo(2)) and transcutaneous monitoring of carbon dioxide partial pressure (PtcCO(2)) has been introduced (TOSCA 500, Radiometer basel AG, Switzerland) [corrected] We designed this study to evaluate the usability and reliability of TOSCA in neonates with birth weight <or=1500 g (very low birth weight). In a prospective study of 22 newborns, TOSCA was tested, positioning the sensor on the ear pinna with an adhesive attachment clip. Simultaneous monitoring with TOSCA, conventional pulse oximeter (HP; Datex Ohmeda 3740), and a transcutaneous device (TINA TCM3, Radiometer, Copenhagen) was performed for 60 min. PtcCO(2) measurement from TOSCA (PtcCO(2TOSCA)) and TINA (PtcCO(2)) were compared with Pco(2) from blood samples (PCO(2EAB)) at 1 and 60 min. During the monitoring period, values of PtcCO(2TOSCA) were compared with PtcCO(2), and SatO(2) values from TOSCA with those from a pulse oximeter. Corresponding data were compared using Bland-Altman analysis. Bias (precision) at 1 min and at 60 min between PCO(2EAB) and PtcCO(2) values were 3.5 (12.4) mm Hg and 2.8 (10.2), respectively, whereas between PCO(2EAB) and PtcCO(2TOSCA) values were 18.3 (30.4) mm Hg and 1.8 (25) mm Hg. Bland-Altman analysis shows a better correspondence PtcCO(2)/PtcCO(2TOSCA) between 7 and 15 min. No significant differences were found between Spo(2) and SpO(2TOSCA). The TOSCA monitor is safe and easy to apply in very low birth weight newborns. The pulse oximeter measurements may be useful for titrating oxygen therapy. Pco(2) measurement with TOSCA is most useful as a trend and independent confirmation of arterial Pco(2) is required if an accurate value is needed.

Pulse oximetric measurement of prilocaine-induced methemoglobinemia in regional anesthesia

Pulse oximetric measurement of prilocaine-induced methemoglobinemia in regional anesthesia

Daytime pulse oximeter measurements do not predict incidence of pain and acute chest syndrome episodes in sickle cell anemia

Daytime pulse oximeter measurements do not predict incidence of pain and acute chest syndrome episodes in sickle cell anemia

Daytime pulse oximeter measurements do not predict incidence of pain and acute chest syndrome episodes in sickle cell anemia

A prospective, infant cohort study of children with sickle cell anemia was evaluated to determine the relationship between daytime pulse oximeter measurements and the incidence of pain and acute chest episodes (ACS). A total of 130 children were evaluated. The Pearson correlation between SpO2 and pain and ACS episode rates were 0.00 (P = .97) and 0.10 (P = .27), respectively. Daytime SpO2 cannot independently predict the subsequent rate of pain and ACS episodes.

Unexpected Falsely Low Pulse Oximeter Measurements in a Child with Hemoglobin Cheverly

Unexpected Falsely Low Pulse Oximeter Measurements in a Child with Hemoglobin Cheverly

Acute Mountain Sickness and SaO2 in Moderate Altitude Versus Sea-level Residents Ascending to 4300 m

When sea-level residents (SLR) rapidly ascend to ∼4300 m, arterial oxygen saturation (SaO2) is low, and the incidence and severity of acute mountain sickness (AMS) is typically high, especially following heavy exertion in the early hours of altitude exposure. On the other hand, moderate-altitude residents (MAR) have a higher initial SaO2 upon arrival at 4300 m (Muza 2004) compared to SLR, but it is unknown whether they also exhibit a lower incidence and severity of AMS. PURPOSE: To determine in MAR, compared to SLR, whether ventilatory acclimatization, obtained during residence at 1800–2200 m (21 ±3 mo, ± SD), reduces the incidence and severity of AMS for up to 72 h of exposure to 4300 m with heavy exertion in the early hours of altitude exposure. METHODS: Sixteen MAR (9 men, 7 women; 30±3 yr, 69±9 kg) and eighteen male SLR (25±5 yr, 78±9 kg;) completed an Environmental Symptoms Questionnaire (ESQ) and resting SaO (pulse oximeter) measurement in the morning at their residence altitude (Colorado Springs, CO (CS), and Palo Alto, CA (PA), respectively) and after ∼10, 24, 48, and 72 h residence on Pikes Peak (PP, 4300 m, 458 mmHg). AMS was assessed using the validated “AMS-Cerebral” (AMS-C) factor score in which a score of > 0.7 is indicative of AMS. Each subject completed a 2–4 h cycle exercise bout (50–60% VO2peak) within the first 5 h of altitude exposure. RESULTS: The incidence of AMS was lower (P < 0.05) in MAR compared to SLR, respectively, at PP10 (13% vs. 72%), PP24 (0% vs. 61 %), PP48 (0% vs. 56%), and PP72 (0% vs. 44%). The severity of AMS was also lower (P < 0.05) in MAR compared to SLR, respectively at PP10 (0.4 ± 0.2 vs. 1.5±1.3), PP24 (0.2 ± 0.2 vs. 1.4±1.2), PP48 (0.1 ± 0.2 vs. 1.4±1.5), andPP72 (0.1 ± 0.1 vs. 0.7 ± 0.7). The PP3 exercise SaO2 was higher (P < 0.01) in MAR compared to SLR (80±3% vs.74±6%). Resting SaO2 was similar in MAR and SLR at PP24 (86±2% vs. 83±6%), but higher (P < 0.05) in MAR at PP48 (89±3% vs. 83±6%) and PP72 (89±3% vs. 84±4%). CONCLUSION:These results show that compared to residence at sea level, residence at moderate altitude is very effective in decreasing the incidence and severity of AMS upon exposure to a higher altitude (4300 m) due, in part, to a greater degree of ventilatory acclimatization.

A method for calculation of arterial acid–base and blood gas status from measurements in the peripheral venous blood

In non-emergency medical departments such as internal medicine sampling of arterial blood and analysis for acid–base status is not routinely performed. Peripheral venous blood is routinely taken but interpretation of its acid–base status is difficult. This paper presents a method for calculation of arterial acid–base and blood gas status from measurements in peripheral venous blood combined with a pulse oximeter measurement of arterial saturation. The use of the method has been illustrated using the data of three patients with different acid–base, haemodynamic, and metabolic conditions. The sensitivity of the method has been tested for measurement errors including venous blood acid–base and blood gas status and pulse oximetry; errors due to physiological assumptions including the values of RQ and strong acid production at the tissues; and errors due to air bubbles in the blood. Errors due to these effects are relatively insignificant except for errors in calculated arterial PO 2, particularly when SpO 2 is greater than 97%; and errors when the change in base excess across the sampling site due to strong acid production is greater that 1.3 mmol/l.

Asthma Management Issues in Infancy and Childhood

The prevalence of asthma has been increasing worldwide over the past 2 decades, especially the prevalence of childhood asthma. Currently, the prevalence of childhood asthma is around 3-20% in different countries based on the report from the International Study of Asthma and Allergies in Children (ISAAC). Asthma in childhood is predominantly an extrinsic asthma. In general, countries in the coastal, temperate, and subtropical zones have the highest prevalence of mite- and cockroach-sensitive asthma. Countries in the sub-arctic or semi-arid areas have a lower prevalence of childhood asthma, mostly associated with sensitization to pet dander, moulds, and pollens. Many genes have been linked to asthma in different ethnic populations. A global consensus for the management of asthma in adults and children >5 years of age has been made possible in the Global Initiative for Asthma (GINA) guidelines, where a step-wise management program using inhaled medication with and without oral anti-inflammatory drugs is recommended. The management of asthma in children <5 years of age remains inconclusive. Recent studies suggest that inherited susceptibility associated with risk factors from the prenatal and postnatal environment is likely to promote allergic sensitization and development of asthma. Consequently, early prevention of prenatal sensitization in utero and environmental control of early life exposure to various allergens may decrease the incidence of childhood asthma. In the management of moderate persistent asthma in infants and young children <5 years of age, airway resistance tests (FEV(1) or PEF) are not of significance, but assessment of respiratory rate and skin pulse oximeter measurements of arterial oxygen saturation are helpful. Moreover, recent advances in pharmacogenetics and pharmacogenomics may provide better individualized care for early pharmacological prevention of childhood asthma via selective modulation of airway remodeling.