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Pulse oximetry is commonly used in patients who are critically ill in order to help titrate oxygen delivery. We aimed to investigate the accuracy of peripheral pulse oximetry in patients who were critically ill with COVID-19 pneumonitis and were receiving invasive mechanical ventilation and to determine if this was affected by patient ethnicity. Effect of patient ethnicity on the accuracy of peripheral pulse oximetry in patients with COVID-19 pneumonitis requiring mechanical ventilation. [Extracted from the article]

Unlike other studies into racial bias in oximetry, very few profoundly hypoxic patients were enroled - in our opinion a strength of this study, as we feel, few clinicians would choose to rely on oximetry alone in the context of profound hypoxia. Keywords: bias; oximetry; skin pigmentation EN bias oximetry skin pigmentation 129 131 3 01/11/22 20220201 NES 220201 Recent media stories on the potential impact of skin pigmentation on the accuracy of medical and healthcare devices have provoked confusion and anxiety for both clinicians and their patients [1, 2] Furthermore, the Black Lives Matter movement has focused attention on the impact of racial bias within medical training [3]. Comparing paired arterial oxygen saturation samples with pulse oximetry measurements, the authors concluded that while the margin of error on pulse oximetry could be clinically significant, depending on the scenario, there was little evidence for error being attributable to skin pigmentation. Adler [15] concluded that there was no effect of skin pigmentation, although observed more technical errors in obtaining a stable reading in patients with darker skin pigmentation. [Extracted from the article]

Episodic and ongoing hypoxaemia are well-described after surgery, but, to date, no studies have investigated the occurrence of episodic hypoxaemia following minimally-invasive colorectal surgery performed in an enhanced recovery setting. We aimed to describe the occurrence of postoperative hypoxaemia after minimally-invasive surgery in an enhanced recovery setting, and the association with morphine use, incision site, fluid intake and troponin increase. We performed a prospective observational study of 85 patients undergoing minimally-invasive surgery for colorectal cancer between 25 August 2016 and 17 August 2017. We applied a pulse oximeter with a measurement rate of 1 Hz immediately after surgery either until discharge or until two days after surgery, and recorded the oxygen saturation. We measured troponin I during the first four days after surgery, or until discharge. The median (IQR [range]) length of stay was 3 (2-4 [1-38]) days. Thirty-six percent of patients spent more than 1 h below an oxygen saturation of 90% (4.2% of the day), and with a median (IQR [range]) proportion of 1.3 (0.2-11.1 [0.0-21.4])% of the day spent with an oxygen saturation below 88%. We found no associations between time spent below an oxygen saturation of 88% and morphine use (p = 0.215), fluid intake (p = 0.446), complications (p = 0.808) or extraction site (p = 0.623). Postoperative increases in troponin I were associated both with time spent below an oxygen saturation of 88% (p = 0.026) and hypopnoea episodes (p = 0.003). Even with minimally-invasive surgery and enhanced recovery after surgery, episodic hypoxaemia and hypopnoea episodes are common, but are not associated with morphine use, fluid intake or incision site. Further studies should investigate the relationship between hypoxaemia and troponin increase. [ABSTRACT FROM AUTHOR]

Intravenous remifentanil patient-controlled analgesia can be used during labour as an alternative to epidural analgesia. Adverse effects of opioids, including hypoxia and bradycardia, may lead to maternal morbidity and mortality. We devised an interactive feedback system based on a clinical proportional algorithm, to continuously monitor for adverse effects to enhance safety and better titrate analgesia. This vital signs-controlled, patient-assisted intravenous analgesia with remifentanil used a prototype delivery system linked to a pulse oximeter that evaluated maternal oxygen saturation and heart rate continuously. With this system, we detected oxygen saturation < 95% for more than 60 s in 15 of 29 subjects (52%); and heart rate < 60 min-1 for more than 60 s in 7 of 29 subjects (24%) during use. The system automatically responded appropriately by reducing the dosages and temporarily halting remifentanil administration, thus averting further hypoxia and bradycardia. [ABSTRACT FROM AUTHOR]

Pulse oximetry is an essential monitor for safe anaesthesia but is often not available in low-income countries. The aim of this study was to determine whether the introduction of pulse oximetry with training was feasible and could reduce the incidence of oxygen desaturation during anaesthesia in a low-income country. Pulse oximeters were donated, with training, to 83 non-physician anaesthetists in Malawi. Knowledge was tested immediately before and after training and at follow-up. Providers were asked to record the lowest peripheral oxygen saturation (SpO2 ) for the first 100 cases anaesthetised after training. The primary clinical outcome was the proportion of cases with an oxygen desaturation event (SpO2 < 90%). Seventy-seven of 83 (93%) participants completed all pre- and post-training tests. Pulse oximetry knowledge improved after training from a median (IQR [range]) score of 39 (37-42 [28-48]) to 44 (42-46 [35-50]) and this knowledge was maintained for 8 months (p < 0.001). Oxygen saturation data and provider responses were recorded for 4772 cases. The proportion of oxygen desaturation episodes decreased from 17.2% to 6.5%, representing a 36% reduction in the odds of an oxygen desaturation event in the second 50 cases compared with the first 50 (OR 0.64, 95%CI 0.50-0.82, p < 0.001). We conclude that donation of pulse oximeters, with training, in Malawi was feasible, improved knowledge and reduced the incidence of oxygen desaturation events. [ABSTRACT FROM AUTHOR]

Numerous studies of remifentanil patient-controlled analgesia during labour have shown high levels of maternal satisfaction, but concerns remain, especially over the side-effects of sedation and respiratory depression. We conducted a prospective observational study of maternal oxygen desaturation during remifentanil patient-controlled analgesia. Pulse oximetry values were recorded every eight s and later downloaded for analysis. A desaturation episode was defined as oxygen saturation < 90%. We collected 148 h of data in 61 women, during which we observed 176 desaturation episodes. These episodes occurred in 43 (70%) women. The median (IQR [range]) of the lowest saturation during each episode was 87 (85-89 [68-89])% with duration 16 (8-24 [8-104]) s. Supplementary oxygen reduced the time per hour spent with saturation < 90%, but not the depth or duration of individual episodes. Desaturation episodes were twice as common during the second stage of labour as compared with the first stage. Prior opioid administration, bolus size and use of nitrous oxide during patient-controlled analgesia use were not found to influence frequency, depth or duration of desaturation episodes. Although these findings suggest desaturation occurs more frequently during remifentanil patient-controlled analgesia than previously reported, the results are comparable with earlier oximetry studies of women who received nitrous oxide and pethidine during labour. [ABSTRACT FROM AUTHOR]

Pulse oximetry is widely accepted as essential monitoring for safe anaesthesia, yet is frequently unavailable in resource-limited settings. The Lifebox pulse oximeter, and associated management training programme, was delivered to 79 non-physician anaesthetists attending the 2011 Uganda Society of Anaesthesia Annual Conference. Using a standardised assessment, recipients were tested for their knowledge of oximetry use and hypoxia management before, immediately following and 3-5 months after the training. Before the course, the median (IQR [range]) test score for the anaesthetists was 36 (34-39 [26-44]) out of a maximum of 50 points. Immediately following the course, the test score increased to 41 (38-43 [25-47]); p < 0.0001 and at the follow-up visit at 3-5 months it was 41 (39-44 [33-49]); p = 0.001 compared with immediate post-training test scores, and 75/79 (95%) oximeters were in routine clinical use. This method of introduction resulted in a high rate of uptake of oximeters into clinical practice and a demonstrable retention of knowledge in a resource-limited setting. [ABSTRACT FROM AUTHOR]

Pulse oximetry is a standard of care during anaesthesia in high-income countries. However, 70% of operating environments in low- and middle-income countries have no pulse oximeter. The 'Lifebox' oximetry project set out to bridge this gap with an inexpensive oximeter meeting CE (European Conformity) and ISO (International Organization for Standardization) standards. To date, there are no performance-specific accuracy data on this instrument. The aim of this study was to establish whether the Lifebox pulse oximeter provides clinically reliable haemoglobin oxygen saturation (SpO2) readings meeting USA Food and Drug Administration 510(k) standards. Using healthy volunteers, inspired oxygen fraction was adjusted to produce arterial haemoglobin oxygen saturation (SaO2) readings between 71% and 100% measured with a multi-wavelength oximeter. Lifebox accuracy was expressed using bias (SpO2 − SaO2), precision ( SD of the bias) and the root mean square error ( A rms). Simultaneous readings of SaO2 and SpO2 in 57 subjects showed a mean ( SD) bias of −0.41% (2.28%) and A rms 2.31%. The Lifebox pulse oximeter meets current USA Food and Drug Administration standards for accuracy, thus representing an inexpensive solution for patient monitoring without compromising standards. [ABSTRACT FROM AUTHOR]

This systematic review and meta-analysis assessed the accuracy of plethysmographic variability index derived from the Massimo® pulse oximeter to predict preload responsiveness in peri-operative and critically ill patients. A total of 10 studies were retrieved from the literature, involving 328 patients who met the selection criteria. Overall, the diagnostic odds ratio (16.0; 95% CI 5-48) and area under the summary receiver operating characteristic curve (0.87; 95% CI 0.78-0.95) for plethysmographic variability index to predict fluid or preload responsiveness was very good, but significant heterogeneity existed. This could be explained by a lower accuracy of plethysmographic variability index in spontaneously breathing or paediatric patients and those studies that used pre-load challenges other than colloid fluid. The results indicate specific directions for future studies. [ABSTRACT FROM AUTHOR]

Summary Peripheral pulse oximetry has become a core monitoring modality in most fields of medicine. Pulse oximeters are used ubiquitously in operating theatres, hospital wards, outpatient clinics and general practice surgeries. This study used a portable spectrometer (Lightman®, The Electrode Co. Ltd., Monmouthshire, UK) to measure the emission spectra of the two light emitting diodes within the pulse oximeter sensor and to determine the accuracy of 847 pulse oximeters currently in use in 29 NHS hospitals in the UK. The standard manufacturing claim of accuracy for pulse oximeters is ± 2-3% over the range of 70-100% SpO2. Eighty-nine sensors (10.5%) were found to have a functional error of their electrical circuitry that could cause inaccuracy of measurement. Of the remaining 758 sensors, 169 (22.3%) were found to have emission spectra different from the manufacturers' specification that would cause an inaccuracy in saturation estimation of > 4% in the range of 70-100% saturation. This study has demonstrated that a significant proportion of pulse oximeter sensors may be inaccurate. [ABSTRACT FROM AUTHOR]

Basic blood gas analysers (calibrated as per regulatory standards) that do not include integral co-oximetry modules are not considered accurate indicators of the arterial oxygen saturation, and calculated arterial oxygen saturation values from these blood gas analysers are therefore a source of error. It is well known that the gold standard for measuring oxygen saturation is co-oximetry, performed on arterial blood gas samples using multi-wavelength spectrophotometry, and not arterial blood gases by blood gas machines [1, 4]. Racial discrepancies in oximetry: where do we stand?. [Extracted from the article]

The laryngeal mask airway is included as a first line airway device during adult resuscitation by first responders. However, there is little evidence for its role in paediatric resuscitation. Using anaesthetised children as a model for paediatric cardiopulmonary arrest, we compared the ability of critical care nurses to manually ventilate the anaesthetised child via the laryngeal mask airway compared with the facemask and oropharyngeal airway. The airway devices were inserted in random order and chest expansion was measured using an ultrasound distance transducer. The critical care nurses were able to place the laryngeal mask airway and achieve successful ventilation in 82% of children compared to 70% using the facemask and oropharyngeal airway, although the difference was not statistically significant (p = 0.136). The median time to first successful breath using the laryngeal mask airway was 39 s compared to 25 s using the facemask (p < 0.001). In this group of nurses, we did not show a difference in ventilation via a laryngeal mask airway or facemask, although facemask ventilation was achieved more quickly. [ABSTRACT FROM AUTHOR]

A 41-year-old woman presented with the clinical features of methaemoglobinaemia after drinking Chinese herbal medicine. A life threatening methaemoglobin level of 68% was measured. Both clinical and laboratory diagnostic difficulties were encountered. The pitfalls of pulse oximeter, blood gas analysis and co-oximeter interpretation during diagnosis and after methylene blue administration are discussed. [ABSTRACT FROM AUTHOR]

Pulse oximeters may delay displaying the correct oxygen saturation during the onset of hypoxia. We investigated the desaturation response times of pulse oximeter sensors (forehead, ear and finger) during vasoconstriction due to mild hypothermia and vasodilation caused by glyceryl trinitrate. Ten healthy male volunteers were given three hypoxic challenges of 3 min duration under differing experimental conditions. Mild hypothermia increased the mean response time of finger oximeters from 130 to 215 s. Glyceryl trinitrate partly offset this effect by reducing the response time from 215 to 187 s. In contrast, the response times of the forehead and ear oximeters were unaffected by mild hypothermia, but the difference between head and finger oximeters was highly significant (p < 0.0001). The results suggest that the head oximeters provide a better monitoring site for pulse oximeters during mild hypothermia. [ABSTRACT FROM AUTHOR]

Shows how the presence of a pulse oximeter enables the early diagnosis of the extravasation of fluid from a peripheral venous cannula. Change in rate of oxygen saturation; Arterial waveform from left radial artery cannula; Decrease in blood flow and venous congestion.

Analyzes the blood gases in the line of hemofiltration units using a Viamed pulse oximeter finger probe. Deterioration of saturation signal; Waves caused by blood pump rotation; Effect of dialysate fluid pump.

A method is described which allows an approximation to the arterial flow waveform to be derived from a pulse oximeter waveform. The observed pulse oximeter waveform is the sum of arterial inflow and venous outflow. These components are separated mathematically. Subtraction of the venous outflow reveals the underlying arterial flow waveform. The assumptions on which the method is based are stated explicitly and discussed. [ABSTRACT FROM AUTHOR]

This study compared derived arterial flow waveforms, extracted from pulse oximeter waveforms, with Doppler flow waveforms. Fingertip pulse oximeter waveforms and radial artery Doppler flow waveforms were measured simultaneously in volunteers. The pulse oximeter waveforms were processed to extract the arterial flow waveforms and these were compared with the measured Doppler waveforms. They were very similar. [ABSTRACT FROM AUTHOR]

Highlights the role of the pulse oximeter in continuous intraoperative patient monitoring during anesthesia induction. Patient monitoring standards outlined in the Association of Anesthetists of Great Britain and Ireland recommendations; Factors to consider in intraoperative patient monitoring; Suggestion for the audible bleeping on a pulse oximeter to be enabled.

Proposes a solution to the problem of positioning pulse oximeters. Problem encountered with critically ill patients; Advantages of positioning the probe on the nasal septum.

Presents several letters which focused on topics that are related to medical care and anesthetics. Exposure of nurses to radiation on intensive care units; Effect of sedation on desaturation; Use of pulse oximetry in monitoring during anesthesia.

New measurement principles in pulse oximetry have been introduced to decrease the incidence of false movement alarms. Experimental studies have shown that the new Nellcor Symphony N-3000 may reduce the incidence of false alarms when monitoring during different activities. We compared the Nellcor Symphony N-3000 with the Nellcor N-200 pulse oximeter, when monitoring patients in the general surgical ward. Twenty-two patients were monitored during unrestricted ward activities for a total of 275 h with a N-3000 and a N-200 pulse oximeter simultaneously. Data were analysed for lack of concordance between the two pulse oximeters with respect to frequency of registered hypoxaemic episodes and thus the amount of time spent in the alarm state. The median number of desaturation episodes with the N-200 was 18 (range 0–511) compared with four (range 0–476) with the N-3000 (p < 0.0001). The median number of drop-outs (loss of signal) was 13 (range 1–46) with the N-200 compared with nine (2–41) with the N-3000 (p = 0.06). The N-200 registered saturation values of 85% or below for 23% of the observation time compared with 6% of the observation time with the N-3000 pulse oximeter (p < 0.0001). The different working principles of the two generations of oximeters were reflected in the present results derived from a clinical setting. The Nellcor Symphony N-3000 may offer an advantage compared with the Nellcor N-200, because of the reduced frequency of alarms and total time in alarm when monitoring patients in the general surgical ward. [ABSTRACT FROM AUTHOR]

We present a young man who developed fat embolism syndrome following a fractured femoral shaft. By intermittently measuring oxygen saturation with a pulse oximeter and varying the inspired partial pressure of oxygen we were able to quantify the development of shunt and ventilation/perfusion (V/Q) mismatch over the course of his illness. Shunt and low V/Q gradually improved in the week following admission but deteriorated following general anaesthesia for nailing of the femur. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Clinical evaluation of a novel technology for non-invasive and continuous measurement of plasma haemoglobin concentration," by A. J. Broderick and colleagues in the 2015 issue.

The article reports on a research that compared the spectrographic accuracy of the Lightman device with an industrial laboratory spectrometer from Bentham Instruments Ltd. The study found that the light absorption by oxyhaemoglobin varied with wavelength. The researchers have used specific software for pulse oximeters models to convert absolute wavelength measurements into predicted errors.

A response from the author of the article "Clinical evaluation of a novel technology for non-invasive and continuous measurement of plasma haemoglobin concentration" in the 2015 issue is presented.

Presents a case on the use of a reflectance pulse oximeter probe in a patient with necrotizing pancreatitis undergoing a pancreatic necrosectomy. Detection of a generalized oedema and poor signal from a finger pulse oximeter probe; Accuracy of the reflectance pulse oximeter probe with a headband in providing a satisfactory signal; Citation of burns as a complication of pulse oximetry.

Focuses on patient monitoring during transfers from the operating theater to the recovery area. Closing the gap in continuous monitoring from the anesthetic room to the operating theater; Application of pulse oximeter and non-invasive blood pressure monitor; Duration of the interruption.

Relates a problem that occurred concerning the use of pulse oximetry on an elderly gentleman with moderately severe dementia. Loss of the pulse oximetry trace; Role of the patient in the loss; Device's potential as a medical hazard.

Examines the means of detecting hypoxemia in the late post-operative stage. Use of Nellcor-200 pulse oximeter to identify hypoxemic episodes; Difference between using pulse oximeter alone and using oximeter with other detecting gadgets in identifying hypoxemia; Incidence of nocturnal hypoxemia in post-orthopedic or abdominal surgery.

Replies to a report of false high reading involving a Hewlett-Packard pulse oximeter in the January 1998 issue of the periodical 'Anaesthesia.' Damage to the sensor housing revealed by an inspection of the device; Incorrect reading that can be caused by a damaged sensor housing; Importance of regular inspection of all pulse oximetry sensors for signs of physical damage.

The article offers information on the observation from the article "Misalignment of Disposable Pulse Oximeter Probes Results in False Saturation Readings That Influence Anesthetic Management" by Z. Guan in the previous issue.

Reports on the use of Pleasanton, California-based medical equipment manufacturer Nellcor Inc.'s Oxiband pulse oximeter probe. Use of oximeter probe with single-use adhesive band; Attachment of oximeter to a patient's ear lobe with a clothes peg; Application of clothes peg to the part connecting the light-emitting unit and the light-sensor unit.

Relates an incident involving a mother and a baby during a cesarean section under spinal anesthesia. Safe delivery of the baby; Anesthesiologist's discovery that the midwife had removed the pulse oximeter from the mother to allow a hug with her baby.

Responds to an article which encourages anesthetists to listen continuously to tonal changes in the pulse oximeter bleep during anesthesia induction, published in the periodical 'Anaesthesia.'

Reports the cause of post-operative corneal abrasion. Position of the disposable pulse oximeter probe on the index finger; Prevention of corneal abrasion; Suggestion on the positioning of the probe.

Reports on an incident where a Hewlett-Packard (HP) pulse oximeter read a false high oxygen saturation that led to a patient becoming hypoxic through over reliance on the device. Return of the machine to HP despite an 'in-house' finding that the machine had no defect; One other report of false high reading involving the same HP pulse oximeter model.