Aspectos técnicos y regulatorios sobre el uso de oxímetros de pulso en el monitoreo de pacientes con COVID-19, 7 de agosto del 2020 / Technical and Regulatory Aspects of the Use of Pulse Oximeters in Monitoring COVID-19 Patients, 7 August 2020

En este documento se presentan consideraciones técnicas y regulatorias para el uso de oxímetros de pulso como herramienta en el monitoreo clínico de pacientes con COVID-19. Asimismo, se resume la evidencia disponible sobre la eficacia, efectividad y seguridad de los diferentes tipos de oxímetros de pulso, sus limitaciones y recomendaciones de utilización. Está destinado a profesionales de la salud, así como a autoridades sanitarias y demás tomadores de decisiones sobre el uso de tecnologías sanitarias para la atención y cuidado de pacientes con COVID-19.

This document presents technical and regulatory considerations for the use of pulse oximeters as a tool in clinical monitoring of COVID-19 patients. It also summarizes available evidence on the efficacy, effectiveness, and safety of different types of pulse oximeters, their limitations, and recommendations for use. It is intended for health professionals, as well as health authorities and other decision makers responsible for health technologies for the care of COVID-19 patients.

Nuevas generaciones de oximetría de pulso en neonatología / New generations of pulse oximetry in neonatology

CONTEXTO: El diagnóstico y monitoreo del nivel de oxígeno1 (O2) en el organismo resulta de gran importancia en la atención de salud en diversos casos. La insuficiencia respiratoria hipoxémica es la primera causa de hospitalización en pediatría, el control estricto de la oxemia es mandatorio en pacientes neonatos prematuros, debido al riesgo de daños retinianos ante la exposición prolongada a concentraciones elevadas de oxígeno, también es utilizada la evaluación de la saturación de oxígeno en los miembros para descartar ciertas cardiopatías congénitas. En los pacientes críticos con necesidad de ventilación mecánica u otras modalidades, la determinación del oxígeno en sangre resulta un parámetro imprescindible para monitorear la calidad del tratamiento de soporte. En estos pacientes puede realizarse por determinación directa en catéteres arteriales, o indirectamente por métodos de saturometría de pulso. La evaluación de la hipoxemia se realiza con medición de gases arteriales y a través de metodologías no invasivas con saturometría de pulso, sin embargo, esta medición puede verse afectada por diversos factores como la intensidad de la luz ambiental, pigmentación de la piel, perfusión tisular, concentración de hemoglobina y otros. La cianosis es un signo tardío de hipoxemia apareciendo habitualmente con saturación de oxígeno menor a 75%. La oximetría de pulso es una herramienta que permite medir en forma no invasiva la saturación de oxígeno de la hemoglobina y ha significado una revolución en el manejo y monitorización de los pacientes con insuficiencia respiratoria. Se caracteriza por ser simple, no invasiva y razonablemente confiable en la mayoría de las circunstancias clínicas.En los últimos 15 años los avances tecnológicos y la competencia entre marcas y modelos van favoreciendo la aparición de oxímetros de pulso más pequeños y más económicos, difundiendo su utilización ampliamente. METODOLOGÍA: Se realizó una búsqueda en las bases de datos bibliográficas detalladas a continuación, en el repositorio y página de OMS y OPS, en BRISA de RedETSA, en sitios de Agencias de Evaluación de Tecnologías Sanitarias y Agencias nacionales e internacionales reguladoras de alimentos, medicamentos y dispositivos, las que se detallan más abajo, en Tripdatabase, Epistemonikos, buscadores genéricos de Internet como google académico. Se buscaron Guía de Práctica Clínica de las sociedades relacionadas con atención del recién nacido, neonatología, cuidados críticos, terapias respiratorias invasivas, priorizando las del Ministerio de Salud de la Nación Argentina y de la Provincia de Neuquén. RESULTADOS: Se realizó una búsqueda en los registros de la Administración Nacional de Medicamentos, Alimentos y Tecnología Médica (ANMAT), de las opciones de oximetría de pulso disponibles para comercialización en Argentina. Descripción de la Tecnología: Se identifican dos tecnologías disponibles en Argentina que se corresponden con nuestra definición de nueva generación de oxímetro de pulso. Tecnologías alternativas: Medición de PO2 capilar por saturometría convencional y punción para medición de gases arteriales. CONCLUSIONES: La utilización de la oximetría de pulso está recomendada a nivel mundial para uso en pacientes críticos de neonatología y rastreo de cardiopatías congénitas en recién nacidos sanos . Al hablar de las nuevas generaciones de oximetría de pulso (tecnología SET y nuevos algoritmos) no existe evidencia de alta calidad que respalde el reemplazo de los convencionales, teniendo en cuenta su elevado costo, costo de oportunidad y potencial impacto en la equidad. Los expertos consultados muestran satisfacción con los resultados obtenidos con este tipo de nueva tecnología, pero no puede respaldarse su percepción en evidencias científicas sólidas con bajo riesgo de sesgos Al considerar que la tecnología SET está en uso desde hace 10 años en la neonatología del HPN mediante donaciones de programas verticales, se recomienda la gestión de estas adquisiciones en forma centralizada y de esta manera unificar los criterios para los Servicios de Neonatología de la provincia. Se recomienda centralizar y revisar los criterios de aceptación de donaciones de equipos médicos. Se recomienda la renovación de equipamientos según necesidad en el Servicio de Neonatología del HPN, siendo esta donde se internan los pacientes críticos y la redistribución de los equipos antiguos en el resto de los hospitales de la provincia. En todos los casos es necesario un plan de gestión del ciclo de la tecnología que incluya los correspondientes mantenimientos preventivos y correctivos, el monitoreo de fallas y la planificación a mediano y largo plazo.

Comparison of Two NIRS Tissue Oximeters (Moxy and Nimo) for Non-Invasive Assessment of Muscle Oxygenation and Perfusion.

BACKGROUND: Near-infrared spectroscopy (NIRS) tissue oximeters enable non-invasive measurement of muscle oxygenation and perfusion. Several NIRS oximeters are currently available, particularly for muscle measurements. AIM: To evaluate the agreement of oxygenation and perfusion measurements obtained by two devices (Moxy, Fortiori Designs LLC, USA, and Nimo, Nirox, Italy) during an arterial occlusion test on the arm. SUBJECT AND METHODS: Arterial occlusions were conducted at the arm of one individual for 10 min with 200 mmHg. Measurements were made twice a day on five different days. Both NIRS devices were fixed at the arm (covering the muscles extensor carpi ulnaris, extensor digitorum, and flexor carpi ulnaris). RESULTS: The experiment revealed that i) both devices could detect changes in muscle oxygenation and perfusion during the occlusion, but ii) the magnitudes and dynamic changes differed between the two devices. DISCUSSION AND CONCLUSION: Both devices had different performances with regard to the measurement of tissue oxygenation and perfusion. This study shows that it might be worthwhile to compare all NIRS tissue oximeters currently available for muscle measurement in a large systematic study to increase the comparability of measurements obtained with different devices.

introduce nationwide pulse oximetry screening for the detection of critical congenital heart disease and other hypoxaemic conditions in the newborn.

The mortality risk for infants with critical congenital heart disease (CCHD) unrecognised at the time of birth is high. Pulse oximetry has been utilised as a screening tool for the detection of these anomalies in the newborn as the majority will have a degree of hypoxaemia. This screening strategy has a moderate sensitivity and excellent specificity for the detection of CCHD, and a low false-positive rate. Respiratory and infective diseases are responsible for a large number of positive test results. The early recognition of these diseases can also improve health outcomes. Different approaches have been taken to introduce screening, ranging from hospital-led initiatives to mandatory state-wide policies. A study conducted in New Zealand demonstrated that sector-led screening initiatives are unlikely to result in equitable outcomes. In this midwifery-led maternity setting a nationwide pulse oximetry screening programme with adequate human and material resources should be introduced.

Current Neurologic Assessment and Neuroprotective Strategies in Cardiac Anesthesia: A Survey to the Membership of the Society of Cardiovascular Anesthesiologists.

BACKGROUND: Neurologic injury and cognitive disorder after cardiac surgery are associated with morbidity and mortality. Variability in the application of neuroprotective strategies likely exists during cardiac surgery. The Society of Cardiovascular Anesthesiologists (SCA) conducted a survey among its members on common perioperative neuroprotective strategies: assessment of aortic atheromatous burden, management of intraoperative blood pressure, and use of cerebral oximetry. METHODS: A 15-item survey was developed by 3 members of the SCA Continuous Practice Improvement - Cerebral Protection Working Group. The questionnaire was then circulated among all working group members, adapted, and tested for face validity. On March 26, 2018, the survey was sent to members of the SCA via e-mail using the Research Electronic Data Capture system. Responses were recorded until April 16, 2018. RESULTS: Of the 3645 surveys e-mailed, 526 members responded (14.4%). Most responders worked in academic institutions (58.3%), followed by private practices (38.7%). Epiaortic ultrasound for the assessment of aortic atheromatous burden was most commonly utilized at the surgeon's request (46.5%). Cerebral oximetry was most commonly used in patients with increased perioperative risk of cerebral injury (41.4%). Epiaortic ultrasound (1.9%) and cerebral oximetry (5.2%) were rarely part of a standardized monitoring approach. A majority of respondents (52.0%) reported no standardized management strategies for neuroprotection during cardiac surgery at their institution. A total of 55.3% stated that no standardized institutional guidelines were in place for managing a patient's blood pressure intraoperatively or during cardiopulmonary bypass. When asked about patients at risk for postoperative cerebral injury, 41.3% targeted a blood pressure goal >65 mmHg during cardiopulmonary bypass. The majority of responders (60.4%) who had access to institutional rates of postoperative stroke/cerebral injury had standard neuroprotective strategies in place. CONCLUSIONS: Our data indicate that approximately half of the respondents to this SCA survey do not use standardized guidelines/standard operating procedures for perioperative cerebral protection. The lack of standardized neuroprotective strategies during cardiac surgery may impact postoperative neurologic outcomes. Further investigations are warranted and should assess the association of standardized neuroprotective approaches and postoperative neurological outcomes.

Newborn Screening Pulse Oximetry to Detect Critical Congenital Heart Disease: A Follow-Up Survey of Current Practice at Army, Navy and Air Force Hospitals.

INTRODUCTION: The purpose of this study was to assess the evolution of newborn pulse oximetry screening (+POx) among Army, Air Force, and Naval military hospitals (MH), including prevalence, protocol use, quality assurance processes, access to echocardiography, and use of telemedicine. This is a follow-up from a prior study published in 2011. MATERIALS AND METHODS: An Internet-based questionnaire was forwarded to the chief pediatrician at MH worldwide which support newborn deliveries. Descriptive data were reported using percentages. Grouped responses, as applicable, were further compared using the chi-square test. A p-value < 0.05 was considered statistically significant. RESULTS: Seventy-eight percent (36/46) of MH supporting deliveries worldwide responded to the survey (17 Army hospitals, 11 Navy Hospitals, 8 Air Force hospitals). All responding hospitals utilize +POx, of which 94% endorsed protocol compliance with the American Academy of Pediatrics guidelines. Nine (25%) hospitals were located outside of the United States. Delivery volumes (infants per month) range between 1-49 (36%), 50-99 (28%), 100-199 (19%), and 200-300 (17%). Eleven hospitals reported regular review of +POx data, with most reviewing them monthly. Four MH share findings with state institutions. Ten hospitals either have a staff pediatric cardiologist or use tele-echocardiography for on-site evaluations. Ten hospitals are located greater than 60 miles from the nearest center with echocardiography capabilities. Of the five hospitals using tele-echocardiography, four confirmed critical congenital heart disease (CCHD) using this practice, and all five reported averting transfer of an infant using this technology. Of the 22 hospitals lacking the ability to obtain on-site echocardiography, 12 (55%) are interested in implementing a tele-echocardiography protocol. CONCLUSIONS: All responding MH use +POx, representing significant increase from the 30% of MH reporting use of +POx seven years ago. The majority of MH follow AAP +POx guidelines, and though most have providers review results prior to discharge, only one-third report periodic chart review for quality assurance. Most MH transfer infants with positive +POx results for evaluation due to a lack of on-site echocardiography. Tele-echocardiography was reported as a potential solution to diagnose or rule out CCHD. Over half of remaining hospitals without cardiologists are interested in using this technology to evaluate stable infants with positive CCHD screening.

Cost-Effectiveness Analysis of the DiagnOSAS Screening Tool Compared With Polysomnography Diagnosis in Dutch Primary Care.

STUDY OBJECTIVES: The growing recognition of obstructive sleep apnea (OSA) as a serious health condition, increasing waiting lists for sleep tests, and a high proportion of unnecessary referrals from general practice highlight the need for alternative diagnostic strategies for OSA. This study's objective was to investigate the cost-effectiveness of DiagnOSAS, a screening tool that strives to facilitate fast and well-informed referral to hospitals and sleep clinics for diagnosis, in The Netherlands. METHODS: A Markov model was constructed to assess cost-effectiveness in men aged 50 years. The diagnostic process of OSA was simulated with and without DiagnOSAS, taking into account the occurrence of hazardous OSA effects: car accidents, myocardial infarction, and stroke. The cost-effectiveness of "DiagnOSAS Strategy" and a "Rapid Diagnosis Scenario," in which time to diagnosis was halved, was assessed. RESULTS: Base case results show that, within a 10-year time period, DiagnOSAS saves €226 per patient at a negligible decrease (< 0.01) in quality-adjusted life-years (QALYs), resulting in an incremental cost-effectiveness ratio of €56,997/QALY. The "Rapid Diagnosis Scenario" dominates usual care (ie, is both cheaper and more effective). For a willingness-to-pay threshold of €20,000/QALY the probability that the "DiagnOSAS Strategy" and "Rapid Diagnosis Scenario" are cost-effective equals 91.7% and 99.3%, respectively. CONCLUSIONS: DiagnOSAS appears to be a cost-saving alternative for the usual OSA diagnostic strategy in The Netherlands. When DiagnOSAS succeeds in decreasing time to diagnosis, it could substantially improve health outcomes as well.

The Need to Apply Medical Device Informatics in Developing Standards for Safe Interoperable Medical Systems.

Medical device and health information technology systems are increasingly interdependent with users demanding increased interoperability. Related safety standards must be developed taking into account these systems' perspective. In this article, we describe the current development of medical device standards and the need for these standards to address medical device informatics. Medical device information should be gathered from a broad range of clinical scenarios to lay the foundation for safe medical device interoperability. Five clinical examples show how medical device informatics principles, if applied in the development of medical device standards, could help facilitate the development of safe interoperable medical device systems. These examples illustrate the clinical implications of the failure to capture important signals and device attributes. We provide recommendations relating to the coordination between historically separate standards development groups, some of which focus on safety and effectiveness and others focus on health informatics. We identify the need for a shared understanding among stakeholders and describe organizational structures to promote cooperation such that device-to-device interactions and related safety information are considered during standards development.

Anaesthesia and global health initiatives for children in a low-resource environment.

PURPOSE OF REVIEW: As the United Nations moves from Millennium Development Goals to Sustainable Development Goals, we find ourselves with the opportunity to influence the priority of global health initiatives. Previously, the global health community has failed to recognise the importance of access to safe, affordable surgery and developing the necessary specialities that support it as most of the funding focus had been on primary healthcare and infectious diseases. RECENT FINDINGS: Now the WHO is publishing guidelines to safe surgery and the Lancet Commission on Global Surgery has been launched. However, this is only the start; anaesthesia remains a forgotten speciality within the world of public and global health and there are still challenges in escalating surgery in low and middle-income countries to an acceptable level that is affordable and timely. SUMMARY: Although there is increased world interest in safe surgery and anaesthesia this has not yet been translated into a mandate that will compel countries to invest in improving levels of infrastructure, accessibility, manpower, and safety. A general anaesthetic remains a dangerous event in a child's life in resource-limited countries.

ASPMN survey--nurses' practice patterns related to monitoring and preventing respiratory depression.

The American Society for Pain Management Nursing convened a taskforce to develop guidelines on monitoring for opioid-induced sedation and respiratory depression. Part of the guideline development was the determination of nursing practice patterns related to monitoring and preventing respiratory depression during the administration of analgesics for pain. One hundred and forty-seven responses were received from 90 unique institutions across the United States. Monitoring adults with intermittent pulse oximetry while using intravenous patient-controlled analgesia (IV PCA) was 58%. Adults were monitored with continuous pulse oximetry by 25% of respondents. When using continuous epidural analgesia, 56% of patients were monitored intermittently, and 40% were monitored continuously. The use of end tidal CO2 (ETCO2) monitoring was much less, with 2.2% patients on epidural therapy, and 1.5% of institutions were using ETCO2 with IV PCA. The survey also included the location of the alarm, respiratory parameters for alarms, changes in procedures reported by institutions, and definitions of high-risk patients.

An assessment of the accuracy of pulse oximeters.

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% S(p)O(2). 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.

Pulse oximetry as a screening test for congenital heart defects in newborn infants: a test accuracy study with evaluation of acceptability and cost-effectiveness.

BACKGROUND: Screening for congenital heart defects (CHDs) relies on antenatal ultrasound and postnatal clinical examination; however, life-threatening defects often go undetected. OBJECTIVE: To determine the accuracy, acceptability and cost-effectiveness of pulse oximetry as a screening test for CHDs in newborn infants. DESIGN: A test accuracy study determined the accuracy of pulse oximetry. Acceptability of testing to parents was evaluated through a questionnaire, and to staff through focus groups. A decision-analytic model was constructed to assess cost-effectiveness. SETTING: Six UK maternity units. PARTICIPANTS: These were 20,055 asymptomatic newborns at ≥ 35 weeks' gestation, their mothers and health-care staff. INTERVENTIONS: Pulse oximetry was performed prior to discharge from hospital and the results of this index test were compared with a composite reference standard (echocardiography, clinical follow-up and follow-up through interrogation of clinical databases). MAIN OUTCOME MEASURES: Detection of major CHDs - defined as causing death or requiring invasive intervention up to 12 months of age (subdivided into critical CHDs causing death or intervention before 28 days, and serious CHDs causing death or intervention between 1 and 12 months of age); acceptability of testing to parents and staff; and the cost-effectiveness in terms of cost per timely diagnosis. RESULTS: Fifty-three of the 20,055 babies screened had a major CHD (24 critical and 29 serious), a prevalence of 2.6 per 1000 live births. Pulse oximetry had a sensitivity of 75.0% [95% confidence interval (CI) 53.3% to 90.2%] for critical cases and 49.1% (95% CI 35.1% to 63.2%) for all major CHDs. When 23 cases were excluded, in which a CHD was already suspected following antenatal ultrasound, pulse oximetry had a sensitivity of 58.3% (95% CI 27.7% to 84.8%) for critical cases (12 babies) and 28.6% (95% CI 14.6% to 46.3%) for all major CHDs (35 babies). False-positive (FP) results occurred in 1 in 119 babies (0.84%) without major CHDs (specificity 99.2%, 95% CI 99.0% to 99.3%). However, of the 169 FPs, there were six cases of significant but not major CHDs and 40 cases of respiratory or infective illness requiring medical intervention. The prevalence of major CHDs in babies with normal pulse oximetry was 1.4 (95% CI 0.9 to 2.0) per 1000 live births, as 27 babies with major CHDs (6 critical and 21 serious) were missed. Parent and staff participants were predominantly satisfied with screening, perceiving it as an important test to detect ill babies. There was no evidence that mothers given FP results were more anxious after participating than those given true-negative results, although they were less satisfied with the test. White British/Irish mothers were more likely to participate in the study, and were less anxious and more satisfied than those of other ethnicities. The incremental cost-effectiveness ratio of pulse oximetry plus clinical examination compared with examination alone is approximately £24,900 per timely diagnosis in a population in which antenatal screening for CHDs already exists. CONCLUSIONS: Pulse oximetry is a simple, safe, feasible test that is acceptable to parents and staff and adds value to existing screening. It is likely to identify cases of critical CHDs that would otherwise go undetected. It is also likely to be cost-effective given current acceptable thresholds. The detection of other pathologies, such as significant CHDs and respiratory and infective illnesses, is an additional advantage. Other pulse oximetry techniques, such as perfusion index, may enhance detection of aortic obstructive lesions. FUNDING: The National Institute for Health Research Health Technology programme.

Sensitivity and specificity of telemedicine-based long-term pulse-oximetry in comparison with cardiorespiratory polygraphy and polysomnography in patients with obstructive sleep apnoea syndrome.

We investigated the feasibility of night-time pulse-oximetry telemedicine. We compared polysomnography (PSG) as the gold standard with simultaneously recorded pulse-oximetry from a wrist pulse-oximeter. The results were evaluated by a sleep specialist and compared with outpatient polygraphy. A total of 135 consecutive patients (mean age 55 years, mean body mass index 31.6 kg/m(2)) were studied. Patients with minor, moderate and severe PSG findings were grouped together and compared to those without PSG findings; the resulting sensitivity was 1 and specificity 0.35. In addition, patients with and without minor PSG findings were grouped together and compared to those with moderate and severe PSG findings; the resulting sensitivity was 0.66 and the specificity was 0.98. The receiver operating characteristic (ROC) of telemedically-evaluated oximetry was superior to that of outpatient polygraphy. In contrast, the automatic assessment of severity based on the Oxygen Desaturation Index was unsatisfactory. For patients suspected of sleep related breathing disorders (SRBD), telemedically-evaluated pulse-oximetry is able to identify those who should be referred to a sleep laboratory for definitive diagnosis and treatment. The technique appears to be suitable for first screening in all patients at risk for SRBD.

Role of pulse oximetry in examining newborns for congenital heart disease: a scientific statement from the American Heart Association and American Academy of Pediatrics.

BACKGROUND: The purpose of this statement is to address the state of evidence on the routine use of pulse oximetry in newborns to detect critical congenital heart disease (CCHD). METHODS AND RESULTS: A writing group appointed by the American Heart Association and the American Academy of Pediatrics reviewed the available literature addressing current detection methods for CCHD, burden of missed and/or delayed diagnosis of CCHD, rationale of oximetry screening, and clinical studies of oximetry in otherwise asymptomatic newborns. MEDLINE database searches from 1966 to 2008 were done for English-language papers using the following search terms: congenital heart disease, pulse oximetry, physical examination, murmur, echocardiography, fetal echocardiography, and newborn screening. The reference lists of identified papers were also searched. Published abstracts from major pediatric scientific meetings in 2006 to 2008 were also reviewed. The American Heart Association classification of recommendations and levels of evidence for practice guidelines were used. In an analysis of pooled studies of oximetry assessment performed after 24 hours of life, the estimated sensitivity for detecting CCHD was 69.6%, and the positive predictive value was 47.0%; however, sensitivity varied dramatically among studies from 0% to 100%. False-positive screens that required further evaluation occurred in only 0.035% of infants screened after 24 hours. CONCLUSIONS: Currently, CCHD is not detected in some newborns until after their hospital discharge, which results in significant morbidity and occasional mortality. Furthermore, routine pulse oximetry performed on asymptomatic newborns after 24 hours of life, but before hospital discharge, may detect CCHD. Routine pulse oximetry performed after 24 hours in hospitals that have on-site pediatric cardiovascular services incurs very low cost and risk of harm. Future studies in larger populations and across a broad range of newborn delivery systems are needed to determine whether this practice should become standard of care in the routine assessment of the neonate.

Accuracy of clinical assessment of paediatric obstructive sleep apnoea in two English centres.

OBJECTIVES: To ascertain the sensitivity and specificity of clinical diagnosis of obstructive sleep apnoea in children, and to determine if a published clinical algorithm identifies those at high risk of post-adenotonsillectomy complications. METHOD: Sixty-seven children aged three to eight years underwent clinical assessment and overnight polysomnography. RESULTS: Polysomnography detected a significant apnoea-hypopnoea index (i.e. > or =5, indicating significant obstructive sleep apnoea) in 13 (43 per cent) children with a clinical diagnosis of obstructive sleep apnoea and in six (19 per cent) children with no such diagnosis. The sensitivity of clinical assessment was 68.4 per cent and the specificity 59.5 per cent. The post-operative risk algorithm failed to identify any high risk children, although in actuality seven had severe obstructive sleep apnoea confirmed by polysomnography. CONCLUSIONS: This study of two English centres confirms that the clinical diagnostic process for obstructive sleep apnoea is reasonably insensitive and has low specificity. The studied algorithm discriminated poorly between children with and without severe obstructive sleep apnoea. Realistic diagnostic screening guidelines for paediatric sleep apnoea are overdue in the UK, where access to polysomnography is limited.

Pulse oximetry index: a simple arterial assessment for patients with venous disease.

OBJECTIVE: To provide additional safety data comparing ankle brachial pressure index (ABPI) and pulse oximetry (Lanarkshire Oximetry Index, LOI) as measures of arterial circulation in patients with venous disease of the leg. METHOD: A total of 107 (195 legs) attending hospital leg ulcer clinics participated in this prospective open study. We attempted to measure brachial and foot arterial pressures in all patients using both the handheld Doppler method (ABPI) and pulse oximeter method (LOI). Features of patients with limbs in which either the ABPI or LOI could not be assessed were documented. ABPI and LOI values were compared, and agreement between the two assessment methods was assessed. RESULTS: We found the LOI measurement to be a simpler technique than Doppler ABPI measurement, with an endpoint less prone to the subjective variability associated with the Doppler method. Of the 195 legs assessed,we obtained LOI in 10 in which an ABPI could not be recorded. LOI could not be recorded in only one leg. There was a linear association (p<0.001) and fair agreement (kappa=0.303) between LOI and ABPI in the 184 legs in which both ratios could be measured. There was no evident tendency for LOI to read either low or high compared with ABPI. CONCLUSION: Pulse oximetry LOI is a simple alternative to Doppler ABPI in the screening of patients for arterial disease that could be a contraindication to, or require modification of, compression therapy. It can be measured in some legs that cannot be assessed by Doppler ultrasound.

Pulse oximetry knowledge and its effects on clinical practice.

AIM: to explore literature pertaining to registered nurses' and/or doctors' knowledge in relation to the pulse oximetry in clinical practice. BACKGROUND: pulse oximeters provide non-invasive readings of both pulse rate and peripheral oxygen saturation, leading to quick identification of potential/actual problems. Because of this, clinicians, like nurses, may become too dependent on it, neglecting other aspects of the holistic assessment process. METHODS: a literature search was carried out between 1980 and 2006, with much of the data skewed towards 1994-2006. As the central focus was to be on pulse oximetry knowledge of nurses and/or doctors, articles included had to contain a central theme addressing this. Other criteria for inclusion were links between pulse oximetry and knowledge in clinical practice, nurses and/or doctors as participants in studies addressing this, as well as the clinical competency in relation to the device. CONCLUSION: improving knowledge may not necessarily be the answer in improving clinical competency. Future research will need to be carried out to measure the connection between knowledge and competency and to use that as a basis for education and training.

Hemoximetry as the "gold standard"? Error assessment based on differences among identical blood gas analyzer devices of five manufacturers.

BACKGROUND: The calibration and testing procedures of a pulse oximeter with arterial blood samples from healthy subjects are based on reference values from the hemoximeter. There are no tests to identify the accuracy of the reference devices. Because of this limitation and since the true values of oxygen saturation (sO2 in %) in blood samples were not known, we used the differences between two identical devices, A and B, for error assessment. METHODS: Two identical devices, A and B, from five leading manufacturers were investigated. Seventy-two arterial blood samples from 12 healthy volunteers at three different levels of saturation between 100% and 70% sO2 were randomly evaluated by the test systems. RESULTS: The observed differences (Delta) between Devices A and B, as a measure for the error of the hemoximeters, increased significantly with all manufacturers from level 97 (Deltamin, -0.9%; Deltamax, 2.6%) to 85 (Deltamin, -2.4%; Deltamax, 4.3), this effect was even stronger between levels 97 and 75 (Deltamin, -4.6%; Deltamax, 4.3%). A variance proportion analysis revealed the concentration of the reduced hemoglobin as the main error source for sO2 measurements. Independent from the sO2 levels there were also significant differences for the carboxy hemoglobin concentration in the range of 0%-4% and for the methemoglobin concentration in the range of 0%-1%. CONCLUSIONS: The variance of sO2 measurements between identical devices increased significantly when saturation decreased from the normal level of 97% to the hypoxemic levels of 85% and 75%.