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PubMed2001

Pulse oximetry in sickle cell anemia.

OBJECTIVES: To determine whether pulse oximetry is accurate and if it correlates with arterial blood gas saturation in pediatric patients with sickle cell anemia. DESIGN: Prospective, comparative study using a convenience sample of patients with sickle cell anemia who had simultaneous arterial blood gas sampling and pulse oximetry. SETTING: Children's Memorial Hospital, a large tertiary care pediatric hospital in Chicago, IL. Patients selected from the emergency department and the pediatric intensive care unit. PATIENTS: Twenty-four consecutive patients with sickle cell anemia who had simultaneous arterial blood gas sampling and pulse oximetry. MEASUREMENTS AND MAIN RESULTS: Twenty-four patients had a total of 70 simultaneous pulse oximeter and blood gas pair samples. Each patient's initial pulse oximeter/blood gas pair was used in the statistical analysis. Three patients had venous samples and were excluded from comparison, leaving 21 arterial blood gas/pulse oximeter pairs for analysis. The pulse oximeter correlated well with the cooximeter-measured arterial saturation (r(2) =.74). The pulse oximeter significantly underestimated saturation by a mean of -1.6% (95% confidence interval, -0.3 to -3; p =.03). CONCLUSIONS: Pulse oximetry correlates well with cooximeter-measured saturation in patients with sickle cell anemia. Pulse oximetry significantly underestimates true arterial saturation, but the bias is clinically insignificant. Pulse oximetry can be used reliably to estimate the arterial oxygen saturation in patients with sickle cell anemia.

Adolescent↗
PubMed1991

The clinical utility of pulse oximetry in the pediatric emergency department setting.

Pulse oximetry provides a noninvasive, painless, accurate, and rapid method for measuring arterial oxygen saturation (SaO2). It has been shown to be valuable in anesthesia and critical care and recently has been used extensively in the outpatient setting. As is often the case with new technologies, little has been published on the basic issues of reliability, reproducibility, and effect on patient care. This prospective clinical study evaluated the basic principles of pulse oximetry in the pediatric emergency department setting and tested the hypotheses that pulse oximetry SaO2 measurements are reliable and provide valuable information, in addition to clinical and laboratory data which affect patient assessment and management. One hundred twenty patients were enrolled in phase 1 and 437 in phase 2 of the study. Pulse oximetry readings were reproducible with an intraclass correlation of 0.87. SaO2 measurements changed the assessed degree of illness in 188 (53%) patients; 47 (13%) were felt to be more ill and 130 (37%) to be less ill than at initial assessment. Sixty-nine (17%) patients were identified in whom SaO2 readings changed management plans; 27 (8%) were managed more aggressively (intubation, surgery, or admission), while 40 (11%) were managed less aggressively (discharged). In three cases, pulse oximetry was instrumental in the diagnosis of a serious illness. The results from this study indicate that pulse oximetry SaO2 readings are stable and reproducible and provide information which impacts significantly on patient assessment and management.

Adolescent↗
PubMed1995

From oxygen content to pulse oximetry: completing the picture in the newborn.

In recent years clinicians caring for sick preterm infants have come to depend on pulse oximetry to avoid hyperoxia, which means assuming saturation values for critical levels of oxygen tension. This prediction is made difficult by the shape of the haemoglobin-oxygen dissociation curve at critical values for arterial pO2 and by the effects of changes in acid-base balance on p50. Combined blood gas and co-oximetry measurements can be used to determine critical limits for pulse oximetry. Fetal haemoglobin has slightly different light absorption characteristics from adult haemoglobin. To adjust for this, adult and fetal matrices are available in the OSM 3 HEMOXIMETER (Radiometer Medical A/S, Denmark) but the measurement requires an extra preliminary step to estimate fetal haemoglobin concentration. We sought to determine the importance of this extra procedure for measuring the saturation of newborn blood, and to determine whether the adult or fetal mode should be used for determining saturation for comparison with pulse oximeters. We measured the effect of the correction for fetal haemoglobin by obtaining absorbances from the co-oximeter and multiplying them by the adult and fetal matrices. We demonstrated that, at 90% saturation, failure to use the fetal correction in the presence of high levels of fetal haemoglobin result in a 4% overestimate of saturation, with resultant underestimation of the safe range for pulse oximetry. Published values for extinction coefficients for fetal and adult blood at wavelengths used by pulse oximeters are inconsistent, but it appears that fetal haemoglobin does not bias pulse oximetry readings. Determining saturation limits by co-oximetry for use with pulse oximeters in preterm infants requires the description of the haemoglobin-oxygen dissociation curve with the correction for fetal haemoglobin.

Acid-Base Equilibrium↗
PubMed1996

Oximetry for amniotic fluid embolism detection in mini-pigs: tail or snout?

The continuous, non-invasive real-time monitoring of arterial oxygenation (pulse oximetry) has become a standard of care in both human and veterinary medicine. It allows reliable, simple and inexpensive assessment of the arterial oxygenation status. In pigs, commonly used sites for oximetry-probe placement are the ear, snout or tongue, while more recently the 'pig-tail oximetry' has been suggested. In a study regarding the coagulation system during amniotic fluid embolism (AFE) in mini-pigs, we compared tail and snout for oximetry-probe placement and compared them with the 'gold standard': blood-gas analysis (BGA). In both the AFE group and the control group, the tail measurements were slightly lower and the snout measurements were slightly higher than the BGA results. In the experimental model used, both tail and snout measurements were able to detect a temporary desaturation immediately after amniotic fluid embolism (AFE). Blood-gas analysis (BGA) performed on blood drawn from a large artery missed the event. Clinically, there is no significant difference between snout and tail as oximetry-probe placement sites: both are reliable oximetry sites in mini-pigs.

Animals↗
PubMed1997

Effect of location of the sensor on reflectance pulse oximetry.

OBJECTIVE: The influence of the location of the sensor on reflectance pulse oximetry during fetal monitoring in labour was investigated using the newborn infant as a model. METHODS: Seven healthy infants were studied between 19 and 48 hours after term delivery. Recordings of reflectance pulse oximetry were obtained from eight different sites on the infant's head. The relative changes in red to infrared light (R/IR) were determined. In pulse oximetry R/IR values are converted to arterial oxygen values by means of an empirically derived calibration curve. RESULTS: Significantly lower R/IR values were found at the forehead compared with the fontanelle, the parietal and occipital position, and the temporal area. Conversion to oxygen saturation values revealed a difference of up to 13.4% in oxygen saturation between the forehead and the occipital area. CONCLUSION: Assuming that the arterial blood oxygen saturation did not change substantially, our findings indicate that in reflectance pulse oximetry there is no unique relation between R/IR and arterial oxygen saturation. The differences in reflectance pulse oximetry at the various sites are explained by differences in optical properties (scattering and absorption) of the tissue underneath the sensor. These will affect the red and infrared light reaching the detectors in a different way, and consequently R/IR changes. Because during intrapartum monitoring exact positioning of the sensor on the fetal head is usually impossible, the accuracy of fetal reflectance pulse oximetry is impaired.

Fetal Monitoring↗
PubMed1997

Does pulse oximetry reliably detect aspiration in dysphagic stroke patients?

BACKGROUND AND PURPOSE: The aim of the present study was to examine the value of pulse oximetry in the diagnosis of aspiration by comparing it with the gold standard, videofluoroscopy, by use of a prospective, controlled, single-blind study design. METHODS: Pulse oximetry was performed simultaneously with videofluoroscopy in 54 consecutive dysphagic stroke patients. Oxygen saturation measurements were taken before the video-fluoroscopic examination (baseline), on swallowing and continuously for 2 minutes after swallowing, and 10 minutes later. RESULTS: Pulse oximetry reliably predicted aspiration or lack of it in 81.5% of cases. The predictive value of the test was low in patients aged > or = 65 years and possibly those with chronic lung disease. One smoker also had a false-negative pulse oximetry result, ie, normal oxygen saturation despite radiological evidence of aspiration. CONCLUSIONS: Pulse oximetry is a reliable method of diagnosis of aspiration in most dysphagic patients. However, careful interpretation of pulse oximetry data is necessary in older subjects, possibly those with chronic pulmonary disease, and smokers. The method is noninvasive, simple, and quick, and can be used routinely in the clinical assessment of dysphagic patients.

Adult↗
PubMed1992

Observer agreement for respiratory signs and oximetry in infants hospitalized with lower respiratory infections.

To determine observer agreement for a clinical score and oximetry in lower respiratory infection in children less than 2 yr of age, a convenience sample of 56 infants hospitalized with bronchiolitis or pneumonia was assessed independently by two observers. A total of 12 infants had chronic lung disease of prematurity or congenital heart disease. Infants in whom oxygen supplementation could not be discontinued for at least 5 min were excluded. A severity score was assigned for each of four categories (respiratory rate, retractions, wheeze, and general appearance). A total for each patient was obtained by summing the score for each category. Oxygen saturation was measured using a Nellcor oximeter. Agreement beyond chance was measured using the kappa statistic. The relationship between observers for total score and oximetry and the mean total score and mean oximetry value for each patient was expressed as a Pearson correlation coefficient. A total of 56 infants and children were studied: 2 had pneumonia, 11 had an exacerbation of pulmonary signs and symptoms with their underlying cardiac or pulmonary disease, and 43 had bronchiolitis. Kappa was 0.48 for general assessment, 0.38 for respiratory rate, 0.31 for wheeze, and 0.25 for retractions. All values were statistically significantly greater than 0 at p less than 0.01. Correlations for total score and for oximetry were 0.68 and 0.88, respectively. The median difference between oximetry readings was 1. The correlation coefficient between total score and oximetry was -0.04. The limited agreement for clinical signs makes comparison of patient illness severity between studies difficult.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchiolitis↗
PubMed1998

Pulse oximetry in severe carbon monoxide poisoning.

STUDY OBJECTIVES: To evaluate the accuracy and quantitate the error of pulse oximetry measurements of arterial oxygenation in patients with severe carbon monoxide (CO) poisoning. DESIGN: Retrospective review of patient clinical records. SETTING: Regional referral center for hyperbaric oxygen therapy. PATIENTS: Thirty patients referred for treatment of acute severe CO poisoning who demonstrated carboxyhemoglobin (COHb) levels >25%, with simultaneous determinations of arterial hemoglobin oxygen saturation by pulse oximetry (SpO2) and arterial blood gas (ABG) techniques. MEASUREMENTS AND RESULTS: COHb levels and measurements of arterial oxygenation from pulse oximetry, ABG analysis, and laboratory CO oximetry were compared. SpO2 did not correlate with COHb levels. SpO2 consistently overestimated the fractional arterial oxygen saturation. The difference between arterial hemoglobin oxygen saturation (SaO2) calculated from ABG analysis and SpO2 increased with increasing COHb level. CONCLUSIONS: Presently available pulse oximeters overestimate arterial oxygenation in patients with severe CO poisoning. An elevated COHb level falsely elevates the SaO2 measurements from pulse oximetry, usually by an amount less than the COHb level, confirming a prior observation in an animal model. Accurate assessment of arterial oxygen content in patients with CO poisoning can currently be performed only by analysis of arterial blood with a laboratory CO-oximetry.

Adult↗
PubMed1999

Use of pulse oximetry to recognize severity of airflow obstruction in obstructive airway disease: correlation with pulsus paradoxus.

STUDY OBJECTIVES: The purpose of this cross-sectional study was to confirm the observation that pulse oximetry tracing correlates with pulsus paradoxus, and is therefore a measure of the severity of air trapping in obstructive airway disease. DESIGN: Cross-sectional survey. SETTING: The ICU in a tertiary care academic hospital. PATIENTS: Twenty-six patients consecutively admitted to the ICU with obstructive airway disease, either asthma or COPD. MEASUREMENTS AND RESULTS: Forty-six percent of the study patients required mechanical ventilation, and 69% had an elevated pulsus paradoxus. We defined the altered pulse oximetry baseline tracing as the respiratory waveform variation (RWV). The RWV was measured in numerical form as the change in millimeters from the baseline. Pulsus paradoxus was significantly correlated with the RWV of the pulse oximetry tracing (p < 0.0001). An analysis of the respiratory variations in the pulse oximetry waveforms in obstructive lung disease patients reflects the presence and degree of auto-positive end-expiratory pressure (auto-PEEP; p < 0.0001). CONCLUSIONS: We describe the characteristic alterations in the pulse oximetry tracings that occur in the presence of pulsus paradoxus and auto-PEEP. Since pulse oximetry is available universally in ICUs and emergency departments, it may be a useful noninvasive means of continually assessing pulsus paradoxus and air trapping severity in obstructive airway disease patients.

Adult↗
PubMed2002

Detection of pulsus paradoxus associated with large pericardial effusions in pediatric patients by analysis of the pulse-oximetry waveform.

OBJECTIVE: To determine whether analysis of the pulse-oximetry waveform can be useful in detecting the pulsus paradoxus associated with large pericardial effusions in pediatric patients. METHODS: A retrospective review of charts of 8 pediatric patients (age range: 5-19 years) who had echocardiographic evidence of large pericardial effusion, subsequently underwent pericardiocentesis, and had pulse-oximetry waveform tracings obtained before and after pericardiocentesis within an 18-month period was conducted in 2 tertiary-care pediatric intensive care units. We analyzed the pulse-oximetry waveform tracings for the presence of a pulsus paradoxus. Other abstracted data included clinical evidence of tamponade, echocardiographic findings, and the volume of pericardial fluid aspirated. RESULTS: Before pericardiocentesis, a decrease in the highest value of the upper plethysmographic peak of the pulse-oximetry waveform was observed during inspiration in each patient. Echocardiographic evidence of large pericardial effusion with compromised cardiac filling was also present in each patient. Only 6 of these patients had clinical evidence of cardiac tamponade at that time, 4 with a documented pulsus paradoxus using standard methods of blood pressure analysis. After pericardiocentesis, the inspiratory fall in the highest value of the upper plethysmographic peak of the pulse-oximetry waveform lessened in every patient. Echocardiography documented a decrease in the size of the effusion and resolution of the compromised cardiac filling in every patient. CONCLUSIONS: Analysis of pulse-oximetry waveforms may be a widely available, easily interpretable, and reliable method of detecting the pulsus paradoxus associated with large pericardial effusions in pediatric patients.

Adolescent↗
PubMed1984

Assessment of perfusion in the diabetic foot by regional transcutaneous oximetry.

Regional transcutaneous oximetry is a new, noninvasive diagnostic technique for the investigation of peripheral vascular disease (PVD) that uses differences in limb and trunk transcutaneous PO2 to assess the adequacy of local perfusion. The application of such measurements would be of great importance in diabetes, in which limb ischemia is commonly difficult to assess. A group of diabetic subjects with symptomatic PVD was studied with regional oximetry, Doppler-assisted blood pressure measurements, and arteriography. Doppler studies correlated poorly to symptom grade and angiographic data, while oximetry clearly demonstrated limb hypoxia under the functional conditions appropriate to the patients' clinical symptomatology. The superiority of oximetry to Doppler studies was highly significant (X2 = 12.64, P less than 0.001). Regional transcutaneous oximetry should therefore be the noninvasive diagnostic test of choice in the initial evaluation of the diabetic limb for PVD. Because of its dependence on the adequacy of local oxygenation, transcutaneous oximetry is a powerful tool for investigation of the pathophysiology of PVD and will, in the future, have wide-ranging applications to the diagnosis and therapy of PVD.

Aged↗
PubMed1991

Pulse oximetry monitoring outside the intensive care unit: progress or problem?

OBJECTIVE: To evaluate the use of continuous pulse oximetry monitoring in general care units. DESIGN: Hemoglobin oxygen saturation data collected prospectively by use of pulse oximetry with concurrent review of the medical record. SETTING: General medical-surgical nursing units in a large, tertiary care university hospital. PATIENTS: Forty patients on two nursing units monitored with continuous, bedside pulse oximetry at the request of their primary physicians. MEASUREMENTS: All patients had continuous pulse oximetry monitoring. A research associate visited the bedside two or three times daily and recorded saturation compared with time data from the previous 8.75 hours. Patients were studied for 36 hours or until pulse oximetry monitoring was discontinued. Episodes of desaturation were counted. Patient charts were reviewed for documentation of desaturation in either nursing or physician notes. Orders adjusting oxygen therapy or other respiratory therapy within 12 hours of any desaturation episode were also recorded. MAIN RESULTS: Thirty of the 40 patients (75%) had at least one episode of desaturation to less than 90%; 23 (58%) had at least one episode to less than 85%. Desaturation episodes were documented in nursing notes for only 33% of those patients who desaturated to less than 90% and in physician notes in only 7% of cases. Changes in respiratory therapy were ordered in 20% of patients who desaturated to less than 90% and in only 26% who desaturated to less than 85%. CONCLUSIONS: Despite their repeated occurrence, episodes of hypoxemia were rarely documented in either nursing or physician notes. Further, even in patients who had episodic desaturation, pulse oximetry monitoring had little effect on changes in physician-directed respiratory care.

Adult↗
PubMed1999

Pulse oximetry.

Pulse oximetry is one of the most commonly applied technologies in acute and critical care. It has the potential to continuously monitor pulmonary function, avoid unnecessary blood gases, and alert clinicians to hypoxemic events that are not readily apparent by physical assessment. Due to these advantages, pulse oximetry has a firm place in health care. Unfortunately, pulse oximetry will not usually have a major impact on reducing hospital resources. In addition, oximetry has the potential to be misused owing to its widespread application. In order to obtain the maximum benefits from this technology, clinicians must be educated about the strengths and limitations of oximetry. If this education effectively changes clinicians' behavior, pulse oximetry will provide an excellent clinical advantage in patient assessment as well as moderate cost benefits.

Aged↗
PubMed2003

Understanding of pulse oximetry among hospital staff.

AIM: To assess the level of understanding of pulse oximetry in a hospital setting and identify training needs. METHODS: Twenty nine nurses and 34 doctors anonymously completed a questionnaire survey previously used by researchers in Exeter, UK. Respondents were required to explain the basic principles of pulse oximetry and demonstrate an understanding of the physiological factors limiting its accuracy. They were asked to apply their knowledge in different clinical scenarios. RESULTS: A higher proportion of nurses than doctors demonstrated an awareness of the physiological limitations of pulse oximetry. The majority of respondents correctly identified normal ranges for adult patients. Twenty nine per cent of respondents did not know how a pulse oximeter worked. Respondents failed to recognise the clinical implications of low oxygen saturations in many of the hypothetical scenarios. Only 16% of respondents had received any formal training in the use of pulse oximetry, with 65% identifying a need for more training. CONCLUSIONS: Medical and nursing staff at Christchurch Hospital have a good understanding of pulse oximetry. A higher proportion of participants were aware of checking vital signs when the oximeter reading was unreliable, than in the original UK study cohort. A need was identified for further education in this core technique. Staff training may increase the clinical value of pulse oximetry.

Adult↗
PubMed1993

Pulse oximetry and factors associated with hemoglobin oxygen desaturation in children with sickle cell disease.

The observation of low transcutaneous arterial oxygen saturation (SaO2) in otherwise well sickle cell patients has lead to questions about the interpretation of pulse oximetry values in these patients. We undertook a prospective study of children with sickle cell disease to (1) determine the prevalence of, and factors associated with, low transcutaneous SaO2 in clinically well patients, (2) develop an algorithm for the use of pulse oximetry in acutely ill patients, and (3) assess the accuracy of pulse oximetry in these patients. Eighty-six clinically well children with hemoglobin (Hb) SS had a lower mean transcutaneous SaO2 than 22 Hb SC patients and 10 control subjects (95.6% v 99.1% v 99.0%, respectively; p < .001). In Hb SS patients, a history of acute chest syndrome and age greater than 5 years were associated with lower transcutaneous SaO2 (mean 93.8% for those with a history of acute chest syndrome v 97.8% for those without a history of acute chest syndrome, and 94.0% for patients > 5 years old v 97.2% for those < or = 5 years old; P < .001). These associations were not seen in Hb SC patients. During acute illness, Hb SS patients with acute chest syndrome had transcutaneous SaO2 values that were less than 96% and at least 3 points lower than measurements made when they were well. A nomogram was designed to aid in the interpretation of transcutaneous SaO2 in acutely ill Hb SS patients when a comparison value is not available. The accuracy of pulse oximetry was shown by the correlation between SaO2 measured by pulse oximetry and calculated by using the patient's oxygen dissociation curve and PaO2 (r = .97). This study provides evidence that Hb oxygen desaturation is not a universal finding among children with sickle cell disease and identifies factors associated with Hb oxygen desaturation. We conclude that pulse oximetry may be useful to assess whether progressive pulmonary dysfunction begins at an early age in Hb SS patients, and to assess acutely ill patients for the presence of hypoxemia associated with acute chest syndrome.

Anemia, Sickle Cell↗
PubMed1994

A study of pediatric house staff's knowledge of pulse oximetry.

OBJECTIVE: Pulse oximetry is widely used to measure oxygen saturation in inpatient and outpatient settings. As with any medical technology, competence in interpretation and application of the data is essential for patient care. We therefore undertook a study to quantify pediatric house staff's knowledge of pulse oximetry and their ability to interpret the information. METHODS: A 16-item multiple choice questionnaire (6 demographic, 10 knowledge) was developed to assess knowledge of pulse oximetry. The questionnaire was administered to a total of 134 pediatric house staff from five medical school-affiliated residency programs in New York City. RESULTS: The mean test score and standard deviation was 64.3% +/- 1.9, with a range of 10% to 100%. Regarding three questions related to the knowledge of the oxyhemoglobin deviation curve, only 17% of the the respondents answered all three questions correctly. In three questions pertaining to the accuracy of the pulse oximeter, 36% of the respondents answered all questions correctly. Forty-three percent of the house staff believed that training in the use of pulse oximetry was inadequate. CONCLUSIONS: The results showed that there is marked variability in pediatric house staff's knowledge of all aspects of pulse oximetry. This could contribute to patient morbidity. We suggest that medical schools and residency programs place more emphasis on teaching the principles and applications of pulse oximetry and the oxyhemoglobin dissociation curve.

Clinical Competence↗
PubMed1993

History and recent developments in pulse oximetry.

To honour Siggaard-Andersen's role in the development of accurate blood oximetry, this paper was abstracted from a recent review and survey of over 750 publications of pulse oximetry. Pulse oximetry usage has become nearly universal during anesthesia and related critical care in the developed world during the last decade. More than 35 manufacturers offer pulse oximetry. Costs of some have fallen to less than $1500 per device, with no necessary on-going charges. Pulse oximeters are remarkable: Accuracy is +/- 2% down to 70% SaO2 without any user calibration, no drift, instantaneous readout, and almost no maintenance or safety problems. New developments include better understanding of management of premature infants, beginning use for fetal SaO2 during labor, sophisticated methods of ignoring motion artifacts and room light interference, and awareness of sources of error. Oximetry use has caused anesthesiologists and most critical care physicians to become far more able to avoid severe hypoxia in patients. Malpractice insurance rates for anesthesiologists have dropped in the USA, and other evidence suggests, although failing to prove, that anesthesia and critical care is now safer, probably due to oximetry.

Adult↗
PubMed1995

Comparing fetal pulse oximetry with scalp pH.

OBJECTIVE: To determine whether pulse oximetry has the potential to replace scalp blood pH sampling in infants with abnormal cardiotocographs. STUDY DESIGN: The average scalp oximetry reading in labor recorded with an experimental N400 system was compared with fetal scalp blood pH. RESULTS: The average oximetry readings were unrelated to the pH of aerobically sampled fetal scalp blood. There was no subgroup of acidemic infants with a low oximetry reading. CONCLUSION: Pulse oximetry readings with present technology do not reflect scalp pH. The equipment is improving, but at this time pulse oximetry is not a simple alternative for scalp capillary blood sampling.

Blood Gas Analysis↗