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PubMed2005

Black magic and EPR oximetry: from lab to initial clinical trials.

EPR oximetry is a technique that can make repeated non-invasive measurements of the PO2 in tissues. To extend the application of EPR oximetry to humans, India ink is the probe of choice because appropriate India inks have EPR signals whose line widths are sensitive to changes in oxygen concentrations, and, most importantly, India ink already has been used extensively in humans as a marker in the skin, lymphatics, various organs during surgery, tumors, and for decoration as tattoos. We have developed an India ink that has good sensitivity to oxygen, high stability in tissues, good signal intensity, and minimal toxicity. In this article we describe the various properties of this India ink, results obtained from our animal experiments, and our first preliminary clinical results, which are part of the first systematic clinical use of EPR oximetry. The clinical results indicate that it is possible to do repeated measurements over several months and probably years after the injection of the ink, indicating that long-term follow-up studies are feasible. We are very encouraged with these results and are confident that EPR oximetry using India ink will be a non-invasive, fast, and reliable technique for pO2 measurements in clinical studies.

Animals↗
PubMed1987

Pulse oximetry and transcutaneous oxygen tension for detection of hypoxemia in critically ill infants and children.

We tested the performance of transcutaneous oxygen monitoring (TcPO2) and pulse oximetry (tcSaO2) in detecting hypoxia in critically ill neonatal and pediatric patients. In 54 patients (178 data sets) with a mean age of 2.4 years (range 1 to 19 years), arterial saturation (SaO2) ranged from 9.5 to 100%, and arterial oxygen tension (PaO2) from 16.4 to 128 mmHg. Linear correlation analysis of pulse oximetry vs measured SaO2 revealed an r value of 0.95 (p less than 0.001) with an equation of y = 21.1 + 0.749x, while PaO2 vs tcPO2 showed a correlation coefficient of r = 0.95 (p less than 0.001) with an equation of y = -1.04 + 0.876x. The mean difference between measured SaO2 and tcSaO2 was -2.74 +/- 7.69% (range +14 to - 29%) and the mean difference between PaO2 and tcPO2 was +7.43 +/- 8.57 mmHg (range -14 to +49 mmHg). Pulse oximetry was reliable at values above 65%, but was inaccurate and overestimated the arterial SaO2 at lower values. TcPO2 tended to underestimate the arterial value with increasing PaO2. Pulse oximetry had the best sensitivity to specificity ratio for hypoxia between 65 and 90% SaO2; for tcPO2 the best results were obtained between 35 and 55 mmHg PaO2.

Adolescent↗
PubMed1987

Is pulse oximetry reliable in detecting hyperoxemia in the neonate?

We tested the hypothesis that hyperoxemia defined as arterial PO2 above 12 kPa can be detected by pulse oximetry using 95% oxygen saturation as the upper limit. Thirty artificially ventilated neonates with an indwelling arterial catheter were studied registrating transcutaneous oxygen saturation (Ohmeda Biox 3700 Pulse Oximeter) and transcutaneous PO2 continuously during a 4-hour period and measuring arterial oxygen saturation and PO2 intermittently. 46 episodes of arterial hyperoxemia were observed. Pulse oximetry had a sensitivity of 30%, detecting 14 of these 46 hyperoxemic episodes, and a specificity of 93%. The accuracy for separating hyperoxemia from normoxemia by pulse oximetry could be improved by shifting the cut-off point from 95% to 92%. With this optimal cut-off point sensitivity was 70% and specificity 62%. We conclude that pulse oximetry is not reliable for detection of hyperoxemia.

Blood Gas Monitoring, Transcutaneous↗
PubMed1987

Pulse oximetry and transcutaneous oxygen tension in hypoxemic neonates and infants with bronchopulmonary dysplasia.

The reliability of pulse oximetry and transcutaneous oxygen tension (tcPO2) was investigated in hypoxemic neonates and older infants with chronic hypoxemia due to bronchopulmonary dysplasia (BPD). It was found that during severe hypoxemia (tcPO2 less than 40 mmHg and saturation less than 80%) pulse oximetry showed a better correlation with arterial saturation than tcPO2 with arterial oxygen tension. During mild hypoxemia and normoxemia (tcPO2 40-90 mmHg and saturation 80-95%) tcPO2 and pulse oximetry both showed a good correlation with arterial values. Above 95% saturation and a corresponding tcPO2 of 70-120 mmHg, the correlation between arterial and transcutaneous PO2 was better than that between pulse oximetric and arterial saturation. Computer recording and analysis of tcPO2 and pulse oximetry improves the quality of both noninvasive oxygenation parameters in older infants with BPD.

Birth Weight↗
PubMed1987

Continuous neonatal evaluation in the delivery room by pulse oximetry.

The pulse oximeter, a noninvasive and continuous monitor of arterial oxygenation that is reliable in adults, children, and infants, was evaluated for use in neonates in the delivery suite. One hundred newborn infants, weighing 850 to 5,230 g each, delivered vaginally or by cesarean section with general or epidural anesthesia were studied. After delivery, each infant was placed in a radiant warmer, and a pulse oximetry probe was placed on the right hand. Hemoglobin saturation was then recorded for 15 minutes. Initial pulse oximetry values were obtained in less than one minute after cord clamping in 43% of infants, less than two minutes in 81%, and less than three minutes in 98%. Average arterial oxygen saturation was 59% at 1 minute (43 infants), 68% at 2 minutes (81), 82% at 5 minutes (98), and 90% at 15 minutes (91). Oxygen saturation was less than 30% in 12 neonates and less than 50% in 26 neonates at some time during the 15-minute monitoring period. Oxygen saturation did not differ significantly between neonates delivered vaginally or by cesarean section, regardless of the presence or type of anesthetic used. Arterial oxygen saturation measured by pulse oximetry showed a statistically significant relationship when compared with the traditional Apgar scoring system. Pulse oximetry was found to be very useful in objectively judging the adequacy of resuscitative efforts, as well as in identifying children who had marked arterial desaturation during the early neonatal period.

Humans↗
PubMed1988

Pulse oximetry: analysis of theory, technology, and practice.

Interest in two-wavelength classic, that is, nonpulse, oximetry began early in the 20th century. Noninvasive in vivo measurements of oxygen saturation showed promise, but the methods were beset by several problems. The pulse oximetry technique, by focusing on the pulsatile arterial component, neatly circumvented many of the problems of the classic nonpulse arterial approach. Today's pulse oximeter owes a good measure of its success to the technologic advances in light emission and detection and the ready availability of microcomputers and their software. Many clinicians have recognized how valuable the assessment of the patient's oxygenation in real time can be. This appreciation has propelled the use of pulse oximeters into many clinical fields, as well as nonclinical fields such as sports training and aviation. Understanding how and what pulse oximetry measures, how pulse oximetry data compare with data derived from laboratory analysis, and how the pulse oximeter responds to dyshemoglobins, dyes, and other interfering conditions must be understood for the correct application and interpretation of this revolutionary monitor.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

Pulse oximetry versus arterial blood gas specimens in long-term oxygen therapy.

Portable pulse oximeters are now widely available for the assessment of arterial oxygenation, and the U.S. Medicare program considers saturation readings to be acceptable substitutes for arterial PO2 in selecting patients for long-term oxygen therapy (LTOT). Current oximeters are reasonably accurate (plus or minus 4 or 5 percent of the co-oximetry value), but the clinician should be aware of several potential problems. Readings may be inaccurate in the presence of hemodynamic instability, carboxyhemoglobinemia, jaundice, or dark skin pigmentation, and also during exercise. Indicated saturation may substantially overestimate arterial PO2 if the patient is alkalemic. Pulse oximetry cannot detect hypercapnia or acidosis. For these and other reasons, pulse oximetry should not be used in initial selection of patients for LTOT, as a substitute for arterial blood gas analysis in the evaluation of patients with undiagnosed respiratory disease, during formal cardiopulmonary exercise testing, or in the presence of an acute exacerbation. Pulse oximetry is an important addition to the clinician's armamentarium, however, for titrating the oxygen dose in stable patients, in assessing patients for desaturation during exercise, for sleep studies, and for in-home monitoring.

Blood Gas Analysis↗
PubMed2000

Successful pharyngeal pulse oximetry in low perfusion states.

PURPOSE: We describe pharyngeal oximetry with the laryngeal mask airway in two patients with low perfusion states where finger oximetry failed. CLINICAL FEATURES: One patient was a 47-yr-old man with septic shock and the other a 64-yr-old man with multiorgan failure. In both patients, a # 4 laryngeal mask airway with a pediatric pulse oximeter probe was inserted behind the tracheal tube. A good waveform was obtained and oxygen saturation was 0-2% lower than arterial samples. CONCLUSION: Pharyngeal oximetry with the laryngeal mask airway is feasible in low perfusion states when finger oximetry fails.

Humans↗
PubMed1998

A preliminary comparison of videofluoroscopy of swallow and pulse oximetry in the identification of aspiration in dysphagic patients.

Pulse oximetry has recently received attention in the dysphagia literature because of its possible contribution to the management of neurogenic dysphagia. The present study was devised to examine whether pulse oximetry could be exploited to determine episodes of aspiration in patients with known dysphagia of neurologic origin. To this end, pulse oximetry was undertaken in six patients undergoing videofluoroscopic study of swallow. Normal controls also underwent pulse oximetry during feeding. The results indicate that there is no clear-cut relationship between changes in arterial oxygenation and aspiration. However, some support is found for the association between altered arterial oxygenation and oral feeding in dysphagic individuals. Further research in both normals and compromised individuals is needed.

Adult↗
PubMed1999

Assessment of dysphagia with the use of pulse oximetry.

Recent anecdotal literature has shown a relation between arterial oxygen saturation (SpO2), as measured by pulse oximetry, and aspiration during eating. The present study was designed to determine whether bedside pulse oximetry has a role in the assessment of pharyngeal phase dysphagia. Forty-six adult patients with clinically suspected swallowing abnormalities underwent modified barium swallow to evaluate dysphagia. After determining baseline oxygen saturation by pulse oximetry, different consistencies of barium were sequentially ingested. Patients were monitored for radiographic evidence of penetration or aspiration, which was correlated with continuous SpO2 recording. Patients who exhibited aspiration or penetration without clearing had a significant decline in SpO2 compared with those patients who penetrated but cleared or in whom no penetration was observed. These relations were not associated with age, gender, or diagnosis. These preliminary data indicate that bedside pulse oximetry may be a useful tool in the evaluation of patients with dysphagia.

Adult↗
PubMed2003

Evaluation of fetal intrapartum hypoxia by middle cerebral and umbilical artery Doppler velocimetry with simultaneous cardiotocography and pulse oximetry.

OBJECTIVE: To investigate fetal circulation at different stages of hypoxia during labor, and to study blood flow alterations in the brain and peripheral tissues, through simultaneous use of three non-invasive techniques. MATERIALS AND METHODS: Ninety two pregnant women between 38 and 41 weeks of gestation, comparable for maternal age and parity, were simultaneously monitored with cardiotocography (CTG), continuous fetal pulse oximetry and Doppler ultrasonography during the first stage of labor. In 70 cases evaluation was successful, and useful data was obtained. Doppler waveforms were obtained before and during abnormal CTG patterns, of both the umbilical (UA) and middle cerebral artery (MCA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI). The study population was divided in three groups, according to CTG and fetal pulse oximetry tracings: 20 term fetuses with normal CTG patterns and oxygen saturation (FSPO(2)) values >40%, 30 term fetuses with abnormal CTG patterns and FSPO(2) values between 30 and 40%, and 20 fetuses with abnormal CTG patterns and FSPO(2) values <30% for a time up to 2 min. These were studied and peripartum outcomes were compared. RESULTS: Redistribution of blood flow was noted at FSPO(2) values of 37%, in all groups. In the presence of reduced oxygen saturation (near to or below 30%), MCA Doppler showed significantly lower PI (1.06+/-0.33 vs.0.74+/-0.39, p=0.03) and RI (0.59+/-0.14 vs. 0.44+/-0.14, p=0.03), while that of the UA showed mildly higher resistance indices (0.98+/-0.14 vs. 1.28+/-0.50, p=0.01 and 0.57+/-0.12 vs. 0.79+/-0.24, p=0.004, respectively). When an oxygen saturation value of <30% was maintained for greater than 2 min, MCA Doppler indices reversed, likely indicating morbid fetal hypoxia. Differences in fetal outcomes between groups correlated with Doppler and pulse oximetry tracings. CONCLUSIONS: During active labor the fetus maintains oxygen supply to the brain by redistributing blood flow. In cases of hypoxia this is feasible for only 2 min. We note a strong correlation between fetal pulse oximetry, Doppler velocimetry of the MCA and UA, and fetal morbidity.

Adult↗
PubMed1997

Accuracy of pulse oximetry during intense exercise under severe hypoxic conditions.

There is a growing need to measure arterial oxygen saturation with a non-invasive method during heavy exercise under severe hypoxic conditions. Although the accuracy of pulse oximetry has been challenged by several authors, it has not been done under extreme conditions. The purpose of this study was to evaluate the accuracy of a pulse oximeter (Satllite. Datex, Finland) during exercise under hypoxic conditions where arterial oxygen saturation was below 75%, simulating exercise at extreme altitude. Ten healthy non-smoking men performed two exercise studies of 30 min under normoxia and under hypoxia on two consecutive days. The exercise intensity was 80% of maximal O2 consumption of VO2max. Arterial oxygen saturation measured by pulse oximetry was corrected (SpO2[corr]) according to previously published equations and was compared to arterial oxygen saturation (SaO2) in blood samples taken simultaneously from the radial artery. Reference arterial saturation values ranged from 57.2 to 97.6% for the whole data set. This data set was split according to low (SaO2 < or = 75%) and high (SaO2 > 75%) SaO2 values. The error of pulse oximetry (SpO2[corr]-SaO2) was 2.05 (0.87)% [mean (SD)] and 1.80 (1.81)% for high and low SaO2 values, respectively. SpO2[corr] and SaO2 were highly correlated (r = 0.93, SEE = 1.81) for low values. During high-intensity constant workload under severe hypoxic conditions, once corrected, pulse oximetry provides an estimate of SaO2 with a mean error of 2%. Thus, the correction previously described for SpO2 values above 75% saturation applies also to SpO2 values in the range of 57-75% during exercise under hypoxic conditions.

Adult↗
PubMed2005

The contribution of pulse oximetry to the early detection of congenital heart disease in newborns.

UNLABELLED: Approximately half of all newborns with congenital heart disease are asymptomatic in the first few days of life. Early detection of ductal-dependant cardiac malformations prior to ductal closure is, however, of significant clinical importance, as the treatment outcome is related to the time of diagnosis. Pulse oximetry has been proposed for early detection of congenital heart disease. The aims of the present study were: 1) to determine the effectiveness of a pulse-oximetric screening performed on the first day of life for the detection of congenital heart disease in otherwise healthy newborns and 2) to determine if a pulse-oximetric screening combined with clinical examination is superior in the diagnosis of congenital heart disease to clinical examination alone. This is a prospective, multi-centre study. Postductal pulse oximetry was performed between six and twelve hours of age in all newborns of greater than 35 weeks gestation. If pulse-oximetry-measured arterial oxygen saturation was less than 95%, echocardiography was performed. Pulse oximetry was performed in 3,262 newborns. Twenty-four infants (0.7%) had repeated saturations of less than 95%. Of these infants, 17 had congenital heart disease and five of the remaining seven had persistent pulmonary hypertension. No infant with a ductal-dependant or cyanotic congenital heart disease exhibited saturation values greater or equal to 95%. CONCLUSION: postductal pulse-oximetric screening in the first few days of life is an effective means for detecting cyanotic congenital heart disease in otherwise healthy newborns.

Early Diagnosis↗
PubMed1989

Pulse oximetry in the emergency department.

Three cases representing the emergency department use of pulse oximetry are described. A brief review of the principles of operation of pulse oximetry, as well as a discussion of recent literature and clinical uses of the technology, is presented. While not replacing arterial blood gases in the assessment of critically ill patients, a more widespread use of pulse oximetry in evaluating emergency department patients might provide significant information in the management of patients with respiratory complaints. Pulse oximetry may also play an important role in monitoring those patients requiring airway interventions such as assisted ventilation or endotracheal intubation.

Adolescent↗
PubMedDate not supplied

Pulse oximetry for preoperative vascular assessment in a thumb near-amputation.

Pulse oximetry, or photoplethysmography, is widely available in emergency departments and intuitively seems well suited to the evaluation of vascular compromise in digital trauma. In a review of the medical literature, no cases were found in which pulse oximetry was used in preoperative assessment of a traumatized digit. We report the case of a patient with a near-amputation of his thumb in whom pulse oximetry proved to be a valuable tool in his evaluation and treatment because it was a rapid, noninvasive, sensitive means of assessment of digital vascular viability. Evaluation and management of this patient is discussed, and the pertinent literature concerning the use of pulse oximetry and vascular injuries of the hand is reviewed.

Adult↗
PubMed2005

Transabdominal fetal pulse oximetry with near-infrared spectroscopy.

OBJECTIVE: The purpose of this study was to determine the feasibility of noninvasive fetal pulse oximetry in the human fetus with transabdominal continuous-wave near-infrared spectroscopy. STUDY DESIGN: The instrument has 3 wavelength light-emitting diodes (735, 805, and 850 nm) as light sources and a photomultiplier tube as a detector. This instrument was used in 6 pregnant women (>36 weeks of gestation). First, a fetal heart rate was obtained with a fetal heart rate monitor. Then, the depth of fetal tissue (head) from the maternal abdomen was determined by ultrasound examination; the distance between the optodes (light source and the detector) was set to be approximately twice the depth of the fetus (7-11 cm). The data analysis was based on the modified Beer-Lambert law and the use of optical densities at 735 and 850 nm to obtain the concentration changes of the oxyhemoglobin and deoxyhemoglobin. The saturation was expressed as the percent of oxygen saturation equal to 100 x oxyhemoglobin/(oxyhemoglobin + deoxyhemoglobin). We recorded the spectroscopy data and the fetal heart rate for approximately 3 to 10 minutes in each patient. RESULTS: The mean oxygen saturation values of each of the 6 individual fetuses ranged from 50% to 74% (overall mean saturation, 61% +/- 14.8% [SD]). CONCLUSION: This preliminary data indicate that transabdominal fetal pulse oximetry is feasible for human patient application. The measured values were similar to those that are obtained with transvaginal pulse oximetry. Future studies should correlate transabdominally obtained measurements with those measurements that are obtained by transvaginal fetal pulse oximetry.

Abdomen↗
PubMed2005

Evaluation of oesophageal reflectance pulse oximetry in major burns patients.

Pulse oximetry is being used in everyday clinical practice in anaesthesia utilising a peripheral probe. However, it may be unreliable in certain clinical situations such as hypothermia, hypovolemia, vasoconstriction and decreased cardiac output. Similar situations occur in burns patients and, more importantly, burns to extremities which limit the sites available for measurement of peripheral oxygen saturation (SpO(2)). To overcome these limitations, the oesophagus has been investigated as an alternative measurement site, as perfusion may be preferentially preserved centrally. A miniaturised reflectance oesophageal saturation (SpO(2)) probe has been constructed utilising infrared and red photodiodes and a photodetector. Our study was aimed at evaluating the reliability of oesophageal pulse oximetry in major burns patients. Seven adult patients (five males, two females) were studied. They were sedated and ventilated as part of their routine care. Measurable photoplethysmographic (PPG) traces and SpO(2) values were obtained in the oesophagus of all patients at a mean depth of 15.6+/-1.8 cm (measured from the lips). It was found that the oesophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a CO-oximeter. The mean (+/-S.D.) of the differences between the oesophageal oxygen saturation results and those from CO-oximetry was 0.50+/-0.69%. A Bland and Altman analysis showed that the bias and the limits of agreement between the oesophageal and commercial toe pulse oximeters were 0.4% and -3.6% to 4.6%, respectively. This study suggests that the oesophagus can be used as an alternative site for monitoring arterial blood oxygen saturation by pulse oximetry in burned patients.

Adult↗
PubMed2004

Effect of body mass index on overnight oximetry for the diagnosis of sleep apnea.

Overnight oximetry is widely used for screening for the sleep apnea hypopnea syndrome (SAHS). The degree of desaturation at an apnea event is known to be affected by the degree of obesity. We hypothesized that the diagnostic ability of oximetry for SAHS is affected by the degree of obesity. A total of 424 consecutive patients referred for possible SAHS were studied. The subjects were classified into three groups of normal-weight, overweight and obese based on the body mass index (BMI). The apnea-hypopnea index (> or = 15 h(-1)) by polysomnography was used as the diagnostic gold standard. Oximetry data were automatically analyzed to calculate the oxygen desaturation index (ODI2/3/4:at 2%/3%/4% threshold). The diagnostic abilities of the ODI were different in the three BMI-groups at a given cutoff value, e.g. the sensitivity/specificity of ODI4 (cutoff = 15) were 54%/100%, 83%/ 97%, and 98%/78% for the normal-weight, overweight and obese groups, respectively (P < 0.0001). The gender and the age had no significant effect on the ability. We demonstrated the diagnostic sensitivity and specificity of the ODI for SAHS depended on the BMI. Oximetry as a screening tool for SAHS may become more useful by selection of a cutoff value appropriate for the BMI of each subject.

Aged↗