Oximetry Readings Research Articles

A comparison of response time to desaturation between tracheal oximetry and peripheral oximetry

Trachea is an alternative site for pulse oxygen saturation monitoring. The response time of the oximetry probe has been reported more rapid when placed in central than in peripheral. The purpose of this study is to compare the performance of the oximetry probes placed in trachea and peripheral site during rapid desaturation. Endotracheal tubes with an oximetry sensor were intubated in ten anesthesia dogs. Both the oxygen saturation signals from trachea (S(t)O(2)) and tail (S(p)O(2)) were shown on the same monitoring screen. The mechanical ventilation was disconnected to produce a rapid desaturation when both S(t)O(2) and S(p)O(2) were 100%, and the mechanical ventilation was reconnected when S(p)O(2) decreased to 80%. The time of S(t)O(2) and S(p)O(2) dropped to 95, 90, 85, and 80% was recorded, respectively during the mechanical ventilation disconnection, and the arterial blood was sampled for arterial oxygen saturation (S(a)O(2)) measurement simultaneously. The levels of measurement agreement between two oximetry readings (S(p)O(2), S(t)O(2)) and S(a)O(2) were analyzed, respectively with the Bland and Altman method. The mean response time of S(t)O(2) was significantly shorter than S(p)O(2) when both of them decreased from 100 to 80% (172.6+/-68.9 vs 220.7+/-72.3 s) during rapid desaturation. The 95% confidence interval for absolute difference between S(p)O(2) and S(a)O(2) was 4.12+/-6.47%, and between S(t)O(2) and S(a)O(2) was 3.33-3.46%. Oxymetry placed in trachea provides a better monitoring for detecting rapid desaturation than in peripheral.

Telemetry Via Wi-Fi: A Case Study

Telemetry Via Wi-Fi: A Case Study

Effect of Road Traffic Accident Contaminants on Pulse Oximetry among Normoxaemic Volunteers

Objectives Pulse oximetry is a simple and reliable non-invasive method used widely in emergency care. Signal strength is usually easy to interpret in most monitors and is used as a simple validation tool for the reliability of the readings. However it is known from the literature that in certain circumstances the oxygen saturation readings could be false in spite of a deceptively normal signal. The aim of this study was to compare the pulse oximetry readings on fingers contaminated with natural contaminants which might appear in a road traffic accident (RTA) scenario. Methods 50 healthy volunteers were included. Beside the control fingers, the others were contaminated by (1) dried blood (B), (2) soil (S), (3) oil grease (O) and (4) green extract from natural leaves (G). Results The average control reading was 99.1% (SD 1.11). The average readings on the contaminated fingers were as follows: B: 98.6% (SD 1.27); S: 98.7% (SD 1.17); O: 98.5% (SD 1.09); G: 98.7% (SD 1.06). There was a statistically different decrease in the readings between the B and O groups compared to control. Conclusion Pulse oximetry could give unreliable readings despite a normal signal when a patient's fingers are contaminated - especially with dried blood or black oil grease which are both common in road traffic accidents. Cleaning the fingers before pulse oximetry therefore should be considered.

65-Year-Old Man With Persistent Fever

65-Year-Old Man With Persistent Fever

65-Year-Old Man With Persistent Fever

© 2009 Mayo Foundation for Medical Education and Research A 65-year-old man was transferred to our institution for evaluation of fever. His symptoms included subjective fever, cough productive of creamy white sputum, and nasal congestion of 3 months’ duration. He denied dyspnea, hemoptysis, weight loss, or night sweats. Approximately 10 days before admission, he had been seen by his primary care physician for worsening of symptoms and was treated empirically with an undefined antibiotic. Subsequently, palpitations and severe fatigue developed, and the patient was admitted to a local hospital, where he was noted to be febrile and hypoxic with pulse oximetry readings in the high 80% range. Acute coronary syndrome was excluded, and ceftriaxone and moxifloxacin were initiated empirically. Computed tomography (CT) of the chest without intravenous contrast was performed. Compared with chest CT performed 4 years earlier, no new pulmonary infiltrate was evident; however, both the superior and the lateral aspect of the right hilum were more prominent than in the previous study and were suspicious for adenopathy. The patient was transferred to our institution approximately 2 days later for further evaluation. On admission, the patient’s main symptoms were fever, fatigue, palpitations, mild chest discomfort, cough, and nasal congestion. Findings on the rest of the systems review were unremarkable. The patient had a history of asthma, chronic sinusitis, seasonal allergic rhinitis, aspirin intolerance, nasal polyposis with multiple prior polypectomies, and benign prostatic hypertrophy. His medical regimen consisted of omeprazole, atorvastatin, doxazosin, irbesartan-hydrochlorothiazide, montelukast, and fluticasone-salmeterol. His family history was notable for a sibling’s death due to lung cancer at age 28 years. On physical examination, the patient had a temperature of 37.9 °C, heart rate of 95 beats/min (regular), blood pressure of 149/74 mm Hg, respiratory rate of 18 breaths/min, and pulse oximetry of 94% while breathing 3 L of oxygen via nasal cannula. He appeared comfortable and had palpable anterior cervical chain and submandibular lymph nodes, jugular venous distension 3 cm above the clavicle, faint inspiratory crackles at both lung bases, and a grade 2/6 systolic murmur best heard at the apex. Findings on the rest of the physical examination were normal. Laboratory results are listed in the Table.

Anesthetic Management of a Patient With Congenital Methemoglobinemia

Methemoglobinemia occasionally causes cyanosis particularly in congenital methemoglobinemia. Avoidance of exposure to oxidizing agents is important for patients with congenital methemoglobinemia because of their deficient enzymatic pathways and decreased oxygen-carrying capacity. Here, we present a patient with preoperatively undiagnosed congenital methemoglobinemia who underwent uterine myomectomy under general anesthesia. The patient was a 35-year-old woman who displayed a low pulse oximetry reading of 91% prior to induction of anesthesia. Methemoglobinemia was first suspected intraoperatively because of a mismatch of SpO2 of finger pulse oximetry and SaO2 of arterial blood, and was later confirmed by multiple-wavelength CO-oximetry. The pathophysiology, etiology, clinical manifestations, anesthetic considerations, and treatment options of methemoglobinemia are discussed.

Index of Suspicion

Index of Suspicion

Effects of hyperbaric oxygen on the replanted extremity subjected to prolonged warm ischaemia

In this investigation, the influence of hyperbaric oxygen (HBO) therapy on the survival of a replanted extremity subjected to prolonged warm ischaemia is evaluated. Among the relative contraindications to replantation are prolonged warm ischaemia time, since an obstruction to blood reflow ('no-reflow phenomenon') may occur in amputated parts that are subjected to more than 6h of warm ischaemia. Twenty-three rat hindlimbs were amputated and subjected to 4h of normothermic ischaemia. The average weight of the animals was 500 gm, and re-plantation of the hindlimb was performed by bone fixation followed by microvascular anastomosis of the femoral vessels. Limb re-vascularisation was confirmed at the end of all procedures by the milk test, clinical assessment and pulse oximetry recordings (>90%). Eleven animals served as a control group and no further therapy was instituted, whereas 12 animals served as the study (replantation) group and were subjected to HBO therapy for 3 days postoperatively. The therapy was conducted in a large animal chamber for 90 min at 2.5 ata. Limb survival was assessed by capillary refill upon compression, skin turgor assessment and colour. Confirmation of clinical findings was conducted with daily pulse oximetry readings of >90%. Animals were followed up for 7 days at which point all animals were euthanized or were euthanized earlier if a non-viable limb was present. Two of the 11 limbs in the control group survived following re-plantation, whereas eight of the 12 limbs in the experimental HBO group survived at least 7 days following replantation. This difference was statistically significant (p=0.0361) using chi-square analysis and Fisher's exact test. Although re-plantation of an amputated extremity after prolonged warm ischaemia is considered a relative contraindication due to the possibility of poor outcomes, our results indicate that the window for replantation may be increased if adjunctive HBO therapy is employed in the postoperative period.

Intraparenchymal Methylene Blue Injection for Sentinel Lymph Node Biopsy in Breast Cancer Patients does not Interfere with the Pulse Oximetry Readings

Purpose: Alteration in oxygen saturation is a side effect of the dye used in sentinel lymph node biopsy. The object of this study was to determine the possible effects of methylene blue on the oxygen saturation in patients undergoing sentinel lymph node biopsy. Methods: The complete peroperative records of 148 patients who underwent sentinel lymph node biopsy with intraparenchymal injection of methylene blue were reviewed. The data reviewed included the preinjection pulse oximeter saturation readings and the postinjection values until the readings returned to the preoperative levels in the postanesthesia care unit. Results: The pulse oximetry values were recorded preoperatively, after intubation and, at 15, 30, 45, and 60 minutes of the operation. The results showed that methylene blue did not cause any significant changes in oxygen saturation levels. Conclusion: We suggest that methylene blue might be preferable for the patients with concomitant disease, and for whom close monitoring of their oxygen saturation is required.

Dyshemoglobinemias and Pulse Oximetry

Pulse oximetry normally provides a reliable indicator of arterial blood oxygen saturation. Individuals with a variant hemoglobin with low oxygen affinity would exhibit pulse oximetry values consistent with hypoxemia despite maintaining adequate oxygen delivery to tissues. We describe a patient we diagnosed with hemoglobin Rothschild and his mother. He presented with SpO2 81% on pulse oximetry and PaO2 on arterial blood gas of 47 mm Hg, while his mother had SpO2 87%. These values were significantly lower than physical examination suggested. A possible dyshemoglobinemia should be suspected when discordance exists between pulse oximetry readings and physical examination findings.

Pulse Oximetry Coupled With Spirometry in the Emergency Department Helps Differentiate an Asthma Exacerbation From Possible Vocal Cord Dysfunction

Nolan PK, Chrysler M, Phillips G, Goodman D, Rusakow LS. Pediatr Pulmonol. 2007;42(7):605–609 PURPOSE OF THE STUDY. These investigators sought to determine if they could find evidence for vocal cord dysfunction (VCD) in asthmatic adolescents whose condition failed to respond adequately to treatment in the emergency department (ED) for a presumptive asthma exacerbation. STUDY POPULATION. Subjects with wheezing presenting to the ED of an urban children's hospital were recruited. Inclusion criteria were age 12 to 21 years, failure to respond to treatment for wheeze sufficiently to allow discharge, and pulse oximetry reading of ≥97%. Exclusion criteria were having other cardiac or pulmonary disease, inability to perform spirometry, or need for endotracheal intubation. METHODS. Spirometry with standard techniques was performed by using a computer-linked pneumotachygraph and appropriate software to capture both expiratory and inspiratory flow volume curves. Spirometric results were classified as small airway obstruction, variable extrathoracic airway obstruction (consistent with VCD), a combination of the 2 previous findings, or normal airflow. RESULTS. Twenty ED encounters with 17 subjects were studied. Only 5 (25%) of the encounters included spirometric evidence of small airway obstruction, but 12 of 20 had evidence for VCD (ie, variable extrathoracic airway obstruction on the inspiratory loop). These 12 included 3 that also had evidence for small airway obstruction. There were 6 encounters with no abnormality on spirometry. CONCLUSIONS. Spirometry may identify presumptive refractory asthma exacerbations that, instead, are episodes of VCD. REVIEWER COMMENTS. Several years ago we treated an 8-year-old boy who had been admitted to the hospital for status asthmaticus 4 times in 1 month but never had an oxygen requirement. A videotape of the boy when he was symptomatic (provided by the parents) showed obvious stridor, not wheezing. Similarly, in this study the cardinal observation was refractory “wheeze” without arterial desaturation. Computerized spirometry is not universally available in the ED, and in addition, not all such units have software capable of displaying the inspiratory limb of the flow-volume loop. However, in busy ED environments with large asthmatic populations, availability of this measurement should greatly aid the classification of wheezing events. Pediatricians need to be more aware that VCD may present symptoms that mimic asthma.

Pulse Oximetry Screening at 4 Hours of Age to Detect Critical Congenital Heart Defects

The purpose of this prospective study was to assess the feasibility and reliability of pulse oximetry screening to detect critical congenital heart defects in a newborn nursery. The study was performed in a large urban hospital with an exclusively inborn population. Stable neonates who had a gestational age of >or=35 weeks and birth weight of >or=2100 g and in whom a critical congenital heart defect was not suspected were admitted to the newborn nursery. When the 4-hour pulse oximetry reading was <96%, pulse oximetry was repeated at discharge, and when the pulse oximetry reading remained at persistently <96%, echocardiography was performed. Of 15299 admissions to newborn nursery during the 12-month study period, 15233 (99.6%) neonates were screened with 4-hour pulse oximetry. Pulse oximetry readings were >or=96% for 14374 (94.4%) neonates; 77 were subsequently evaluated before discharge for cardiac defects on the basis of clinical examination. Seventy-six were normal, and 1 had tetralogy of Fallot with discontinuous pulmonary arteries. Pulse oximetry readings at 4 hours were <96% in 859 (5.6%); 768 were rescreened at discharge, and 767 neonates had a pulse oximetry reading at >or=96%. One neonate had persistently low pulse oximetry at discharge; echocardiography was normal. Although 3 neonates with a critical congenital heart defect had a 4-hour pulse oximetry reading of <96%, all developed signs and/or symptoms of a cardiac defect and received a diagnosis on the basis of clinical findings, not screening results. All neonates with a critical congenital heart defect were detected clinically, and no cases of critical congenital heart defect were detected by pulse oximetry screening. These results indicate that pulse oximetry screening does not improve detection of critical congenital heart defects above and beyond clinical observation and assessment. Our findings do not support a recommendation for routine pulse oximetry screening in seemingly healthy neonates.

Fetal pulse oximetry: Correlation with intrapartum fetal heart rate patterns and neonatal outcome

To determine how fetal pulse oximetry behaves in various cardiotocographic (CTG) tracings and correlates with neonatal outcome. Pregnant women undergoing active labor with singleton pregnancies of 32-42 weeks were enrolled. CTG recordings were reassuring or nonreassuring (namely variable or persisting late decelerations). Pulse oximetry values during labor and changing throughout deceleration and recovery phases, duration and frequency of pulse oximetry recordings <30%, and neonatal outcome were determined. One-way anova, Tukey test, chi(2)-test and multiple logistic regression model were used for statistical analysis where appropriate. A total of 156 pregnant subjects were divided into three groups: reassuring fetal heart rate (FHR) patterns (group 1, n=78 [50%]), late decelerations (group 2, n=16 [10.3%]) and variable decelerations (group 3, n=62 [39.7%]). The initial and final pulse oximetry readings, pulse values in first stage of labor, the duration and the frequency of pulse oximetry recordings <30% were significantly different between groups (P<0.001, P<0.001, P<0.001, P=0.001, P<0.001). Fetal acidosis was significantly more frequent with late decelerations (23.1%, P=0.004). A multiple logistic regression model demonstrated that the initial pulse oximetry value during active labor was the most predictive variable of neonatal well-being (P<0.001). Decreased fetal pulse oximetry values, especially prolonged and recurrent recordings <30% are well-correlated with abnormal FHR patterns, indicating an association with fetal compromise and metabolic acidosis. Going through active labor with a lower initial value of FSpO(2) more frequently leads to an altered FHR pattern and subsequent adverse fetal outcome.

Does Arterial Oxygen Desaturation as Measured by Pulse Oximetry Occur During Aspiration or Penetration in Acute Dysphagic Stroke Patients?

Background: The high prevalence of swallowing problems and aspiration in stroke patients has been well documented. A reliable swallowing assessment that can accurately determine potential aspiration risk is necessary. The most recent adjunct to the clinical bedside assessment has been the use of pulse oximetry. Purpose: This study examines whether the use of oxygen saturation levels as measured by pulse oximetry can reliably predict the presence of aspiration or penetration of acute dysphagic stroke patients. Methods: This prospective study compared results of pulse oximetry in 20 people with dysphagia post stroke with normal controls. Fiberoptic Endoscopic Evaluation of the Swallow (FEES) was used to confirm the presence of aspiration or penetration. The FEES and pulse oximetry readings were taken simultaneously. Investigators evaluated the results of each test independently to avoid bias. Results: The results confirmed that saturation levels are lower in people with dysphagia post stroke than in the nondysphagic control group. No systematic relations between saturation levels and episodes of aspiration or penetration were found for any of the consistencies tested. Clinically significant changes in oxygen saturation are not found to predict risk of aspiration or penetration in the patient group. Measures of sensitivity (23.5%) and specificity (33.3%) are low. Conclusions: The results confirm that oxygen saturation as measured by pulse oximetry is not a reliable screening tool for identifying aspiration risk in acute stroke patients.

Changes in Pulse Oximetry After Patent Blue Dye Injection Into the Uterine Cervix

To evaluate changes in pulse oximetry readings in patients with cervical carcinoma after the injection of patent blue dye into the uterine cervix for sentinel lymph node detection. Fifty-six patients underwent radical hysterectomy and bilateral pelvic lymphadenectomy for the treatment of International Federation of Gynecology and Obstetrics stage I or II cervical cancer. Four milliliters of patent blue dye were injected into the cervix. On the eve of surgery, all patients also received an injection of Dextran 500 labeled with technetium 99 m (Tc-99 m Dextran, 600 to 800 muCi) into the cervix and subsequently underwent pelvic lymphoscintigraphy. Of the 56 patients, 1 (1.79%) had an anaphylactic reaction, and in 13 (23.22%), pulse oximetry readings were <96%. The lowest median pulse oximetry reading in these patients was 87%. Pulse oximetry readings began to decrease between 2 and 10 minutes after patent blue dye injection into the cervix and lasted for approximately 5 minutes. No changes in blood pressure, heart rate, or electrocardiogram were found during the period in which this alteration was recorded by the pulse oximeter. The decrease in pulse oximetry readings after patent blue dye injection into the cervix was associated with larger tumors and tumors that surrounded the external cervical os.

Screening Newborns for Congenital Heart Disease with Pulse Oximetry: Survey of Pediatric Cardiologists

Controversies exist regarding the use of pulse oximetry for routine screening of newborns. This study aimed to evaluate current practices and opinions of pediatric cardiologists in relation to newborn screening for congenital heart disease (CHD) using pulse oximetry. Email invitations were sent to 1,045 pediatric cardiologists in North America. The survey was Internet based and included multiple-choice questions. Two repeat email reminders were sent after the initial invitation. A total of 363 responses (35%) were returned. In terms of experience, 40% of the respondents had more than 20 years, 32% had 10 to 20 years, 21% had 5 to 10 years, and 6% had less than 5 years of experience. More than 90% agreed that an early diagnosis of CHD for newborns prevents morbidity and mortality. In terms of practice, 96% reported that all newborns are examined by a clinician before discharge, 29% reported that newborns get a pulse oximetry reading, and 1.4% (n = 5) reported the use of electrocardiogram. Only 58% of respondents thought that current practice is adequate for detecting significant CHD. With regard to their experience with pulse oximetry, 26% reported "too many false-positives," 21% described it as "prone to noise and artifact," and 30% viewed it as "very operator dependent." The overall support for mandated pulse oximetry screening was 55%. The support for mandate decreased with years of experience, with 76% of the supporters having less than 5 years, 58% of those having 5 to 10 years, 53% of those having 10 to 20 years, and 51% of those having more than 20 years of experience. Pediatric cardiologists recognize that current practice is inadequate for detecting significant CHD. Slightly more than half of the pediatric cardiologists in this study supported a mandate for pulse oximetry screening, but there were many concerns, and the support decreased with increasing years of clinical experience.

Advances in neonatal resuscitation: supporting transition

Although neonatologists use the term resuscitation we rarely practise resuscitation as the adult doctors understand it. An adult who collapses lifeless needs very urgent chest compressions, cardioversion and ventilation. Such...

The Reliability of a Single Pulse Oximetry Reading as a Screening Test for Congenital Heart Disease in Otherwise Asymptomatic Newborn Infants

Routine pulse oximetry has been studied to detect children with otherwise undiagnosed congenital heart disease prior to nursery discharge. The reported sensitivities in asymptomatic patients have been less than expected and vary widely, bringing into question the reliability of the test. The purpose of this study was to assess whether routine pulse oximetry contributes to identifying patients with critical congenital heart disease and to determine the reliability of a single pulse oximeter reading in screening asymptomatic newborn infants. Between December 26, 2003, and December 31, 2005, three hospitals in west central Florida performed a pulse oximetry routinely on all newborns at the time of discharge. Patients diagnosed with critical congenital heart disease during the study period were identified to assess whether the pulse oximetry reading initiated their diagnosis. In one hospital, the pulse oximeter data were evaluated for reliability. Downloaded data were compared to a log compiled by the nursery personnel, first without (phase 1) and then with (phase 2) their knowledge and additional training. Results were characterized as reliable, probe placed but reading not verifiable, or no evidence of probe placement. Of the 7962 infants who received oximetry testing, there were 12 postnatal diagnoses of critical congenital heart disease. None was initially identified by routine pulse oximetry. Pulse oximetry reliability improved substantially between phase 1 and phase 2 (38 v. 60%, p < 0.0001). Optimal reliability (>95%) was obtained by a nurse with a degree of LPN or higher performing an assessment of at least 360 seconds. Routine pulse oximetry was neither reliable nor an important diagnostic tool in our cohort. Important human factors (probe placement time, oximetry training, and nursing degree) impact single determination pulse oximetry reliability. With routine surveillance and quality improvement, the reliability of this test can be increased. Future studies to determine the effectiveness of pulse oximetry screening for the diagnosis of congenital heart disease in the asymptomatic newborn population must address these factors. Until such a study demonstrates acceptable sensitivity and clinical value, universal screening should not be instituted.

Delivery of antegrade cerebral perfusion during descending aortic reconstruction: a case report

Antegrade cerebral perfusion (ACP) has been demonstrated to be a safe and effective method of providing adequate protection to the brain during hypothermic circulatory arrest. By improving oxygen delivery to the cerebral capillaries, users of this technique have reported fewer temporary neurological deficits in postoperative periods, even after prolonged periods of circulatory arrest. Furthermore, ACP may be delivered with little alteration to the cardiopulmonary bypass (CPB) circuit. Surgical correction of a descending aortic aneurysm can provide a challenge when the left subclavian artery is involved. A period of hypothermic circulatory arrest is required to complete the proximal anastamosis of the graft. Access to the cerebral vessels for selective cerebral perfusion is limited during a left thoracotomy approach. A 54-year-old female presented with a computerized tomography (CT) scan of a descending aortic aneurysm, originating at the base of the left subclavian artery. Surgical intervention using CPB via femoral-femoral cannulation was employed. The patient was systemically cooled to 22 degrees C. Selective antegrade cerebral perfusion was administered via cannulation of the left common carotid artery. Antegrade cerebral perfusion lasted 19 minutes, with improved transcranial oximetry readings. The patient was successfully weaned from CPB. The patient was discharged on postoperative day nine with no evident suquelae. It is believed that the application of ACP in this procedure further improved patient outcome.

Diagnostic room-air pulse oximetry: effects of smoking, race, and sex

Objective We sought to determine the distribution of oximetry (Sp o 2) values in awake, asymptomatic adults and the effect of personal characteristics on these values. Methods Using a cross-sectional design, we sampled oximetry readings in awake, asymptomatic adults in an emergency department setting. Personal characteristics were analyzed using logistic regression, with lower oximetry readings, defined by the 20th percentile, as the dependent variable. Results Of 871 eligible subjects, 50 (5.7%) had an Sp o 2 value less than 97%, and 13 (1.5%) had an Sp o 2 value less than 96%. Lower readings were associated with the following characteristics (odds ratio with 95% confidence interval): male sex, 3.8 (2.5-5.6); age ≥60 years, 2.4 (1.3-4.5); white race, 5.3 (3.6-7.8); obesity, 3.2 (2.1-4.8); history of asthma, 3.2 (1.6-6.2). Smoking was not associated with lower Sp o 2 values. Conclusion Room-air Sp o 2 values less than 97% are rare in asymptomatic, awake adults. White race and male sex are associated with lower Sp o 2 readings.