Prehospital use of pulse oximetry in rotary-wing aircraft

A prospective study of 200 patients was conducted to evaluate the use of pulse oximetry as an adjunct to clinical monitoring of clinically ill patients transported by rotary-wing aircraft with non-pressurized cabins. Thirty-four subjects (17%) were found to have significant hemoglobin desaturation of less than 90%, as defined by pulse oximetry (SpO 2). Data were recorded continuously for later review. Desaturation often was noted prior to alterations in vital signs or clinical appearance. In 32 of 34 hypoxemic subjects (94%), therapeutic interventions corrected the low SpO 2. The use of pulse oximetry permitted measures for cardiorespiratory support to be instituted and assessed more rapidly than otherwise would have been possible. The availability of a continuous record of SpO 2 facilitated detailed review of case management. It is concluded that the use of pulse oximetry is a practical and valuable adjunct for monitoring critically ill patients transported by rotary-wing aircraft.     

Pulmonary aspiration during emergency endoscopy in patients with upper gastrointestinal hemorrhage

OBJECTIVE: To evaluate the frequency and significance of aspiration and its clinical importance in patients with upper GI bleeding undergoing esophagogastroduodenoscopy in the ICU. DESIGN: Thirty consecutive patients with active and severe upper GI bleeding were studied. SETTING: ICU. PATIENTS: Ranged in age from 20 to 78 yr with an equal number of males and females. INTERVENTIONS: All patients had continuous pulse oximetry monitoring and had chest radiographs obtained less than 12 hr before endoscopy and less than 4 hr after endoscopy. MEASUREMENTS: Six (20%) of 30 patients developed new lung infiltrates after esophagogastroduodenoscopy. In this group of patients, preendoscopy chest radiographs were obtained after less than 4 hr. In five of these patients, infiltrates were accompanied by fever and/or leukocytosis and oxygen desaturation to less than 90% during the esophagogastroduodenoscopy. CONCLUSION: Clinically significant aspiration pneumonia frequently complicates esophagogastroduodenoscopy in upper GI bleeding patients and is an important mechanism of esophagogastroduodenoscopy-induced hypoxia.     

Cerebral oximetry monitoring provides early warning of hypercyanotic spells in an infant with tetralogy of Fallot

A 3.6-kg, 3-month-old infant with a history of tetralogy of Fallot and increasing hypercyanotic spells was brought to the operating room for operative repair. Before the initiation of cardiopulmonary bypass, it was noted that an abrupt decrease in the cerebral oximetry value occurred before pulse oximetry measured the decrease in oxygen saturation. This happened 4 times, and during all 4 of the hypercyanotic spells, the decrease of the cerebral oximeter value occurred 15 to 30 seconds before a change registered in the pulse oximetry value. For the first time, this case illustrates that cerebral oximetry monitoring may be able to identify the onset of hypercyanotic spells and desaturation before standard pulse oximetry. Cerebral oximetry may provide a quicker identification of acute changes in the clinical status of infants and children by identifying hypoxemia before pulse oximetry.     

The pulse in reflectance pulse oximetry: Modeling and experimental studies

Objective.Reflectance pulse oximetry permits the use of alternative monitoring sites such as the face or torso, and is the approach commonly employed in fetal pulse oximetry systems. The purpose of this study is to investigate the impact of assumptions about the nature of arterial pulsatility on the calibration of such systems. Methods. Monte Carlo simulations of reflectance pulse oximetry were run on a six-layer tissue model, varying depth and magnitude of the arterial pulse. SpO₂ readings on and off the femoral artery obtained during desaturation studies in newborn piglets were compared to predictions. Results. Monte Carlo simulation results clarified the difference between deep and shallow pulsatility found with photon diffusion models, agreeing with earlier in vivo observations. Significant overestimation of SpO₂ 75% and slight underestimation > 75% is expected if a sensor is placed on a highly pulsatile site. The on- and off-artery SpO₂ readings recorded during desaturation in the newborn piglet follow the model predictions. Conclusions. The sensitivity of reflectance pulse oximetry calibration to the depth and magnitude of arterial pulsatility reinforces the observation that monitoring site selection is of importance in optimizing reflectance pulse oximetry performance, particularly fetal pulse oximetry. Sites with palpable pulsatility should be avoided. Reuss JL, Siker D. The pulse in reflectance pulse oximetry: Modeling and experimental studies     

An educational project to improve knowledge related to pulse oximetry.

BACKGROUND: Pulse oximetry is a frequently used, noninvasive monitoring tool for assessing arterial blood oxygenation. Physicians, registered nurses, and respiratory therapists are responsible for the accurate interpretation of pulse oximetry data as part of the evaluation and management of acutely and critically ill patients. OBJECTIVES: (1) To evaluate the extent of current knowledge about pulse oximetry and (2) to increase clinicians' knowledge of research-based practices related to the appropriate use of pulse oximetry and interpretation of its results. METHODS: A test/survey of 17 true-false questions based on the research-based practice protocol of the American Association of Critical-Care Nurses was developed to evaluate current knowledge of pulse oximetry. A convenience sample of medical, nursing, and respiratory therapy staff was invited to complete the test/survey before and several months after an educational program to improve staff members' knowledge of pulse oximetry. The program included educational forums, policy changes, competency checklists, and verification of inclusion of research-based principles in orientation programs. RESULTS: A total of 442 staff members completed the test/survey given before the educational program: 331 nurses, 82 physicians, and 29 respiratory therapists. The overall mean percentage of correct answers was 66%. Differences between disciplines were significant: respiratory therapists scored slightly higher (76%) than did nurses (64%) and physicians (66%) (P = .01). The scores on the test/survey given after the educational program increased significantly, from 66% to 82% (P < .01). CONCLUSIONS: This educational project improved staff members' knowledge of pulse oximetry monitoring.     

The effects of motion artifact and low perfusion on the performance of a new generation of pulse oximeters in volunteers undergoing hypoxemia.

INTRODUCTION: Motion artifact and low perfusion often lead to faulty or absent pulse oximetry readings in clinical practice. OBJECTIVE: Determine the impact of motion artifact and low perfusion on newly introduced pulse oximetry technologies during hypoxemic episodes in healthy volunteers. METHODS: Five different pulse oximeters from 4 manufacturers (the Datex Ohmeda 3900P; the Agilent; the Nellcor N-3000; the Nellcor N-395; and the Schiller OX-1, which is the European version of the Ivy SatGuard 2000 with Masimo SET) were compared with respect to their ability (separated or in combination) to provide accurate readings in the presence of motion artifact and low perfusion. Four of these oximeters represent the latest available oximetry technology, and one (the N-3000) represents a previous generation of oximeters. Oxygen saturation values (S(pO(2))) and pulse rate from the oximeters were recorded during episodes of induced hypoxemia in 10 healthy volunteers. Standardized and repeatable motion artifacts were generated by a motion machine and by having the test subject perform tapping and scratching motions. Perfusion to the finger was reduced by an inflatable balloon impinging on the brachial artery. The pulse oximetry readings from the test oximeters were compared to readings from control pulse oximeters on the unperturbed reference hand. The pulse rates from the test oximeters were compared to the electrocardiographically-measured heart rate. RESULTS: The frequency of faulty readings was increased by increasing motion interference and decreasing perfusion. The S(pO(2)) deviation was within +/- 3% of the reference reading > 95% of the time for all instruments during the control desaturation period in the absence of motion and with normal perfusion. With the combination of motion and low perfusion, the S(pO(2)) error was within +/- 3% less than 62% of the time for all oximeters tested. A significant difference in the frequency of large S(pO(2)) errors was observed only in the direct comparison of the N-395 and N-3000. The N-395 exhibited less frequent S(pO(2)) error exceeding 6% of S(pO(2)) in the combination of the most challenging situations (motion and motion with reduced perfusion). In the same situation the Datex-Ohmeda 3900P and Nellcor N-3000 showed significantly higher pulse rate errors than the other devices (Datex-Ohmeda 3900P 53% of the time and N-3000 37% of the time). CONCLUSIONS: The established model of creating motion artifact and low perfusion is capable of simulating a hierarchy of severe clinical situations. With solely motion or solely reduced perfusion the percentage of errors exceeding +/- 3% of S(pO(2)) increased by 20% and 10%, respectively, compared to the control period. Simultaneous presence of motion and reduced perfusion leads to a relative incidence of > 35% of errors > 3% of S(pO(2)) for the various oximeters. In this situation the N-3000 and the Datex-Ohmeda 3900P exhibited differences between estimated pulse rate and electrocardiographically-measured heart rate > 25 beats/min > 37% of the time.     

洼田吞咽能力评定法联合电视透视吞咽检查对脑卒中患者营养风险的预测价值

目的:探讨洼田吞咽能力评定联合电视透视吞咽检查(VFSS)对脑卒中患者营养风险预测价值。方法:回顾性分析我院脑卒中住院患者病例资料176例,均由管床医生采用洼田吞咽能力评定法对其营养不良风险进行评估,然后采用VFSS行吞咽障碍评估。所有入选对象随访1个月,观察营养不良发生情况,并分析单纯洼田吞咽能力评定法、单纯VFSS评定法及两者联合评估对营养不良风险的预测价值。结果:洼田吞咽能力评定法显示,营养不良风险者42例,VFSS结果显示营养不良风险者41例;随访1个月有38例(21.59%)发生营养不良。洼田吞咽能力评定联合VFSS并联和串联的灵敏度分别为92.11%和55.26%;特异度分别为89.85%和97.10%;准确度分别为90.34%和88.07%;阳性预测值分别为71.43%和84.00%;阴性预测值分别为97.63%和88.74%。结论:洼田吞咽能力评定联合VFSS对脑卒中患者住院营养风险预测价值较高。     

Effect of nail polish on oxygen saturation determined by pulse oximetry in critically ill patients

INTRODUCTION: Nail polish of different colours may alter accuracy and precision of pulse oximetry as previous data in healthy volunteers suggest. This trial evaluates the oxygen saturation determined by pulse oximetry and haematoximetry with nail polish of nine different colours applied. MATERIAL AND METHODS: Fifty critically ill and mechanically ventilated patients in an ICU were investigated in a prospective clinical-experimental trial. On nine finger nails polish of different colours was applied in a predetermined consecutive order. Functional oxygen saturation was determined by pulse oximetry (SpO2) on each finger for each colour with the finger sensor probe both in the normal position and at a 90 degrees rotation. Simultaneously oxygen saturation was determined by haematoximetry (SaO2). Accuracy (bias, DeltaS = SaO2-SpO2) and precision (standard deviation, S.D.) of pulse oximetry were analyzed with the t-test. A value of P < 0.05 was considered significant. RESULTS: While black (DeltaS = +1.6+/-3.0%), purple (DeltaS = +1.2+/-2.6%) and dark blue nail polish (DeltaS = +1.1+/-3.5%, each N = 50) had the greatest effect (P < 0.05), all other colours, including colourless nail polish, had a smaller effect (mean bias +0.2 to +0.9%). A rotation of 90 degrees reduced the bias from +2.8 to +1.3% (N = 10, n.s.). CONCLUSION: Nail polish does not alter pulse oximetry readings in mechanically ventilated patients to a clinically relevant extent. The mean error of measurement for all colours was within the manufacturers' specified range of +/-2%. A 90 degrees rotation of the sensor probe does not eliminate errors in measurement. To remove nail polish might be helpful to decrease the error of measurement in some cases.     

老年脑梗死隐性误吸的高危因素临床研究

【目的】探讨老年脑梗死隐性误吸的高危因素与发生机制,为卒中相关性肺炎的风险评估与早期干预提供参考。【方法】2011年8月至2012年10月入选在本院神经内科住院的急性老年脑梗死患者72例,入院后24 h内完成临床吞咽功能评估,并在7 d内完成吞咽电视荧光透视检查（VFSS）,通过VFSS确定患者有无误吸,记录隐性误吸发生率,分析隐性误吸与年龄、病变部位、临床吞咽异常表现的关系,分析老年脑梗死隐性误吸的高危因素。【结果】完成VFSS检查的72例患者中,误吸者32例,误吸发生率为44．4％（32/72）,其中隐性误吸占13例,占误诊的40．6％（13/32）。60～65岁,66～70岁,71～75岁,76～80岁,＞80岁这五个年龄段的隐性误吸发生率分别为7．7％（1/31）,15．4％（2/13）,23．1％（3/13）,23．1％（3/13）,30．7％（4/13）,年龄越大隐性误吸的发生率就越高。＞80岁患者较60～65岁患者的隐性误吸发生率有统计学差异（ P ＜0．05）。其余各年龄段无统计学差异（ P ＞0．05）。双侧多发性梗死者隐性误吸率46．6％（7/15）,脑干＋小脑梗死者为40％（2/5）,大脑半球＋基底节区梗死者为9．5％,前两组与大脑半球＋基底节区梗死组比较均有统计学差异（ P ＜0．01）。但前两组间的比较无统计学差异（ P ＞0．05）。【结论】急性老年脑梗死患者较容易发生隐性误吸,年龄越大的患者,双侧多发性脑梗死的老年患者发生的几率更高。     

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.     

Noninvasive Hemodynamic Monitoring of Critical Patients in the Emergency Department

Objective : To evaluate the feasibility of multicomponent noninvasive hemodynamic monitoring in critical emergency patients and to compare this technique with simultaneous invasive monitoring by the pulmonary artery thermodilution catheter.
Methods : A prospective observational study was done comparing invasive monitoring and noninvasive monitoring in 60 critically ill or injured patients who required hemodynamic monitoring shortly after entering the ED of a university-affiliated county hospital. Cardiac output (CO) values measured by the standard thennodilution pulmonary artery catheter technique were compared with simultaneously obtained measurements using a noninvasive bioimpedance method. Concurrent measurements were made of pulse oximetry to screen pulmonary function and transcutaneous oximetry to assess tissue perfusion.
Results : The impedance CO values closely approximated those for the thermodilution method; r 0.81, p < 0.001. Significant circulatory abnormalities, including hypotension, reduced cardiac index, arterial hemoglobin desaturation, tissue hypoxia, reduced O₂ delivery, and consumption, were found in 54 of the 60 (90%) patients. The cardiac index decreased in 44% of the patients, the transcutaneous O₂ decreased in 39%. and the O₂ saturation by pulse oximetry fell in 22% during the observation period in the ED (commonly lasting 2–8 hours).
Conclusions: Noninvasive monitoring can provide hemodynamic and perfusion information previously available only by invasive thermodilution catheters. Such noninvasive monitoring can display continuous on-line real-time data, allowing immediate recognition of circulatory abnormalities and providing a means to titrate therapy to appropriate therapeutic goals.     

Effects of a developmental physical therapy program on oxygen saturation and heart rate in preterm infants

To evaluate the physiologic responses of 14 preterm infants to physical therapy, pulse oximetry was used to measure the percentage of arterial oxygen saturation (SaO2) and heart rate during baseline, intervention, and recovery phases. Treatment consisted of six one-minute activities that were equally divided between the side-lying and supported-sitting positions. The order of position and activities was randomly varied. A one-way analysis of variance for repeated measures revealed no significant changes in mean SaO2 as a function of the position or duration of intervention. Mean heart rate increased significantly as a result of intervention (p less than .0001), but there was no significant difference between the baseline and recovery phases. Further analysis indicated that the change in heart rate was not a function of duration of intervention. The results indicate that the preterm infants were able to tolerate the intervention without desaturation. The return of heart rate to baseline values during the recovery phase suggested a normal physiologic response to exercise. Despite some technical limitations, pulse oximetry is recommended to monitor preterm infants during physical therapy.     

The Influence of Larger Subcutaneous Blood Vessels on Pulse Oximetry

OBJECTIVE: Recent studies have renewed interest in reflectance pulse oximetry, specifically for monitoring the patient's forehead. Blood circulation on the forehead immediately above the eyebrow is fed by arteries that branch from the internal carotid artery and lack the vasoconstrictor response present in more peripheral regions. Some investigators question, however, the reliability of monitoring SpO2 on the forehead due to prior reported inaccurate readings with reflectance sensors. The present study evaluates pulse oximetry accuracy when reflectance sensors are placed over potentially pulsing or moving larger arterial vessels, or over more homogeneous microvasculature devoid of larger subcutaneous vessels. METHODS. Ten healthy adult volunteers were fitted with reflectance pulse oximetry sensors and exposed to a controlled desaturation to 70%. Sensors were placed immediately above the left and right eyebrows as well as over the temple. Additionally, numerical modeling was used to simulate light signals and photon migration through a homogeneous tissue bed with an added static or dynamic artery. RESULTS: Sensors placed above the eyebrows tracked one another with significantly better accuracy than when comparing temple with the brow placement (RMS of the Differences = 1.12% vs. 4.24%, respectively). Photon migration simulations indicate that the detected light bypasses the interior of larger vessels, while vessel presence affects the red and IR light pulse amplitudes independent of SaO2. CONCLUSIONS: Placement of reflectance pulse oximetry sensors directly over larger cardio-synchronously pulsing or moving vasculature can significantly degrade SpO2 reading accuracy. Reflectance sensors placed low on the forehead directly over the eyebrow and slightly lateral to the iris appear to avoid such vasculature and provide consistent and accurate estimates of SaO2.     

Predictors of dysphagia after spinal cord injury.

OBJECTIVE: To quantify the incidence of swallowing deficits (dysphagia) and to identify factors that predict risk for dysphagia in the rehabilitation setting following acute traumatic spinal cord injury. DESIGN: Retrospective case-control study. SETTING: Freestanding rehabilitation hospital. PATIENTS: Data were collected on 187 patients with acute traumatic spinal cord injury admitted for rehabilitation over a 4-year period who underwent a swallowing screen, in which 42 underwent a videofluoroscopic swallowing study (VFSS). MAIN OUTCOME MEASURES: VFSS was performed on patients with suspected swallowing problems. Possible antecedents of dysphagia were recorded from the medical record including previous history of spine surgery, surgical approach and technique, tracheostomy and ventilator status, neurologic level of injury, ASIA Impairment Classification, orthosis, etiology of injury, age, and gender. RESULTS: On admission to rehabilitation 22.5% (n = 42) of spinal cord injury patients had symptoms suggesting dysphagia. In 73.8% (n = 31) of these cases, testing confirmed dysphagia (aspiration or requiring a modified diet), while VFSS ruled out dysphagia in 26.2% (n = 11) cases. Logistic regression and other analyses revealed three significant predictors of risk for dysphagia: age (p < .028), tracheostomy and mechanical ventilation (p < .001), and spinal surgery via an anterior cervical approach (p < .016). Other variables analyzed had no relation or at best a slight relation to dysphagia. Tracheostomy at admission was the strongest predictor of dysphagia. The combination of tracheostomy at rehabilitation admission and anterior surgical approach had an extremely high rate of dysphagia (48%). CONCLUSION: Swallowing abnormalities are present in a significant percentage of patients presenting to rehabilitation with acute traumatic cervical spinal cord injury. Patients with a tracheostomy appear to have a substantially increased risk of development of dysphagia, although other factors are also relevant. Risk of dysphagia should be evaluated to decrease the potential for morbidity related to swallowing abnormalities.     

Oxygen desaturation during oesophageal manometry

Eighteen generally fit clinical patients were monitored with pulse oximetry. Mean oxygen saturation levels were lower (P<0.05) during oesophageal manometry (97.7-97.3%) than before it (98.3%). Fourteen out of seventeen (successful) traces had short 4-8% desaturation episodes, and in worst cases there were 8-9 episodes. It seems, therefore, that even patients with no predisposing factors than perhaps smoking and mild bronchial asthma are vulnerable to some oxygen desaturation in oesophageal manometry.     

The accuracy of pulse oximetry in the emergency department

The objective of this retrospective study was to identify factors affecting the accuracy of pulse oximetry in the ED. Over a 3-year period, 664 consecutive emergency department (ED) patients had simultaneous arterial blood gas (ABG) and pulse oximeter readings taken. Pulse oximeter saturations (SpO2) were compared with ABG CO-oximeter saturations (SaO2) for accuracy. Multiple variables including age, sex, hemoglobin, bicarbonate, pH, and carboxyhemoglobin (COHb) were analyzed to see if they affected SpO2 accuracy. ROC curves were used to determine the best pulse oximeter threshold for detecting hypoxia. Using multivariate analysis, COHb was the only statistically significant factor affecting the accuracy of pulse oximetry. In patients with COHb <2%, SpO2 overestimated SaO2 by more than 4% in 8.4% of cases. In patients with COHb > or = 2%, SpO2 overestimated SaO2 by more than 4% in 35% of cases. The best pulse oximetry threshold for detecting hypoxia is 92%. At this threshold, if COHb is <2%, pulse oximetry has a sensitivity of 0.92 and specificity of 0.90. If COHb is > or =2%, sensitivity is 0.74 and specificity is 0.84. For patients likely to have a COHb < 2, pulse oximetry is an effective screening tool for detecting hypoxia. However, more caution must be exercised when using pulse oximetry in patients likely to have a COHb > or = 2%.     

Detection of a systolic pressure threshold for reliable readings in pulse oximetry

OBJECTIVE: To determine the error of measurement in pulse oximetry with a decreased arterial perfusion and to identify a systolic pressure threshold for (1) initial detection and (2) a reliable reading of oxygen saturation. DESIGN: An experimental clinical prospective study. The study was approved by the local ethics committee. SETTING: Eighteen bed intensive care unit at a University hospital. PATIENTS AND PARTICIPANTS: Twenty-five adult mechanically ventilated and critically ill patients in the ICU during a 3-month period. INTERVENTIONS: A blood pressure cuff at the upper arm (same side as an arterial catheter already in place) was inflated to decrease the arterial pulsatile flow. The cuff was deflated stepwise and the resulting oxygen saturation was measured simultaneously. The error of measurement [delta S = SpO2 (baseline)-SpO2 (indicated)] was calculated for each 5 mmHg of blood pressure (BP). MEASUREMENTS AND RESULTS: Twenty-five patients (9 female, 16 male, 48 +/- 15.9 years old) with a mean SpO2 of 98.3 +/- 1.5% and a BP of 129 +/- 18.4 mmHg participated. The mean systolic BP to obtain initial readings with pulse oximetry was 45.8 +/- 17.7 (range, 25-101) mmHg (35% of the baseline pressure) resulting in lower readings of pulse oximetry (mean -11.5 +/- 13.6%, range -45 to +4%). With a systolic BP > 80 mmHg the mean bias was within the manufacturers limits of +/-2%. CONCLUSIONS: Pulse oximetry is reliable with a systolic blood pressure > 80 mmHg. The lower the BP, the lower the pulse oximetry readings leading to a bias of up to -45%.     

脉搏血氧饱和仪对慢性阻塞性肺疾病患者进行血氧监测的价值研究

目的探究慢性阻塞性肺疾病(COPD)患者脉搏血氧饱和度(SpO₂)与动脉血气分析血氧饱和度(SaO₂)的一致性,以确定脉搏血氧饱和仪对COPD患者进行血氧监测的价值。方法收集2019年1-6月我院急诊科收治入院的69例慢性支气管炎和/或肺气肿患者相关数据,根据住院后的肺功能和胸部平扫检查结果分为慢支炎组16例、肺气肿组11例和COPD组42例,用GraphPad Prism 8统计学软件对3组患者的SpO₂值和SaO₂值进行一致性检验(Bland-Altman分析)和偏倚分析;用Excel 2007对3组病例SpO₂值的敏感性、特异性、阴性预测值和阳性预测值进行公式计算。结果 Bland-Altman分析提示,当患者血氧饱和度>90%时,SpO₂值与SaO₂值的差值在"0"上下,随着患者缺氧程度的加重,SaO₂和SpO₂之间的差值也越来越大。3组病例数据均显示其SpO₂     

Pulmonary Embolism Risk Stratification: Pulse Oximetry and Pulmonary Embolism Severity Index

Background: Risk stratification of pulmonary embolism (PE) patients is important to determine appropriate management. Objectives: We evaluated two published risk-stratification tools in emergency department (ED) PE patients: a pulse oximetry cutoff below 92.5% oxygen (at 5280 feet elevation) and the Pulmonary Embolism Severity Index (PESI). Methods: Electronic medical records of all patients diagnosed with PE were abstracted to identify their triage vital signs, co-morbidities, and adverse short-term outcomes (AO) either requiring interventions (defined as respiratory failure, hypotension requiring pressors, and hemodynamic impairment requiring thrombolytics) or resulting in death. We applied these models to our ED PE patients and assessed their performance. Results: There were 168 PE patients identified, with an overall AO rate of 7.1% (12/168), including a 3.0% mortality rate. A room-air pulse oximetry cutoff of 92.5%, for values measured at 5280 feet, classified 89/136 patients as low risk, 1.1% of which had an AO, and 47/136 patients as high risk, of which 10.6% had AO. This pulse oximetry cutoff had a sensitivity of 83% (95% confidence interval [CI] 36–99%), specificity of 68% (95% CI 58–76%), and a negative predictive value (NPV) of 99% (95% CI 93–100%). PESI classified 91/168 patients as low risk (class I or II): 2.2% had AO but none died, and 77/168 were classified as high risk (class III, IV, or V), with an AO rate of 13.0%. A PESI cutoff score of II had a sensitivity of 83% (95% CI 52–98%), specificity of 57% (95% CI 49–65%), and NPV of 98% (95% CI 92–100%). Conclusion: Both PESI and pulse oximetry measurements are moderately accurate identifiers of low-risk patients with PE.