Happy hypoxia in COVID-19: pathophysiology and pulse oximetry accuracy

2021 ◽  
Vol 13 (7) ◽  
pp. 288-296
Author(s):  
Noamaan Wilson-Baig
Keyword(s):  
Hospital Mortality ◽  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Disease Severity ◽  
Pulse Oximeter ◽  
Clinical Presentation ◽  
Recent Literature ◽  
Oxygen Fraction ◽  
The Relationship ◽  
Inspired Oxygen

Many patients with COVID-19 have presented to emergency departments with arterial hypoxaemia but without breathlessness; this is called ‘happy hypoxia’ or, more accurately, ‘silent hypoxaemia’. Hypoxaemia needs to be identified correctly in patients with COVID-19 as it is associated with in-hospital mortality. The aetiology of silent hypoxia is unclear, and the pathophysiological processes involved in the relationship between the response to hypoxaemia and the sensation of dyspnoea may explain its clinical presentation. Pulse oximetry is used routinely to measure oxygen saturation. However, recent literature has questioned its accuracy in patients with COVID-19. Inaccuracies in readings, which arise for several reasons, could in part explain silent hypoxaemia. Caution should be taken when interpreting pulse oximeter readings or patients could be given a higher inspired oxygen fraction than necessary. Silent hypoxaemia may also mask disease severity in patients with COVID-19.

scholarly journals Relating oxygen partial pressure, saturation and content: the haemoglobin–oxygen dissociation curve

Breathe ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 194-201 ◽  
Author(s):  
Julie-Ann Collins ◽  
Aram Rudenski ◽  
John Gibson ◽  
Luke Howard ◽  
Ronan O’Driscoll
Keyword(s):  
Oxygen Saturation ◽  
Partial Pressure ◽  
Pulse Oximetry ◽  
Blood Gas Analysis ◽  
Gas Analysis ◽  
Oxygen Dissociation Curve ◽  
Blood Gas ◽  
Dissociation Curve ◽  
Oxygen Dissociation ◽  
The Relationship

Key PointsIn clinical practice, the level of arterial oxygenation can be measured either directly by blood gas sampling to measure partial pressure (PaO2) and percentage saturation (SaO2) or indirectly by pulse oximetry (SpO2).This review addresses the strengths and weaknesses of each of these tests and gives advice on their clinical use.The haemoglobin–oxygen dissociation curve describing the relationship between oxygen partial pressure and saturation can be modelled mathematically and routinely obtained clinical data support the accuracy of a historical equation used to describe this relationship.Educational AimsTo understand how oxygen is delivered to the tissues.To understand the relationships between oxygen saturation, partial pressure, content and tissue delivery.The clinical relevance of the haemoglobin–oxygen dissociation curve will be reviewed and we will show how a mathematical model of the curve, derived in the 1960s from limited laboratory data, accurately describes the relationship between oxygen saturation and partial pressure in a large number of routinely obtained clinical samples.To understand the role of pulse oximetry in clinical practice.To understand the differences between arterial, capillary and venous blood gas samples and the role of their measurement in clinical practice.The delivery of oxygen by arterial blood to the tissues of the body has a number of critical determinants including blood oxygen concentration (content), saturation (SO2) and partial pressure, haemoglobin concentration and cardiac output, including its distribution. The haemoglobin–oxygen dissociation curve, a graphical representation of the relationship between oxygen satur­ation and oxygen partial pressure helps us to understand some of the principles underpinning this process. Historically this curve was derived from very limited data based on blood samples from small numbers of healthy subjects which were manipulated in vitro and ultimately determined by equations such as those described by Severinghaus in 1979. In a study of 3524 clinical specimens, we found that this equation estimated the SO2 in blood from patients with normal pH and SO2 >70% with remarkable accuracy and, to our knowledge, this is the first large-scale validation of this equation using clinical samples. Oxygen saturation by pulse oximetry (SpO2) is nowadays the standard clinical method for assessing arterial oxygen saturation, providing a convenient, pain-free means of continuously assessing oxygenation, provided the interpreting clinician is aware of important limitations. The use of pulse oximetry reduces the need for arterial blood gas analysis (SaO2) as many patients who are not at risk of hypercapnic respiratory failure or metabolic acidosis and have acceptable SpO2 do not necessarily require blood gas analysis. While arterial sampling remains the gold-standard method of assessing ventilation and oxygenation, in those patients in whom blood gas analysis is indicated, arterialised capillary samples also have a valuable role in patient care. The clinical role of venous blood gases however remains less well defined.

Measurement of Carboxyhemoglobin and Methemoglobin by Pulse Oximetry

2006 ◽  
Vol 105 (5) ◽  
pp. 892-897 ◽  
Author(s):  
Steven J. Barker ◽  
Jeremy Curry ◽  
Daniel Redford ◽  
Scott Morgan
Keyword(s):  
Carbon Monoxide ◽  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Sodium Nitrite ◽  
Pulse Oximeter ◽  
Hemoglobin Oxygen Saturation ◽  
Arterial Blood ◽  
Human Volunteers ◽  
Oxygenation Monitoring ◽  
Intravenous Sodium

Background A new eight-wavelength pulse oximeter is designed to measure methemoglobin and carboxyhemoglobin, in addition to the usual measurements of hemoglobin oxygen saturation and pulse rate. This study examines this device's ability to measure dyshemoglobins in human volunteers in whom controlled levels of methemoglobin and carboxyhemoglobin are induced. Methods Ten volunteers breathed 500 ppm carbon monoxide until their carboxyhemoglobin levels reached 15%, and 10 different volunteers received intravenous sodium nitrite, 300 mg, to induce methemoglobin. All were instrumented with arterial cannulas and six Masimo Rad-57 (Masimo Inc., Irvine, CA) pulse oximeter sensors. Arterial blood was analyzed by three laboratory CO-oximeters, and the resulting carboxyhemoglobin and methemoglobin measurements were compared with the corresponding pulse oximeter readings. Results The Rad-57 measured carboxyhemoglobin with an uncertainty of +/-2% within the range of 0-15%, and it measured methemoglobin with an uncertainty of 0.5% within the range of 0-12%. Conclusion The Masimo Rad-57 is the first commercially available pulse oximeter that can measure methemoglobin and carboxyhemoglobin, and it therefore represents an expansion of our oxygenation monitoring capability.

Concurrent Validity of Arterial Blood Oxygen Saturation Measurements: A Preliminary Analysis of an iPad Pulse Oximeter and Traditional Pulse Oximeter Using Bluetooth

2014 ◽  
Vol 19 (3) ◽  
pp. 37-42
Author(s):  
Scott Cheatham ◽  
Morey J. Kolber ◽  
Michael P. Ernst
Keyword(s):  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Pulse Rate ◽  
Pulse Oximeter ◽  
Concurrent Validity ◽  
Outcome Measure ◽  
Blood Oxygen ◽  
Short Term ◽  
Blood Oxygen Saturation ◽  
Main Outcome Measure

Context:Pulse oximetry has become mobile with the use of smartphone and Bluetooth wireless technology. This technology offers many benefits but has not been extensively studied. There is a need to further validate its clinimetric properties for health professionals to provide proper guidance to patients.Objective:This investigation assessed the concurrent validity of the iSpO2pulse oximeter against a traditional pulse oximeter in measuring short-term resting blood oxygen saturation (SpO2) and pulse rate.Design:Observational study of reliability.Setting:University kinesiology laboratory.Participants:Thirty healthy, recre-ationally active adults (18 men, 12 women; mean age = 25.7 ± 5.46 years, mean height = 170.3cm ± 9.51, mean body mass = 76.4 kg ± 19.33).Intervention:Resting measurement of SpO2and pulse rate using the iSpO2pulse oximeter with the iPad Mini and a traditional pulse oximeter with Bluetooth.Main Outcome Measure:Resting SpO2and pulse rate were concurrently measured over 5 min.Results:The concurrent validity between the iSpO2and traditional pulse oximeter was moderate for measuring SpO2, intraclass correlation coeffcient (ICC)(3, 1) = .73,SEM= 0.70%, and good for pulse rate, ICC(3, 1) = .97,SEM= 1.74 beats per minute (bpm). The minimal detectable change at the 95% confidence interval for both instruments suggests that there may be 1.94% disagreement for SpO2and 4.82 bpm disagreement between pulse oximetry methods. The 95% limits of agreement (LoA) for measuring SpO2suggests that the iSpO2and traditional pulse oximeters may vary -0.28 ± 1.98%, or approximately 2%. The 95% LoA for measuring pulse rate suggests that the iSpO2and traditional pulse oximeter may vary 1.74 ± 4.98 bpm, potentially upward of 6 bpm. On the basis of the results of the LoA, it appears that there may be a slight systematic bias between the two devices, with the traditional pulse oximeter producing higher pulse rates than the iSpO2.Conclusion:The findings suggest that both instruments may be beneficial for indirect short-term measurements of resting SpO2and pulse rate.

scholarly journals Admission Oxygen Saturation and Mortality in Acute Pulmonary Embolism Patients: Observational Data From Large ICU Databases

2021 ◽  
Author(s):  
Xiaolin Xu ◽  
Anping Peng ◽  
Jing Tian ◽  
Runnan Shen ◽  
Guochang You ◽  
...  
Keyword(s):  
Pulmonary Embolism ◽  
Logistic Regression ◽  
Intensive Care ◽  
Hospital Mortality ◽  
Oxygen Saturation ◽  
Acute Pulmonary Embolism ◽  
Research Database ◽  
Optimal Range ◽  
Subgroup Analyses ◽  
The Relationship

Abstract Background The relationship between blood oxygenation and clinical outcomes of acute pulmonary embolism (APE) patients in intensive care unit (ICU) is unclear, which could be nonlinear. The study aimed to determine the association between admission pulse oximetry-derived oxygen saturation (SpO2) levels and mortality, and to determine the optimal range with real-world data. Methods Patients diagnosed with APE on admission and staying in ICU for at least 24 hours in the Medical Information Mart for Intensive Care III (MIMIC-III) database and the eICU Collaborative Research Database (eICU-CRD) were included. Logistic regression and restricted cubic spline (RCS) models were applied to determine the nonlinear relationship between mean SpO2 levels within the first 24 hours after ICU admission and in-hospital mortality, from which we derived an optimal range of SpO2. Subgroup analyses were based on demographics, treatment information, scoring system and comorbidities. Results We included 1109 patients who fulfilled inclusion criteria, among whom 129 (12%) died during hospitalization and 80 (7.2%) died in ICU. The RCS showed that the relationship between admission SpO2 levels and in-hospital mortality of APE patients was nonlinear and U-shaped. The optimal range of SpO2 with the lowest mortality was 95–98%. Multivariate stepwise logistic regression analysis with backward elimination confirmed that the admission SpO2 levels of 95%-98% was associated with decreased hospital mortality compared to the group with SpO2 < 95% (Odds ratio [OR] = 2.321; 95% confidence interval [CI]: 1.405–3.786; P < 0.001) and 100% (OR = 2.853; 95% CI: 1.294–5.936; P = 0.007), but there was no significant difference compared with 99% SpO2 (OR = 0.670, 95% CI: 0.326–1.287; P > 0.05). This association was consistent across subgroup analyses. Conclusions The relationship between admission SpO2 levels and in-hospital mortality followed a U-shaped curve among patients with APE. The optimal range of SpO2 for APE patients was 95–98%.

scholarly journals Correlation between hepatopulmonary syndrome and oxygen saturation pulse oximetry in cirrhotic patients

2020 ◽  
Vol 66 (11) ◽  
pp. 1577-1582
Author(s):  
Sara Cardoso Paes Rose ◽  
Débora Vilela Cunha ◽  
Sandra de Barros Cobra Medeiros ◽  
José Eduardo Trevizoli ◽  
Marcos de Vasconcelos Carneiro ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Statistical Significance ◽  
Hepatopulmonary Syndrome ◽  
Gas Analysis ◽  
Saturation Pulse ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Cirrhotic Patients ◽  
The Relationship

SUMMARY Hepatopulmonary Syndrome (HPS) is a complication of cirrhosis that worsens the disease's prognosis, pre and post liver transplant. The objective of this study is to analyze the prevalence of HPS in cirrhotic patients at our service and to correlate it with oxygen saturation (SatO2) using a pulse oximeter to evaluate if this is useful as a screening test for HPS. A prospective study was conducted in patients with hepatic cirrhosis conventionally selected from 2014 to 2016. All the patients underwent an echocardiogram with microbubbles and oxygen saturation measurement by pulse oximetry. Those with intrapulmonary shunt were submitted to arterial blood gas analysis. The relationship between oxygen saturation and HPS was assessed by the multivariate model of binary logistic regression. We analyzed 77 patients, and 23.3% (18 patients) had all criteria for HPS. The relationship between HPS and SatO2 did not show statistical significance, even after the variables were adjusted for sex, age, and smoking. Oxygen saturation alone was not able to detect HPS in the sample of cirrhotic patients. More accurate methods for screening and diagnosis of the syndrome should be used.

In Vivo Evaluation of Customized Pulse Oximeter and Sensitivity Pulp Tests for Assessment Of Pulp Vitality

2019 ◽  
Vol 43 (1) ◽  
pp. 11-15
Author(s):  
Divya S Sharma ◽  
Shikha Mishra ◽  
Naveen Reddy Banda ◽  
Sneha Vaswani
Keyword(s):  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Pulse Oximeter ◽  
Permanent Teeth ◽  
In Vivo Evaluation ◽  
Thermal Tests ◽  
Valuable Adjunct ◽  
Pulp Vitality ◽  
Group 2

Objective: The purpose of this study was to test a customized pulse oximeter (CPO) for evaluation of pulp vitality in primary and permanent teeth against clinical diagnosis (vital and untreated non-vital) in order to expand its clinical use for pulp preservation. Study design: CPO was evaluated on intact primary and permanent central or lateral incisor (CI, LI) teeth-vital (group 1, 20n each); untreated non-vital (group 2, 10n each) and; root filled non-vital (group 3, 10n each) of children 4–12 years according to inclusion/ exclusion criteria. For each patient CPO was first applied on finger followed by vitality tests in following sequence-electrical, pulse oximetry and thermal tests. Results: Mean oxygen saturation (%SpO2) in permanent and primary–vital teeth was 88.78% & 87.77% respectively; non-vital teeth was 74.67% & 75.00% respectively; and in all root filled teeth was 0%. Tooth and finger oxygen saturation values showed strong positive relationship in vital primary or permanent teeth and; no correlation in untreated non-vital primary or permanent teeth. The accuracy rate of thermal pulp test and pulse oximetry was 100% and for electrical pulp test it was 90% for permanent and 86.67% for primary teeth. Conclusion: The CPO tested in this study proved to be a valuable adjunct for diagnosing pulp vitality by objective means.

scholarly journals Relationship between Ventilator-Associated Events and Timing of Rehabilitation in Subjects with Emergency Tracheal Intubation at Early Mobilization Facility

2018 ◽  
Vol 15 (12) ◽  
pp. 2892 ◽  
Author(s):  
Taku Shinoda ◽  
Hiromasa Nishihara ◽  
Takayuki Shimogai ◽  
Tsubasa Ito ◽  
Ryuya Takimoto ◽  
...  
Keyword(s):  
Intensive Care Unit ◽  
Mechanical Ventilation ◽  
Tracheal Intubation ◽  
High Mortality ◽  
Early Mobilization ◽  
Positive End Expiratory Pressure ◽  
Rehabilitation Intervention ◽  
Oxygen Fraction ◽  
The Relationship ◽  
Inspired Oxygen

The present study aimed to investigate the relationship between the occurrence of ventilator-associated events (VAE) in the intensive care unit and the timing of rehabilitation intervention. We included subjects who underwent emergency tracheal intubation and received rehabilitation. We performed rehabilitation according to our hospital’s protocol. We assessed the mechanical ventilation parameters of inspired oxygen fraction and positive-end expiratory pressure, and a VAE was identified if these parameters stabilized or decreased for ≥2 days and then had to be increased for ≥2 days. We defined time in hours from tracheal intubation to the first rehabilitation intervention as Timing 1 and that to first sitting on the edge of the bed as Timing 2. Data were analyzed by the t-test and χ2 tests. We finally analyzed 294 subjects. VAE occurred in 9.9% and high mortality at 48.3%. Median values of Timing 1 and Timing 2 in the non-VAE and VAE groups were 30.3 ± 24.0 and 30.0 ± 20.7 h, and 125.7 ± 136.6 and 127.9 ± 111.4 h, respectively, and the differences were not significant (p = 0.95 and p = 0.93, respectively). We found no significant relationship between the occurrence of VAE leading to high mortality and timing of rehabilitation intervention.

scholarly journals Accuracy and precision of pulse oximeter at different sensor locations in patients with heart failure

2021 ◽  
Vol 16 ◽  
Author(s):  
Alaa Thabet Hassan ◽  
Soher Mostafa Ahmed ◽  
Azza Salah AbdelHaffeez ◽  
Sherif A.A. Mohamed
Keyword(s):  
Heart Failure ◽  
Oxygen Saturation ◽  
Pulse Oximetry ◽  
Pulse Oximeter ◽  
Arterial Oxygen Saturation ◽  
Arterial Oxygen ◽  
St Segment Elevation ◽  
Accuracy And Precision ◽  
St Segment ◽  
Patients With Heart Failure

Background: Despite its wide use in clinical practice, few studies had assessed the role of pulse oximetry in patients with heart failure. We aimed to evaluate the accuracy and precision of the pulse oximeter in patients with heart failure and to determine this accuracy at three different sensor locations.Methods: Comparison of pulse oximetry reading (SpO2) with arterial oxygen saturation (SaO2) was reported in 3 groups of patients with heart failure (HF); those with ejection fraction (EF) >40%, those with EF <40%, and those with acute HF (AHF) with ST and non-ST segment elevation acute myocardial infarction (STEMI and non-STEMI).Results: A total of 235 patients and 90 control subjects were enrolled. There were significant differences in O2 saturation between control and patients’ groups when O2 saturation is measured at the finger and toe, but not the ear probes; p=0.029, p=0.049, and 0.051, respectively. In HF with EF>40% and AHF with O2 saturations >90%, finger oximetry is the most accurate and reliable, while in HF with EF<40% and in patients with AHF with O2 saturations <90%, ear oximetry is the most accurate.Conclusion: Pulse oximetry is a reliable tool in assessing oxygen saturation in patients with heart failure of different severity. In HF with EF>40% and in AHF with O2 saturations >90%, finger oximetry is the most accurate and reliable, while in HF with EF<40% and in patients with AHF with O2 saturations <90%, ear oximetry is the most accurate. Further studies are warranted.

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