What Is a Good Oxygen Saturation Percentage

Oxygen Saturation

Oxygen saturation (SpO2) measured by pulse oximeter was normal (97% at rest in room air).

From: Pleural Diseases , 2022

Vital Signs

Brian K. Peterson , in Physical Rehabilitation, 2007

NORMAL VALUES

Oxygen saturation values of 95% to 100% are generally considered normal. Values under 90% could quickly lead to a serious deterioration in status, and values under 70% are life-threatening. ²⁹ Patients may deteriorate considerably before there is a dramatic change in oxygen saturation because, as discussed previously, the Pao ₂ may fall from 100 mm Hg to 60 or 70 mm Hg before the oxygen saturation drops to 90%. Signs of deterioration include low BP, increased respiratory rate, and increased pulse rate. ¹³⁷ Other signs of altered oxygen saturation that would indicate checking Spo ₂ are altered respiratory rate; depth or rhythm; unusual breath sounds; cyanotic appearance of nail beds, lips, or mucous membranes; dusky skin; confusion; decreased level of consciousness; and dyspnea. ^1,29

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Care of the Term Infant

Alan R. Spitzer MD , in Fetal and Neonatal Secrets (Third Edition), 2014

Oxygen saturation screening, in which oxygen saturation is less than 95% on day 2 of life, has been demonstrated to identify many of the infants who are not diagnosed during physical examination. Because of the apparent value of this screening, in 2011 the Secretary of Health and Human Services, Kathleen Sebelius, recommended the use of oxygen saturation screening in newborn infants before hospital discharge. ^{∗ †}

14.

Is there any downside to oxygen saturation screening?

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Monitoring Oxygen Status

J.G. Toffaletti , C.R. Rackley , in Advances in Clinical Chemistry, 2016

2.1 Pulse Oximetry

Oxygen saturation ( sO₂) can be measured continuously and noninvasively by pulse oximetry [2,3]. Pulse oximetry uses light absorption through a pulsing capillary bed usually in a toe or finger. The probe uses two LED light sources; one is red (660   nm) and the other is invisible infrared (~   940   nm). Although some light is absorbed by skin and tissue, the only variable absorption is due to arterial pulsations. These absorbance differences at different wavelengths are used to calculate sO₂ for hemoglobin. Because pulse oximetry will not measure the oxygen saturation correctly for other hemoglobins such as met-Hb or CO-Hb, pulse oximetry will not detect CO poisoning. For example, if a patient has an elevated CO-Hb, the %O₂Hb will be decreased, but the pulse oximeter may read a very normal sO₂. A cooximeter, which requires a blood sample, will determine the %O₂Hb (and sO₂ if desired), and the percentages of met-Hb and CO-Hb (see Section 5).

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Pediatric Emergencies

Steven W. Salyer PA‐C , ... Linda L. Lawrence , in Essential Emergency Medicine, 2007

Laboratory Findings

Oxygen saturation monitoring is the standard of care for any pediatric patient with breathing difficulty. Cardiac monitoring is a helpful adjunct. An electrolyte panel can be performed, with special attention paid to the potassium level; hyperkalemia is a contraindication for the use of succinylcholine during rapid sequence intubation (RSI), if required. A CBC can be sent to evaluate the hemoglobin level and a head CT scan can aid in the diagnosis of an inflammatory condition such as epiglottitis. A toxicology screen should be considered in older children and adolescents or when there is a historical indication.

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Invasive Respiratory Support

David Buckley , Michael Gillham , in Cardiothoracic Critical Care, 2007

Monitoring During Weaning

Oxygen saturation, breath rate, tidal volume (if available), and heart rate should be monitored continuously during weaning. A breath rate greater than 30 to 35 breaths per minute, a tidal volume less than 3 to 4 ml/kg, tachycardia, sweating, use of accessory muscles, and intercostal indrawing indicate impending exhaustion.

Pulse oximetry is used to guide F_Io₂ and PEEP settings. Measurements of P_aco₂ and end-tidal carbon dioxide concentration are of little help because they usually increase only once the patient has become overtired. Thus regular measurement of arterial blood gases is not necessary during weaning. Chest radiography should be performed only when clinically indicated.

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Blood Gases

Yacov Rabi MD, FRCPC , ... Namasivayam Ambalavanan MBBS, MD , in Assisted Ventilation of the Neonate (Sixth Edition), 2017

Pulse Oximetry

Oxygen saturation monitoring via pulse oximetry is standard practice in NICUs. While it has reduced the frequency of blood gas testing, it has important limitations. Pulse oximeters work on the principle that saturated hemoglobin (oxyhemoglobin) is a different color from desaturated hemoglobin (deoxyhemoglobin) and thus absorbs light of a different frequency. ^66–68 Oxyhemoglobin demonstrates higher absorbance of infrared light at a wavelength of 940   nm compared to deoxyhemoglobin, which demonstrates a higher absorbance of red light at a wavelength of 660   nm. The ratio of light absorbance at these two wavelengths is used to derive the transcutaneous oxygen saturation.

A probe consisting of a light source and a photosensor is placed so that the light source and photosensor are on opposite sides of each other with tissue in between. As light passes through the tissues, the saturated and desaturated hemoglobin absorb different frequencies of light. By measuring the difference between the ratio of the different frequencies of light absorbed during systole and diastole, the amount of light absorbed due to arterial flow can be calculated. Then, by comparing the absorption at the two appropriate frequencies, the percentage of saturated hemoglobin can be calculated. Refinements of this system include complex algorithms for calculating more exact saturation and for separating arterial pulsations from motion artifact. The calculation of saturation is dependent on sensing light so that ambient light striking the sensor can lead to a false reading.

The so-called functional oxygen saturation measured by pulse oximeters is represented by the equation 100   ×   OxyHb/(OxyHb   +   DeoxyHb), where OxyHb is oxyhemoglobin and DeoxyHb is deoxyhemoglobin. With advancing technology, the number of wavelengths of light employed by some pulse oximeter manufacturers has increased, allowing the pulse oximeter to measure total hemoglobin and other hemoglobin species such as methemoglobin and carboxyhemoglobin. ⁶⁹ However, this technology is quite new and is still undergoing validation in the newborn population.

By focusing only on oxyhemoglobin and deoxyhemoglobin, traditional pulse oximetry may provide misleading values in the setting of elevated levels of other hemoglobin species. In the setting of elevated carboxyhemoglobin levels, pulse oximetry will overestimate oxygen saturation by 1% for every 1% increase in carboxyhemoglobin. ⁷⁰ This occurs because carboxyhemoglobin absorbs light similar to oxyhemoglobin (Fig. 10-10). In contrast, methemoglobin absorbs equal amounts of red and infrared light (see Fig. 10-10). As the amount of methemoglobin increases, the ratio of light absorbance at both wavelengths approaches 1, which corresponds to an oxygen saturation of 85%. ^71,72

Co-oximetry is utilized in modern blood gas analyzers and differs from pulse oximetry in that is uses spectrophotometry to determine the relative concentrations of hemoglobin derivatives by measuring their absorbances of different wavelengths of light. Modern co-oximeters utilize over 100 different wavelengths of light. ⁷³ In this manner, they directly measure several hemoglobin species including oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin, methemoglobin, and sulfhemoglobin. Therefore, they are less prone to error in reporting oxygen saturations compared to pulse oximetry in the presence of different hemoglobin species. The "fractional" oxygen saturation measured by blood gas analyzers is represented by the equation 100 × OxyHb/(OxyHb + DeoxyHb + COHb + MetHb), where OxyHb is oxyhemoglobin, DeoxyHb is deoxyhemoglobin, COHb is carboxyhemoglobin, and MetHb is methemoglobin. In the setting of elevated concentrations of abnormal hemoglobin species, blood gas testing should guide therapy, and pulse oximetry results should be critically examined to determine if they are accurate.

Several factors commonly observed in the newborn patient population do not adversely affect the accuracy of pulse oximetry, however. The presence of fetal hemoglobin, anemia, or hyperbilirubinemia has negligible effects on the accuracy of pulse oximetry. ^74–76

In general, pulse oximeters provide excellent data about oxygenation in the physiologic range. However, the values they provide must be interpreted with care. Poor perfusion, ambient light, and motion all interfere with an adequate signal. Also, different manufacturers use different algorithms for calculating saturation and so may give slightly different results. It is important to know that manufacturers are constantly updating the software in their devices, making many published articles on the limitations of specific devices out of date.

Pulse oximeters are dependent on adequate pulsatile blood flow. In situations such as shock, or if severe edema obscures pulsatile flow, the oximeter may not function reliably. Similarly, in patients on total support from venoarterial ECMO, who have minimal arterial pulsations, many pulse oximeters do not function well if the pulse pressure is less than 10   mm   Hg.

The flat upper part of the S-shaped oxygen–hemoglobin dissociation curve (see Fig. 10-1) makes it difficult for pulse oximeters to differentiate between degrees of hyperoxemia. For example, a Pao₂ of 80 and a Pao₂ of 180   mm   Hg both represent essentially 100% saturation in a preterm neonate. Some clinicians suggest that this is a significant limitation of pulse oximetry compared with transcutaneous oxygen monitoring, particularly as avoiding hyperoxemia to decrease the risk of retinopathy of prematurity is an important priority in neonates. ⁷⁷ Pulse oximeters are also less accurate in the low end of the saturation range (e.g., less than 70% saturation) than in the normal physiologic range. Fortunately, this does not usually pose a clinically significant problem because the exact degree of severe desaturation is usually less important for clinical decision making than the occurrence of the desaturation itself.

One major advantage of pulse oximetry is that oxygen saturation is a better indicator of oxygen content than is Pao₂, as saturation is a variable in calculating oxygen carried by hemoglobin (the major contributor to oxygen content in blood), whereas Pao₂ represents dissolved oxygen, which is only a minor, yet important, component of oxygen transport.

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Invasive Procedures

Myung K. Park MD, FAAP, FACC , in Pediatric Cardiology for Practitioners (Fifth Edition), 2008

NORMAL HEMODYNAMIC VALUES

Normal oxygen saturation in the right side of the heart is usually 70% but it may vary between 65% and 80%, depending on cardiac output. Left-sided saturations are usually 95% to 98% in room air. In newborns and heavily sedated children, the oxygen saturation may be lower. Pressures are lower in the right side than in the left side of the heart, with systolic pressures in the right ventricle (RV) and pulmonary artery (PA) about 20% to 30% of those in the left side of the heart ( Fig. 7-1).

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Pulmonary Physiology

Andrew B. Lumb , ... Kai Kuck , in Pharmacology and Physiology for Anesthesia (Second Edition), 2019

Background

Hemoglobin oxygen saturation—or "oxygen saturation," as it is commonly referred to in clinical practice—is the proportion of total hemoglobin in blood that is oxyhemoglobin (i.e., hemoglobin bound to oxygen), expressed as a percentage and abbreviated SaO ₂ (for arterial saturation) or SvO₂ (for venous saturation). Oxygen saturation is an important variable in determining blood oxygen content and oxygen delivery. First described in 1972 by Aoyagi in Japan, ¹ pulse oximetry provides a continuous, noninvasive estimation of SaO₂ that previously could only be measured periodically by analyzing blood ex vivo in a blood gas analyzer after obtaining an arterial blood sample. Because of its perceived clinical utility, pulse oximetry quickly emerged as a standard monitor to assess the adequacy of oxygenation in perioperative and critical care settings. Understanding the scientific and technical concepts underpinning pulse oximetry is essential for the practitioner to apply the technology appropriately, including recognition of artifactual signals.

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Cardiovascular Physiology in Infants and Children

Maureen A. Strafford , in Smith's Anesthesia for Infants and Children (Seventh Edition), 2006

Oxygen Content and Saturation.

Oxygen saturation is the percent of hemoglobin present as oxyhemoglobin; it is measured directly with oximetry. Oxygen capacity is the maximal amount of oxygen that can be bound to hemoglobin. This value is calculated by multiplying the patient's hemoglobin by 1.34 and is expressed in milliliters per 100 milliliters. Oxygen content is thetotal amount of oxygen present in blood and includes oxygen bound to oxyhemoglobin as well as oxygen dissolved in the plasma. Oxygen content is the product of the oxygen saturation value multiplied by 1.34 multiplied by 10, where 1.34 is the amount of O₂ that 1 g of hemoglobin carries when fully saturated. The number 10 converts 100 mL to liters. Dissolved oxygen is usually ignored because it is so small. However, when Po ₂ is high, dissolved oxygen may be high and must be considered. Dissolved oxygen is equal to Pao ₂ × 0.003 mL/100 mL. Oxygen content and oxygen consumption (

o ₂) must be known to calculate systemic and pulmonary blood flow.

Pulmonary blood flow

${\dot{\text{Q}}}_{\text{P}}=\frac{{\dot{\text{V}}\text{o}}_{\text{2}}[mL/min]}{{\text{P}\dot{\text{V}}\text{o}}_{\text{2}}{\text{content}-\text{Pao}}_{\text{2}}\text{content}}$

Systemic blood flow

${\dot{\text{Q}}}_{\text{P}}=\frac{{\dot{\text{V}}\text{o}}_{\text{2}}[mL/min]}{{\text{Sao}}_{\text{2}}{\text{content}-\text{M}\dot{\text{V}}\text{o}}_{\text{2}}\text{content}}$

where P

o ₂ is the oxygen content in the pulmonary vein, Pao ₂ is the oxygen content in the pulmonary artery, Sao ₂ is the oxygen content in a systemic artery or aorta, and M

o ₂ is the oxygen content in a mixed venous sample.

The mixed venous oxygen content should be the same in the RA as in the pulmonary artery if no shunts are present. However, venous blood is poorly mixed in the RA where streaming and large variations in oxygen content are normally seen, as in coronary sinus return. Mixing on the left side of the heart is much more uniform. Saturation data become important in the detection and quantification of shunt flow.

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Arterial and Venous Blood Gases

Luciano Gattinoni , Eleonora Carlesso , in Critical Care Nephrology (Second Edition), 2009

Hemoglobin Oxygen Saturation

Hemoglobin oxygen saturation (SatHb), measured by infrared spectroscopy, is the statistical average of all oxygen bound to hemoglobin molecules relative to the total amount that could be bound. Indeed, a saturation of 90% HbO₂ indicates that 90% of the binding sites of hemoglobin are actually bound to oxygen molecules. Such a saturation value implies that most of the hemoglobin molecules carry four molecules of oxygen each, some three, and a few others two or one. The relationship between the oxygen tension (P_o2) and hemoglobin saturation is the oxygen dissociation curve. The S shape of this curve indicates that the affinity of hemoglobin for oxygen increases with rising O₂ saturation (cooperative oxygen binding). However, under physiological conditions, the P_o2-SatHb relationship depends largely on heterotropic molecules. ⁵ The major regulators of O₂ affinity are protons (Bohr effect); an increase in proton concentration decreases oxygen affinity. 2,3-Diphosphoglyceric acid, a metabolite of the glycolytic pathway, as well as chloride ion (Cl⁻) shift, reduce the O₂ affinity with human hemoglobin. A minor role in oxygen affinity is played by carbon dioxide, which shares binding sites with 2,3-diphosphoglyceric acid. Several attempts to compute oxygen saturation from P_o2 have been performed, first by Hill, ⁶ later by Adair ⁷ ; subsequently, several models have been proposed and implemented in blood gas machines. ⁸ However, owing to the large number of covariables that may affect the oxygen dissociation curve, the direct measurement of hemoglobin oxygen saturation is highly recommended.

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What Is a Good Oxygen Saturation Percentage

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