Hi all, My question is in regards to the actual meaning of the SPO2 score and range we see. In particular, what is the meaning of the range? When we see, say, a score of 94% and a range of 91% - 97%, is the range corresponding to the minimum and maximum SPO2 values observed during sleep? Spo2 94-95% periodically all day while sitting or lying flat. Fluctuates back up to 98-97% but doesn't stay there. Up and down hr as well. 1 doctor answer. 1 doctor weighed in. Clarence Grim answered. Endocrinology 57 years experience. Using a pulse oximeter device, saturation of peripheral oxygen (SpO2) is an estimation of the oxygen saturation level. For a regular healthy person, the normal blood oxygen saturation level (SpO2) is around 94% to 99%. For patients with mild respiratory diseases, the SpO2 is around 90% or above. Spo2 or the saturation of oxygen measures the oxygen content in the blood. The device mainly function based on the beer lamberts law I.e measured the amount of light which passes through the tissues and detected by the sensors. Spo2 below 92% in young individuals and below 90% in older individuals warrants medical intervention.
ISSN 0004 - 5772
Abstract
Across the world healthcare systems are dealing with COVID 19. One of the main manifestations of this infection is varied degree of involvement of lung causing a spectrum of illness from mild lower respiratory tract infection to severe Adult Respiratory Distress Syndrome (ARDS). One of the important clinical parameters is to identify hypoxia early to initiate higher level of care at the earliest. However, presence of silent or latent hypoxia has made this task a challenge in COVID 19. A simple 6-minute walk test (6MWT) to look for inducible hypoxia for a patient who looks comfortable and is not hypoxic at rest, helps in early detection of hypoxia and initiating early higher-level care. The 6MWT also helps in looking for discharge preparedness of patient. This simple tool has immense clinical applicability to ensure safe care of COVID 19 patients.
COVID 19 has manifested in several forms but to unmask latent hypoxia is the key to save lives and its imperative to have an easy clinical tool to screen for the same. While many protocols have been developed for risk stratification like National Early Warning Signs 2 (NEWS 2), SOFA score neither have the ability to predict hypoxia. Pulmonary manifestation of covid19 can be easily picked up by a simple user friendly 6 miniute walk test which can detect desaturation to pick up silent hypoxia which has been often referred to as “happy hypoxia”.1 Another observation in COVID 19 patients is at rest they appear comfortable and saturation are maintained above 94%, however mild exertion like using washroom often makes them hypoxic and/or short of breath. Thus, in this group of patients, it is important to identify hypoxia early, stratify the risk and plan treatment.
A simple 6 minutes’ walk test (6MWT)2 is a reliable tool to assess cardiorespiratory effort tolerance in chronic lung and chronic heart failure patients. Traditionally the test involves measuring the heart rate and blood pressure along with oxygen saturation using a finger pulse oximeter probe. Jenkins et al3 proposed a stopping criterion for the test based on drop in the measured oxygen saturation (SpO2) by finger probe. The test provides a global assessment of the cardio-pulmonary reserves. A simple effort of walking at a steady pace in patients with compromised cardio respiratory reserves may precipitate a drop in oxygen saturation. There are many physiological variables which may be attributed to drop in saturation, however the most important been hearts inability to improve cardiac output and second, decrease in lung diffusion capacity which can be due to lung infiltration due to COVID 19 pneumonia and/or due to alveolar capillary micro thrombi in the pulmonary circulation (pulmonary vascular endothilitis).4 The 6-minute walk test can also predict the anaerobic threshold in patients. Anaerobic threshold is a reflection of combine efficiency of heart, lung and circulation and marks the onset of anaerobic metabolism due to oxygen deficit secondary to inadequate oxygen delivery. Sinclair et al5 in 110 patients used 6MWT to derive the anaerobic threshold in patients awaiting non cardiac surgery.
A classic 6-minute walk test (6MWT)as described in American Thoracic Society statement6 is used for measuring response to medical interventions in patients with moderate to severe cardiac or pulmonary disease, it assesses one-time functional status of patient and predict morbidity and mortality. The principle of 6-minute walk test in COVID 19 is to identify patients who are not hypoxic at rest, but become hypoxic (silent Hypoxia) on 6-minute walk test. The 6MWT will ascertain evidence of hypoxia identified by SpO2 less than 94% or an absolute drop in SpO2 by more than 3% from base line during or at end of the test. Patients over 60 years of age may have a shorter- 3-minute walk test (3MWT) if they are unable to perform a 6-minute test. The test is indicated in all COVID-19 positive patients who are not hypoxic or short of breath at rest. The test is contraindicated if patient is hypoxic at rest SpO2 < 94 %, Short of breath at rest, not able to walk unassisted, Eisenmenger’s syndrome, severe anaemia, known patient of unstable angina or valvular heart disease.
The 6MWT can be performed at home or hospital, one person either family member or healthcare worker supervises the test. Patient fulfils the prerequisite indication to identify latent or silent hypoxia and there is no contraindication. Patient is requested to wear a simple cloth or three-ply mask. A base line saturation using finger pulse oximeter probe is noted. Patient is requested to start walking in confines of his room, it is a self-paced test, and patient can do as many laps as he can in confines of room. At end of 6 minutes a repeat reading of saturation is taken, a positive test for hypoxia is if SpO2 is less than 94% or there is an absolute drop of SpO2 by 3% or more from baseline. If patient feels lightheaded, unwell or short of breath during the walk, then test should be aborted, patient rested and SpO2 checked. Similarly, patients over 60 years of age, an interim reading of SpO2 at 3 minutes and supervisor of test assessing the need to complete 6 minutes or stop is mandatory.
A positive test mandates higher level care, this means patients who are home quarantined need to present to emergency department of hospital, similarly on treatment ward patients may need to be shifted to High Dependency Unit (HDU) or Intensive Care Unit (ICU). The test also helps doctors to seek additional laboratory information like CRP, D-dimer, Ferritin and IL6 as needed. The test should be repeated again closer to discharge day to assess discharge readiness, it assesses cardiorespiratory reserve post recovery and completes a comprehensive clinical assessment for readiness to discharge. Giannitis et al7 proposed to do the test closer to discharge day in patients with heart failure to assess the cardio respiratory functional status of the patient.
Summary
The 6MWT is a simple and effective test to assess the silent hypoxia, it helps in identifying patients early who have a potential to deteriorate. This simple intervention would help in initiating appropriate esclation of level of care and treatment. The ease of doing a self paced test may be tempting, but it needs to be performed under supervision and if positive for hypoxia then necessary action needs to be initiated. It can also be used to assess discharge readiness. The simplicity, improvement of margin of safety and prompting early intervention make this test an important tool in COVID 19 patient management.
References
- Wilkerson RG, Adler JD, Shah NG, et al. Silent hypoxia: A harbinger of clinical deterioration in patients with COVID-19. Am J Emerg Med 2020 May 22.
- Singh SJ, Puhan MA, Andrianopoulos V, et al. An official systematic review of the European Respiratory Society/American Thoracic Society: measurement properties of field walking tests in chronic respiratory disease. Eur Respir J 2014; 44:1447–1478.
- Jenkins S, Cecins N . Six-minute walk test: observed adverse events and oxygen desaturation in a large cohort of patients with chronic lung disease. Intern Med J 2011; 41:416–22.
- Ackermann M, Verleden SE et al Pulmonary vascular endothilitis, thrombosis and angiogenesis in COVID -19. N Engl J Med 2020; 383:120-128.
- Sinclair RC, Batterham AM, Davies S, Cawthorn L, Danjoux GR. Validity of the 6 min walk test in prediction of the anaerobic threshold before major non-cardiac surgery. Br J Anaesth 2012; 108:30–35.
- American Thoracic Society (ATS) Statement: Guidelines for Six-minute walk test. Am J Respir Crit Care Med 2002; 166:111–117.
- Giannitsi S, Bougiaklo M, Bechlioulis A, Kotsia A, Michalis LK, Naka KK. 6 minute walk test:a useful tool in the management of heart failure patients. Ther Adv Cardiovasc Dis 2019; 13.
Know the steps to take to identify and treat low SpO2 levels
What is SpO2?
SpO2, also known as oxygen saturation, is a measure of the amount of oxygen-carrying hemoglobin in the blood relative to the amount of hemoglobin not carrying oxygen. The body needs there to be a certain level of oxygen in the blood or it will not function as efficiently. In fact, very low levels of SpO2 can result in very serious symptoms. This condition is known as hypoxemia. There is a visible effect on the skin, known as cyanosis due to the blue (cyan) tint it takes on. Hypoxemia (low levels of oxygen in the blood) can turn into hypoxia (low levels of oxygen in the tissue). This progression and the difference between the two conditions is important to understand.
How the Body Maintains Normal SpO2 levels
It is vital to maintain normal oxygen saturation levels in order to prevent hypoxia. Thankfully, the body usually does this by itself. The most important way that the body maintains healthy SpO2 levels is through breathing. The lungs take oxygen that has been inhaled and binds it to hemoglobin that then travels throughout the body with the payload of oxygen. The oxygen needs of the body increase during times of high physiological stress (e.g., lifting weights or running) and at higher altitudes. The body is usually able to adapt to these increases, provided that they are not too extreme.
Measuring SpO2
There are many ways that the blood can be tested to ensure it contains normal oxygen levels. The most common way is to use a pulse oximeter to measure the SpO2 levels in the blood. Pulse oximeters are relatively easy to use, and are common in health care facilities and at home. They are very accurate despite their low price point.
To use a pulse oximeter, simply place it on your finger. A percentage will be displayed on the screen. This percentage should be between 94 percent and 100 percent, which indicates a healthy level of hemoglobin carrying oxygen through the blood. If it is less than 90 percent, you should see a doctor.
The ABCs of Pulse Oximetry
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Spo2 94%
The Future of Telehealth in Respiratory Care
How Pulse Oximeters Measure Oxygen in the Blood
Pulse oximeters have been in use for many years. However, they were mostly used by health care facilities until recently. Now that they have become relatively common in the home, many people are wondering how they work.
Pulse oximeters function by using light sensors to record how much blood is carrying oxygen and how much blood is not. Oxygen-saturated hemoglobin appears to be a brighter red to the naked eye than non-oxygen saturated hemoglobin, and this phenomenon allows the highly sensitive sensors of the pulse oximeter to detect minute variations in the blood and translate that into a reading.
Symptoms of Hypoxemia
There are several common symptoms of hypoxemia. The number and severity of these symptoms depend on how low the SpO2 levels are. Moderate hypoxemia results in fatigue, light-headedness, numbness and tingling of the extremities and nausea. Beyond this point, hypoxemia usually becomes hypoxia.
Symptoms of Hypoxia
Spo2 94 While Sleeping
A normal SpO2 level is vital to maintaining the health of all tissue in the body. As previously mentioned, hypoxemia is low oxygen saturation in the blood. Hypoxemia is directly related to hypoxia, which is low oxygen saturation in the body’s tissue. Hypoxemia often causes hypoxia, if the oxygen levels are quite low, and remain so. Cyanosis is a good indicator of hypoxemia becoming hypoxia. However, it is not perfectly reliable. For example, someone with a darker complexion will not present with obvious cyanosis. Cyanosis also often fails to increase in visibility as the hypoxia becomes more severe. Other symptoms of hypoxia, however, do become more severe. Severe hypoxia causes twitches, disorientation, hallucinations, pallor, irregular heartbeat and eventually death. Hypoxia often has a snowball effect, in that once the process is started, it speeds up and the condition rapidly becomes more severe. A good rule of thumb is to get help as soon as your skin starts taking on a blue tinge.
Cyanosis of the tissue in the hand
Spo2 94 Fitbit
Editor's Note: This article was updated Feb. 8, 2021 to reflect new information.