Introduction
Technology integration has revolutionized medicine and surgical techniques. This has enabled us to perform diagnostic and therapeutic assessments non-invasively. Hemoglobin (Hb) monitoring is a common diagnostic procedure performed worldwide. The hemoglobin test is helpful in -
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Diagnosing anemia.
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Requiring blood transfusion.
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Bleeding during surgery.
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Other conditions.
Non-invasive hemoglobin monitoring technique has recently gained traction but has yet to be explored by emergency health service providers. The article explores the benefits, disadvantages, and clinical application of non-invasive hemoglobin monitoring.
What Is Hemoglobin?
Hemoglobin is the essential part of red blood cells. The protein is responsible for transporting oxygen-rich blood from the lungs to body tissues. Hemoglobin is formed from four protein molecules known as globulin chains. Each globulin chain contains heme with iron embedded in it. If the hemoglobin level reduces below the normal range, it is known as anemia, cancer, or other medical disorders. Therefore, if an individual has anemia, an adequate amount of oxygen does not reach the body's tissue leading to fatigue. The normal hemoglobin range for men is between 14 to 17 g/dL (gram per deciliter). In women, the average hemoglobin range is between 12.3 to 15.3 g/dL.
Why Is Hemoglobin Monitoring Necessary?
Hemoglobin monitoring is an essential test for individuals with trauma. The decision to treat trauma patients with blood transfusion or operative intervention can be made through test results. Most patients are treated nonoperatively, whereas some require surgical intervention for ongoing bleeding or hemodynamic instability. Therefore, surgical intervention patients require close monitoring and repeated hemoglobin assessment to look for bleeding.
There is also a risk of postoperative anemia that significantly increases the morbidity and mortality of patients which can be avoided by continuous Hb monitoring. Accurately monitoring the hemoglobin levels can avoid the risk of over and under-transfusion.
How Is Hemoglobin Measured?
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Invasive Measurement
Hemoglobin monitoring through invasive measures is time-consuming, expensive, painful to patients, and may increase the risk for biohazard exposure. In addition, patient care is delayed due to the time-consuming efforts for phlebotomy (blood collection from a vein), sample transport to the laboratory; time taken for testing and validation, and reporting of results.
The most commonly used invasive testing for hemoglobin is complete blood count (CBC). It can be performed manually or automatically with machines. However, the test does not provide real-time data.
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Non-invasive Hemoglobin Monitors
In recent years, pulse CO-oximeters (carbon monoxide) was modified to non-invasively measure hemoglobin concentrations through multi-wavelength sensors for spot checks or frequent hemoglobin monitoring. At first, the non-invasive technique was introduced for surgery monitoring, but in recent years, it has been used for spot checks for blood donor qualification. The device emits light in multiple wavelengths and measures hemoglobin concentration depending on light adsorption in blood. The device contains a fingertip sensor that measures hemoglobin non-invasively.
What Are the Types of Non-invasive Hemoglobin Monitors?
Non-invasive hemoglobin monitors are of two types:
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Continuous Hemoglobin Monitor: The serum hemoglobin levels can be monitored continuously and provide real-time data on hemoglobin levels in the body.
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Spot Check Hemoglobin Monitor: A point-of-care device monitors hemoglobin within one minute of placing the fingertip probe on the patient's finger.
The accuracy and reliability of the monitor can vary.
How Does Non-invasive Hemoglobin Monitor Function?
Most commercially available non-invasive devices have differences in their basic principle. However, most of the devices rely on two principles of spectrophotometry and photoplethysmography.
In devices operating with spectrophotometry, light is transmitted through or reflected from blood and tissue depending on their biochemical variables. The differences in reflection magnitude help estimate hemoglobin and hematocrit values using mathematical models. Occlusion spectroscopy contains a ring-shaped sensor attached to the subject's finger. The sensor temporarily halts blood flow forming an electrical signal that yields a high signal-to-noise ratio.
Devices functioning with the principle of photoplethysmography detect the magnitude of the plethysmography signal at different cardiac cycle intervals using different light wavelengths. Separate photo-detectors detect the signals to estimate the value of hemoglobin and hematocrit.
What Are the Benefits of Non-invasive Hemoglobin Measurement?
Non-invasive hemoglobin monitors reduce pain, scarring, and discomfort in patients while hemoglobin monitoring. The risk of being subjected to potential biohazards is diminished. The hemoglobin levels are monitored continuously, and the data is obtained in real-time. The Hb test results can be received within 30 seconds. There is a reduced need for personnel for hemoglobin monitoring, and it can be carried out quickly and safely. There is no risk associated with the handling of blood and needles for laboratory personnel. The non-invasive method of hemoglobin monitoring is accurate, up to 1 g/dL. The non-invasive monitoring device is portable in size.
What Are the Drawbacks of Non-invasive Hemoglobin Measurement?
Non-invasive hemoglobin devices are dependent on adequate blood perfusion to extremities. Any changes in blood perfusion to extremities can change the measured values and accuracy. Therefore, in patients with shock or taking vasopressors, blood perfusion to the periphery is compromised. Hence, the reading must be taken with caution.
The patients must remain still while measuring the hemoglobin levels through a non-invasive technique. If the patients do not stay still, then repeated measurements are needed. Hence, the device's application is limited to intoxicated or agitated patients. Accurate measurement of hemoglobin levels may be hindered if the fingers are contaminated with tar, soot, or nail polish.
What Is the Recent Advancement in Non-invasive Hemoglobin Monitoring?
Recently, mobile-based apps have been developed for non-invasive and instant monitoring of hemoglobin levels. The hemoglobin levels are measured using the individual's phone camera flash toward the finger. The color of blood visible under lights is analyzed for hemoglobin estimation using a software app developed for phones. Additionally, light from incandescent or LED (light emitting diode) bulbs may be used for assessment. The hemoglobin measurements through smartphones had almost 65 percent correlation with invasive methods. The mobile app cannot replace invasive blood tests like complete blood count (CBC). However, the mobile app can be a practical alternative screening test that can be useful to determine the need for further investigations.
Conclusion
Non-invasive hemoglobin monitoring can efficiently measure hemoglobin levels in emergencies. The values provided are accurate and reliable in most patients enabling quick treatment. The technique is also painless, comfortable, and with minimal risk to handling personnel. Recent advancements in mobile-based techniques have enabled easy accessibility and screening of hemoglobin levels.
