Background

A non-invasive medical device called pulse oximetry is used to evaluate a person’s blood’s oxygen saturation. It provides a valuable indicator of how well oxygen is being transported to the body’s extremities, including the fingers and toes. The device used for pulse oximetry is called a pulse oximeter.

Principle of Operation:

• Pulse oximeters work on the principle that oxygenated and deoxygenated hemoglobin (the proteins in red blood cells responsible for carrying oxygen) absorb light differently.
• The device typically emits two wavelengths of light, usually red and infrared, through a translucent part of the body, often a fingertip.
• The blood’s oxygen saturation is then determined by measuring how much light is absorbed by oxygenated and deoxygenated haemoglobin.

Development and History:

• The development of pulse oximetry dates back to the early 1970s. The first commercial pulse oximeter was introduced in 1981.

The technology has since evolved, becoming more compact, accurate, and affordable. It is now widely used in various healthcare settings, including hospitals, clinics, and even for home monitoring.

Indications

• Endotracheal Intubation: During the placement of a breathing tube (endotracheal intubation), pulse oximetry is often used to continuously monitor oxygen saturation levels to ensure proper ventilation and oxygenation.
• Cardiac Arrest: Pulse oximetry may be used during cardiac arrest resuscitation efforts to monitor oxygen saturation and guide interventions to optimize oxygen delivery.
• Procedural Sedation: When patients undergo procedures that involve sedation, pulse oximetry helps monitor their oxygen levels, ensuring safety during the sedation process.
• Asthma/Chronic Obstructive Pulmonary Disease (COPD): Individuals with asthma or COPD may experience fluctuations in oxygen saturation levels. Pulse oximetry is employed to monitor these patients during exacerbations or routine care.
• Respiratory Complaints: For patients presenting with respiratory complaints, pulse oximetry aids in the rapid assessment of oxygenation status, guiding healthcare providers in determining appropriate interventions.
• Acute Respiratory Distress Syndrome (ARDS): It is a severe lung condition characterized by low oxygen levels in the blood. Pulse oximetry plays a crucial role in monitoring ARDS patients to guide ventilator management and support.
• Sleep Disorders/Sleep Apnea: In sleep studies and assessments for sleep disorders, pulse oximetry is often used to monitor oxygen saturation levels during different sleep stages, especially in conditions like sleep apnea.
• Shunts in Cyanotic Heart Diseases: In patients with congenital heart diseases causing shunting of blood, pulse oximetry helps assess the degree of oxygenation by monitoring the oxygen saturation in different parts of the circulatory system.

Contraindications

• Motion Artifacts: Excessive movement or motion can interfere with the accuracy of pulse oximetry readings. Patients who are agitated, restless, or involved in significant physical activity may produce unreliable results.
• Poor Peripheral Perfusion: Severe hypotension and shock are two conditions that lead to poor peripheral perfusion and may affect pulse oximetry values. In these cases, central venous oxygen saturation (ScvO2) monitoring or arterial blood gas analysis may be more appropriate.

Nail Polish and Artificial Nails: Nail polish, especially dark-colored varieties, and artificial nails can absorb light and interfere with the transmission of light through the finger, potentially leading to inaccurate readings.

Outcomes

• Oxygen Saturation (SpO2) Measurement: The measurement of arterial blood oxygen saturation (SpO2) is the main result of pulse oximetry. This percentage value indicates the proportion of hemoglobin in the blood that is carrying oxygen. Normal oxygen saturation levels typically range from 95% to 100%.
• Early Detection of Hypoxemia: Pulse oximetry is crucial for the early detection of hypoxemia. Detecting hypoxemia promptly allows healthcare providers to intervene and optimize oxygen delivery to vital organs and tissues.
• Monitoring Respiratory Status: Continuous monitoring of oxygen saturation is particularly important in patients with respiratory conditions such as asthma, chronic obstructive pulmonary disease, or acute respiratory distress syndrome (ARDS). Changes in oxygen saturation levels can indicate worsening respiratory function.
• Assessment During Procedures and Anesthesia: During medical procedures, surgeries, and anesthesia, pulse oximetry helps healthcare providers ensure that patients are adequately oxygenated. Sudden drops in oxygen saturation can be indicative of airway issues, respiratory compromise, or other complications

Equipment Setup

Pulse Oximeter:

• Choose a reliable pulse oximeter with appropriate sensors for the patient population (e.g., pediatric or adult).
• Ensure that the pulse oximeter is functioning correctly and the batteries are charged or replaced as needed.

Sensor Placement:

• Select an appropriate site for sensor placement. The most common locations are the fingertip, earlobe, or toe.
• Ensure that the sensor site is clean, dry, and free from excessive hair or jewelry that might interfere with proper contact.

Secure Sensor:

• Properly secure the pulse oximeter sensor to the chosen site. Ensure that it is snug but not too tight, allowing for proper blood flow to the area.

Calibration:

• Some pulse oximeters may require calibration or verification of accuracy before use. Follow the manufacturer’s guidelines for calibration if necessary.

Patient Positioning

• Comfortable Position: Ensure the patient is in a comfortable position for the procedure. This might include lying on a procedure table, sitting in a chair, or assuming a specific position, depending on the nature of the procedure.
• Accessibility of Monitoring Site: Choose a monitoring site that is easily accessible and does not interfere with the procedure. For example, if the procedure involves the upper extremities, placing the pulse oximeter on a finger may be appropriate.
• Secure Wiring: Make sure that the patient’s pulse oximeter wire is securely fastened without being too tight to the point of discomfort or impeding mobility.
• Consider Special Populations: For pediatric patients or patients with specific conditions, choose the appropriate sensor size and location based on the patient’s age, size, and medical condition.
• Patient Education: Communicate with the patient about the purpose of the pulse oximeter, emphasizing that it is a non-invasive and painless monitoring tool. Address the patient’s concerns and queries.

During the Procedure:

• Continuous Monitoring: Activate continuous monitoring and ensure that the pulse oximeter is displaying real-time oxygen saturation readings.
• Prompt Action for Changes: Be attentive to any significant changes in oxygen saturation levels and respond promptly. Address potential issues such as changes in patient positioning or sensor dislodgment.
• Documentation: Document baseline oxygen saturation levels before the procedure and monitor trends throughout. Document any interventions taken in response to changes in oxygen saturation.
• Integrate with Anesthesia Monitoring (if applicable): If the procedure involves anesthesia, integrate pulse oximetry monitoring with other anesthesia monitoring devices for a comprehensive assessment of the patient’s vital signs.

TECHNIQUE

Digit Approach:

• The recommended technique involves the placement of a transmission probe at the end of a digit, typically the finger, where the emitter is positioned on one side and the sensor on the opposite side. To ensure accurate readings:
• The digit should be positioned in a comfortable and shaded manner to prevent excessive light interference.
• Prior to probe attachment, it is crucial to eliminate any excessive debris, nail polish, or artificial nails that might impede proper contact.
• Connect the probe securely to the monitoring unit to initiate the pulse oximetry process.

Ear Approach:

• A transmission probe is applied to the end of an earlobe, with the emitter and sensor on opposite sides.
• Subsequently, connect the probe to the monitoring unit to initiate the pulse oximetry measurements.

Palm/Foot Approach in Neonates:

• In cases where neonates pose challenges for digit or ear placement:
• Apply a transmission probe over the palm or foot, considering their size.
• Connect the probe to the monitoring unit to commence pulse oximetry for neonatal patients.

Forehead Approach:

For readings from the forehead:

• Place a reflectance probe just above the eyebrows on the forehead, ensuring it is positioned away from significant vessels.
• The patient should be comfortably inclined during the process.
• Secure the probe with a headband placed across the forehead.
• Connect the probe to the monitoring unit for continuous pulse oximetry monitoring.

Complications

• Motion Artifacts: Excessive patient movement or motion can lead to inaccuracies in pulse oximetry readings. This is especially relevant in situations where patients are agitated, restless, or involved in physical activities.
• Poor Peripheral Perfusion: Conditions that result in poor peripheral perfusion, such as hypotension or shock, may affect the accuracy of pulse oximetry readings. In such cases, central venous oxygen saturation (ScvO2) monitoring or arterial blood gas analysis may be more reliable.
• False Readings in Certain Conditions: Certain medical conditions, such as anemia, carbon monoxide poisoning, or methemoglobinemia, can potentially result in inaccurate pulse oximetry readings. These conditions affect the oxygen-carrying capacity of hemoglobin.
• Nail Polish and Artificial Nails: Dark-colored nail polish or artificial nails can absorb light and interfere with the transmission of light through the finger, potentially leading to inaccurate readings.
• Skin Conditions: Skin conditions affecting the area where the pulse oximeter is applied, such as burns, tattoos, or scars, may interfere with proper sensor contact and accurate readings.
• Inaccuracies in Presence of Intravenous Dyes: Certain intravenous dyes used in medical procedures, such as indocyanine green or methylene blue, may interfere with the accuracy of pulse oximetry readings.
• Delay in Detecting Rapid Changes: Pulse oximetry may not detect rapid changes in oxygen saturation, and there may be a delay in reflecting sudden drops in oxygen levels.

False Readings during Movement: Patient movement during the application of pulse oximetry, especially in critical care or during procedures, can result in false readings. This can lead to unnecessary interventions or delays in addressing actual changes in oxygenation.

Medication Summary

Medications are not directly used in the process of pulse oximetry. It is a non-invasive method used to measure the oxygen saturation of hemoglobin in arterial blood, and it does not involve the administration of medications.

Instead, pulse oximetry relies on the interaction of light with oxygenated and deoxygenated hemoglobin to estimate the percentage of oxygen saturation in the blood.

References

Pulse Oximetry:ncbi. nlm. nih

Medication

References

Pulse Oximetry:ncbi. nlm. nih