Capnograph

Oxygen is delivered to the body’s cells through the bloodstream. After being utilized by the cells, the resulting carbon dioxide (CO2) is carried away by the blood circulation. The blood transports CO2 to the pulmonary capillaries, where it is expelled into the environment during exhalation.

A capnograph (ETCO2 measurement device) is a direct monitor of inspiratory pressure and an indirect monitor of arterial blood CO2 partial pressure. It is commonly used during anesthesia, in emergency departments, intensive care units, and for critically ill patients hospitalized for extended periods. The device provides valuable information through a capnogram—a curve showing exhaled CO2 levels over time—indicating the patient’s respiratory status, ventilation pathway obstructions, or inspiratory air leaks. The capnogram also displays CO2 levels during inhalation, which is particularly useful when using mechanical ventilation systems. In healthy individuals, the difference between arterial blood CO2 partial pressure and exhaled gas is minimal, and in children, it is nearly negligible.

In cases of lung diseases or certain congenital heart conditions, the difference between arterial blood CO2 and exhaled gas increases and may exceed 1 kPa. CO2 monitoring directly measures the gas concentration using a sensor placed in the patient’s airway or indirectly by sampling air from the respiratory pathway. The most common method for measuring respiratory CO2 in capnography is infrared light absorption.

Since the end-tidal CO2 measurement device is directly connected to the patient’s airway, it can quickly detect changes in pulmonary ventilation and alert healthcare providers to any respiratory system issues. In contrast, pulse oximetry, which measures blood oxygen saturation, may take 2 to 3 minutes to reflect respiratory problems, reducing the window for timely intervention.

Types of Capnographs

Mainstream Capnograph

Equipped with a CO2 sensor connected to an airway adapter, this type measures CO2 by absorbing infrared light from the exhaled airflow. Higher CO2 levels result in greater infrared light absorption, reducing the visible light detected.

Sidestream Capnograph

This type samples gas from the airway through a small tube and processes the signal at a location similar to the mainstream sensor. The measurement is performed by the ETCO2 device.

Advantages of Sidestream Capnographs

• Easy installation and sterilization.
• Suitable for conscious patients.
• Compatible with simultaneous oxygen tubing use.

Disadvantages of Sidestream Capnographs

• Risk of sampling tube blockage.
• Delay in CO2 measurement.
• Influence of water vapor pressure changes on CO2 concentration.
• Impact of pressure drop along the sampling tube on CO2 measurement.
• Inaccurate capnogram display in children.

Advantages of Mainstream Capnographs

• No sampling tube required.
• No obstruction in the airway.
• Unaffected by pressure drops.
• Unaffected by changes in water vapor pressure.
• No delay in data recording.
• Suitable for neonates and children.

How to Purchase

For inquiries about pricing and purchasing this essential medical device, contact Anhuma’s sales team or visit the official Anhuma website for more details. The capnograph is a critical tool for enhancing patient care in various medical settings.