What is Capnography and what is it used for in patient monitoring?

What is Capnography?

Oxygen enters your body’s bloodstream via the lungs and then travels throughout the body to aid in metabolism.  Your body’s metabolism breaks down the food you eat in order to produce energy, and as a byproduct of this process your body excretes a gaseous waste product called carbon dioxide (Co2) into your blood. This then travels back to your lungs and exits your body through exhaled breath.  Capnography refers to the use of a capnograph to measure the levels of excreted carbon dioxide, or CO2, into the bloodstream.  A capnograph is most commonly used for patients undergoing anesthesia to ensure that the patient receives enough oxygen throughout the procedure; however, they are also used often in Emergency Medicine when a patient receives an endotracheal tube, also known as a breathing tube, to ensure proper placement of the tube.

Capnography measures exhaled breath by plotting the partial pressure of CO2 in wavelength form on an x and y axis grid.  The capnograph displays wavelengths as well as numbered measurements - a normal reading falls between 30 and 40. The capnograph is the patient’s direct line of communication to his or her doctor when they are unable to speak for themselves. If a patient’s number falls below 30 it is a strong indication that the patient isn’t receiving enough oxygen due to a problem with the endotracheal tube or a general medical complication.

Recently, hospitals and other healthcare facilities have also begun to rely upon a capnograph to help patients suffering from asthma and COPD.  To determine the severity of the patient’s illness a doctor uses a capnograph to gauge how well his or her lungs are functioning.  As respiratory science advances, more and more uses for the capnograph are being discovered every day.