What is capnography?
Capnography is the measurement and recording of the concentration or partial pressure of carbon dioxide (CO2). It is usually measured by a sensor placed in the nose of the examinee (exhaled CO2) or on his finger (transcutaneous CO2).
The pressure of CO2 that is obtained by this method gives an indirect estimate of the pressure of CO2 in arterial blood. These two pressures in normal individuals are almost equal. Though, there are various diseases that increase the difference between them.
A high value of exhaled CO2 means that there is hypoventilation and difficulty in breathing. In contrast, low exhaled CO2 demonstrates hyperventilation which means that the examinee breathes more than normal.
Because capnography provides measurement of CO2 breath per breath, it is a very useful diagnostic tool in the hands of the physician, and may reveal too early a disruption of the respiratory function of the patient. Thus, it is used for the evaluation of asthma, heart failure, diabetes, pulmonary embolism and in all those cases where quick and easy assessment of the patient’s ventilation is needed.