Capnography (End tidal Carbon dioxide)

Definition:
It is the monitoring of the conc. or PaCO2 in the respiratory gases, its a main tool to measure CO2 during Anesthesia ans Intensive care.
It is recorded in form of graph that plot;  expiration against time.

Main Uses:
The Capnogram directly use for the monitoring of inhaled and exhaled Conc. or partial pressure of CO2.
The Capnogram indirectly use for the monitoring of the CO2 Partial pressure of Arterial blood.

* In a healthy individual there is very small difference between arterial blood and exhaled gas CO2 partial pressure.
* In presence of lung disease and congenital heart diseases, there is more than 1 kPa is difference between arterial blood and exhaled gas CO2 partial pressure

Diagnostic Uses:
It provides the information about Carbon-dioxide production i.e;

• Pulmonary perfusion.
• Alveolar ventilation.
• Respiratory pattern.
• Elimination of CO2 from anesthesia breathing circut and ventilators.

The graph can be effected by some lung disease, i.e;

Bronchitis,

Emphysema,

Asthma.

The graph cannot be affected by pulmonary embolism and some heart disease, i.e;

There is no change in graph relation, but actual they effects the relation between exhaled carbon-dioxide partial pressure and arterial blood.

* Increase production of CO2 is seen in Fever and in shivering.

* Decrease production of CO2 is seen in Anesthesia and hypothermia.