Respiration defined as the movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction.
Tests of respiratory functions carried out for various reasons, including the
Assessment of lung disease,
Monitoring the condition of patients under anesthesia or under intensive care, and
Investigation of normal lung physiology.
The body, in particular, the brain, requires a constant supply of blood with dissolved oxygen and carbon dioxide of around 100 and 40 mmHg respectively. For maximum efficiency. perfect matching of air and blood flow required in each of the lungs alveolar compartments, with an overall ventilation rate of 18-20 breaths per minute.
Normal Respiratory Rate
12-20 Breaths per minute
Several ways to measure respiration. Measured either through capnography or ECG. Capnography nor respiration measured from ECG. Priority to capnography when the patient under inductional agents then respiration
When measured from ECG, respiration measurement is based on impedance pneumography. The method passing a low current, high-frequency carrier signal between two ECG electrodes on either side of the chest wall.
The impedance or resistance of the chest changes as the lungs expand and contract and as the volume of air in the lung changes. The change in impedance creates a change in voltage across the carrier signal which interpreted as a breath and displayed as an analog waveform.
The rate displayed as a digital value on the Monitor.
The ECG electrodes placed as shown in the diagram below. However, in order to improve the measurement.
Apnea Detection
Apnea is the cessation of breathing in infants and adults who are at risk of respiratory failure. sensitive APNEA detection circuit which detects such an event and triggers an alarm if a user-defined time limit is exceeded.
Respiration monitored through the same ECG cables (3/5 lead) or through Capnography.
Priority of method
Respiration from C02 (sidestream) of AGM
Respiration from Capnography (Mainstream)
Measurement of Respiration from ECG.
