Monitoring Devices

• 21% oxygen
• 71% nitrogen
• 1% carbon dioxide and other gases

lungs and tissues - in capillary beds

exhaled CO2 concentration and is an accurate indicator of arterial circulation and CO2 concentration

• the animal needs CO2 to maintain an acid base balance 
• if the animal breathed all the CO2 out then it would become alkalotic

• metabolism
• pulmonary perfusion
• alveolar ventilation
• technical error

• hypotension
• hypothyroidism
• muscle relaxants

• fever
• malignant hyperthermia
• sodium bicarbonate
• tourniquet release
• seizures

• decreased cardiac output
• hypotension
• hypovolemia
• pulmonary embolism
• cardiac arrest

• increased cardiac output
• increased blood pressure

• hyperventilation
• apnea
• partial airway obstruction
• asthma
• pulmonary edema

• hypoventilation
• rebreathing

• disconnection
• sampling leaks
• sampling fresh gas flow
• obstructed endotracheal tube

• exhausted CO2 absorber
• inadequate fresh gas flow
• leaks in the breathing circuit
• faulty valves

depleats CO2 and causes body to stop breathing so CO2 will build back up to stimulate breathing again

alveolar ventilation (hypoventilation and rebreathing) and technical error (exhausted CO2 absorber, inadequate fresh gas flow, leaks in the breathing circuit, faulty valves)

• first look at INCO2
• if INCO2 is normal then the cause is hypoventilation
• if INCO2 is increased then the cause is a technical error

• if it is low then there could be a low cardiac output, hypotension, hypovolemia, embolism (rules these out first)
• then look for hyperventilation or technical error (these are the most common)
• if it is ZERO then look for apnea, obstruction in the endotracheal tube, or a disconnection in the machine