humidification and their use in anesthesia field

Brief description of how humidification works and takesplace in the anesthesia field

1. HUMIDIFICATION

2. HUMIDITY A general term used to describe the amount of water vapour in gas. ABSOLUTE HUMIDITY The mass of water vapour in a volume of gas. IMPORTANCE OF HUMIDIFICATION Normal breathing: U pper respiratory tract warms, humidifies, and filters inspired gases, primarily in the nasopharynx Even at extremes of inspired temperature and humidity, the gas that reaches the alveoli is 100% saturated at body temperature. Normally, the respiratory tract loses approx, 1470J heat and 250ml water per day. ISOTHERMIC SATURATION BOUNDARY is the point at which gases reach alveolar conditions ie ; normal body temperature and 100% relative humidity.

3. Damage to respiratory tract Body heat loss Absorbent desiccation Tracheal tube obstruction EFFECTS OF EXCESSIVE HUMIDITY Pulmonary oedema Altered alveolar arterial O2 gradient Decreased hematocrit and serum sodium EFFECTS OF INHALING DRY GASES

4. CO2 absorbent- reaction of CO2 with absorbent releases water - absorbent granules also contains water Moistening/Rinsing breathing tubes and reservoir bag before use Low fresh gas flows -conserve moisture Coaxial breathing circuits –increase humidity more quickly than separate limbs along with low flows. But not very efficient in mapleson D as it requires high fresh gas flow. OTHER MAIN SOURCES HEAT AND MOISTURE EXCHANGERS- hydrophobic, hygroscopic HUMIDIFIERS- heated and unheated NEBULISERS SOURCES OF HUMIDITY

5. HME(Heat Moisture exchanger) When combined with filter for bacteria and viruses, it is known as heat moisture exchange filter. Disposable devices Vary in size and shape Each has a female connection port at patient end and male connection port at other end.