Capable of providing adequate levels of humidification & it has low resistance to flow and low dead space. It Provides microbiological protection to the patient & Maintenance of body temperature

Basic principle

1 Inhaling dry gases can cause damage to the cells lining the respiratory tract, impairing ciliary function

2 Within a short period of just 10 mint of ventilation with dry gases, cilia function will disrupt

3 This increases the patient’s susceptibility to respiratory tract infection

4 A decrease in body temperature occurs in the respiratory tract humidifies the dry gases

5 Air fully saturated with water vapor has an absolute humidity of about 44
mg/L at 37◦C

6 During nasal breathing at rest, inspired gases become heated to 36◦C with a relative humidity of about 80-90% by the time they reach the carina, largely because of heat transfer in the nose


7 Mouth breathing reduces this to 60-70% relative humidity

8 The humidifying property of soda-lime can achieve a humidity of 29 mg/L when used with the circle breathing system.

9 The Isotherm boundary point is where 37◦C and 100% humidity have been

10 Normally it is a few centimeters distal to the carina

11 Insertion of a tracheal or tracheostomy tube bypasses the upper airway and moves the isothermal boundary distally




Basic components

1 Two ports, designed to accept 15 and 22 mm size tubings and connections

2 The head contains a medium with hydrophobic properties in the for5 The condensed water evaporates and returns to the patient with the next inspiration of dry and cold gases, humidifying themm of a mesh with a large surface area


3 It can  make of ceramic fiber, corrugated aluminum or paper, cellulose, metalized polyurethane foam, or stainless steel fibers

4 Warmed humidified exhaled gases pass through the humidifier, causing water vapor to condense on the cooler HME medium


6 There is no addition of water over and above that previously exhaled

7 The greater the temperature difference between each side of the HME, the greater the potential for heat and moisture to transfer during exhalation and inspiration

8 The HME humidifier requires about 5-20 mint before it reaches its optimal ability to humidify dry gases

9 The performance of the HME is affecte

10 Water vapor content and temperature of the inspired and exhaled gases

11 Inspiratory and expiratory flow rates affect the time the gas is in contact with the HME medium hence the heat and moisture exchange

12 The volume and efficiency of the HME medium- the larger the medium, the greater the performance




Leave a Reply

Your email address will not be published.


Enjoy this blog