A page where I summarize information regarding various medical equipment, purely for my own enjoyment.
Humidifiers are divided into the subtypes active and passive. Active means that heat and water is added from an external source, while passive ones utilize the patient.
Active humidifier: air goes into a heated reservoir, where it is loaded with water vapor. The air is then sent to the patient through the inspiratory limb of the breathing circuit, but as the temperature drops condensation occurs (as lower temperature = the air is unable to hold as much water vapor). As a result, water traps are used, which require frequent emptying to reduce the risk of contamination. These humidifiers usually also come with heated wires along the inspiratory limb, in order to reduce the problem of condensation. As exhaled air can still condense in the expiratory limb (termed "rainout"), double heated wire circuits have come into use.
Passive humidifiers: Heat and moisture exchanger (HME): mimics the function of a nose. These contain a condenser that retains moisture upon exhalation and returns it to the next inspired breath. Placement is between the Y piece and the patient. This means condensation in the tubing is not an issue, but HMEs may increase resistance to airflow. Some HMEs have the option to add a heated water source to turn them into an active humidifier and increase their capacity.