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There are no contraindications to humidification, though the device chosen will depend upon type of oxygen therapy, tenacity of secretions, and the patient’s clinical condition (i.e. mechanical ventilation, self-ventilating at home, etc.).

Humidification should not be used for patients requiring open system (mask) ventilation when ‘droplet contact’ isolation precautions are required.

Anticipated patient outcomes

The provision of adequate humidification of gases enabling clearance of secretions, a reduction in the tenacity of secretions, and improved gas exchange. The patient’s airway is to remain patent at all times.

Preprocedural considerations

Equipment

Heat and moisture exchanger (HME)

During ventilatory humidification an HME performs the function of the nose and pharynx in conditioning the inspired air. It retains heat and moisture in the expired air and returns them to the patient in the next inspired breath. Many HMEs contain a bacterial filter. The HME consists of spun, pleated, highly thermal conductive material. It is also known as an artificial or ‘Swedish’ nose (Figure 10.8). It can be used in a self-ventilating patient with a tracheostomy who is being weaned from oxygen (Figure 10.9). It can also be used in ventilated patients, inserted between the patient’s airway and the ventilator circuit.

Figure 10.8 Swedish nose.

Figure 10.9 Heat and moisture exchanger.

Cold water bubble humidifier

This device delivers partially humidified oxygen at about 50% relative humidity. Gas is either forced across or bubbled through water at room temperature (Figure 10.10). This method is not advised as it is inefficient (Bersten et al. 2009).

Figure 10.10 Cold water bubble humidifier.

Water bath humidifiers

With these devices, inspired gas is forced over or through a heated reservoir of water (Figure 10.7D). To achieve an adequate humidity for the patient, the water bath must reach a set temperature. The gas will then cool as it moves down the breathing circuit to the patient, and a relative humidity of 100% will be reached. Hot water bath humidifiers are therefore very efficient and useful for humidification for immobile patients, particularly if they are receiving mechanical ventilatory support. However, they have four main disadvantages.

Danger of overheating and causing damage to the trachea.

Their efficiency can alter with changes in gas flow rate, surface area and the water temperature.

Condensation and collection of water in the oxygen delivery tubes.

The possibility of microcontamination of stagnant water (Tinker and Zapol 1992).

Aerosol generators

These devices are not governed by temperature, but provide microdroplets of water suspended in the gas (Bersten et al. 2009). The gas provided through aerosol devices can be very highly saturated with water. There are three main types of aerosol humidifier.

Gas-drive nebulizer

Mechanical (spinning disc) nebulizer

Ultrasonic nebulizer

These devices are useful for the spontaneously breathing patient with chronic chest disease.

Procedure guideline 10.2 Humidification for respiratory therapy

Various humidifiers exist. Select the system most appropriate for the patient.

Essential equipment

Bath humidifier

Heating equipment

Oxygen (elephant) tubing (Figure 10.7C)

Oxygen analyser (Figure 10.7A)

Sterile H2O bottle or bag depending on type of humidifier used

Preprocedure

Action Rationale

1 Discuss with patient’s doctor the choice of system to be used. To ensure the most appropriate device is selected to meet the patient’s needs. E

2 Explain to patient the reason for use of the humidifier and how it works. To enable the patient to understand what is happening and to able to tolerate the humidification. E

Procedure

3 Prepare the device to be used (although some circuits are ready prepared with humidifier).

(a) Prepare humidifier and circuit.

(b) Attach humidifier/wide-bore oxygen tubing: ensure minimal length of tubing, water trap and mask.

To ensure the circuit is in working condition and patent to oxygen flow. E

Connecting