Chapter 12: Respiratory care, CPR and blood transfusion
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Evidence‐based approaches
Many devices can be used to supply humidification. The best of these will fulfil the following requirements (Al Ashry and Modrykamien [7], McNulty and Eyre [154]):
- The inspired gas must be delivered to the trachea at a temperature of 32–37°C with 100% humidity and should have a water content of 33–44 g/m3.
- The appliance should not increase resistance or affect the compliance of respiration.
- Electrical humidifiers should have a safety alarm system to guard against overheating and overhydration. The set temperature should also remain constant; temperature and humidification should not be affected by large ranges in flow.
Rationale
The provision of humidification and heat in high‐flow oxygen therapy (>5 L/min) can minimize symptoms of dryness and improve patient tolerance. Although there is no evidence to support the use of humidification in patients receiving low‐flow oxygen therapy or those receiving it in the short term, it should always be considered for patients where the natural pathway of humidification is bypassed (those with an altered airway such as a tracheostomy, laryngectomy or endotracheal tube) (McNulty and Eyre [154]). Adequately heated and humidified oxygen therapy reduces the tenacity of secretions, improves the clearance of secretions, and reduces atelectasis, thus improving lung ventilation and gas exchange (McNulty and Eyre [154], Nishimura [197]).
Indications
Humidification is indicated for:
- patients who are intubated and mechanically ventilated
- patients who have an altered airway
- patients with COPD to aid expectoration of viscous secretions
- patients who report upper airway discomfort due to dryness.
Contraindications
Humidification should not be used for patients requiring open system (mask) ventilation when their infective status determines that ‘droplet contact’ isolation precautions are required.
Anticipated patient outcomes
Secretions will be cleared and the patient's lung function and gas exchange will be improved through the provision of humidified gases.
