Humidification Introduction


Flexicare’s comprehensive portfolio of breathing systems supports the range of invasive and non-invasive, passive and active humidification ventilation therapies to enhance patient care and improve clinical outcomes.

Humidification Principles

The upper airway plays a key role in filtering, warming and adding moisture to inspired gases as they travel into the lungs.

When the upper airway is bypassed during invasive ventilation, delivery of cold and dry gases desiccate and cool the lining of the airway, leading to dysfunction of the Mucociliary Transport System. Dysfunction has been associated with retention of tracheobronchial secretions1, loss of airway patency, mucous plugging, atelectasis, infection2 and Ventilator-Associated Pneumonia (VAP)3.

Although gas conditioning by the upper airway is retained during non-invasive respiratory support, the high pressure and flow rate of dry and cold medical gases may overwhelm the upper airway, cause discomfort and reduce patient compliance with the therapy.

Artificial warming and humidification of inspired respiratory gases to close to physiological levels maintains the position of the Isothermic Saturation Point and reduces the adverse effects of low temperature and humidity on lung function and the Mucociliary Transport System during prolonged use.

Humidification in Anaesthesia

With the focus on optimising patient outcomes, humidified breathing circuits are being used for patients undergoing general anaesthesia. Studies have shown that heated humidified breathing systems are more effective in maintaining mucociliary clearance during 3 hours of general anaesthesia than the use of conventional anaesthetic circuits4.

In addition, active humidification delivers gas at 37°C directly to the patient’s lungs, helping maintain core body temperature and reducing the incidence and duration of hypothermia during surgery.

Invasive Ventilation

When the upper respiratory tract is bypassed by an endotracheal or tracheostomy tube, normal warming and humidification of inspired gases cannot take place. Dysfunction of the Mucociliary Transport System can occur if gases reaching the lowest respiratory tract are insufficiently warmed and humidified.

For long term intubated patients, active humidification is recommended to deliver gases close to the Optimal Temperature and Humidity.

Optimal 37°C, 44 mgH2O/L

Humidity 100% Relative Humidity

Non-Invasive Ventilation (NIV)

For non-intubated patients, respiratory support can be delivered by High Flow Oxygen Therapy (HFOT) via a High Flow Nasal Cannula or other Non-Invasive Ventilation (NIV) therapies such as Continuous Positive Airway Pressure (CPAP) or Bi-Level Positive Airway Pressure (Bi-PAP).

Delivering a high gas flow during the inspiratory phase improves alveoli recruitment and gas exchange in the lungs. However, the cold and dry medical gases at a high flow rate may overwhelm the Mucociliary Transport System. Therefore, active humidification is recommended to deliver Essential Humidity during HFOT or NIV therapy to support the patient’s upper airway function to deliver Optimal Humidity to the lungs, and to improve patient comfort and compliance.

Essential 31°C, 32 mgH2O/L

Humidity 100% Relative Humidity

1 Irwin, R.S & Rippe, J. M (2008), Irwin and Rippe’s Intensive Care Medicine (Sixth Edition), Philadelphia, PA: Lippincott Williams & Wilkins.
2 Lemin, M, New Developments in Mechanical Ventilation and Humidification, AARC Times, March 2009, Vol. 33 Issue 3, P32.
3 Lorente L, Lecuona M, Jiménez A, Mora ML, Sierra A, Ventilator-Associated Pneumonia Using A Heated Humidifier Or A Heat And Moisture Exchanger: A Randomized Controlled Trial, Crit Care, 2006, 10(4), R116.
4 Effect of Heated Humidified Ventilation on Bronchial Mucus Transport Velocity in General Anaesthesia: A Randovmized Trial by Seo HS, Kim SH, Hong JY, and Hwang JH, Dept. of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.