Respiratory Humidification: Basics
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Respiratory Humidification: Basics www.wilamed.com

Respiratory humidification is a method of artificial warming and humidifying of respiratory gas for mechanically ventilated patients. The term respiratory gas conditioning stands for warming and humidification as well as purification of respiratory gas. These three essential functions of respiratory gas conditioning serve the preparation of inspired respiratory gas for the sensitive lungs. If natural respiratory humidification fails, pulmonic infections and damage to lung tissue may be the consequence

In a healthy person, 75% of respiratory gas conditioning takes place in the upper respiratory tract (nasopharynx) (Figure 1). The remaining 25% are taken over by the trachea.1 The upper respiratory tract warms, humidifies and cleanses 1,000 to 21,000 liters of respiratory gas daily, depending on body size and physical capability.2 1. Warming Warming of breathing air is effected by many small blood vessels, netlike coating the nasal and oral mucous membrane (mucosa). Nerve impulses regulate the amount of blood flow like a body‘s-own heating system. Thus vessels are supplied with more blood...

During inspiration, well-vascularized mucous membranes inside the nose and mouth release moisture to the passing respiratory gas. As a result, a healthy adult person evaporates 200 to 300 ml of water per day. While inspiring through nose or mouth the mucous membranes cool down. During exhalation this cooling effect causes a portion of moisture in the air coming from the lungs (100% relative humidity at 37°C) to condensate on the mucous membranes, whereby the mucous membranes are moisturized again. On the way to the lower respiratory tract, the respiratory gas already humidified in the...

3. Cleaning While the removal of inhaled particles in the upper respiratory tract primarily takes place through coughing and sneezing (tussive clearance), in the deeper respiratory tracts mucociliary clearance is paramount. It is the most important cleaning mechanism of the bronchi. Mucociliary Clearance The main bronchi down to the alveoli are lined with a respiratory epithelium. On it, cilium is existent, bearing hair-shaped structures on its surface (cilia). The cilia are surrounded by fluid mucous layer, the periciliary liquid. This ciliary layer is covered by viscous mucus which traps...

Natural respiratory gas conditioning can be affected by mechanical ventilation using cold and dry respiratory gas. In case of non-invasive respiration (e.g. respiratory masks), a continuous positive flow is administered (e.g. CPAP). The resulting increased oral breathing causes undesirable accompanying symptoms. In the long run the upper respiratory tracts dry out caused by a permanent positive pressure supply with cool respiratory gas. The consequences are painfully inflamed nasal and oral mucous membranes as well as blockage of air passages and congestion of secretion in the respiratory...

Artificial respiration with cold and dry respiratory gas causes mucus on the respiratory epithelium to become more viscous, within a short time impairing the functionality of the cilia. The stroke frequency of the cilia slows down to final suspension (at < 30% water vapor saturation after 3–5 minutes). After no more than one hour, damages are detectable in the cell smear. The consequences may be severe:1,10 ○ ○ Impairment of the ciliary function through viscous mucus and swelling mucous membranes ○ ○ Increase in airway resistance and decrease of compliance through increasing secretion as...

Respiratory humidifier AIRcon – functional principle To prevent aforesaid complications, it is imperative to take measures to compensate loss of heat and moisture, if a patient is mechanically ventilated over a longer period of time. Then, the conditioned inspiratory air is transported to the patient. An embedded heating wire in the breathing tube keeps the temperature constant and prevents condensation. AIRcon compensates for this heat and moisture loss (fig. 3). Dry and cold inspiratory air is passed Thus, AIRcon keeps the respiratory epithelium mucous layer supple and cilia flexible....

Advantages of the respiratory humidifier AIRcon over HMEs ○ ○ Providing the physiological temperature of ○ ○ Applicable also for neonates of less 37°C with the optimum of 100% relative humidity ○ ○ Maintaining of mucociliary clearance over long periods of time ○ ○ Secretion liquefaction reduces the risk of tube or cannula occlusion ○ ○ No increase of dead space or breathing resistance than 2500 g ○ ○ No sustainable moisture losses during extraction ○ ○ Operation with heated and unheated breathing tube systems possible ○ ○ Intelligent alarm management ○ ○ Individual a

Active humidification – accessories Humidifier chamber ○ ○Practical autofill system: An integrated floater ensures the correct water fill level. ○ ○ Constant volume: A regulated autofill mechanism ensures a constant volume in the humidifier chamber. ○ ○ Economical: Our range of products includes disposable humidifier chambers (usable for up to 7 days), and reusable humidifier chambers (autoclavable at 134°C). Mountings ○ ○ Universal application: Our mountings are applicable with conventional and common standard rails. ○ ○ Stable support: The mountings are specifically designed for the...

References 1 W. Oczenski, H. Andel und A. Werba: Atmen - Atemhilfen. Thieme, Stuttgart 2003: 274, ISBN 3-13-137696-1. 2 A. Wanner, M. Salathé, T.G. O‘riordan: Mucociliary Clearance in the Airways. In: American journal of respiratory and critical care medicine, 1996, 154 (1), no6: 1868-1902, ISSN 1535-4970. 3 N. Cauna, K.H. Hinderer: Fine structure of blood vessels of the human nasal respiratory mucosa. In: Ann Otol Rhinol Laryngol, 1969; 78(4):865-79, ISSN 0003-4894. 4 J. Rathgeber, K. Züchner, H. Burchardi: Conditioning of Air in Mechanically Ventilated Patients. In: Vincent JL. Yearbook...

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