When Natural Balance is Compromised

When an infant needs respiratory support, the natural balance of the airway can be compromised. Respiratory interventions without humidity impede development and exacerbate the associated risks as described below:

1. A threat to energy reserves 
Developing infants need energy for growth and development. The depletion of heat and moisture can negatively impact energy reserves. Read more about the threat to energy reserves.

2. An immature mucociliary transport system 
This is inherently compromised in an infant. The cilia are often too short and uncoordinated to effectively reach into the mucus layer. If low humidity gas is used with respiratory support, mucociliary clearance can be severely compromised.


3. Medical gases 
These are extremely cold and dry. Their use in respiratory medicine often means low humidity gases are delivered to infants. The influence of this can be significant. The table opposite highlights various forms of humidified gas that can be delivered to infants in hospital.

4. A bypassed airway 
Endotracheal or tracheostomy tubes bypass the upper airway where the majority of heat and moisture is normally added during inspiration. In this process, the filtering mechanisms of the upper airway are also bypassed.

5. Inspiratory flows
Even though medical gas flow rates may be classed as “low”, they may still make up a significant proportion of (or exceed) the infant’s minute volume. In effect, excessive heat and moisture are drawn away from the airway mucosa.

A Threat to Energy Reserves

Developing infants need energy for growth and development. The depletion of heat and moisture from the airway can negatively impact these limited energy reserves through:

Increased Risk of Infection

Low humidity gases increase the risk of infection by placing strain on the mucociliary transport system, reducing its efficiency and the explusion of inspection-causing contaminants.

Reduced Respiratory Mechanics

Work of breathing can significantly increase when the airway lumen is reduced through intubation, secretion build-up, bronchoconstriction and poor lung compliance.

Evaporative Losses

When inadequate levels of humidity are inhaled, water vapor is drawn from the airway mucosa until the inspired gas has reached 37 ºC, 44 mg/L. The energy cost to the infant for each gram of water removed from the mucosa is 0.58 kCal (2.4 KJ).1

Absolute humidity during various respiratory interventions graph



The graph opposite highlights the levels of humidity able to be delivered during various respiratory interventions, against what is physiologically normal (37 ºC, 44mg/L) for the lungs.

The deficit must be made up by the infant's airway requiring significant consumption of precious energy reserves.