Significance and technical background of humidified mixture of gases in the delivery room

• Pressure 
• Temperature
• State variables, state equations of gas, change of state of gases

p . V = n . R . T 

R = 8, 314 J . mol-1. K-1 

Any gas is a vapour in its liquid state. We call those vapours that are far enough away from their liquid phase a gas.

„Water vapour“ in not fog. Fog is a mixture of dry air, water vapour and water aerosol.

 Misting, fogger, nebulizer

Nebulizer

• Nebulizers generate aerosols consisting of droplets of various sizes, which are mixed with inhaled breathing gas. 
• Small volume nebulizers
• Ultrasound nebulizers

  

The high-density mist produced by nebulizers is useful in reducing the viscosity of respiratory secretions in people suffering from, for example, cystic fibrosis, epiglottitis and bronchiectasis.


Calculations with moist air

Dalton's law the statement that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual component gases.


Possibility of defining so-called partial pressures p = p1 + p2 + … pn

Humidifiers


Passive

Independent of any external power source or external water supply. 

HME (Heat and moisture exchangers) 

They function as heat and moisture exchangers - they take heat and moisture from the exhaled gas, which they add to the inspired gas during the next inspiration. Significant functional differences between different HMEs. 

Bubble humidifier

Inspiratory flow directed to the capillary system of the diffuser. 

Humidification efficiency is low, but it can be improved by increasing the water temperature.

A bubble bottle is mostly used in high-flow oxygen therapy by mask or nasal cannula to prevent drying out of the mucous membranes in the nose and mouth. 

Active

Moisture and heat supplied to the breathing gases by an electrically powered humidifier. 

Active humidifiers for breathing gases are determined by the ISO 8185 standard.

The minimum water content in inhaled gases is approx. 33 mg/dm³ and the maximum temperature of breathing gases is approx. 42 °C.

In a  flow-through vaporizer, the inspiratory flow is guided by a heated water bath – a variant of a bubble humidifier with active heating.

As a result, the surface vaporizer transports only water vapour and no water droplets into the patient. The advantage is that water vapour does not carry any germs.  

Therefore, the risk of transferring bacteria through surface vaporizers is minimal.

In the case of a surface vaporizer, the inspiratory flow is guided over the surface of the water.

As a result, the surface vaporizer transports only water vapour and no water droplets into the patient. The advantage is that water vapour does not carry any germs.  

Therefore, the risk of transferring bacteria through surface vaporizers is minimal.

In the case of a surface vaporizer, the inspiratory flow is guided over the surface of the water.

As a result, the surface vaporizer transports only water vapour and no water droplets into the patient. The advantage is that water vapour does not carry any germs.  

Therefore, the risk of transferring bacteria through surface vaporizers is minimal.

Conclusion

• The pressure of saturated water vapour always depends on the temperature.
• The rate of evaporation depends on the temperature.
• Appropriate thermomanagement in the delivery room has a high impact on reducing neonatal mortality, especially in preterm newborns. The positive effect of humidification and heating of the ventilation mixture.
• The time delay in heating the ventilation circuit of the resuscitation system to optimal parameters is at least 15 minutes.