RDS Therapies

Ventilation can damage alveolar cells by disrupting the cell junctions. Furthermore, some parts of the lung may over inflate and rupture. When damage occurs the epithelial lining of the lung is disrupted and plasma leaks into the alveolar spaces. This estudate inhibits surfactant function and oxygen uptake, further compromising the infant.
Damage to the cells lining the lung causes an inflammatory response mediated via neutrophils and cytokines. The neonatal lung is not well prepared to resist this inflammation and may be permanently damaged and scarred.

Shearing
Surfactant deficient alveoli have a tendency to collapse at the end of a breath. When an alveoli collapses the opposing walls tend to stick together – much like two panes of glass. The walls of the alveoli tend to move in laterally and this movement causes the alveoli walls to shear thus causing further physical damage.

Oxygen toxicity
Oxygen normally exists in a neutrally charged state. However oxygen can also exist in a number of other states known as reactive oxygen species and these are highly reactive. Despite having an extremely short life, when these molecules come into contact with organic molecules such as the lipids found in cell membranes they react with them. This damages the cellular structures.
For a normal lung these oxygen free radicals do not pose a problem because:

• At 21% oxygen concentrations (air) their formation is low
• Our lungs are equipped with a number of anti-oxidant defences such as superoxide dismutase

Lung damage through ventilation
Ventilation damages neonatal lungs by:

• Inhalation of high concentrations of oxygen exposing the infant to reactive oxygen species.
• High ventilatory pressures damage the lung through overinflation.
• Cycle of inflation and collapse.

Van Marter reported that mechanical ventilation with high-inspired oxygen concentrations and high PIP in infants between 500-1,500 gr. birth weight was associated with an increased risk of developing Bronchopulmonary Dysplasia (BPD).
Many clinicians have therefore adopted strategies aimed at lowering inspired oxygen concentrations and ventilatory pressures where possible

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