A neonatologist caring for my twins in the NICU once said, “if we could choose one organ to have a problem, let it be the lungs.” That’s because lung problems are among the easiest to fix in the short-term: just add more oxygen. It’s also because lungs continue to develop in newborns, all the way up until the child is around eight years old.
Nonetheless, supplemental oxygen has its downsides. In the short-term, because newborn babies’ brains are very sensitive, too much oxygen can cause brain damage. In the long-term, too much mechanical ventilation can cause chronic lung disease and bronchopulmonary dysplasia (BPD).
There’s a hierarchy of supplementary oxygen. From least potent to most:
- Blow-by oxygen – the nurse or doctor has an oxygen mask and passes it in front of the child’s face.
- Nasal cannula – tubes in the nose are connected to a mixed source of oxygen and fresh air
- Continuous positive airway pressure (CPAP) – a facemask that pushes a low-pressure mixture of oxygen (measured by the fractional inspired concentration, the FiO2)
- Positive pressure ventilation (also known as mechanical ventilation) – the child is intubated, with oxygen pushed into the lungs at higher pressure
- High-frequency oscillator ventilator– the child is intubated, with oxygen moving in and out at a frequency of 10 to 15 times per second
- High-frequency jet ventilator – the child is intubated, with cycled blasts of oxygen
- Extracorporeal membrane oxygenation (ECMO) – a heart-lung machine that processes oxygen in the bloodstream outside of the body
The high-frequency positive pressure ventilation strategies are becoming increasingly common, ever since a Cochrane Review in 2016 found that it and triggered ventilation showed benefits over conventional ventilation. But the benefits are not earth-shattering, and there’s typically no benefit in patients advocating for transitioning their baby to one.
With each type of supplemental oxygen, the goal in the NICU is to “wean” the baby down to a lower level of oxygen.
For most parents, the most startling jump is from CPAP to the mechanical ventilator (which nurses often call “the vent”). It can be upsetting, because it feels like the child is taking a step backwards. I sure felt it when my daughter went from CPAP to the vent to the oscillating ventilator. But there’s hope.
Mechanical ventilation is usually prescribed for acute respiratory distress, defined typically as:
- Too much acid in the blood (metabolic acidosis), as shown by an arterial pH below 7.2 and arterial carbon dioxide (PaCO2) above 60 mmHg.
- Too little oxygen in the blood (hypoxia), as shown by an arterial PaO2 below 50 mmHg, or when good oxygen saturdation cannot be sustained on a CPAP with less than 40% pure oxygen.
- Severe apnea.
The causes of that respiratory failure are numerous, like apnea of prematurity, infection, sepsis, recovery from a surgery, persistent pulmonary hypertension, or meconium aspiration syndrome. Each one of those problems will have to be treated separately – the ventilation is just a way to keep up oxygen levels for the child.