28 March 2016

NICU Basics: Respiratory support

I thought we'd write a series of posts on 'NICU Basics', as there are so many medical terms and procedures to get to grips with. Often, whether you're having antenatal discussions or are actually in the NICU, you wonder what on earth they're talking about. Occasionally you might feel they're taking advantage of your lack of knowledge to fob you off or to fail to provide your child with appropriate care. So, in this post, we'll talk about the types of respiratory support that are available and what they do.

Low-flow oxygen

Also known as nasal cannula oxygen or simply oxygen.

This does what it says on the tin: it is oxygen piped from a central hospital supply in the NICU and delivered to your baby, either via a mask (rare in babies) or by prongs in the nose (the 'nasal cannula'). Oxygen is used when your baby is breathing independently but is unable to adequately oxygenate themselves, that is, they have chronic or acute 'hypoxemia'. This may be noticed via low oxygen saturation levels or by testing of levels of carbon dioxide and other substances in your baby's blood.

Your baby may be on a very low level of oxygen, such as 0.04 litres per minute (lpm), or a high level like 2 lpm.

Oxygen can be used at home where, instead of the hospital supply, the oxygen comes from cylinders which will be delivered to you or from a device that 'concentrates' oxygen from the air. Many babies with T18 do have oxygen at home, to manage or prevent desaturations.

Rumer on low-flow oxygen
Rumer on oxygen

High-flow therapy

May be known by brand names such as Vapotherm or Optiflow.

High-flow therapy is delivered via nasal cannula, just like low-flow oxygen. To avoid retention of carbon dioxide (CO2), the cannula must not take up more than 50% of the nostrils. High-flow works by delivering humidified air to the upper airways.

The air is actively blown into the airway (rather than simply being sucked in by breathing), and fills up the dead space, pushing out old air and providing a constant flow of fresh air. This helps the baby get oxygen into their airways and get rid of CO2, thus helping them ventilate. It also provides some pressure support, stopping the air sacs collapsing down after each breath, so the baby has to work less hard to breathe. Unlike CPAP, however, it is an open system rather than a sealed one, with the emphasis on removing old air and introducing new as opposed to maintaining a high background pressure.

Like low-flow oxygen, high-flow therapy is delivered in litres per minute, usually somewhere between approximately 3-8 lpm. The gas it provides can be room air (21% oxygen), or if the baby needs more, it may deliver, say, 8 lpm of gas at 35% oxygen.

High-flow works very well for many babies. The evidence suggests that it is as effective as CPAP, and some studies have even suggested it is more effective. It is well worth a try if CPAP isn't working well for your baby.

High-flow cannot usually be provided at home, but some families have managed to arrange for home use when their child needs long term high-flow therapy.

Rumer on Vapotherm (high-flow therapy)
Rumer on Vapotherm (high-flow therapy)

Continuous Positive Airway Pressure (CPAP)

CPAP is used to provide a continuous pressure in order to keep the airways open. This means the baby has to work less hard to breathe.

It is delivered via nasal prongs or a mask, and it is important that there is a good seal. A leak will make CPAP less effective.

CPAP has been around longer than high-flow therapy and is many physicians' preference. However, the evidence as to which is more effective is unclear.

CPAP is delivered at a selected PEEP (Positive End Expiratory Pressure), which is the pressure in the lungs above the pressure outside the body at the end of the 'out' breath. CPAP can use room air (21% oxygen) to generate pressure, or more oxygen can be added if it is needed. Like high-flow therapy, oxygen on CPAP is usually expressed as a Fraction of Inspired Oxygen (FIO2), that is to say, the percentage of the gas that is comprised of oxygen, eg. 40% oxygen.

CPAP can be used at home, and is often used for children with sleep apnea. However, all day use of the mask in the long term would not be sustainable for babies due to pressure sores - or, as one of Rumer's doctors put it: "It will squash her face."

Rumer receiving CPAP by mask
Rumer receiving CPAP by mask

Bi-level Positive Airway Pressure (BiPAP)

BiPAP is the halfway house between CPAP and intubation (see below). It offers two pressure levels: a background pressure (like CPAP) during 'out' breaths and a higher pressure to support each 'in' breath. So the baby breathes in and the BiPAP machine supports the breath; the baby breathes out and a positive level of pressure is maintained so that the baby's airways do not completely shut. BiPAP can also be set so that, if the baby doesn't breathe as frequently as is necessary, it can supply a breath even without the baby 'triggering' it (by starting to breathe in).

BiPAP provides a very high level of respiratory support; some studies suggest that it can be as effective and intubation and ventilation. BiPAP is sometimes used at home, but as with CPAP, long-term continuous mask use is not sustainable. Some children use BiPAP at nights only, for example in cases of sleep apnea.

BiPAP is generally delivered by mask, but some machines permit the use of nasal prongs. As with CPAP, mask seal is very important. BiPAP can be delivered using room air (21% oxygen), or higher percentages of oxygen can be supplied as needed.

Rumer on BiPAP via a Trilogy machine
Rumer on BiPAP via a Trilogy machine
(the mask was far too big for her)

Intubation and Mechanical Ventilation

Also known simply as intubation or ventilation.

This is the highest level of breathing support. A tube called an endotracheal tube (ETT) is inserted into the baby's airway ('intubation') and a machine called a ventilator is used to deliver breathing support ('ventilation').

As the tube is inserted directly into the space between the two lungs, this is the most effective form of breathing support. There are many different modes of ventilation that can be used; some provide breaths for the patient and some respond to the patients own breathing attempts by providing support, similarly to BiPAP. Some do both. You may find your child starts on one type of ventilation (eg. 'Assist Control', where the ventilator takes over breathing) and then, as they are doing better, the doctor switches to another mode (eg. 'SIMV', where the ventilator supports your baby's own breaths and provides breaths when your baby goes too long without triggering a breath themselves).

If, due to complex needs, your child cannot come off a ventilator, then long-term ventilation can be provided at home via a tracheostomy (a surgically-created hole in the throat). However, this is a high-risk, invasive procedure that should be carefully considered.

Ventilators can provide support using room air (21% oxygen) or can deliver higher concentrations of oxygen as needed (eg. 35% oxygen). Since delivering the air directly into your child's lower airway is so effective, your child may need lower concentrations of oxygen than on non-invasive ventilation such as BiPAP.

Intubation is uncomfortable for a child, and sedation will be used when initially intubating. Low-dose sedatives are normally continued until a child is 'extubated' (ie. when the tube is removed and ventilation ceased). After extubation, you may find your child has a sore throat and is unable to cry for a few days.

Rumer with Chris, intubated by mouth in NICU
Intubated by mouth in NICU
Rumer intubated nasally in PICU
Intubated nasally in PICU


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