Ventilation

So you walk into the NICU and your baby is hooked up to approximately 41 million different machines. There are feeding pumps, medication pumps, and pulse-ox machines. There’s the suction tubing and the blood pressure cuff. There’s a lot going on, but it helps if you are able to look at each item individually, instead of getting overwhelmed by the chaos. (Organized chaos, I’m certain).

One of the most overwhelming parts of the NICU initially can be the ventilation devices. The following list is not all-inclusive, and of course, you should talk to the neonatologist as well as the respiratory therapist for personalized explanations. There are also different types of ventilators, which you should also discuss with the neo and the RT. Charlotte was only on the conventional vent and the oscillator vent while in the NICU. During her stint in the PICU last fall, she was on the jet vent for a bit.

SETTINGS ON A VENTILATOR

1. Mode: The way the breathing is delivered.

- Controlled Mechanical Ventilation: Ventilator determines the number of breaths taken, as well as the volume of those breaths. This is used for patients who are paralyzed or for patients with complete central apnea, as the ventilator will not allow the patient to breathe on their own at all.

- Pressure Support Ventilation (PSV): The patient determines the rate of inspirations, and the duration of the breath. The ventilator ensures that the patient is receiving the proper amount of pressure per breath (as opposed to the Assist Control, which ensures a certain amount of volume). This is set through the PIP (Peak Inspiratory Pressure, the pressure that keeps the lungs open upon inhalation) setting on the ventilator.

- Assist Control (A/C): The patient receives a breath they initiate it, as well as a set number of breaths per minute. The ventilator assists the patient with their breaths, helping them to reach the prescribed volume. When a patient initiates a breath on their own, the clock is reset for the mechanical inspiration. This mode of ventilation is not tolerated well when the patient is awake, meaning your child might be given a paralytic while on this ventilation setting.

- Intermittent Mandatory Ventilation (IMV): The patient is allowed to breathe independently except during certain prescribed intervals, when a ventilator delivers a breath either under positive pressure or in a measured volume. Basically, the patient is allowed to take breaths on their own, but there is a certain rate (every 5 seconds, every 15 seconds, etc) when the ventilator will deliver a breath, even if the patient is not breathing on their own. When patients are only breathing at the prescribed rate, this is called “riding the vent” and is an indication that either the patient is a) asleep or b) heavily reliant on the ventilator (some adjustments to the settings might be necessary).

- Synchronized Intermittent Mandatory Ventilation (SIMV): The patient receives three types of breaths. One is a mandatory, controlled breath through the ventilator which is given if the patient does not meet the required rate on their own. The second occurs where the patient can receive assisted or synchronized breaths (like A/C). Third, the patient can breath on their own, through a valve in the ventilator, which may or may not be pressure supported, depending on the strength of their breathing. SIMV method of ventilator helps babies to move towards CPAP and is tolerated without a paralytic better than other forms of ventilation.

2. Rate: The number of breaths per minute. Patients may breathe “over” the vent, meaning they are taking more breaths per minute than the rate set on the ventilator. This setting simply ensures a minimum amount of inspirations per minute.

3. Tidal Volume: Amount of air per breath. Leaks around the ET (endotracheal) tube can cause problems with this reading on the ventilator.

4. FiO2: Fraction of Inspired Oxygen. In other words, how much oxygen the patient is receiving per breath. Room Air’s FiO2 is 21%, meaning 21% of the air you are breathing in is oxygen. This number can range from 21%-100%. However, since learning that oxygen can have a negative effect on brain development, and can cause permanent eye damage, doctors try to keep the FiO2 as low as possible without compromising oxygen saturations. {it should be noted that preemies DO NOT need to maintain O2 sats as high as full term kids or adults. Charlotte was well over 36 weeks before they expected her O2 to be above 95%. Even now, at 20 months actual, 16 adjusted, they are not concerned unless her O2 levels are below 90% consistently.}

5. PEEP: Positive End Expiratory Pressure. Remember when we talked yesterday that your lungs inflate because of a negative pressure which is created when your chest wall pulls your lungs out? Well, you can imagine then, that when you exhale, your lungs might have a tendency to collapse. Naturally, our bodies don’t like this, so they try to keep the lungs open, just a little, when we exhale, so that it is easy to inhale the next time around. PEEP is that pressure which keeps the lungs from collapsing when you exhale. PEEP might be adjusted if they are trying to avoid increasing the FiO2 in an effort to increase oxygen saturations.

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