How to Read the NICU Monitors

What You Should Know About Vital Signs

When you have a baby in the NICU, you will become all too familiar with the symphony of sounds that accompany this environment. It’s hard not to become reliant and almost obsessed with the monitor as it is the one constant in the NICU. You’ve probably been told in neonatal lingo, what a “Brady” is and what a “desat” is and may have even started referring to them as “episodes.” But truly knowing and understanding the "what" and "why" of all the wires and the monitor can help put your mind at ease.

Every baby in a neonatal intensive care unit will be monitored on something called a cardiopulmonary monitor. Basically, this is a system that consists of wires with electrodes that stick to the baby; two on either side of the chest, and one on the lower abdomen or on a leg. These electrodes are attached by wires and detect every activity of the heart and transmit it to the monitor where it is recorded and displayed as a waveform on the screen.

The system also measures the baby’s respiratory rate, (how fast the breathing is) has the capacity to record the oxygen saturation (O2 sat) within the blood, (measured by a probe that is either attached to the hand or foot) and also measure the baby’s blood pressure; either by cuff reading or by a real time reading through the artery in the umbilicus, (UAC) wrist, or foot. An arterial reading is translated into a waveform that can be seen on the monitor. This continual readout of blood pressure is typically used at the beginning of a NICU stay and in more critical conditions.

Blood pressure ​

Blood pressure is measured in two numbers, systolic and diastolic. Systolic is the pressure when the heart contracts and diastolic is the pressure when the heart is relaxed. Normal blood pressure for a premature baby varies depending on gestational age. Typically in the NICU, we want the blood pressure median (the middle number) that is measured between the systolic and diastolic, to be around the gestational age of the baby.

The purpose of blood pressure monitoring in a premature infant is to make sure the baby’s blood pressure does not fall too low. Low blood pressure is common in a preterm baby right after birth but can also be caused by infection, blood or fluid loss, and some medications. Raising the baby’s blood pressure can be as simple as giving extra fluid by I.V. which increases the baby’s blood volume, which in turn improves cardiac function. Medications called vasopressors may also be used. The most commonly used medications are dopamine, dobutamine, and epinephrine. These medications work by increasing the baby’s heart rate, constricting blood vessels, and increasing blood flow to the vital organs. 

The normal heart rate for a premature baby is between 120-160 beeps per minute. It is not uncommon to see the baby’s heart rate jump up to 200 when they are agitated, hungry, or upset. A preemie’s normal breathing rate is between 30-60 breaths per minute. Oxygen saturation normal values also vary based on the gestational age of the baby. A consistently increased heart rate can be an indication of anemia, a decrease in red blood cells (red blood cells carry oxygen to the body’s vital organs).

The monitor has parameters that are set to alarm if the numbers fall below or above what is expected. It is not uncommon to have false alarms when the baby moves, or if the electrodes become detached. It is important to get in the habit of looking at your baby and recognizing your preemie’s skin color and movements, and when they do and do not match up with the monitor alarms and waveforms.

What Is Bradycardia & Why Does It Happen? 

Bradycardia is the slowing of the heart. When a baby’s heart begins to slow, there is decreased blood flow to the lungs and oxygen to the tissues drops. Bradycardia in a premature baby is defined as a heart rate lower than 100 beats per minute. Bradycardia is an expected normal part of prematurity because the nervous system is immature. The heart is regulated by a part of the nervous system called the autonomic nervous system (ANS). In most situations, we are unaware of the workings of the ANS because it functions in an involuntary, reflexive manner and is out of our conscious control.

The ANS is divided into the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system uses the fight or flight response and increases blood pressure, and the heart beats faster. The parasympathetic nervous system works to save energy and decreases blood pressure and the heart beats slower. In a mature nervous system, these work in cadence, allowing the respiratory rate and blood pressure to be somewhat stable. In a premature baby, the nervous system is immature, and these systems, therefore, can get out of rhythm causing inconstancies which can lead to bradycardia.

Premature babies can have triggers that cause them to have episodes of bradycardia. Simple stimulation, eating, inserting a feeding tube, and reflux can trigger a preemie into having an episode of bradycardia. Depending on the cause of the Brady will depend on the intervention. Normal preemie bradycardia can sometimes self-resolve when the nervous system is triggered to chime in. If this does not happen, the baby will need stimulation, either by light touch or a vigorous flick of the foot or rubbing of the back. In some situations, the baby will need oxygen or an increase in oxygen. Caffeine is a medication that is used if the bradycardia is caused by apnea (a pause in breathing). Sometimes Brady's are warning signs that something might be medically wrong such as an infection. In most cases, as the baby grows and the nervous system matures, they will grow out of it.

What Is Apnea?

Apnea is a term for the absence of breathing or pause in breathing and is fairly common in premature babies. The more premature the baby, the greater the chances that apnea will occur. Apnea of prematurity is usually caused by an immature central nervous system. The centers that control breathing are not fully developed and can be unreliable. However, apnea spells can be triggered by other reasons and can indicate:

  • That the baby may be getting an infection.
  • Bleeding or tissue damage in the brain.
  • gastrointestinal problems such as reflux. (When the stomach contents move back up into the esophagus.) 
  • Too low or too high levels of chemicals in the body, such as glucose or calcium. 
  • Stimulation of reflexes that can trigger apnea such as with feeding tubes or suctioning, and unstable temperature. 

When apnea occurs, stimulation by rubbing the back or foot can help remind the baby to begin breathing again. Most premature babies will outgrow apnea of prematurity typically by the time they reach 36 weeks gestation. The short pauses are not harmful to the preemie but if they occur frequently, the baby will be put on a medication (typically caffeine) to help stimulate the central nervous system.

The monitors are a big part of the NICU as they display ongoing information about the baby’s vital signs. All the bells and bongs can be very unsettling at first. But knowing what each alarm is and what it means can help make you feel more comfortable with your baby. The monitors often become a very valuable source of information for parents, and it actually might be difficult to adjust to their absence when you are discharged home. It can be very exciting and scary at the same time to finally have a cordless, wireless baby.

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