By Jim Church
At a recent meeting in Alaska, I had the opportunity to listen to EMTs from across the region talk about providing health care in a state that is mostly roadless, experiences extreme weather, and has frequent earthquakes and volcanic eruptions. Patient transport is frequently accomplished via dog sled, snow machine, air services (medical and commercial) and/or boat (commercial or Coast Guard).
One of the most interesting patient care stories I heard there is that of a prematurely delivered infant that required bag-valve-mask ventilation during the dog sled ride to the nearest airstrip in order to connect with a Medevac unit. Just let that sink in for a minute.
So how do you ventilate a prematurely born infant who is smaller in size than the average adult bag-valve-mask ventilation device you carry in your ambulance? The answer is “very carefully,” right?
Initial Response
A premature infant is one that is delivered before 37 weeks, three weeks before they are normally due to become air breathers. The more premature at delivery, the more likely the infant will experience problems such as hypothermia and respiratory distress. It is only due to advances in neonatal care that survival has reached about 90 percent for premature infants born at 28 weeks, approximately three months before they should arrive.
The newly born infant, regardless of gestational age, needs to be dried, warmed and stimulated — to which most infants respond vigorously. For those few who don’t respond, additional treatment may include supplemental oxygen, positive pressure ventilation, chest compressions for heart rates less than 60 beats per minute, and medications and/or fluid administration. Here we will focus on the respiratory component of this staged response.
Neonatal Respiratory Considerations
Fetal lungs are filled with fluid that expands and develops the lung until the trip though the birth canal. The first breaths of life help clear this fluid and replace it with air. Fetal lungs are designed to be ready to go at 40 weeks, and generally do okay if delivered a couple of weeks early; but delivery before 37 weeks, puts them at risk for respiratory distress or failure.
Current recommendation for respiratory resuscitation of a newborn, premature or otherwise, is to use supplemental oxygen if there is persistent cyanosis, despite adequate respiratory effort and a heart rate greater than 100.
If the newborn is not breathing, or the heart rate is less than 100, or there is persistent cyanosis despite supplemental oxygen, then begin positive pressure ventilation (BVM or tracheal tube) with supplemental oxygen. Squeezing the bag should produce no more than 30-40 centimeters of water to prevent over-inflation and related problems, such as a pneumothorax.
This ventilation pressure can be monitored by having a pressure gauge hooked to your ventilation tubing. However, if you don’t carry a pressure gauge for that infrequent out-of-hospital neonatal resuscitation, watch for the earliest hint of chest rise — easier to see in premature infants due to less body fat — and monitor for an increase in heart rate, which is a cardinal sign of adequate ventilation and oxygenation. Keep the ventilation rate at 40-60 per minute and, of course, initiate transport.
So, when do you intubate if that is an option within your scope of practice?
Fortunately, most term newborns require positive pressure ventilation respond prior to the need for tracheal tube insertion. Premature infants may be less responsive to BVM ventilation due to their immature lungs. A neonatal tracheal tube is indicated if:
- meconium is present and the infant exhibits respiratory distress or failure;
- BVM ventilation is prolonged or not working;
- chest compressions are required for persistent heart rate less than 60 beats per minute;
- tracheal tube administration of medications is indicated;
- or if there are special situations, such as a congenital diaphragmatic hernia complicating respiratory success.
Again, an increase in heart rate after intubation is a hallmark sign of adequate ventilation and oxygenation. Oxygen saturations should be followed to confirm and maintain adequate oxygenation.
Carbon dioxide monitors should be utilized with any intubation at any age to confirm placement and continuously trend levels of expired CO2. And CO2 waveforms can provide additional information such as the presence of bronchospasm, which produces a “shark fin” wave on the monitor. Any system that allows tracheal intubation in the field without CO2 confirmation and monitoring, preferably waveform, is putting their patients at risk and needlessly exposing the system and provider to potential legal problems in the event of a less than optimum outcome.
Once at a facility, a chest X-ray can determine the relationship of the tracheal tube tip to the bifurcation of the right and left main stem bronchi (carina), which indicates if a tube is too shallow or too deep. Chest X-ray does NOT confirm tube placement in the trachea; that is primarily the job of the CO2 detection device.
Although a heart beat is generally required to circulate CO2 to the lungs so that it can be detected in expired air by the CO2 monitoring device, effective chest compressions in a pulseless patient may circulate enough CO2 to the lungs to produce a small CO2 waveform. This device may be especially useful in the tiny premature infant where presence and/or location of breath sounds can be difficult to determine, especially if you are listening with an adult stethoscope.
Summary
On average, pediatric prehospital contacts account for only about 4 percent of total patient encounters in the field. Thus, we experience infrequent pediatric contact — even more infrequent for life threatening pediatric conditions, especially for distressed newborns, if they are prematurely born.
This makes it even more important that our approach is straightforward and progressive: dry, warm, stimulate, oxygenate, ventilate, chest compressions, and drugs/fluid. Repeat as necessary, all while moving towards the light (of the hospital emergency department entrance, of course).
References
American Heart Association. Part 13: Neonatal Resuscitation Guideline. Circulation 2005;112:IV-188-IV-195. Retrieved December 27, 2008 from http://circ.ahajournals.org/cgi/content/full/112/24_suppl/IV-188
