Someone mentioned upthread that processes in a newborns lungs continued to operate and would allow for air in veins to eventually exit and the baby would eventually recover. Is that why embolisms in adults could be more fatal because that process has stopped? Would explain the recoveries in what mostly seems to be premature babies.
This is incorrect. I am sorry but this will be very long.
Everyone's lungs can exhale the air in an air embolism, IF the heart is still beating (to move the air), AND the air has entered through venous circulation (because it will go to Right Atrium, Right Ventricle and lungs), AND there is not too much air AND there are no connections between venous and arterial circulation in the heart. Every one of these conditions must be met for the lungs to POTENTIALLY be able to filter out the air before it reaches the arteries feeding oxygen to the heart, and the brain. In this case, the embolism may not cause much damage. I will explain why in a moment. On the other hand,
ONCE air has entered arterial circulation through the heart or lungs, the air will go to the coronary artery (which feeds oxygen to the heart) and to the brain. Both of these circumstances will cause (potentially fatal) damage to the heart muscle and to the brain.
Whether or not it is fatal depends on HOW MUCH AIR and HOW FAST IT GETS IN. A lot of air getting to the heart or brain will kill a lot of cells in the heart or brain. A small amount of air will kill a small amount. It is not mysterious or confusing that sometimes air embolism is fatal and sometimes it is not. (Please let me know if you need elaboration after reading the rest of this post.)
Now I will explain the differences between normal newborn circulation and anatomically normal adult circulation. Then I will explain why babies are MORE (not LESS) susceptible to venous embolisms than adults. Then I will explain why in most cases of collapse, newborn babies respond to CPR even temporarily and why they might not respond if the cause of collapse is an air embolism.
Normal adult circulation follows this pathway: Blood that is at the edges of the body comes from the capillaries to the veins. All the veins travel back towards the heart. These veins are carrying blood whose oxygen has been used up by the body. All this blood meets at the right atrium of the heart. The blood then goes to the right ventricle of the heart. Then it travels through the pulmonary artery to the lungs. The blood circulates in the capillary bed of the lungs and exchanges gas there through the alveoli (tiny air sacs in the lungs). This is where carbon dioxide goes out, and oxygen comes in. This is where an air embolism could potentially be filtered. Then freshly oxygenated blood returns to the left atrium of the heart by the pulmonary vein. Then blood goes into the left ventricle. From the left ventricle, blood goes into the aorta.
Now, this is really important!
When blood comes to the aorta, the VERY FIRST PLACE vessels that branch off the aorta go to the heart! All this fresh oxygenated blood feeds the coronary arteries, which feed the heart. If this circulation is blocked, the heart muscle is starved of oxygen. It cannot beat and then it stops. This is commonly known as a heart attack. Those coronary arteries can be blocked by air or clots (emboli), or they can be blocked by plaque that forms on the walls of those arteries. After the heart has gotten it's share of the blood, the next branch takes blood to the brain. And after that blood goes to all the arteries of the body, down to the tissues, where it meets venous circulation in the capillaries, and the cycle starts all over again. (Although really, the cycle properly starts in the heart, I chose to start from the capillaries because that is the route that medicines administered through an intravenous line will travel.)
Now you can see if there is only a small amount of air, it can be filtered by the lungs. If there is a very LARGE amount of air, it will still get into arterial circulation (like a cup overflowing) and then it can cause problems.
Newborn circulation is a little different. Before babies are born, they do not use their lungs to exchange gases. Mom's placenta does that.
So babies have a special vessel called a ductus arteriosus. It lets blood flow between their main lung artery (pulmonary artery) and their main body artery (aorta). Very little blood goes to the lungs. It goes around the lungs through the DA. (There are vessels that travel to and from the placenta bringing oxygenated blood to the heart.) When the baby is born, the baby begins using their lungs and their circulation begins to resemble adult circulation. It no longer flows through the placental circuit, which I am omitting here for brevity. Over the first week of life or so, that DA starts to close off and become non functional. Eventually it no longer exists as a vessel, although early on, a respiratory or cardiac arrest can lead to it opening up again.
Preterm babies may take longer to close the ductus arteriosus than term babies.
This DA, which is still open at birth, is what makes newborns MORE vulnerable to air entering the veins. There is a place for the air to get to the heart and brain without going to the lungs first.
Now, why do most newborns need CPR? (NRP). At birth, when placental circulation is interrupted, the first thing the baby must do is take a big breath, inflate the lungs, and send oxygenated blood to the heart. Premature babies lack a protein in the lungs called surfactant. This is kind of like soap. It reduces surface tension in the lungs and lets the lungs inflate easily. Without surfactant, the lungs stick together and they are hard to inflate. We can help inflate the lungs using a bag mask setup that pushes air into the lungs.
If a newborn baby was experiencing low oxygen below birth, they may not have the urge to take a breath. Then they may need an inflating breath to get the oxygenated blood to the heart and and brain so they can get the urge to take more breaths.
Sometimes if a baby has been without oxygen for too long, an now the heart is beating to slowly to move any oxygen that does get into the lungs around the body. This baby needs chest compressions in addition to positive pressure ventilation.
The primary cause of cardiac arrest in adults is cardiac failure. The heart is not working. Adults usually need extensive chest compressions to survive after a heart attack. It matters more whether you give good quality chest compressions than it does that you give rescue breaths.
The primary cause of cardiac arrest in newborn babies is RESPIRATORY FAILURE. The baby is not breathing for one reason or another or the lungs are not working. As soon as the lungs are inflated and air is moving, the heart can start working again. Most babies who need resuscitation at birth or while in the NICU will recover once there is enough air going in and out of the air sacs in their lungs. They ONLY NEED BREATHS. This can be done with mask breaths, or through a breathing tube. Chest compressions are only needed to keep the blood circulating while the heart is beating too slow. After a couple rounds of chest compressions and breath cycles, the baby's heart is beating fast enough to carry blood, and they are breathing on their own or with assistance. Sometimes the baby is very sick and they will die later, often not in another code but because it is judged to be not in their best interests to escalate care.
It is uncommon for the baby's heart not to beat at all during heart rate checks. Compressions are usually given because the heart is beating too slow, not because it is not beating at all. Now, why might a baby's heart stop and not recover with standard resuscitation efforts? There are many reasons, usually having to do with a baby who is very sick. Very very sick. But also, if the coronary arteries were all full of air and too much of the heart muscles have stopped working (died), that would unfortunately do it.