by Sruthy Sreekanth
Premature babies are generally very highly susceptible to lung infection/ lung disease because their lungs are not fully developed and cannot provide enough oxygen for producing a substance called “surfactant”, made of proteins and fats, which prevents the infant's lungs from collapsing and keeps it inflated by reducing the surface tension within the alveoli of the lungs.
Typically, healthy babies start to produce surfactants between the 24th to 28th weeks of pregnancy. However, premature babies may not have enough surfactant in their lungs, increasing the work of breathing needed to be done, since a lack of surfactant can cause the alveoli to collapse. As less oxygen is breathed in and as respiration progresses, more carbon dioxide begins to build up in the blood, leading to increased carbonic acid in the blood; a condition called “acidosis”. This makes the baby work much harder to let oxygen into the lungs and causes them to become more and more exhausted over time while doing so. Hence, a ventilator is needed to do the work of breathing instead.
A ventilator is a bedside machine that's attached to a breathing tube and this is placed into the trachea or windpipe of the premature baby; however there are quite a few risks involved in using a ventilator on infants. Sometimes, delivering oxygen directly into the lungs, under the influence of high pressure can damage the alveoli, in turn leading to air leaks. These air leaks can make it more difficult for the ventilator to help with the baby’s breathing, ultimately not serving its purpose. The risk involves two types of air leaks occurring, one being a more common type that occurs when air gets into the space between the lung and the inner chest wall and this is called “pneumothorax”. This can cause the alveoli to become overinflated and burst, causing high lung damage. The other type of air leak is called “pulmonary interstitial emphysema”, where there are air pockets present in the lung tissue around the alveoli and this air cannot be removed.
So, you may be wondering... How exactly do we find an alternative method that's safer for infants and helps them reduce experiencing risks posed by respiratory distress syndrome?
Introducing the more suitable alternative - bubble Continuous Positive Airway Pressure (CPAP)! Unlike mechanical ventilators, the bubble CPAP is less invasive and is considered to be the gentlest form of respiratory support as it applies low pressure to the infant's delicate alveoli, preventing damage, increasing the lungs functional residue, and hence decreasing the work of breathing required to let oxygen into the lungs. Developed in the mid 1970’s by Dr.Jen-Tien Wung at Columbia University (New York); this machine, blends and humidifies the oxygen that’s delivered to the baby through a nasal mask or via short bi nasal prongs, (tube-like structures) that go into both nostrils where one end of the expiratory tube called the “distal end” is placed in water. When this humidified oxygen is delivered through the circuit, bubbles come out of the tube, preventing the buildup of excess pressures. Hence, the name “bubble” CPAP.
Interesting, right? But how exactly does it work? What's the mechanism and process behind it? You must have so many questions running through your mind, just like me. So let's dive a little bit deeper into the functioning of this CPAP machine! :)
The bubble CPAP system consists of 3 main components:
A gas source - The gas source is a source containing oxygen and compressed air, which is connected to an oxygen blender in order to supply the appropriate concentration of oxygen for inspiration/inhalation.
A pressure generator - This creates a suitable pressure environment like the low pressure needed to prevent bursting of the infant’s air sacs, (alveoli) and is maintained by keeping the distal end of the respiratory tube underwater. This pressure, despite being low, is continuous and can be varied based on how deep the tube is placed in water.
An interface between the patient and the circuit (connecting the machine to the patient's nostrils) - Nasal prongs provide an interface between the infant's airways and the circuit connected to the CPAP machine. Usually, these prongs are short and wide to provide low resistance to the airflow, hence reducing the chances of air leakage.
In the future, researchers hope to see a greater rise in the lives saved for babies diagnosed with respiratory distress syndrome and aim to increase survival rate in most cases of neonatal RDS. The bubble CPAP machine continues to do wonders and researchers hope to maximize the efficiency of this machine to be able to reduce the risk of death from neonatal respiratory distress, ultimately striving towards maximizing the life span of such premature infants.
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