Lung surfactant

During STRUCTURE AND FUNCTION OF LIPIDS lecture to Year 1 Medicine, I forgot about Phospholipids structure and function, and did not cover its significance. So students will need to read up on their own. I have provided a brief guide below to help you with your reading.

If you remember, I talked about surface tension of water in my lecture. I showed the glass tubes with the 2 different water curvature at the water-air interface. The application of that is when we talk about phospholipids. Phospholipids have 2 main functions in our bodies. One function is for making lipid bilayer membrane. The second function is as lung surfactant - to reduce the surface tension of water-air interface in the lung alveoli, so breathing can occur (inhale and exhale, without the alveoli collapsing). However, some newborns lack the pulmonary surfactant, and thus suffer from respiratory distress syndrome (RDS).

RDS is a medical emergency. RDS is a breathing disorder that affects newborns. RDS rarely occurs in full-term infants. The disorder is more common in premature infants born about 6 weeks or more before their due dates. RDS is a common lung disorder in premature infants. In fact, nearly all infants born before 28 weeks of pregnancy develop RDS. They may survive for a few days but often succumb within a week. 

Sometimes big babies born at term also experienced RDS. Since they are big babies, they experienced difficulties during delivery, often due to shoulder dystocia (sukar nak keluar bahu bayi). The baby struggles and in the end makes it but had swallowed some of the amniotic fluid and bacteria during the ordeal and suffers from RDS. So it is worth avoiding having big babies.

Interesting reads in medical history are:

1. Discovery of lung surfactant by Kurt von Neergaard in 1929
2. Discovery of the detailed mechanism of how pulmonary surfactant functions in 1950s
3. Death of Jacqueline Kennedy's newborn son in 1963 despite best efforts
4. Reduced deaths of newborns when RDS was treatable
5. Manufacture of lung surfactants - artificial and natural  (from cows and pigs)

From the laboratory aspect, it is possible to detect whether the lungs have fully developed and whether newborns will be able to use their lungs. The test done is called L/S ratio. L stands for lecithin and S stands for sphingomyelin. The L/S ratio is the ratio of lecithin to sphingomyelin. It tells us whether the lungs are mature or not, will function alright or otherwise, whether the baby is ready to breathe on its own or not, etc. The L/S ratio was much depended upon in the past.

Pulmonary surfactant
http://en.wikipedia.org/wiki/Pulmonary_surfactant

Respiratory Distress Syndrome (RDS)
http://www.thoracic.org/education/breathing-in-america/resources/chapter-19-respiratory-distress-syndr.pdf

National Heart Lung and Blood Institute (NHLBI)
http://www.nhlbi.nih.gov/health/health-topics/topics/rds/

American Lung Association
http://www.lung.org/#