[ozmidwifery] Fetal lung fluid.. again...

[Gayle Rafferty]

Found these couple of articles on the net, but can't find anything to say that the 'squeeze' doesn't happen.  These also don't say that it is necessary to have the squeeze either as the fluid is reabsorbed by various methods.  Interesting again...  Gayle ------------------------------------------------------------- The placenta provides exchange of O2 and CO2 for the fetus. Fetal lungs develop throughout gestation, and fairly well developed alveoli are present by the 25th wk. The fetal lungs continually produce fluid, a transudate from pulmonary capillaries plus some pulmonary surfactant secreted by type II pneumocytes. Fetal breathing movements occur intermittently, usually about 1/3 of the time during rapid eye movement sleep. Lung fluid moves up through the tracheobronchial tree and contributes to amniotic fluid. Fetal breathing movements appear to be essential for lung development and for the neuromuscular control of breathing, which the newborn needs to survive. For normal gas exchange to occur at birth, pulmonary alveolar and interstitial fluid must be cleared promptly. There are two mechanisms to accomplish this: (1) During vaginal delivery, the fetal thorax is compressed, expelling some lung fluid. As the thorax is delivered, elastic recoil of the ribs draws some air into the pulmonary tree. The first strong inspiratory efforts further fill the alveoli with air. (2) Fetal epinephrine and norepinephrine levels rise during labor and increase the active absorption of sodium and fluid across the respiratory epithelium via epithelial sodium channels. Neonatal wet lung syndrome (transient tachypnea of the newborn--see Respiratory Disorders in Ch. 260) is probably caused by delay in the active resorption of fetal lung sodium and fluid via epithelial sodium channels. http://www.merck.com/pubs/mmanual/section19/chapter256/256a.htm 39-30 WHAT IS THE WET LUNG SYNDROME? Before delivery the fetal lungs are not collapsed but filled with lung fluid. At vaginal delivery, most of this fluid is squeezed out of the lungs as the chest is compressed in the birth canal. After birth the remaining fluid is coughed up or is absorbed within a few minutes. In some infants this rapid removal of fetal lung fluid does not take place resulting in the wet lung syndrome which presents as respiratory distress. The wet lung syndrome is the commonest cause of respiratory distress. It is also important because during the first day of life it can easily be confused with hyaline membrane disease. The wet lung syndrome is seen in both term and preterm infants, especially after fetal distress, maternal sedation, caesarean section and polyhydramnios. In these infants the normal clearance of lung fluid is often delayed for many hours resulting in the wet lung syndrome. 39-31 HOW CAN YOU DIAGNOSE THE WET LUNG SYNDROME? These infants may be born at or before term. Most are term. They develop respiratory distress from delivery. Their clinical signs gradually improve. The shake test on the gastric aspirate is positive, which excludes hyaline membrane disease. THE WET LUNG SYNDROME IS THE COMMONEST CAUSE OF RESPIRATORY DISTRESS http://www.pepcourse.co.za/newborncare/Unit39_p3.html