NCM 104SKILLS

DETERMINING FETAL LUNG MATURITY :

SHAKE TEST

SHAKE TEST or FOAM STABILTY TEST Is a simple and

inexpensive test for determining fetal lung maturity based on the ability of surfactant in the amniotic fluid to form bubbles or foam in the presence of ethanol.

It is quick and may be accomplished in 15 to 30 minutes.

(FOAM STABILITY TEST) In this test, a fixed amount

of amniotic fluid is mixed with volume of 95% ethanol in a series of tubes with alcohol concentration ranging from 0.43 – 0.55.

The mixture is shaken for 30 seconds and the contents are allowed to settle for 15 seconds and the samples are examined for uninterrupted ring of foam in the tube.

(FOAM STABILITY TEST) The principle of the test

is that more surfactant is needed to maintain the foam in greater concentrations of ethanol and more fetal lung surfactant is needed to support fetal lung function at birth.

An index of 0.47 or higher is considered to indicate enough fetal lung surfactant for fetal lung maturity

SHAKE TEST PROCEDURE: A. Place exact amount of

95% ethanol, isotonic saline and amniotic fluid in a glass test tube.

B. Shake the mixture for 15 - 30 seconds until foam or bubbles form on the surface.

C. Let it stand for 15 minutes.

D. Interpret the results.

SHAKE TEST

INTERPRETATION:

The finding of a persistent ring of bubbles on the surface of the mixture after 15 minutes indicates a POSTIVE SHAKE TEST, indicating lung maturity.

Shake test has a high – false negative rate but a low false – positive rate.

To ensure a more accurate detection of fetal lung maturity, a MATURITY CASCADE TESTING SYSTEM for fetal maturity was developed by Garite and Freeman:

The foam stability test or shake test is done first. If it indicates maturity, no other test is done. Only a shake test is needed in more than half the time (63%).

If the results are inconclusive or indicate immaturity, the FLUORESCENT POLARIZATION TEST, also called MICRO – VISCOMETRY, is performed. Values of 0.320 are associated with fetal lung maturity.

MICROVISCOSITY FLUORESCENCE POLARIZATION ASSAY

- Measures fetal lung surfactant.- This assay provides a fluorescence

polarization (P) surfactant’s albumin ratio.- Phospholipids decrease the microviscosity of

amniotic fluid and this change in microviscosity is measured through fluorescent polarization.

- In this test, a fluorescent dye that binds to both albumin and surfactant is added to amniotic fluid sample.

If again inconclusive, the L/S RATIO is completed.

L/S RATIO The test is performed between 34 weeks and 38

weeks. Measures the levels of lecithin, sphingomyelin and

phosphatidyl glycerol, and an amniocentesis will be required.

As the lungs mature, the levels of lecithin rise and those of sphingomyelin decrease. Both these are found in the amniotic fluid, and the ratio between them will indicate the maturity of the lungs.

The amniotic fluid will also reveal the presence of phosphatidyl glycerol.

PULMONARY SURFACTANTo Is the substance that lines the alveoli of

the lungs which lowers the surface tension of the alveoli during respiratory exhalation.

o It is composed of phospholipids: Lecithin (L) the most abundant (80%) Sphingomyelin (S) Phosphatidylinositol (PI) Phosphatidyl glycerol (PG) Phosphatidyl phosphorus (PP)

o Of the phosphalipids in surfactant, LECITHIN (L) and SPYNGOMYELIN (S)are important in determining lung maturity.

o In early pregnancy, the concentration of sphyngomyelin in amniotic fluid is greater than that of lecithin.

o At 30 – 32 weeks, there are equal sphyngomyelin and lecithin concentrations.

o At 35 weeks, lecithin concentration exceeds that of spyngomyelin and an L/S ratio of 2:1 is usually reached.

Fetal lung maturity is assessed with 98% accuracy when the L/S ratio is 2:1 or greater.

Infants of diabetic mothers are an exception to this and have a high incidence of false positives, which means that the L/S ratio of 2:1 may not indicate lung maturity.

In diabetic women, the presence of PHOSPHATIDYL GLYCEROL (PG) which is the second most abundant phospholipid helps determine lung maturity in fetuses.

Advantage: the presence of blood and meconium in the amniotic fluid does not invalidate this test result

LIMITATIONS OF L/S RATIO A. Expensive and time consuming: takes 4

to 5 hours to obtain if done in the same facility (24 hours if sent away to a laboratory).

B. The presence of blood or other contaminants alters the L/S ratio results.

Phosphatidylglyerol (PG) may be used in blood contaminated specimens. Since it is not present in the blood, or vaginal fluids, its presence in amniotic fluid is reliable in predicting lung maturity.

LIMITATIONS OF L/S RATIO C. There is a high rate of inaccuracy in

prediction, i.e., predicting immaturity when the fetus is really mature.

Lung maturity has been most frequently assessed by a combination of the L/S ratio and PG and can be confirmed in most pregnancies if phosphatidylglycerol (PG) is present in conjunction with an L/S ratio of 2:1.

NCM 104SKILLS

PERFORMING ROLL - OVER TEST

ROLL - OVER TEST  Most widely performed test to trace who are

prone to developing PIH.

Comparison of the blood pressure of a pregnant woman lying on her back versus on her side; an excessive increase when she rolls to the supine position indicates increased risk of preeclampsia.

Performed between 28 and 32 weeks age of gestation.

PERFORMING ROLL – OVER TEST

A. Check blood pressure with the client in the lateral position until stable. This may take approximately 5 - 10 minutes.

B. The blood pressure cuff left loosely in place, roll client to supine to supine position.

C. Check blood pressure immediately. D. Wait for 5 minutes. E. Check blood pressure again focusing on

the diastolic reading.

PERFORMING ROLL – OVER TEST

Interpret Results:1. Positive Test: An increase of 20 mmHg

or more in the diastolic pressure at the 5 – minute interval.

2. Negative Test: Less than 20 mmHg rise in diastolic blood pressure at the 5 – minute reading.

G. Do recording and reporting.