Between six and eight of every 100 women who get pregnant develop a dangerous pregnancy-related medical condition called preeclampsia. Preeclampsia, characterized by high blood pressure and high levels of protein in the urine, is usually diagnosed after week 32 but, in some cases, symptoms appear as early as week 20. Pulmonary edema, which can escalate into respiratory failure, is a serious risk that can now be identified early and easy using lung ultrasound scans.

At France's Hospital Nord in Marseille, Dr. Marc Leone and his team of researchers used traditional screening methods for pulmonary edema (excess fluid in the lungs) and ultrasound scans to see if either method proved more effective. Leone says the lung ultrasound "allowed us to quickly assess whether a woman with preeclampsia had pulmonary edema and confirm the severity of the condition."

The traditional approach to diagnosing pulmonary edema in preeclamptic patients is the measure of urinary output although the Leone team says results are accurate only about half the time. The researchers tested this method against two forms of ultrasound screening — pulmonary (lungs) and cardiac (heart).

Cardiac ultrasounds were conducted because pulmonary edema is a sign of heart failure although lung inflammation causes it, too. Cardiac ultrasounds require special equipment that maternity wards may not have readily available. Lung ultrasounds can be done with the same equipment used for fetal ultrasound scans.

The Leone research team enlisted 20 women diagnosed with severe preeclampsia for the study. Each woman was given a lung ultrasound and a cardiac ultrasound before delivery and again after delivery. The screenings indicated that before delivery:

  • 25% (5 each) of the women had non-cardiac pulmonary edema as detected with lung ultrasound.
  • 20% (4 each) of the women had non-cardiac pulmonary edema according to cardiac ultrasound.

The conclusion is that the lung ultrasound is more effective than cardiac ultrasound, which missed one case (5%) of pulmonary edema in the study group.

Lung ultrasound relies on the presence of white lines that look similar to comet trails on the ultrasound screen. These lines represent water in the lungs being reflected by the ultrasound technology. When three or more lines are visible, pulmonary edema is strongly indicated.

When pulmonary edema is diagnosed, the patient is typically treated with medication that lowers blood pressure, administration of oxygen, diuretics that expel excess fluids from the body, or some combination of the three.

These treatment options may not be so effective when the problem is pulmonary rather than cardiac edema. An added benefit of the lung ultrasound is that the state of edema can be monitored easily and non-invasively to gauge real-time effectiveness of whatever treatment plan is pursued.

Source: Leone, Marc, MD, Ph.D., et al. "Lung Ultrasound Predicts Interstitial Syndrome and Hemodynamic Profile in Parturients with Severe Preeclampsia." Anesthesiology. American Society of Anesthesiologists / Lippincott Williams & Wilkins. 2014. Web. Apr 1, 2014.