Imaging the first breaths after birth using a synchrotron

Prof Stuart Hooper, Monash Institute for Medical Research

The transition to newborn life at birth represents one of the greatest physiological challenges that any human will encounter during their lives. Before birth the fetal lungs are filled with liquid and this liquid must be cleared at birth to allow the entry of air and the start of pulmonary gas exchange. This process of lung aeration is not only critical for the onset of air-breathing, but also triggers major changes in the cardiovascular system. These changes include rapid restructuring of the circulatory system, which transforms it into the adult phenotype that is required for independent life.

To study the process of lung aeration at birth, we have developed a X-ray imaging technique that uses synchrotron radiation to resolve the air/liquid interfaces in the lung with a high degree of resolution. The technique, called phase contrast X-ray imaging, uses the refractive index difference between air and water to produce contrast of all air/liquid boundaries within the lung. As the lung is liquid-filled before birth it displays no absorption contrast with surrounding tissues and no phase contrast and so is not visible using this technique. However, as air enters the lungs after birth the air-filled airways strongly exhibit contrast and immediately become visible. Consecutive images acquired during this process can be compiled into movies and, as a result, the entry air into the lungs can be visualized allowing the factors that regulate this process to be studied in detail. Using this technique we have identified the primary mechanisms regulating lung aeration at birth, which has overturned almost 40 years of accepted scientific wisdom. Furthermore, based on the concepts derived from this knowledge, we have been able to identify ventilation strategies that assist infants born very premature to aerate their lungs after birth. Premature infants commonly struggle to clear their lungs of liquid and commence effective gas exchange at birth. This can have severe consequences for the infant, including death or severe life-long disability, which requires substantial clinical intervention if it is to be avoided. Our primary research aim is to improve the outcomes for these infants, who are the most vulnerable in our society.