But when the patient is only the size of an adult's hand and has come into the world three months before its organs are ready to cope on their own, the doctor's 'ear' must be especially precise, non-invasive and safe.
Scientists at the Centre for Baby Health Research believe it is time to re-design the centuries-old stethoscope to cope with the unique demands of the premature infant. A team of biomedical scientists and clinicians, with the help of a $500,000 donation from Tattersalls, have combined to develop a sophisticated tool to detect minute changes in lung gas volume in premature babies.
The researchers are conducting trials of the technology on babies at the Monash Medical Centre. Their approach signals a major innovation in neonatal intensive care, where continuous monitoring of the lungs may prove both practical and possible for the first time.
Of the 5000 babies who undergo intensive care in Australia each year, three out of four have breathing difficulties that frequently lead to long-term lung disease. The chances of survival are now quite high, but usually only after a lengthy illness with potentially hazardous treatments involving high doses of steroids, and costly and stressful periods in an intensive care unit.
Dr Mal Wilkinson, a senior research fellow at the centre, says that getting the lungs working properly is critical to the overall health of the baby. "The lungs are where it all begins. Poorly functioning lungs impede the workings of the heart, which in turn affects the flow of blood and oxygen to all the vital organs."
Doctors use ventilators and artificial chemicals called surfactants to help inflate the lungs of the infant, but they have been frustrated by their inability to continuously monitor the subtle changes in the baby's lung sounds.
"We want to introduce a method where we can quantify the air space in the baby's lungs at any particular time, at the bedside, as unob-trusively as possible, over a period of days or even weeks. This just cannot be done now," Dr Wilkinson said.
The conventional stethoscope struggles to detect such minute sound variations. X-rays provide a good snapshot of the lungs but in such delicate infants their use is limited because of the radiation exposure and the disruption involved in positioning the child under the X-ray equipment. Ultrasound is ineffective because its penetration is inadequate. The air sacs of the lung scatter the ultrasound energy and, like shining a torch into a fog, all you see is fog.
But as designers of space craft and deep sea vehicles have known for a long time, low frequency sounds of around 500 Hz penetrate extremely well.
With the new technology, sound is directed into the baby's chest while tiny microphones on the chest are able to track those sounds as they bounce off the walls of the lungs. A computer then produces a sonogram for the clinician to diagnose the subtle changes occurring in abnormal lungs.
"Premature babies are born perfect," says Dr Wilkinson. "But we need the technology to be perfect to support them until they are ready to cope on their own."
The neonatal research team: Back row, from left, Ms Heather Neil, Ms Liz Skuza, Dr Mal Wilkinson, Ms Dyna Eldaief; front row, Dr Andrew Ramsden, Mr Vojta Brodecky and Dr Philip Berger.