John Crowe and colleagues describe the process of developing a pulse monitor for newborn babies.
for monitoring physiological functions such as heart and breathing
rates, temperature and blood pressure are now widely and cheaply
available. Consequently, it is rare that the opportunity arises to
consider the ergonomics of a new physiological monitor. However, this
opportunity did arise in a collaborative project between the Faculty of
Engineering and the Department of Child Health at the University of
The team are developing an optical based sensor, named
HeartLight, that can record the cardiac synchronous variations in blood
volume, that is, the pulse, from which heart rate can be calculated.
monitor is to be used during the resuscitation of newborn infants,
necessary in 10% of births. The aim is to remove the need for
practitioners to suspend the resuscitation process in order to manually
measure the baby’s heart rate by counting the beats whilst listening
with a stethoscope. It also aims to reduce the risk of errors that are
known to occur during manual counting.
The capture of user
requirements in this project was essential to the development of the
instrumentation. Therefore, the collaboration of human factors
academics, clinical consultants and research nurses was vital to the
iterative process around which the heart monitor was developed.
ergonomic requirements of this sensor are twofold. First, the design of
the sensor and its attachment mechanism and second, how the calculated
heart rate is relayed to the practitioner. Sensor placement must fit
within clinical practice that involves placing the premature baby in a
polythene wrap/bag and putting a hat on them to avoid hypothermia.
sensor requires contact with the surface of the skin on an area where
it is thin enough for the fluctuations in blood volume to be measured.
Studies demonstrated that the sensor placement on the forehead obtained
reliable results within these parameters. This fact presented a viable
solution for attachment of the device. By placing the sensor under the
hat against the forehead it presented an optimal position for
monitoring. Another benefit of this placement was that the sensor would
be unlikely to be dislodged during the resuscitation process.
scale of technology for use with neonates is another significant
consideration. Engineers working on this project have had to consider
the specialist requirements and critical time pressures of a
resuscitation environment; multiple sensors and alarms, medical devices
and hardware with wiring, in addition the need for practitioners to
carry out the resuscitation process on a small baby. Technology
requirements therefore have to be developed for both the adult clinical
user and the tiny patient.
The display of heart rate measures
raises more questions. Should the output be visual or audible? What
format should this take? Do less experienced clinical staff need more
information? What if more than one practitioner is in attendance and how
do they share the workload and processing of this information? What
accuracy is needed for the information to be effective in this
These issues have proven interesting to
investigate since it encompasses the resolution of the output value and
the rate of update. The requirements of neonatologists, environmental
considerations and quality and quantity of information that they work
with provides a complex backdrop to these issues.
project is ongoing. Not only do the practical issues of carrying out
development and testing of a new device provide challenges to the team,
but the additional complications of working with babies and their
families and the sensitivity required in emergency scenarios, such as
resuscitation, is a significant facet of the work being carried out.
these challenges, the expectations of the device within clinical
practice and survival rates for neonates are high. The inclusion of
ergonomics from the start of the process has made the eventual roll out
of this device more feasible due to the approaches taken early on in its
By John Crowe, Alexandra Lang & Don Sharkey