Physiotherapy chest mat. Rachael Gregson using the physiotherapy chest mat she developed, on a baby in intensive care. The baby has a respiratory illness. The mat measures the pressure applied to the child's chest wall as it is being massaged. Breathing is also monitored before, during and after treatment. The data is collated and used to determine the effectiveness of the massage techniques used. Rachael Gregson is a research fellow at the University of Southampton and Great Ormond Street Hospital.