Numerical Simulation of the Flow and Concentration Fields for Oxygen Delivery Systems

A novel mainstream capnometer system for non-intubated pediatric patients requiring oxygen administration

Capnometer has been widely used as a respiratory monitor. Stable carbon dioxide (CO(2)) monitoring of non-intubated patient is especially problematic due to the frequent occurrence of tube obstruction and it could be even more difficult when oxygen is being administered. Oxygen is often administered by an oxygen mask or oxygen nasal cannula; however there are some problems with these methods. For oxygen masks, it is necessary to provide high-flow oxygen to prevent rebreathing of exhaled CO(2), and as for oxygen nasal cannula, it is incapable of increasing the oxygen concentration and patient may feel uncomfortable during oxygen administration because it could dry nasal mucous. To solve these problems, we developed a novel mainstream capnometer system, which provides stable monitoring of exhaled CO(2) while administering oxygen. This capnometer system has a mask with an opening large enough to facilitate the observation of patient's nose and mouth and the procedures such as daily oral care. Furthermore, the outer rim of the mask is designed to effectively retain oxygen flow without causing rebreathing.

Performance of six types of oxygen delivery devices at varying respiratory rates

The administration of a known concentration of oxygen is an important part of routine care of the sick patient. Many devices are currently available. The actual concentration of oxygen that can be delivered by these devices can be affected by several factors, both from the patient as well as the device itself. Measuring the F(i)o(2) delivered to the lungs in vivo can be both difficult and potentially uncomfortable for the subjects. We constructed a model using a resuscitation manikin, a ventilator and a set of bellows to simulate ventilation. With this model we tested a series of devices - variable performance, fixed performance and high flow - at two fixed tidal volumes. The respiratory rate was increased and its effect on the oxygen concentration assessed. Variable performance systems such as the Hudson mask deliver a significantly reduced oxygen concentration at high respiratory rates. Fixed performance systems delivering 24-40% oxygen deliver appropriate oxygen concentrations across the range of respiratory rates, whereas those delivering 60% show a reduction in performance. High flow systems show no failure of performance at increased respiratory rates.