Non-invasive calibration method for pulse oximeters

In case of a healthy subject the normal SpO2 value is 97 ± 2% on see level. Modern, finger probe based pulse oximeters are measuring the SpO2 level with 1-2% error. The dispersion between subjects can reach 4%, thus such accuracy is not really demanded by the majority of clinicians. Moreover, in case of fetal pulse oximetry 5% measuring error is accepted. Considering these factors we investigated the feasibility of a non-invasive calibration method with a self-developed pulse oximeter. This method is carried out without blood sampling. Pulse oximeters are measuring the R rate, which is proportional to the SpO2 value. Calibrating an oximeter means finding the function between the R and SpO2. A calibrated pulse oximeter was used as reference. In the case of every subject 15 minutes long measurements were performed. The reference device and our oximeter were attached to the subject at the same time, while artificial air with 14% oxygen content was inhaled by the subject for ten minutes. The SpO2 was measured by the reference oximeter and the R rate by our oximeter. Based on 511 measured data pairs the relationship was determined between 86-100%. The relationship was estimated by linear regression. Although the original relation is non-linear, linear estimation can be used in this small range of SpO2 with good accuracy. The average error of the calibrated device is 2.76%, which is appropriate in medical practice. This method is easier and cheaper as the invasive calibration, but the calibrated device will have slightly bigger measuring error

Theoretical investigation into exhaust gas energetic utilisation

Sustainable development is a kind of development where the pace of technical development, the satiation of increasing supply and the raw materials and resources of the Earth are poised so that the rate of living and the opportunities of the future generations should not decline. For this reason, transportation systems must be developed and the effectiveness of transportation service must be increased while environmental pollution must be decreased or prevented. Vehicles are burning fuels inefficiently. There are two options of decreasing environmental impacts – one is to reduce fuel consumption while another is to do it in a more acceptable way increasing efficiency. There is justifiable demand put forward by the society to moderate environmental impacts caused by road transportation. This article deals with modelling the energetic utilisation of exhaust gas. First published online: 10 Feb 201