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Biomedical subjects

P T Meriläinen

Publications and source records attributed to P T Meriläinen.

6 recordsLinked to original sources
PubMed2000

Accuracy of an indirect calorimeter for mechanically ventilated infants and children: the influence of low rates of gas exchange and varying FIO2.

OBJECTIVE: To test the accuracy and validity of the Deltatrac II MBM-200 metabolic monitor for use in mechanically ventilated infants and children in the pediatric intensive care unit. DESIGN: Laboratory validation of an indirect calorimeter with a ventilated lung model. The influence of low tidal volumes and low levels of oxygen consumption (V(O2)) and carbon dioxide production (V(CO2)) in combination with different levels of inspired oxygen concentrations (F(IO2)) was investigated. SETTING: University research laboratory. SUBJECTS: Low tidal volumes were provided with two intermittent flow types of ventilators, a Servo 300 and a Servo 900C. INTERVENTIONS: A butane flame with a V(O2) approximating 20 mL/min and 40 mL/min was ventilated. To investigate the effect of different levels of F(IO2) on the accuracy of V(O2), V(CO2), and respiratory quotient (RQ), measurements were performed at F(IO2) target values of 0.25, 0.40, and 0.60. MEASUREMENTS AND MAIN RESULTS: No significant differences were found between the ventilators regarding V(O2), V(CO2), and RQ measurements. The mean deviation of V(O2) increased significantly with increasing F(IO2) to -7.98% with a V(O2) of 21.0 mL/min and to -8.46% with a V(O2) of 38.9 mL/min (F(IO2), 0.558) with a variability (2 SD) of +/- 4.86% and +/- 6.82%, respectively. The mean deviation and variability of V(CO2) in all tests remained within 8%. The mean deviation of RQ increased significantly with increasing F(IO2) to 5.5% with a V(O2) of 21.0 mL/min and to 5.69% with a V(O2) of 38.9 mL/min (F(IO2), 0.558) with a variability (2 SD) of +/- 5.62% and +/- 5.76%, respectively. The minute to minute delivered F(IO2) fluctuated significantly when increasing the level of F(IO2). CONCLUSIONS: The Deltatrac II MBM-200 metabolic monitor appears accurate for low levels of V(O2) and V(CO2) during mechanical ventilation with F(IO2) levels up to 0.390. With increasing F(IO2) to 0.558, the increase in deviation of V(O2) for single measurements can be of clinical relevance for mechanically ventilated infants and children. The increased fluctuation of delivered F(IO2) on higher levels of F(IO2) is likely the cause of the inaccuracy.

Calorimetry, Indirect↗
PubMed1990

A differential paramagnetic sensor for breath-by-breath oximetry.

The operating principles of a fast paramagnetic oxygen sensor are described in detail. Some historical background of the paramagnetic effect in oxygen measurement is given as well. This sensor measures the difference between oxygen partial pressures in two gases as an alternating pressure signal being generated by the interaction of oxygen molecules with a switched magnetic field. Factors affecting the ideal performance of the sensor are analyzed. The main sources of interference are external pressure and vibration, and asymmetry in the transfer of the pressure signal to the microphone. Finally, the advantages of clinical breath-by-breath oximetry are briefly discussed.

Biosensing Techniques↗
PubMed1988

A fast differential paramagnetic O2-sensor.

A differential oxygen sensor using the paramagnetic principle in a pneumatic bridge configuration has been constructed and tested. The signal being picked up with a differential pressure transducer is generated in a measuring cell with a strong magnetic field being switched on and off with a frequency of 110 Hz. The output signal is a DC-voltage proportional to the O2 concentration difference between the two gases to be measured. A response time of 130 ms has been obtained. A special emphasis on the mechanical design was put to minimize the internal magneto-mechanical noise and to attenuate the external pressure and vibration interference. To eliminate the relatively strong temperature dependence of the paramagnetic effect a compensation circuit was designed as an integral part of the sensor. In performance investigations linearity, stability, noise, humidity and pressure effects as well as sensitivity for other gases were studied.

Electron Spin Resonance Spectroscopy↗
PubMed1987

Metabolic monitor.

The purpose of this review is to provide information about the technical solutions behind the Datex Deltatrac Metabolic Monitor. Deltatrac measures oxygen consumption (VO2), carbon dioxide production (VCO2) and calculates from those respiratory quotient (RQ = VCO2/VO2) and energy expenditure (EE). Deltatrac can monitor both mechanically ventilated and spontaneously breathing patients. In Deltatrac carbon dioxide is measured with conventional infrared technique but both in oxygen and flow measurement novel innovative methods have been used. A fast differential paramagnetic O2 sensor as well as the gas dilution system to measure flow have been developed specially for this application.

Carbon Dioxide↗