Biomedical subjects

A Mamen

Publications and source records attributed to A Mamen.

3 recordsLinked to original sources

PubMed2002

Examination of the Metamax I and II oxygen analysers during exercise studies in the laboratory.

The performance of the Metamax I and the Metamax II portable analysers for measuring the O2 uptake has been examined during exercise. Healthy subjects ran on the treadmill or bicycled on ergometers while the O2 uptake was measured by the Metamaxes and also by the Douglas bag technique or the Vmax 29 instrument. In the first series of experiments, O2 uptake was measured by each instrument in turn. In later experiments two or more breathing valves were connected in a series, thus enabling measurement of the O2 uptake simultaneously by more than one instrument. The O2 uptake measured by the Metamax analysers rose linearly by the value given by the control methods. However, there were variations of approximately 5% because the relationships differed between subjects. When the data from each subject were examined separately, the error of regression was 0.5-1 micromol s(-1) kg(-1) (2-3%), and the error of regression when relating the O2 uptake to the exercise intensity was similar to that found when using the Douglas bag technique alone. In most cases the lung ventilation reported by the Metamaxes was a few percent less than that given by the control methods, while the fractional extraction of O2 was higher for the Metamaxes. The respiratory exchange ratios (R-value) reported by the Metamaxes were in good agreement with those of the control methods in the range 0.9-1.0 only; for this parameter, the Metamaxes do not seem to be reliable for exercise testing. The O2 uptake and the R-value were also calculated from the raw data reported by the Metamaxes. The calculated values differed somewhat from those reported by the instruments, and the calculated values were more in agreement with those obtained by the Douglas bag technique than those reported by the instrument. This study suggests that the O2 uptake reported by the Metamaxes is precisely measured within subjects but that there are some systematic errors as well as variations between subjects.

Adolescent↗

PubMed2000

Examination of four different instruments for measuring blood lactate concentration.

Information on the performance of different instruments used to measure blood lactate concentration is incomplete. We therefore examined instruments from Yellow Springs Instruments (YSI 23L and YSI 1500) and three cheaper and simpler instruments: Dr. Lange's LP8+, Lactate Pro from Arkray in the KDK corporation and Accusport from Boehringer Mannheim. First, a number of blood samples were analysed by standard enzymatic photofluorometry (our reference method) and, in addition, by one or more of the instruments mentioned above. Second, measurements using two or more identical instruments were compared. Third, since Lactate Pro and Accusport are small (approximately 100 g, pocket-size), battery-driven, instruments that could be used for outdoor testing, the performance of these instruments was examined at simulated altitudes (O2 pressure of <10 kPa) and at temperatures below -20 degrees C, while screening the instruments as much as possible from the cold. Most of the different instruments showed systematically too high or too low values (10-25% deviation). The observed differences between instruments may affect the "blood lactate threshold" by 2-5%. We found different readings between "equal" YSI 1500 instruments, while we could see no difference when comparing the other instruments of the same type. Lactate Pro gave reliable results at both -21+/-1 degrees C and at simulated altitude. Accusport gave reliable results in the cold, but 1.85+/-0.08 mmol L(-1) (mean+/-SD) too high readings at the simulated altitude. Of the three simpler instruments examined, the Lactate Pro was at least as good as the YSI instruments and superior to the other two.

Altitude↗

PubMed1996

LSD-like panic from risperidone in post-LSD visual disorder.

Risperidone, a novel antipsychotic agent, is an antagonist of postsynaptic serotonin-2 and dopamine D2 receptors. In certain individuals, the hallucinogenic drug lysergic acid diethylamide (LSD) is associated with apparently lifelong continuous visual disturbances, characterized in DSM-IV as hallucinogen-persisting perception disorder (HPPD). Because the hallucinogenic mechanism of LSD is known to act in part at postsynaptic serotonin-2 receptors, it is noteworthy that three HPPD patients treated with risperidone reported an exacerbation of LSD-like panic and visual symptoms. We conclude that HPPD may be a relative contraindication for the use of risperidone.

Adult↗