RESUMO
The digital impedance meter is a microprocessor-based instrument able to detect, quantify and identify micro-organisms. The equipment makes use of the bipolar technique of measuring the impedance modulus of six cells containing inoculated culture broth. It performs temperature compensation automatically. Growth curves are stored in memory as time course events and can be displayed on any suitable device.
Assuntos
Condutividade Elétrica , Técnicas Microbiológicas/instrumentação , Processamento de Sinais Assistido por Computador , Calibragem , Desenho de Equipamento , Escherichia coli/crescimento & desenvolvimento , Microcomputadores , Design de SoftwareRESUMO
By means of the bipolar impedance technique, we detected bacterial growth in an inoculated broth as its time course absolute impedance. From it, the impedance change relative to sterile medium was obtained, calculating also its time derivative. The repeatability of the derivative curves (they overlapped within a band better than 3.3%) permitted the identification of a double-hump pattern which, in principle, could be accepted as an indicator of the type of bacteria (Escherichia coli). After six experimental series, the growth curves appeared as sensitive to the initial concentration of bacteria and to the culture time preceding inoculation; they were also dependent on the temperature and on the average basal impedance. Temperature showed a greater effect (one order of magnitude) on the lag-phase of the growth curve than on the stationary-phase. This effect occurs because the impedance growth curves tend to get away from the reference offered by the sterile medium. The best working conditions were obtained for an average basal impedance of 510 ohms under well controlled temperature conditions (variations smaller than or equal to 0.20 degrees C) with wire stainless steel electrodes vertically immersed in the culture broth. This impedance technique appears as inexpensive and easy to automatizing for large number of samples.
Assuntos
Condutividade Elétrica , Escherichia coli/crescimento & desenvolvimento , Temperatura , Humanos , Fatores de TempoRESUMO
In a population of ten young normal male subjects (average height of 174.2 cm +/- 3.8, average weight of 70.2 kg +/- 6.16), which was subjectively classified as mainly ectomorph (slightly biased towards the mesomorph type) a good correlation was found between the transthoracic impedance changes due to normal respiratory movements and tidal volume (average r of 0.963 +/- 0.034) and a mean coefficient b1 of 3.64 ohms/liter +/- 1.82. For equal volume, inspiratory and expiratory movements, on the average, produced impedance changes with no significant difference (p less than 0.55). Attempts to quantitatively correlate the coefficient b1 (ohms/liter) with the anthropometric parameters did not produce any consistent result.
Assuntos
Cardiografia de Impedância , Pletismografia de Impedância , Espirometria/métodos , Constituição Corporal , Humanos , MasculinoRESUMO
In a population of ten young normal male subjects (average height of 174.2 cm +/- 3.8, average weight of 70.2 kg +/- 6.16), which was subjectively classified as mainly ectomorph (slightly biased towards the mesomorph type) a good correlation was found between the transthoracic impedance changes due to normal respiratory movements and tidal volume (average r of 0.963 +/- 0.034) and a mean coefficient b1 of 3.64 ohms/liter +/- 1.82. For equal volume, inspiratory and expiratory movements, on the average, produced impedance changes with no significant difference (p less than 0.55). Attempts to quantitatively correlate the coefficient b1 (ohms/liter) with the anthropometric parameters did not produce any consistent result.
RESUMO
In a population of ten young normal male subjects (average height of 174.2 cm +/- 3.8, average weight of 70.2 kg +/- 6.16), which was subjectively classified as mainly ectomorph (slightly biased towards the mesomorph type) a good correlation was found between the transthoracic impedance changes due to normal respiratory movements and tidal volume (average r of 0.963 +/- 0.034) and a mean coefficient b1 of 3.64 ohms/liter +/- 1.82. For equal volume, inspiratory and expiratory movements, on the average, produced impedance changes with no significant difference (p less than 0.55). Attempts to quantitatively correlate the coefficient b1 (ohms/liter) with the anthropometric parameters did not produce any consistent result.
RESUMO
A high linearity instrument for biological use which permits the measurement of impedance modulus and its variations in the range of 50 to 1,000 ohms is described. It has two outputs (Z and delta Z) which can be connected to an oscilloscope or to any conventional physiological recorder. The deviation from linearity is not greater than 0,06%, with a sensitivity of up to 100 mV/ohm, and an estimated average error better than 1% in absolute value with standard deviation better than 3% and an expected range smaller than +/- 10%. The instrument can stand changes of +/- 10% in the a.c. power supply without showing significant alterations in its behavior. Besides, it has good isolating characteristics in order to prevent undesirable leak currents which are potentially dangerous for the patient. The instrument was tested satisfactorily in human beings and in experimental dogs by recording respiratory movements and cardiac activity.
Assuntos
Cardiografia de Impedância/instrumentação , Frequência Cardíaca , Pletismografia de Impedância/instrumentação , Respiração , Adulto , Animais , Cães , Eletrocardiografia , HumanosRESUMO
A high linearity instrument for biological use which permits the measurement of impedance modulus and its variations in the range of 50 to 1,000 ohms is described. It has two outputs (Z and delta Z) which can be connected to an oscilloscope or to any conventional physiological recorder. The deviation from linearity is not greater than 0,06
, with a sensitivity of up to 100 mV/ohm, and an estimated average error better than 1
in absolute value with standard deviation better than 3
and an expected range smaller than +/- 10
. The instrument can stand changes of +/- 10
in the a.c. power supply without showing significant alterations in its behavior. Besides, it has good isolating characteristics in order to prevent undesirable leak currents which are potentially dangerous for the patient. The instrument was tested satisfactorily in human beings and in experimental dogs by recording respiratory movements and cardiac activity.
RESUMO
A high linearity instrument for biological use which permits the measurement of impedance modulus and its variations in the range of 50 to 1,000 ohms is described. It has two outputs (Z and delta Z) which can be connected to an oscilloscope or to any conventional physiological recorder. The deviation from linearity is not greater than 0,06
, with a sensitivity of up to 100 mV/ohm, and an estimated average error better than 1
in absolute value with standard deviation better than 3
. The instrument can stand changes of +/- 10
in the a.c. power supply without showing significant alterations in its behavior. Besides, it has good isolating characteristics in order to prevent undesirable leak currents which are potentially dangerous for the patient. The instrument was tested satisfactorily in human beings and in experimental dogs by recording respiratory movements and cardiac activity.