Match the words with their antonyms.

9. Choose the correct variant:

1. The conversion is achieved by using oscillators whose frequencies… on a fixed internal capacitor and the inductance of each coil.

2. Two general methods… for calibration of the respiratory inductive plethysmograph.

3. A number of parameters… with the accuracy of the approximation of the volume integral with a Riemann sum.

4. Furthermore, the selection of the position of the first section … important.

5. While the interval of integration … mostly well defined in theoretical analyses,

for in vivo measurements, the first section … often less well defined.

6. The principle of the indicator dilution theory … gas or fluid volume was originally developed by Stewart and Hamilton.

7. The advantage of water displacement volumetry … the possibility for direct measurement of objects with an irregular form.

The calculation of the volume of the leg is performed … the leg into disks of thickness.

Read and translate the text.

TEXT B

Air plethysmography uses the relation between the volume change of a gas in a closed system and the corresponding pressure and temperature. The relation between pressure and volume is described by Boyle’s law which can be written as:

P_iV_i = P_fV_f

with P_i and V_i the initial pressure and volume, respectively, and P_f and V_f the final pressure and volume, measured at constant temperature: the displacement of the fluid or the compressing of the air is a direct measure of the blood flow or original volume. The air plethysmograph uses the change in pressure that occurs in a cuff wrapped around the segment of interest due to the change in volume. By inflating the cuff to about 60 mm Hg, the arterial in-flow causes small increases in pressure. These small changes in pressure over the cardiac cycle can be monitored. The measurement of blood flow is achieved by comparing the pressure changes to changes caused by removing known amounts of air from the system. The second measurement uses volume changes at various pressures between systolic and diastolic pressures, and the peak deflection is compared with the deflection caused by removal of known amounts of air from the system. In segmental plethysmography, two cuffs are used to measure the volume changes in a segment of a limb. Venous occlusion is established by the first cuff, while the second is inflated to a pressure that will exclude blood flow from those parts that should not be included in the measurement.

The technique can also be used for whole-body plethysmography, a common technique used to measure residual volume, functional residual capacity (FRC), and total lung volume, the parameters usually determined during pulmonary function testing. In body plethysmography, the patient sits inside an airtight box, and inhales or exhales to a particular volume (usually the functional residual capacity, the volume that remains after a normal exhalation).

The increase in chest volume slightly reduces the air volume of the box, thereby increasing the pressure. First, the change in volume of the chest is quantified using Boyle’s law with the initial pressure and volume of the box, and the pressure in the box after expansion.

The change in volume of the box is equal to the change in volume of the chest. A second measurement using the initial volume of the chest (unknown) and the initial pressure at the mouth, and the inspiratory volume (the unknown chest volume and the change in volume obtained in the first measurement) together with the pressure at the mouth during the inspiratory effort. By solving Boyle’s law for the unknown volume, the original volume of gas present in the lungs when the shutter was closed is obtained, which is normally the volume present at the end of a normal exhalation.

Date: 2016-04-22; view: 953