Flow-volume loops normal

FIGURE 25-3. Normal flow-volume loop. Flows are measured on the vertical (y) axis, and lung volumes are measured on the horizontal (x) axis. FVC can be read from the tracing as the maximal horizontal deflection. Instantaneous flow (Vmax) at any point in FVC also can be measured directly. FVC = forced vital capacity. 

FIGURE 25-4. A. Flow-volume loop depicting mild obstruction characterized by decrease flow at low lung volumes. B. Moderate airflow obstruction characterized by a more concave curve. C. Variable intrathoracic obstruction in which peak flow is decreased at higher lung volumes with normalization of curve at lower lung volumes. D. Restrictive lung disease with a curve that is decreased in width but with a normal shape. 

FIGURE 7.7 Typical flow-volume loops, (a) Normal flow-volume loop, (b) Flow-volume loop of patient with obstructive lung disease. 

The flow/volume loop plots exhalation (positive flow) upwards on the y-axis and inspiratory flow (negative flow) downwards. Volume is on the x-axis in liters (there is no time component in this plot, so the FEVi cannot be read from it). The time component is much faster at the beginning of exhalation, the peak usually being reached in less than 0.04 s. The maximum flow on a forced manoeuvre is the peak expiratory flow. Flow volume loops usually record flow in liters per second as here, whereas peak flow meters record in liters per minute. A normal expiratory limb has a near linear rise to peak expiratory flow and then a nearly straight line until vital capacity is reached. A reduction of flow below a straight line usually implies small airways obstruction. The normal inspiratory limb encloses about the same area on the plot as the expiratory limb but is semicircular. The inspiratory limb is flattened by reduced-compliance (stiffer) lungs, as seen in pulmonary fibrosis, by diaphragm muscle weakness and upper airways obstruction. 

Recirculating bed media are fed hot into the primary bed zone at a ratio of 50 to 100 times the coal feed rate. Various types of reinjection, nonmechanical valves and seals are used, such as seal pots, L-valves, J-valves, and others. These are simple refractory lined ducts having solids holding volumes that provide a loop seal, and appropriate aeration nozzles that induce and control solids flow. Cyclones are normally used to separate recirculating solids from the over-... 

During plant shutdown periods, where the reactor coolant pumps are stopped, the normal residual heat removal system provides the motive force for the chemical and volume control system purification. Purification flow Ifom the normal residual heat removal system heat exchanger is routed directly through the normal chemical and volume control system purification loop. Boron changes and dissolved gas control are still possible by operating the chemical and volume control system in a semi-closed loop arrangement. 

Provision must be made to introduce into the carrier gas ahead of the analyzing column a gas-phase sample that has been entrapped in a fixed volume loop or tubular section. The fix loop or section shall be so constructed that the total volume, including dead space, shall not normally exceed 0.5 mL at 1 atm. If increased accuracy of the hexanes and heavier portions of the analysis is required, a larger sample size may be used (see Test Method D 2597). The sample volume must be reproducible such that successive runs agree within 1 % on each component. A flowing sample inlet system is acceptable as long as viscosity effects are... 

Hypercalcemia can be a medical emergency. Because loop diuretics reduce Ca2+ reabsorption significantly, they can be quite effective in promoting Ca2+ diuresis. However, loop diuretics alone can cause marked volume contraction. If this occurs, loop diuretics are ineffective (and potentially counterproductive) because Ca2+ reabsorption in the proximal tubule would be enhanced. Thus, saline must be administered simultaneously with loop diuretics if an effective Ca2+ diuresis is to be maintained. The usual approach is to infuse normal saline and furosemide (80-120 mg) intravenously. Once the diuresis begins, the rate of saline infusion can be matched with the urine flow rate to avoid volume depletion. Potassium chloride may be added to the saline infusion as needed. 

Flow injection procedures are very useful for performing trace analyses in highly concentrated salt solutions. Fang and Welz [270] showed that the flow rate of the carrier solution can be significantly lower than the aspiration rate of the nebulizer. This allows even higher sensitivities than with normal sample delivery can be obtained. Despite the small volumes of sample solution, the precision and the detection limits are practically identical with the values obtained with continuous sample nebulization. The volume, the form of the loop (single loop, knotted reactor, etc.) and the type and length of the transfer line between the flow injection system and the nebulizer considerably influence the precision and detection limits that are attainable. 

Normal flow-injection analysis (FIA) involves using a peristaltic pump to aspirate the sample Into the loop of an Injection valve, which also quantizes the aspirated volume, and subsequently Inserting the loop contents into a carrier or reagent stream. 

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