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Cameron
Heartometer Company
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Excerpt from: By Alexander S.
Cameron and Alexander W. Cameron HOW TO OPERATE THE HEARTOMETER Before taking blood pressure or making a Heartograph, it is important to learn how to operate the instrument and to understand its mechanism. The standard Heartometer is made for 110 to 115 volts, 60 cycle, alternating current, but the instrument is also made for 25, 40 and 50 cycle alternating current, or for any other voltage and cyclage specified. For direct current, a special converter is necessary. Before connecting the instrument to the electric line, be sure that the current conforms exactly to the voltage and cyclage which is imprinted on the instrument. Connect the cord to the outlet on the back of the cabinet, and the other end to the electric light socket. The instrument is provided with a fuse so if used inadvertently on the wrong current, the instrument will not be damaged. The pilot light at the top center of the door indicates that the instrument is properly connected. The clutch for operating the Heartometer is located at the upper left side of the cabinet, and is used in three positions: 1. All the way out for Blood Pressure Reading. 2. All the way in for graphing. 3. Intermediate for cutting off the current to the instrument. Before making a Heartograph, check the zero setting. The blood pressure pen should be on the inner edge of the heavy blue line. If ever necessary to “Zero” the pen loosen the 2 screws, move the arm to proper position and retighten screws. The door is closed by a magnet, and is opened by a straight pull of knob on the left side of the door, giving access to the drawer containing cord, ink, arm band and accessories. Fill pens with ink furnished with the instrument; red for the heart graph and green for the blood pressure. Be sure that the ink is all the way to the point of the pen and that there are no air bubbles to prevent an even flow of ink. Always keep pens filled above the shoulder and they will write freely. If pens fail to write, remove and wash in hot water – drying them thoroughly before refilling. Care should be taken to avoid bending pen arms and the spring arms that support them. Place graph in position on instrument with the section for patient’s record on the left side of the instrument; centered below the graphing pen. Be sure that the retaining screw holding the chart is tight, otherwise the chart will not rotate. The clutch must be all the way out for blood pressure, and all the way in for heart graphing. The Heartograph chart is easily inserted. It is taken off the instrument by turning the lower and left graph clips, removing the center screw, and pulling downward.
HOW TO MEASURE BLOOD PRESSURE WITH THE HEARTOMETER
With the Heartometer technique, blood pressure readings and graphs are routinely made on the right and left brachial and right and left tibial arteries. In addition to this, it may be desirable to make readings from the radial, popliteal and femoral arteries. The routine generally followed is to make the brachial pressure (Figure 6) readings and graphs, then the tibials (Figure 4). In the case of fat arms and always in the lower extremities, use a 3-inch pressure bandage over the inflation cuff. The patient should be instructed to sit erect, to relax, breathe normally and avoid talking or moving while the graph is being made. Apply band snugly with the center of the compression bag squarely over the artery. It is important that the rubber sac does not bulge out of the compression band. The valve on the inflation system must be completely closed in taking blood pressure, for correct readings cannot be made if pressure is allowed to “bleed off.” Pull the clutch knob (upper left side of cabinet) all the way out. Close the valve and start increasing the pressure, pausing two or three seconds after each inflation and note if there is a regular pulsation of the light caused by the pulse action (usually evident between 60 and 80 mm. of pressure in the brachial arteries). The lowest pressure at which either light flashes regularly is the diastolic or low blood pressure. This is recorded by pushing the clutch knob all the way in, thus starting the motor. Make a line about an inch long. Stop the motor by pulling the clutch knob all the way out. Now inflate quickly until light ceases to flash. This indicates that the artery is collapsed and that the pressure in the cuff is above the systolic level. Deflate 3 to 5 m. at intervals, which can be checked by watching the recession of the blood pressure pen on the graph, pausing 2 or 3 seconds between each deflation until one light flashes rhythmically. The inflation valve must be completely closed at each interval and sufficient time must elapse to permit the impulse to actuate the light. The highest point at which one light pulsates regularly for a count of ten is the systolic or maximum blood pressure. Start the motor by pushing the clutch knob all the way in, and make a line about one inch long to record the systolic pressure. After this, stop the motor by pulling the clutch knob all the way out. A graph of the systolic and diastolic blood pressures is shown on page 8. HOW TO MAKE THE HEART TRACING (HEARTOGRAPH) After recording the diastolic and systolic pressures deflate quickly until the blood pressure pen is 10 or 15 mm. below the diastolic mark. Now increase the pressure ¼ of the pulse pressure field. (This is usually 10 to 20 mm., but varies considerably). In cases where there is extremely large or small pulse pressures, or partial or completely obliterated circulation in the extremities, it may be necessary to make short graphs at different pressures to establish the proper graphing level. Always close the clamp on the tubing when making graphs. Push the clutch knob all the way in to start the motor. Be sure the graphing pen rests on the paper. When revolution of chart is completed, stop the motor by pulling the clutch knob out. The clutch knob should be all the way out before releasing the air from the arm band. If the pressure used in graphing is too low, the graph will lack amplitude and characteristic pattern. If made at too high a pressure, the graph will show a flat base (see examples on page 9). The proper graphing pressure is that point at which you obtain the maximum amplitude with the sharpest top and bottom on the graph. Write in the name, sex, age, pressures, pulse rates and other pertinent facts, and record from which artery the graph was taken. NORMAL GRAPHS Proper graphs are dependent on correct graphing pressure. With normal blood pressure readings, the best graphs are usually obtained at 75 mm. to 90 mm. of pressure (10 to 20 mm. above the diastolic pressure). Until experience has been gained in graphing, short trial graphs (7 ½ to 15 second sections) should be made at various pressures to establish the correct graphing pressure. The graph should be made at the pressure level at which the trial graph most closely resembles the characteristics of the normal heart pattern as shown on pages 16 to 22. The pulse waves are mechanically amplified at the ratio of 150 to 1 on the graph and because of this, irregularities of action are readily discernible. On page 22 there are sections of typically normal graphs of a male, female and a 3 ½ year old child. Note the differences in the amplitude of these three. The rhythm in each is regular and the graphs have similar characteristics. Great care is taken to insure that graphs made by each Heartometer will be identical to those made by every other Heartometer under the same conditions (Figures 7 and 8). A small size arm band should be used for
graphing infants. Because of
the low blood pressure the best graph is usually secured at At times the heart graph pen does not always graph at the same distance from the center of the chart. The position of the pen is dependent on the engaging of the clutch at the beginning, middle or end of the cardiac cycle. This has no real diagnostic significance. To change position of pen on chart, pull clutch out and re-engage. The graph on page 10 is an example of two tracings made at different positions on the paper. The pressures of the popliteal and tibial arteries will usually be 30 to 60% higher than on the brachial. Blood pressure readings on opposing arteries may vary 10% or more at times; however, the graphs should be similar in character. Figure 5 shows the method of applying the inflation bag for graphing the popliteal artery. The bladder is placed on the under side of the upper leg (over the space between the hamstring tendons, known as the popliteal space). It is important that the rubber sac does not bulge out of the wrapping, as may happen with fat patients. In these cases it is necessary to reinforce the arm band with a three inch bandage. An occasional source of trouble in taking the blood pressure and in graphing is due to leaky valves or arm bands. These leaks are evident by the trend of the graph toward the center, as shown on page 11. This is usually due to particles of dust and grit which may be removed by carefully dissembling and cleaning the valve. |
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