Version May 2024
| I. How to construct a home arm volumeter |
| A. Parts. All parts are made of common polyvinyl chloride (PVC) piping used in plumbing. All parts are unthreaded. (Note: Phrases set in quotation marks in this section indicate the phrase to use when purchasing materials at the hardware store.) |
| one 6-inch (15-cm) internal diameter PVC pipe of approximately 1/4-inch (6-mm) standard thickness (called "6-inch Pipe"); length equal to arm length |
| one 4-inch (10-cm) internal diameter PVC pipe (called "4-inch Pipe"), 9 inches (23 cm) long |
| one asymmetric "Y" PVC all female connector (called "Asymmetric Y connector"; also called "Wye" in some plumbing catalogs), designed to connect two 6-inch and one 4-inch pipes |
| one PVC 45-degree elbow (called "Elbow") with one male and one female connecter end, designed to connect two 4-inch-diameter PVC pipes, also called a "45-degree 4-inch male-female PVC angle" |
| one 6-inch PVC cap (called "6 inch Cap") |
| PVC solvent glue |
| B. Assembly instructions. |
| 1. Arm length |
| Determine arm length by measuring the arm from the inner fold of the armpit (anterior axillary fold; Point A) along the inside (anterior aspect) of the arm to the tip of the middle finger when the hand is outstretched in a taut position (Point B). |
| 2. Cutting and gluing |
| Warning: It is dangerous to cut PVC pipe with a power saw and to handle PVC glue, which emits toxic vapors; these tasks should be left to a properly trained person. |
| Reference for metric equivalents: Conversion factor: 1 inch = 2.5 cm. Approximate equivalents: 1/4 inch = 6 mm; 4 inches = 10 cm; 5 inches = 13 cm; 6 inches = 15 cm; 9 inches = 23 cm. |
| a. Cut the 6-inch pipe to a length equal the length of the arm. |
| b. Cut the 4-inch pipe to a length of 9 inches (23 cm). |
| c. Cut the asymmetric Y-connector. Stand the asymmetric Y-connector with the 4-inch connector end facing down. Measure 5 inches (13 cm) up from the bottom of the 6-inch connector end and mark point A. Mark point B just above the ridge of the 4-inch connector end (Step 1). Cut across the asymmetric Y-connector in a straight line spanning from point A to point B (Step 2). File and sand the newly cut top edge to make a smooth, curved lip (Step 3). |
| d. Glue the 6-inch cap to one end of the 6-inch pipe to seal the bottom of the volumeter. |
| e. Glue the asymmetric Y-connector to the other end of the 6-inch pipe. |
| 3. Fitting |
| Attach the 4-inch pipe to one end of the elbow and attach the elbow to the asymmetric Y-connector. The volumeter's spout is now in place. The spout also serves as a handle to lift, drag, or carry the volumeter. |
| C. Filing, sanding, cleaning, and disinfecting. Clean all parts before assembly. Carefully check the assembled volumeter, inside and out. File and sand any sharp edges or points. Clean and disinfect the volumeter using a bleach solution. Rinse thoroughly with water to remove any trace of bleach. |
| II. How to measure arm volume |
| A. Equipment |
| Home arm volumeter |
| Beverage pitcher (the pitcher does not need to have volume gradations because the water volume is measured by weighing) |
| Digital gram kitchen scale or postal scale (the scale should read up to 5000 grams, be accurate to 1 gram, and have a platform large enough to hold the pitcher. The display must be in grams [not ounces] because water weight in grams is equivalent to water volume in milliliters, which is the only way the water volume can be determined through weighing. The author strongly recommends that patients weigh the water and not use graduated containers, which are too imprecise and yield misleading volumetric readings.) |
| B. Measurement procedure. |
| 1. Weigh the empty pitcher and record its empty weight (Step 1). This will be a constant that you always subtract from the weight of the pitcher of water. |
| 2. Place the volumeter on a level-surfaced floor. To achieve comparable measurements, try to place the volumeter in the same location each time. |
| 3. Prepare a comfortable seat beside the volumeter, for example, a stool or low chair. A closed toilet seat may also be convenient with the volumeter placed beside the toilet. |
| 4. Place the pitcher under the volumeter spout. Under the pitcher, place any type of flat base, such as a plastic food storage container, to raise the pitcher up to the edge of the spout. This base is necessary so that no drops of water splash outside of the pitcher (Step 2). |
| 5. Fill the volumeter with lukewarm water until it overflows into the pitcher. Wait for all air bubbles to settle. Top off the water level with a bit more water and wait for the overflow to completely stop dripping into the pitcher (Step 3). |
| 6. Empty the water out of the pitcher (Step 4). Dry the pitcher with a towel. Return the dry pitcher to its original spot under the spout of the volumeter. |
| 7. You are now ready to measure your arm volume. Sit beside the volumeter. Slowly and gently lower your arm into the volumeter. Water will rush out through the spout into the pitcher. Continue lowering your arm until your middle finger touches the bottom of the volumeter, while keeping your fingers, wrist, and elbow in a fully extended and taut position (Step 5). |
| 8. Hold this position until the water stops dripping into the pitcher. You can best see this by watching when the water in the pitcher becomes still. |
| 9. Remove your arm and dry it with a towel. |
| 10. Place the pitcher filled with the overflow water on the scale (Step 6). |
| 11. Record the gram output showing on the scale. From this number, subtract the weight of the empty pitcher (Step 1). The difference equals the volume in grams of the water in the pitcher. This amount equals the volume in millilitres of your arm. |
| 12. We recommend that you do at least two consecutive measurements, and preferably three (see Helpful Hints). |
| 13. When you have finished measuring, the volumeter can be dragged or lifted by the spout and tipped into the bathtub or shower to empty. |
| III. Helpful hints |
| The most important procedure in measuring arm volume is Procedure 8: holding the arm immobile in the volumeter until the water stops dripping. This may take up to one minute. It is therefore important to be comfortable and relaxed when you take your arm measurement. Your seat should be comfortable. To avoid straining your back, try to bend from the waist and keep your back straight. |
| Measuring in the bathtub: since the floor of the bathtub is not a level surface, it may not be an ideal location for the volumeter. Also, sitting on the side of a bathtub (in a straddle or side-saddle position) is not usually comfortable. |
| We recommend that you take three measurements in a row and calculate the average, in case of an erratic measurement. By comparing three measurements, you can judge your skill at measurement. With practice, your measurements may vary by less than 10 mililiters, which is highly precise. |
| If you discover that the six-inch pipe has been cut too long and your middle finger does not touch bottom before the top of the volumeter hits your armpit, you can use a "landmark," such as a freckle on your upper arm, and stop immersion at that landmark. You can also add a "false bottom" to your volumeter by filling a plastic container with vase gems, marbles, or polished stones and placing the weighted container in the volumeter. |
| To lower costs of making the volumeter, patients can group together to have several made at one time. |
| We recommend that you not modify the design of the home use volumeter. It is the result of trial and error and numerous prototypes over two years. Even a minor design change may change the volume and shape of the water meniscus at the top of the cylinder of water and result in unreliable measurements. |
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