An oxygen flow meter is a specialized device used to precisely regulate and measure the amount of oxygen a person receives during therapy. This instrument ensures that the oxygen supply, whether from a tank or a concentrator, is delivered at the exact rate prescribed by a healthcare provider. Its primary purpose is to maintain the correct dosage, measured in Liters Per Minute (LPM). Understanding how to read and set this device is an important step for anyone managing home oxygen delivery.
Key Components of the Oxygen Flow Meter
The most common type of flow meter uses a mechanism known as a Thorpe tube, which is a transparent, vertically-mounted tube typically made of plastic or glass. This tube is tapered, meaning its diameter gradually widens from the bottom to the top. Inside the tube, a small, free-moving indicator, often a spherical ball or a bobbin, floats within the flow of oxygen gas.
The gas enters the bottom of the tube, creating an upward force that lifts the indicator against the pull of gravity. As the flow rate increases, the ball rises higher in the tapered tube, allowing more space for the gas to pass. The side of the tube features a calibrated scale with clear markings that correspond to the flow rate in Liters Per Minute.
Step-by-Step Guide to Reading the Flow Rate
Accurately determining the flow rate requires careful observation of the floating indicator against the calibrated scale. For meters that use a spherical ball, the flow rate is read at the precise center of the ball, not the top or the bottom edge. You should align your eye horizontally with the middle of the ball to ensure the most accurate reading against the LPM markings.
The scale typically has lines indicating whole liters per minute, and sometimes smaller hash marks for half-liter increments. If the center of the ball rests directly on the line labeled “2,” the flow rate is two liters per minute. It is important that the flow meter remains perfectly upright during operation, because tilting the device will cause the ball to rest against the side of the tube, resulting in an incorrect reading.
Setting and Adjusting the Oxygen Flow
Setting the flow meter to the prescribed rate is accomplished by turning the flow control knob, which is typically located at the bottom of the meter. This knob acts as a needle valve, controlling the amount of oxygen gas entering the Thorpe tube. Turning the knob counterclockwise generally increases the gas flow, causing the indicator ball to rise in the tube.
Conversely, rotating the knob clockwise reduces the flow, making the ball descend. Adjustments should be made slowly and deliberately, allowing the indicator ball a moment to settle in its new position after each turn. Once the center of the ball aligns perfectly with the line corresponding to the prescribed LPM rate, the adjustment is complete. Never increase the flow rate beyond the prescribed level without explicit medical direction.
Common Issues and Troubleshooting
One common issue is the flow ball not moving, which can indicate that the oxygen source is off or the tubing is blocked. Check that the oxygen supply cylinder or concentrator is active and that the tubing leading to the patient is free of kinks or obstructions. If you hear a distinct hissing sound near the meter, this suggests a leak at one of the connections, such as where the tubing attaches to the meter’s outlet.
To fix a leak, gently ensure all connections are firmly secured, paying close attention to the small plastic connector, sometimes called the “Christmas tree” nipple. If the ball rises but does not reach the desired setting, the oxygen source pressure may be low, or the concentrator may require maintenance. If these simple checks do not resolve the issue, contact your equipment supplier or healthcare provider for professional assistance.