POCs offer greater freedom and mobility compared to traditional oxygen tanks. These devices typically use a pulse dose delivery system, which releases a short burst of oxygen only when the user inhales, conserving oxygen and extending battery life. Unlike continuous flow systems, pulse dose settings are non-standardized, making it confusing for users to determine the correct flow. Understanding how the setting is determined and monitoring its effectiveness is paramount for proper oxygen delivery and patient safety.
The Medical Basis for Flow Settings
The necessary oxygen flow setting begins with a prescription from a healthcare professional. This prescription is based on a comprehensive evaluation of oxygen needs under various physiological conditions. The goal of this medical assessment is to maintain a safe and effective blood oxygen saturation level, typically targeting 90% or higher during activity.
One of the most common tests used to determine oxygen requirements upon exertion is the six-minute walk test (6MWT). During this evaluation, a patient walks for six minutes while oxygen saturation is continuously monitored with a pulse oximeter. If saturation drops below the target threshold, the provider increases the oxygen flow setting until the level remains stable throughout the activity.
Oxygen needs can also change significantly during sleep, requiring nocturnal oximetry. This test monitors saturation and heart rate overnight to detect episodes of low oxygen levels (nocturnal hypoxemia). The results of these tests—at rest, during exertion, and during sleep—establish the required therapeutic effect. The physician translates this efficacy into an initial setting for the specific portable device.
Translating Settings: Pulse Dose vs. Continuous Flow
Users often confuse the pulse dose setting number on their POC with the familiar liters per minute (LPM) rate of continuous flow oxygen. A setting of “3” on a pulse dose machine does not mean it is delivering 3 LPM of oxygen. Pulse dose delivery is measured in a short burst, or bolus, in milliliters per breath, not as a constant flow over time.
The numbers on a pulse dose POC, typically ranging from 1 to 9, represent a proprietary setting defined by the manufacturer. These settings correspond to the volume of the oxygen bolus delivered per breath or the duration of the flow rate. Since the amount of oxygen is tied to the patient’s breathing rate and the device’s sensor sensitivity, there is no direct, standardized equivalent to a continuous flow LPM rate.
The variability is significant; a setting of “2” on one brand’s POC may deliver a very different amount of total oxygen per minute than on a competing model. This lack of standardization makes switching devices and using the same number setting impossible. Therefore, the physician’s initial prescription must be based on clinical testing with the specific device the patient will use, or a manufacturer equivalence chart must be consulted.
Monitoring Oxygen Saturation During Activity
After a pulse dose setting is prescribed, the most practical way to ensure its adequacy is through self-monitoring with a pulse oximeter. This small, non-invasive device clips onto a finger and measures the arterial oxygen saturation (\(\text{SpO}_2\)) level in the blood. The results provide immediate feedback on whether the prescribed setting meets the body’s oxygen demand during various activities.
The target \(\text{SpO}_2\) for most people on supplemental oxygen is to remain at or above 90%, especially during movement. To monitor this effectively, check your saturation at rest to establish a baseline. Then, check the reading during periods of light exertion, such as walking, light housework, or climbing stairs, as these activities increase oxygen demand.
For situational monitoring, use the pulse oximeter during the first few minutes of a new activity, and again after about five minutes to see if the \(\text{SpO}_2\) level has stabilized. If the reading consistently drops below 90% during activity, the current pulse dose setting is likely insufficient for that level of exertion. If your \(\text{SpO}_2\) consistently drops below the target range, promptly contact your physician to discuss an adjustment to your prescribed setting.