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Peak flow measurement is a quick test to measure air flowing out of the lungs. The measurement is also called the peak expiratory flow rate (PEFR) or the peak expiratory flow (PEF). Peak flow measurement is mostly done by people who have asthma. Peak flow measurement can show the amount and rate of air that can be forcefully breathed out of the lungs. The measurement should be started after a full lung inhalation. During the test, you blow forcefully into the mouthpiece of a device. A peak flow meter (PFM) is used most often. This is a small handheld device made of plastic. A PFM is small and light enough to be used almost anywhere. It’s important to use the same PFM on a regular basis. The readings can vary between brands and types of meters. In some cases, the test is done in a healthcare provider's office or a hospital with a spirometer. This device has a handheld mouth piece that’s attached by cord to a larger electronic machine. An important part of peak flow measurement is noting peak flow zones. Peak flow zones are areas of measurement on a peak flow meter. The goal of the peak flow zones is to show early symptoms of uncontrolled asthma. Peak flow zones are set differently for each person. Your healthcare provider will help determine your peak flow zones. The 3 peak flow zones are noted by color and include:
Why might I need peak flow measurement?Peak flow measurement using a peak flow meter is useful for people with asthma. During an asthma flare-up, the large airways in the lungs slowly begin to narrow. This slows the speed of air moving through the lungs. A peak flow meter can help show the narrowing of the airways well before an asthma attack happens. A peak flow meter can help you determine:
A peak flow meter can help you manage asthma. It can give you and your healthcare provider information about how open the airways are in your lungs. The PFM can detect small changes in the large airways before you start to wheeze. Using a PFM every day will let you know when your peak flows are starting to drop. This allows you to make early changes in your medicine or routine to help keep asthma symptoms from getting worse. The PFM can also identify the reading at which you need to call your healthcare provider or go to the emergency room. Your healthcare provider may not advise you use a PFM unless your asthma is moderate or severe and you are managing it with medicine. PFM can also be used to assess other lung problems, such as:
What are the risks of peak flow measurement?All procedures have some risks. The risks of this procedure may include:
Certain factors may interfere with the accuracy of peak flow measurement, such as:
How do I get ready for peak flow measurement?Your healthcare provider will explain the procedure to you. Ask him or her any questions you have. You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully. Ask questions if anything is not clear. Tell your healthcare provider if you take any medicines. This includes prescriptions, over-the-counter medicines, vitamins, and herbal supplements. Make sure to:
Before starting daily peak flow meter measuring, your healthcare provider may have you follow a detailed schedule over 2 to 3 weeks. This is done to find your “personal best” peak flow measurement. This value will be used as a baseline for your daily measurements. What happens during peak flow measurement?Peak flow measurement is done 1 or more times daily at the same time of day, or whenever you are having early signs of an asthma attack. Or you should use it when directed by your healthcare provider. Use the peak flow meter (PFM) before taking asthma medicine. Your healthcare provider may advise other times when using a PFM is useful. In most cases, peak flow measurement follows this process:
What happens after peak flow measurement?Note which peak flow zone your measurement falls into. Follow the instructions below:
Your healthcare provider may give you more instructions about what to do for each peak flow zone. Chapter 5. Oxygen Therapy Hypoxemia or hypoxia is a medical emergency and should be treated promptly. Failure to initiate oxygen therapy can result in serious harm to the patient. The essence of oxygen therapy is to provide oxygen according to target saturation rate, and to monitor the saturation rate to keep it within target range. The target range (SaO2) for a normal adult is 92 – 98%. For patients with COPD, the target SaO2 range is 88 – 92% (Alberta Health Services, 2015; Kane, et al., 2013; Perry et al., 2014). Although all medications require a prescription, oxygen therapy may be initiated without a physician’s order in emergency situations. Hypoxia is considered an emergency situation. Most hospitals have a protocol in place allowing health care providers to apply oxygen in emergency situations. The health care provider administering oxygen is responsible for monitoring the patient response and keeping the oxygen saturation levels within the target range. The most common reasons for initiating oxygen therapy include acute hypoxemia related to pneumonia, shock, asthma, heart failure, pulmonary embolus, myocardial infarction resulting in hypoxemia, post operative states, pneumonthorax, and abnormalities in the quality and quantity of hemoglobin. There are no contradictions to oxygen therapy if indications for therapy are present (Kane et al., 2013). Hypoxic patients must be assessed for the causes and underlying reasons for their hypoxia. Hypoxia must be managed not only with supplemental oxygen but in conjunction with the interventions outlined in Table 5.3.
Applying and Titrating Oxygen TherapyWhen providing oxygen therapy, remember the following (Kane et al., 2013):
Oxygen is available in hospitals through bulk liquid oxygen systems that dispense oxygen as a gas through outlets in rooms. It can also be provided in cylinders (large or small) for easy transport for patient use while mobile or when moving around the hospital. An oxygen flow meter regulates the flow in litres per minute. Oxygen therapy may be short- or long-term depending on the SaO2 requirements of the patients and underlying diseases processes (Perry et al., 2014). Checklist 41 reviews the steps for applying and titrating oxygen therapy (see Figure 5.2).
Special considerations:
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