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:
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Green . This means “go.” The green zone is 80% to 100% of your highest peak flow reading, or personal best. This is the zone you should be in every day. When your measurements are in this zone, air is moving well through the large airways in your lungs. It means that you can do your usual activities and go to sleep without trouble.
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Yellow. This means “caution” or “slow down.” The yellow zone is 50% to 80% of your personal best. Measurements in this zone are a sign that your large airways are starting to narrow. You may start to have mild symptoms, such as coughing, feeling tired, feeling short of breath, or feeling like your chest is tightening. These symptoms may keep you from your usual activities or from sleeping well.
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Red. This means “stop.” The red zone is less than 50% of your personal best. Readings in this zone mean you have severe narrowing of your large airways. This is a medical emergency. You should get help right away. You may be coughing, very short of breath, wheezing while breathing in and out, or having retractions (the muscles between the ribs are working hard to help you breathe). You may also have trouble walking and talking.
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:
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When to get emergency medical care
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How well an asthma treatment plan is working
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When to stop or add medicine as directed by your healthcare provider
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What triggers an asthma attack, such as exercise
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:
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Emphysema. This is a chronic lung condition that affects the smallest air sacks in the lungs (alveoli).
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Chronic bronchitis. This is long-term inflammation of the bronchi. It creates excess mucous and a chronic cough.
What are the risks of peak flow measurement?
All procedures have some risks. The risks of this procedure may include:
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Having to take in deep breaths may make you feel dizzy or short of breath
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It may trigger coughing or wheezing
Certain factors may interfere with the accuracy of peak flow measurement, such as:
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Not breathing in deeply enough to start the test
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Not breathing out forcefully enough to show your true level of dysfunction
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Coughing during the test
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Poor seal around the mouthpiece while performing the procedure
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A dirty meter
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Blocking the mouthpiece with your tongue
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Use of medicines that open the airways (bronchodilators)
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Use of a different type or brand of peak flow meter, as measurements may vary among brands and types of meters
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:
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Not eat a heavy meal before the procedure, if instructed by your healthcare provider
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Follow any other instructions your healthcare provider gives you
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:
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Before each use, make sure the sliding pointer on the peak flow meter is reset to the 0 mark.
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Hold the PFM by the handle.
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Stand up straight.
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Remove chewing gum, candy, or food from your mouth.
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Take a deep breath and put the mouthpiece in your mouth. Seal your lips and teeth tightly around the mouthpiece.
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Blow out as hard and as fast as you can. A “fast blast” is better than a “slow blow.”
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Note the number where the sliding pointer has stopped on the scale.
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Reset the pointer to 0.
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Repeat this 3 times. The 3 readings should be close together. If not, adjust your technique.
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If you cough during a measurement, repeat the measurement.
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Record only the highest of the 3 readings on a graph or in a notebook. Do not average the numbers together. The highest number is called your peak flow or personal best.
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Use the peak flow meter once a day, or as directed by your healthcare provider. Measure peak flows about the same time each day. A good time might be when you first wake up, or at bedtime.
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Clean and care for your meter as instructed.
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If you use a new peak flow meter, you will need to find your new personal best value on the new meter.
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Your healthcare provider may give you other instructions as needed.
What happens after peak flow measurement?
Note which peak flow zone your measurement falls into. Follow the instructions below:
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Green . This means “go.” You should continue to follow your asthma plan as directed by your healthcare provider.
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Yellow. This means “caution” or “slow down.” You should tell your healthcare provider at this time. He or she may tell you to increase or change your medicines. He or she may give you other instructions to help keep your symptoms from getting worse.
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Red. This means “stop.” This is a medical emergency. You should get help right away. Take your rescue medicine and call your healthcare provider or go to an emergency room.
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.
| Interventions |
Additional Information |
| Raise the head of the bed | Raising the head of the bed promotes effective breathing and diaphragmatic descent, maximizes inhalation, and decreases the work of breathing. Positioning enhances airway patency in all patients. A Fowler’s or semi-Fowler’s position promotes a patient’s chest expansion with the least amount of effort. Patients with COPD who are short of breath may gain relief by sitting with their back against a chair and rolling their head and shoulders forward or leaning over a bedside table while in bed.
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| Deep breathing and coughing techniques | Deep breathing and coughing techniques help patients effectively clear their airway while maintaining their oxygen levels. Teach patients “controlled coughing” by having them take a deep breath in and cough deeply with the mouth slightly open. If they have difficulty coughing, teach the huffing technique. This involves taking a medium breath and then making a sound like “ha” to push the air out fast with the mouth slightly open. This is done three or four times, and then they are instructed to cough. If secretions are thick and tenacious, the patient may be dehydrated and require additional fluids (if medical condition does not contraindicate additional fluids). |
| Oxygen therapy and equipment | If patient is already on supplemental oxygen, ensure equipment is turned on and set at the required flow rate and is connected to an oxygen supply source. If a portable tank is being used, check the oxygen level in the tank. Ensure the connecting oxygen tubing is not kinked, which could obstruct the flow of oxygen. Feel for the flow of oxygen from the exit ports on the oxygen equipment. In hospitals where medical air and oxygen are used, ensure patient is connected to the oxygen flow port.
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| Assess need for bronchodilators | Pharmacological management is essential for patients with respiratory disease. Medications such as bronchodilators effectively relax smooth muscles and open airways in certain disease processes such as COPD. Glucocorticoids relieve inflammation and also assist in opening air passages. Mucolytics and adequate hydration decrease the thickness of pulmonary secretions so that they can be expectorated more easily.
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| Oral suctioning | Some patients may have a weakened cough that inhibits their ability to clear secretions from the mouth and throat. Patients with muscle disorders or who have experienced a cerebral vascular accident (CVA) are at risk for aspiration related to ineffective cough reflex, which could lead to hypoxia. Provide oral suction if patient is unable to clear secretions, foreign debris, or mucous from the mouth and pharynx. See Checklist 42 for further directions.
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| Pain relief | Provide adequate pain relief. Pain is known to increase the metabolic demands on the body, which in turn increases the need for more oxygen supply. |
| Devices to enhance secretion clearance | Many devices assist with secretion clearance, such as vests that inflate with large volumes of air and vibrate the chest wall, and handheld devices that help provide positive expiratory pressure to prevent airway collapse in exhalation. Usefulness of these therapies is decided based on the individual patient’s situation and the preference of both the patient and care provider. |
| Frequent rests in between activities | Patients experiencing hypoxia often feel short of breath (SOB) and fatigue easily. Allow patient to rest frequently, and space out interventions to decrease oxygen demand in patients whose reserves are likely limited. Has the patient just returned from a walk down the hall or to the bathroom?
Assess for underlying causes of the hypoxia. Is the potential problem respiratory or cardiovascular? What underlying respiratory or cardiovascular conditions exist? Complete respiratory and cardiovascular assessments may reveal potential abnormalities in these systems. |
| Obstructive sleep apnea | Patients with obstructive sleep apnea (OSA) may be unable to maintain a patent airway. In OSA, nasopharyngeal abnormalities that cause narrowing of the upper airway produce repetitive airway obstruction during sleep, with the potential for periods of apnea and hypoxemia. Pressure can be delivered during the inspiratory and expiratory phases of the respiratory cycle by using a mask to maintain airway patency during sleep. The process requires consideration of each individual’s needs in order to to obtain compliance. |
| Anxiety and depression | The most common co-morbidities of COPD are anxiety and depression. Anxiety is related to chronic shortness of breath and an inability to breathe effectively. Anxiety and depression are chronically undertreated and may be relieved with breathing retraining, counselling, relaxation techniques, or anti-anxiety medications if appropriate. |
| Data source: Cigna & Turner-Cigna, 2005; Kane et al., 2013; Maurer et al., 2008; Perry et al., 2007; Perry et al., 2014; Shackell & Gillespie, 2009 |
Applying and Titrating Oxygen Therapy
When providing oxygen therapy, remember the following (Kane et al., 2013):
- Initiate oxygen according to hospital protocols when patients with respiratory or cardiovascular conditions warrant its use.
- Always assess for underlying respiratory diseases. Patients with COPD are at risk for acute hypoventilation and carbon dioxide retention. Elevated CO2 levels increase risk for respiratory failure or hyperventilation. With COPD patients, always check the physician orders for the required amount of oxygen and acceptable SaO2 range.
- Regardless of underlying conditions, your first priority should be to prevent or treat hypoxia. Never withhold oxygen for COPD patients while waiting for additional medical interventions (Alberta Health Services, 2015; British Thoracic Society, 2008).
- Check all equipment for safety and function at least once per shift. Check oxygen equipment more frequently if using a high-flow system, which requires higher oxygen concentration.
- Avoid interruption of oxygen therapy during patient transport.
- When patient has a tracheostomy or a high-flow oxygen system and is being transported out of your care, contact respiratory therapy for assistance.
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).
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| 1. Complete respiratory assessment for hypoxia. SaO2 should be greater than 92% unless otherwise stated by the physician. The goal is to use the least amount of oxygen to maintain levels between 92% and 98%. | Assess need for O2: check SaO2 level with a pulse oximetry device.
Assess for underlying medical conditions or alternate causes of hypoxia (cardiovascular). |
| 2. If a patient requires oxygen therapy, choose an oxygen delivery system based on your patient’s requirements. | Oxygen is initially started at a low concentration (2 L/min) using nasal prongs. Then the flow is titrated up to maintain oxygen saturation of 92% or greater.
Selection of delivery system is based on the level of oxygen support required (controlled or non-controlled), the severity of hypoxia, and the disease process. Other factors include age, presence of underlying disease (COPD), level of health, presence of an artificial airway, and environment (home or hospital). Significant decreases to O2 saturation levels or large increases to maintain O2 saturation should be reported promptly to responsible health care provider. |
| 3. Once oxygen is applied, reassess your patient in 5 minutes to determine the effects on the body. | Hypoxia should be reduced or prevented. O2 levels should be between 92% and 98%.
Assess vital signs, respiratory and cardiovascular systems, and level of consciousness. Assess and implement additional treatments for hypoxia if appropriate. Reassess your patient if signs and symptoms of hypoxia return. |
| 4. If required, adjust O2 levels. | Changes in O2 percentages should be in 5% to 10% increments.
Patients should be reassessed (respiratory assessment including O2 saturations) after 5 minutes following any changes to oxygenation levels. Changes in litre flow should be in 1 to 2 L increments. Consider changing O2 delivery device if O2 saturation levels are not maintained in target range. Slow, laboured breathing is a sign of respiratory failure. |
| 5. If hypoxia continues, contact respiratory therapist or physician for further orders according to agency protocol. | Patient may require further interventions from the respiratory therapist or most responsible health care provider.
Signs and symptoms of respiratory deterioration include increased respiratory rate, increased requirement of supplemental oxygen, inability to maintain target saturation level, drowsiness, decrease in level of consciousness, headache, or tremors. |
| Data source: British Thoracic Society, 2008; Perry et al., 2014 |
- The underlying condition causing hypoxia must be treated to manage and improve patient outcomes. For example, if hypoxia is caused by pneumonia, additional treatment for hypoxia may include antibiotics, increased fluid intake, oral suctioning, position changes, and deep breathing and coughing exercises.
- If a patient has COPD, check physician order for the amount of required oxygen and the expected saturation level. In general, COPD patients receive 1 to 2 L/min (Kane et al., 2013).
- Once oxygen saturation levels are within normal range, perform a respiratory assessment every two to four hours to monitor need for supplemental oxygen.
- When using oxygen therapy, assess the patient’s skin where the oxygen device comes into contact with the patient. The nose, chin, and ears may have skin breakdown due to the irritation of the tubing on the skin. Oxygen therapy tends to cause drying effects to the nares and mouth. To prevent the drying effect, consider increasing fluid intake (if not contraindicated). Perform frequent mouth care and apply humidification if the patient is receiving more than 4 L/min (Perry et al., 2014).
- A patient is admitted with COPD and pneumonia and has an oxygen saturation of 88% on 1 L/min of oxygen. Is this an appropriate oxygenation level for a patient with COPD? Why?
- A patient with no underlying respiratory disease is hypoxic with an oxygen saturation level of 91% on room air. What are four additional interventions that may help improve oxygen saturation levels without applying oxygen therapy?