From the Guidelines
Peak flow is a physiological measurement of the largest flow of exhalation that can be achieved from maximal inspiration, expressed in L·min–1, and is used to monitor asthma control by measuring the maximum airflow during a forced exhalation. This measurement is typically taken using a small handheld device called a peak flow meter, and patients with asthma should establish their personal best peak flow value when they're feeling well, which serves as a baseline for comparison 1. The peak expiratory flow should be recorded as the best of three forced expiratory blows immediately after a full inspiration with the patient either standing or sitting.
Key Points to Consider
- Peak flow readings are typically categorized into green (80-100% of personal best), yellow (50-80%), and red zones (below 50%), with each zone indicating different levels of asthma control and guiding appropriate treatment responses.
- For accurate readings, patients should stand up straight, take a deep breath, form a tight seal around the mouthpiece, and blow out as hard and fast as possible.
- Measurements should ideally be taken at the same time each day, typically in the morning and evening, to track patterns and identify triggers that may worsen asthma symptoms.
- The measurement works by quantifying the function of larger airways, making it particularly useful for conditions like asthma where airway constriction occurs, as supported by the european respiratory society clinical practice guidelines for the diagnosis of asthma in children aged 5-16 years 1.
Clinical Application
In clinical practice, peak flow measurement is a valuable tool for diagnosing and managing asthma, as it provides a simple and non-invasive way to assess lung function and monitor treatment response. According to the european position paper on rhinosinusitis and nasal polyps 2020, a 20% increase and absolute improvement of 60l/min in peak flow after administration of a bronchodilator is suggestive of asthma 1. Therefore, peak flow measurement should be a routine part of asthma management, and patients should be educated on how to use a peak flow meter correctly and interpret their results.
From the FDA Drug Label
The maximum albuterol plasma level at 0. 5 hours was 2.1 ng/mL (range, 1.4 to 3. 2 ng/mL). There was a significant dose-related response in FEV1 (forced expiratory volume in one second) and peak flow rate. Published reports of trials in asthmatic children aged 3 years or older have demonstrated significant improvement in either FEV1 or PEFR within 2 to 20 minutes following a single dose of albuterol inhalation solution
Peak flow refers to the peak flow rate or PEFR (Peak Expiratory Flow Rate), which is a measure of how fast a person can breathe out air after a maximum inhalation. In the context of this drug, an increase in peak flow rate indicates an improvement in pulmonary function. 2
From the Research
Definition of Peak Flow
- Peak expiratory flow rate (PEFR) is an important test in the diagnosis and monitoring of respiratory conditions, especially asthma 3.
- Peak expiratory flow (PEF) can be defined as the maximum flow at the mouth achieved during an expiration, delivered with maximum force starting from the level of maximum lung inflation 4.
- PEFR measures the speed at which air is forcefully exhaled from full inspiration, expressed in litres per minute (L/min) 3.
Measurement of Peak Flow
- PEFR is a simple-to-obtain measure that records the maximal flow rate of air that can be achieved in one forceful expiration following a full inspiration 3.
- The procedure for measuring PEFR is simple to teach, but it is necessary to use the correct technique to achieve accurate results 3.
- For the purpose of standardization, it is recommended that forced expiration is initiated with open glottis and immediately after a maximal inspiration, with the position of the head in a neutral position 4.
Clinical Significance of Peak Flow
- Measuring the peak expiratory flow rate is an inexpensive, straightforward and useful clinical investigation that enables fluctuations in the patient's respiratory effort to be monitored over time 5.
- The peak expiratory flow rate is used for the diagnosis, monitoring and assessment of the severity of respiratory compromise, particularly in patients with asthma 5.
- Peak expiratory flow rates can be used to evaluate the effect of treatments, such as inhaled salmeterol and albuterol, in patients with asthma 6, 7.