A peak flow, also called a peak flowmeter, is a portable, lightweight, space-saving system that measures peak expiratory flow, or PEF. It allows the patient to monitor his respiratory function. By controlling his breath with peak flow, the patient can then detect any deterioration in his DEP and possibly anticipate an asthma attack.

The peak-flow, also called a peak flowmeter, is a small, portable device for personal use that measures peak expiratory flow, or PEF, also known as “Peak Expiratory Flow”. The EPD is the moment when the breath is most powerful during an exhalation. It constitutes an important marker in the monitoring of asthma.

As the user breathes into the mouthpiece of the housing, the cursor will stop at a number on a graduated scale when the breath speed is at its maximum, thus indicating the “peak maximum flow”. The device then returns this value in liters per minute: it is this result which can be read directly on the measurement scale.

By taking measurements regularly, the user can observe the evolution of his DEP. Expiration improves as PEF increases, is stable when PEF is constant, or deteriorates as PEF decreases.

Used from the age of 5-6 years, peak flow allows:

• measure the degree of obstruction of the bronchi (COPD, asthma);
• assess the severity of asthma;
• anticipate an asthma attack;
• monitoring the course of the disease and these symptoms;
• take regular measurements during the first few weeks after being diagnosed with asthma;
• to evaluate the effectiveness of a bronchodilator administered during an attack;
• estimate the effectiveness of a change in treatment;
• identify new symptoms and signs.

The result obtained is compared to a reference DEP – determined by means of a scale which in adults is a function of age, height and sex, and in those under 18 is only a function of size – and classified into three colored areas indicating the possible severity of the respiratory capacity:

• green zone: the DEP obtained is between 100 and 80% of the reference DEP: the respiratory functions are normal or corrected;
• orange zone: the PED obtained is between 80 and 60% of the reference PED: this is an alert, the patient must quickly consult his doctor to initiate or adjust his treatment;
• red zone: the PED obtained is less than 60% of the reference PED: the patient must immediately call his doctor to start treatment for the crisis.

On medical prescription, the frequency of checks carried out with peak flow must be decided with the attending physician and adapted according to the situation. As a general rule, it is recommended to take 2 measurements per day, in the morning upon waking up and in the evening before going to bed.

HOW TO USE

• place a plastic tip on the device;
• check that the cursor is correctly positioned at the bottom of the graduated scale;
• stand up, or sit, with your chest straight, in order to free the thorax;
• hold the device horizontally;
• breathe as much as possible, inflating the chest as much as possible with the mouth open and chin raised until it reaches full lung capacity;
• blocking breathing, deflated cheeks;
• immediately insert the mouthpiece of the device into your mouth;
• close your lips around the mouthpiece and stop your nose to prevent leaks;
• achieve maximum forced voluntary expiration: blow in one blow, as hard and as quickly as possible;
• repeat the operation 2 times (3 measures in total) returning to the initial position;
• rest between each measurement;
• discard the plastic tip;
• document the highest value of the three in a logbook or tracking sheet;
• transcribe its position during these measurements;
• also note all daily events (coughing, wheezing, waking up at night, oppression, emotions, sport, etc.) as well as the drugs consumed.

Precautions for use

• do not use peak flow like a blowpipe, with your tongue in the mouthpiece;
• do not hinder the cursor with your fingers;
• do not block the air outlets;
• always use the same peak flow, in order to have reliable and comparable values;
• plastic tips are disposable;
• wipe the device before use;
• clean the device after each use with a disinfectant and / or hot soapy water;
• do not use boiling water;
• do not bring it to a boil;
• rinse it gently with clean water;
• evacuate the drops by shaking it lightly;
• let it air dry;
• make sure it is completely dry before using it;
• strictly reserved for individual use, peak flow is never ready, just like a toothbrush.

There are various models on the market, with measuring ranges ranging from:

• from 60 to 800 L / min (Adult size);
• from 40 to 400 L / min (Format usable by children from 5/6 years old).

However, some peak flows may be suitable for both adults and children.

Peak flow is usually provided with disposable plastic tips, which allow hygienic use, as well as a sheet for recording results. Peak flows must also comply with standard NF EN 13826 relating to spirometers allowing the measurement of the expiratory peak flow. The device must also be guaranteed for 2 years by the manufacturer under normal conditions of use from the date of invoice.

Green, orange and red notches, positioned according to the patient’s best values, can immediately know the state of his breath. The peak flow can also have a handle to avoid hindering the cursor.