African Journal of Respiratory Medicine 5 March 2011 Review Article The peak low meter and its use in clinical practice B O Adeniyi and G E Erhabor Dr B O Adeniyi, Consultant Physician (Respiratory) Federal Medical Centre, Owo, Ondo State, Nigeria; and Professor G E Erhabor, Consultant Chest Physician and Professor of Medicine, Obafemi Awolowo University, Ile-Ife, Nigeria, and President of the Nigerian Thoracic Society. Correspondence to Dr B O Adeniyi. Email: delbis2003@yahoo.com Introduction Bronchial asthma is a disease that causes signiicant morbidity and mortality. It is projected to increase at an alarming rate with an estimated prevalence of 400 million by the year 2025, as contrasted to 300 million at present. Monitoring this disease involves both subjective and objective modalities. The peak low meter is the one of the means of objectively assessing and monitoring the airway function of the patient with bronchial asthma. It has been said that the peak low meter is to the asthmatics, what the sphygmomanometer is to the hy- pertensive. Most clinicians are, however, not skilled in the use of this simple instrument and its in partnership with the asthmatic, to develop a personalised asthma management plan in order to achieve effective control. This article thus seeks to highlight the importance of the peak low meter and its use in clinical practice. A peak low meter is a small hand-held device that measures how fast a person can blow air out of the lungs when there is forceful exhalation, after maximum inhalation. This measurement is called the ‘peak expira- tory low’ (PEF). The peak low meter helps to assess the airlow through the airways and thus help to determine the degree of obstruction along them. The measurement of PEF was pioneered by Dr Martin Wright who produced the irst meter speciically designed to measure this index of lung function. Since the original design was introduced in the late 1950s, and the subse- quent development of a more portable, lower-cost version (the ‘Mini-Wright’ peak low meter), other designs and copies have become available across the world. Brands of electronic peak low meters are also being marketed. Description A peak low meter (Figure 1) consists of a housing which has within it a channel along which a pointer is movable to a distance dependent on the lung function of the pa- tient using the meter. Positioned adjacent to the channel, are two or more indicators which move along an axis parallel with the channel. Each indicator presents to view, two visually distinguishable areas deining a boundary that can be set at a point along the path of the pointer to indicate limit positions relating to lung function. This indicates to the user when to take remedial action. Types of peak low meters There are several brands of peak low meters available which all perform the same function. However, there are two major types: the low-range peak low meter for small children between 4 and 9 years of age, and for adults with severely impaired lung function; and the standard-range peak low meter for older children, teenagers, and adults. It is important that the doctor or healthcare provider prescribes the appropriate device for each individual. Adults have larger airways than children. If given a low-range peak low meter, they will continually have maximum peak low rates even when having severe short- ness of breath. This may jeopardise proper management; they therefore need the much larger standard range. What is a normal peak low rate? Normal peak low rates vary according to age, height, and sex. However, a patient’s normal score should be within 20% of a person of the same age, sex, and height who does not have asthma. There are published standardised normal values which were calculated by comparing asthmatics with a set of age- and sex-matched controls. The ‘normal peak low’ or ‘personal best’ is the highest consistent peak low reading over a 2 –3-week period when the patient does not have asthma symptoms. It serves as a standard against which other readings are meas- ured. By checking the patient’s personal best when he does not have symptoms, changes can be recognised and reduced PEF can be Measuring scale Mouthpiece Cursor Figure 1 A peak low meter