This article was first published in PrimaryCare Today on August 2011
Forms of spirometers were used long before the concept of 'science' when such things were the realm of philosophers . As early as around 150 A.D. Greek philosopher Claudius Galen, a physician, was recorded as experimenting on human ventilation by getting a child to breathe in and out of a bladder.
In 1681, Giovanni Alfonso Borellii measured the volume of air inspired by sucking a liquid up a tube. He had the sense to block off the nostrils - recommended for spirometry today, but we still often see inaccuracy because a disposable noseclip has not been used.
It is generally agreed that the father of spirometry was John Hutchinson, a London surgeon. He presented a paper in 1846 to the Royal Medical and Chirurgical Society of London, on the Capacity of the Lungs, and on the Respiratory Functions, with a view to establishing a precise and easy method of detecting disease by the spirometer. John Hutchinson made a spirometer using an inverted bell sealed by water, much like a small version of a town gasometer. He measured the lungs of over two thousand people and coined the term 'vital capacity' (VC) i.e. the capacity to live. He recognized that the volume of air that can be exhaled from fully inflated lungs is a powerful indicator of longevity and classified people by their occupation. He believed that VC should be used in actuarial predictions for life insurance.
Hutchinson's exacting observations showed that in normal subjects the VC is directly related to height, and inversely related to the age of the individual. Weight has only a minor effect on the vital capacity, but he observed that vital capacity became mildly reduced following a large meal. Much later the concept of the timed vital capacity gave us spirometry as we know it today.
The term forced expiratory volume was coined by the British Thoracic Society in 1957, following the work of Tiffeneau and Pinelli of Paris in 1947. This added the timed vital capacity (ie, FEV1) to spirometry. Volume expiratoire maximal seconde is sometimes still called the Tiffeneau value in France today. Forced vital capacity and FEV1 together are useful in identifying patients at risk of many diseases, including COPD, lung cancer, heart attack, stroke, and all-cause mortality.
In 1959 Dr Martin B Wright and C B McKerrow introduced a peak flow measuring device. This first Wright Peak Flow Gauge is a simple and reliable device for maximum flow rate assessment. Devices virtually identical to the original were still in use up to 2003 when a new standard Flow / volume graph Volume / time graph was adopted in Europe which made peak flow for a spirometer correlate with peak flow measurements from a peak flow meter. This is now ISO standard EN ISO 23747:2007. Vitalograph were the first to manufacture Peak Flow Meters to conform to this ISO standard, when it was a CEN standard in 2003.
In 1972 an inventor's anemometer for measuring the top speed of a skier caught the eye of Dietmar Garbe whilst on a skiing trip in the USA. He took this idea and developed it into a device first shown in 1976 for use on humans to measure peak flow. This was a very inexpensive design of peak flow meter which was quickly imitated by other manufacturers. These simple devices made it possible to prescribe peak flow meters for use at home, widely regarded as essential for all asthmatics.
Dietmar and Margaret Garbe with a Mr Thurston founded Garthur (London) Ltd in 1952 and in 1962 produced the first spirometer designed for use outside the laboratory - an office spirometer. They called this spirometer the 'Vitalograph' - Vital after vital capacity and graph indicating the function of the instrumentation. This was the start of the simple, single breath test. Today Vitalograph is the only British owned major spirometer manufacturer.
In 1980 the US Framingham study of over 5,000 men over the age of 30 years reported that the vital capacity is a powerful prognostic indicator. This simple office procedure is a useful predictor of pulmonary disease and cardiac failure and can effectively select groups of persons heading for premature death. Since the FVC predicts cardiovascular as well as noncardiovascular mortality, spirometry measurement is shown as a measure of living capacity, useful for insurance and underwriting purposes - just as John Hutchinson affirmed over 200 years ago! However, to this day, even large insurance policies do not require spirometry to identify persons at high risk of premature mortality.
The British Lung Foundation, NICE, the British Thoracic Society, the GPIAG and others report a high prevalence of undiagnosed and untreated COPD, which increases with age. In particular there is a high prevalence of COPD in both current and former smokers that is not diagnosed, even in the face of clinical respiratory symptoms of classic cough and dyspnea. It is also vital that those people already diagnosed with a respiratory condition have a correct diagnosis and are being managed appropriately. Studies have show that in some areas there is a COPD misdiagnosis rate of up to 27%. The estimated cost savings associated with more accurate diagnosis is around £17.8 million per year.
The Department of Health's 'Lung Improvement Programme' is supporting six improvement project work streams, one of which is Accurate Diagnosis. This work stream focuses on delivering accurate, quality assured, diagnosis at the earliest opportunity along with ensuring a clear differentiation between COPD, asthma and other diseases.
The recent updates to the NICE Guidelines for the diagnosis and management of COPD 2010 state that:
- A diagnosis of COPD should be considered in patients over the age of 35 who have a risk factor (generally smoking) and have any of the following: breathlessness on exertion, chronic cough, regular sputum production, frequent winter 'bronchitis' or wheeze.
- The presence of airflow obstruction should be confirmed by performing post-bronchodilator spirometry. All health professionals involved in the care of people with COPD should have access to spirometry and be competent in the interpretation of the results.
In the USA the Lung Health Study and third National Health and Nutrition Examination Survey were the foundations for a new health-care initiative, the National Lung Health Education Program (NLHEP). "Test your lungs, know your number" was the motto of the NLHEP. The number in particular is FEV1 percent of predicted. This number should remain constant in healthy people even though lung function declines with age. In subjects with COPD which is worsening, this number will decline. COPD can be treated with modern medicines, but early detection is essential for a good outcome.
The NLHEP consensus committee recommends use of forced expiratory volume in 6 s (FEV6), as a surrogate for FVC. Normal lungs empty in six seconds. The FEV6 is an easier test for the test subject than FVC, and has been shown to be a good indicator of both obstructive and restrictive ventilatory disorders.
The forced expiratory manoeuvre is highly dependent on patient cooperation and effort, and is normally repeated at least three times to ensure reproducibility. Since results are dependent on patient cooperation, FEV1 and FVC can only be underestimated, never overestimated. This means that screening for COPD can only give false positives, not miss the presence of disease, of which the sufferer is typically unaware.
In the year 2009 Vitalograph released to the market low cost, simple, accurate, handheld devices that report the key values FEV1, FEV1/FEV6 and comparison with predicted values. These devices monitor the quality of the blow and give a simple digital result. This development is set to bring the concept of pre -spirometry case selection into a new era. Also, in 2011 Vitalograph launched an e-Diary that has stimulated great interest as it is not simply a programme on a PC but a purpose-built medical device.
This spirit of innovation continues to lead advances in respiratory care as companies such as Vitalograph, Medisoft and others invest in ongoing product development to support clinical needs and protect the quality of life of those with respiratory conditions.