Digital spirometer

Dr Raj Thakkar reviews a hand-held digital spirometer.

If you don't have time to read the whole of this review, I can summarise it in two words: 'buy it!'

For those with a little more time, shut your surgery door, take the phone off the hook, put your feet up and read on.

The NICE guidelines on COPD, published in 2004, state that 'all health professionals managing patients with COPD should have access to spirometry and be competent in the interpretation of the results'.

Despite NICE also stating 'routine spirometric reversibility testing is not necessary as a part of the diagnostic process or to plan initial therapy with bronchodilators or corticosteroids', the latest changes to QOF require pre- and post-bronchodilator spirometry.

This is arguably helpful to differentiate COPD from asthma. Nevertheless, given COPD is under-diagnosed and there is a significant morbidity and mortality associated with the condition, it is imperative all GPs have access to a reliable and user- friendly spirometer. Of course, spirometry is also invaluable for disease monitoring, screening and assessment of fibrotic and occupational lung diseases.

Great design
There are a number of spirometers on the market, so what is it about the MicroLoop MK8 that makes it a must buy? Admittedly, it isn't the cheapest but you do get what you pay for.

The kit comes in a sturdy foam-filled case which houses the device itself, power and computer docking cradle, cables and there is space for eight mouthpieces. It even comes with a nose-clip, advised for optimum technique.

The device itself is around the size of, and has the feel of a PDA (personal digital assistant). It has a high-definition, colour touch-sensitive screen, which conveniently displays the battery life and time. Less than a minute is required to attach the transducer and disposable mouth piece to the device.

Easy to use
Once activated, the on screen menu is incredibly easy to follow. By using the built-in stylus, various options can be selected including 'forced spirometry', which automatically reveals the patient details screen. Sex, age, height and weight are then entered as well as an adjustment factor for ethnicity. Predicted values are then calculated by the internal computer based on national demographics.

Once the patient data is entered, a colour graph appears on the screen with a prompt to start breathing. As the patient blows, the flow/volume data is plotted in real time. In order to meet national standards, three readings are required with less than 5 per cent variability between them.

The MicroLoop helpfully displays the percentage variability with each blow so the patient is managed using reliable data. If the blow effort is deemed inadequate, the device will display why, 'poor effort' and 'abrupt end' for example. Animated cartoon prompts are available for children.

Numerical values and volume/time traces are displayed, again with the touch of a button. Post-bronchodilator blows can be measured, compared and recorded in order to assess for reversibility. A vast array of parameters, 45 in total, can be measured using the device if the user so requires and are displayed in absolute units as well as percentage predicted. Measurements include peak flow and lung age. In trials, resistant smokers take more notice of advanced lung age than a reduced FEV1 or FEV1:FVC.

Variety of parameters
Many of the cheaper spirometers offer basic data such as FEV1 and FVC, which can be used for screening and monitoring, although many don't even offer predicted values. While these screening spirometers may be appealing for their simplicity and value-for-money, relying purely on FEV1, FVC and FEV1:FVC may be misleading.

In some patients, a forced spirometry manoeuvre may cause excessive airways collapse and hence a falsely low FVC. In this case, a relaxed blow should be measured and the FVC substituted for the 'relaxed vital capacity' (rVC, sometimes known as the VC). Hence, the greater of the FVC or the VC should be used in spirometry calculations when assessing patients for COPD.

Take the following example: FEV1=1.80, FVC=2.10, VC=3.2. FEV1:FVC is 86 per cent, suggestive of lung restriction whereas FEV1:VC is 56 per cent, indicating obstructive lung disease.

The MicroLoop has a relaxed spirometry function too, which caters for this so that the patient is assessed with accuracy.

The device has the feel of a PDA with a high-definition colour screen

Data storage
Data for over 2,000 tests can be stored in the device's internal memory and information can be held for individual patients allowing comparison of tests over time. Test data can be printed directly from the machine or transferred to a PC and attached to patient records such as EMIS with additional software.

The verdict
The system is portable enough for home testing and simple enough for technophobes. A help button provides useful and practical support.

The MicroLoop is sophisticated but GP- and patient-friendly. In my view, it is a must-have for any modern practice.

Dr Thakkar is a GP in Wooburn Green, Buckinghamshire.

Equipment supplied by Williams Medical Supplies.

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