METHODS

Thirty inpatients on rehabilitation wards consented to take part in the study. To obtain as near a random sample as possible all patients meeting the study criteria were asked consecutively if they were willing to be included, until the required number was reached. All had stable, reproducible, AMT scores of 8–10 when tested four to seven days apart. None had previously used any form of inhaler. All were able to read newsprint, with or without glasses, and hear a voice at conversational level with or without a hearing aid.

Patients were excluded if there was evidence of focal neurological loss on clinical examination, a confusional state, or a painful condition of the hands.

All subjects were given standard MDI training using the National Asthma Campaign recommended method and the level of competence reached was scored on a scale of 0–10 by analogue judgment by an experienced observer, where 0 represented the worst possible technique, 10 a perfect technique, and the threshold for adequate competence^2–4 was at 5/6 (5 just incompetent, 6 just competent). The scale is shown in table 1, along with typical observations of technique. A separate observer performed the minimental test (MMT),¹¹ which is a test of global cognitive status, the Barthel index,¹² a score of performance in the activities of daily living, the geriatric depression scale (GDS),¹³ the ideational dyspraxia test (IDT),¹⁴ which tests the ability to describe the use of objects, and the ideomotor dyspraxia test (IMD),¹⁵ which tests the ability to demonstrate the use of objects.

Statistical analysis

Correlation coefficients were calculated using Excel software, and categorical data were tested for statistical significance with Fisher's test.

RESULTS

The results are summarised in tables 2 and 3. A significant correlation was found between inhalation score and IMD, and between inhalation score and MMT. Furthermore, a threshold effect emerged with MMT, in that no subject with a MMT of less than 23/30 had an inhalation score of 5/10 or more (6/10 or more required for a competent score), and all subjects with an inhalation score of 6/10 or more had an IMD score of 14/20 or more.

Three subjects with MMT scores of 23/30 or more had an inhalation score of less than 6/10; however, all had abnormal IMD scores. Therefore, all subjects with an unsatisfactory inhalation score after training had evidence of cognitive impairment or dyspraxia, or both. No correlative or threshold relationship was found between inhalation score and Barthel index, GDS, or IDT. Only two patients had GDS scores in the depression range, though these were not severe and both had inhalation scores of more than 5/10.

DISCUSSION

This study has shown that elderly inpatients who are unable to learn to use a MDI despite a normal AMT score do have evidence of cognitive impairment on testing with the MMT or are dyspraxic.

The observed correlations between inhalation score and MMT or IMD are not of clinical value but do reinforce the contention that cognitive function and praxis are the main determinants of whether a patient will be able reliably to learn to use an inhaler device. Of course, the correlation shown between inhalation score and IMD is somewhat tautological since MDI technique is itself a manifestation of ideomotor function. The threshold effects demonstrated are of use in a clinical setting because they provide a means of identifying patients who are unlikely to cope with a self administered inhaler device. It is noteworthy that the threshold found for the MMT was 22, which is generally taken to indicate definite but mild impairment, with scores of 23–25 representing a borderline score. Similarly, the IMD threshold was 14, which is also close to the borderline score of 16 which is deemed be the lower limit of normal. Of course, these are not hard and fast rules, and the overall clinical context needs to be taken into account; nevertheless, these factors add a further indication that the MMT and IMD might be useful as screening tests.

How might the findings help in practice? While the AMT remains a useful quick screening test for likelihood of being able to use inhaler devices, because an abnormal score is reliably associated with inadequate technique,⁷ there will be some patients with a normal AMT score who cannot use an MDI properly if the AMT score alone is relied upon for cognitive screening. Our findings suggest that the more sensitive MMT¹¹ might be a more suitable screening test in this context. Furthermore, because subclinical dyspraxia is a frequent finding in frail elderly patients, our results support the contention that if such patients require inhaled therapy they should be assessed with a test of praxis, such as the IMD, as well as the MMT before deciding to proceed with an inhaler device. These tests are not particularly time consuming; the MMT takes about five minutes and the IMD about three minutes. If the results are in the impaired range there is not likely to be a successful result if MDI training is attempted. This is consistent with previous work using the AMT and the MMT for MDIs and other complex devices in elderly subjects.^7,8,16 An earlier study showed that some elderly subjects with borderline or slightly impaired AMT scores can learn to use less complex inhalers, such as the Turbohaler (Astra),^17,18 therefore, further work needs to be conducted to determine whether the MMT and IMD can be used to determine the likelihood of successful acquisition of adequate technique with such inhalers.