Azouz, Wahida Ahmed Abugrara (2012) Novel methodology to characterise how asthma and chronic obstructive pulmonary disease patients use their inhalers and methods to improve their inhaler technique Objective assessment of how patients use inhalers. Doctoral thesis, University of Huddersfield.

Inhaled administration is the mainstay of asthma and chronic obstructive pulmonary disease (COPD) management using either a pressurised metered dose inhaler (pMDI) or a dry powder inhaler (DPI). Poor disease control and increased hospitalisations is linked to poor inhaler technique. Previous studies to assess inhaler technique have used subjective measures and there is very limited data about the inhalation characteristics used by patients when they use their inhalers.

Inhalation flow profiles when patients use their pMDI and inhalation pressure profiles when they use DPIs have been measured using 659 subjects (106 children with asthma [CHILD], 361 adults with asthma [ADULT], 142 COPD [COPD] and 50 healthy volunteers [HEALTHY]) in 5 separate studies. All patient studies used their real life inhaler technique. One of the studies also evaluated the value of using a pMDI co-ordination aid and training these patients to prolong their inhalation whilst a different one investigated the impact of using enhanced training when using a DPI.

The first study, 20 CHILD, 57 ADULT and 32 COPD subjects, revealed that the mean (SD) inhalation flows through a pMDI were 108.9 (40.4), 146.0 (58.8) and 107 (50.6) L/min, respectively and only 7, 10 and 10 used a slow flow. In the second pMDI study involving, 20 CHILD, 130 ADULTS, 31 COPD patients, their flows were 70.5 (36.4), 131.4 (60.8) and 70.9 (28.1) L/min and 5, 53 and 10 used their pMDI with good co-ordination. However only 3, 6 and 9 patients had good co-ordination and slow flow. In the third study, 71 ADULT patients, the mean (SD) pMDI inhalation flow was 155.6 (61.5) L/min which decreased (p<0.001) to 112.3 (48.4) when the pMDI was fitted with a co-ordination aid. This was due to the increased resistance to airflow from the aid. Inhalation flow further reduced (p<0.001) to 73.9 (34.9) L/min when patients were trained to prolong their inhalations. Their inhaled volumes did not change whereas mean (SD) inhalation times were 1.60 (0.21), 1.92 (0.80) and 2.66 (1.03) seconds (p< 0.001) respectively. There was a good correlation between their inhaled volume and forced vital capacity with a ratio of 0.7 suggesting that the patient used a full inhalation.

A DPI study, involving 16 CHILD, 53 ADULT and 29 COPD patients, measured inhalation characteristics through different DPIs (low to high resistance) when patients used their real life DPI inhalation manoeuvres. The inhalation characteristics were lower in CHILD and highest in ADULT. Overall flows were higher when using low resistance DPIs but the pressure changes and the acceleration of the inhalation flow were significantly higher with high resistance DPIs which suggest more efficient de-aggregation of the formulation. There was a tendency for more problems with low resistance DPIs than high resistance DPIs. The last study involved CHILD, ADULT, COPD and HEALTHY subjects (50 of each) when they inhaled through a Spiromax and a Turbuhaler (similar resistance) after standard verbal inhalation technique training and when using enhanced training with an IN-Check Dial. The order of inhalation characteristics was HEALTHY > ADULT > COPD > CHILD. Significant (p<0.001) improvements in the inhalation flows, pressure changes and acceleration of the flow were achieved in all groups after the enhanced training.

The studies provide an insight into the inhalation characteristics of patients when they use different inhalers. The main problem with pMDI use was short inhalation times and when patients were trained to prolong their inhalation then flows reduced. Enhanced training when using a DPI significantly improved the technique of all patients.

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