Can all patients with COPD use the correct inhalation flow with all inhalers and does training help?

The inhalation rate is important when patients use an inhaler. Dry powder inhalers (DPIs) require an inhalation rate >30 L min(-1) whereas metered dose inhalers (MDIs) should be used at <90 L min(-1). Within the setting of a routine clinic, we have measured peak inhalation flows (PIF) of COPD patients when they used a Diskus (SDSK), Turbuhaler (STBH), Handihaler (SHAND) and MDI. Subjects were then randomised into trained (VT) and non-trained (NT) groups. One hundred and sixty-three patients with a mean (S.D.) age and % predicted FEV(1) of 72.5 (9.9) years and 47.8 (22.2)% completed the study. Of the patients, 4.9%, 14.2% and 57.0% inhaled <30 L min(-1) through SDSK, STHB and SHAND, respectively and 59.5% inhaled >90 L min(-1) with the MDI. Generally, the more severe the COPD, the slower was their PIF with all inhalers. The MDI PIF values in the VT group (n=84) post-training were significantly (p<0.001) slower but there was no change for the DPIs. Of the 55 VT patients inhaling >90 L min(-1) through the MDI only 7 (p<0.001) inhaled too fast post-training. Pre-training 3, 15 and 46 VT subjects inhaled <30 L min(-1) through the SDSK, STBH and SHAND and after training none, 5 and 26 did not inhale faster than this minimum required rate. Some COPD patients have problems achieving required PIFs through DPIs but training is useful to help some exceed the minimum required rate despite only small improvements. The patients found it easier to slow their PIF through the MDI.

Emitted dose estimates from Seretide Diskus and Symbicort Turbuhaler following inhalation by severe asthmatics.

The dose emitted from dry powder inhalers may be inhalation flow-dependent. Using an ex vivo method, the Electronic Lung, we have measured the aerodynamic characteristics of the emitted dose for both active constituents from Seretide Diskus (salmeterol xinafoate 50 mcg; fluticasone propionate 500 mcg) and Symbicort Turbuhaler (formoterol 6 mcg; budesonide 200 mcg). Electronic inhalation profiles were collected from 20 severe asthmatics (mean PEFR 53% predicted) when they inhaled using a placebo Seretide Diskus and a placebo Symbicort Turbuhaler. These were replayed in the Electronic Lung with the respective active inhaler in situ. Mean(S.D.) peak inhalation flow rates (PIFR) through the Diskus and Turbuhaler were 94.7(32.9) and 76.8(26.2) l min(-1), respectively. From the Electronic Lung the Diskus inhalation profiles provided a mean(S.D.) fine particle dose (FPD) for fluticasone propionate and salmeterol of 20.4(4.8) and 18.4(4.4)% labelled dose. For Turbuhaler inhalation profiles the FPD was 23.1(12.9) and 20.7(11.1)% labelled dose for budesonide and formoterol, respectively. The linear (p < 0.001) relationships between FPD against PIFR for budesonide and formoterol were 3 (p = 0.002) and 2.8 (p = 0.007) times steeper than fluticasone propionate and salmeterol, respectively. The results highlight a more significant effect of inspiratory flow on variable dosage emission when using the Symbicort Turbuhaler compared with the Seretide Diskus.