Experts have called for better research on the impact of inhaler technique on COPD outcomes, after a systematic review found only ‘weak’ evidence of a correlation between the two.
A team led by Professor David Halpin, Consultant Physician and Honorary Professor of Respiratory Medicine, University of Exeter, reviewed 7 cohort and 12 case-control studies involving 6,487 patients, which objectively assessed inhaler errors and also had data on at least one of the following: FEV1, dyspnoea, health status or exacerbations.
Overall, the review found only “weak evidence” that lower inhaler error rates were linked with improved FEV1, symptoms and health status and fewer exacerbations, and when considering individual errors, only some were associated with worse outcomes, according to the paper, published in BMJ Open Respiratory Research (link here).
“Although it seems obvious that patients who do not use a device correctly will not get the full benefit of the drugs they contain, this systematic review found only weak and inconsistent evidence that making fewer mistakes using inhalers is associated with better clinical outcomes,” the researchers said.
An association between inhaler errors and FEV1, symptoms, health status and moderate exacerbations was observed in some cohort trials, but in each case in less than 100 patients.
In case-control studies, an association between inhaler errors and poorer outcome was seen for exacerbations (more than 100 patients) and FEV1 (less than 100 patients).
‘Low quality’ evidence
However, more than three-quarters (15) of these studies were deemed to be ‘low quality’, and most were confounded due to a lack of adherence data, they stressed.
Notably, only one study (PIFotal COPD) reported on the association between specific inhaler errors using a DPI and clinical outcomes.
This found that only mistakes in the technique used to breathe was linked with significantly worse health status, higher secondary healthcare costs, higher total COPD-related healthcare costs and severe – but not moderate – exacerbations, which suggests that “the finding may be confounded and more likely to be due to patients with more severe diseases having problems using inhalers correctly”.
The authors also noted that this study found no significant impact from a “failure to remove the protective cap’ on the device, “calling into question the relevance of the overall findings of the study and the definition of critical errors”.
Other limiting factors of the review were heterogeneity between the studies, short follow-up periods, that exacerbation rates were mostly based on patient recall, that most studies failed to take adherence into account, and a lack detail for quantitative analysis.
As such, “the lack of evidence found in this narrative review does not mean that teaching patients how to use their inhalers correctly and regularly checking their technique is unimportant,” they stressed.
“Better prospective studies with longer follow-up examining clinical outcomes in patients who make fewer errors after training are needed. Ideally, such studies should include objective monitoring of inhalation technique and adherence using digital inhalers, as well as examining the effect of specific errors”.