Abstract: This review includes 29 parallel randomised controlled trials (RCTs) (n = 2210), although not all reported relevant or useable data. All participants had asthma, and follow-up ranged from 2 to 26 weeks. Most studies were at low or unclear risk of selection and attrition biases and at high risk for biases associated with blinding. We considered most of the evidence to be of low quality owing to these biases and to imprecision in the estimates of effect. We classified studies into three comparisons: enhanced face-to-face training session(s), multi-media-delivered inhaler training (e.g. DVD, computer app or game) and technique feedback devices. Differences between interventions, populations and outcome measures limited quantitative analyses, particularly for exacerbations, adverse events, unscheduled visits to a healthcare provider and absenteeism from work or school. Enhanced inhaler technique education and multi-media training improved technique in most studies immediately after the intervention and at follow-up, although the variety of checklists used meant that this was difficult to assess reliably. For both adults and children, how and when inhaler technique was assessed appeared to affect whether inhaler technique improved and by how much. Analyses of the numbers of people who demonstrated correct or 'good enough' technique were generally more useful than checklist scores. Adult studies of enhanced education showed benefit when this metric was used at 2 to 26 weeks' follow-up (odds ratio (OR) 5.00, 95% confidence interval (CI) 1.83 to 13.65; 258 participants; three studies; 31 per 100 with correct technique in the control group compared with 69 (95% CI 45 to 86) in the education group; moderate-quality evidence). A similar result was seen in studies looking at feedback devices at four weeks' follow-up (OR 4.80, 95% CI 1.87 to 12.33; 97 participants; one study; 51 per 100 with correct technique in the control group compared with 83 (95% CI 66 to 93) in the feedback group; low-quality evidence). However, the benefit of multi-media training for adults even immediately after the intervention was uncertain (OR 2.15, 95% CI 0.84 to 5.50; 164 participants; two studies; I² = 49%; 30 per 100 in the control group with correct technique compared with 47 (95% CI 26 to 70) in the multi-media group; moderate-quality evidence). Evidence tended to be less clear for children, usually because results were based on fewer and smaller studies. Some studies did not report exacerbations in a way that allowed meta-analysis; others provided inconclusive results. Inhaler technique interventions provided some benefit for asthma control and quality of life but generally did not lead to consistent or important clinical benefits for adults or children. Confidence intervals included no difference or did not reach a threshold that could be considered clinically important. Responder analyses sometimes showed improvement among more people in the intervention groups, even though the mean difference between groups was small. We found no evidence about harms. Although interventions to improve inhaler technique may work in some circumstances, the variety of interventions and measurement methods used hampered our ability to perform meta-analyses and led to low to moderate confidence in our findings. Most included studies did not report important improvement in clinical outcomes. Guidelines consistently recommend that clinicians check regularly the inhaler technique of their patients; what is not clear is how clinicians can most effectively intervene if they find a patient's technique to be inadequate, and whether such interventions will have a discernible impact on clinical outcomes.

Plain-language summary: We found 29 studies involving 2210 people with asthma. Studies lasted between 2 and 26 weeks. Studies reported inhaler technique on a range of different checklists. We grouped studies into three types: studies testing enhanced face-to-face training session(s), studies using multi-media to deliver inhaler training (e.g. a video, computer app or game) and studies testing devices that give people visual or audio feedback about technique. Studies tested different types of training and used different measures to gauge success, meaning that we could not bring data together. This was particularly true when we tried to assess effects on asthma attacks, adverse events, visits to a healthcare provider and absences from work or school. Both face-to-face and multi-media inhaler training improved inhaler technique in most studies, although results varied depending on how and when each technique was assessed. Some studies reported the number of people who had correct or 'good enough' technique. More people had correct or 'good enough' technique after face-to-face training and with feedback devices. But the benefit of multi-media training for adults was uncertain. Interventions that provide inhaler training may bring some benefit for quality of life and asthma control among adults and children, but results were varied and studies were small. Children may receive some benefit but results tended to be less clear for children because fewer and smaller studies have included children as participants. For studies like these, it is not possible to blind people to their assigned group. This may bias how people behave or respond to questionnaires, which reduced our confidence in the findings. We were uncertain about other results because studies did not provide enough data to show clear benefit. We cannot say for sure what is the best way to help people learn how to use their inhaler properly. It is important that patients understand how their inhaler works, so they should ask their doctor or nurse for help. We also use Cochrane Reviews to make suggestions for future research. We suggest that trials should last longer than six months and should report adherence information. The most useful information reported was the number of people who had 'good enough' inhaler technique, so we urge future trials to report this as well.