Metered dose inhalers (MDIs) are commonly prescribed for inhalation therapy, but correct use is critical to promoting effective medication delivery. This systematic literature review and meta-analysis evaluates the overall and step-by-step prevalence of errors among adults with obstructive lung diseases in the United States who used MDIs.Electronic and manual searches conducted between 1979-2018 using PubMed, EMBASE, PsycINFO, Cochrane, and Google identified 10 articles that met the following inclusion criteria: (a) English language, (b) U.S. adults diagnosed with chronic obstructive pulmonary disease, and (c) MDI use error rates. Meta-analytic techniques using random-effects models were applied to calculate effect sizes, weighted proportions, and 95% confidence intervals (CIs). Heterogeneity was assessed by the I statistic.Aggregate findings revealed that 86.7% of patients (n=390, 95% CI 77.5-96.0) made at least 1 inhalation technique error, and 76.9% (n=885, 95% CI 65.8-87.9) incorrectly performed ≥ 20% of device use steps. The most prevalent step-by-step errors across the studies (n=1105) were failure to: (a) exhale fully and away from the inhaler before inhalation (65.5% [95% CI 52.0, 78.9]); (b) hold breath for 5-10 seconds (41.9% [95% CI 29.8, 53.9]); (c) inhale slowly and deeply (39.4% [95% CI 26.2, 52.5]); (d) exhale after inhalation (35.9% [95% CI 17.0, 54.8]); and (e) shake the inhaler before use (34.2% [95% CI 30.6, 37.7]).Across the studies used in this meta-analysis more than three-fourths of U.S. adults with obstructive lung diseases used MDIs incorrectly. Our findings suggest the need for ongoing patient education and consideration of alternative devices to mitigate errors.