Four-quadrant quantitative inhalation assessment and one-year changes in COPD Assessment Test scores in newly diagnosed COPD A descriptive longitudinal study

Abstract Background Inhalation performance includes device-dependent inspiratory flow, post-inhalation breath-holding and actuation–inhalation coordination. We characterised baseline performance using a four-quadrant classification and examined the association between baseline classification and one-year change in COPD Assessment Test (CAT) score in patients with newly diagnosed chronic obstructive pulmonary disease (COPD). Methods This single-centre descriptive longitudinal study included 484 patients with newly diagnosed, stable COPD who completed one year of regular inhaled therapy without an acute exacerbation. Baseline peak inspiratory flow (PIF) and breath-hold duration were graded from A (highest assessment priority) to D (lowest). Hand–mouth coordination contributed to the classification only when the recorded impedance grade was 0. Each patient was assigned the highest-priority grade among the contributing components. PIF thresholds were study-defined and device-specific. All patients received routine verbal inhaler education. The primary outcome was one-year change in CAT score (ΔCAT); a reduction of at least 2 points defined a CAT responder. Associations between baseline quadrant and CAT outcomes were examined using the Kruskal–Wallis test, chi-square test and baseline-adjusted analysis of covariance. Results PIF below the study-defined threshold occurred in 69/158 dry-powder inhaler users (43.7%), 16/91 soft-mist inhaler users (17.6%) and 13/235 pressurised metered-dose inhaler users (5.5%; P < 0.001). Composite quadrants A–D included 259, 84, 58 and 83 patients, respectively. Breath-hold duration was < 3 s in 254 of 259 patients in quadrant A. Reported CAT scores were 11.1 (interquartile range [IQR], 7.0–14.0) at baseline and 7.9 (IQR, 5.0–10.0) at one year; the reported ΔCAT was − 3.2 (IQR, − 6.0–0.0) points. Neither ΔCAT nor responder proportions differed significantly across quadrants (P = 0.711 and P = 0.909, respectively). The association between quadrant and CAT change remained non-significant after adjustment for baseline CAT (P = 0.487). Conclusions Short post-inhalation breath-hold duration was the most frequent component assigned the highest assessment priority. The proportion below the study-defined PIF threshold differed by inhaler class, but this comparison does not establish an independent effect of device resistance. No statistically significant association between baseline quadrant and one-year CAT change was detected in this selected cohort. Repeated performance assessments and external validation are needed before the classification can guide prognosis or intervention.