Impact of Preliminary Bronchodilator Dose in Chronic Obstructive Pulmonary Disease Patients With Suboptimal Peak Inspiratory Flow

Purpose: Suboptimal peak inspiratory flow rate (PIFR) is highly prevalent in patients with chronic obstructive pulmonary disease (COPD) owing to the mismatch of their PIFR with the corresponding inhaler-device resistance. This study aimed to investigate the impact of a preliminary dose of pressurized metered dose inhalers (pMDIs) on patients with COPD with suboptimal PIFR using Diskus dry powder inhalers (DPIs).

Methods: A prospective, randomized, case-control study included 24 patients with COPD. PIFR was measured using the In-Check Dial G16 with low-to-medium resistance. Spirodoc was used to measure baseline spirometric data and compare it before and 30 minutes after the administration of Diskus DPI. On a different day, the study dose was given to each suboptimal patient by the same aerosol generator with preceded 2 puffs of salbutamol pMDI and re-evaluated for spirometric parameters 30 minutes after the study dose.

Findings: There was a significant difference between the optimal and suboptimal groups in peak expiratory flow (2.38 ± 1.20 vs 1.49 ± 1.06 L/s, P = 0.050). PIFR showed a statistically significant difference between the optimal and suboptimal groups (71.66 ± 6.15 vs 41.25 ± 9.79 L/min, P < 0.0001). There was a significant difference in forced vital capacity (ΔFVC) between optimal and suboptimal groups without a preliminary dose (0.42 ± 0.21 vs 0.16 ± 0.11 L, P = 0.002), forced expiratory volume in 6 seconds (ΔFEV₆) (0.53 ± 0.49 vs 0.17 ± 0.11 L, P = 0.022), forced expiratory volume in 3 seconds (ΔFEV₃) (0.41 ± 0.38 vs 0.1 ± 0.16 L, P = 0.013), forced expiratory volume in 1 second (ΔFEV₁)/FVC (-2.38 ± 8.41 vs 2.96% ± 2.95%, P = 0.033), and ΔFEV₁/FEV₆ (-4.32 ± 11.23 vs 2.91% ± 4.35%, P = 0.015). There was a significant difference in ΔFVC between optimal and suboptimal groups with a preliminary dose (0.42 ± 0.21 vs 0.23 ± 0.18 L, P = 0.046), ΔFEV₁/FVC (-2.38 ± 8.41 vs 5.67% ± 6.53%, P = 0.009), ΔFEV₁/FEV₆ (-4.32 ± 11.23 vs 5.16% ± 4.99%, P = 0.008), and forced expiratory time (ΔFET) (0.28 ± 0.45 vs -0.31 ± 0.70 seconds, P = 0.022). The only parameter that showed a significant difference between suboptimal groups without and with a preliminary dose is Δ peak expiratory flow (0.24 ± 0.59 vs 0.65 ± 0.68 L/s, P = 0.004).

Implications: Administering a preliminary dose of pMDI can minimally enhance the effectiveness of DPIs in patients with COPD with suboptimal PIFR and health outcomes.