OBJECTIVE

We have measured peak inspiratory flow (PIF), inspiratory capacity (IC), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) and other functional parameters in COPD patients to investigate which PIF's patients generate with maximal effort, through three different resistances, representing Diskus, Nexthaler and Turbuhaler.

PATIENTS AND METHODS

Forty patients with COPD were enrolled in this study. All patients were examined: pulmonary function tests, including flow/volume spirometry and N2-wash out, were conducted. MIP and MEP were measured. PIF was measured using the In-check DIAL; patients inhaled through the device set for the optimal Turbuhaler resistance, Nexthaler resistance and Diskus resistance. The relationship between lung function parameters and PIF was studied.

RESULTS

The mean PIF through Nexthaler resistance was significantly higher than the Turbohaler resistance. We have found a mild correlation between PIF and MIP and between PIF, IC and VC.

DISCUSSION

All patients could achieve inspiratory flows > 30 l/min with all inhalers used for the trial. The most interesting result is the mild correlation between MIP and PIF, showing that inspiratory muscle force is probably an important predictor of an adequate inspiratory flow in COPD patients. Many studies confirmed that when using a DPI the inhalation flow is dependent on the resistance of the device and the patient's inspiratory effort.

CONCLUSIONS

Inhalation therapy is the mainstay of treatment of patients with COPD. In the last years, significant developments have been achieved in the field of device formulation, but in daily practice, an appropriate inhaler choice should consider not only device related aspects, but also patient's pulmonary function and in particular patient's respiratory muscle strength.