Introduction: Preserved ratio impaired spirometry (PRISm) is used when a patient has a normal ratio of forced expiratory volume in 1 second to forced vital capacity (FEV₁/FVC ?LLN) but decreased FEV₁ or FVC. Often in patients with a restrictive pattern the lung volumes are normal.

Aim: The present study aims to determine whether the restrictive pattern is real or spirographic phenomenon in patients diagnosed with asthma.

Materials and methods: We analyzed spirometry data from 150 patients with a clinical diagnosis of asthma. Final data included 30 patients with restrictive pattern aged 61.0 ± 12.2. All pulmonary function tests were performed on a computer spirometer MasterScreen Diffusion? (Jaeger, Wuerzburg, Germany), with  real time curves and automatic correction (BTPS). In all patients bronchodilator test (BDT) was also conducted.

Results:The main spirometric parameters ? VC, FVC, and FEV1 in the studied population were decreased but their ratios were normal. In women was found a higher incidence of obesity, while men were more overweight. The values of inspiratory capacity in women rose after BDT by an average of 230 ml, while for men this value was 140 ml. We found that both genders maintained the restrictive pattern after the bronchodilator test (BDT), but also a positive bronchodilator test was found in 13 patients, accounting for 43.3% of the total group.

Conclusion:

The restrictive pattern in patients with obstructive diseases is a possible finding and may be due to obesity or pulmonary hyperinflation. Bronchodilator test increases the reliability of the examination.