Background: Spirometry can be considered a routine way to evaluate patients with respiratory complaints, both inside and outside the hospital setting.
Objective: To assess the quality of spirometry in a public health care area with respect to two factors: the technicians' performance and the calibration of spirometers.
Material and method: Four health care clinics were studied. Four technicians participated and the four spirometers were tested at different volumes (calibration syringes 1L and 3L) and different flows (explosive decompression). Eight patients with COPD participated in the study of inter-technician variability.
Results: Agreement among the technicians was very high: 0.98-0.99 for FEV1 and 0.91-0.98 for FVC. The mean results obtained by the technicians were: FEV1 = 2.15 0.03, range 2.20-2.14; FVC = 3.25 0.05, range 3.30-3.21 (ns). Volumetric readings from the spirometers were correct for the 1I calibration syringe, but 2 out of 4 spirometers lost linearity with the 3I calibration syringe. One spirometer gave readings out of range for all flow levels, and 2 out of 4 spirometers were out of range at low flows.
Conclusions: 1. Results obtained by different technicians were not significantly different and there was high agreement among them, confirming that performance of spirometry was good. 2. The spirometers showed poor linearity at low flows.