Fig. 6.
Syringe volume errors produced by syringe potentiometer (SP), weighted averaging (WA), and polynomial least-squares (PolyLS) calibration methods as a function of increasing numbers of calibration strokes. Values are presented as means ± 95th percentile confidence interval (CI95%). The gray shaded region denotes the ±3.5% error margin of volume errors as recommended by the American Thoracic Society and the European Respiratory Society (11). Note that CI95% of volume errors produced by the SP and WA methods fall within the recommended error margin after only 5 calibration strokes, whereas it takes 20 strokes with the PolyLS method to achieve the same level of volume accuracy.