Apnea-onset definition significantly affects pneumogram results

Pneumogram (PG) scoring methods have not been standardized. To determine the extent to which varying definitions for apnea-onset and apnea-termination will result in clinically significant differences in calculated apnea density (A6/D%) and periodic breathing, we analyzed 40 randomly selected PGs. All PGs were initially scored using end-expiration (EE) to mark the beginning of each apnea. As the second definition, peak inspiration (PI) was used to identify the onset of each apnea. All apneas greater than or equal to 6 s in duration and all episodes of periodic breathing were identified. The differences between results obtained by each definition were compared by paired t-test. The differences between the EE and PI definitions were statistically significant (p less than 0.01) for A6/D%, periodic breathing, longest apnea, and number of apneas greater than 11 s, with the PI definition consistently resulting in higher values. In summary, calculated PG results are significantly different, both clinically and statistically, depending on the scoring definition utilized for apnea-onset. Although each definition will yield results that are internally consistent, it is crucial that the normative standards used for comparison be derived utilizing the same scoring definition.