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 ≥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 EE and PI definitions were statistically significant (p < 0.01) for A₆/D%, periodic breathing, longest apnea, and number of apneas >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.