title: Statistics and graphs for heart rate variability: pNN50 or pNN20?
abstract: Two measures of heart rate variability, pNN50 and pNN20, are compared. A non-linear transformation of these measures is proposed, that is helpful in understanding their interrelationship. Provided a valid statistical test is employed, results from analysing pNN20 are likely to be equivalent to those from analysing pNN50. Arguments recently made by Mietus et al (2002 Heart 88 378-80) against the commonly used pNN50 are unconvincing.
mesh_terms: D003627:Data Interpretation, Statistical; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008955:Models, Cardiovascular; D008959:Models, Neurological; D017711:Nonlinear Dynamics; D010275:Parasympathetic Nervous System / Q000502:physiology*