Determining When Enhanced Pause (Penh) is Sensitive to Changes in Specific Airway Resistance

Abstract

Penh is a dimensionless index normally used to evaluate changes in the shape of the airflow pattern entering and leaving a whole-body flow plethysmograph as an animal breathes. The index is sensitive to changes in the distribution of area under the waveform during exhalation and increases in a nonlinear fashion as the normalized area increases near the beginning of the curve. Enhanced pause (Penh) has been used to evaluate changes in pulmonary function and as a method to evaluate airway reactivity. However, the use of Penh to assess pulmonary function has been challenged (Bates et al., 2004; Lundblad et al., 2002; Mitzner et al., 2003; Mitzner & Tankersley, 1998; Petak et al., 2001; Sly et al., 2005). The objective of this study was to show how Penh of the thorax and plethysmograph flow patterns are related. That relationship is used to describe the conditions under which whole-body plethysmograph Penh measurements can be used to detect changes in sR_aw.

Notes

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The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

*The data used in this example was taken from a previous pilot study. Specific pathogen free male Sprague-Dawley rats (405 ± 20 g) were purchased from Hilltop Laboratories (Scottdale, PA). The rats were housed in an AAALAC-accredited animal facility at 23OC and 50% relative humidity with a 12 hour light/dark cycle and were provided an autoclaved Prolab 3500 diet and tap water ad libidum. The rats were acclimated for 2 weeks prior to exposure to a methacholine aerosol (200mg/m3 of a 300mg/ml solution).