PURPOSE: Changes in tidal breathing flow and volume parameters indicate airway obstruction. Impedance pneumography (IP) is a promising method for long-term ambulatory measurements of tidal breathing. IP is based on the measurement of the electrical conductivity of the thorax that changes with lung volume. The purpose of this study is to assess the agreement between a pneumotachograph (PNT) and IP in estimation of ratio of time to peak tidal expiratory flow to expiratory time (tptef:te).
METHODS: Simultaneous registration of IP and PNT was conducted on 37 healthy sitting adults (12 female, age 21-27 years) during tidal respiration for 40 breaths. The cycles with tptef:te values outside the 25% and 75% percentiles were discarded, and the mean of the remaining 20 values obtained with both methods was calculated. Additionally, the reliability of both methods was assessed by dividing the 40 tptef:te values from both methods of each person randomly into two pools (IP1/IP2 and PNT1/PNT2), discarding the values outside 25% and 75% percentiles and calculating the mean tptef:te for the 10 breaths of both pools of both methods. Comparison between and within methods were made by Bland-Altman analysis with 95% confidence intervals.
RESULTS: The tptef:te values from IP and PNT were 0.36±0.12 and 0.34±0.15, respectively. The difference between IP and PNT in tptef:te estimation in individual subjects was 0.02±0.09. In the method reliability assessment, the difference between IP1 and IP2 was 0.00±0.07 and between PNT1 and PNT2 0.00±0.07.
CONCLUSION: The variation between tptef:te values obtained with IP and PNT has 95% confidence interval close to the interval obtained for both methods for reliability. There is no significant discrepancy in the mean values between the two methods.
CLINICAL IMPLICATIONS: These results show that IP is potentially a suitable method for tidal breathing studies, possibly for assessing the long-term variation in airway obstruction.
DISCLOSURE: Ville-Pekka Seppä, No Financial Disclosure Information; No Product/Research Disclosure Information