DOI: 10.5061/dryad.jdfn2z3c0
title: Variability of RRate: breathing and quality data

description: Background: Respiratory rate is difficult to measure, especially in
 neonates who have an irregular breathing pattern. The World Health
 Organisation recommends a one minute count, but there is limited data to
 support this length of observation. We sought to evaluate agreement
 between the respiratory rate (RR) derived from capnography in neonates,
 over 15 seconds, 30 seconds, 120 seconds and 300 seconds, against the
 recommended 60 seconds rate. Methods: Neonates at two hospitals in Nairobi
 were recruited and had capnograph waveforms recorded using the Masimo Rad
 97. A single high quality 5 minute epoch was randomly chosen from each
 subject. For each selected epoch, the mean RR was calculated using a
 breath-detection algorithm applied to the waveform. The RR in the first 60
 seconds was compared to the mean RR measured over the first 15 seconds, 30
 seconds, 120 seconds, full 300 seconds, and last 60 seconds. We calculated
 bias and limits of agreement for each comparison and used Bland-Altman
 plots for visual comparisons. Results: A total of 306 capnographs were
 analysed from individual subjects. The subjects had a median gestation age
 of 39 weeks with slightly more females (52.3%) than males (47.7%). The
 majority of the population were term neonates (70.1%) with 39 (12.8%)
 having a primary respiratory pathology. There was poor agreement between
 all the comparisons based on the limits of agreement [confidence
 interval], ranging between 11.9 [-6.79 to 6.23] breaths per minute in the
 one versus two minutes comparison, and 34.7 [-17.59 to 20.53] breaths per
 minute in the first versus last minute comparison. Worsening agreement was
 observed in plots with higher RRs. Conclusions: Neonates have high
 variability of RR, even over a short period of time. A slight degradation
 in the agreement is noted over periods shorter than one minute. However,
 this is smaller than observations done 3 minutes apart in the same
 subject. Longer periods of observation also reduce agreement. For device
 developers, precise synchronization is needed when comparing devices to
 reduce the impact of RR variation. For clinicians, where possible,
 continuous or repeated monitoring of neonates would be preferable to one
 time RR measurements.
description: The Masimo Rad-97 pulse CO-oximeter with capnography (Masimo
 Corporation, USA) was used to collect continuous capnograph waveforms from
 neonates.  Following data collection, the capnograph (carbon dioxide,
 CO<sub>2</sub>) waveform data at approximately 20Hz was
 inputted into a custom breath detection algorithm developed in MATLAB
 (Math Works, USA) based on adaptive pulse segmentation. The algorithm
 analysed the waveform’s shape and identified the start and end of each
 breath (waveform trough to trough), and this breath duration was used to
 calculate an instantaneous respiratory rate (breaths per minute) for each
 breath. A mean respiratory rate was calculated by taking the mean of the
 instantaneous rates for all breaths within the epoch. A breath was
 considered to be within the epoch if its peak, as identified by the
 algorithm, was within the epoch. Additionally, the algorithm calculated a
 capnography quality score at 2Hz. The statistical program R was used to
 process this information and randomly select high quality 5-minutes epochs
 for each subject. The high quality criteria threshold was 90% of RR
 quality scores in the epoch meeting the minimum quality score of 2,
 indicating a regular capnography waveform with an appropriate shape (that
 is, minimal variation of amplitude, time interval, up-slope and down-slope
 of waveform peaks when compared).