1. Validation of a new non-invasive automatic monitor of respiratory rate for postoperative subjects 
G.B. Drummond, A. Bates, J. Mann, D.K. Arvind 
British Journal of Anaesthesia 
Volume 107, Issue 3, Pages (September 2011)
DOI: /bja/aer153
Copyright © 2011 The Author(s) Terms and Conditions

2. Fig 1
Derivation of respiratory signal. (a) The Orient speck device measures acceleration in three orthogonal directions, and nasal cannula pressure is a measure of respiratory flow. (b) The same time period, showing combination of the acceleration trace into a mean measure that is presented as a rate of rotation, becoming analogous to flow. The waveforms are very similar.
British Journal of Anaesthesia  , DOI: ( /bja/aer153)
Copyright © 2011 The Author(s) Terms and Conditions

3. Fig 2
Signal analysis procedure for comparison of respiratory rates obtained from the two devices. The cannula signal (top trace) is used as the standard. Onset of a breath is detected when the signal value decreases and then increases through limits that are set dynamically according to the overall amplitude of the signal (dotted lines indicate upper and lower limits). Each detected breath onset is indicated by a breath mark. A similar process is used for the Orient speck signal (middle trace). If the cannula and Orient speck marks are within preset limits, they are considered to represent measures of the same breath and a match is declared (bottom trace). The durations of the two breaths are then compared.
British Journal of Anaesthesia  , DOI: ( /bja/aer153)
Copyright © 2011 The Author(s) Terms and Conditions

4. Fig 3
An example of a difficult analysis. A period of airway obstruction is followed by recovery. Nasal flow (cannula signal, upper trace) is small, and leads to a period of increased flow probably associated with arousal. Breath duration transiently increases and frequency is then increased. An opposite effect is seen with the Orient speck signal: movements are greater during obstruction. During this time, the signals from the Orient speck cannot be matched with corresponding marks on the nasal cannula signal and gaps appear in the matching (bottom trace).
British Journal of Anaesthesia  , DOI: ( /bja/aer153)
Copyright © 2011 The Author(s) Terms and Conditions

5. Fig 4
(a) Definition of the time periods used to compare matched signals, and unmatched data used to analyse respiratory rates from each epoch. (b) Data from analysis of signals available in each 5 min epoch to generate a plot similar to a ward chart.
British Journal of Anaesthesia  , DOI: ( /bja/aer153)
Copyright © 2011 The Author(s) Terms and Conditions

6. Fig 5
Consistency of epoch measurements. (a) A typical ‘nursing chart plot’ indicating the 5% and 95% confidence intervals of the measures, which are sufficiently close to give clinical confidence. (b) The 95% confidence range for the subjects studied showing one outlier (circled). (c) The time plot for this subject showing a trend to a lower rate. (d) A sample of the nasal cannula signal taken from this period confirms a reduced rate.
British Journal of Anaesthesia  , DOI: ( /bja/aer153)
Copyright © 2011 The Author(s) Terms and Conditions