© GB Smith 2007 Radar-based breathing rate monitoring: manikin + human volunteer study Dave Parry 1 Gary Smith 2 Sheena Farrell 2 David Prytherch 2 Nicholas Hirsch 3 Sarah Harrison 2 Lynsey Woodward 2 University of Portsmouth 1 Portsmouth Hospitals NHS Trust 2 National Hospital for Neurology & Neurosurgery 3

© GB Smith 2007 Breathing rate  should be routine component of clinical monitoring  is difficult to measure  affected by many clinical states  important predictor of cardiopulmonary arrest, death and readmission to a critical care unit  importance and usefulness often underestimated by clinicians  poor level of breathing rate recording in general hospital wards

© GB Smith 2007 Potential benefits of continuous monitoring of breathing rate Breathing rate continuous monitoring Nurse Time Nurse

© GB Smith 2007 Radar-based breathing rate monitoring

© GB Smith 2007 Laerdal BedAlert  device development funded by Laerdal Medical  resources provided by Laerdal Medical  research undertaken jointly by Portsmouth Hospitals NHS Trust and University of Portsmouth

© GB Smith 2007 Laerdal BedAlert

© GB Smith 2007 Radar head unit PC Controller 1.7 metres Network cable Laerdal BedAlert: arrangement of study components

© GB Smith 2007 Laerdal BedAlert: manikin study  simulation study  breathing rate recorded by the BedAlert vs that of an intubated, human manikin lying supine on a standard bed, ventilated using a positive pressure ventilator  measurements were taken at ventilator tidal volumes mls  manikin breathing rates varied from 5 to 45 breaths/minute in steps of 5 breaths/minute  each manikin breathing rate kept constant for 5 minutes  average value of the BedAlert breathing rate recorded

© GB Smith 2007 Laerdal BedAlert: manikin study BedAlert breathing rate (bpm) Manikin breathing rate (bpm) n = 52

© GB Smith 2007 Bland Altman plot of results for all tidal volumes combined Manikin – BedAlert breathing rate Ventilator-driven manikin breathing rate Laerdal BedAlert: manikin study Mean difference (bias) = bpm SD of the difference (precision) = Limits of agreement = to bpm

© GB Smith 2007 Tidal Volume RangeBiasPrecisionLimits of Agreement Low ( ml) to Medium ( ml) to High ( ml) to Laerdal BedAlert: manikin study

© GB Smith 2007 Laerdal BedAlert: manikin study  the BedAlert radar system gives a clinically acceptable agreement in breathing rate with that of a ventilator- driven human manikin.  no obvious influence of tidal volume on measured breathing rate  in 2002 Lim et al showed inter and intra-observer limits of agreement of +4.4 to -4.2 breaths per minute (experienced clinical staff vs experienced clinical staff).

© GB Smith Radar-based respiratory rate monitoring Human volunteer study

© GB Smith 2007 Laerdal BedAlert: human volunteer study 6 human volunteers computer metronome played repetitive tone at set rate tone rate 5 – 35 breaths/minute tone maintained for 2 minutes at each stage breathing rate simultaneously recorded by BedAlert. studied in 4 different positions

© GB Smith 2007 Radar head unit PC Controller 1.7 metres Network cable Laerdal BedAlert: arrangement of study components

© GB Smith 2007 Laerdal BedAlert: human volunteer study Tone rate (bpm) BedAlert breathing rate (bpm) n = 2105

© GB Smith 2007 Bland Altman plot of results for all positions Tone rate – BedAlert breathing rate Mean difference (bias) = bpm SD off the difference (precision) = Limits of agreement = to bpm Laerdal BedAlert: human volunteer study

© GB Smith 2007 Laerdal BedAlert: human volunteer study Bias, precision and limits of agreement for the positions studied PositionBiasPrecisionLimits of Agreement Prone to Sitting to Right lateral decubitus to Supine to +0.50

© GB Smith 2007 Laerdal BedAlert: summary accurate painless non-invasive safe radar-based method of measuring breathing rate potential benefits of continuous monitoring requires minimal human resources next steps