Validation of Respiration Rate Algorithms

Continuous accurate unobtrusive respiratory rate monitoring may lead to improved patient outcomes, as respiratory rate is thought to be a sensitive marker of patient deterioration. Currently systems are not suitable for long term monitoring, particularly in ambulant patients as they are too restrictive. To ensure that our algorithms are suitable for use in a clinical context we need to demonstrate their performance not only in the optimal situation, healthy volunteers at rest, but also in more challenging situations such as where the person being monitored is moving and also in patients who have conditions which may affect their physiology in such a way that the accuracy of the respiration rate estimation may be affected.

No previous study has systematically tested algorithms deriving respiratory rate from either the ECG or the photoplethysmography (PPG) waveforms in a real -world setting.

The algorithms work by looking for changes in intervals between heartbeats and also changes in the sizes of the ECG and PPG waveforms, both of which may be caused by respiration. These changes tend to diminish with increasing age and also conditions which alter the chest movement and cardiac reflexes. Thus it is important to test our algorithms' accuracy in participants exhibiting these conditions. It is also important to ensure that the calculations of respiratory rate are accurate across a range of heart rates and respiratory rates. Our testing covers all these variables.

Healthy volunteers and hospital outpatients

• Respiratory Rate
• Pulse Oximetry

• Other: Recording of 12 lead ECG
  Recording of 12 lead ECG
• Other: Recording of lying and standing blood pressure
  Recording of lying and standing blood pressure
• Other: Recording of chest wall movement
  Recording of chest wall movement
• Other: Recording of heart rate variability
  Done during deep breathing and a valsalva manoeuvre
• Other: Recording of ECG and Pulse oximeter waveform at rest
  For 10 mins
• Other: Recording of ECG and Pulse oximeter waveform during exercise
  Recording of ECG and Pulse oximeter waveform during exercise

• Young Healthy Volunteers
  Healthy volunteers under the age of 40
  Interventions:

  • Other: Recording of 12 lead ECG
  • Other: Recording of lying and standing blood pressure
  • Other: Recording of chest wall movement
  • Other: Recording of heart rate variability
  • Other: Recording of ECG and Pulse oximeter waveform at rest
  • Other: Recording of ECG and Pulse oximeter waveform during exercise
• Older healthy volunteers
  Healthy volunteers over the age of 70
  Interventions:

  • Other: Recording of 12 lead ECG
  • Other: Recording of lying and standing blood pressure
  • Other: Recording of chest wall movement
  • Other: Recording of heart rate variability
  • Other: Recording of ECG and Pulse oximeter waveform at rest
• Patients with atrial fibrillation
  Patients with permanent AF
  Interventions:

  • Other: Recording of 12 lead ECG
  • Other: Recording of lying and standing blood pressure
  • Other: Recording of chest wall movement
  • Other: Recording of heart rate variability
  • Other: Recording of ECG and Pulse oximeter waveform at rest
• Patients with a pacemaker
  Patients who have an implanted pacemaker that is continually pacing
  Interventions:

  • Other: Recording of 12 lead ECG
  • Other: Recording of lying and standing blood pressure
  • Other: Recording of chest wall movement
  • Other: Recording of heart rate variability
  • Other: Recording of ECG and Pulse oximeter waveform at rest
• Patients with restricted chest movement
  Patients whose chest expansion is less than 2.5cm
  Interventions:

  • Other: Recording of 12 lead ECG
  • Other: Recording of lying and standing blood pressure
  • Other: Recording of heart rate variability
  • Other: Recording of ECG and Pulse oximeter waveform at rest

Inclusion Criteria:

• Young Healthy Volunteers

  • Participant is willing and able to give informed consent for participation in the study.
  • Male or Female, aged between 18 and 40 years old.

• Older Healthy Volunteers

  • Participant is willing and able to give informed consent for participation in the study.
  • Male or Female, aged 70 years or above.

• Patients

  • Participant is willing and able to give informed consent for participation in the study.
  • Male or Female, aged 18-70 years old.
  • Participant has one of the following conditions:
  • Atrial fibrillation
  • A permanent pacemaker that is continuously active
  • Reduced chest wall movement

Exclusion Criteria:

• Young Healthy Volunteers

  • Any condition which might increase the risk of exercise testing
  • Any history of ischaemic heart disease
  • Any history of heart failure
  • Any structural heart disease (eg: valvular lesions, hypertrophic obstructive cardiomyopathy)
  • Any abnormalities on a resting ECG
  • Deep vein thrombosis diagnosed within the last 6 months or under active treatment
  • Uncontrolled hypertension (systolic blood pressure >220 mm Hg, diastolic >120 mm Hg)
  • Aortic aneurysm
  • Aortic or cardiovascular surgery within 6 months of recruitment
  • A family history of sudden cardiac death, congenital arrhythmia syndromes or cardiomyopathy
  • Autonomic dysfunction, either previously diagnosed or upon testing by the research team
  • Any condition involving the brain or spinal cord
  • Diabetes
  • Alcohol consumption > 21 units/week for women and 28 units/week for men or a history of previous alcohol dependence.
  • Acute kidney injury
  • Chronic kidney disease stage 4 or 5
  • Any condition causing hepatic dysfunction
  • Presence of a permanent pacemaker (these participants would be eligible for the pacemaker group)
  • Reduced chest wall movement (these participants would be eligible for the reduced chest movement group)
  • Any acute infection requiring antibiotic treatment within 3 months of recruitment
  • Any other surgery or illness requiring hospitalisation within 3 months of recruitment
  • Currently taking any medication with the exception of analgesics or the oral contraceptive pill.
  • Any wound or skin condition affecting the torso which may be affected by the application of adhesive ECG dots to the skin
  • Pregnancy
  • Inability to give informed consent

• Older Healthy Volunteers

  • Any diagnosed condition primarily affecting the cardiovascular or respiratory systems
  • Symptomatic autonomic dysfunction
  • Orthostatic hypotension
  • Any condition involving the brain or spinal cord
  • Diabetes
  • Alcohol consumption > 21 units/week for women and 28 units/week for men or a history of previous alcohol dependence.
  • Acute kidney injury
  • Chronic kidney disease stage 4 or 5
  • Any condition causing hepatic dysfunction
  • Presence of a permanent pacemaker
  • Chronic Obstructive Pulmonary Disease (COPD).
  • Any muscular dystrophy
  • Kyphosis
  • Scoliosis
  • Pectus excavatum
  • Any disease involving the lungs or pleura
  • Any acute infection requiring antibiotic treatment within 3 months of recruitment
  • Any other surgery or illness requiring hospitalisation within 3 months of recruitment
  • Currently taking any medication with the exception of analgesics or the oral contraceptive pill.
  • Any wound or skin condition affecting the torso which may be affected by the application of adhesive ECG dots to the skin
  • Pregnancy
  • Inability to give informed consent

• Patients

  • Any infection which would require isolation or barrier nursing according to the hospital's infection control policy
  • Any wound or skin condition affecting the torso which may be affected by the application of adhesive ECG dots to the skin
  • Requirement for any form of artificial ventilatory support, including oxygen therapy
  • More than one of the inclusion criteria. (ie: a patient may not have both atrial fibrillation and reduced chest wall movement and be eligible for this study)
  • Inability to give informed consent

• Engineering and Physical Sciences Research Council, UK
• University of Oxford