title: Non-invasive assessment of cardiac output at rest and during exercise by finger plethysmography.
abstract: OBJECTIVE
  We sought to determine the accuracy of finger plethysmography using pulse waveform analysis with brachial calibration for measurement of cardiac output during submaximal exercise by comparing it against an acetylene (C2H2) uptake technique.
  
  
  METHODS
  The study included 24 healthy volunteers (12 males, age 35 ± 8 years). Testing was performed on an upright cycle ergometer using an incremental protocol. Cardiac output measurements were performed at rest and during sub-maximal exercise using a single breath C2H2 uptake technique and continuously using finger plethysmography with brachial calibration.
  
  
  RESULTS
  Valid results at rest and during sub-maximal exercise were achieved in 20 of 24 participants. Cardiac output at rest was 5.3 ± 1.1 and 5.2 ± 1.2 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.712. Mean difference between techniques was -0.1 ± 0.5 l min(-1). Cardiac output during submaximal exercise was 10.2 ± 2.3 and 10.3 ± 2.1 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.898. Mean difference between techniques was 0.1 ± 1.5 l min(-1). The overall correlation between finger plethysmography and C2H2 data obtained during rest and exercise was r(2) = 0.872, P<0.0001. Mean rise in cardiac output during exercise was 4.9 ± 1.5 (finger plethysmography) and 5.1 ± 1.5 l min(-1) (C2H2), P = 0.64.
  
  
  CONCLUSIONS
  Finger plethysmography determined cardiac output values both at rest and during sub-maximal exercise are comparable with those obtained using a single breath C2H2 uptake technique.
authors.affiliation: The Heart Hospital, Institute for Cardiovascular Science, University College London, London, UK. chriscritoph@doctors.org.uk
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Critoph
authors.forename: Vimal
authors.initials: V
authors.lastname: Patel
authors.forename: Bryan
authors.initials: B
authors.lastname: Mist
authors.forename: Martin D
authors.initials: MD
authors.lastname: Thomas
authors.forename: Perry M
authors.initials: PM
authors.lastname: Elliott
mesh_terms: D000114:Acetylene; D000328:Adult; D001642:Bicycling; D001916:Brachial Artery / Q000502:physiology; D001944:Breath Tests; D002138:Calibration; D002302:Cardiac Output; D015444:Exercise; D005080:Exercise Test; D005260:Female; D005385:Fingers / Q000098:blood supply*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D010991:Plethysmography / Q000592:standards; D011237:Predictive Value of Tests; D063177:Pulse Wave Analysis; D015203:Reproducibility of Results; D012146:Rest
chemical_list: D000114:Acetylene
keywords: Modelflow; acetylene uptake; cycle ergometer; haemodynamics; pulse waveform analysis