Modelflow®, when applied to non-invasive fingertip pulse pressure recordings, is a poor predictor of cardiac output (Q, litre·min-1). The use of constants established from the aortic elastic characteristics, which differ from those of finger arteries, may introduce signal distortions, leading to errors in computing Q. We therefore hypothesized that peripheral recording of pulse pressure profiles undermines the measurement of Q with Modelflow®, so we compared Modelflow® beat-by-beat Q values obtained simultaneously non-invasively from the finger and invasively from the radial artery at rest and during exercise. Seven subjects (age, 24.0±2.9 years; weight, 81.2±12.6 kg) rested, then exercised at 50 and 100 W, carrying a catheter with a pressure head in the left radial artery and the photoplethysmographic cuff of a finger pressure device on the third and fourth fingers of the contralateral hand. Pulse pressure from both devices was recorded simultaneously and stored on a PC for subsequent Q computation. The mean values of systolic, diastolic and mean arterial pressure at rest and exercise steady state were significantly (P<0.05) lower from the finger than the intra-arterial catheter. The corresponding mean steady-state Q obtained from the finger (Qporta) was significantly (P<0.05) higher than that computed from the intra-arterial recordings (Qpia). The line relating beat-by-beat Qporta and Qpia was y=1.55x-3.02 (r2=0.640). The bias was 1.44 litre·min-1 and the precision was 2.84 litre·min-1. The slope of this line was significantly higher than 1, implying a systematic overestimate of Q by Qporta with respect to Qpia. Consistent with the tested hypothesis, these results demonstrate that pulse pressure profiles from the finger provide inaccurate absolute Q values with respect to the radial artery, and therefore cannot be used without correction with a calibration factor calculated previously by measuring Q with an independent method.
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April 2004
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Research Article|
April 01 2004
Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles
Marcel AZABJI KENFACK;
Marcel AZABJI KENFACK
*Département de Physiologie, Centre Médical Universitaire, 1 rue Michel Servet, CH–1211 Genève 4, Switzerland
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Federic LADOR;
Federic LADOR
*Département de Physiologie, Centre Médical Universitaire, 1 rue Michel Servet, CH–1211 Genève 4, Switzerland
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Marc LICKER;
Marc LICKER
†Département d'Anesthésiologie, Pharmacologie et Soins Intensifs Chirurgicaux, Hôpital Cantonal Universitaire, Bâtiment Opéra, 1211 Genève 4, Switzerland
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Christian MOIA;
Christian MOIA
*Département de Physiologie, Centre Médical Universitaire, 1 rue Michel Servet, CH–1211 Genève 4, Switzerland
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Enrico TAM;
Enrico TAM
‡Dipartimento di Scienze e Tecnologie Biomediche, School of Medicine, P.le Kolbe 4, I-33100, Udine, Italy
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Carlo CAPELLI;
‡Dipartimento di Scienze e Tecnologie Biomediche, School of Medicine, P.le Kolbe 4, I-33100, Udine, Italy
§Microgravity, Ageing, Training, Immobility Center of Excellence, P.le Kolbe 4, I-33100, Udine, Italy
Correspondence: Dr Carlo Capelli (e-mail ccapelli@makek.dstb.uniud.it).
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Denis MOREL;
Denis MOREL
†Département d'Anesthésiologie, Pharmacologie et Soins Intensifs Chirurgicaux, Hôpital Cantonal Universitaire, Bâtiment Opéra, 1211 Genève 4, Switzerland
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Guido FERRETTI
Guido FERRETTI
*Département de Physiologie, Centre Médical Universitaire, 1 rue Michel Servet, CH–1211 Genève 4, Switzerland
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Clin Sci (Lond) (2004) 106 (4): 365–369.
Article history
Received:
September 15 2003
Accepted:
November 07 2003
Accepted Manuscript online:
November 07 2003
Citation
Marcel AZABJI KENFACK, Federic LADOR, Marc LICKER, Christian MOIA, Enrico TAM, Carlo CAPELLI, Denis MOREL, Guido FERRETTI; Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles. Clin Sci (Lond) 1 April 2004; 106 (4): 365–369. doi: https://doi.org/10.1042/CS20030303
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