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.
Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles / M. A. Kenfack; F. Lador; M. Licker; C. Moia; E. Tam; C. Capelli; D. Morel; G. Ferretti. - In: CLINICAL SCIENCE. - ISSN 0143-5221. - STAMPA. - 106:(2004), pp. 365-369.
Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles
TAM, ENRICO;
2004
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
