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Accuracy of invasive arterial pressure monitoring in cardiovascular patients: an observational study.

Romagnoli S, Ricci Z, Quattrone D, Tofani L, Tujjar O, Villa G, Romano SM, De Gaudio AR - Crit Care (2014)

Bottom Line: Invasive pressure values were then compared with the non-invasive ones.Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena.NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. stefano-romagnoli@hotmail.com.

ABSTRACT

Introduction: Critically ill patients and patients undergoing high-risk and major surgery, are instrumented with intra-arterial catheters and invasive blood pressure is considered the "gold standard" for arterial pressure monitoring. Nonetheless, artifacts due to inappropriate dynamic response of the fluid-filled monitoring systems may lead to clinically relevant differences between actual and displayed pressure values. We sought to analyze the incidence and causes of resonance/underdamping phenomena in patients undergoing major vascular and cardiac surgery.

Methods: Arterial pressures were measured invasively and, according to the fast-flush Gardner's test, each patient was attributed to one of two groups depending on the presence (R-group) or absence (NR-group) of resonance/underdamping. Invasive pressure values were then compared with the non-invasive ones.

Results: A total of 11,610 pulses and 1,200 non-invasive blood pressure measurements were analyzed in 300 patients. Ninety-two out of 300 (30.7%) underdamping/resonance arterial signals were found. In these cases (R-group) systolic invasive blood pressure (IBP) average overestimation of non-invasive blood pressure (NIBP) was 28.5 (15.9) mmHg (P <0.0001) while in the NR-group the overestimation was 4.1(5.3) mmHg (P < 0.0001). The mean IBP-NIBP difference in diastolic pressure in the R-group was -2.2 (10.6) mmHg and, in the NR-group -1.1 (5.8) mmHg. The mean arterial pressure difference was 7.4 (11.2) mmHg in the R-group and 2.3 (6.4) mmHg in the NR-group. A multivariate logistic regression identified five parameters independently associated with underdamping/resonance: polydistrectual arteriopathy (P = 0.0023; OR = 2.82), history of arterial hypertension (P = 0.0214; OR = 2.09), chronic obstructive pulmonary disease (P = 0.198; OR = 2.61), arterial catheter diameter (20 vs. 18 gauge) (P < 0.0001; OR = 0.35) and sedation (P = 0.0131; OR = 0.5). The ROC curve for the maximal pressure-time ratio, showed an optimum selected cut-off point of 1.67 mmHg/msec with a specificity of 97% (95% CI: 95.13 to 99.47%) and a sensitivity of 77% (95% CI: 67.25 to 85.28%) and an area under the ROC curve by extended trapezoidal rule of 0.88.

Conclusion: Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena. NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.

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Related in: MedlinePlus

Fast-flush test. Amplitude ratio (AR): A2 (3 mm)/A1 (7 mm) = 0.43. The corresponding damping coefficient is 0.28 [9]. P identifies the period (peak-to-peak distance) necessary for the natural frequency calculation: paper speed/P. In the example, 25 (mm/sec)/2 mm = 12.5 Hz; these data can be then plotted into the diagram showed in Figure 3. N: normal QRS complex.
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Fig2: Fast-flush test. Amplitude ratio (AR): A2 (3 mm)/A1 (7 mm) = 0.43. The corresponding damping coefficient is 0.28 [9]. P identifies the period (peak-to-peak distance) necessary for the natural frequency calculation: paper speed/P. In the example, 25 (mm/sec)/2 mm = 12.5 Hz; these data can be then plotted into the diagram showed in Figure 3. N: normal QRS complex.

Mentions: A standard procedure was used for all measurement collection. First, the arterial pressure transducer was leveled and zeroed to the intersection of the anterior axillary line and the fifth intercostal space. The investigators then purged the system of any air bubble with a dedicated inflated flush system set at 300 mmHg. Second, invasive systolic blood pressure (Sys-IBP), diastolic blood pressure (Dia-IBP), and mean blood pressure (Mean-IBP) were measured by means of a radial artery catheter (Leadercath Arterial polyethylene catheter - 18 gauge, 10 cm length, 0.8 mm internal diameter × 1.2 mm external diameter or 20 gauge, 8 cm length, 0.6 mm internal diameter × 0.9 mm external diameter; Vygon, Ecouen, France), connected to a disposable pressure transducer (Package transducer Edwards; VAMP Plus system; Edwards Lifesciences, Irvine, CA, USA) and measured with a Philips MP60 IntelliVue monitor (Philips Medical System; Best,The Netherlands). The signal was then directed via the analogic output to a MostCare® pulse contour hemodynamic monitoring system (Vygon, Vytech Health, Padova, Italy) in order to measure the dP/dtMAX. This ratio represents the maximal rate of pressure change over time between two consecutive points during the systolic upstroke recorded at 1000 Hz: in a previous study [10] this parameter was shown to be significantly higher in underdamped/resonant signals that in non-affected waveforms. Moreover, the analog pressure signals were digitized using a multifunction board (Multifunction Analog and Digital Board RTI-800, Analog-Devices, Norwood, MA, USA), and recorded on a personal computer (LTE5000, Compaq, Houston, TX, USA) for fast-flush test registration and analysis [11] (Figure 1). The fast-flush test is the only one that allows clinicians to evaluate, the appropriateness of the dynamic response of the blood pressure measuring system at the bedside. The Fn and the damping coefficient (β) must be measured. The test is described elsewhere in details [9]: briefly, it is performed by flushing saline with high pressure (300 mmHg) via the flush system of the transducer. This, generates an undershoot and overshoot of waves that will decay exponentially in accordance with the β. The natural frequency (Fn) can be measured by dividing the paper speed (for example, 25 mm/sec) by the wavelength or period (peak to peak distance in mm) generated by the flush (Figure 2). Damping (anything that reduces energy in an oscillating system) will reduce the amplitude of the oscillations and some degree of damping is required in all systems (for example, friction in the fluid pathway). The β can be derived from the amplitude ratio (AR) of two consecutive resonant waves. AR is calculated by dividing the smaller wave (second) by the higher one (first) (Figure 2). Once the AR is measured, the corresponding β is then taken from charts [9]. Finally, the Fn and the AR or the corresponding β can be plotted in a specific graph that shows three areas: adequate dynamic response, overdamping, underdamping [9] (Figure 3).Figure 1


Accuracy of invasive arterial pressure monitoring in cardiovascular patients: an observational study.

Romagnoli S, Ricci Z, Quattrone D, Tofani L, Tujjar O, Villa G, Romano SM, De Gaudio AR - Crit Care (2014)

Fast-flush test. Amplitude ratio (AR): A2 (3 mm)/A1 (7 mm) = 0.43. The corresponding damping coefficient is 0.28 [9]. P identifies the period (peak-to-peak distance) necessary for the natural frequency calculation: paper speed/P. In the example, 25 (mm/sec)/2 mm = 12.5 Hz; these data can be then plotted into the diagram showed in Figure 3. N: normal QRS complex.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4279904&req=5

Fig2: Fast-flush test. Amplitude ratio (AR): A2 (3 mm)/A1 (7 mm) = 0.43. The corresponding damping coefficient is 0.28 [9]. P identifies the period (peak-to-peak distance) necessary for the natural frequency calculation: paper speed/P. In the example, 25 (mm/sec)/2 mm = 12.5 Hz; these data can be then plotted into the diagram showed in Figure 3. N: normal QRS complex.
Mentions: A standard procedure was used for all measurement collection. First, the arterial pressure transducer was leveled and zeroed to the intersection of the anterior axillary line and the fifth intercostal space. The investigators then purged the system of any air bubble with a dedicated inflated flush system set at 300 mmHg. Second, invasive systolic blood pressure (Sys-IBP), diastolic blood pressure (Dia-IBP), and mean blood pressure (Mean-IBP) were measured by means of a radial artery catheter (Leadercath Arterial polyethylene catheter - 18 gauge, 10 cm length, 0.8 mm internal diameter × 1.2 mm external diameter or 20 gauge, 8 cm length, 0.6 mm internal diameter × 0.9 mm external diameter; Vygon, Ecouen, France), connected to a disposable pressure transducer (Package transducer Edwards; VAMP Plus system; Edwards Lifesciences, Irvine, CA, USA) and measured with a Philips MP60 IntelliVue monitor (Philips Medical System; Best,The Netherlands). The signal was then directed via the analogic output to a MostCare® pulse contour hemodynamic monitoring system (Vygon, Vytech Health, Padova, Italy) in order to measure the dP/dtMAX. This ratio represents the maximal rate of pressure change over time between two consecutive points during the systolic upstroke recorded at 1000 Hz: in a previous study [10] this parameter was shown to be significantly higher in underdamped/resonant signals that in non-affected waveforms. Moreover, the analog pressure signals were digitized using a multifunction board (Multifunction Analog and Digital Board RTI-800, Analog-Devices, Norwood, MA, USA), and recorded on a personal computer (LTE5000, Compaq, Houston, TX, USA) for fast-flush test registration and analysis [11] (Figure 1). The fast-flush test is the only one that allows clinicians to evaluate, the appropriateness of the dynamic response of the blood pressure measuring system at the bedside. The Fn and the damping coefficient (β) must be measured. The test is described elsewhere in details [9]: briefly, it is performed by flushing saline with high pressure (300 mmHg) via the flush system of the transducer. This, generates an undershoot and overshoot of waves that will decay exponentially in accordance with the β. The natural frequency (Fn) can be measured by dividing the paper speed (for example, 25 mm/sec) by the wavelength or period (peak to peak distance in mm) generated by the flush (Figure 2). Damping (anything that reduces energy in an oscillating system) will reduce the amplitude of the oscillations and some degree of damping is required in all systems (for example, friction in the fluid pathway). The β can be derived from the amplitude ratio (AR) of two consecutive resonant waves. AR is calculated by dividing the smaller wave (second) by the higher one (first) (Figure 2). Once the AR is measured, the corresponding β is then taken from charts [9]. Finally, the Fn and the AR or the corresponding β can be plotted in a specific graph that shows three areas: adequate dynamic response, overdamping, underdamping [9] (Figure 3).Figure 1

Bottom Line: Invasive pressure values were then compared with the non-invasive ones.Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena.NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. stefano-romagnoli@hotmail.com.

ABSTRACT

Introduction: Critically ill patients and patients undergoing high-risk and major surgery, are instrumented with intra-arterial catheters and invasive blood pressure is considered the "gold standard" for arterial pressure monitoring. Nonetheless, artifacts due to inappropriate dynamic response of the fluid-filled monitoring systems may lead to clinically relevant differences between actual and displayed pressure values. We sought to analyze the incidence and causes of resonance/underdamping phenomena in patients undergoing major vascular and cardiac surgery.

Methods: Arterial pressures were measured invasively and, according to the fast-flush Gardner's test, each patient was attributed to one of two groups depending on the presence (R-group) or absence (NR-group) of resonance/underdamping. Invasive pressure values were then compared with the non-invasive ones.

Results: A total of 11,610 pulses and 1,200 non-invasive blood pressure measurements were analyzed in 300 patients. Ninety-two out of 300 (30.7%) underdamping/resonance arterial signals were found. In these cases (R-group) systolic invasive blood pressure (IBP) average overestimation of non-invasive blood pressure (NIBP) was 28.5 (15.9) mmHg (P <0.0001) while in the NR-group the overestimation was 4.1(5.3) mmHg (P < 0.0001). The mean IBP-NIBP difference in diastolic pressure in the R-group was -2.2 (10.6) mmHg and, in the NR-group -1.1 (5.8) mmHg. The mean arterial pressure difference was 7.4 (11.2) mmHg in the R-group and 2.3 (6.4) mmHg in the NR-group. A multivariate logistic regression identified five parameters independently associated with underdamping/resonance: polydistrectual arteriopathy (P = 0.0023; OR = 2.82), history of arterial hypertension (P = 0.0214; OR = 2.09), chronic obstructive pulmonary disease (P = 0.198; OR = 2.61), arterial catheter diameter (20 vs. 18 gauge) (P < 0.0001; OR = 0.35) and sedation (P = 0.0131; OR = 0.5). The ROC curve for the maximal pressure-time ratio, showed an optimum selected cut-off point of 1.67 mmHg/msec with a specificity of 97% (95% CI: 95.13 to 99.47%) and a sensitivity of 77% (95% CI: 67.25 to 85.28%) and an area under the ROC curve by extended trapezoidal rule of 0.88.

Conclusion: Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena. NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.

Show MeSH
Related in: MedlinePlus