ISSN:
1573-2614
Keywords:
Monitoring
;
blood pressure
;
Equipment
;
transducers
;
Measurement techniques
;
manometry
Source:
Springer Online Journal Archives 1860-2000
Topics:
Computer Science
,
Medicine
Notes:
Abstract The accuracy of invasive arterial blood pressure monitoring is dependent on an adequate damped natural frequency (DNF) and damping factor (DF) of the system. Several factors influencing the DNF and DF were investigated to determine requirements for optimal design of catheter-manometer systems. The frequency sweep method was used in a specially constructed chamber that included linearizing and compensation circuitry. The DNF of isolated 20-gauge cannulae varied from 35.1 to 47.7 Hz. The DNF of 24-gauge cannulae varied from 27.7 to 44.3 Hz. An arterial cannula was found to require a DNF above 40 Hz to prevent the DNF from decreasing to below 25 Hz with the addition of arterial pressure tubing. Arterial pressure tubings exceeding 300 mm in length had DNF values that were unacceptably low even before the addition of arterial cannulae (e.g., the DNF was 23.8 Hz for a 900-mm tubing length, 19.8 Hz for 1,000-mm length, and ranged from 12.9 to 21.4 Hz for 1,200-mm lengths). The 3-way stopcocks and continuous flush devices further decreased the DNF, especially when the diameters were not matched. The percentage decrease caused by 3-way stopcocks and flush devices ranged between 19.5 and 40.8% for 300-mm length tubings and between 2.3 and 25.8% for tubings of 1,200-mm lengths. The radius ratio (outside diameter divided by inside diameter) is introduced as a new method to express the stiffness of arterial pressure tubing. A weak correlation was found between DNF and radius ratio (r=0.37,p=0.026 for 300-mm tubing andr=0.57,p=0.0095 for 1,200-mm tubing). The influence of temperature changes from 25 to 37°C on the DNF for the entire catheter-manometer system was minimal and ranged from an increase of 1.2 Hz to a decrease of 1.7 Hz. It is not possible to predict the exact DNF and DF of a complete catheter-manometer system from a knowledge of the values for the individual constituents, and new combinations should be tested before being placed in use. The items chosen for an optimal catheter-manometer system should ideally consist of a 300-mm arterial pressure tubing, stopcocks, and flush devices with internal diameters matched to the tubing and an arterial cannula with a known DNF and DF, especially avoiding cannulae with flow control devices.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01627636
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