Disposable IBP Transducer Kit-Single Channel Full-time Job

Invasive intraarterial blood pressure measurement is currently the gold standard for intraoperative hemodynamic monitoring but accurate systolic blood pressure (SBP) measurement is difficult in everyday clinical practice, mostly because of problems with hyper-resonance or damping within the measurement system, which can lead to erroneous treatment decisions if these phenomena are not recognized. A hyper-resonant blood pressure trace significantly overestimates true systolic blood pressure while underestimating the diastolic pressure. Invasively measured systolic blood pressure is also significantly more affected than mean blood pressure by the site of measurement within the arterial system. Patients in the intraoperative period should be treated based on the invasively measured mean blood pressure rather than the systolic blood pressure. In this review, we discuss the pros/cons, mechanisms of Disposable IBP Transducers, and the interpretation of the invasively measured systolic blood pressure value.

Introduction & Background

Disposable IBP Transducer Kit-Single Channel is the gold standard of arterial pressure measurement in 10-20% of high-risk patients [1-2]. In the remaining 80%-90% of surgical patients, the standard intermittent non-invasive blood pressure (BP) that is obtained using oscillometry with a brachial cuff has been shown to have only poor agreement with IBP in critically ill patients [3-4]. These observed measurement differences are clinically significant because they would have triggered a change in treatment in as many as 20% of the critical care patients. Non-invasive oscillometric BP measurement with a brachial cuff tends to, on average, overestimate BP during hypotension and underestimate BP during hypertension, with a significant bias and considerable scatter. Invasive BP measurement with an arterial catheter, providing continuous BP measurements, detected nearly twice as many episodes of hypotension as intermittent oscillometric measurements with a brachial cuff [5]. Continuous rather than intermittent hemodynamic monitoring is highly desirable in high-risk patients. Even when continuous BP monitoring was accomplished in medium-risk patients with non-invasive techniques, the number of episodes of intraoperative hypotension was still reduced by half when compared to intermittent monitoring with a brachial cuff [6]. Although non-invasive continuous monitoring has fewer complications than arterial cannulation, it has not yet Disposable IBP Transducer Kit-Double Channel as the gold standard in high-risk patients, but rather serves as an alternative in low and medium-risk patients where IBP measurements are not warranted [7].

How is IBP measured?

Disposable IBP Transducer Kit-Triple Channel, in essence, replaces a small part of the wall of an artery with a stiff membrane inside a pressure transducer. To achieve this, it requires the cannulation of an artery with a stiff short catheter and the use of a short and stiff tube to connect the cannula to the transducer. In order to measure pressure, a hydrostatic reference level needs to be defined - usually, this is the level of the right atrium - and the transducer needs to be kept at the correct reference level all the time. Each component of the measurement system - transducer, hydrostatic leveling, cannula, tubing - will introduce inaccuracies or measurement errors.

Transducer

The transducer nowadays is almost always a disposable pressure transducer, which is factory-calibrated by the manufacturer. The accuracy of the disposable transducers typically is better than the accuracy required of less than ±3% or ±3 mmHg by the International Organization for Standardization/American National Standards Institution (ISO/ANSI) standard [19-20]. It needs to be zeroed, and since transducers are prone to baseline drift, this should be performed at regular intervals. In terms of quantitative error, these effects will cause a small bias of less than 3 mmHg, which is not clinically relevant in routine patient monitoring but should be considered in research or validation studies.

Leveling

The pressure transducer should be placed at heart level; by convention, this is set at the level of the right atrium. A leveling error of 10 cm will cause a measurement error of 7.4 mmHg. In clinical practice, a mean error of 3 mmHg with a standard deviation of 2 mmHg has been reported [21-22]. Again, this is probably not clinically relevant in routine patient monitoring but to be considered in research or validation studies. A more unpredictable component of leveling error is in the position changes of the operating table (rotation, tilting) where it may be difficult to maintain the proper reference position at the right atrium. It will certainly add to the overall error and is hard to quantify.

Problems occur in clinical practice when a hyper-resonant IBP Transducer Core Part trace overestimates the SBP and a surgeon decides, for example, to limit the SBP to 100 mmHg when the patient is separating from cardiopulmonary bypass (CPB). If there is insufficient damping in the system, the measured SBP will be 100 mmHg while the MAP at the same time may be too low to provide adequate coronary perfusion. The patient may then have to be placed back urgently and perhaps unnecessarily onto CPB due to the erroneous overestimation of the SBP as a result of this hyperresonance artifact. The effects of resonance and damping must therefore be carefully considered whenever making treatment decisions based on the SBP. If the trace looks hyper-resonant or over-damped, the treatment decisions should be based on the MAP. If clinicians insist on making treatment decisions based on SBP then the damping within the measurement system must first be optimized before it is safe to use SBP to guide therapy. 

The industry has recognized this potential for SBP to be overestimated as a major problem and is evaluating filtering methods for acquiring radial intra-artery BP waveforms [32]. Determining the natural frequency and damping factor of the IBP measurement system for each individual patient is, however, widely regarded as too cumbersome to find acceptance in routine clinical practice. This rather labor-intensive process is mandatory in research and validation studies that seek to measure SBP accurately [32]. Algorithms that identify erroneous invasively measured BP readings have also been developed [33].