What is the function of the patient monitor?

Accidents are common in intensive care medicine. One way to detect, diagnose, and treat these events is to use physiological displays that show the patient's vital signs. The monitors currently used in intensive care units (icu) provide information in digital and waveform formats, but most of these displays originated from patient monitors developed by anesthesiologists.What is a patient monitor? You may find more in this article.

The following knowledge points are listed below:

• The history of the patient monitor 

• The function of the patient monitor

1. The history of the patient monitor

In the past three decades, in high-risk areas such as aviation and power plant control, people have spent a lot of energy and resources to improve data display design. These efforts have significantly improved the safety and efficiency of aircraft and nuclear power plant operations. The common denominator in these two fields is engineering systems. All monitoring systems are designed by engineers, so their designers and operators are familiar with these systems to a certain extent. Sometimes the design goal of the system is to reduce the complexity of system monitoring. Engineering systems can be contrasted with situations where the task involves monitoring natural systems (ie patients).

One of the earliest technical means to monitor the physiology of patients was the bar chart electrocardiogram (ECG) recorder developed by Sir Thomas Lewis in 1912. What's interesting is that even today's most innovative displays still use the elements of Lewis' original bar graph and add some digital information.

The development of patient monitors stems from the need of anesthesiologists to improve patient monitoring during surgery. The currently used anesthesia monitors display more than 36 important physiological patient variables, which are usually displayed in real time through a combination of digital data and waveforms, which reflects the complexity of the monitoring task.

In the 1970s, ICU introduced physiological monitoring displays, and there has been no substantial change since then. The patient monitor still uses traditional anesthesia to present physiological variables. The design format of these displays is based on the Single Sensor Single Indicator (SSSI) method, which provides a separate indicator for each sensor connected to the patient. This monitoring method is established in the field of engineering systems1 and has been applied to patient monitoring without major modification.

2. The function of the patient monitor

The physiological parameters currently displayed on ICU patient monitors include: blood pressure obtained from arterial catheters and external pressure cuffs; blood oxygen saturation obtained from pulse oximeter; heart rate; and respiratory rate obtained from external sensors and electrocardiogram waveforms. Critically ill patients may also need to use pulmonary artery catheters for hemodynamic monitoring. The parameters obtained from the PA catheter including central venous pressure, right atrial pressure, PA pressure, cardiac output and other calculated parameters will also be displayed.

ICU nurses regularly monitor the physiological parameters of the patient to ensure the stability of the patient. One of the most common problems they face is to detect changes in one or more patients' physiological parameters. If the test results are viewed in the context of the physiological parameters and medical history of all patients, and the test results must be interpreted and compared with the parameters stored in the nurse’s recent memory or patient records, timely detection of changes will become a potential problem.

Nurses sometimes have to integrate 10 or more rapidly changing physiological parameters into a clear and qualitative mental representation of the patient’s current state. To make matters worse, in the event of an unexpected and potentially life-threatening event, as clinicians must interpret new data in order to discover problems and intervene quickly, cognitive needs increase. The high cognitive demand for data integration reduces the available cognitive resources for other important tasks (for example, taking corrective actions, recording, communicating with doctors and/or nurses). This may lead to other problems or a series of errors, such as task interruption or deviation from treatment plan or necessary interventions

Providing nurses with information about the patient's physiological state in an easy-to-understand manner of a patient monitor can reduce the time required to detect changes. However, the currently available monitors are not specifically designed as cognitive aids to quickly detect changes in patient status

The current ICU patient monitors also lack the ability to promote a comprehensive assessment of the patient's condition, which will enable nurses to develop a high level of understanding of the situation. 5 Designs that follow the SSSI method tend to generate data in sequence. The fragmented format makes it difficult and time-consuming for nurses to develop a consistent understanding of the relationship and basic mechanism of display parameters. However, this situation runs counter to the fact that a consistent understanding of the function of a system and the physiological mechanism of the patient is a necessary prerequisite for optimal results.

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