Keywords

1 Introduction

Pressure ulcers are skin and/or underlying tissue lesions caused by the limitation of blood circulation owing to the combination of increased pressure, friction, and sheer force on specific parts of the body [1, 2]. These pressure injuries are closely related to loss of quality of life, impairment in mobility, and increased mortality, both directly and indirectly [3].

Repositioning patients every 2 h (q2hr) to prevent continuous high pressure on a specific body part is the mainstream of pressure sore care, and it has been considered a guideline for general patient care [4, 5]. However, previous studies have shown that standard turning does not sufficiently relieve the high skin-bed pressure on peri-sacral areas, such as the sacrum, coccyx, and ischial tuberosity, even in non-disabled adult subjects. This may explain why pressure ulcers still develop despite preventive methods, including regular patient repositioning [6]. In addition, recording repositioning has not been standardized or automated, and remains manual. This causes a lack of optimal repositioning and incomplete documentation of a patient’s position.

Several studies have focused on a preventive solution for pressure ulcers with real-time position monitoring systems. In particular, devices that use sensors to detect pressure are considered to be one of the most effective methods because they minimize care-giver's effort [7]. It is also important because there has been issues about the pressure monitoring while sleeping. Furthermore, these devices used to modify care plans while preventing the development of pressure ulcers [8]. Comprehensive understanding of the monitoring information gathered from devices is necessary to increase optimal patient repositioning by clinical staff. An integrated analysis is needed between pressure monitoring information and known positions to prevent pressure ulcers.

There is a lack of research evaluating pressure measurements in various positions considering the risk areas of each position. This study aimed to clarify the key clinical implications for preventing pressure ulcers by quantitatively analyzing acquired pressure parameters in high-risk areas depending on position.

2 Materials and Methods

2.1 Study Design

In this study, we retrospectively analyzed the clinical records of trials conducted on a multi-actuated bed with an applied pressure sensor. From August to September 2022, the clinical records of 20 healthy individuals were obtained. The inclusion criteria were: 1) over 18 years of age, 2) no underlying disease, and 3) no limitations on activity. The reviewed data were recorded in a structured form. Additionally, we collected demographic data such as age, gender, height, weight, and body mass index (BMI).

This study was approved by the Institutional Review Board of Korea University Guro Hospital (2022GR0463).

2.2 Pressure Sensing with Multi-actuated Bed

A calibrated XSENSOR IX500:256.256.22 (XSENSOR Technology Corporation, Calgary, Canada) pressure mapping system with X3 software (v8) was used. XSENSOR is considered the gold standard for pressure mapping and has been used in several studies [5, 9, 10]. The XSENSOR mat consists of 65,536 sensing points, has a total area of 63.5 cm × 53.3 cm and a sensing area of 29.5 cm × 29.5 cm. The manufacturer’s specifications state that the pressure mat showed high durability in subsurface testing, an accuracy rate of ±10% of the calibrated values, a sampling frame rate of 6.2 frames per second, and a spatial resolution of 1.15 mm. The device was calibrated to measure pressure from 0 to 200 mmHg. IP readings were transferred from the XSENSOR mat to a handheld monitor.

A modern automatic bed setting (Jeong In ENS Corporation, Republic of Korea) was used in conjunction with the XSENSOR mat. Repositioning to the lateral tilt (i.e., turning) position and supine position are the most routine methods for patients’ position change [11]. The multi-actuated bed supported three standard positions for the prevention of pressure ulcers: right-side tilt, 30°; left-side tilt, 30°; and supine [12].

Fig. 1.
figure 1

Illustration of three different position with measurement. (a) is side-tilt 30° position, (b) is supine position and (c) is example of pressure sensing measurements.

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In particular, the side-tilt and supine positions have different high-risk areas for the development of pressure ulcers. In the supine position, pressure ulcers frequently occur at the head (occiput), bilateral shoulders (scapula), sacrum, coccyx, and bilateral heels. In the lateral tilt position, pressure ulcers easily develop in the ear, shoulder (upper humerus), elbow outer side (lateral epicondyle), hip (greater trochanter), knee outer side (fibular head), and lateral ankle outer side (lateral malleolus). [13, 14] We considered these differences regarding positioning on the evaluations and selected the most highly recorded areas in each risk area.

The sensor mat was placed above the bed, and the pressure was continuously monitored for 10 min in three positions. In total, 30 min was needed for each evaluation [5]. Recorded data included average pressure (N/cm2), peak pressure (N/cm2), minimal pressure (N/cm2), and area (cm2). The settings are illustrated in Fig. 1.

2.3 Statistical Analysis

Using the Wilcoxon signed-rank test, the quantitative difference between pressure parameters depending on the risk areas of each position was analyzed. For the descriptive analysis, the median and inter-quarter range of measurements were suggested for metric evaluations. SPSS version 26.0 software (SPSS Inc., Chicago, IL, USA) was used for all analyses, with the statistical significance level set at p < 0.05.

3 Results

Ten patients were male and 10 were female. The median age of participants was 28 years (25.25–31.5); median height was 167.0 cm (162.0–172.75); median weight was 63.5 kg (50.25–70.0); and median BMI was 21.12 kg/m2 (18.75–23.87).

3.1 Pressure Measurements at Risk Area of Supine Position

The pressure parameters in the supine position in high-risk areas are listed in Table 1. All four pressure measurements of the head and bilateral shoulders, right heel; coccyx and left heel, right heel were different. Pressure measurements of the head and left heel were different, except for average pressure. The pressure measurements of the sacrum and right heel were different, except for maximal pressure. Pressure measurements of the left shoulder and left heel; right shoulder and left heel; sacrum and left heel were different, except for minimal pressure. Pressure measurements of the left shoulder and sacrum, coccyx; right shoulder and sacrum, coccyx; sacrum and coccyx were different, except in the area. The average and minimal pressures of the left and right shoulders were different. The maximal pressure and areas of the head and coccyx; left shoulder and right heel were different. The areas of the right shoulder and right heels were different. There was no statistically significant differences between the right and left heels.

Table 1. At-risk area of pressure ulcer in supine position.
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3.2 Pressure Measurements at Risk Area of Right Side-Tilt Position

The pressure measurements in the side-tilt position to the right in the high-risk areas are presented in Table 2. All four pressure measurements of the ear and shoulder, elbow, knee, ankle; shoulder and knee, ankle; elbow and hip; hip and knee, ankle were different. The pressure measurements of the ear and hip were different, except for maximal pressure. The pressure measurements of the shoulder and elbow were different, except for minimal pressure. The pressure measurements of the shoulder and hip were different, except for the area. The minimal pressures and areas of the knee and ankle were different. The minimal pressures at the elbow and ankle were different. The elbow and knee areas were different.

3.3 Pressure Measurements at Risk Area of Left Side-Tilt Position

The pressure measurements in the side-tilt position to the left in high-risk areas are also presented in Table 2. All four pressure measurements of the shoulder and knee; elbow and hip; hip and knee, ankle were different. The pressure measurements of the ear and hip were different, except for maximal pressure. The pressure measurements of the ear and shoulder, elbow, knee, ankle; shoulder and elbow; knee and ankle were different, except for minimal pressure. Pressure measurements of the shoulder and hip were different, except for the area. The maximal pressure and area of the shoulder and ankle were different. The elbow and knee areas were different. There was no statistically difference between the elbow and the ankle.

Table 2. At-risk area of pressure ulcer in side-tilt position.
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3.4 Pressure Change Depending on Position

To detect the pressure change depending on positions, we compared the areas with anatomical rotation. We matched the followings: head (occiput) on supine position and bilateral ears on side-tilt position, bilateral shoulder on supine position and bilateral shoulders on side-tilt position, sacrum on supine position and bilateral hip on side-tilt position, bilateral heel on supine position and bilateral lateral ankle on side-tilt position.

Compared to the pressure on head (occiput) in supine position, average pressure was stationary on right ear and decreased on left ear. Also, maximal and minimal pressure were decreased on right ear and increased on left ear, respectively. In comparison of the pressure on bilateral shoulder in supine position and side-tilt position, average and maximal pressure were increased on right side-tilt shoulder; and minimal pressure was decreased on right side-tilt shoulder. In addition, maximal pressure was increased on left side-tilt shoulder; average pressure and minimal pressure were decreased on left side-tilt shoulder. Compared to the pressure on sacrum in supine position, all pressure parameters were increased on right hip. Also, average and minimal pressure were increased and maximal pressure was decreased on left hip. In comparison between the pressure on bilateral heal in supine position and bilateral lateral ankle in side-tilt position, all pressure parameters were decreased on bilateral side-tilt positions.

4 Discussion

Position change for reducing pressure and preventing ulcers have been the standard methods of patient care [1, 12, 15, 16]. However, studies showed failure in reducing the incidence of pressure ulcers [15, 18,19,20]. Although maintaining the skin contact pressure below 32 mmHg is expected to decrease the possibility of developing pressure ulcers, the effectiveness of repositioning patients for pressure sore prevention remains unclear [6].

Previous studies conducted with non-disabled population and pressure mapping system [5, 6]. They emphasized the high-risk of pressure area as peri-sacral area and greater trochanters. Our research was the first study which quantitively tracked the pressure parameters with position change and describe the clear pressure difference between each high-risk pressure ulcer areas. Furthermore, we clarified the importance of frequent position change in patient care for preventing pressure ulcers.

Depending on the position, various findings were observed with quantitative measurements. In the supine position, the average, maximal, and minimal pressure measurements were higher on the head, sacrum, and coccyx than on the shoulder and heel. This might be due to the bilateral distribution of body weight in the shoulder and heel. In the right and left side-tilt positions, we compared the right side and the left side of the body, respectively. The average, maximal, and minimal pressure measurements were higher on the bilateral ear than on the bilateral shoulder and elbow on the upper side of the body. In addition, these three pressure parameters appeared to be higher on the bilateral hip than on the bilateral knee and lateral ankle on the lower side of the body.

Although there were minor differences in the composition of pressure measurements with statistical significance, we clarified the clear differences between pressure values in each risk area. In the supine position, most pressure parameters of the head, shoulder, sacrum, coccyx, and both heels showed significant differences, except between the right and left heels. In addition, in the right side-tilt position, all pressure measurements of the ear, shoulder, elbow, hip, knee, and lateral ankle were significantly different. In the left side-tilt position, most of the pressure parameters of the ear, shoulder, elbow, hip, knee, and lateral ankle were significantly different, except between the elbow and ankle. The difference between right-side tilt and left-side tilt might be explained by the small amount of recruited data, and it would be expected to be covered by larger scale analysis.

In comparing descriptive measurements with positional rotation, the changes in pressure parameters at each high-risk area did not show a consistent pattern. This result suggest that it is more important to change the posture frequently than to make an ideal posture in patient care for preventing pressure ulcers.

This study has some limitations. First, the pressure measurement by the sensor did not directly express the exact pressure loading on the tissue [20]. However, pressure sensor tracking remains one of the most popular methods for pressure monitoring. The clear presentation of pressure change in real time reflects a good representation of the pressure on the surface of the skin. Therefore, it allows us to intuitively recognize the increasing and decreasing pressures. Second, we only used the measured records of participants with a single brand of modern ward bed and sensor monitoring interface. However, we expected that the results would be similar, regardless of the type of hardware system. The pressure measurements at various positions are expected to be different for different beds/sensor mats; however, there is no doubt that the general trends should be reflected in the results. Finally, we studied the data of healthy adults, but not of patients. In patients with a high risk of developing pressure ulcers, the condition of the soft tissue in the affected area is clearly different from that of the general population. Therefore, there are many variables to consider regarding the risk factors for pressure ulcers, such as nutritional status, capillary blood flow, friction force and shear force. In this point of view, we considered that healthy participants were more likely to show a clear tendency of pressure measurements in each high-risk area at different positions and positional change. Further study of patients with classified impairments is necessary, because these results with normal population may appear differently depending on the patient’s variables.

5 Conclusion

This study quantitatively examined pressure distribution depending on position and found that the risk areas for pressure ulcers in different positions have different pressure distributions in a healthy population. These findings suggest clinical implications for positioning depending on patient impairment. Further studies with a larger patient population are needed to evaluate the actual risk of developing pressure ulcers in patients and to establish positioning methods to achieve optimum status to decrease pressure ulcer risk.