Study on in Vitro Accurate Measurement Method of PICC Insertion Depth

Objective to study an in vitro accurate measurement method for the placement depth of PICC. Methods 270 patients undergoing PICC catheterization under ultrasound guidance in outpatient PICC catheterization from March to September 2019 were selected by convenient sampling. By using the random number table method, the subjects were divided into group A (horizontal L-type measurement method) and Group B (characteristic index measurement calculation) by 1:1, with 135 cases in each group. X-ray chest radiograph was taken after catheterization in both groups, and the indwelling position of the catheter was adjusted according to the X-ray chest radiograph. The correlation between PICC predicted length and ideal depth and patient satisfaction were compared between the two groups. Results The success rate of PICC catheter tip insertion in group B was 97.78%, while that in control group A was 82.22%, the difference was statistically significant (P < 0.05). The satisfaction degree of patients in group B was significantly higher than that in group A. The differences were statistically significant (P < 0.05). Conclusion Improving the success rate of the precise depth of PICC catheter placement can significantly reduce the incidence of complications, waste of human and material resources caused by adjusting the catheter position, and significantly improve patient satisfaction.


Introduction
100%. The 2016 American Academy of Intravenous Care Guidelines recommends that the optimal location of the PICC catheter tip is in the lower third segment of the superior vena cava, near the junction of the superior vena cava and the right atrium (CAJ) [2] [3]. After successful catheterization, X-ray chest radiography is the gold standard for determining the location of the PICC tip.
The location of the PICC tip is very important. If the catheterization position is too shallow or too deep, it is likely to cause catheterization related complications, such as phlebitis, catheter blockage, thrombosis, and arrhythmia [4] [5] [6]. So the depth control of PICC catheter placement is the key. At present, the length of PICC catheter placement in clinical practice is mainly determined by the body surface measurement method, with single indicators and inaccurate results. The effect of PICC placement is very dependent on the experience of the operator. There are several in vitro measurement methods commonly used in China. The length of the chest radiograph combined with body surface measurement formula [7] is not suitable for patients who have not taken a chest radiograph before catheterization. L-type measurement method [8] [9]: The patient was in a supine position with the arm extended 90˚, and the puncture point to the right sternoclavicular joint was used to reflexion downward to the third intercostal space. However, this method made the patients more exposed, and the difference was large for obese patients. The length of the brachiocephalic veins on both sides was inconsistent, which affected the accuracy of the length of catheterization. Caliper (formula) measurement method [10]

Intervention Methods
All the selected patients were given catheterization in accordance with the standard procedure of PICC catheterization under the guidance of ultrasound: accurate height and weight were asked or measured for the patient; Group A (horizontal L-type measurement) : the patient was placed in the supine position, the arm abduction was measured by catheterization at A 90˚ Angle with the trunk, and the arm abduction was measured from the pre-puncture point to the right sternoclavicular joint and then reflexes downwards to the 3rd intercostal space.

1) Correlation between predicted length and ideal depth in patients: After ca-
theterization, X-ray chest radiograph was taken to determine that the PICC catheter tip was located in the lower 1/3 section of the superior vena cava, near the junction of the superior vena cava and the right atrium (CAJ), and the ideal location was determined.
2) PICC catheter tip location: the catheter tip may be located in the jugular vein, with subclavicular or axillary vein reflexes, or the catheter tip may be too shallow to reach the superior vena cava or the inferior segment of the superior vena cava. The catheter tip is located too deep beyond the junction of the superior vena cava and the right atrium into the right atrium (Table 2).
3) Patient satisfaction: The evaluation is carried out in the form of questionnaire, which is filled in by patients themselves or with the assistance of nurses.
There are 10 items in the questionnaire, and each item has 4 options: very satisfied, satisfied and dissatisfied. The total satisfaction rate = (very satisfied cases + satisfied cases)/total cases × 100% (Table 3).  6) Tip positioning: after the catheterization is completed, take X-ray chest radiograph to determine.

Statistical Methods
EpiData3.1 software was used to input the data, and the data was analyzed by SPSS17.0 statistical software. Measurement data were expressed as mean ± standard deviation, t-test was used, enumeration data were expressed as cases and percentage, X 2 test was used. Rank sum test was used for grade data, and P < 0.05 was considered statistically significant.

1)
Develop an in vitro measurement depth calculation model, which can more accurately describe the physical characteristics of patients, reduce the significant measurement deviation caused by subjective factors of nurses, and improve the accuracy of catheters depth.
2) Develop an in vitro measurement depth calculation model to provide theoretical basis for clinical application.
3) On the basis of the system and model, continuous feedback adjustment and optimization can be carried out through the measurement statistics of data, so as 4) The results of this study showed that the success rate of improving the precise depth of PICC catheter insertion in the observation group was significantly higher than that in the control group, indicating that the measurement and calculation method of characteristic indicators adopted by the observation group was significantly better than the current transverse L-shaped measurement method; It can significantly reduce the incidence of complications, waste of human and material resources caused by adjusting the catheter position, and significantly improve patient satisfaction.
To sum up, the characteristic indexes measuring method is superior to the method for measuring the horizontal l-shaped, have more advantages, can be