A Simple Method To Repair A Supraglottic Airway Device

Background: During the perioperative period or while in the intensive care unit, the ination line is often cut accidentally during medical procedures or is damaged. As a result, it is not uncommon for a cuff leak to result in inadequate ventilation for the patient. The risk of using endotracheal tubes (ETTs) for secondary intubation is great, increasing the probability of respiratory tract infection and injury and even causing death in severe cases. The best method is to repair the damaged ETT to avoid secondary intubation and to ensure the safety of patients. Therefore, we recommend a practical and straightforward method to repair damage to the line or valve assembly of an endotracheal tube(ETT) and laryngeal mask airway (LMA). Methods: The distal end of a 22G vein (IV) catheter was inserted into the broken end of the ination line. After insertion, the internal tube was withdrawn 1 mm to restore the ination line. After 15 hours, the repaired ETT/LMA devices were tested for air leakage by measuring the pressure and load-bearing tension of the ination line. Results: There was no difference in ETTs pressure between ve intact ETTs and ve repaired ETTs (Group A, ETT, mean difference = 0.2 cmH 2 O; 95% condence interval 1.78 to 2.12 cmH 2 O; P = 0.82). When the cuff expanded to 120 cm H 2 O, there was no air leakage in the ve ETTs after repair, and the tensile strength of the ination line of the repaired ETTs in the experimental group was lower than that in the control group (each n = 5; mean difference = 33.3N; 95% condence interval, 27.5 to 39.1N; P <0.001). There was no difference in LMAs pressure (Group B, LMAs, mean difference = 0.4 cmH 2 O; 95% condence interval: -1.8 to −2.6 cmH 2 O; P = 0.67). When the cuff was expanded to 120 cmH 2 O, there was no air leakage from the ve repaired LMAs. The tensile strength of the ination line of the repaired LMAs in the experimental group was lower than that in the control group (n = 5; mean difference = −10; 95% condence interval: −14 to −5.8 N; P = 0.001). Conclusion: When the ETT, LMA ination line, or valve assembly is damaged or accidentally broken, an IV catheter can be directly inserted into the ination line to quickly and effectively repair it. It is a safe and effective emergency remedial measure, which can be widely used in the clinic.


Introduction
During the perioperative period, life-threatening emergencies can occur during anaesthetisation affecting the safety of the patient. Cuff leakage is not uncommon [1][2], and the level of pressure directly affects the prognosis and safety of patients [3][4]. Recently, a patient tore the in ation line of an ETT during resuscitation after an operation. Because the patient was not awake, there was a risk of extubating; therefore, we chose to repair it using an intravenous catheter. This method could be utilised to repair malfunctioning ETT or LMA in ation lines or incompetent valves (Fig. 1). Herein, we conducted a study to evaluate the reliability and effectiveness of this repair method in both ETTs and LMAs.

Experimental group and control group
The ETT group (group A) used 10 sets of ETTs with good performance and no air leakage of the same model and size. Five ETT sets were assigned to the experimental group and ve sets were assigned to the control group. LMA group (group B) used 10 sets of laryngeal masks with good performance and no air leakage of the same model and size. Five LMA sets were assigned to the experimental group and ve LMA sets were assigned to the control group.
In group A, a 20-ml syringe was used to stimulate the trachea. In group B, it was directly used on the LMA mold when the LMA itself was not in use. The American Kehui combined in ation/pressure gauge device was used for in ation and pressure measurements. In the experimental group, the in ation line was deliberately cut off and then the IV catheter was used to repair it. The in ation line in the control group remained intact.

Integrity test of ETT / LMA in ation pipeline
We used sensors to monitor. In group A/B, the balloon pressure of ve repaired endotracheal tubes/laryngeal masks was adjusted to 120 cmH 2 O. The test was conducted in a quiet room and the detector was zeroed before the measurements were made. The laryngeal mask was immersed in water and leaks were visually observed if bubbles were dispersed from the repaired end.
ETT/LMA airbag cuff pressure Literature suggests that a small amount of gas will be lost during an airbag pressure measurement. We conducted an airbag pressure test and found that the pressure loss is caused by the leakage of a small amount of air when the pressure gauge is directly connected to the pilot ball valve and a small amount of air enters into the pressure gauge. In order to avoid a small amount of air leakage when the pressure gauge is connected with the balloon for pressure measurements, we clamped the endotracheal tube/laryngeal mask in ation lines with the vascular forceps. The experimental group used the venous indwelling needle to carry the stop clamp. The stop clamp was closed during the pressure measurements, and then connected to the balloon pressure gauge. The stop clamp was open during pressure measurements to prevent air leakage during pressure measurement. In this test, we found that the amount of air loss positively correlated with the pressure of LMA. The greater the pressure, the more air that escaped. There is no difference in pressure measured between the experimental and control groups. Therefore, we adjusted the pressure of group A and group B to 30 cmH 2 O. After 15 hours, we reassessed the pressure of each laryngeal mask and endotracheal tube with a pressure gauge and compared the pressure changes between the experimental and control groups.

Tensile strength test of ETT/LMA in ation pipe
Tensile strength test of the in atable tube of the experimental and control groups was conducted to assess the bearing strength of the repaired end. An electronic scale was hung on a wall and, the proximal end of the in ation line of the experimental and control groups was xed with cotton thread, and the scale was rotated. At the other end, the distal end of the whole endotracheal tube/laryngeal mask in ation bag and the distal end of the repaired venous indwelling needle was held. With the increase of pressure, the weight on the electronic scale continues to increase until the in ation tube is broken or separated (Fig. 2). The weight on the electronic scale was recorded and converted to Newtons. The force required for the fracture or separation of the in ation line between the experimental and control groups was assessed by comparing the weights.

Statistical analysis
The SPSS 22 software was used for statistical analysis. The measurement data are expressed by `X ± s. The mean of two groups was compared using a t-test. P < 0.05 was considered statistically signi cant.

Results
Group A consisted of ve intact and ve repaired endotracheal tubes and pressure measurements were conducted. After 15 hours, there were no signi cant different between the pressure of the repaired endotracheal tubes and that of the intact endotracheal tubes. The air leakage experimental group was less than the control group (mean difference = 0.2 cmH 2 O; 95% con dence interval1.8-2.1cmH 2 O; P = 0.82; Fig. 3A). When the pressure was adjusted to 120 cmH 2 O, there was no visible air leakage using the water test for the ve repaired lines. The tensile strength of the repaired laryngeal mask in ation line in the experimental group was lower than that in the control group (each n = 5; mean value difference =33.3N ; 95% con dence interval, 27.5-39.1 N; P <0.001; Fig. 3B) .
Group B consisted of ve intact and ve repaired LMAs and pressure measurements were conducted.
After 15 hours, there was no signi cant difference between the pressure of an intact and repaired LMA. Further, the experimental group also had less air leakage (mean difference = 0.4 cmH 2 O; 95% con dence interval −1.8 ~ −2.6 MH, O; P = 0.67; Fig. 4A). When the pressure was adjusted to 120 cmH 2 O, the ve repaired in ation lines had no visible signs of air leakage when submerged underwater. The tensile strength of the repaired laryngeal mask in ation line in the experimental group was lower than that in the control group (each n = 5; mean difference = -10; 95% con dence interval, -14.2 ~ −5.8 n; P = 0.001; Fig. 4B). This method has been successfully used to repair in ation lines of ETTs and LMAs from various manufacturers (Table1).

Discussion
The arti cial airway is instrumental for proper mechanical ventilation and is essential for airway patency of patients during operation.During the while in intensive care unit or the perioperative period, it is necessary to manage the airways and airbags to ensure the safety .The common causes of airbag leaks includes airbag and tube rupture. The common causes of airbag tube rupture in perioperative anaesthesia or during ICU care are bites, tears, or accidental severing of the tube while providing medical care when the patient is unconscious during resuscitation. [5][6][7][8][9][10][11][12] If the treatment is not timely, oral secretions and gastric contents can enter the airway leading to aspiration pneumonia, which in severe cases can result in death. [13]It is reported that a broken in ation line can be clamped with a syringe air supply vessel clamp to provide adequate airbag pressure, [5] however, this prevents the airbag pressure for being measured. For instance, excessive in ation of the endotracheal tube may cause the airbag pressure to increase to a great extent leading to increased risk of serious injury, including tracheal mucosal ischaemia, ulcer, necrosis, tracheoesophageal stula and even tracheal rupture. Excessive injection of the laryngeal mask will also make the cuff pressure too high, resulting in pharyngeal mucosal compression and even ischaemic necrosis. Postoperative complications such as severe pharyngeal pain, eating di culty and hoarseness may occur [14][15][16].
Several previous studies have described six catheter balloon repair methods. Whiteside et al. [5]a syringe and directly clamping the blood vessel clamp after gas injection in the in ation line to restore the pressure of the airbag. Barrios et al.
[6] also proposed that a closing cap be used after clamping the blood vessel clamp to maintain pressure of the airbag. However, these methods do not allow one to monitor the cuff pressure and it can lead to tracheal mucosal damage or even severe complications. Yoon K et al. [17] used a metal puncture needle, intercepted the middle needle stem and inserted both ends of the needle stem into the two sides of the in ation line to maintain the pressure in the airbag. There are several disadvantages to this method. First, improper cutting of the needle can cause complete blockage of the needle tip or narrow lumen, which can prevent air from entering the airbag. Secondly, if the cutting end is sharp, it is easy to puncture the connecting pipe when joining the connecting lines. When attaching the needle stem to the stump, the operation is complex because the material is small. This leads to more potential safety hazards for patients. Additionally, the device cannot be used during magnetic resonance examinations. Emergency repair of endotracheal tube balloons takes a long time and increases the workload of medical care workers. Dayan et al.
[18] used a puncture needle to repair the line by connecting both ends to maintain the pressure in the airbag, which has numerous limitations. Due to the lack of tube core support, it is di cult to connect the two ends during operation. Further, the material is small and improper usage can be dangerous to patients. Owusu et al. [19] directly connected the residual end of the airbag in ation line of the endotracheal tube with an epidural puncture needle, and then connected it to a three-way valve to ll the airbag. Although effective, the materials needed for this repair are not readily available in an ICU setting. During pressure measurements, it is also necessary to operate the three-way valve to measure the airbag pressure. Lastly, Singh et al. [20] described a method of reconstructing an in ation line. In this method, the LMA device was repaired using a connecter, but the process of material acquisition and production takes some time.
Existing methods are limited as they involve complex operations and materials and increase medical workload. In contrast, our method is convenient as only one intravenous indwelling needle is needed. Further, the operation is simple and shortens the recovery time for patients. In addition, the liquid injection end of the intravenous indwelling needle provides a valve plug, which is safe and sealed (Fig. 5). There is no need to connect the three-way valve, and it will not cause air leakage of the airbag. It can be used to measure the airbag pressure accurately, even when in an intense magnetic eld [18]. Current literature suggests that the breakage of the endotracheal tube and laryngeal mask in ation line is common. Therefore, our repair method is an easy way to repair a broken in ation tube or valve to avoid compromising the airway and prevent secondary intubation and shorten the rescue time of patients in distress due to ETT or LMA failure.
This method still has several shortcomings to consider. When repairing the connecting line of an endotracheal tube, the position can be too deep and di cult to operate. Secondly, the types of adult and child endotracheal tubes and laryngeal masks in our department are limited. Products from other manufacturers may function differently after utilising this repair method. Second, our cuff pressure test was completed through an in vitro model. Although our experimental conditions are similar to what is used clinically, the pressure measurement may differ from the pressure in the human body. According to the statistical analyses, there is no difference in the pressure between intact and repaired tubes. Finally, as we hypothesised, the strength of the restored ETT or LMA in ation lines was much lower than the control, intact ETT or LMA lines.

Conclusion
This straightforward method is the most effective process to date and shortens the rescue time of patients to ensure their safety. The method is safe and reliable and can be effectively used to temporarily repair damaged in ation tubes, in ation bags, or in ation valves. This method prevents reintubation and secondary intubation and reduces the workload of medical staff. Futhermore, this convenient and rapid method will reduce physical and mental harm of patients and the occurrence of legal disputes.

Availability of data and materials
The datasets analysed during the current study are available from the corresponding author upon reasonable request.
Competing interests: The authors declare that they have no competing interests.

Funding
This research did not receive any speci c grant from funding agencies in the public, commercial, or notfor-pro t sectors.
Authors' contributions: TW and SC designed this study and wrote the manuscript. TW and JW performed the experiments. TW SC and JW assisted with data analysis. SC and YL revised the nal manuscript. All the authors contributed to the nal version of the manuscript.

Figure 2
Tensile strength test of ETT/LMA in ation pipe.
The cotton thread on the ETT/LMA in ation line is xed with an electronic scale and the distal pressure is maintained.

Figure 3
A Cuff pressures of ETTs group over 15 hours. Cuffs from ve intact (blue blocks) and ve repaired (brown blocks) were in ated to 30 cmH 2 0, and tensions were remeasured 15 hours later. There was no signi cant difference in the pressure drop from baseline between the two groups (9.60 ± 1.14 to 9.4 ± 1.52 cmH 2 O, t = 2.36, p = 0.82). B Force required to break intact versus repaired in ation lines. Segments from entire (blue blocks) and revised (brown blocks) in ation lines were attached to an electronic scale and pulled down until the tubes were disrupted. Repaired in ation lines were weaker than entire in ation lines (7.88 ± 1.73N to 36.62 ± 5.62 N, t = 10.93, P < 0.05). Segments from entire (blue blocks) and revised (brown blocks) in ation lines were attached to an electronic scale and pulled down until the tubes were disrupted. Repaired in ation lines were weaker than entire in ation lines (26.85 ± 2.15 N to 36.85 ± 3.29 N, t = 5.68, P < 0.05).

Figure 5
Sealing the injection end of the needle with a valve plug.