An intact pilot balloon assembly is crucial to the proper function of a cuffed tracheal tube. Disruption of the pilot balloon, transection of the attached inflation line, or incompetence of the 1-way pilot balloon valve causes deflation of the tracheal tube cuff. This may result in inadequate ventilation and aspiration of oropharyngeal or gastric secretions.1 Thus, when cuff pressure cannot be maintained in a patient requiring mechanical ventilation, replacement of the tracheal tube is typically performed. However, such replacement may present unacceptable risk to patients who were difficult to intubate or in whom difficulty is anticipated because of airway edema.2
We recently encountered such a patient requiring postoperative ventilation in whom intubation had been difficult in the operating room and where airway edema had occurred because of prolonged, prone positioning and substantial crystalloid administration. Upon arrival to the intensive care unit (ICU), we noted a significant air leak around the cuff. Investigation revealed that the inflation line had been transected during transport. The clinical assessment was that exchanging the tracheal tube at this point in time would likely have been challenging, exposing the patient to the risk of our losing the airway. We consequently repaired the tubing by placing an internal stent, composed of a portion of an intravenous (IV) catheter; this allowed the cuff to be inflated sufficiently to seal the airway. Thus, we were able to avoid the need to replace the tracheal tube at this juncture.
Subsequently, we performed a study to assess the integrity of the proposed repair method. Our hypothesis 1 was that the repaired pilot tube assembly would maintain cuff pressure not statistically different from the native device. If true, the method we describe would represent an acceptable temporary alternative to replacement of a tracheal tube under circumstances where the cuff itself is intact, but there is disruption to the function of the pilot balloon assembly. Our hypothesis 2 was that the repaired inflation line segment would be weaker than the intact tubing, thus requiring increased care during handling.
Cuffed Mallinckrodt Lo-Pro tracheal tubes (Medtronic, Minneapolis, MN) were used for the experiments. We used sets of 10 tracheal tubes, with equal numbers of size 7 and 8 mm (internal diameter). Repairs to the transected inflation lines were performed as described in Figure 1.
Experiments were performed in vitro using a simulated trachea, composed of a 20-mL plastic syringe with the plunger removed (BD Luer-Lock Tip; Becton Dickinson, Franklin Lakes, NJ). The internal diameter of the syringe measures 2 cm, approximating the size of an adult human trachea.3 Cuff inflation was performed using a combined inflation/manometer device (Cufflator; Posey, Arcadia, CA), with pressures recorded to the nearest 1 cm H2O. This device is commonly used to monitor tracheal tube cuff pressure in ICUs.4
Compensation for Loss of Pressure due to Measurement
During preliminary testing, we noted a loss of pressure resulting from bleeding of a small amount of air during attachment of the manometer directly to the pilot balloon valve. To compensate for this, we first inflated 10 tracheal tube cuffs to 20 to 30 cm H2O using the manometer bulb, then removed the device. We then immediately reconnected the manometer and remeasured the pressure. The average pressure drop was 8.4 cm H2O (standard error = 0.4 cm H2O). This value was added to final pressure measured at the end of the cuff pressure interval (see next section).
Tracheal Tube Cuff Pressure Testing
The first experiment evaluated the maintenance of cuff pressure over time. Each of the 10 intact and repaired tracheal tubes was inserted into a simulated trachea and inflated to a pressure of 20 to 30 cm H2O. Cuff pressure was measured at baseline and after 8 hours. Tests were conducted simultaneously in an office with the temperature maintained at approximately 74°F on a flat surface and out of direct sunlight. Eight hours later, the pressure of each tracheal tube was rechecked with the manometer, corrected by the pressure drop due to reattachment of the manometer (see section above). We compared the pressure drops between the repaired and intact tracheal tube groups.
Inflation Line Integrity Testing
Underwater leak tests were performed in an empty operating room to evaluate the integrity of the repaired inflation line. A basin was filled with water, and the mended segment from each of 10 repaired tracheal tubes was submerged. The cuff was inflated with air via a syringe to a pressure of 120 mm Hg (measured by connecting the pilot balloon valve to an arterial pressure transducer via a 3-way stopcock, with the pressure displayed on a physiologic monitor). We deliberately used a pressure much higher than clinically relevant cuff pressures (eg, 20–30 cm H2O, 14.7–22.1 mm Hg) to stress the repaired segment. We visually examined the repaired inflation line segment for air bubbles, which would indicate a leak. The transducer was zeroed before each measurement. We compared the percentages of the presence of a leak between the repaired and the intact tracheal tube groups.
Inflation Tubing Tensile Strength Testing
Tensile strengths of inflation lines from 7 intact and 7 repaired tracheal tubes were determined by measuring the static force required to snap the line or separate the repaired segments, respectively. (We had misplaced 3 of the original 10 repaired tubes before this testing, hence the smaller sample sizes.) Each inflation line was secured to a hook using a nonslip mono knot. The other end of the inflation lines was tied with a nonslip mono knot to a digital hanging hook scale. IV fluid bags (nominally containing 250 mL saline) were gradually hung on the end of the hook until the inflation line broke or separated. The weight of the attached bags just before disruption of the lining was then measured and converted to force. We compared the force required to disrupt the tubing between the intact and the repaired tracheal tube groups.
Generalizability of Findings
To evaluate for generalizability of the repair method, standard Mallinckrodt tracheal tubes (3.0–8.5 mm) were tested for absence of a leak under water seal at high pressure with our repair method. We similarly tested samples from other manufacturers, including Parker Medical (Highlands Ranch, CO), Smiths Medical (Keene, NH), and Sun Med (Largo, FL).
A sample size of 5 for each group was calculated for 80% power to detect a difference of 5 cm H2O between pressure drops over 8 hours between the 2 groups, assuming a pooled standard deviation of 2.5 (coefficient of variation of 50%). We selected 5 cm H2O as a clinically relevant value because from an initial cuff inflation pressure of 25 cm H2O, underinflation (<20 cm H2O) occurred in approximately half of ICU patients undergoing mechanical ventilation, as assessed during 8 hours of continuous monitoring.5 To be conservative, we elected to study 10 tracheal tubes in each group.
Data are presented as the mean ± standard error. Differences between intact and repaired tracheal tubes were assessed using the unpaired, 2-sided Student t test (Systat v12; Systat Software, San Jose, CA), with P < .05 required to claim statistical significance. P values were not adjusted, as only 2 a priori hypotheses were tested and an argument for using a 1-sided test could be advanced (ie, there was no plausible reason to think that repaired tracheal tubes would function better than intact devices).
Eight-hour interval measurements in 10 intact versus 10 repaired tracheal tubes demonstrated no significant difference in the pressure drop from baseline (mean difference = 0.5 cm H2O; 95% confidence interval [CI], −2.2 to 1.2 cm H2O; P = .54; Figure 2). There was no visible air leak from the 10 repaired inflation line segments, submerged underwater, when the cuff was inflated to 120 mm Hg, a pressure much higher than would ever be used to inflate a tracheal tube cuff. Our hypothesis 1 was confirmed.
Repaired inflation lines had a much lower tensile strength than intact tubing (mean difference = −21.9 N; 95% CI, −25.7 to −18.1 N; P < 10−6; Figure 3). For reference, 30 N was the typical force applied during a cadaver study investigating the effectiveness of cricoid pressure.6 Our hypothesis 2 was confirmed.
Disrupted inflation lines from tracheal tubes ranging in size from 3.0 to 8.0 mm and from various manufacturers were successfully repaired, as assessed by absence of a leak under high pressure. In some cases, a 24-gauge rather than a 22-gauge IV catheter was required as the stent (Table).
Simulation testing demonstrated that our repair method was effective in maintaining a clinically relevant cuff pressure over an 8-hour interval and was able to withstand extremely high inflation pressures without disruption. Not unexpectedly, the strength of the repaired inflation line was considerably less than that from an intact tracheal tube, requiring care to avoid excessive traction, which might result in disruption. Thus, we recommend that a prominent marker (eg, a piece of colored tape with a label indicating that the tubing has been repaired) be placed on the inflation line to alert the nursing and medical staff of the need for increased care when handling the pilot balloon assembly or moving the patient. In addition, the respiratory therapy department should be notified that the inflation line has been repaired so that its therapists can take appropriate precautions when they measure the cuff pressure or otherwise handle the tracheal tube.
The method we describe for repairing a transected inflation line could also be used if the pilot balloon were to break or if the inflation valve were to malfunction. In such circumstances, one could simply cut the inflation line below the pilot balloon and stent the pilot balloon with tubing taken from an intact tracheal tube. Whether a repaired tracheal tube should be replaced, once conditions for reintubation become acceptable, or maintained in use is a decision that will depend on the clinical scenario. We emphasize that our repair method will not work if there is disruption to the tracheal tube cuff or if transection of the inflation line occurs too distally to allow insertion of the stent. In addition, if the inflation line were stretched (thereby narrowing the lumen) and a segment of intact tubing were not available for the repair, our method might not be possible.
There have been several previous studies describing pilot balloon repair in both adult and pediatric populations. Each study describes a unique method of tracheal tube repair, although the authors did not provide data demonstrating structural integrity of their repair methods. Kovatsis et al7 described 3 methods of pilot balloon repair employed in the context of pediatric tracheal tube placement through supraglottic airways. One method for repair involved an epidural clamp connector. Other methods were described involving IV catheters connected to a Luer Lock valve port adapter. Singh et al8 described similar methods, including use of a Luer Lock as well as a triple stopcock valve to replace the pilot balloon. These techniques, however, eliminated the pilot balloon. Thus, cuff inflation could not be visually assessed by examination of the pilot balloon. Yoon et al9 employed a method similar to ours, although they used a “20 g needle connector,” which served as a conduit to a replacement pilot balloon. Details of the technique, including the source of the connector or if a blunt or sharp needle was used, were not provided.
Recently, a commercial product, BE 409 Pilot Tube Repair Kit (Instrumentation Industries Inc, Bethel Park, PA), has been introduced, which is similar in make-up to the repair method described by Yoon et al.9 The kit includes a replacement pilot balloon connected to a blunt, tapered needle, which is introduced into the severed end of a damaged inflation line to serve as a stent to the replacement pilot balloon. Similar to the published studies,6–8 we were unable to locate data demonstrating the integrity of this repair method. Furthermore, the manufacturer’s product specification sheet indicates that use is contraindicated during magnetic resonance imaging, and the device is not widely available. In contrast, our method uses readily obtainable IV catheters and does not introduce any potential issues related to exposure to high-strength magnetic fields.
Our study has several limitations. First, the internal diameter of pilot assembly inflation lines is not standardized, so the catheter sizes we determined for successful stenting might vary if a tracheal tube other than what we studied is used. Second, our testing of cuff pressure maintenance was done using a simulated trachea model composed of rigid plastic, so the actual pressures we measured might differ from those that would occur in vivo. However, the conditions were the same for the intact and repaired tracheal tubes, and we analyzed the differences in the drop in pressure between the groups. Thus, our conclusions related to equivalence would not be affected. Finally, the method of measuring the cuff pressure using the commercial device we employed itself resulted in a variable loss in pressure. The manner in which we compensated for this measurement artifact introduced a random error in the absolute pressure values measured. However, because the pilot balloon valves were identical and functional in both intact and repaired tracheal tubes, this effect would not have differed systematically between the groups.
In summary, we describe an effective method for repairing pilot balloon assemblies, using a portion of an IV catheter to stent the inflation line. Our procedure can be used effectively as a temporizing measure in situations where there is disruption to the inflation line, the pilot balloon, or the inflation valve, and where replacement of the tracheal tube might present an excessive patient risk. Additional care is necessary when handling a repaired pilot balloon assembly, because the tensile strength of the inflation line is reduced.
Name: Amir C. Dayan, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Name: Richard H. Epstein, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
This manuscript was handled by: Avery Tung, MD, FCCM.
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Copyright © 2016 International Anesthesia Research Society
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