Cuff pressure and microvascular occlusion in the tracheal mucosa. An intravital microscopic study in the rabbit

Transesophageal probe placement increases endotracheal tube cuff pressure but is not associated with postoperative extubation failure after congenital cardiac surgery

Context:

The concomitant use of cuffed endotracheal tubes (ETT) and transesophageal echocardiography (TEE) probes increases ETT cuff pressures (CP), which may contribute to mucosal ischemia and perioperative complications such as failed extubation.

Aims:

To assess changes in ETT CP after TEE insertion in patients of different age groups undergoing congenital heart surgery and examine the relationship between ETT CP and postoperative extubation failure.

Settings and Design:

Single-center quality improvement project.

Subjects and Methods:

ETT CP was measured with a manometer following intubation and again after TEE insertion. Tracheal perfusion pressure was then calculated and postoperative extubation failures were recorded.

Statistical Analysis:

Chi-square testing, Fisher’s-exact testing, one-way analysis of variance testing or Kruskal–Wallis testing with Dunn's pairwise, and student's t-test or Wilcoxon rank-sum testing were used to analyze the data.

Results:

Median ETT CP increased significantly after TEE insertion in each age group, with infants showing a smaller magnitude of increase (+2 [1-6] cm H₂O, P < 0.001) than adults (+12 [8-14] cm H₂O, P = 0.008) (intergroup comparison P = 0.002). Five patients (9%) failed extubation, all of which were infants. Within the infant subgroup, no significant difference existed between failed vs successful extubation regarding ETT CP during bypass (15 ± 1 vs 16 ± 2 mmHg, P = 0.206) or tracheal perfusion pressure pre-bypass (34 ± 9 vs 38 ± 11 mmHg, P = 0.518), during bypass (20 ± 9 vs 22 ± 6 mmHg, P = 0.697), or post-bypass (42 ± 9 vs 41 ± 9 mmHg, P = 0.923). There was a significant difference in cardiopulmonary bypass duration (151 ± 29 vs 85 ± 32 min, P < 0.001).

Conclusion:

Factors beyond intraoperative ETT CP likely play a larger role in postoperative extubation failure.

Guidelines for Tracheostomy From the Korean Bronchoesophagological Society

The Korean Bronchoesophagological Society appointed a task force to develop a clinical practice guideline for tracheostomy. The task force conducted a systematic search of the Embase, Medline, Cochrane Library, and KoreaMed databases to identify relevant articles, using search terms selected according to key questions. Evidence-based recommendations for practice were ranked according to the American College of Physicians grading system. An external expert review and a Delphi questionnaire were conducted to reach a consensus regarding the recommendations. Accordingly, the committee developed 18 evidence-based recommendations, which are grouped into seven categories. These recommendations are intended to assist clinicians in performing tracheostomy and in the management of tracheostomized patients.

Successful emergency management of a bleeding tracheoinnominate fistula

In this case, we describe a novel approach to achieving temporary haemostasis in acute massive haemorrhage from a bleeding tracheoinnominate fistula. We report the case of a 42-year-old man admitted to hospital after suffering 80% body surface area burns. Thirty days following the percutaneous insertion of a tracheostomy, spontaneous massive haemorrhage occurred via the tracheostomy stoma, the tracheostomy tube and the mouth. After hyperinflation of the tracheostomy cuff which controlled airway contamination, effective tamponade was achieved using a hyperinflated balloon on a Foley catheter that was introduced by direct laryngoscopy into the upper larynx above the tracheotomy stoma. This provided temporary control of the bleeding until definitive management through ligation of the innominate artery via median sternotomy.

An in-vitro study to evaluate high-volume low-pressure endotracheal tube cuff deflation dynamics

BACKGROUND

High-volume low-pressure (HVLP) endotracheal tube (ETT) cuffs for critically ill patients often deflate during the course of mechanical ventilation. We performed an in-vitro study to comprehensively assess HVLP cuff deflation dynamics and potential preventive measures.

METHODS

We evaluated 24-hour deflation of seven HVLP cuffs of cylindrical or tapered shape, and made of polyvinylchloride or polyurethane. Experiments were performed within a thermostated chamber set at 37 °C. In the first stage of experiments, the cuff pilot balloon valve was not manipulated. The cuff internal pressure was assessed hourly for 24 hours, via a linear position sensor which monitored cuff deflation displacements. Then, we re-evaluated cuff deflation of the worst-performing ETT cuffs with the cuff pilot balloon valve sealed. Finally, we inflated ETT cuffs within an artificial trachea to evaluate deflation dynamics during mechanical ventilation.

RESULTS

Initial tests showed an exponential decrease in cuff internal pressure in five out of seven cuffs. Cuffs of cylindrical shape and made of polyurethane demonstrated the fastest deflation rates (P<0.050 vs. cuffs of conical shape and made of polyvinylchloride). When the cuff pilot balloon valve was not sealed, the internal cuff pressure deflation rate differed significantly among ETTs (P=0.005). Yet, upon sealing the cuff pilot balloon valve and during mechanical ventilation, cuff deflation rates decreased (P<0.050).

CONCLUSIONS

In controlled in-vitro settings, ETT cuffs consistently deflate over time, and the cuff pilot balloon valve plays a central role in this occurrence. Deflation rate decreases when cuffs are inflated within a plastic artificial tracheal model and mechanical ventilation is activated.

Laryngotracheal stenosis in burn patients requiring mechanical ventilation

Objective

To identify the incidence of laryngotracheal stenosis (LTS) in burn patients requiring mechanical ventilation at a regional academic burn center.

Methods

A retrospective review of all burn patients requiring endotracheal intubation or tracheostomy for airway management between 2003 and 2009 was performed. A group of trauma patients requiring similar airway instrumentation during the same period of time was used as a control.

Results

None of the trauma patients and 2 of the burn patients developed LTS. Both presented with stridor and were diagnosed within 2–5 weeks after extubation. One patient underwent successful carbon dioxide laser radial incision and dilation and continues to do well. The other patient failed endoscopic treatment and required T-tube placement. The incidence of LTS in burn patients requiring mechanical ventilation was 2.98% overall and 4.76% among those with inhalational injury.

Conclusions

Patients become symptomatic within weeks of the initial injury. Treatment is challenging and multiple surgical procedures are often required. A larger study is necessary to determine if the incidence is higher among burn patients.

Endotracheal tubes for critically ill patients: an in vivo analysis of associated tracheal injury, mucociliary clearance, and sealing efficacy

BACKGROUND

Improvements in the design of the endotracheal tube (ETT) have been achieved in recent years. We evaluated tracheal injury associated with ETTs with novel high-volume low-pressure (HVLP) cuffs and subglottic secretions aspiration (SSA) and the effects on mucociliary clearance (MCC).

METHODS

Twenty-nine pigs were intubated with ETTs comprising cylindrical or tapered cuffs and made of polyvinylchloride (PVC) or polyurethane. In specific ETTs, SSA was performed every 2 h. Following 76 h of mechanical ventilation, pigs were weaned and extubated. Images of the tracheal wall were recorded before intubation, at extubation, and 24 and 96 h thereafter through a fluorescence bronchoscope. We calculated the red-to-green intensity ratio (R/G), an index of tracheal injury, and the green-plus-blue (G+B) intensity, an index of normalcy, of the most injured tracheal regions. MCC was assessed through fluoroscopic tracking of radiopaque markers. After 96 h from extubation, pigs were killed, and a pathologist scored injury.

RESULTS

Cylindrical cuffs presented a smaller increase in R/G vs tapered cuffs (P = .011). Additionally, cuffs made of polyurethane produced a minor increase in R/G (P = .012) and less G+B intensity decline (P = .022) vs PVC cuffs. Particularly, a cuff made of polyurethane and with a smaller outer diameter outperformed all cuffs. SSA-related histologic injury ranged from cilia loss to subepithelial inflammation. MCC was 0.9 ± 1.8 and 0.4 ± 0.9 mm/min for polyurethane and PVC cuffs, respectively (P < .001).

CONCLUSIONS

HVLP cuffs and SSA produce tracheal injury, and the recovery is incomplete up to 96 h following extubation. Small, cylindrical-shaped cuffs made of polyurethane cause less injury. MCC decline is reduced with polyurethane cuffs.

Prospective observational study on tracheal tube cuff pressures in emergency patients--is neglecting the problem the problem?

Background

Inappropriately cuffed tracheal tubes can lead to inadequate ventilation or silent aspiration, or to serious tracheal damage. Cuff pressures are of particular importance during aeromedical transport as they increase due to decreased atmospheric pressure at flight level. We hypothesised, that cuff pressures are frequently too high in emergency and critically ill patients but are dependent on providers’ professional background.

Methods

Tracheal cuff pressures in patients intubated before arrival of a helicopter-based rescue team were prospectively recorded during a 12-month period. Information about the method used for initial cuff pressure assessment, profession of provider and time since intubation was collected by interview during patient handover. Indications for helicopter missions were either Intensive Care Unit (ICU) transports or emergency transfers. ICU transports were between ICUs of two hospitals. Emergency transfers were either evacuation from the scene or transfer from an emergency department to a higher facility.

Results

This study included 101 patients scheduled for aeromedical transport. Median cuff pressure measured at handover was 45 (25.0/80.0) cmH₂O; range, 8-120 cmH₂O. There was no difference between patient characteristics and tracheal tube-size or whether anaesthesia personnel or non-anaesthesia personnel inflated the cuff (30 (24.8/70.0) cmH₂O vs. 50 (28.0/90.0) cmH₂O); p = 0.113.

With regard to mission type (63 patients underwent an emergency transfer, 38 patients an ICU transport), median cuff pressure was different: 58 (30.0/100.0) cmH₂O in emergency transfers vs. 30 (20.0/45.8) cmH₂O in inter-ICU transports; p < 0.001. For cuff pressure assessment by the intubating team, a manometer had been applied in 2 of 59 emergency transfers and in 20 of 34 inter-ICU transports (method was unknown for 4 cases each). If a manometer was used, median cuff pressure was 27 (20.0/30.0) cmH₂O, if not 70 (47.3/102.8) cmH₂O; p < 0.001.

Conclusions

Cuff pressures in the pre-hospital setting and in intensive care units are often too high. Interestingly, there is no significant difference between non-anaesthesia and anaesthesia personnel. Acceptable cuff pressures are best achieved when a cuff pressure manometer has been used. This method seems to be the only feasible one and is recommended for general use.

Endotracheal Tube Cuff Pressure Is Unpredictable in Children

The use of cuffed tracheal tubes in children younger than 8 yr of age has recently increased, although cuff hyperinflation may cause tracheal mucosal damage. In this study, we sought to measure the cuff pressure (P(cuff)) after initial free air inflation (iP(cuff)) and to follow its evolution throughout the duration of 50% nitrous oxide (N(2)O) anesthesia. One-hundred-seventy-four children, aged 0 to 9 yr, fulfilling the following criteria, were studied: 1). weight of 3-35 kg; 2). ASA physical status I or II; 3). elective surgery; 4). anesthesia with tracheal intubation using a cuffed tube and lasting at least 45 min; and 5). gas mixture containing 50% N(2)O. Free air inflation results in variable iP(cuff), with hyperinflation in 39% of cases. Numerous gas removals were required to maintain P(cuff) less than 25 cm H(2)O in 85% of the patients. The number of deflations decreased with the duration of mechanical ventilation and was small after 105 min. No difference was observed among the different cuffed tube sizes. We conclude that iP(cuff) is unpredictable after free air inflation and that numerous gas removals are required to maintain P(cuff) less than 25 cm H(2)O during N(2)O anesthesia in children.

IMPLICATIONS

Free inflation of the tracheal tube cuff, controlled only by the palpation of the pilot balloon, is not reliable and results in extremely variable (and sometimes very high) initial cuff pressures in children. In addition, nitrous oxide anesthesia may result in cuff hyperinflation requiring numerous gas removals.

Effects of experimental graded compression on blood flow in spinal nerve roots. A vital microscopic study on the porcine cauda equina

Compression injuries of spinal nerve roots are very common. However, the basic pathophysiology of these conditions is not fully understood. In this study a model is presented for experimental graded compression of the nerve roots of the pig cauda equina, including a technique for vital microscopic studies on the microcirculation flow of the intrinsic vessels of the nerve roots during compression. With this model critical pressure levels for compression-induced occlusion of the arterioles, capillaries, and venules of the intrinsic vasculature of the nerve roots were determined. The study showed that the average minimum pressure in the inflated balloon required to stop the flow in the arterioles was 127 mm Hg (SD = 18, n = 11), in the capillaries 40 mm Hg (SD = 6, n = 12), and in the venules 30 mm Hg (SD = 10, n = 12). The average mean arterial pressure (MAP) was 150 mm Hg (SD = 14, n = 12). There was a statistically significant correlation (p greater than 0.001) between the MAP and the pressure required to stop the flow in the arterioles (r = 0.83, n = 14), but no correlation between MAP and capillary (r = 0.09 NS, n = 20) or venular (r = -0.28 NS, n = 34) occlusion pressure. After the nerve roots had been compressed at 50 or 200 mm Hg for 10 min or 2 h, the recirculation started immediately. There was a hyperemia during the first 10 min, with a dilatation of the vessels, particularly the venules. In nerve roots exposed to compression for 2 h at either 50 or 200 mm Hg, an intraneural edema developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of graded compression on intraneural blood blow. An in vivo study on rabbit tibial nerve

Compression applied to a peripheral nerve may easily interfere with intraneural blood flow. In the present experimental study, a vital microscopic technique was used to observe changes in intraneural microcirculation (intrafascicularly and extrafascicularly) when graded compression was applied to a rabbit's tibial nerve by a specially designed minicompression device. Interference with venular flow was observed already at a pressure of 20 to 30 mm Hg while arteriolar and intrafascicular capillary flow was impaired at about 40 to 50 mm Hg. At 60 to 80 mm Hg no blood flow could be observed in the nerve. Nerves observed 3 or 7 days after 2 hours of compression at 400 mm Hg showed no or very slow stagnant blood flow within the previously compressed segment. It is concluded that acute compression of nerve may cause persistent impairment of intraneural microcirculation due to mechanical injury to blood vessels.