High-volume Low-pressure Cuffs Research Articles

Comparison of Normal Saline and Alkalinized 2% Lignocaine to Reduce Emergence Phenomenon and Post-Intubation Morbidities: A Prospective, Double-Blind, Randomized Study.

Endotracheal intubation for airway management in general anesthesia is associated with post-intubation morbidities due to tracheal mucosa injury caused by endotracheal tube (ETT) cuff. Nitrous oxide (N2O) diffuses into tracheal tube cuffs filled with air. The rate of diffusion of N2O through the membrane is proportional to its concentration gradient. High-volume low-pressure cuffs expand with only a slight increase in pressure until fully inflated. At this point, owing to the inelasticity of the material, the cuff pressure rises rapidly. This increased pressure can damage the tracheal mucosa. This phenomenon can be avoided, if we inflate the cuff with either a liquid or a gas mixture identical to the inspired gas and monitor the cuff pressure and volume at regular intervals. When lignocaine is used to inflate the ETT cuff, it diffuses to the underlying tracheal mucosa. Thus reducing local irritation and inflammation of the airway through its local anesthetic action. Alkalinization of lignocaine increases its rate of diffusion across the ETT cuff. It also reduces the dose of local anesthetic required to achieve the desired result. We sought to determine the benefits of filling the ETT cuff with alkalinized lignocaine 2% over normal saline, to prevent ETT-induced emergence phenomenon and reduce the incidence of post-intubation morbidities like sore throat, hoarseness, and nausea. This prospective, randomized, double-blind, and comparative study was done at a multispecialty hospital. A total of 120 individuals ofAmerican Society of Anesthesiologists (ASA) physical status 1 and 2, posted for surgery under general anesthesia, were randomly selected and divided into two groups: alkalinized 2% lignocaine group (group L) and normal saline group (group S). After induction of general anesthesia, the airway was secured with appropriate-sized ETT. The ETT cuff was inflated with either of the study media. Continuous cuff pressure monitoring was done to keep cuff pressure below 30 centimeters of water (cm of H2O), at all times. At extubation, the response was evaluated in terms of percentage change in heart rate (HR) and blood pressure from baseline, coughing, bucking, and restlessness. All the surgeries lasted more than two hours. Post-operatively, the patients were evaluated for sore throat and hoarseness, at regular intervals of up to 24 hours. ETT cuff pressure was initially less in group S, which rose to a significantly higher level at extubation, compared to group L (p <0.001). At extubation, there was a significant increase in HR and systolic blood pressure (SBP) from baseline, in group S than in group L (p <0.001 and p=0.001, respectively).The incidence of cough and restlessness was less in group L, compared to group S (p<0.001 and p=0.002, respectively). Mean extubation time and emergence time was more in group S than in group L (p<0.001). Post-operatively, the incidence and severity of sore throat were significantly higher in group S than in group L (p<0.001). Meanwhile, the incidence of hoarseness and nausea was comparable in the two groups. Continuous ETT cuff pressure monitoring helps to keep cuff pressure below tracheal mucosa capillary occlusion pressure. Filling the ETT cuff with alkalinized lignocaine further reduces extubation response and post-intubation morbidities.

Impact of Low-Volume, Low-Pressure Tracheostomy Cuffs on Acute Mucosal Injury in Swine.

Tapered low-volume, low-pressure (LVLP) cuffs have been introduced to improve sealing and reduce injury from tracheostomy and endotracheal intubation compared to traditional cylindrical high-volume, low-pressure (HVLP) cuffs. The objective of this study is to develop a swine model of tracheostomy injury and to compare live tissue response following LVLP and HVLP tracheostomy placement. In vivo animal study. Academic institution. Swine underwent tracheostomy followed by placement of LVLP and HVLP tracheostomy cuffs at 30 cm H2O. After 24 and 48 hours, tracheal specimens underwent histopathological analysis including cilia, lamina propria and epithelial thickness, and mucosal injury score. In all cuff contact areas, mean epithelial thickness for both tracheostomy cohorts was decreased compared to control epithelium at 24 and 48 hours (P < .01). HVLP proximal epithelium thickness was decreased at 24 and 48 hours relative to LVLP sections (P < .05). Lamina propria thickness in proximal LVLP sections was less than HVLP sections at 24 hours and 48 hours (P < .05). Mucosal injury score at areas of cuff contact was increased in tracheostomy cohorts relative to controls (P < .001), with HVLP injury score greater than LVLP at the proximal cuff (P < .05). In a swine model, tracheostomy resulted in increased mucosal injury compared to normal tracheal mucosa. LVLP cuffs resulted in less injury than HVLP cuffs, with reduced mucosal inflammation and improved health of epithelium and lamina propria. The wider proximal LVLP cuff demonstrated improved mucosal health compared to the HVLP cylindrical cuff.

A Tapered Cuff Tracheal Tube Decreases the Need for Cuff Pressure Adjustment After Surgical Retraction During Anterior Cervical Spine Surgery: A Randomized Controlled, Double-Blind Trial.

BackgroundSurgical retraction to expose the vertebrae during anterior cervical spine surgery increases tracheal tube cuff pressure and may worsen postoperative sore throat and dysphonia. This randomized double-blind study investigated the effect of cuff shape on intraoperative cuff pressure and postoperative sore throat and dysphonia.MethodsEighty patients were randomized to tracheal intubation with a tapered cuff or a conventional cylindrical high-volume low-pressure cuff (control) during anesthesia. Intraoperative cuff pressures were compared. The primary outcome was the incidence of pressure adjustment needed when the cuff pressure increased to > 25 mm Hg after surgical retraction. The secondary outcome was the incidence of postoperative sore throat and dysphonia.ResultsThe incidence of pressure adjustment after surgical retraction was significantly lower in the tapered group than in the control group (13% vs. 48%; P = 0.001; relative risk reduction, 74%). The median [interquartile range (IQR)] cuff pressure (mm Hg) was significantly lower for the tapered cuff than for the control cuff before surgical retraction [9 (7–12) vs. 12 (10–15); P < 0.001] and after retraction [18 (15–23) vs. 25 (18–31); P = 0.007]. The median (IQR) postoperative dysphonia score assessed by a single speech-language pathologist was lower in the tapered group than in the control group [4 (3–6) vs. 5.5 (5–7); P = 0.008].ConclusionA tapered cuff tracheal tube decreased the need for the adjustment of cuff pressure after surgical retraction during anterior cervical spine surgery, thereby avoiding intraoperative pressure increase. It also has a better outcome in terms of dysphonia.Clinical Trial Registration[www.clinicaltrials.gov], identifier [NCT04591769].

Intraoperative airway cuff pressure monitoring: are we doing it right?

Background: Insertion of endotracheal tubes (ETT) and supra-glottic airway devices (SGA) are common practice amongst anaesthesiologists when administering general anaesthesia to facilitate numerous surgical procedures. In an era where quality of patient care and patient safety takes precedence, monitoring of intraoperative cuff pressure of an airway device remains an essential component in anaesthetic practice. Methods: Data was collected through a single page questionnaire from postgraduate trainees in anaesthesiology involved in administering general anaesthesia for elective surgical procedures over a three- month period at the National Hospital of Sri Lanka. Study population included all patients undergoing elective surgical procedures requiring an endotracheal tube (ETT- high volume low pressure cuff) or a supra-glottic airway (SGA) device to facilitate ventilation under general anaesthesia. Data was analysed using SPSS version 22.0 and was expressed as median, inter-quartile range [IQR], frequency, percentage and 95% confidence interval (CI) where appropriate. Correlation test was used to determine the relationship between cuff pressure and size of airway device. A non-parametric test was used to measure the significance between various carrier gas combinations and cuff pressure values for both ETT and SGA devices. Results: 196 completed questionnaires were received over a three-month period. Mean age of the patients were 44.1 years and 64.8% were females. Majority (53.6%) were ASA (American Society of Anaesthesiologists) grade I. ETT were used in 82.7% and SGA devices were used in 13.8% of cases. ETT’s were used for laparotomies/laparoscopic procedures in 32.7% followed by 22.2% in gynaecological surgeries and 17.9% in thyroid and related surgery. SGA devices were mostly used for gynaecological procedures (40.7%). Theatre supporting staff was responsible for the initial cuff inflation in 83.2%. During the initial cuff pressure measurement 58.6% of endotracheal tubes had pressures within the recommended level (20-30cmH 2 O). 33.3% had cuff pressures of >30cmH 2 O while 8% had cuff pressures of 2 O. In contrast to the above findings, the recommended cuff pressure values for SGA devices was achieved only in 29.6% and in 37% the cuff pressures were more than 70cmH 2 O which was alarming. 33.3% had cuff pressure values less than recommended. Conclusion and Recommendations: It is evident that cuff pressure values in both endotracheal tubes and supra-glottic devices were not optimal and it was more so with the latter. Adherence to current evidence-based recommendations to ensure patient safety is vital in anaesthetic practice. To overcome the above problem, cuff pressure must be monitored at the commencement of surgery and at hourly intervals during general anaesthesia, which will identify under or over-inflation of the cuff and minimize related complications. Similarly, a sign-post to remind the anaesthetist, “Have you checked the cuff pressure today?” should be displayed in all operating theatres next to the airway trolley to avoid failure to reach standards.

Application of low damage endotracheal intubation in patients undergoing extra long-term endotracheal intubation: a case report

To approach the effect of low damage endotracheal intubation on reducing the occurrence of cuff-related intubation complication and prolonging the intubation time. On January 7th, 2015, 1 patient with respiratory failure after subarachnoid hemorrhage were admitted to Huludao Central Hospital. Immediate endotracheal intubation and ventilator assisted ventilation were performed. When the trachea was difficult to be removed in a short time, and tracheotomy was refused, a low damage endotracheal intubation was used for a long term. On the basis of the original high volume low pressure cuff, this tube was designed for inner cuff, the hole was allowed in the inner cuff to connect with the tube. During the period of ventilation, the cuff pressure changed with airway pressure automatically, therefore it would reduce the compression injury of tracheal mucosa, improve the tolerance of the patients, and prolong the intubation time. The patient was removed from the tube on October 12th, 2015 with an intubation day of 279, the intubation-related complications and severe aspiration pneumonia had not been observed during the application of low damage endotracheal intubation. Design of this intubation ensured the cuff pressure changes with airway pressure, therefore, it could effectively avoid the cuff pressure become too high, and reduce the occurrence of intubation-related complication. This low damage endotracheal had an evident superiority in the aspects of cuff management. It has a better practical significance, especially for patients with long intubation time.

Comparison of the Effect on the Cuff Pressure of the Endotracheal Tubes Following Cuff Inflation with Air and With Nitrous Oxide – Oxygen during General Anaesthesia - A Prospective, Randomised Study

Background and aims: During general anaesthesia cuffed endotracheal tubes are used to provide airway seal and prevent aspiration. But it has been observed that use of nitrous oxide oxygen for ventilation during anaesthesia leads to rise in intracuff pressure which can be transmitted to the wall of trachea leading to complications. In this study we compared the effect on cuff pressure of Portex endotracheal tubes( high volume low pressure cuffs) and Armoured endotracheal tubes( low volume high pressure cuffs) when the cuffs were inflated with air and with nitrous oxide- oxygen mixture during general anaesthesia using nitrous oxide oxygen. Method:After institutional ethics committee approval 180 patients aged 18 -60 years of ASA status I & IIposted for elective surgeries were randomly allocated in four groups of 45 each. After taking consent and intravenous access general anaesthesia was given with endotracheal intubation. Group A1- Portexendotracheal tube cuff inflated with air. Group A2- Portex endotracheal tube cuff inflated with nitrous oxide- oxygen mixture. Group B1- Armoured endotracheal tube cuff inflated with air.Group B2- Armoured endotracheal tube cuff inflated with nitrous oxide- oxygen mixture. Controlled ventilation was done with nitrous oxide oxygen during the anaesthesia. Endotracheal tube cuff pressure was measured at inflation and at every 30 minutes interval till 90 minutes. Postoperatively patients were observed for any complications such as sore throat, difficulty in swallowing, hoarseness of voice, etc. Results: It was observed that the intracuff pressure in both the high volume low pressure and the low volume high pressure cuffed endotracheal tubes rises with time when the cuffs are inflated with air. The rise was not significant when nitrous oxide - oxygen was used for inflating the cuff in both the groups. Regardless of the type of inflating medium used for cuff inflation the incidence of complications was high in low volume high pressure cuffed endotracheal tubes as compared to high volume low pressure cuffed endotracheal tubes.

Does Endotracheal Tube Design Affect Cuff Seal, Safety and Subglottic Suction Performance: An in-vitro study?

Introduction: Ideally endotracheal tubes (ETT) should protect the airways without causing pressure induced tissue damage. Traditionally, the addition of a tracheal cuff was heralded as seal against aspiration. This type of ETT utilized a low volume high pressure cuff which caused tracheal damage such as stenosis and malacia. The next development in ETT design was the high volume low pressure cuffs intended to protect the airways while reducing tissue damage. Although reducing damage, the new cuff did not reliably protect the airways. Microaspiration still remains a serious complication of intubation. A taper shaped cuff design was recently introduced to prevent microaspiration without causing tracheal damage. Concerns were raised regarding the contact area and the resultant pressure against the tracheal wall of the taper shaped cuff. Another innovation introduced to prevent microaspiration is subglottic suction present in the tube design. Therefore, the aim of this paper is to evaluate cuff seal performance, cuff safety and intrinsic suction efficiency of current commercially available ETT. Methods: Three separate studies evaluated these areas of interest. Cuff seal performance was evaluated using an approved in vitro test fixture mimicking the human trachea. We investigated the cuff seal performance of 7 endotracheal tubes with different cuff designs and identical tracheal tube size using water as the medium. Three different size tubes from 3 different manufacturers were tested to determine subglottic suction efficiency and cuff sealing performance using the same in vitro test fixture. In a similar fixture a pressure sensitive array was mounted to compare the surface pressure of a standard barrel shaped cuff to the taper shaped cuff. The array design allowed for the pressure profile of the cuff to be mapped where it contacted the cylinder wall. In all tests the cuff pressures were maintained at 25 cm H_2O according to manufacturer's recommendations. Results: The sealing performance varied between the tube manufacturers with TaperGuard (TG) showing the lowest leak at .6 g/5minutes and Kimberly Clark Micro cuff (KCmc) with the highest 59.2 g/5 minutes. In terms of suction efficiency Teleflex ISIS (ISIS) had the best suction performance (.2-5.3ml/sec) at all viscosities and Portex (SACETT) (.3-2.9 ml/min) was the lowest. When comparing surface force the taper shaped cuff was less compared to the barrel shaped cuff. Conclusions: Performance in all areas tested ETTs varied considerably in terms of sealing and suction efficiency. However, the taper shaped cuff demonstrated the least surface pressure and best sealing.

Endotracheal Tubes for Critically Ill Patients: An In Vivo Analysis of Associated Tracheal Injury, Mucociliary Clearance, and Sealing Effi cacy

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). 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. 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). 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.

Endotracheal tube cuff leak: Minor product defect or lack of cuff pressure monitoring?

Sir, We report a leak in the pilot inflation line of an endotracheal tube (ETT) resulting in partial loss of tidal volume and increased risk of pulmonary aspiration. It also brings out the significance of intra-operative cuff pressure monitoring. A 60-year-old man, body mass index 30 kg/m2, a case of acute subdural hematoma and subarachnoid hemorrhage with increased intracranial pressure and deteriorating sensorium (Glasgow Coma Scale 6) was admitted to the intensive care unit. The history of preoperative fasting and other co-morbidities was unreliable. After a quick routine pre check for cuff patency of the ETT by inflation and cuff inspection followed by rapid deflation, the patient was intubated with a size 8.0 mm ID ETT (Ruschelit® Safety Clear Plus, Teleflex Medical Sdn Bhd, Kamunting, Malaysia) and the cuff was inflated with air and manually palpated to assess adequacy of its pressure. He was mechanically ventilated and other measures to control intracranial pressure were initiated. The patient was shifted to the operation theatre for an emergency craniotomy. Nitrous oxide and oxygen 60:40 sub-minimum alveolar concentration isoflurane and propofol infusion 50–100 μg/kg/min were used for maintenance. During the period of approximately 45 min from the time of intubation to the beginning of surgery, a loss of tidal volume was noticed. A check laryngoscopy ruled out tube migration. The cuff appeared lax and was re-inflated but the events repeated in the same manner again. The ETT was changed with another one and examined for obvious leaks. This ETT was then immersed in a bowl of water and the cuff inflated with an aneroid manometer (Mallinckrodt Medical Athlone, Ireland). Multiple air bubbles were noticed to appear at higher cuff pressures (>100 cm H2O), but as the pressure was reduced gradually, their size, number and speed lowered, and the bubbling stopped at the cuff pressure below 40 cm H2O. The leak was detected from the point where the transparent pilot inflation line entered the blue stem of the pilot cuff [shown by the arrow in [Figure 1]. The product defect was communicated to the manufacturers. Figure 1 Arrow showing air bubbles in water at higher cuff pressure; inset showing pilot inflation line entering the pilot cuff with the arrow showing the probable leak site A leak from any part of the ETT assembly can be alarming, more so in cases of difficult airway or in surgeries involving limited access to airway (non-supine position and head and neck surgery) where a change of tube may not be possible intra-operatively.[1] It may cause increased risk of pulmonary aspiration and inadequate ventilation (inadequate depth of anesthesia, intra-operative awareness, and hemodynamic instability). The leaks in the cuffs and the various ways to tackle them are well known but a defect in the pilot inflation line has been sparsely reported in the literature.[2] Various methods using continuous inflation with air, saline or lignocaine jelly or use of three-way stopcock to maintain cuff pressure are documented, though most of them are no more than a rescue measure.[1] This report alarms the caregiver to be vigilant at all times as even minor leaks from unusual sites may have clinically significant and long-standing consequences. Besides, it also reinforces the need for objective monitoring of the ETT cuff pressure, especially in the presence of nitrous oxide (which readily diffuses into the cuff and increases its pressure). Manual assessment of cuff pressure may be grossly incorrect and may underestimate pressures.[3] The pressure can be high as to manifest minor leaks (even when high volume low-pressure cuffs are used), as seen in the case reported. The effects of the leak due to the minor product defect could have been avoided if the cuff pressure was measured and maintained within the safe range of 20–30 cm of H2O.[4]

Tracheal Resection and Anastomosis for Postintubation Tracheal Stenosis

Introduction: Tracheal stenosis is one of the dreaded complication of tracheal intubation. Tracheal resection and anastomosis is an established definitive treatment for stenosis more than one cm. Here, we present a case of postintubation tracheal stenosis managed by resection and anastomosis, first of its kind in our centre.&#x0D; Case Report: We present a case of 26-year female who underwent tracheal intubation during her treatment of tubercular meningitis. Two weeks later, she returned with respiratory difficulty. A diagnosis of post-intubation tracheal stenosis was made. Tracheal resection and anastomosis was done. Recovery was uneventful and she was discharged on 14th post-operative day.&#x0D; Conclusion: Post-intubation tracheal stenosis is still a dreaded complication even after the introduction of high volume low pressure cuff. They can be successfully managed. Care personnel in intensive care unit (ICU) should perform to prevent this complication.

How to avoid microaspiration? A key element for the prevention of ventilator-associated pneumonia in intubated ICU patients.

Microaspiration of subglottic secretions through channels formed by folds in high volume-low pressure poly-vinyl chloride cuffs of endotracheal tubes is considered a significant pathogenic mechanism of ventilator-associated pneumonia (VAP). Therefore a series of prevention measures target the avoidance of microaspiration. However, although some of these can minimize microaspiration, benefits in terms of VAP prevention are not always obvious. Polyurethane-cuffed endotracheal tubes successfully reduce microaspiration but high quality data demonstrating VAP rate reduction are lacking. An analogous conclusion can be made regarding taper-shaped cuffs compared with classic barrel-shaped cuffs. More clinical data regarding these endotracheal tube designs are needed to demonstrate clinical value in addition to in vitro-based evidence. The clinical usefulness of endotracheal tubes developed for subglottic secretions drainage is established in multiple studies and confirmed by meta-analysis. Any change in cuff design will fail to prevent microaspiration if the cuff is insufficiently inflated. At least one well-designed trial demonstrated that continuous cuff pressure monitoring and control decrease the risk of VAP. Gel lubrication of the cuff prior to intubation temporarily hampers microaspiration through sludging the channels formed by folds in high volume-low pressure cuffs. As the beneficial effect of gel lubrication is temporarily, its potential to reduce VAP risk is probably nonsignificant. A minimum positive end-expiratory pressure of at least 5 cmH2O can be recommended as it reduces the risk of microaspiration in vitro and in vivo. One randomized controlled study demonstrated a reduced risk of VAP in patients ventilated with PEEP (5–8 cmH2O). Regarding head-of-bed elevation, it can be recommended to avoid supine positioning. Whether a 45° head-of-bed elevation is to be preferred above 25-30° head-of-bed elevation remains unproven. Finally, the routine monitoring of gastric residual volumes in mechanically ventilated patients receiving enteral nutrition cannot be recommended.

Will the Taper Shaped Cuff Replace the Conventional High Volume-Low Pressured Cuff on Endotracheal Tube?

An effective tracheal seal plays an essential role in precluding aspiration and boosting efficiency with mechanical ventilation when endotracheal tube is inflated. High cuff pressure can cause damage to the tracheal wall and lead to serious complications such as tracheal stenosis. Endotracheal tube (ET) cuff pressures greater than 30 cmH2O may impede capillary blood flow in the tracheal wall, and ET cuff pressures greater than 50 cmH2O is considered high enough to completely block capillary blood flow.[1] Low volume high pressure cuff was used in early ETs but replaced by high volume low pressure (HVLP) cuff because the former causes mucosal injury along the lateral tracheal wall. HVLP cuffs appeared ideal because they are capable of producing a seal with low pressure. However, HVLP's large cuff diameter has emerged as a key issue as it is 1.5 to 2 times larger than the adult trachea. Longitudinal or oblique folds are developed upon inflation within the larger sized HVLP cuffs. The seal then becomes incomplete and allows secretions and air to leak as a result. Pulmonary aspiration of microorganism mass found in the oral cavity is considered one of leading causes of ventilator-associated pneumonia. In addition, over inflation of HVLP cuff can markedly increase cuff pressure, particularly around the folds and result in injury to the tracheal mucosa.[2] Low volume cuff tubes has recently drawn attention again while many researchers explored benefits of modified low volume low pressure (LVLP) cuff tubes. A taper-shaped cuff is designed to fit into the trachea at its narrow end and provides smaller cuff volume. This tapered cuff design is more effective in minimizing longitudinal folds when inflated, improving tracheal seal and preventing leakage of secretions and air even under high airway pressures, compared with conventional HVLP cuffs.[2,3] The transition from HVLP cuffs to taper-shaped cuffs is currently underway in endotracheal tubes. That is, the trend is moving back to low volume cuff tracheal tubes, which exert low pressure, in favor of better outcomes. Then we can have a question: Are tapered cuffs safe from pressure injury that is the most critical complication of low volume high pressure cuffs? While transmission of intracuff pressure to the tracheal wall depends on the cuff material, taper-shaped cuffs can transmit all the intracuff pressure to the tracheal wall.[4] In endoracheal position, the intracuff pressure of LVLP cuffs can be significantly increased by a slight change in inflating volume. In addition, the tapered cuff design provides smaller area of contact with the tracheal wall, compared to cylindrical shaped HVLP cuffs,[2] meaning that the extent of transmitted pressure is higher on the tracheal wall. It is therefore important to examine pressure changes with volume in tracheal tube cuff inflated. Special attention to pressure changes is also crucial in the tracheal tube cuff exposed to nitrous oxide for anesthesia because cuff pressure can significantly increase with increasing volume.[5] In case the taper-shaped cuff is not inflated adequately and develops an asymmetrical shape,

The Effect of Positive End-Expiratory Pressure on Air Leakage: Comparison of Cuff Designs

Background: Recently developed taper-shaped cuffs (TG cuffs) of endotracheal tubes (ETTs) are known to have a more potent sealing effect than cylindrical high-volume low-pressure cuffs (HL cuffs) of conventional ETTs. The aim of this study was to compare TG cuffs with HL cuffs of ETTs in a bench-top model with regard to air leakage under various positive end-expiratory pressures (PEEP). Methods: HL cuffs and TG cuffs made from PVC were included (HL group vs. TG group). A model trachea with an internal diameter (ID) of 22 mm was attached to a test lung. The test lung was ventilated using an anesthesia respirator with volume controlled mode and PEEPs of 0, 5, 10, or 15 cm H2O. Using spirometry, percentages of expired to inspired tidal volumes (TVe/i) were calculated as a measure of air leakage. Results: With regard to PEEPs, the HL group showed significantly higher air leakage compared to the TG group (p < 0.0001), and a higher PEEP resulted in greater air leakage (p < 0.0001). Air leakage with higher PEEP was greater in the HL group than in the TG group at ID 7.0 mm and 7.5 mm (p = 0.0467, p = 0.0045) Conclusions: This study shows the superior sealing ability of the TG cuff during ventilation at various PEEPs.

Migration of polyurethane high-volume low-pressure cuffed endotracheal tubes after neck flexion and extension

To the Editor: In 2007 our hospital converted from standard polyvinyl high-pressure low-volume (HPLV) cuffed endotracheal tubes (ETT) to high-volume low-pressure (HVLP) polyurethane cuffed ETTs. HVLP ETTs feature cuffs that are longer, made of thinner material (10 lm), and inflate to a lower pressure, compared to traditional polyvinyl cuffed ETTs (Fig. 1) [1]. We have noticed the material of the HVLP polyurethane cuffs allows tube stem migration of 0.5 cm in either direction (up and down) while the cuff stays in place. The migration of ETTs towards the carina with neck flexion and away from the carina with neck extension has been documented only with HPLV ETTs [2–5]. The thinner material of HVLP cuffs may allow significant tracheal migration; we therefore conducted a prospective, IRB approved study to observe the mobility of these ETTs from their fixed position following flexion and extension of the neck. One hundred patients (50 males, 50 females) undergoing elective surgery, requiring routine intubation and general anesthesia, signed a written informed consent to participate in the study. All patients’ tracheas were initially intubated to a depth of 21 or 23 cm for women and men, respectively. A single anesthesiologist utilized a fiberoptic bronchoscope (Olympus LF-GP, Center Valley, PA, USA) and a standard metric ruler in centimeters to determine the actual tip to carina distances following intubation. The ETTs were then secured and held in place at the incisors by a second anesthesiologist. Following both flexion and extension of the neck, any ETT tip migration observed (fiber-optic evaluation) was recorded in centimeters by research personnel. Data are expressed as mean ± SD and (range) where appropriate. The Wilcoxon signed ranks test was used to calculate the displacements of the ETT. A P value of B0.05 was considered statistically significant. Flexion resulted in movement of the ETT tip inward (towards the carina) in 78 % of patients and extension moved the tip outward (away from the carina) in 81 % of patients. The average migratory distance (cm) of the ETT tip was 1.2 ± 1.0 (0–3.5) away from the carina following extension and 1.4 ± 1.4 (0–5) towards the carina after flexion (P \ 0.001 for flexion and extension). D. Mangar C. J. Sprenker R. A. Karlnoski R. K. Dodson E. M. Camporesi Florida Gulf-to-Bay Anesthesiology Associates, 1 Tampa General Circle Suite A327, Tampa, USA

An In Vitro Study to Assess Determinant Features Associated With Fluid Sealing in the Design of Endotracheal Tube Cuffs and Exerted Tracheal Pressures*

To assess the structural characteristics involved in the design of high-volume low-pressure endotracheal tube cuffs that are associated with fluid sealing effectiveness and to determine the extent of transmitted tracheal pressures upon cuff inflation. In vitro study. Pneumology laboratories. Eight high-volume low-pressure cuffs of cylindrical or tapered shape, made of polyvinylchloride or polyurethane, were studied. Cuffs were tested within a tracheal model, oriented 30° above horizontal to assess 1 hr leakage of oropharyngeal secretions simulant at cuff internal pressures of 15-30 cm H2O. The four best performing cuffs were evaluated for 24 hrs using an internal pressure of 30 cm H2O. The extent of transmitted tracheal wall pressure throughout the cuff-trachea contact area was determined using an internal pressure sensor within a tracheal model upon cuff inflation up to 30 cm H2O. Outer diameter, length, and compliance of each cuff were assessed. Multivariate regression analysis was performed to identify the main determinants of simulant leakage rate. The cuff-trachea contact area and the percentage of tracheal wall pressure measurements greater than 50 cm H2O were computed. Cuff design characteristics significantly differ among tubes. The cuffs made of polyurethane showed the best short- and long-term sealing efficacy. Nevertheless, in the multivariate analysis, the cuff outer diameter (n: 288, p = 0.003) and length (n: 288, p < 0.001), along with the internal pressure (n: 288, p < 0.001), were the only predictors of simulant leakage rate. The tapered cuffs showed the lowest tracheal wall contact area (n: 96, p < 0.001). The tracheal wall pressure distribution pattern was heterogeneous, and the percentage of high tracheal wall pressure significantly differs among the cuffs (n: 96, p < 0.001). The high-volume low-pressure cuffs' outer diameter, length, material, and internal pressure are the main determinants of sealing efficacy. Despite internal pressure within the safe range, transmitted tracheal pressure is extremely heterogeneous and differs among cuffs, occasionally reaching localized, very high, unsafe levels.

Unilateral vocal cord paralysis following a short period of endotracheal intubation anesthesia

Unilateral vocal cord paralysis following a short period of endotracheal intubation anesthesia

Preventing Ventilator-Associated Pneumonia - The Role of the Endotracheal Tube

The endotracheal tube, rather than the ventilator, is responsible for the vast majority of cases of ventilatorassociated pneumonia (VAP). Tracheal intubation should be avoided, or early extubation performed, if at all possible. With current high-volume low-pressure (HVLP) cuffs, pulmonary aspiration of microorganisms from the upper aerodigestive tract normally occurs and is frequently silent, until there is a clinical respiratory deterioration. Aspiration occurs by 3 mechanisms; channels within the HVLP cuff, in folding of the cuff upon movement and intermittent deflation of the cuff. This aspiration is the pivotal step in the development of VAP. The diagnosis of VAP is notoriously inaccurate and stifles the progress of research into prevention strategies. When treating bacteria present in the lung, the various paradigms of VAP diagnosis remain the only (and best) tools that we have to decide when the benefits of antibiotics outweigh the disadvantages. It is surprising, considering the accepted high mortality and cost of VAP, that until recently, there has been a massive under investment from industry in preventative technologies. New technologies should address the multiple factors implicated in the pathogenesis of VAP, including aspiration elimination by improved cuff designs. However, surrogate outcomes, such as pulmonary aspiration and tracheal colonisation (a more rigorous standard to aspire to), should be considered when evaluating preventative strategies. Pulmonary aspiration and/or tracheal colonisation by pathogenic organisms are undesirable and should be unacceptable. This review appraises the role of the endotracheal tube in both the development and prevention of VAP. Keywords: Agento, CASS, cuff, endotracheal, high volume low pressure, HILO EVAC, HVLP, Lotrach, low volume low pressure, LVLP, Microcuff, PneuX, sealguard, subglottic secretion drainage, taperguard, tube, ventilator-associated pneumonia

Mechanical influences on fluid leakage past the tracheal tube cuff in a benchtop model

High-volume low-pressure (HVLP) cuffs on endotracheal tubes do not fully protect the lower airway from leakage of potentially contaminated secretions down the longitudinal folds within the cuff. Here, our purpose was to evaluate potential effects of positive end-expiratory pressure (PEEP), inspiratory effort intensity, and tube characteristics on fluid leakage past the cuff. This benchtop study at a research laboratory used a tracheal tube inserted into an artificial Plexiglas trachea connected to a ventilator and lung model. Methylene blue was deposited above the tube cuff to simulate subglottic secretions. Five PEEP levels (0, 5, 10, 15, and 20 cmH₂O) were tested with volume-controlled ventilation and three simulated inspiratory effort levels with pressure-support ventilation. Several cuff materials and tube sizes were tested. The leakage occurrence rate ranged from 91% with zero PEEP to 8% with 15 and 20 cmH₂O PEEP and was indirectly proportional to the PEEP level with significant correlation (R² = 0.39, p < 0.001), an effect not explained by higher peak inspiratory pressure. Low, moderate, and high inspiratory effort intensities were associated with 38%, 46%, and 75% leakage rates, respectively (p = 0.024). Leakage flow was considerably less with polyurethane than with polyvinylchloride tubes (mean 0.5 versus 31.8 ml/h). Leakage increased with larger tube diameters. This benchtop study shows that PEEP and a polyurethane cuff prevent leakage past the endotracheal tube cuff, whereas greater inspiratory effort and larger tube diameters for given tracheal size induce or worsen leakage.

Tracheal fluid leakage in benchtop trials: comparison of static versus dynamic ventilation model with and without lubrication

Longitudinal folds in tracheal tube (TT) cuffs cause leakage of pooled secretions past the tube cuff, and the most common in vitro method to test the efficacy of a new tube is a benchtop model using an artificial rigid trachea. This study compared the potential of a static and dynamic ventilation benchtop model and cuff lubrication in testing the tracheal sealing properties of a given TT cuff. Static trial Six brands of 7.5 mm internal diameter (ID) cuffed TT (n = 8) with high volume-low pressure cuffs were inflated in an artificial trachea (18 mm ID) without and with lubrication. Dynamic trial The same tube cuffs, without lubrication, were subjected to positive pressure ventilation (PPV) + positive end-expiratory pressure (PEEP) of 5cmH(2)O or to PPV alone (without PEEP) or to PEEP alone (without PPV). Clear water (5 ml) was placed above the tube cuff, and fluid leakage (ml) was measured up to 60 min. Gel lubrication, PEEP alone and PPV + PEEP completely prevented fluid leakage across the tube cuffs in all six TT brands tested within 60 min when compared to the static unlubricated model (0% leak versus 100% leak; P < 0.01). Fluid leakage in the static unlubricated model and the PPV group was 1.38-4.76 ml and 0.23-4.47 ml, respectively. Gel lubrication, PEEP alone, and PPV + PEEP in the benchtop model had a much stronger protective effect than PPV alone on fluid leakage. Studies testing the fluid sealing efficiency of tube cuffs might be more conclusive in a static benchtop model without lubrication than in a dynamic model.

Randomised Comparison of the Classic Laryngeal Mask Airway™ with the Cobra Perilaryngeal Airway™ during Anaesthesia in Spontaneously Breathing Adult Patients

We tested the hypothesis that the Cobra Perilaryngeal Airway (PLA) with its high volume low-pressure cuff would provide superior airway leakage pressure compared with the Classic Laryngeal Mask Airway (LMA) in spontaneously breathing adult patients. Ninety consecutive adult patients were randomly allocated to receive one of these two supralaryngeal devices. The airway leakage pressure was higher for the PLA compared with the LMA (22 +/- 9 cmH2O vs. 18 +/- 6 cmH2O; P < 0.05). The mean airway device intracuff pressure was lower for the PLA compared to the LMA (36.1 +/- 15.2 mmHg vs. 86.3 +/- 25.3 mmHg P < 0.0001). The time required to achieve successful insertion was greater for the PLA compared with the LMA (39 +/- 21 seconds vs. 27 +/- 10 seconds; P < 0.005). The number of attempts required to achieve successful insertion and the incidence of postoperative complications were similar in both groups. The findings suggest that the PLA provides a superior airway seal at a lower intracuff pressure compared to the LMA. However the time for successful insertion may be increased.