Endotracheal tube cuff-small important part of a big issue

Journal of Clinical Monitoring and Computing 2018-2019 end of year summary: respiration

This paper reviews 28 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2018 and 2019, within the field of respiration. Papers were published covering endotracheal tube cuff pressure monitoring, ventilation and respiratory rate monitoring, lung mechanics monitoring, gas exchange monitoring, CO₂ monitoring, lung imaging, and technologies and strategies for ventilation management.

Arthur Guedel and the Ascendance of Anesthesia: A Teacher, Tinkerer, and Transformer

At the beginning of the twentieth century, anesthesia was an emerging field without permanent departments, exclusive practitioners, or academic residency programs. Instead, surgeons and nurses administered anesthetic gases in an ad-hoc fashion, exposing patients to the perilous risks of general anesthesia. Dr. Arthur Guedel was a general practitioner from rural Indiana who unexpectedly became an integral part of anesthesia's evolution into a safety conscience and formally recognized expertise. Beginning during his military service in World War I, he refined the stages of ether anesthesia and produced the definitive textbook on inhalational anesthetics. During the prolific career that followed, Guedel also introduced ground-breaking devices for patient-controlled analgesia, cuffed endotracheal intubation, and oral airway patency. His inclusive mentorship, collaborative research, and innovative instruments exemplify his role as a multitalented tinkerer, teacher, and transformative leader. This essay examines Guedel's pioneering contributions and the scope of his influence, all of which revolutionized anesthesia and expanded surgeons' operative capability. Through the lens of Guedel's personal and professional life, this essay further illustrates how the diverse, interdisciplinary, and cutting edge characteristics of the practice itself contributed to anesthesia's increased importance in modern medicine.

Bi-national survey of intraoperative cuff pressure monitoring of endotracheal tubes and supraglottic airway devices in operating theatres

Correct intracuff pressure of endotracheal tubes and supraglottic airway devices is required to avoid complications such as sore throat, dysphagia and dysphonia, while maintaining an adequate airway seal. However, intracuff pressure monitoring of airway devices during general anaesthesia may not receive the attention it deserves. The aim of this survey was to investigate the current practice regarding intraoperative cuff pressure monitoring in hospitals across Australia and New Zealand. An online ten-question survey was disseminated by the Australian and New Zealand College of Anaesthetists Clinical Trials Network to a randomised selection of 1000 Australian and New Zealand College of Anaesthetists Fellows working in private and public hospitals of varying sizes. There were 305 respondents in total, but not all respondents answered all questions. In total, 67 of 304 respondents (22.0%) did not have access to a cuff pressure manometer at their main site of work, and of these, 30 (9.9%) expressed that they would like access to one in their daily practice. Of 288 respondents, 122 (40.0%) reported that they used cuff pressure monitoring as part of their routine practice, but 95 (33.0%) measured the cuff pressure at induction only. For supraglottic airway devices, only 44 of 250 respondents (17.6%) aimed for a cuff pressure of 40–60 cmH2O. Of 255 respondents, 101 (39.6%) aimed for a cuff pressure of 20–30 cmH2O for endotracheal tubes. These findings indicate that educational programmes are required to increase the availability and use of cuff pressure monitoring devices for both endotracheal tubes and supraglottic airway devices across Australia and New Zealand.

Reliability of cuff pressure gauges

Cuff pressure gauges are the only recommended instrument to perform controls on endotracheal tube cuff pressure during anesthesia. No calibration is mandatory for these devices. The aim of this study was to describe the level of conformity of various cuff pressure gauges. The single-center measurements were performed with a cuff pressure calibrator on all cuff pressure gauges that were usually used in the operating room. Seven measurements (repeat three times) on each cuff pressure gauges at different levels of pressures (i.e. 0, 10, 20, 27, 30, 40 and 50 cmH₂O) were performed. Our homologation criteria were either the reliability of the leak test (value of cuff pressure gauges maintained at 120 cmH₂O during 5 s) or the difference between the values of the cuff pressure tested and the calibrator below 1.3 cmH₂O at the range of 20-30 cmH₂O. A total of 567 measurements on 27 cuff pressure gauges were performed. Only 30% (n = 8/27) of the cuff pressure gauges reach our homologation criteria. 30% (n = 8/27) failed at the leak test. 48% (n = 13/27) of the cuff pressure gauges tested, had a calibration variation error > 1.3 cmH₂O on the levels of pressure between 20 and 30 cmH₂O. A minority of cuff pressure gauges went through our homologation criteria. These results demonstrate us that there is a real problem of the reliability and the follow-up of those medical devices. This study suggests to reinforce biomedical engineering control on these devices.

Assessing the correct inflation of the endotracheal tube cuff: a larger pilot balloon increases the sensitivity of the 'finger-pressure' technique, but it remains poorly reliable in clinical practice

The pilot balloon palpation (or 'finger-pressure') method is still widely used to assess the endotracheal tube cuff inflation, despite consistent evidence of its poor sensitivity in recognizing cuff overinflation. It was recently speculated that this may be related to the lower wall tension (due to the smaller radius) of the pilot balloon as compared with the cuff, according to Laplace's law. To verify this hypothesis and, secondarily, to assess whether the use of a 'large' pilot balloon (identical to the cuff) increases the reliability of this technique, 62 anesthetists (41 experienced anesthesiologists and 21 residents) were asked to estimate the pressure of a cuff inflated to 88 mmHg into a simulated trachea by feeling both a usual and a modified 'large' pilot balloon. A similar test was repeated at 40 mmHg. After palpation of the usual pilot balloon, only 35% of participants (49% of experienced anesthesiologists and 10% of residents) recognized considerable overinflation (88 mmHg), as compared with 87% of participants (95% of experienced anesthesiologists and 71% of residents) after palpation of the 'large' pilot balloon. Moreover, 89% of participants (85% of experienced anesthesiologists and 95% of residents) believed that pressure was higher in the 'large' balloon than in the normal one. However, only 32% of participants (51% of experienced anesthesiologists and none of residents) recognized slight overinflation (40 mmHg) after feeling the 'large' balloon. The pilot balloon size affects the sensitivity of the 'finger-pressure' technique, but it remains poorly reliable with a larger pilot balloon.

Optimization of Endotracheal Tube Cuff Pressure by Monitoring CO2 Levels in the Subglottic Space in Mechanically Ventilated Patients: A Randomized Controlled Trial

BACKGROUND

Many of the complications of mechanical ventilation are related to inappropriate endotracheal tube (ETT) cuff pressure. The aim of the current study was to evaluate the effectiveness of automatic cuff pressure closed-loop control in patients under prolonged intubation, where presence of carbon dioxide (CO2) in the subglottic space is used as an indicator for leaks. The primary outcome of the study is leakage around the cuff quantified using the area under the curve (AUC) of CO2 leakage over time.

METHODS

This was a multicenter, prospective, randomized controlled, noninferiority trial including intensive care unit patients. All patients were intubated with the AnapnoGuard ETT, which has an extra lumen used to monitor CO2 levels in the subglottic space.The study group was connected to the AnapnoGuard system operating with cuff control adjusted automatically based on subglottic CO2 (automatic group). The control group was connected to the AnapnoGuard system, while cuff pressure was managed manually using a manometer 3 times/d (manual group). The system recorded around cuff CO2 leakage in both groups.

RESULTS

Seventy-two patients were recruited and 64 included in the final analysis. The mean hourly around cuff CO2 leak (mm Hg AUC/h) was 0.22 ± 0.32 in the manual group and 0.09 ± 0.04 in the automatic group (P = .01) where the lower bound of the 1-sided 95% confidence interval was 0.05, demonstrating noninferiority (>-0.033). Additionally, the 2-sided 95% confidence interval was 0.010 to 0.196, showing superiority (>0.0) as well. Significant CO2 leakage (CO2 >2 mm Hg) was 0.027 ± 0.057 (mm Hg AUC/h) in the automatic group versus 0.296 ± 0.784 (mm Hg AUC/h) in the manual group (P = .025). In addition, cuff pressures were in the predefined safety range 97.6% of the time in the automatic group compared to 48.2% in the automatic group (P < .001).

CONCLUSIONS

This study shows that the automatic cuff pressure group is not only noninferior but also superior compared to the manual cuff pressure group. Thus, the use of automatic cuff pressure control based on subglottic measurements of CO2 levels is an effective method for ETT cuff pressure optimization. The method is safe and can be easily utilized with any intubated patient.

A technique to measure the intracuff pressure continuously: an in vivo demonstration of its accuracy

OBJECTIVE

A major concern with the use of cuffed endotracheal tubes (cETT) in children is hyperinflation of the cuff which may compromise tracheal mucosal perfusion. To measure the intracuff pressure (CP), we devised a method using the transducer of an invasive pressure monitoring device. The objective of the study was to test the accuracy and validity of this device for instantaneous and continuous CP monitoring.

METHODS

The study was conducted in 2 phases. In Phase 1 (200 pediatric patients), after inflation of the cuff, the CP was measured using the standard manometer and the transducer simultaneously. In Phase 2 (20 pediatric patients), the transducer was left connected to the pilot balloon of the ETT to obtain a continuous CP reading and the standard manometer was used to measure the CP at 5-min intervals. Statistical analysis included a Bland-Altman comparison and linear regression analysis.

RESULTS

In Phase 1, linear regression analysis demonstrated an R2 value of 0.9956. The bias was 0.30 cmH2O, the precision was 0.75 cmH2O, and the 95% level of agreement (LOA) ranged from -1.16 to 1.77 cmH2O. In Phase 2, the linear regression analysis revealed an R2 value of 0.9846. The bias was 0.28 cmH2O, the precision was 0.7 cmH2O, and the 95% LOA ranged from -1.1 to 1.66 cmH2O.

CONCLUSION

Our study demonstrates that when cETTs are used in the pediatric population, the transducer of the invasive pressure monitoring device can be used reliably to measure the CP at the time of inflation and continuously thereafter.

Detection of endobronchial intubation by monitoring the CO2 level above the endotracheal cuff

Early detection of accidental endobronchial intubation (EBI) is still an unsolved problem in anesthesia and critical care daily practice. The aim of this study was to evaluate the ability of monitoring above cuff CO2 to detect EBI (the working hypothesis was that the origin of CO2 is from the unventilated, but still perfused, lung). Six goats were intubated under general anesthesia and the ETT positioning was verified by a flexible bronchoscope. The AnapnoGuard system, already successfully used to detect air leak around the ETT cuff, was used for continuous monitoring of above-the-cuff CO2 level. When the ETT distal tip was located in the trachea, with an average cuff pressure of 15 mmHg, absence of CO2 above the cuff was observed. The ETT was then deliberately advanced into one of the main bronchi under flexible bronchoscopic vision. In all six cases the immediate presence of CO2 above the cuff was identified. Further automatic inflation of the cuff, up to a level of 27 mmHg, did not affect the above-the-cuff measured CO2 level. Withdrawal of the ETT and repositioning of its distal tip in mid-trachea caused the disappearance of CO2 above the cuff in a maximum of 3 min, confirming the absence of air leak and the correct positioning of the ETT. Our results suggest that measurement of the above-the-cuff CO2 level could offer a reliable, on-line solution for early identification of accidental EBI. Further studies are planned to validate the efficacy of the method in a clinical setup.

Endotracheal tube cuff leaks: causes, consequences, and management

The consequences of endotracheal tube (ETT) cuff leak may range from a bubbling noise to a life-threatening ventilatory failure. Although the definitive solution is ETT replacement, this is often neither needed nor safe to perform. Frequently, the leak is not caused by a structural defect in the ETT. Cuff underinflation, cephalad migration of the ETT (partial tracheal extubation), misplaced orogastric or nasogastric tubes, wide discrepancy between ETT and tracheal diameters, or increased peak airway pressure can cause leaks around intact cuffs. Correction of these problems will stop the leak without ETT replacement. Alternatively, ETT cuff, pilot balloon, and inflation system damage due to inadvertent trauma or manufacturing defects may be responsible. Conservative management ideas (management without ETT replacement) were previously published to solve the problem. However, when a large structural defect is identified or conservative measures fail, ETT replacement becomes necessary. This can be performed with direct laryngoscopy if laryngeal visualization is adequate. A difficult exchange with possible airway loss should be anticipated, and prepared for, when there are signs and/or history of difficult intubation. A risk/benefit analysis of each individual situation is warranted before decisions are made on how best to proceed. Alternative back-up ventilation plans should be preformulated and the necessary equipment ready before the exchange. In this review, various management concerns and plans are discussed, and a simple algorithm to manage leaky ETT cuff situations is presented.