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The investigation of initial endotracheal tube cuff pressures in the operating room: a multi-center cross-sectional study in China
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  • Published: 01 February 2026

The investigation of initial endotracheal tube cuff pressures in the operating room: a multi-center cross-sectional study in China

  • Heqi Peng1,
  • Zhaohui Tang1,2,
  • Yalin Li1,3,
  • Wei Zhang4,
  • Kaiming Duan5,
  • Hong Zheng6,
  • Lulong Bo7,
  • Yilin Zheng8,
  • Peng Wu9,
  • Jiaxin Tian10,
  • Yajuan Han11,
  • Xiaohua Zou12,
  • Gang Chen13,
  • Jun Xu14,
  • Jianqiang Guan15,
  • Xuezheng Zhang16,
  • Jianliang Sun17,
  • Yuekun Shen18,
  • Mao Zhou19,
  • Shu Zheng20,
  • Hui Wang21,
  • Hongmei Ma22,
  • Qulian Guo1,2,
  • Wangyuan Zou1,2 &
  • …
  • Yingqi Weng1,2 

Scientific Reports , Article number:  (2026) Cite this article

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Subjects

  • Epidemiology
  • Risk factors

Abstract

Cuffed endotracheal tubes (ETTs) are widely used in general anesthesia, with recommended cuff pressure (CP) between 20 and 30 cmH2O in adults. This multi-center study investigated actual CP management practices across 19 Grade A tertiary hospitals in China, involving 2058 anesthetized patients. The median initial CP measured within 30 min post-intubation was 48 cmH2O (IQR 32–70), with only 19% within the recommended range (75.4% > 30 cmH2O; 5.6% < 20 cmH2O). All institutions demonstrated similarly suboptimal CP management. Four distinct methods were used for cuff pressure estimation: pilot balloon palpation (96.2%), fixed-volume inflation (2.8%), minimal occlusive volume technique (0.7%), and direct manometry (0.2%). Among them, only direct manometry demonstrated reliable accuracy in achieving appropriate pressures. The remaining three methods showed no clear superiority over one another in terms of pressure assessment accuracy. In orotracheally intubated patients with palpation-estimated CP, independent risk factors for elevated pressure (> 30 cmH2O) included: age < 60 years, pressure-controlled ventilation, absence of PEEP, ETT internal diameter < 7.0 mm, aminosteroid neuromuscular blocker use, and trainee-performed inflation. These findings highlight widespread challenges in optimal CP management across Chinese tertiary care centers.

Data availability

The data that support the findings of this study are not openly available due to reasons of sensitivity and are available from the corresponding author upon reasonable request.

References

  1. Maertens, B. et al. Effectiveness of continuous cuff pressure control in preventing Ventilator-Associated pneumonia: A systematic review and Meta-Analysis of randomized controlled Trials*. Crit. Care Med. 50, 1430–1439. https://doi.org/10.1097/ccm.0000000000005630 (2022).

    Google Scholar 

  2. Touat, L. et al. Intubation-related tracheal ischemic lesions: incidence, risk factors, and outcome. Intensive Care Med. 39, 575–582. https://doi.org/10.1007/s00134-012-2750-6 (2013).

    Google Scholar 

  3. Seegobin, R. D. & van Hasselt, G. L. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs. Br. Med. J. (Clin. Res. Ed.). 288, 965–968. https://doi.org/10.1136/bmj.288.6422.965 (1984).

    Google Scholar 

  4. Cooper, J. D. Tracheal injuries complicating prolonged intubation and tracheostomy. Torac. Surg. Clin. 28, 139–. https://doi.org/10.1016/j.thorsurg.2018.01.001 (2018).

    Google Scholar 

  5. Liu, J. et al. Correlations between controlled endotracheal tube cuff pressure and postprocedural complications: A multicenter study. Anesth. Analg. 111, 1133–1137. https://doi.org/10.1213/ANE.0b013e3181f2ecc7 (2010).

    Google Scholar 

  6. Klompas, M. et al. Strategies to prevent ventilator-associated pneumonia in acute care hospitals: 2014 update. Infect. Control Hosp. Epidemiol. 35 (Suppl 2), 133–154. https://doi.org/10.1017/s0899823x00193894 (2014).

    Google Scholar 

  7. Hung, W. C., Ko, J. C., Weil, A. B. & Weng, H. Y. Evaluation of Endotracheal Tube Cuff Pressure and the Use of Three Cuff Inflation Syringe Devices in Dogs. Front. Veterinary Sci. https://doi.org/10.3389/fvets.2020.00039 (2020).

    Google Scholar 

  8. Ozcan, A. T. D., Doger, C., But, A., Kutlu, I. & Aksoy, S. M. Comparison of endotracheal tube cuff pressure values before and after training seminar. J. Clin. Monit. Comput. 32, 527–531. https://doi.org/10.1007/s10877-017-0046-7 (2018).

    Google Scholar 

  9. Stevens, G. J., Warfel, J. W., Aden, J. K. & Blackwell, S. D. Intraoperative endotracheal cuff pressure study: how education and availability of manometers help guide safer pressures. Mil. Med. 183, E416–E419. https://doi.org/10.1093/milmed/usx127 (2018).

    Google Scholar 

  10. Kim, D. et al. The changes of endotracheal tube cuff pressure by the position changes from supine to prone and the flexion and extension of head. Korean J. Anesthesiology. 68, 27–31. https://doi.org/10.4097/kjae.2015.68.1.27 (2015).

    Google Scholar 

  11. Rosero, E. B., Ozayar, E., Eslava-Schmalbach, J., Minhajuddin, A. & Joshi, G. P. Effects of increasing airway pressures on the pressure of the endotracheal tube cuff during pelvic laparoscopic surgery. Anesth. Analg. 127, 120–125. https://doi.org/10.1213/ane.0000000000002657 (2018).

    Google Scholar 

  12. Kim, T. K. et al. Increased tracheal cuff pressure during insertion of a transoesophageal echocardiography probe A prospective, observational study. Eur. J. Anaesthesiol. 32, 549–554. https://doi.org/10.1097/eja.0000000000000204 (2015).

    Google Scholar 

  13. Tu, H. N. et al. Nitrous oxide increases endotracheal cuff pressure and the incidence of tracheal lesions in anesthetized. Anesth. Analg. 89, 187–190. https://doi.org/10.1097/00000539-199907000-00033 (1999).

    Google Scholar 

  14. Sperry, R. J., Johnson, J. O. & Apfelbaum, R. I. Endotracheal tube cuff pressure increases significantly during anterior cervical fusion with the Caspar instrumentation system. Anesth. Analg. 76, 1318–1321. https://doi.org/10.1213/00000539-199376060-00023 (1993).

    Google Scholar 

  15. Chen, C. & Lu, F. C. Department of disease control ministry of Health, P. R. C. The guidelines for prevention and control of overweight and obesity in Chinese adults. Biomed. Environ. Sci.: BES. 17 Suppl, 1–36 (2004).

    Google Scholar 

  16. Haas, C. F., Eakin, R. M., Konkle, M. A. & Blank, R. Endotracheal tubes: old and new. Respir. Care. 59, 933–952. https://doi.org/10.4187/respcare.02868 (2014).

    Google Scholar 

  17. Guyton, D., Banner, M. J. & Kirby, R. R. High-volume, low-pressure cuffs. Are they always low pressure? Chest 100, 1076–1081, (1991). https://doi.org/10.1378/chest.100.4.1076

  18. Park, H. Y., Kim, M. & In, J. Does the minimal occlusive volume technique provide adequate endotracheal tube cuff pressure to prevent air leakage? A prospective, randomized, crossover clinical study. Anesth. Pain Med. 15, 365–370. https://doi.org/10.17085/apm.20020 (2020).

    Google Scholar 

  19. Rello, J. et al. Pneumonia in intubated patients: role of respiratory airway care. Am. J. Respir. Crit Care Med. 154, 111–115. https://doi.org/10.1164/ajrccm.154.1.8680665 (1996).

    Google Scholar 

  20. Dullenkopf, A., Gerber, A. & Weiss, M. Fluid leakage past tracheal tube cuffs: evaluation of the new microcuff endotracheal tube. Intensive Care Med. 29, 1849–1853. https://doi.org/10.1007/s00134-003-1933-6 (2003).

    Google Scholar 

  21. Monsel, A. et al. Tapered-cuff endotracheal tube does not prevent early postoperative pneumonia compared with Spherical-cuff endotracheal tube after major vascular surgery: A randomized controlled trial. Anesthesiology 124, 1041–1052. https://doi.org/10.1097/aln.0000000000001053 (2016).

    Google Scholar 

  22. Vu Quoc, D. et al. Effectiveness of continuous endotracheal cuff pressure control for the prevention of Ventilator-Associated respiratory infections: an Open-Label Randomized, controlled trial. Clin. Infect. Dis. 74, 1795–1803. https://doi.org/10.1093/cid/ciab724 (2022).

    Google Scholar 

  23. Bolzan, D. W. et al. Clinical use of the Volume-Time curve for endotracheal tube cuff management. Respir. Care. 59, 1628–1635. https://doi.org/10.4187/respcare.02683 (2014).

    Google Scholar 

  24. Krishna, S. G. et al. Cuffed endotracheal tubes in children: the effect of the size of the cuffed endotracheal tube on intracuff pressure. Pediatr. Anesth. 27, 494–500. https://doi.org/10.1111/pan.13099 (2017).

    Google Scholar 

  25. Ban, M. G. et al. Accuracy of pilot balloon palpation for cuff pressure assessment in small versus large sized tubes: a prospective non-randomized observational study. Sci. Rep. https://doi.org/10.1038/s41598-023-32704-3 (2023).

    Google Scholar 

  26. Li, S. et al. Factors Associated with Age-Related Changes in Non-Smoking Urban Men and Women in China Determined by Low-Dose Computed Tomography Imaging. Med. Sci. Monit. https://doi.org/10.12659/msm.931006 (2021).

    Google Scholar 

  27. Sakai, H. et al. Age-related changes in the trachea in healthy adults. Adv. Exp. Med. Biol. 662, 115–120. https://doi.org/10.1007/978-1-4419-1241-1_16 (2010).

    Google Scholar 

  28. Saracoglu, A., Dal, D., Pehlivan, G. & Gogus, F. Y. The professional experience of anaesthesiologists in proper inflation of laryngeal mask and endotracheal tube cuff. Turkish J. Anaesthesiol. Reanimation. 42, 234–238. https://doi.org/10.5152/tjar.2014.87487 (2014).

    Google Scholar 

  29. Maboudi, A., Abtahi, H., Hosseini, M., Tamadon, A. & Safavi, E. Accuracy of endotracheal tube cuff pressure adjustment by fingertip palpation after training of intensive care unit nurses. Iran. Red Crescent Med. J. 15, 381–384. https://doi.org/10.5812/ircmj.4164 (2013).

    Google Scholar 

  30. Murugiah, U. R. et al. Knowledge acquisition and retention among nurses after an educational intervention on endotracheal cuff pressure. Nurs. Crit. Care. 26, 363–371. https://doi.org/10.1111/nicc.12600 (2021).

    Google Scholar 

  31. Girling, K. J., Bedforth, N. M., Spendlove, J. L. & Mahajan, R. P. Assessing neuromuscular block at the larynx: the effect of change in resting cuff pressure and a comparison with video imaging in anesthetized humans. Anesth. Analg. 88, 426–431. https://doi.org/10.1097/00000539-199902000-00038 (1999).

    Google Scholar 

  32. Sunaga, H., Zhang, Y., Savarese, J. J. & Emala, C. W. Gantacurium and CW002 do not potentiate muscarinic Receptor-mediated airway smooth muscle constriction in Guinea pigs. Anesthesiology 112, 892–899. https://doi.org/10.1097/ALN.0b013e3181d32016 (2010).

    Google Scholar 

  33. Jooste, E., Zhang, Y. & Emala, C. W. Neuromuscular blocking agents’ differential bronchoconstrictive potential in Guinea airways. Anesthesiology 106, 763–772. https://doi.org/10.1097/01.anes.0000264763.48920.c9 (2007).

    Google Scholar 

  34. Hou, V. Y., Hirshman, C. A. & Emala, C. W. Neuromuscular relaxants as antagonists for M2 and M3 muscarinic receptors. Anesthesiology 88, 744–750. https://doi.org/10.1097/00000542-199803000-00026 (1998).

    Google Scholar 

  35. Milchert, M. et al. Skeletal muscle relaxants inhibit rat tracheal smooth muscle tone < i > In vitro. J. Physiol. Pharmacol. 60, 5–11 (2009).

    Google Scholar 

  36. Cembala, T. M., Sherwin, J. D., Tidmarsh, M. D., Appadu, B. L. & Lambert, D. G. Interaction of neuromuscular blocking drugs with Recombinant human m1-m5 muscarinic receptors expressed in Chinese hamster ovary cells. Br. J. Pharmacol. 125, 1088–1094. https://doi.org/10.1038/sj.bjp.0702166 (1998).

    Google Scholar 

  37. Nishino, T., Sugimori, K., Hiraga, K. & Honda, Y. Effects of tracheal irritation and hypercapnia on tracheal smooth muscle in humans. J. Appl. Physiol. (Bethesda Md. : 1985). 69, 419–423. https://doi.org/10.1152/jappl.1990.69.2.419 (1990).

    Google Scholar 

  38. Ishikawa, T., Sekizawa, S. & Sant’ Ambrogio, F. B. Sant’ Ambrogio, G. Endotracheal cuff pressure as an index of airway smooth muscle activity: comparison with total lung resistance. Respir. Physiol. 112, 175–184. https://doi.org/10.1016/s0034-5687(98)00029-2 (1998).

    Google Scholar 

  39. Sen, O. et al. Effects of pressure-controlled and volume-controlled ventilation on respiratory mechanics and systemic stress response during laparoscopic cholecystectomy. Springerplus 5 https://doi.org/10.1186/s40064-016-1963-5 (2016).

  40. Pitts, R. et al. Variables affecting leakage past endotracheal tube cuffs: a bench study. Intensive Care Med. 36, 2066–2073. https://doi.org/10.1007/s00134-010-2048-5 (2010).

    Google Scholar 

  41. Zanella, A. et al. Fluid leakage across tracheal tube cuff, effect of different cuff material, shape, and positive expiratory pressure: a bench-top study. Intensive Care Med. 37, 343–347. https://doi.org/10.1007/s00134-010-2106-z (2011).

    Google Scholar 

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Funding

The work was supported by grants from the Natural Science Foundation of Hunan Province in China (No. 2019JJ50933) and the National Natural Science Foundation of China (No. 82101319).

Author information

Authors and Affiliations

  1. Department of Anesthesiology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, China

    Heqi Peng, Zhaohui Tang, Yalin Li, Qulian Guo, Wangyuan Zou & Yingqi Weng

  2. National Clinical Research center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, China

    Zhaohui Tang, Qulian Guo, Wangyuan Zou & Yingqi Weng

  3. Department of Anesthesiology, People’s Hospital of Ningxiang City, Ningxiang, China

    Yalin Li

  4. Operation Office, Xiangya Public Health, Central South University, Changsha, China

    Wei Zhang

  5. Department of Anesthesiology, The Third Xiangya Hospital, Central South University, Changsha, China

    Kaiming Duan

  6. Department of Anesthesiology, Second Xiangya Hospital, Central South University, Changsha, China

    Hong Zheng

  7. Faculty of Anesthesiology, Changhai Hospital, Shanghai, China

    Lulong Bo

  8. Department of Anesthesiology, Peking University First Hospital, Beijing, China

    Yilin Zheng

  9. Department of Anesthesiology, Daping Hospital, Army Medical University, Chongqing, China

    Peng Wu

  10. Department of Anesthesiology, The Second Affiliated Hospital of Dalian Medical University, Dalian, China

    Jiaxin Tian

  11. Department of Anesthesiology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, China

    Yajuan Han

  12. Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, Guiyang, China

    Xiaohua Zou

  13. Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China

    Gang Chen

  14. Department of Anesthesiology and Perioperative Medicine, Henan Provincial People’s Hospital, People’s Hospital of Zhengzhou University, Zhengzhou, China

    Jun Xu

  15. Department of Anesthesiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China

    Jianqiang Guan

  16. Department of Anesthesiology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China

    Xuezheng Zhang

  17. Department of Anaesthesia, The Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine, Hangzhou, China

    Jianliang Sun

  18. Department of Anesthesiology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China

    Yuekun Shen

  19. Department of Anesthesiology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China

    Mao Zhou

  20. Department of Anesthesiology, Fujian Provincial Hospital, Shengli Clinic Medical College of Fujian Medical University, Fuzhou, China

    Shu Zheng

  21. Department of Anesthesiology, Tianjin Hospital, Tianjin, China

    Hui Wang

  22. Department of Anesthesiology, Qinghai Provincial People’s Hospital, Xining, China

    Hongmei Ma

Authors
  1. Heqi Peng
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  2. Zhaohui Tang
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  3. Yalin Li
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  4. Wei Zhang
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  5. Kaiming Duan
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  6. Hong Zheng
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  7. Lulong Bo
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  8. Yilin Zheng
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  9. Peng Wu
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  10. Jiaxin Tian
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  11. Yajuan Han
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  12. Xiaohua Zou
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  13. Gang Chen
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  19. Mao Zhou
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  23. Qulian Guo
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  24. Wangyuan Zou
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  25. Yingqi Weng
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Contributions

Study conception and design: YQW, ZHT, QLG ,Patient recruitment and Data collection: YQW, HQP, ZHT, YLL, KMD, HZ, LLB, YLZ, PW, JXT, YJH, XHZ, GC, JX, JQG, XZZ, JLS, YKS, MZ, SZ, HW, HMMData analysis: YQW, HQP, ZW, Manuscript preparation: YQW, HQP, Manuscript editing: YQW, HQP and WYZ, Study supervision: YQW, ZHT.

Corresponding author

Correspondence to Yingqi Weng.

Ethics declarations

Competing interests

The authors declare no competing interests.

Ethical approval

This study was approved by the medical ethics committee in every hospital and registered in the Chinese Clinical Trial Registry on March 21th, 2019 (The Investigation of tracheal tube cuff pressure in patients with tracheal intubation under general anesthesia, ChiCTR1900022038, https://www.chictr.org.cn/showproj.html?proj=36902).

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Peng, H., Tang, Z., Li, Y. et al. The investigation of initial endotracheal tube cuff pressures in the operating room: a multi-center cross-sectional study in China. Sci Rep (2026). https://doi.org/10.1038/s41598-026-37279-3

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  • Received: 16 April 2025

  • Accepted: 21 January 2026

  • Published: 01 February 2026

  • DOI: https://doi.org/10.1038/s41598-026-37279-3

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Keywords

  • Endotracheal tube cuff pressure
  • Cross-sectional study
  • General anesthesia
  • Risk factors
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