Following tracheal intubation, mucus flow is reversed in the semirecumbent position: possible role in the pathogenesis of ventilator-associated pneumonia
Abstract
OBJECTIVES: Critically ill intubated patients are positioned in the semirecumbent position to prevent pneumonia. In tracheally intubated sheep, we investigated the effects of gravitational force on tracheal mucus transport and on bacterial colonization of the respiratory system. DESIGN: Prospective randomized animal study. SETTING: Animal research facility at the National Institutes of Health. SUBJECTS: Sixteen healthy sheep. INTERVENTIONS: Spontaneously breathing or mechanically ventilated sheep were randomized to be positioned with the orientation of the trachea above (40 degrees, trachea-up) or below (5 degrees, trachea-down) horizontal. MEASUREMENTS AND MAIN RESULTS: Tracheal mucus velocity was measured through radiographic tracking of radiopaque tantalum disks, insufflated into the trachea. After 24 hrs, sheep were euthanized, and samples from the airways and lungs were taken for microbiological analysis. The proximal trachea was colonized in all sheep. In trachea-down sheep, all mucus moved toward the glottis at a mean velocity of 2.1 +/- 1.1 mm/min. When mucus reached the endotracheal tube, it either entered the endotracheal tube or was lodged at the inflated endotracheal tube cuff. In all trachea-up sheep, abnormal tracheal mucus clearance was found. Mucus, mostly on the nondependent part of the trachea, moved toward the glottis at an average velocity of 2.2 +/- 2.0 mm/min and constantly accumulated at the inflated endotracheal tube cuff. From the proximal trachea, mucus eventually moved toward the lungs on the dependent part of the trachea, leading to an "intratracheal route" of colonization of the lungs. Pneumonia was found in 6/8 of trachea-up sheep and the same microorganisms were isolated from the lungs and the proximal trachea. No pneumonia was found in trachea-down sheep (p = .007). CONCLUSIONS: The study indicates that following tracheal intubation gravitational force influences tracheal mucus clearance. When the trachea is oriented above horizontal, a flow of mucus from the proximal trachea toward the lungs is highly associated with bacterial colonization of the airways and pneumonia.
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Elevation of the head of the bed decreases immigration of gastric microbiota to the lungs but also impedes microbial elimination from the lungs.
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Raising the head of the patient's bed decreases immigration to the lungs of gastric microbiota compared with supine positioning, but this practice also compromises microbial elimination from the lungs.
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From The microbiome and critical illness (2016) · cites this paper as [59]
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- Authors
- Li Bassi, G., Zanella, A., Cressoni, M., Stylianou, M., & Kolobow, T.
- Affiliations
- National Institutes of Health (US)
- Venue
- Critical Care Medicine
- Published
- 2008-02
- Volume
- 36
- Issue
- 2
- Pages
- 518-525
- ISSN
- 0090-3493 (ISSN-L)
- OpenAlex
- W2008828658
- Cited by
- 119
- References
- 17
- Citations by year
- 2026: 3 · 2025: 5 · 2024: 7 · 2023: 3 · 2022: 6 · 2021: 4 · 2020: 2 · 2019: 12 · 2018: 7 · 2017: 6 · 2016: 4 · 2015: 5 · 2014: 8 · 2013: 12 · 2012: 8
- FWCI
- 7.25
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Critical Care Medicine (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Health Sciences › Medicine › Critical Care and Intensive Care Medicine › Nosocomial Infections in ICU
- Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Respiratory Support and Mechanisms
- Health Sciences › Medicine › Anesthesiology and Pain Medicine › Airway Management and Intubation Techniques
- Keywords
- ventilator-associated pneumonia, endotracheal intubation, mucus clearance, gravitational force, semi-recumbent position, endotracheal tube cuff, bacterial colonization, sheep model, mechanical ventilation
- MeSH terms
- Animals, Female, Gravitation, Intubation, Intratracheal, Mucociliary Clearance, Mucus, Posture, Respiration, Artificial, Rheology, Sheep, Colony Count, Microbial, Pneumonia, Ventilator-Associated
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