An endotracheal tube is a flexible plastic tube inserted through the mouth or nose and into the windpipe to keep a patient’s airway open and allow mechanical ventilation. It is one of the most commonly used devices in emergency medicine, surgery, and intensive care, serving as the primary means of securing an airway when a person cannot breathe adequately on their own. Despite its apparent simplicity, the tube’s design, placement, and management involve a surprising number of clinical decisions that directly affect patient outcomes, from infection risk to long-term airway damage.
When an Endotracheal Tube Is Needed
The reasons for placing an endotracheal tube generally fall into a handful of categories. A patient may be unable to keep their airway open on their own, as when the tongue falls back toward the throat during unconsciousness or when swelling from burns blocks the upper airway. The airway may need protection from aspiration, particularly in trauma patients with oral bleeding, people with a full stomach, or those with severe gastroesophageal reflux. Oxygenation failure, marked by falling oxygen saturation and signs of obstruction in the lungs, is another common trigger. And sometimes intubation is preemptive: if a patient’s condition is deteriorating and respiratory failure looks likely, placing the tube early can prevent a crisis.1IntechOpen. Indications for Endotracheal Intubation
Not every breathing emergency requires intubation, though. Alternatives like face masks, laryngeal mask airways, and other supraglottic devices can bridge the gap in some situations. The endotracheal tube remains the gold standard when the airway needs definitive, long-term protection, particularly in patients who will be on a ventilator for hours or days.
How the Tube Is Designed
Most endotracheal tubes are made of polyvinyl chloride (PVC) and are curved to follow the natural path from the mouth through the throat to the trachea. They come in a range of inner diameters, typically from about 2.5 mm for neonates up to 9 mm or larger for adults. The size matters more than you might expect: each one-millimeter decrease in inner diameter can roughly double the work of breathing through the tube, because airflow resistance rises steeply in narrow channels.2CHEST. Pressure Support Compensation for Inspiratory Work Due to Endotracheal Tubes and CPAP Devices That means choosing a tube that is too small can leave a patient struggling to breathe even while connected to a ventilator, and larger tubes are generally preferred when the patient’s anatomy allows it.3PubMed Central. Effect of endotracheal tube size on airway resistance and dynamic lung compliance
Near the tip, most tubes have a small side hole called a Murphy eye, which provides a backup path for airflow if the main opening gets blocked by the tracheal wall or secretions. However, not all tubes have one. A study comparing tubes from different manufacturers found that about 14% of the tubes examined lacked a Murphy eye entirely.4PubMed Central. Characteristics of endotracheal tube design of different brands are related to proper endotracheal tube position in pediatrics: a descriptive study The same study also found wide variation in the placement of depth markings on tubes of the same size across brands, with the distance from the vocal cord marking to the tip ranging from 10 to over 40 mm. That inconsistency is clinically relevant because clinicians use those markings to judge how deep the tube sits in the airway.
The Cuff and Why Its Pressure Matters
Most adult endotracheal tubes have an inflatable balloon, called a cuff, near the tip. Once the tube is positioned in the trachea, the cuff is inflated to create a seal against the tracheal wall. This seal serves two purposes: it prevents air from leaking out around the tube during ventilation, and it blocks fluids from the throat from draining down into the lungs.
The catch is that the cuff presses directly against the delicate lining of the trachea, and too much pressure can cut off blood flow to that tissue. Research has shown that cuff pressures above about 30 cm of water impair mucosal blood flow, which can lead to tissue damage.5PubMed Central. Endotracheal cuff pressure and tracheal mucosal blood flow: endoscopic study of effects of four large volume cuffs The type of cuff also makes a difference. Stiffer cuffs reduce blood flow more than softer, more compliant ones, and the damage is worst at the surface of the tracheal lining rather than in deeper tissue layers.6The American Journal of Surgery. Comparison of clinical and experimental characteristics of endotracheal tube cuffs Modern tubes use high-volume, low-pressure cuffs specifically to spread the sealing force over a larger area and minimize this ischemic damage. Still, even with modern cuffs, some degree of airway injury is common after intubation, and prolonged intubation occasionally results in tracheal stenosis, a narrowing of the airway that can require surgical correction.7PubMed Central. Post intubation tracheal stenosis
Confirming the Tube Is in the Right Place
One of the most critical moments during intubation is verifying that the tube has actually gone into the trachea and not the esophagus. An esophageal placement, if unrecognized, means the patient gets no oxygen to their lungs and can die within minutes. Physical examination alone, such as listening to the chest with a stethoscope, is not reliable enough. In emergency intubations, auscultation has shown a sensitivity of about 94% and a specificity of only 83% for detecting correct placement, meaning it misses some esophageal intubations and falsely flags some correct ones.8PubMed. Comparison of three different methods to confirm tracheal tube placement in emergency intubation
The current standard is waveform capnography, which detects carbon dioxide in the patient’s exhaled breath. If the tube is in the trachea, you get COâ‚‚ on every breath; if it is in the esophagus, you don’t. In patients with a pulse, capnography achieves near-perfect accuracy. The American College of Emergency Physicians recommends it as the primary confirmation method and specifically warns against relying solely on physical exam findings, pulse oximetry, or chest X-rays.9Annals of Emergency Medicine. ACEP Clinical Policy: Procedures for Endotracheal Intubation in the Adult Emergency Department
Capnography has a weak spot, though: cardiac arrest. When the heart isn’t pumping blood to the lungs, COâ‚‚ production drops and capnography becomes less sensitive. In those situations, ultrasound and esophageal detector devices serve as backups.10Annals of Emergency Medicine. ACEP Clinical Policy: Procedures for Endotracheal Intubation in the Adult Emergency Department Ultrasound is gaining traction as a rapid alternative. In one hospital study, it confirmed tube position about 16 seconds faster than capnography while achieving comparable accuracy.11PubMed Central. Ultrasonography Imaging versus Waveform Capnography in Detecting Endotracheal Tube Placement during Intubation at a Tertiary Hospital
Confirmation is not a one-time event. A properly placed tube can shift if the patient is moved, turned, or transported. Continuous waveform capnography is considered ideal for ongoing monitoring, and tube position should be rechecked any time a patient’s condition changes suddenly.12Annals of Emergency Medicine. ACEP Clinical Policy: Procedures for Endotracheal Intubation in the Adult Emergency Department
Infection and the Problem of Biofilm
The endotracheal tube creates a direct pathway from the outside world into the lower airways, bypassing most of the body’s natural defenses. This is a major reason why ventilator-associated pneumonia (VAP) is one of the most common infections in intensive care. The tube contributes in two specific ways. First, the cuff never forms a perfectly smooth seal. Folds in the deflated or partially inflated cuff create tiny channels through which bacteria-laden secretions from the throat can trickle down into the trachea, a process called microaspiration. Second, bacteria colonize the inner surface of the tube itself, forming a slimy layer called biofilm that is extremely resistant to antibiotics and the immune system.13PubMed Central. The tracheal tube: gateway to ventilator-associated pneumonia
Researchers have been working on antimicrobial coatings to tackle the biofilm problem. One approach uses silver-containing hydrogel coatings applied to the tube surface. In laboratory testing, silver-loaded coatings prevented biofilm formation by Pseudomonas aeruginosa, one of the bacteria most commonly implicated in VAP.14Colloid and Interface Science Communications. Antibacterial endotracheal tube with silver-containing double-network hydrogel coating Another technique involves a rapid ten-second coating process using specific solvents that creates an antimicrobial surface effective against E. coli without the toxicity associated with silver nitrate.15Scientific Reports. Novel ten second antimicrobial coating for endotracheal tubes to prevent ventilator associated pneumonia These technologies are still largely in the experimental stage, but they represent a meaningful shift in how the field thinks about tube design, treating the tube itself as part of the infection prevention strategy.
Pediatric Tubes and the Cuffed Versus Uncuffed Debate
For decades, the standard practice in children was to use uncuffed endotracheal tubes. The reasoning was based on an older understanding of pediatric anatomy: the child’s larynx was thought to be narrowest at a ring of cartilage called the cricoid, making it naturally funnel-shaped, so the airway itself would form a seal around an uncuffed tube. Imaging studies conducted since the 2000s have overturned that idea, showing that the pediatric larynx is actually narrowest at the vocal cords, similar to adults, and more cylindrical in shape.16PubMed Central. Pediatric Application of Cuffed Endotracheal Tube
This anatomical correction, combined with improvements in cuff design, has shifted practice. Cuffed tubes in children reduce air leak during ventilation and lower the risk of aspiration. In a study comparing the two types in young children during anesthesia, cuffed tubes selected using an appropriate sizing formula fit correctly in 99% of patients, compared to 77% for uncuffed tubes chosen by the traditional method. Importantly, the rate of croup symptoms afterward was essentially the same between the two groups.17Anesthesiology. Comparison of Cuffed and Uncuffed Endotracheal Tubes in Young Children during General Anesthesia The American Heart Association now recommends cuffed tubes for pediatric use.18PubMed Central. Pediatric Application of Cuffed Endotracheal Tube
In neonates, the picture is less clear. A Cochrane review found that cuffed tubes may reduce the need for reintubation compared with uncuffed tubes, but the evidence was based on a single small study and rated as very low certainty. No neonates in the study required surgery for airway complications in either group, but endoscopy to confirm findings was not available.19PubMed Central. Cuffed versus uncuffed endotracheal tubes for neonates For the smallest patients, the evidence simply has not caught up yet.
Difficult Airways and Video Laryngoscopy
Not every intubation goes smoothly. Patients with short necks, limited mouth opening, large tongues, facial trauma, or obesity can present a “difficult airway” where passing the tube through the vocal cords becomes challenging or impossible with standard equipment. Video laryngoscopes, which use a camera on the blade to display the airway on a screen, have become a major tool for these cases. They consistently provide a better view of the vocal cords than traditional direct laryngoscopy.
Seeing the cords, however, does not always mean the tube slides in easily. The sharply curved blades on some video laryngoscopes (called hyperangulated blades) give an excellent view but create a steep angle that makes threading the tube difficult. Clinicians use either a preshaped rigid stylet inside the tube or a flexible guide called a bougie to navigate the curve. A randomized trial comparing the two approaches with a hyperangulated blade found that first-attempt success was 98% with a bougie versus 88% with a stylet.20PubMed. Comparison of the success rate of tracheal intubation between stylet and bougie with a hyperangulated videolaryngoscope: a randomised controlled trial For awake intubation in patients with anticipated difficult airways, video laryngoscopy combined with a video stylet has also shown shorter intubation times.21Trends in Anaesthesia and Critical Care. Bougie-assisted C-MAC video laryngoscope versus C-MAC video stylet for awake endoscopic intubation in anticipated difficult airways: A randomized controlled trial
Endotracheal Tubes in Cardiac Arrest and Prehospital Settings
Whether paramedics and emergency crews should use endotracheal tubes or simpler supraglottic airway devices during out-of-hospital cardiac arrest has been one of the more contentious debates in emergency medicine. Endotracheal intubation provides a more secure airway, but it takes longer and requires more skill. Supraglottic devices can be placed faster and by providers with less training.
The evidence is mixed. One large study found that successful endotracheal intubation in the field was associated with higher rates of return of spontaneous circulation and survival to hospital discharge compared to supraglottic airways.22PubMed Central. Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest But another study found that neurological outcomes were similar between the two approaches, while noting that the time from collapse to airway placement was about a minute and a half longer with intubation. In that study, speed of airway placement mattered more than the type of device: each minute of delay was associated with worse neurological outcomes.23PubMed Central. Comparison of supraglottic airway versus endotracheal intubation for the pre-hospital treatment of out-of-hospital cardiac arrest A randomized trial in Taipei found no significant difference in sustained return of circulation, survival to discharge, or good neurological outcomes between the two methods.24JAMA Network Open. Effect of Placement of a Supraglottic Airway Device vs Endotracheal Intubation on Return of Spontaneous Circulation in Adults With Out-of-Hospital Cardiac Arrest in Taipei
The emerging consensus is that the skill and speed of the person placing the airway may matter as much as the device itself. A paramedic who can intubate quickly and correctly probably provides a benefit. A less experienced provider who struggles with the tube for several minutes may do better with a supraglottic device.
What Happens When the Tube Comes Out
Extubation, the planned removal of the tube, carries its own risks. The most worrying complication is laryngeal edema, swelling around the vocal cords that can narrow the airway enough to cause stridor (a high-pitched breathing sound) or even require reintubation. In one study of over 460 patients, about 4% developed post-extubation stridor requiring treatment, and about 1.5% needed to be reintubated.25PubMed. The endotracheal tube cuff-leak test as a predictor for postextubation stridor Female patients, those intubated for longer periods, and those whose tube was large relative to their airway were at higher risk.
Clinicians often use a cuff-leak test before extubation: they deflate the cuff and check whether air can escape around the tube. The idea is that little or no leak suggests the airway has swollen around the tube. In practice, the test is imperfect. Its ability to predict stridor varies widely across studies, and a failed test does not mean extubation will fail. Many patients with a small or absent leak are extubated successfully.26PubMed Central. The cuff-leak test: what are we measuring? One study found that using a leak cutoff of about 15% distinguished reasonably well between patients who needed reintubation and those who didn’t, but the positive predictive value was only 25%, meaning three out of four patients who “failed” the test did not actually need reintubation.27PubMed. The cuff leak test to predict failure of tracheal extubation for laryngeal edema Current practice generally treats the test as one piece of information rather than a gate that determines whether extubation proceeds.
Keeping the Tube in Place
Unplanned extubation, where the tube comes out accidentally, is a persistent problem in intensive care. Risk factors include male sex, delirium, agitation, physical restraint use, higher consciousness levels, poor tube fixation, and bedside handling. The timing is not random: unplanned extubations happen more often at night, around nursing shift changes, and during the weaning phase when ventilator support is being reduced.28PubMed Central. Prevention of unplanned endotracheal extubation in intensive care unit: An overview of systematic reviews
Tubes can be secured with adhesive tape, commercial tube holders, or ties. Despite years of research, no single fixation method has been shown to be clearly superior. Weak fixation, such as a single thin strip of tape, is consistently associated with higher rates of accidental removal.29PubMed Central. Unplanned extubations in Intensive Care Unit: evidences for risk factors. A literature review The practical takeaway is that any method needs to be applied carefully and checked regularly, and that sedation management and patient monitoring play at least as large a role as the tape itself.
Sedation is the other side of the equation. An awake or lightly sedated patient with a tube in their throat will cough, gag, and may try to pull it out. Dexmedetomidine, a sedative that allows patients to remain arousable while suppressing airway reflexes, has been shown to improve tube tolerance and reduce coughing compared with placebo, while also cutting morphine requirements substantially.30Egyptian Journal of Anaesthesia. Efficacy of Dexmedetomidine for endotracheal tube tolerance, analgesia and sedation – A prospective randomised double blind controlled trial A single dose at the time of extubation also reduces coughing during tube removal, which can matter for patients at risk of elevated intracranial or intraocular pressure.31PubMed. Single-dose dexmedetomidine attenuates airway and circulatory reflexes during extubation
Endotracheal Tubes in Veterinary Medicine
The same basic principles of endotracheal intubation apply to animals, but anatomy creates unique challenges. Dogs are intubated regularly for surgery, and sizing the tube correctly matters just as much as in humans. A study in Beagles found that a tube with an outer diameter of about 70% of the tracheal diameter measured on a chest X-ray provided the best fit, balancing ease of insertion with an adequate seal.32PubMed. Selection of appropriate endotracheal tube size using thoracic radiography in Beagle dogs
Some species are far harder to intubate. Llamas, for instance, produce heavy salivary secretions and have oral anatomy that makes it difficult to see the larynx. The standard technique involves threading a stylet into the trachea first, then sliding the tube over it. Researchers have also evaluated a retrograde approach, where a guide wire is inserted through the skin of the neck into the trachea and passed upward through the mouth, and the tube is then threaded over it in reverse. Both methods took a similar amount of time, but the retrograde technique required fewer attempts to place the tube successfully.33PubMed Central. Comparison of endotracheal intubation techniques in llamas
The Environmental Cost of Single-Use Tubes
Endotracheal tubes are overwhelmingly single-use, disposable PVC products. In a specialty that uses enormous volumes of plastic, they are one of many items that go straight into clinical waste after a single patient encounter. The shift from reusable to single-use devices across anesthesia was driven by concerns about infection transmission, but the scientific evidence supporting that shift for many items, including tubes, is weaker than commonly assumed.34PubMed. Moving towards green anaesthesia: Are patient safety and environmentally friendly practices compatible? A focus on single-use devices Reusable alternatives tend to cost less over time and produce less waste, water consumption, and greenhouse gas emissions. The tension between infection control and environmental sustainability is an active area of discussion in anesthesiology, though regulatory inertia and liability concerns have so far kept most hospitals on the disposable path.