Endotracheal Tube (ET)


Article Author:
Rami Ahmed


Article Editor:
Tanna Boyer


Editors In Chief:
Russell McAllister
Jason Widrich
Daniel Sizemore


Managing Editors:
Avais Raja
Orawan Chaigasame
Khalid Alsayouri
Kyle Blair
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beenish Sohail
Hajira Basit
Phillip Hynes
Sandeep Sekhon


Updated:
6/1/2019 4:37:44 PM

Introduction

The endotracheal tube (ETT) was first reliably used in the early 1900s.[1] In its simplest form, it is a tube constructed of polyvinylchloride (PVC) that is placed between the vocal cords through the trachea to provide oxygen and inhaled gases to the lungs.  It also serves to protect the lungs from contamination such as gastric contents and blood. The advancement of the endotracheal tube has closely followed advancements in anesthesia and surgery.[2] Modifications have been made to minimize aspiration, isolate a lung, administer medications, and prevent airway fires. Despite advances with the endotracheal tube, more research to optimize its use is necessary. For example, ventilator-associated pneumonia (VAP) is a major concern, and the ETT itself is felt to be a primary agent for the development of VAP.[2]

Pediatric ETT’s are sized by age with options across the spectrum from premature infants to adult size teenage children. Historically, pediatric endotracheal tubes were uncuffed for fear that the pressure from the cuff would damage the trachea via pressure necrosis as the airway just below the vocal cords (cricoid cartilage) is the most narrow part in children.  In adults, the narrowest portion of the airway is the vocal cords.  Except for neonatal patients, this practice has largely been discontinued in favor of cuffed pediatric ETT’s.[3] A few well-established criteria are available to aide in ETT size selection.

Anatomy

The tube:

The endotracheal tube has a length and diameter. The endotracheal tubes size (“give me a 6.0 tube”) refers to its internal diameter in millimeters (mm). The ETT will typically list both the inner diameter and outer diameter on the tube (for example, a 6.0 endotracheal tube will list both the internal diameter, ID 6.0,  and outer diameter, OD 8.8). The narrower the tube, the greater resistance to gas flow. Medical providers thus should select the largest tube that is appropriate for the patient; this is critically important to the spontaneously breathing patient who will have to work harder to overcome the increased resistance (a size 4 ETT has 16 more times resistance to gas flow than a size 8 ETT). The ETT is measured from the distal end of the tube and is typically marked in 2 cm increments. After successfully intubating the patient the depth of the endotracheal tube ending at the teeth or lips should be noted. This depth provides a baseline measurement to ensure the tube has not traveled out of the trachea or deeper into the trachea with patient movement or transport. PVC is not radiopaque, and thus a radiopaque linear material is in included throughout the length of the tube to make it easier to visualize the placement on x-ray. Ideally, the distal tip of the ETT is 4 cm (+/- 2 cm) above the carina on chest x-ray in adults.[4] Should you desire to perform bronchoscopy on an adult patient with a standard bronchoscope (diameter 5.7 mm with a 2 mm suction channel) the patient typically needs to be intubated with at least 7.5-8.0 size ETT; ETTs larger than 8.0 are available and used for bronchoscopy.[5] The typical depth of the endotracheal tube is 23 cm for men and 21 cm for women, measured at the central incisors. The average size of the tube for an adult male is 8.0, and an adult female is 7.0, though this is somewhat an institution dependent practice. Pediatric tubes are sized using the equation: size = ((age/4) +4) for uncuffed ETTs, with cuffed tubes being one-half size smaller.[6]  Typically a pediatric ETT is taped at a depth of 3 x the tube size in a child (i.e., a 4.0 ETT commonly gets taped at around 12cm depth).  

The cuff:

A cuff is an inflatable balloon at the distal end of the ETT. Pediatric ETTs are produced with and without cuffs. The inflated cuff produces a seal against the tracheal wall; this prevents gastric contents from entering the trachea and facilitates the execution of positive pressure ventilation. The cuff inflates by attaching an appropriate size syringe (10 to 20 ml for adult ETT) to the pilot balloon. The syringe provides air under pressure and inflates both the pilot balloon and the cuff. Once the cuff inflates, the syringe needs to be removed, or the air in the cuff may redistribute back to the syringe and deflate the cuff. Palpating the firmness of the pilot balloon is a good estimation to the pressure in the cuff. Cuff manometers are available but not common in clinical use.  Ideal cuff pressure should be 20 cm H2O or less. If the pilot balloon does not hold air, it must be assumed the cuff of the ETT has been damaged and is non-functional.  Some ETTs have a low volume high-pressure cuff, but it is more common to find high volume low-pressure cuffs on ETTs in current medical practice.  

The bevel:

To facilitate placement through the vocal cords and to provide improved visualization ahead of the tip, the ETT has an angle or slant known as a bevel. As the endotracheal tube approaches the cords, the left facing bevel provides an optimal view.

The Murphy's eye:

ETTs have a built-in safety mechanism at the distal tip known as Murphy’s eye, which is another opening in the tube positioned in the distal lateral wall. If the distal end of the ETT should become obstructed by the wall of the trachea or by touching the carina, gas flow can still occur via Murphy's eye,  This prevents complete obstruction of the tube.

The connector:

ETT connectors attach the ETT to the mechanical ventilator tubing or an Ambu bag. For adult and pediatric ETTs, it is customary to use the universal 15 mm connector.

Indications

The main indication to use an endotracheal tube is to secure a definitive airway. A definitive airway is the placement of an ETT in the trachea with an inflated cuff below the vocal cords. The main reasons to secure a definitive airway are an inability to maintain airway patency, inability to protect the airway against aspiration, failure to ventilate, failure to oxygenate, and anticipation of a deteriorating course leading to respiratory failure.

Contraindications

The primary (relative) contraindications to the placement of an ETT in the oropharynx is severe airway trauma or obstruction that does not allow safe placement of the tube, severe cervical spine injury which requires complete immobilization, and those patients with Mallampati III/IV classification suggesting potentially difficult airway management.

The main contraindications to avoid placing an ETT with the nasotracheal approach include facial trauma, head trauma concerning for basilar skull fracture, active epistaxis, expanding neck hematoma, oropharyngeal trauma, and apneic patients.[7]

Equipment

Equipment necessary to optimize the use and function of the ETT:

  • Stylet
  • Syringe for cuff/pilot balloon
  • Universal 15 mm connector
  • End-tidal CO2 device

Personnel

In the ER it is common to have an RN available to push drugs (if needed).  The RN can function as a second person and can call for help if needed for an unanticipated difficult airway.  Some hospitals commonly have an RT help with taping of the ETT and ventilation once a patient is intubated.  

Preparation

Select an appropriate size endotracheal tube and remove it from the package. Lubricate the distal end and balloon (if not emergency placement). Attach a proper size syringe (10 to 20 cc) filled with air to the pilot balloon and test the balloon by blowing it up and then deflating it. Place a stylet into the ETT and bend it to an appropriate shape. Place the tube with the stylet and attached syringe back in the package ready for use. Repeat the same procedure with a tube one size smaller in case of difficult intubation. Set aside an end-tidal CO2 detector.

Complications

Several mechanical complications can occur with the ETT resulting in a loss of function. A defective balloon will result in a loss of ability to protect the airway from aspirate and may make mechanical ventilation difficult. The loss of the universal 15 mm connector (either missing or defective)  essentially makes the ETT nonfunctional as the mechanical ventilator or bag-valve-mask cannot interface with it.  Some complications from the physical placement of the tube include bleeding, infection, perforation of the oropharynx (especially with the use a rigid stylet), hoarseness (vocal cord injury), damage to teeth/lips, or esophageal placement.

Enhancing Healthcare Team Outcomes

An interprofessional team is necessary to make sure that an ETT is placed appropriately, especially in the emergency department setting. As there is not one definitive method to ensure appropriate ETT placement, an interprofessional team working together to confirm several means of tube placement is necessary to ensure optimal patient outcomes. For example, after emergent intubation in the emergency department, a respiratory therapist may ensure a good color change of the end-tidal CO2 detector while also securing the ETT. Simultaneously, nursing staff may auscultate over the lung fields and abdomen to ensure good quality, equal breath sounds in the thoracic cavity with absent breath sounds in the abdomen. The physician will be monitoring the pulse ox while ordering a stat portable chest x-ray to confirm placement of the tube. It has become more common and standard of care to have a constant waveform monitor for end tidal CO2 for intubated patients, especially in the OR and ICU.  Collaboration, closed-loop communication, and the principles of crisis resource management are necessary for the success of teams working in acute care environments.[8]


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Endotracheal Tube (ET) - Questions

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A high volume, low pressure cuff can do which of the following?



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A 65-year-old patient presents to the emergency department with massive hemoptysis. He is quickly intubated, and the healthcare practitioner reports significant continued bloody secretions during suctioning. The practitioner requests an emergent bronchoscopy. What is the minimum size of the endotracheal tube that is typically necessary for an adult standard bronchoscope?



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A 46-year-old female undergoes an uneventful exploratory laparotomy. Chest and abdominal x-rays are performed to evaluate for a lost sponge in the counts at the end of the case. The chest x-ray incidentally reveals that the endotracheal tube is sitting just at the carina. One of the trainee surgeons becomes worried and asks for the tube to be adjusted. However, the anesthetist does not show concern. Which of the following best explains why the anesthetist is unconcerned?



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A 2.5-year-old male is about to be intubated in the emergency room who has been admitted with status asmaticus. The child has a history of being born at 26 weeks gestation, chronic lung disease on inhaled steroids twice a day and albuterol nebulizers as needed, and seasonal allergies on montelukast. His condition is worsening and the bedside nurse calls for help. The bedside nurse pushes induction drugs and paralytic, and upon direct laryngoscopy, the provider has a grade 1 view of the entire vocal cords, however the 4.5 cuffed endotracheal tube will not pass. The patient is mask ventilated anda 4.0 cuffed endotracheal tube with a stylet is arranged. A second perfect view of the vocal cords with direct laryngoscopy is obtained, however the 4.0 cuffed endotracheal tube will not pass either. A 3.5 cuffed endotracheal tube is tried which does pass, albeit tightly. Which of the following best explains the reason for this problem recurring?



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A trauma patient was just dropped off from the emergency department (ED) to the intensive care unit (ICU). The resident covering the ICU overnight was just urgently paged to the patient's room because the bedside nurse and respiratory therapist are having trouble ventilating the patient. A quick physical exam reveals that the pilot balloon has been cut off of the endotracheal tube, causing a huge air leak and inability to properly ventilate the patient, who received a dose of a paralytic in the ED just prior to transport. The pulse oximeter is reading 93% and has been steadily in the low 90s during the 5-minute exam. What is the next best move?

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A 5-foot-2 inch tall 43-year-old woman has just been intubated in the emergency department. The respiratory therapist (RT) confirms + end-tidal CO2 and is taping the 6.0 cuffed endotracheal tube at 22 cm at the patient's teeth. On a follow up confirmatory chest x-ray, the left lung is found to be atelectatic. Which of the following best explains this finding?



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Endotracheal Tube (ET) - References

References

Szmuk P,Ezri T,Evron S,Roth Y,Katz J, A brief history of tracheostomy and tracheal intubation, from the Bronze Age to the Space Age. Intensive care medicine. 2008 Feb;     [PubMed]
Haas CF,Eakin RM,Konkle MA,Blank R, Endotracheal tubes: old and new. Respiratory care. 2014 Jun;     [PubMed]
Litman RS,Maxwell LG, Cuffed versus uncuffed endotracheal tubes in pediatric anesthesia: the debate should finally end. Anesthesiology. 2013 Mar;     [PubMed]
Salem MR, Verification of endotracheal tube position. Anesthesiology clinics of North America. 2001 Dec;     [PubMed]
Farrow S,Farrow C,Soni N, Size matters: choosing the right tracheal tube. Anaesthesia. 2012 Aug;     [PubMed]
Aker J, An emerging clinical paradigm: the cuffed pediatric endotracheal tube. AANA journal. 2008 Aug;     [PubMed]
Folino TB,Parks LJ, Intubation, Nasotracheal 2018 Jan;     [PubMed]
King AE,Conrad M,Ahmed RA, Improving collaboration among medical, nursing and respiratory therapy students through interprofessional simulation. Journal of interprofessional care. 2013 May;     [PubMed]

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