Endotracheal Intubation

 

Intubation is the process of placing a tube in a patient's airway to secure it against swelling, trauma, and foreign material. The Endotracheal route is considered the gold standard in intubation, both in the field and within the hospital. This section will review the reasons to intubate, the side effects, and the process of doing so.

 

Ways to intubate

Endotracheal intubation always results with a tube in the trachea, how it gets there is a matter of technique. There are many routes that are used both inside and outside of the hospital to place ET tubes. Each of these has near-identical indications, contraindications, and limitations. The challenge with all of the following methods is avoiding the accidental intubation of the esophagus. Therefore the rest of this section will focus on the "direct" method. The rest of the methods are included here for completeness and some will be reviewed in further sections.

Direct Laryngoscopy: The use of a metal tool to push down the tongue in combination with tilting back the head to allow for a direct look at the vocal cords. This method will be discussed in detail in this section.

Fiber Optic: The use of a metal tool with a camera on the end to allow for an easier direct look at the cords, great for patients with C-Spine injury or difficult pharyngeal anatomy.

Non-Visualized (nasal): The use of nasal anesthetics to pass a tube through the nare into the larynx, which is confirmed by listening for breath sounds or by a fiber-optic camera. 

Digital: The use of the fingers to palpate the epiglottis followed by direct passage of an ET tube into the trachea by feel alone. It is used in situations where patients are trapped and positioning them is impossible.

Lighted Stylette: The use of an extremely bright light attached to a tube that allows you to see a red shine through the neck if you are in the trachea and not the esophagus.

Indications, Contraindications, and Complications

INDICATIONS: The indications for intubation are focused around the airway: is the airway currently compromised beyond what bag-valve-mask can support? Or do you anticipate that the airway will become compromised? The exact indications for pre-hospital intubation are as follows:

• Respiratory failure (apnea) or inadequate respiration.
• Altered level of consciousness with abnormal breathing that is expected to deteriorate.
• Protection of the airway in a severely altered patient.
• A recent injury that may lead to airway obstruction (burn, anaphylaxis, head/neck trauma).

CONTRAINDICATIONS: The contraindications to intubation involve factors that increase the potential damage to pharyngeal structures that may occur. The most important ones to remember are as follows:

• Pathology or trauma involving the glottis or oropharynx that would make it difficult/impossible to pass an ET.
• Laryngeal fracture.
• Penetrating trauma to the upper airway.
• Severe upper airway edema from burns, infection, or anaphylaxis that may lead to laryngospasm if irritated further.
  • (Rapid aggressive airway management is preferred in these cases, i.e., early intubation, but is not always possible.)

COMPLICATIONS: The complications of intubation and ET tube placement are significant in number. Any intubation attempt must be preceded by a plan to deal with an issue in any major system of the body. While this list seems daunting, remember that a closed airway will kill a patient more quickly than many of the items listed here. 

Airway-related complications:

• Trauma to the lips, gums, teeth, or larynx
• Laryngospasm or Bronchospasm
• Perforation of the trachea
• Hypoxia

Systemic complications:

• Tachycardia or bradycardia
• Hypertension or Hypotension
• Elevation of intracranial pressure
• Perforation of the esophagus
• C-Spine trauma, Jaw dislocation, Laryngeal fracture

LIMITATIONS: The limits of endotracheal intubation are seen when there is a pathology that limits your ability to get the tube past the oropharynx and larynx. While the larynx is supported by cartilage rings that keep it open (barring severe trauma), the oropharynx/larynx is mostly made of soft tissue, which can swell and close off with little warning. This makes it difficult to intubate in the event of laryngospasm, laryngeal edema, severe facial/neck trauma, and in cases where visualizing the vocal cords is impossible.

RAPID SEQUENCE INTUBATION: When there is a need to protect the airway immediately or a danger of aspiration, the technique of rapid sequence intubation (RSI) involves the use of sedation or induced paralysis for speed without interference from the patient. 

SEDATION: Midazolam (Versed)--a benzodiazepine, which also has amnesic and retroamnesic effects.

Onset of action: 3-5 minutes IV. 
IV adult dosing: 0.5 - 2 mg over at least 2 minutes; can repeat every 2 to 3 minutes if needed up to 2.5-5 mg.

Hypotension is a common complication of sedation. This can be additive to bradycardia from the vagal response to intubation, so be aware.

Etomidate and Ketamine are the RSI sedatives with the best patient outcomes in regard to BP stability. Ketamine is special in that it has bronchodilatory and hypertensive effects making it useful in patients with asthma, hypotension, and anaphylaxis.

PARALYSIS: Succinylcholine (Anectine)--neuromuscular blocking agent, a paralytic.

Onset of action: 30–60 sec (via IV), 2–3 min (via IM) and duration of action: < 10 min (via IV), 10–30 min (via IM)]
IV adult dosing: 0.6 mg/kg (0.3 - 1.1 mg/kg).

CAUTION: Succinylcholine shouldn't be used in patients with blunt force trauma, burns, or crush injuries because these conditions can result in hyperkalemia and lead to cardiac arrest. Likewise, advanced renal failure. These scenarios can be additive to succinylcholine's adverse effect of causing hyperkalemia. 

 

Procedure for directly visualized (laryngoscope) intubation

The procedure for direct visualized tracheal intubation via laryngoscopy is as follows, learning this protocol is best done with direct practice on mannequins, as the best intubators can perform many of the below tasks by muscle memory:

1. Pre-oxygenate with 100% O2 for 30 seconds if at all possible. 
2. While oxygenating the patient, gather equipment including a correctly sized laryngoscope blade and handle (check to make sure light that the tip of the laryngoscope is white, tight, and bright); suction, safety glasses, a correct-size ET tube with stylet, syringes to inflate the pilot balloon on the ET, ETCO2 device, means to secure the tube after intubation, and water-soluble lubrication. 
   
   Also, don BSI due to the danger of biological exposure to the patient's secretions, exhalations, coughing and gagging. You need more than just gloves! Mask and face shield, please. Safety first. 

   When to Use a Straight Blade: A curved blade displaces the base of the tongue forward to see the cords; a straight blade lifts the epiglottis and moves the tongue to the left. A straight blade is used for tight arrangements, such as short/thick necks, obesity, or a large tongue. 

   Correct size of the ET tube is based on the internal (inside) diameter in mm of the tube. Duracher's formula for a CUFFED ETT is (age/4) + 3.5. This offers a precise method for sizing cuffed endotracheal tubes in children, refining the older Cole formula [(age/4) + 4.0] used for uncuffed endotracheal tubes. This adjustment helps minimize intubation attempts and manage cuff pressure to avoid airway damage. It's recommended to have ETTs 0.5 mm smaller or larger on hand for the best fit. Duracher's Formula is more accurate for CUFFED tube sizing. Click here for research article.
   
   PEDIATRIC
   ♦ According to the Merck Manual, for children aged 1-8: 
     • For UNCUFFED endotracheal tube:  SIZE = 4 + (Age / 4)
     • For CUFFED endotracheal tube: SIZE = 3.5 + (Age / 4)
     --After age 8 (CUFFED) = Age/4 + 3.
   
   ♦ Alternatively, use of Broselow tape (a color-coded length-based tape measure) or
   ♦ the child's pinky finger diameter are crude approximations for ETT size in a pinch. 
   
   ♦ According to the NIH, another formula is used:  
   • (age + 16)/4 because it is more accurate the older the child gets when compared with the 4 + (Age/4).
3. While oxygenating the patient, ensure the tube cuff inflates and deflates completely.
4. Following pre-oxygenation, open the airway with a chin tilt and insert the laryngoscope blade into to R part of the mouth with the left hand, sliding over the tongue to the laryngopharynx.
   
   Hyperextend the patient's head. Many persons get confused about flexion and extension of the head since the neck musculature is not similar to flexion/extension joints of the extremities. We're talking head, not neck, because the confusion is all the worse since extension of the head (tilting back) accompanies flexion of the neck and vice versa: 
   
   Extension/hyperextension is the tilting of the head BACK. This puts the trachea more in a direct line approach from the pharynx, although a neutral position is used for nasotracheal intubation.
   Flexion/hyperflexion is chin-to-chest position, which simply cannot work for intubation. 
    
5. Up-and-left pressure (without putting pressure on the teeth!) should offset the mandible and allow for placement of the tip of the laryngoscope blade in the vallecula and thus reveal the glottic opening for visualization of the vocal cords. Apply this pressure by manipulating the blade with your shoulder/upper arm, keep the wrist stiff!
6. Suction as needed to visualize the tube.
7. Once the cords are visualized, take the lubricated ET tube (preferably with the stylet in place) in the R hand and carefully introduce the tube between the vocal cords, stopping when the cords rest between the two black horizontal marks on the tube.
8. Withdraw the laryngoscope blade while holding the tube in place, and remove the stylet.
9. Inflate the pilot balloon with the manufacturer-suggested amount of air.
10. Confirm tube placement, secure the tube, and monitor its position while en route.

Cricoid pressure ("Sellick Maneuver"): Hold the cricoid cartilage between your thumb and middle finger and use your index finger to push the cricoid cartilage backward against the spine. The cricoid pressure collapses the esophagus between the cricoid cartilage and the spine to prevent regurgitation of gastric contents and not to actually prevent vomiting. 

 

Confirming Proper Placement

Even when the tube is visualized passing the cords, confirmation of effective ventilation is vital. The key modalities to confirm placement are a combination of:

• chest rise,
• breath sounds, and
• end-tidal CO2 via capnography. 

Esophageal Detector Device: Another way to confirm placement (81-100% accuracy, according to the NIH), is using an esophageal detector device (EDD) when capnography (the accepted standard for confirmation) is not available. If you have intubated the patient correctly, the EDD will expand quickly after you squeeze it. That means it's filling with air it got from the airway, meaning you're connected to the lungs. 

After securing the tube connect a capnograph, place a stethoscope over the gastric area, and provide a single breath via bag-valve-mask. This first step lets you know if the breath is going down the esophagus as opposed to the trachea, this is known as "esophageal intubation." Then, move to auscultate the left lung and if sounds are heard there auscultate the right, ensuring breath sounds are even through the lungs.

Throughout all the above steps, look for equal chest rise and end-tidal CO2 measurements of 35% to 45%. 

ESOPHAGEAL INTUBATION: If breath sounds are heard in the abdomen, esophageal intubation has occurred and the patient should be extubated (withdraw air from the pilot balloon and remove the tube). Auscultation over the stomach should produce no breath sounds.

UNEQUAL BREATH SOUNDS: If no breath sounds are auscultated in the L lung but are present in the R lung, deflate the pilot balloon to about half-full and withdraw the tube a few centimeters. (It has been passed too far, bypassing the left mainstem bronchus.) Re-inflate the pilot balloon to the correct pressure and reassess until equal sounds are auscultated in the L and R lung.

CAVEATS:

• Be aware that a pneumothorax could prevent bilateral breath sounds even after correct placement. Make a note of where the tube is marked at the teeth and reassess often.
• Esophageal Detection Device (EDD) and auscultation of lung sounds may be unreliable in the smaller chests of children and neonates due to disparate anatomy compared with adults.
• End-tidal capnography by any method can be unreliable if there is insufficient perfusion, such as with MI or shock. 
• Inflate the pilot balloon with the manufacturer-suggested amount of air; overfilling can compress the superficial cell layers causing ischemia and necrosis.

 

Post-intubation reassessment and management 

Immediately following intubation carefully monitor every vital sign as countless complications are possible; heart rate, blood pressure, SPO2, ETCO2, and respiratory rate are all critical. 

Following the immediate post-intubation period, use the mnemonic DOPE for factors that could affect your now intubated patient while they are in transit.

• D – Displacement/Dislodged tube.
• O – Obstruction or clamped tube.
• P – Placement in the R mainstem bronchus or esophagus.
• E –Equipment: the tube or other equipment may have malfunctioned requiring replacement.

 

Extubation

Extubation always risks airway compromise and aspiration if the patient cannot protect his own airway. If a patient is suddenly aware and struggles with the ETT, It is usually better to sedate this patient en route to the hospital rather than extubate in a prehospital environment.