1. Indications for tracheal intubation
Tracheal intubation is indicated for any condition that does require airway management. Tracheal intubation is often required when patients are under general anesthesia to facilitate airway management; it is also part of the monitoring of critically ill patients with multisystem disease or impairment. Emergency indications include cardiac or respiratory arrest, airway failure to prevent inadvertent aspiration, hypoxia or hypoventilation, and airway obstruction.
2. Contraindications
Airway management is extremely important in emergencies or acute cases, such as when a patient is in cardiac arrest, but there are still very few contraindications to tracheal intubation. Direct laryngoscopic tracheal intubation is relatively contraindicated in patients who have undergone partial tracheal transection because the tracheal intubation step leads to total tracheal transection and airway injury. In these patients, surgical airway management may be necessary, and unstable cervical spine injury is not a contraindication, but the cervical spine must be maintained in strict, linear fixation during intubation. The assistant should stand on the side of the bed to support the patient’s head and neck, keeping the patient’s shoulders in a natural position. Keep the patient’s mouth fully open by opening or removing the patient’s neck collar. When emergency intubation is not required, the difficulty of intubation should be evaluated first, as discussed in detail in the following sections on preoperative preparation, sedation and anesthesia.
3. Equipment required for intubation
The following equipment should be prepared before intubation: gloves, mask, suction device (to check for correctness before intubation), ball valve mask (with oxygen source connected), 10 ml syringe, endotracheal tube clamp (if not available, use cloth tape instead), end-tidal carbon dioxide detector, tracheal tube and core, and laryngoscope with a suitable scope body.
There are two main types of laryngoscope bodies used: Machintosh’s (curved type) and Miller’s (straight type). There are different models of each type of body, and the technique used varies slightly from body to body. The choice of scope is based on the operator’s experience and personal preference. size 3 or 4 Macintosh’s and size 2 or 3 Miller’s are suitable for most adult patients.
The type of endotracheal tube depends on the internal diameter of the trachea. 7.0, 7.5, or 8.0 mm endotracheal tubes are suitable for most adults, and can be extrapolated for pediatric patients as follows: [age + 4] ÷ 4 = type of tube, width of the pediatric pinkie at the end of the finger = outside diameter of the tube, based on the pediatric height or length calculation (e.g., Broslow CLuten resuscitation tape). The cannula can be either cannulated or uncannulated. Cannulae with a capsule are suitable for adults or older children. Non-capsulated cannulae are used in younger patients (requiring a cannula diameter of less than 5.5 mm). After the insertion of the cannula with a capsule, gas should be injected to expand the capsule and close the lumen between the trachea and the cannula, which can avoid air leakage and aspiration of gastric contents.
4.Preparation before intubation
Before tracheal intubation, first of all, the necessary equipment should be prepared and ensure that they can be used normally, personnel in place, if the situation allows, the patient or his family must sign the informed consent.
Inject gas to inflate the capsule to check for air leaks. Insert the catheter core into the tracheal tube, maintaining the normal curvature of the catheter. Do not expose the end of the core to the catheter. If necessary, the core is also “field hockey puck”-like to reshape the tracheal tube so that it can easily enter the epiglottis. An aspirator should also be available for backup. Open intravenous access and, if time and condition permit, preferably connect a monitor. While intubating, have the assistant observe the monitor and report changes in condition. Adjust the height of the bed to the level of the operator’s lower sternal border. When there is no contraindication, place a pillow or folded towel on the patient’s occipital area so that he or she is in the inspiratory position. The neck is flexed and the head is hyperextended so that the mouth, pharynx, and larynx are in a straight line, allowing full exposure of the vocal cords. When the patient is an infant, the above method is usually not necessary because the infant’s occipital area is large and can be placed in the inspiratory position with the occipital area as a support point. If the patient’s condition permits, the patient can be placed on 100% oxygen for at least 3 minutes with a non-retractable mask or a bulb mask prior to intubation. This replaces the alveoli previously occupied by nitrogen with oxygen. This step also significantly reduces the duration of positive pressure ventilation during intubation, which further reduces the risk of inadvertent aspiration of gastric contents. Prior to insertion of the laryngoscope, all dentures, if worn, should be removed. If a ball-and-flap mask is used for ventilation, the dentures should be reapplied to maintain the mask seal. If the patient is comatose or sedated, the assistant should apply forceful compression to the cricoid cartilage. This method (Sellick method) allows compression of the esophagus between the cricoid cartilage and the cervical spine to avoid reflux of gastric contents. If the airway is twisted, the pressure should be reduced to fully expose the acoustic canal.
5. Sedation and anesthesia
In many cases, the use of neuromuscular blocking agents and effective sedation is required. These medications improve the visibility of the vocal cords, prevent the patient from vomiting and aspirating gastric contents, and make intubation more convenient. If you plan to use such medications, the difficulty of intubation must be evaluated prior to the procedure. You will usually be able to predict that intubation will be difficult in the following situations: if the patient has a previous history of difficult intubation, limited neck mobility, small jaw, poor visibility of pharyngeal structures by pulling the tongue through the opening, limited oral opening, and proximity of the laryngeal node to the chin. In addition, anatomic deformities (e.g., due to tumor, trauma, or infection), edema, and airway obstruction may also increase the difficulty of tracheal intubation. Therefore, if you are faced with a potentially difficult intubation, you should have a plan to deal with the eventuality, including alternative techniques to prepare for intubation, such as the use of flexible resin probes, mask ventilation, fiberoptic bronchoscopy, or surgical approaches.
6. Operation steps
The operator adjusts the body position with both eyes at a sufficient distance from the patient to allow direct binocular vision. Hold the laryngoscope in the left hand and open the patient’s mouth with the right hand. Insert the laryngoscope body into the right side of the patient’s tongue. Gradually move the scope to the center of the mouth, pressing the tongue to the left side. Slowly insert the scope body to position it to the epiglottis. The ideal placement of the scope depends on whether a curved or straight model is used. If a curved type is used, place it in the epiglottis valley, between the heel of the tongue and the epiglottis. If a straight type is used, place it behind the epiglottis. After correct placement of the lens, the laryngoscope is lifted forward at an angle of 45 degrees so that the vocal cords can be seen. Advance the laryngoscope along the hand axis toward the side of the patient’s foot. The wrist should not be bent and the lens should be shaken to prevent the patient’s teeth from clenching, which is the time to avoid tooth and soft tissue damage (do not put the vocal cords in view). Hold the tracheal cannula in the right hand, maintain the vocal fold view, and insert the tracheal cannula to the right side of the patient’s mouth. The tube should not be obstructed by the vocal fold view, which is a critical part of the procedure. The cannula is passed through the vocal cords into the trachea until the balloon disappears. The needle core is withdrawn and the balloon is fed 3 to 4 cm past the vocal cords. air is used to inflate the balloon to the minimum pressure required to prevent air leakage, at which point the tidal volume is used to replace the air with this balloon. Generally less than 10 ml of air is required. Before you confirm the intubation has been in the trachea to have an assistant to maintain the pressure of the tracheal cartilage ring.
7.Failure judgment and troubleshooting
If you cannot observe the vocal cord or epiglottis after adjusting the laryngoscope body position, it may be due to too deep insertion of the scope or failure to place it precisely in the median line. Slowly withdrawing the scope in the midline often allows the vocal folds or epiglottis to jump into view; use your right hand to handle the glottis or have an assistant apply a steady backward, upward, and rightward pressure to the glottis (this is called the BURP maneuver), which also makes it easier to view the vocal folds; an assistant can gently pull the right edge of the patient’s lip and cheek to increase the visibility of the vocal folds. If you still cannot see the vocal folds clearly, the assistant should gently relieve the pressure on the cricoid cartilage, as this pressure can sometimes interfere with observation. In summary, you should always make the vocal cords as adjustable as possible for the best viewing field before attempting tracheal intubation.
8. Post-intubation verification
The end of the tracheal tube should be located in the middle of the trachea, 3-7 cm above the bulge. generally, for medium-sized adults, align the 22 cm scale of the tracheal tube with the anterior teeth. In children, the following formula can be used to estimate the required depth of insertion: catheter depth = [age + 2] ÷ 12. Connect the endotracheal tube with the endotracheal carbon dioxide detector and attach the respiratory bag to give a small tidal volume of breath. The presence of the endotracheal tube cannot be determined solely on the basis of physical examination or vaporization of the tube; other techniques must be used to determine this important aspect of tracheal intubation management. After tracheal intubation, it is plausible that exhaled carbon dioxide can be monitored continuously for the first six breaths. In some patients in cardiac arrest, there is no gas exchange, and therefore, carbon dioxide cannot be demonstrated even if the catheter is in the trachea. In these cases, the tracheal cartilage rings can be viewed directly with an esophageal detection device or fiberoptic endoscopy.
Second, to determine if the esophagus is inserted, the abdomen can be auscultated during positive pressure ventilation. Auscultate both lungs in the mid-axillary line on both sides for symmetry of respiratory motion. If the left lung has decreased breath sounds after intubation, then the right main bronchus may be inserted and the tracheal tube is slowly withdrawn until the breath sounds are symmetrical on both sides on auscultation (i.e., symmetry between the right and left lungs). After tracheal intubation, examine the patient’s lungs with chest fluoroscopy and confirm that the tip of the labeled line on the tracheal tube that is not X-rayed is in the mid-trachea and not in the left or right main bronchus. However, for identifying whether the esophagus is inserted, X-ray fluoroscopy is not reliable.
9. Catheter fixation
Once it can be confirmed that the tracheal tube is in the proper position, the catheter is then fixed to the patient’s head. An endotracheal tube fixator should be used to hold the catheter in place, as this fixator can help prevent sudden displacement of the catheter. If the fixator is not completely effective, a tape or cloth endotracheal tube fixation band can be used. The use of sedatives and hand immobilization can also be used to prevent the patient from inadvertently pulling out the intubation tube.
10. Complications
The most serious complication of tracheal intubation is accidental insertion into the esophagus, which can lead to aspiration of gastric contents, hypercapnia, and death. Laryngoscopy can stimulate vomiting and aspiration of gastric contents, causing aspiration pneumonia. Other complications include bradycardia, laryngospasm, bronchospasm, and apnea due to pharyngeal irritation. Loss of teeth, lips, vocal cords and aggravation of cervical spine injuries can also occur.