Manikin - Anatomy of the Trachea

Manikin - Anatomy of the Trachea

Because the way of tracheal intubation model is mainly through the portal cavity or nasal cavity, the catheter is sent to the trachea or common bronchus through the throat and glottis fissure. Therefore, familiarity with the anatomy of the airway is essential. The nasal cavity refers to the passage from the anterior nostril to the posterior nostril, which forms an arc from front to back and forms a sharper angle with the upper and lower direction of the nasopharyngeal cavity. There are abundant blood vessels in the nasal mucosa. When the catheter enters the nasal cavity, it should be pushed forward slowly from front to back. Do not use too much force to prevent mucosal damage and bleeding. When the patient's nasal mucosa has inflammation or nasal polyps, it should be more cautious, and oral intubation can be used instead. When nasal intubation is used, a catheter with a thin wall, soft and flexible tube should be selected, which is generally slightly thinner than the catheter for oral intubation, otherwise it will not be easy to pass through the posterior nostril. Some people think that as long as there is no contraindication, a few drops of vasoconstrictor can be instilled, generally 1% ****** solution, and occasionally 0.1% epinephrine solution can be used to constrict the blood vessels of the nasal mucosa, so that the inner diameter of the nasal cavity is corresponding. Intubation can only be done after enlargement. If the nasal vestibule is composed of cartilage, the nasal cavity is almost entirely bone. When the tracheal tube is inserted through the nasal cavity, the nasal vestibule can often be expanded to accommodate a catheter with a diameter of 10 mm, and the glottic cleft can be inserted through the anterior nasal opening and the posterior nasal opening of the common nasal passage. The distance from the anterior nostril to the posterior nostril is equivalent to the length of the alar to the earlobe, about 12-14cm for adults. When intubating the mouth, it can be directly inserted into the glottis through the throat through the mouth. Because the mucosa of the posterior pharyngeal wall is very fragile, it is vulnerable to damage when the laryngoscope is improperly placed. It will cover the laryngeal surface (pointing to the side of the glottis fissure) because the vagus nerve is distributed more, such as when the anesthesia is too shallow or the surface anesthesia is insufficient, it is easy to cause the laryngeal reflex when it encounters stimulation, so that the larynx is lifted up, which will cover the larynx, and the glottis will be closed at the same time. Even laryngospasm, which makes the emergency resuscitation simulator difficult to intubate.

The larynx is located in front of the 5th cervical thrust, and its range of motion up and down is equivalent to a cervical vertebra. It is composed of cartilage, ligaments, mucous membranes and muscles. The cartilage is mainly composed of thyroid cartilage and cricoid cartilage, supplemented by structured epiglottis, cuneiform cartilage and small horn cartilage. The front protrusion is called the Adam's apple and is more pronounced in adult males than in females. It helps to determine the upper edge of the thyroid cartilage, which is the positioning of the body surface landmark. There is an interring membrane between the thyroid cartilage and the cricoid cartilage. There are two vocal cords and false vocal cords (ventricular folds) between the annular cavities in the shape of the thyroid cartilage, on the left and right sides, which form the glottis.

The entrance of the larynx of the nurse model is narrow in the front and wide in the back, and it is not on the same plane. The glottis is the most narrow and straight part of the larynx. It shrinks during shallow general anesthesia and widens during deep general anesthesia. When the general anesthesia is too shallow, the catheter used is too thick, and the intubation can easily scratch the vocal cords.

The cricoid cartilage is hereinafter referred to as the trachea. It is composed of 16-20 horseshoe-shaped rings of cartilage, connected by connective tissue. The anterior cartilage ring is tough and the posterior wall muscle is weak and vulnerable, with a total length of 10-14 cm. The upper boundary is the level of the 6th cervical push, and the lower boundary is equivalent to the level of the 5th thoracic vertebra, which is divided into left and right main bronchi. The bifurcation of the trachea is called the carina. Because of the abundant distribution of the vagus nerve in the inner face of the carina, it is extremely sensitive and is only suppressed under deep anesthesia. The right main bronchus intersects with the longitudinal axis of the trachea at an angle of 250, so the angle is smaller than that of the left main bronchus, and the diameter of the tube is also thicker than that of the left bronchus, so it is easy to insert the tracheal tube. And because the left main bronchus is shorter than the left one, only 1.5-2.0 cm in adults, once the catheter is mistakenly inserted into the right bronchus, it is very easy to block the opening of the right upper lobe bronchus.

The path from the oral cavity or the nasal cavity to the trachea is not a straight line. If an axis is made through the oral cavity, and an axis is made through the larynx and the pharynx, when lying down, these two axes intersect with each other to form an angle; when looking up, The two axes of transpharyngeal and translarynx can be overlapped in a straight line, which is conducive to nasal intubation; if the patient's head is raised, and the patient's head is tilted back as much as possible, the axes of the cage can be completely overlapped, which is convenient for the formation of transoral clear vision intubation. The relationship between the changes in the position of the two axes of the respiratory tract and the position of the head. The inner diameter and length of the trachea and bronchi are also different in different ages.

Regarding children, it is more difficult due to the different characteristics of intubation. For example, due to the characteristics of the upper respiratory tract of newborns, the tongue is large and thick, and the tongue base is backward inclined to form an angle of 39.5 degrees with the epiglottis. In addition, the thyroid cartilage is inclined forward by 60 degrees, which will cause the larynx to form a 130-degree sink angle. The size of this plunge angle has a great impact on endotracheal intubation. The smaller the angle, the more difficult it is to see the larynx intubation, and the larger the angle, the easier it is to insert. This angle is smaller in neonates than in infants, so it is more difficult to observe the throat and intubate for neonates. If the thyroid cartilage is pushed from the front to the back of the neck, the larynx is moved back to reduce the anteversion angle of the thyroid cartilage, which will help to stretch and increase the angle of penetration of the larynx, thus making it easier to observe the larynx and intubate. In short, to correctly grasp the depth of the intubation.