**3. Evaluation of the complex airway**

#### **3.1. Pediatric airway differences**

The pediatric airway changes significantly from birth to adulthood. These changes affect the development of the skull, oral cavity, throat, and trachea. The head is larger than the body in infants and young children. Due to the absence of paranasal sinuses, the facial skeleton is smaller in neonates compared with neurocranium. Oral cavity is small at birth. It grows in the first year of life due to the significant growth of the mandibles and teeth in the following period. In neonates, the tongue has a flat surface and limited lateral mobility and appears relatively large in the small mouth space. Neonatal laryngeal and tracheal structures are especially important for anesthesiologist. The larynx appears more prominently during direct laryngoscopy, but when compared with adults, the surrounding structure is loosely embedded. External manipulation allows direct laryngoscopic intubation to be easily carried to a position where it is possible. If the epiglottis is not removed by the bladder of the laryngoscope, the glottic appearance on the laryngoscopy is prevented long, narrow, and often U- or V-shaped ("flopping") [16]. Glottis is higher in the newborn (C2/C3) than in the vertebrae, and after 2 years, it falls to the normal position in C5 [17]. In newborn, vocal cords are shorter, and anterior glottis, which normally corresponds to two-thirds in a larger child, constitutes about 50% of the newborn. The newborn larynx is conical, but in a larger child, it is approximately cylindrical. Though the larynx is thought to be widest in the supraglottic region and narrowest in the subglottic region, this suggests that the narrowest portion of the magnetic resonance imaging (MRI) studies may be in glottic. Also, the cricoid ring is the narrowest part of the neonatal airway and is an ellipsoid-shaped mucosa layer which is highly sensitive to trauma. Bypassing the air leak at this level from the untrained tracheal tube does not guarantee avoidance from the pressure points and the next payment [18]. Intubation tubes with small tracheal internal diameter cause a significant increase in airway resistance and this can lead to an exaggerated mucosal injury. The tracheal length depends on the child's age and height but is not dependent on body weight. During the operation, changes in the head position may lead to a displacement of the tracheal tube and reevaluate the position of the tube with the head's new position. Verification of the position of the tracheal tube clinically (chest movement, auscultation) or by other means (chest radiography, fluoroscopy, ultrasonography, or bronchoscopy) is recommended.

see the larynx. Macroglossia occurs in Beckwith-Wiedemann syndrome, Down syndrome,

Functional Anatomy and Physiology of Airway http://dx.doi.org/10.5772/intechopen.77037 19

Perioperative management in obese patient, including airway management, is an increasing and a worldwide concern for the anesthesiologist. Since obese patients have an increased fatty tissue distributed in a truncal fashion, obesity may have an important and negative impact on the airway patency and respiratory function. Respiratory function and airway patency can be significantly altered by this change in position [23]. Airway assessment of the obese patient should be performed with the patient in both the sitting and supine positions. Respiratory function and airway patency can be significantly altered by this change in position [24]. Body weight may not be as critical as the location of excess weight. Massive weight in the lower abdomen and hip area may be less important than when the weight is in the upper body area. A short, thick, immobile neck caused by cervical spine fat pads will interfere with rigid laryngoscopy. Furthermore, the redundancy of soft tissue structures inside the oropharyngeal and supralaryngeal area may also make visualization of the laryngeal structures difficult. Mask ventilation should be difficult in the obese patient. When a high positive pressure is required to ventilate the patient, the chance of inflating the stomach is increased. Rapidly oxygen desaturation during apnea, secondary to a reduced functional residual capacity, limits intubation time. In the case of a cannot-intubate-cannot-ventilate situation, access to the neck for transtracheal jet ventilation or establishing a surgical airway (emergency tracheostomy or

Maternal, fetal, surgical, and personal factors in pregnancy cause an increase in the incidence of unsuccessful intubation. The mucosa of the upper respiratory tract becomes more vascular and edematous, which increases the risk of bleeding and swelling in the airway [25]. These changes cause the Mallampati score to increase as the pregnancy progresses and during labor. Airway edema may be exacerbated by preeclampsia, oxytocin infusion, intravenous fluids, and Valsalva maneuvers during labor and delivery. A decreased functional residual capacity and increased oxygen requirements accelerate the onset of desaturation during apnea and are further exacerbated in obese patients. Progesterone reduces the lower esophageal sphincter tonus, which results in gastric reflux. Risk of reflux is further increased because of delayed gastric emptying after prolonged painful delivery and opioid administration. Enlarged breasts can make laryngoscopy difficult [26]. Airway anatomy may become distorted during prolonged labor or toxemia, leading to an edematous soft tissue encroachment of the upper airway [27]. At last, in cases of fetal distress or maternal hemorrhage, the emergency nature of

All illustrations were designed and colored by architect Ceren Yoldaş. www.yoldasmimarlik.com 00 90 5425346896, Doğan Demircioğlu Cad. Özlem Sitesi C Blok Denizli Turkey.

Sturge-Weber syndrome, and in a variety of dystrophically related syndromes [22].

**3.3. Obese patients**

**3.4. Pregnancy**

**Acknowledgements**

cricothyroidotomy) will also be more complex [9].

the circumstances compounds airway management problems [9].

**Physiological conditions:** in human, the downward movement of the laryngeal structures according to age is the main factor in transaction from nasal breathing to oral breathing. Direct result is the dissociation of the epiglottis and the soft palate. The pediatric airway cannot be assessed in young children without considering very low functional residual capacity. This situation, a high oxygen demand, an increased carbon dioxide production, and an increased closure capacity, is together. And the situation which is in very low tolerance to apnea appears with this result. This rapidly leads to significant hypoxemia and respiratory acidosis. Even the optimal time preoxygenation cannot result in a "safety time" that is long enough to prevent desaturation following short periods of apnea. The smaller the child, the more limited the time is [19, 20]. In human, one of the most strongest reflexes is laryngeal reflexes and it can be thought to prevent pulmonary aspiration. These functional reflexes are undernapped by the inner and outer branches of the larynx, recurrent laryngeal nerve, and superior laryngeal nerves. The afferent innervation of the subglottic part of the larynx and all muscles is also provided by the recurrent laryngeal nerve, except for the cricothyroid scar. The larynx is relatively insensitive to irritant gases that are inhaled but is very sensitive to mechanical or chemical stimuli caused by fluid or solutes.

#### **3.2. Congenital disease**

It may produce abnormalities of the head, neck, or upper airway [9]. Cardiovascular, nervous, musculocutaneous, or excretory system disease is more often tabulated with these abnormalities. Crouzon, Goldenhar, Pierre Robin, and Treacher Collins syndromes are known for their abnormal head and neck. The patients with micrognatia, retrognatia, and macroglossia must be remembered for the congenital diseases in childhood [9]. The most significant vascular malformations are vascular rings, usually of aortic arch origin, encircling the trachea. Tracheomalacia, congenital tracheal stenosis, shortened trachea, and bronchogenic cysts can contribute to difficult airway management [21]. Infants with congenital malformation syndromes associated with cardiovascular anomalies and skeletal dysplasia have a shortened trachea significant percentage [21]. Soft tissue changes that cause airway management difficulties are usually divided into two categories as those that disturb the motion of the airway and limit the movements that disturb the airway by mass effects. Soft tissue changes that limit airway motion usually affect mouth opening. Microstomy, a feature of Freeman-Sheldon syndrome, is a condition in which the movement of oral tissues that do not respond to stomach relaxation is limited. Other rare diseases that limit the movement of airway tissue include fibrofacial myositis ossificans and dermatomyositis. The mass effects on the airway due to soft tissue abnormalities may be the result of congenital, end-of-life, or subsequent disease outcomes of surgical interventions [22]. Macroglossia is one of the most common problems appearing with birth, and the tongue expands and fills the oral cavity, making it difficult to see the larynx. Macroglossia occurs in Beckwith-Wiedemann syndrome, Down syndrome, Sturge-Weber syndrome, and in a variety of dystrophically related syndromes [22].

#### **3.3. Obese patients**

tube does not guarantee avoidance from the pressure points and the next payment [18]. Intubation tubes with small tracheal internal diameter cause a significant increase in airway resistance and this can lead to an exaggerated mucosal injury. The tracheal length depends on the child's age and height but is not dependent on body weight. During the operation, changes in the head position may lead to a displacement of the tracheal tube and reevaluate the position of the tube with the head's new position. Verification of the position of the tracheal tube clinically (chest movement, auscultation) or by other means (chest radiography,

**Physiological conditions:** in human, the downward movement of the laryngeal structures according to age is the main factor in transaction from nasal breathing to oral breathing. Direct result is the dissociation of the epiglottis and the soft palate. The pediatric airway cannot be assessed in young children without considering very low functional residual capacity. This situation, a high oxygen demand, an increased carbon dioxide production, and an increased closure capacity, is together. And the situation which is in very low tolerance to apnea appears with this result. This rapidly leads to significant hypoxemia and respiratory acidosis. Even the optimal time preoxygenation cannot result in a "safety time" that is long enough to prevent desaturation following short periods of apnea. The smaller the child, the more limited the time is [19, 20]. In human, one of the most strongest reflexes is laryngeal reflexes and it can be thought to prevent pulmonary aspiration. These functional reflexes are undernapped by the inner and outer branches of the larynx, recurrent laryngeal nerve, and superior laryngeal nerves. The afferent innervation of the subglottic part of the larynx and all muscles is also provided by the recurrent laryngeal nerve, except for the cricothyroid scar. The larynx is relatively insensitive to irritant gases that are inhaled but is very sensitive to

It may produce abnormalities of the head, neck, or upper airway [9]. Cardiovascular, nervous, musculocutaneous, or excretory system disease is more often tabulated with these abnormalities. Crouzon, Goldenhar, Pierre Robin, and Treacher Collins syndromes are known for their abnormal head and neck. The patients with micrognatia, retrognatia, and macroglossia must be remembered for the congenital diseases in childhood [9]. The most significant vascular malformations are vascular rings, usually of aortic arch origin, encircling the trachea. Tracheomalacia, congenital tracheal stenosis, shortened trachea, and bronchogenic cysts can contribute to difficult airway management [21]. Infants with congenital malformation syndromes associated with cardiovascular anomalies and skeletal dysplasia have a shortened trachea significant percentage [21]. Soft tissue changes that cause airway management difficulties are usually divided into two categories as those that disturb the motion of the airway and limit the movements that disturb the airway by mass effects. Soft tissue changes that limit airway motion usually affect mouth opening. Microstomy, a feature of Freeman-Sheldon syndrome, is a condition in which the movement of oral tissues that do not respond to stomach relaxation is limited. Other rare diseases that limit the movement of airway tissue include fibrofacial myositis ossificans and dermatomyositis. The mass effects on the airway due to soft tissue abnormalities may be the result of congenital, end-of-life, or subsequent disease outcomes of surgical interventions [22]. Macroglossia is one of the most common problems appearing with birth, and the tongue expands and fills the oral cavity, making it difficult to

fluoroscopy, ultrasonography, or bronchoscopy) is recommended.

mechanical or chemical stimuli caused by fluid or solutes.

**3.2. Congenital disease**

18 Tracheal Intubation

Perioperative management in obese patient, including airway management, is an increasing and a worldwide concern for the anesthesiologist. Since obese patients have an increased fatty tissue distributed in a truncal fashion, obesity may have an important and negative impact on the airway patency and respiratory function. Respiratory function and airway patency can be significantly altered by this change in position [23]. Airway assessment of the obese patient should be performed with the patient in both the sitting and supine positions. Respiratory function and airway patency can be significantly altered by this change in position [24]. Body weight may not be as critical as the location of excess weight. Massive weight in the lower abdomen and hip area may be less important than when the weight is in the upper body area. A short, thick, immobile neck caused by cervical spine fat pads will interfere with rigid laryngoscopy. Furthermore, the redundancy of soft tissue structures inside the oropharyngeal and supralaryngeal area may also make visualization of the laryngeal structures difficult. Mask ventilation should be difficult in the obese patient. When a high positive pressure is required to ventilate the patient, the chance of inflating the stomach is increased. Rapidly oxygen desaturation during apnea, secondary to a reduced functional residual capacity, limits intubation time. In the case of a cannot-intubate-cannot-ventilate situation, access to the neck for transtracheal jet ventilation or establishing a surgical airway (emergency tracheostomy or cricothyroidotomy) will also be more complex [9].

#### **3.4. Pregnancy**

Maternal, fetal, surgical, and personal factors in pregnancy cause an increase in the incidence of unsuccessful intubation. The mucosa of the upper respiratory tract becomes more vascular and edematous, which increases the risk of bleeding and swelling in the airway [25]. These changes cause the Mallampati score to increase as the pregnancy progresses and during labor. Airway edema may be exacerbated by preeclampsia, oxytocin infusion, intravenous fluids, and Valsalva maneuvers during labor and delivery. A decreased functional residual capacity and increased oxygen requirements accelerate the onset of desaturation during apnea and are further exacerbated in obese patients. Progesterone reduces the lower esophageal sphincter tonus, which results in gastric reflux. Risk of reflux is further increased because of delayed gastric emptying after prolonged painful delivery and opioid administration. Enlarged breasts can make laryngoscopy difficult [26]. Airway anatomy may become distorted during prolonged labor or toxemia, leading to an edematous soft tissue encroachment of the upper airway [27]. At last, in cases of fetal distress or maternal hemorrhage, the emergency nature of the circumstances compounds airway management problems [9].
