**5. Preoperative preparation**

Approximately 10–15% of pregnant women undergo emergency cesarean section [2]. Regional anesthesia is preferred worldwide most commonly, and general anesthesia is applied with rapid sequence induction (RSI) for the rest of the patients. Some tests and examinations are required to evaluate the airway before anesthesia applications. The ideal test should be simple, fast, and cost-effective in the preoperative evaluation. Most bedside testa are affected with anatomical and physiological changes of pregnancy [3]. It should also have high sensitivity, high specificity, and positive predictive value. According to the American Society of Anesthesiologists (ASA) difficult intubation guidelines, the difficult airway definition can be described as an experienced anesthesiologist experiencing difficulties in ventilation, tracheal intubation, or both [4]. Difficult laryngoscopy is defined as an experienced anesthesiologist's inability to perform intubation in more than three attempts with a conventional laryngoscope. Difficult mask ventilation is defined as the anesthesiologist's inability to maintain oxygenation without assistance, the inability to increase the peripheral oxygen saturation above 90% despite using 100% oxygen, or the inability to correct improper ventilation findings. Gas leakage from the face mask, decreased chest movements and auscultation findings, dilatation of the stomach with air, hypoxemia, cyanosis, or hypercarbia indicate improper ventilation. One of the most commonly used preoperative evaluation tests is the Modified Mallampati score. Mallampati score of 3 and 4, BMI of >26 kg. m2 , mandibular protrusion defect, snoring history, abnormal facial anatomy, and high thyromental distance are among the markers of difficult mask ventilation in pregnant women. Obstructive sleep apnea is another marker of difficult mask ventilation. In the preoperative period, difficult laryngeal mask placement can also be evaluated. Components of the shortening of RODS are listed in **Table 2**.

Protruding maxillary incisors, receding mandible, short interincisor distance, and increased neck circumference are among other difficult airway markers in pregnant women. Other potential risk factors include obesity, short neck, receding


#### **Table 2.** *Difficult laryngeal mask ventilation markers: RODS.*


#### **Table 3.**

*Preoperative examination findings for direct laryngoscopy and intubation difficulty.*

mandible, swollen tongue, and facial edema. The distances that should be measured in the preoperative examination and examination findings that are predictive for direct laryngoscopy and intubation difficulty are given in **Table 3**. In pregnant patients the physiological and the anatomical changes constitute the difficulty for airway management. The susceptibility to hypoxaemia, friability and mucosal engorgement are main causes of failed airway management [2].

#### **6. Preoxygenation and apneic oxygenation in obstetric patients**

As obstetric patients are prone to have airway management difficulties, preoxygenation is essential to increase the oxygen reserve before anesthesia induction. The ideal way to determine the sufficiency of preoxygenation is to monitor end tidal oxygen (FeO2) concentration. FeO2 < 90% shows inadequate preoxygenation. We have a critical level the oxygen consumption about 250 mL/min. This rate increases during pregnancy. As oxygen is removed from lungs the alveolar partial oxygen pressure decreases during airway interventions. Therefore apneic oxygenation is recommended. Oxygen delivery systems include nasal canula, simple face mask, Ventury mask, non-rebreather mask, insufflation by transtracheal or endobronchial catheters, dual bladed laryngoscopes. High flow nasal cannula is also commonly used for this purpose today. During apneic oxygenation, carbon dioxide levels continue to rise, which can lead to a decrease in pH and respiratory acidosis. However, the use of higher flow more than 15 L/min oxygen during apnea provides better gas washout.

#### **7. Awake intubation**

When it is thought that oxygenation and manual ventilation cannot be guaranteed after anesthesia induction in a pregnant woman with difficult intubation, awake intubation is recommended. Expecting a high rate of leakage between the face mask and the face, upper airway collapse as a result of general anesthesia are among the conditions that require awake intubation. Awake intubation can be performed using a video-laryngoscope or flexible bronchoscope [5, 6]. During the procedure, low or, if possible, high flow oxygen applications are recommended to extend the apneic window. If the patient will be intubated under general anesthesia or if it is understood that there is a difficult airway following induction,

**185**

*Airway Management during Pregnancy and Labor DOI: http://dx.doi.org/10.5772/intechopen.96476*

women with hemodynamic instability.

and failure due to inexperienced operator.

cricothyroid membrane identification [11].

**9. Difficult airway guide in obstetrics**

**8. Surgical cricothyroidotomy**

the use of a video-laryngoscope is often recommended [7]. Different types of video-laryngoscopes have been presented in studies and case reports. Kariya et al. [8] reported that awake tracheal intubation with Airway Scope is safe in pregnant

Topicalization can be performed in different ways. N. Glossopharyngeus nerve block can be performed in palatoglossal arc. It provides the blockade of gag reflex. N. Laryngealis recurrens and superior can be blocked in cervical level. Another technique is to apply local anesthetic infiltration at the oropharyngeal area. Mucosal atomization devices, inhalational lidocaine or lidocaine lolipops are aother alternatives. EMLA contains 2.5% lidocaine and 2.5% prilocaine and is another option for topicalization. The disadvantages include uncooperated patients, oversedation risk

The frequency of obesity is increasing in pregnant women. Although regional anesthesia is recommended, surgical intervention may be required under general anesthesia. It is important to identify neck landmarks while performing surgical cricothyroidotomy. Cricothyroidotomy complications vary from 6.1% to 54.5% [9, 10]. Ultrasonography can provide advantages over traditional digital palpation in obese pregnant women by improving the image and increasing the accuracy of

The incidence of failed tracheal intubation in obstetric patients is 1/390 [12]. In 2015, the Obstetric Anesthetists' Association and Difficult Airway Society in the UK came together and published the Guideline for difficult intubation in obstetrics [13] (**Figure 1**). Three algorithms are defined according to this guide. These consist of safe obstetric general anesthesia, obstetric failed tracheal intubation, and cannot intubate cannot oxygenate (CICO) steps. The first step is the Pre-induction planning and preparation and planning should be done with a team discussion. RSI is the recommended technique. However, mask ventilation can be performed so that the intraabdominal pressure does not exceed 20 cmH20. The practitioner can attempt at most two times in the presence of difficult tracheal intubation. The third attempt should only be performed by an experienced anesthesiologist. If there is a failure, a failed intubation declaration is made, and help is sought. Continuity of oxygenation is essential. 2 ventilation attempts can be made with a laryngeal mask. Ventilation should be continued with a face mask in case of failure. The 3rd algorithm is initiated if oxygenation fails with the mask. CICO is declared. 100% oxygen is continued to be given. Laryngospasm and insufficient muscle relaxation are excluded. If necessary, neuromuscular blockade is repeated. If oxygenation still fails, the front-of-neck access procedure is applied. If oxygenation of the patient can be achieved before starting the surgical airway, the team should decide according to the clinical condition of the pregnant woman. The patient can be awakened or a decision to continue can be given by evaluating the clinical situation of the pregnant woman and the experience of the operator. Maternal and fetal condition, obesity, surgical factors, aspiration risk, and airway require hazards consideration. Obstetric airway may provide a stressful environment because of failure risk of tracheal intubation and difficult mask ventilation. This may cause a risk of

*Airway Management during Pregnancy and Labor DOI: http://dx.doi.org/10.5772/intechopen.96476*

*Special Considerations in Human Airway Management*

Mandibular protrusion (defect or prognathism)

Difficult intubation story Interincisor distance < 4 cm Tiromental distance < 6 cm Sternomental distance < 12 cm Head and neck extension < 30°

Neck circumference > 40 cm Submental compliance defect

Mallampati 3–4

**Table 3.**

mandible, swollen tongue, and facial edema. The distances that should be measured in the preoperative examination and examination findings that are predictive for direct laryngoscopy and intubation difficulty are given in **Table 3**. In pregnant patients the physiological and the anatomical changes constitute the difficulty for airway management. The susceptibility to hypoxaemia, friability and mucosal

As obstetric patients are prone to have airway management difficulties, preoxygenation is essential to increase the oxygen reserve before anesthesia induction. The ideal way to determine the sufficiency of preoxygenation is to monitor end tidal oxygen (FeO2) concentration. FeO2 < 90% shows inadequate preoxygenation. We have a critical level the oxygen consumption about 250 mL/min. This rate increases during pregnancy. As oxygen is removed from lungs the alveolar partial oxygen pressure decreases during airway interventions. Therefore apneic oxygenation is recommended. Oxygen delivery systems include nasal canula, simple face mask, Ventury mask, non-rebreather mask, insufflation by transtracheal or endobronchial catheters, dual bladed laryngoscopes. High flow nasal cannula is also commonly used for this purpose today. During apneic oxygenation, carbon dioxide levels continue to rise, which can lead to a decrease in pH and respiratory acidosis. However, the use of higher flow more than 15 L/min oxygen during apnea provides better gas

When it is thought that oxygenation and manual ventilation cannot be guaranteed after anesthesia induction in a pregnant woman with difficult intubation, awake intubation is recommended. Expecting a high rate of leakage between the face mask and the face, upper airway collapse as a result of general anesthesia are among the conditions that require awake intubation. Awake intubation can be performed using a video-laryngoscope or flexible bronchoscope [5, 6]. During the procedure, low or, if possible, high flow oxygen applications are recommended to extend the apneic window. If the patient will be intubated under general anesthesia or if it is understood that there is a difficult airway following induction,

engorgement are main causes of failed airway management [2].

*Preoperative examination findings for direct laryngoscopy and intubation difficulty.*

**6. Preoxygenation and apneic oxygenation in obstetric patients**

**184**

washout.

**7. Awake intubation**

the use of a video-laryngoscope is often recommended [7]. Different types of video-laryngoscopes have been presented in studies and case reports. Kariya et al. [8] reported that awake tracheal intubation with Airway Scope is safe in pregnant women with hemodynamic instability.

Topicalization can be performed in different ways. N. Glossopharyngeus nerve block can be performed in palatoglossal arc. It provides the blockade of gag reflex. N. Laryngealis recurrens and superior can be blocked in cervical level. Another technique is to apply local anesthetic infiltration at the oropharyngeal area. Mucosal atomization devices, inhalational lidocaine or lidocaine lolipops are aother alternatives. EMLA contains 2.5% lidocaine and 2.5% prilocaine and is another option for topicalization. The disadvantages include uncooperated patients, oversedation risk and failure due to inexperienced operator.
