ventilation can be performed with a limitation of a maximum peak airway pressure of 20 cmH2O in order to avoid overcoming the tone of the lower esophageal sphincter and insuffating the stomach with oxygen [30, 31].

Endotracheal Tube (ETT)

Although an ETT is the most de nitive and most reliable airway device in patients undergoing general anesthesia, an ETT has challenges when inserted in a patient with central airway obstruction undergoing a therapeutic bronchoscopic procedure. Insertion of the ETT does not allow the bronchoscopist to examine the vocal cords and the upper part of the trachea for pathology. The large external diameter of the therapeutic fexible bronchoscope requires the insertion of an ETT with an internal diameter of 8.5 mm or 9 mm in order to deliver adequate ventilation around the bronchoscope (Fig. 5.4). The length of the ETT projecting from the patient’s mouth limits the length of the fexible bronchoscope available for insertion into the airway, and the proximal end of the ETT is commonly cut off. Insertion

Fig. 5.4  EBUS bronchoscope introduced through ETT

of an ETT in a patient with pre-existing tracheal or bronchial stents carries a risk of dislodging or deforming the stents, which can potentially result in airway compromise [32].

Rigid Bronchoscope

The rigid bronchoscope is an ideal airway device in complicated interventional bronchoscopic procedures where instruments and stents are inserted in the airway. The distal end of the rigid bronchoscope is beveled to allow for lifting of the epiglottis and safer insertion through the vocal cords. The proximal end of the rigid bronchoscope can remain open to air to allow for simultaneous insertion of multiple instruments. Leak of the ventilating gas through the open end of the rigid bronchoscope makes jet ventilation or spontaneous ventilation the only possible modes of ventilation. Alternatively, when a cap is placed to seal the proximal end of the rigid bronchoscope, positive pressure ventilation from the anesthesia ventilator can be used. Leak is overcome by inserting a throat pack and Vaseline gauze to occlude the nostrils. A short stainless steel cylinder attached to the proximal end of the rigid bronchoscope has multiple side ports to accommodate a jet ventilator, an anesthesia circuit, and bronchoscopic instruments [33].

The rigid bronchoscope has many advantages over the fexible bronchoscope. These include the ability to provide positive pressure ventilation during lengthy airway procedures and the ability to insert instruments with a large diameter into the airway such as the microdebrider, large suction catheter, and the deployment device for silicone stents. The rigid bronchoscope can also be used as a coring device to debulk airway tumors, dilate stenotic areas, stent the airway open in the case of external airway compression by an anterior mediastinal mass, and tamponade airway bleeding [34].

Modes of Ventilation

Spontaneous Ventilation

Spontaneous ventilation is necessary in cases when the integrity of the airway is compromised, such as tracheoesophageal stulas, broncho-

esophageal stulas, and iatrogenic tears in the airway. In such cases, positive pressure ventilation can result in leakage of the ventilating gas (oxygen and/or air) to the mediastinum, the thoracic cavity, and possibly the peritoneum. Anterior mediastinum mass is another indication for spontaneous ventilation because of multiple reports of worsening of the compressive obstruction of the central airway by the mass after a muscle relaxant was given. In addition, spontaneous ventilation is valuable during pleuroscopy, when collapse of the lung on the side of the procedure is essential for visualization.

Spontaneous ventilation can be easily achieved under conscious sedation, MAC, or general anesthesia. Inhalation anesthetics or intravenous anesthetics with adequate topical anesthesia can be used, without the muscle relaxant, for the insertion of the rigid bronchoscope, LMA, or the ETT. Alternatively, a small dose of the short-­acting muscle relaxant succinylcholine can be used for the intubation with rapid regain of spontaneous ventilation.

Assisted Ventilation

In a patient with an airway device in place, ventilation can be assisted by multiple modalities to overcome hypoxia and/or hypercapnia associated with spontaneous ventilation under general anesthesia. For example, intermittent handbag ventilation with a large tidal volume, pressure support, or synchronized intermittent mandatory ventilation can be used to overcome atelectasis and improve saturation and CO2 elimination during bronchoscopic procedures.

Noninvasive Positive Pressure Ventilation (NIV)

NIV, commonly used for patients with sleep apnea, has been described as bene cial in hypoxemic patients undergoing bronchoscopy with anesthesia. Modi ed nasal or full-face masks, with a special adaptor to allow for the insertion of the bronchoscope, can be used. NIV should be considered when endotracheal intubation and mechanical ventilation is suspected to carry an increased risk to the patient undergoing bronchoscopy. The use of NIV ventilation was shown

to improve oxygenation and reduce the risk of acute respiratory failure after bronchoscopy in patients with impaired baseline oxygenation, such as chronic obstructive pulmonary disease (COPD) patients with pneumonia or immunocompromised patients [35, 36].

Positive Pressure Controlled Mechanical Ventilation

Patients undergoing interventional bronchoscopic procedures that require muscle relaxation need mechanical ventilation. Mechanical ventilation can be delivered through the LMA, ETT, or rigid bronchoscope. When the LMA is the airway device of choice, the peak airway pressure should be kept below 20 cmH2O to avoid opening the lower esophageal sphincter and infating the stomach. Mechanical ventilation through the rigid bronchoscope is associated with leakage around and through the rigid bronchoscope. To overcome such leak, insertion of a throat pack, occlusion of the nostrils with Vaseline gauze, capping of the rigid bronchoscope ports, and high oxygen fow rates with high tidal volumes are needed.

Jet Ventilation

Jet ventilation can be performed using a handheld device through which 100% oxygen is injected into a port at the proximal end of the rigid bronchoscope. The pressure of the injected oxygen can be adjusted with a dial; the frequency of ventilation is left to the operator to select and frequently ranges from 8 to 20 breaths per minute. Jet ventilation should be performed only when the proximal end of the rigid bronchoscope is open to air, to avoid barotrauma [37]. Air is entrained at the open proximal end of the rigid bronchoscope, causing variation in the delivered FiO2.

Electronic Mechanical Jet Ventilation

The mechanical jet ventilator (Acutronic Medical Systems, Hirzel, Switzerland) has many advantages over the simple handheld jet ventilator [38]. The user can control the FiO2, the frequency of ventilation (up to 150 breaths per minute), and the driving pressure of ventilation (up to 40 mmHg). The inspired oxygen can be humidi ed up to