**5. Pitfalls and tips**

## **5.1 Learning curve for VS technique**

It is intuitive to think that DL is a difficult skill to acquire and, VL must be an easier technique for novice trainees to learn. The studies of the learning protocol in normal airway and simulated difficult airway mannequin model usually results in superiority of VL over DL (e.g., better view; shorter intubation times, higher overall success rate, less dental trauma and esophageal intubation) [207–214]. Meanwhile, practicing may improve DL and VL skill competency and the rating of overall ease of use for DL/VL. Opposite learning results (DL faster than VL) in various simulation teaching programs were also reported [215, 216].

The VS technique has been tried in patients with difficult airway related to limited mouth opening [217]. Furthermore, the VS technique has been compared head to head

#### **Figure 29.**

*Application of VS technique for tracheal intubation in a patient who was undergoing cardiopulmonary resuscitation (CPR). This is a 69-year-old man (BMI 24.2 kg/m<sup>2</sup> ) with lung squamous cell carcinoma and tongue squamous cell carcinoma with metastasis. Neck mobility was limited due to prior tumor-wide excision and neck dissection. Code blue was announced due to massive hemoptysis and in-hospital cardiac arrest in this patient. After repeated attempts of tracheal intubation with VL/DL failed, the airway management rescue team successfully intubated the patient using VS technique while CPR was uninterrupted. The intubation time is 6 s. White arrows denote a suction catheter. (Also see the Supplementary Materials Video S27).*

with VL in a normal airway vs. difficult airway due to limited mouth opening mannequin-based study. However, in the difficult airway model, VS was quicker to intubate [149, 218]. Similar results were reported when VS was compared with DL [64, 219, 220]. A semi-rigid VS had the advantages of better maneuverability, superior view of the glottis, and shorter intubation time than a rigid VS. However, when compared with VL in real surgical patients, semi-rigid VS was not superior to VL on intubation time and first-pass success rate [221].

The learning curve for proficiency with optical stylets is reported to be from 10 to 20 uses. In real world experience, we found that the learning curve for performing VS technique by novice trainees (interns and residents) is great. Usually, with a reasonable person standard for these learners, they can accomplish the tracheal intubation task in patients with normal airway. The performance on the task is evaluated by their number of attempts. Usually, the number of trials ranges from 1 to 10 (a steep learning curve). It should be mentioned that our novice trainees always receive structured training courses on cadaver and mannequins before performing on actual patients. **Figures 30** and **31** shows the tracheal intubation with VS technique by an intern.

#### **5.2 Mucus, saliva, secretion, blood**

All the optical intubating tools are affected by heavy mucus, secretions, liquid, and gross blood. Simple suctioning is effective in removing these contaminants which easily obscure the optic aperture of the stylet (VS) or scope (VL) and prevent

#### **Figure 30.**

*Application of VS technique for tracheal intubation in a morbidly obese patient (BMI 34.7 kg/m2 , 167 cm, 97 kg) who underwent percutaneous nephrolithotomy for renal stones. His past medical history includes heart failure due to idiopathic dilated cardiomyopathy, diabetes, hypertension, and he has an implanted cardioverter–defibrillator. Airway management was performed by a competent intern who had a quick learning curve on face mask ventilation and VS technique.*

#### **Figure 31.**

*Application of VS technique for tracheal intubation by a novice trainee (intern). The same patient as in Figure 30. (A) Tongue. (B) Soft tissue. (C) Vallecula (arrow). (D) In front of the epiglottis (arrow). (E) Vocal cords. (F) Entry into trachea. The intubation time is 25 s. Also see the Supplementary Materials Video S28).*

#### **Figure 32.**

*Application of VS technique for tracheal intubation in a patient with copious secretions in the airway. This is a 65-year-old man with BMI 27.8 kg/m2 . Prior surgical history included cervical spinal laminoplasty (C4-7 stenosis). The intubation time is 42 s. (Also see the Supplementary Materials Video S29).*

#### **Figure 33.**

*A case complicated by copious secretions and bleeding during tracheal intubation. This is a 49-year-old man (BMI 31.8 kg/m2 ) with cirrhosis of liver, pneumonia, and respiratory failure. Debridement was performed for gouty tophi and infection in his extremities. (A) The patient was resting in the ward prior to operation. (B) Before induction of anesthesia. (C) After tracheal intubation was accomplished. (D) Mixture of mucus, saliva, and secretions removed from the patient's airway after intubation.*

adequate visualization. In addition to good suctioning, some have proposed that oxygen insufflation will help clear secretions and lead to a better view [222].

Prior to induction of anesthesia, we always ask patients to clear their throat by swallowing any saliva. In addition, if not contraindicated, we would give an antisialagogue to reduce the secretions. Usually, this is enough to obtain a clean and clear airway for insertion, advancement, and maneuvering the VS inside of the patient's oropharynx. **Figure 32** shows a patient who had copious secretion during tracheal intubation process.

When patients are bed-ridden or in critical or emergent conditions, it is quite common that they have a significant amount of saliva, mucus, and/or blood in their airways. **Figure 33** shows an unexpected worst-case scenario in a patient in critical condition. Prior to VS, it was not recognized that the patient had a huge amount of mixed secretions, mucus, and blood in his oropharynx. When the picture obtained from VS optical lens appeared onto the video screen, nothing was easily identified (**Figure 34**). We were still able to navigate in the oropharyngeal space and advanced the stylet into the glottis eventually (**Figure 34**). In the same patient, after his airway was secured by VS, it was still a struggle to clear the copious secretions to obtain a view by VL of the glottis and ET tube (**Figure 35**).

There are occasional cases with head and neck cancer where FOB is advisable over VS. In such a patient with laryngeal cancer who had received multiple radiation therapies, the mouth opening was limited, the neck was stiff, and the hypopharynx and glottis were swollen (**Figures 36** and **37**). VS was tried after induction of anesthesia (**Figure 38**). However, copious mucus, secretions, and saliva seriously obscured the visualization of the spotted optic lens on the VS. The epiglottis could not be lifted up at all. The airway

#### **Figure 34.**

*A case complicated by copious secretions and bleeding during tracheal intubation. The same patient as in Figures 33 and 35. Serial close-up view from VS camera. A bunch of mucus and blood mixtures were seen and blocked the view for advancement of the stylet (A–D). After struggling, a clear glottis view was eventually obtained (E) and ET tube was successfully secured into trachea (F). The intubation time is 80 s. (Also see the Supplementary Materials Video S30).*

#### **Figure 35.**

*A case complicated by copious secretions and bleeding during tracheal intubation (the same patient as in Figures 33 and 34). After airway secured by VS, VL was used to examine patient's airway. (A–C) Serial close-up views from VL camera show a bunch of mucus and blood mixtures blocking the view in the patient's airway. (D) After adequate suction, the views became clearer. (Also see the Supplementary Materials Video S31).*

was eventually secured with FOB (**Figure 39**). **Figure 40** shows the intubation images of the same patient during his elective tracheostomy 3 weeks later. Tracheal intubation was performed by FOB. This extreme clinical case should be regarded as the limit of using VS technique in comparison to the conventional role of FOB.

#### **5.3 Video-video paired technique**

Combined use of DL/VL with FOB has been a common alternative in certain anticipated difficult airways [223–231]. Similarly, it has also been thought to combine VL and a particular shaped stylet (or bougie-kind of introducer). When lighted or optical stylets became available, it was natural to combine both for tracheal intubation in scenarios like ankylosing spondylitis, morbid obesity, or certain congenital anomalies involving orofacial or head/neck regions. Using an appropriate videolaryngoscopic blade may create better oropharyngeal space and laryngeal views and therefore may reduce stylet use in patients with normal airway [8], but not replace stylet use in morbidly obese patients [123].

In a patient with a difficult airway, after several attempts at laryngoscopy had failed, endotracheal intubation was accomplished by the combined use of a laryngoscope and the Bonfils rigid fiberscope [232, 233]. This successful combo technique involved two airway managers. One used a laryngoscope to displace the patient's tongue to the left ventral part of the mouth and cleared the airway by suctioning. The other one inserted the Bonfils rigid fiberscope, followed the blade of the laryngoscope to the larynx, obtained a good view of the vocal cords, and railroaded the ET tube into the trachea. It was reported the intubation time was 20 s. Although it was not known

#### **Figure 36.**

*An extreme and anticipated difficult airway in a patient with mandibular sarcoma. Repeated surgical treatments (tumor wide excision, neck dissection, mandibulectomy, free flap reconstruction) and concurrent chemoradiotherapy were performed. (A) Pre-operative endoscopic examination showed swollen glottis. (B, C) Limited mouth opening and stiff neck due to radiation therapy. The face mask ventilation was adequate to maintain oxygenation. (D) After nasal tracheal intubation using fiberoptic intubation. (E) After tracheostomy. (F) During surgery.*

the exact underlying cause for the several failed attempts at laryngoscopy in this patient, successful rescue with VS in 20 s is reasonably acceptable.

The shape of the stylet may affect the effectiveness and performance of VL in patients with normal airways [234]. The combined use of VS and VL has been helpful in patients with normal [235] and difficult airways [14, 34, 35, 236]. While VS has been used as an adjunct to DL/VL, we prefer to reverse the ancillary relationship between VS and VL/DL. Namely, we proposed the DL/VL play an adjunct to VS. The role of DL/VL is to open the airway, create minimal oropharyngeal space, lift up the epiglottis, and finally allow VS to pass through under the epiglottis and acquire a better glottis view. It is worthy to mention that this combination method (VS-VL) has been applied in many difficult cases at our institute. One example involves a patient with mucopolysaccharidosis (MPS) who also had prior C-spine surgery and was receiving a corneal transplantation. He had a limited mouth-opening and flaccid epiglottis which could not be lifted up by jaw-thrust maneuver at all. However, with the aid of VL, tracheal intubation was smooth and swift with VS technique. Another case involved a morbidly obese patient (BMI 56 and 60) who underwent two separate operations (UPPP and bariatric surgery) at our institution. Several attempts at tracheal intubation with various intubation tools failed. With the aid of VL, tracheal intubation was eventually accomplished by VS technique without complications.

#### **Figure 37.**

*Adoption of VS (A) and FOB (B) in the same patient as in Figures 36–40. It is noted that, after failure of VS technique, FOB was used to establish nasal tracheal intubation.*

#### **Figure 38.**

*Serial views from VS camera during tracheal intubation (same patient in Figures 36–40). (A–C) The oropharynx was crowded due to radiation fibrosis of the neck. (D–F) Copious secretions and saliva were noted. The epiglottis (labeled by the yellow star) was firmly attached to the posterior pharyngeal wall when the patient was anesthetized and paralyzed (E–H). The maneuverability of the VS was seriously hindered by the limited mouth opening and rigid neck. Intubation failed after several attempts.*

#### **Figure 39.**

*Rescued intubation with FOB when the patient's controlled ventilation was reverted back to spontaneous respiration. (A–D) The epiglottis (labeled by the black star) was firmly attached to the posterior pharyngeal wall. (C, D) There appeared a tiny slit only when the patient exhaled. The airway operator then took this chance to sneak the FOB tip through this tiny slit and passed under the epiglottis. Subsequent views of swollen glottis (E, F) and vocal cords (G, H). Same patient as in Figures 36–40.*

#### **Figure 40.**

*Awake FOB under light sedation was performed in the same patient 3 weeks later. Elective tracheostomy was scheduled because it became progressively more difficult for the patient to breathe. (A, B) The epiglottis was lying against the posterior pharyngeal wall and there was a very narrow space to allow air to breathe out. A nasogastric feeding tube was seen. (C) A partial view of glottis under the epiglottis. (D) View of closed vocal cords. (E) The tip of a suction catheter was seen and it was withdrawn back later. (F) Vocal cords was in the closed status before the fiber's entry into trachea. Same patient as in Figures 36–40.*

In contrast to previous experiences of using the combined VS/VL technique in difficult airway clinical scenarios [34, 35] and in mannequin models [237], we have routinely applied this technique in normal airways in our daily practice. Included among our routine use of VS-VL for daily practice are cases of intraoperative neurophysiologic monitoring (IONM) during thyroidectomy [238]. The IONM allows confirmation of the functional integrity of the recurrent laryngeal nerve as well as facilitates identification of the RLN before visualization during operations. While VS technique provides an accurate and swift tracheal intubation (e.g., especially in the presence of a giant goiter), VL ensures the contact surface of a specialized EMG endotracheal tube (e.g., Xomed and TriVantage Nerve Integrity Monitoring (NIM) ETTs, Medtronic Xomed Inc., Jacksonville, FL, USA) can been seen and placed in the correct spot between the vocal cords.

Here we demonstrate two cases of using the VS-VL paired technique in patients with normal airways during our routine practice. **Figures 41** and **42** shows a patient with a flat epiglottis and **Figures 43** and **44** shows another patient with an omegashape epiglottis. Neither epiglottis prevented the convenience and ease of using VS-VL paired technique to intubate.
