DISCUSSION
FE-NIV-SPI is a safe and simple technique that can be routinely applied under common procedural setting to detect LC in infants. The usage of nasopharyngeal catheter to deliver continuous oxygen flow and application of nose-closure maneuver to generate airway pressure to expand PLS and AET lumens, allowing detailed visualization of the LC.
Hypoxia and hypoventilation are frequent complications of pediatric FE interventions, therefore the usage of supplemental oxygen and PPV are highly recommended.21-23 Without pneumatic stenting of SPI, as traditional method of FE, hypopharynx, posterior larynx and upper esophagus remain collapsed and the LC may otherwise stay undetected. Over the past two decades, we have incorporated FE-NIV-SPI technique as the default method to maintain oxygenation and ventilation in our endoscopic practice. This allows us to perform many bronchoscopic interventions that otherwise cannot be safely performed in infants with severe asphyxia condition.13-19 If FE-NIV-SPI is routinely applied in all FE, this review suggest that it may detect more LC at the first laryngeal examination. Although the deeper involved lesions, such as type IV, may still need a RE to confirm, the most commonly types of I, II and III LC defects can be diagnosed reliable with FE-NIV-SPI. That may allow waiving more invasive and complicated procedures of RE, general anesthesia and radiologic examinations.
For LC, an early diagnosis is crucial for subsequent management to prevent morbidity or mortality. Traditionally, being widely available and easily handled, FE plays an essential role in exploring lesions that cause airway and respiratory problems in pediatric patients.24-26 However, FE has not been considered a commendable tool to evaluate the posterior commissure of the larynx where lesion as LC may fail to recognize.27 RE is more capable and remains the gold standard for confirmation of LC.3-7 However, there may have technical difficulties and risky, especially in small infants who already have respiratory distress, need transfer to operation room and receive general anesthesia. Their short oral cavity limits in securing the RE instrument. The review suggests that these disadvantages can be effectively counteracted by the application of FE-NIV-SPI, especially in type I, II and III LC.
SPI with simultaneous chin-lift help to pneumatically expand the PLS including larynx, hypopharynx, esophageal inlet and upper esophagus. In our prior study19 of identical setting, the SPI with duration of 0 to 5 seconds could create linear correlated positive pressure levels from 4.1±3.3 to 65.5±18.5 cmH2O in PLS. When the nose was open (SPI 0 second), the intra-PLS pressure around 4.1±3.3 cmH2O, the surrounding structures were relatively collapse included the posterior glottis space. LC may be inadvertently overlooked as a result of redundant mucosa between esophagus and trachea apposing each other and sealing the cleft (Figure 2a), as those seven referred infants had done FE in the traditional way. During the SPI, the intra-PLS pressure gradually rising and sustaining up to 60 cmH2O, which were high enough to open the collapsed lumens of AET and the esophageal sphincter. These dynamic changes of pressure levels could be optionally and safely controlled by operator. The LC, if existed, could be well visualized (Figure 2b, c), probed and dispersed with the tip of FE or forceps to assess the depth and grading the cleft. The whole AET lumens, included trachea and esophagus, could be detail investigated. These dynamic events allowed for repeat and precise evaluation by FE.
This FE-NIV-SPI technique provides several advantages. 1) Oxygen insufflation alone through the nasopharyngeal catheter can flush upper airway dead space, as the effects of “apneic oxygenation”,28-30 which can significantly prolong onset of desaturation. 2) Both assist inspiration and expiration can be achieved by simple maneuvers of nose-closure and abdomen-compression, respectively, to provide adequate oxygenation and PPV. 3) No other supplemental instruments such as mask, endotracheal tube, ventilation bag, or ventilator are needed, therefore it is cost-effective, eliminate procedural time and provide an unimpeded field for FE manipulation. 4) In addition to the LC, other coexisted lesions such as laryngomalacia,6 vallecular cyst,18,I9 trachea, bronchial or esophageal pathologies also can be detected and managed in the same FE session.16,17 5) Furthermore, it facilitates therapeutic interventions15-18 such as laser ablation, balloon measurement, stent implantation and repair in cardiopulmonary compromised children.
There are limitations in this study. 1) Although FE-NIV-SPI is easy for detecting most type I, II, and III LC, severe type IV LC may difficult to fully visualize and not with diagnostic certainty. Confirmatory RE is still necessary to determine the deeper cleft length and guide the management approach, as it remains the gold diagnostic standard. 2) Although the technique of FE-NIV-SPI have previously been reported,13-15 this may still be unfamiliar to many pediatric pulmonologists. Repetitive practice of this technique may be necessary to develop skill competency. 3) This report is from one single institution experience and the case number may not enough to make definitive conclusion. For this rare incidence and occult lesion of LC, further multi-center cooperative investigations are needed to verify the early detection with this FE-SPI technique.