Discussion
We here present an elegant and simple NIV of “PhO2-NC” as a SPI technique to measures changes of the PIP and image in the PLS with FB. To the best of knowledge, this is the first study in the medical literature. Even with the prevalence of NIV worldwide, the types of device and the modes of delivery being used vary among institutes and countries. Clinically, this SPI is unique in waives using other supplementary instruments, except a small oxygen catheter, and capability of operator himself optional and easy controllable skill.
The PLS is a fibromuscular tube-like structure that is semicircular in cross section and relatively closed space. It serves as a continuation of the aerodigestive cavity, providing pathway from the nasal and oral cavities to the trachea, esophagus and the bilateral middle ears. PLS boundaries almost with soft tissues of the mouth and the nasal choanae anteriorly; the soft palate, velum, and portion of the skull base superiorly; the tonsils laterally; the inlets of larynx and esophagus inferiorly; and the pharyngeal constrictors posteriorly. Therefore, the PLS is a potential dynamic space which do expand with increasing inside pressure.
FB examination via nasal track offers real-time visualization and assessment of the whole PLS. FB is useful for detecting dynamic images that better demonstrate the presence, location, degree and extent of lesions. In the PLS, an optional action of SPI by PhO2-NC can create an enough and controllable positive distending pressure which helps open and appropriate expand the space, increase the cross-sectional area, and therefore allows accurate and precise inspection the anatomic structure with FB. Especially when there exist collapsed space or dynamic lesions such as pharyngomalacia, kissing tonsils, vallecular cyst, laryngomalacia or glottis malacia laryngeal cleft, etc. as showing in the Figure 2 and Figure 3, which may otherwise remain unrecognized when using traditional technique without proper or controllable pressure in the PLS. In addition, the PhO2-NC itself may provide simultaneous and optional PPV. Which also benefits for the therapeutic intervention of FB such as doing laser partial adenoidectomy and tonsillectomy, check bleeding, marsupialization of vallecular cyst,11epiglottoplasty,16 etc. We have already applied this SPI modality successfully in many pediatric endoscopy interventions of airway9-16 and esophagus.17,18
Physiologically, this PhO2-NC has combinational effects of “apnea oxygenation” 19-23 and PPV. In the setting of PhO2, the continuous flow indeed fully fill the PLS with oxygen. For apnea oxygenation, randomized controlled trials have shown that it can extend the period of safe apnea, reduces the unintended hypoxemia when used in patients after sedation or muscle paralyze, even with difficult airways. PhO2 with addition of optional SPI, positive inflation pressure or PPV can be created for a prolonged period, which allows appropriate and controllable pressures and times to expand the collapsed PLS for FB detail inspection, as well as doing therapy. Furthermore, it may also promote the pressurized oxygen flow into the low airways and lungs.20‐24
The modality of FB with this SPI offers several clinical advantages. Transnasal approach of FB provides a better dynamic assessment for airway movements. The interface of SPI is inside the PLS which much reduces the ventilation deaspace. This SPI is an easy PPV technique that can be performed with only a continuous oxygen flow and a soft catheter sitting in the pharynx that minimizes impeding airway access during FB procedures. It can optionally control and simultaneously accomplish by FB operator himself. SPI can appropriately open and expand a collapsed PLS, as demonstrated in this study, which facilitates the passage of FB for thoroughly examine the PLS. This allows clear visualization of contains, structures and lesions that helps to yield more accurate diagnosis and subsequent effective management, without interference by artificial airway devices of facemask, nasal prong, LMA or ETT. It is technically simple and readily available, therefore, can be used in resource‐limited sceneries. Additionally, it causes less distortion, less invasive, better‐tolerated and cost‐effective compared to the traditional technique. Controlled and appropriately sustained (3 to 5 seconds) inflations may be more effective than short (1 to 2 seconds) inflations in the prolonged expansion of target airway space for better and detailed measurement which not easily be identified at lower inflation levels. Furthermore, these dynamic pressures of SPI may also transmit and facilitate tracheobronchial lumen expansion and lung ventilation. For patients with risk of compromised airway and oxygen desaturation, it may reduce hypoxia, provide ventilation and, therefore, improve patient safety with little medical resources.
Some limitations may exist in this study. There might have variation of the tightness of the nose (mouth)-closure in the same or between operators. This indeed may affect the levels of measured pressure. A more prolonger duration of SPI, up to 15 seconds or more had been reported,3,8 but it was not included in this primitive study because worry its adverse effects of high created PIP. In clinical practice, the real effort of SPI may individualize but that is controlled by the operators.
Nonetheless, the findings of the present study are important and suggest the need for further investigations. Such as the opening pressure of a collapse PLS or occult lesions which can be measured and help for determine subsequent pressure of NIV support. The similar SPI effects in the lower airway lumens, ventilation, and lung recruitment.