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.