Nasal obstruction is
a common complaint in the practice of Otolaryngology. Billions of
dollars are spent on the surgical treatment of this complaint.
Nasal obstruction is
a symptom, not a diagnosis, and there are a range of medical and
structural conditions that can cause such symptoms.
There are four nasal
valves or flow limiting segments: external valve, internal valve,
septal valve, and inferior turbinates.
Either a narrow or
a very wide nasal passage can affect the air column. When the normal,
turbulent air flow pattern is disturbed, it is perceived as nasal
obstruction. This helps explain the few patients that complain of
persistent nasal obstruction in the postoperative period even with
a widely patent nasal passage.
Airflow within the
nose is both smooth and turbulent. Each flow component is important
in the perception of "normal" nasal function. Smooth airflow
provides movement of air toward the lower respiratory tract. Turbulent
airflow causes eddied currents within the nostril. This allows for
the distribution of the air column across a larger surface area
for conditioning and for the air to reach the olfactory area.
The paired external
valves consist of the lower lateral cartilage, the columella, and
the nasal floor. Active dilatation of this valve occurs with each
inspiration by action of the nasalis muscles. Malfunctions in this
area can be the result of trauma, facial nerve palsies or congenital
anomalies of the alar cartilage.
The paired internal
valves consist of the caudal end of the upper lateral cartilage,
the nasal septum, and the soft tissue surrounding the piriform aperture.
This valve is located at the anterior end of the inferior turbinate.
The aging process can adversely affect the internal valve function
by decreasing tissue elasticity and causing further collapse.
The nasal septal valve
is composed of the perpendicular plate of the ethmoids posteriorly,
the quadrangular cartilage anteriorly, and the vomer inferiorly.
The maxillary crest
and palatine bones complete the septal floor. The septum is uniquely
constructed to absorb direct trauma. The quadrangular cartilage
articulates directly with the bone posteriorly and inferiorly. Direct
cartilage-bone articulation is rare without intervening ligaments
and it is this unique construction that allows more lateral mobility.
Studies show that anterior
deflections of the septum account for most of nasal symptoms associated
with septal deformities. Smaller, anterior deflections are much
more important in the perception of nasal airflow than larger posterior
The inferior turbinates
contain special erectile tissue consisting of venous sinusoids surrounded
by smooth muscle. There is a normal nasal cycle in which this erectile
tissue vasodilates and vasoconstricts. The cycle occurs approximately
every four hours, first one side then the other. Although the nasal
cycle is a normal phenomenon, this pattern can sometimes be confused
as obstructive symptoms.