Nasal airway obstruction and its management

Dr. T. Balasubramanian

6/3/2010 Otolaryngology online drtbalu

Nasal air way obstruction and its management

Introduction:

Nasal obstruction is an important symptom of many underlying disorders, and is the

most common cause for visiting an otolaryngologist. It should be borne in mind that

nasal obstruction is a symptom and not a diagnosis. These patients hence should be

evaluated for both subjective / objective nasal obstruction. Nasal patency these days

can be evaluated objectively based on the anatomy of the nasal cavity and physiology

of nasal air flow which can be studied using a Rhinomanometer.

Subjective feeling of nasal block could be due to the following factors:

1. Sensitivity of pressure receptors in the nose

2. Sensitivity of thermal receptors in the nose

3. Sensitivity of pain receptors in the nose

4. Presence of excessive secretions in the nose

The cause for nasal obstruction is considered to be multifactorial which includes both

subjective and objective causes.

Anatomic causes of nasal block:

Nasal valve area problems: Nasal valve area is considered to be the narrowest

portion of the human airway. Anatomically it has two components i.e. External and

internal nasal valves. The anatomy of internal nasal valve was first described by

Mink in 1903.

Boundaries of internal nasal valve include:

1. Dorsal portion of nasal septum medially

2. Inner caudal edge of upper lateral cartilage laterally

3. Anterior head of inferior turbinate posteriorly

The internal nasal valve area is supposedly the narrowest portion of human airway

has a cross sectional area of approximately 40 – 60 mm2. This area accounts for

nearly 2/3 of the whole airway resistance. Hence collapse / stenosis of this area

accounts for one of the commoner causes of nasal block.

External nasal valve is also known as nasal vestibule. It is bounded by the caudal

edge of the lateral crus of the lower lateral cartilage, fibrofatty tissue over the ala and

the membranous septum.

Diagram showing the nasal valve areas

The nasal vestibule should be considered to be the first component of the nasal

resistance mechanism. If the nasal airflow rate exceeds 30 litres / minute, the

vestibule of nose collapses causing a reduction in the rate of nasal airflow. This

collapse of ala increases the nasal resistance.

On inspiration, the increased velocity of air flowing through the nasal valve area will

cause a drastic decrease in the introluminal pressure causing a vacuum effect on the

upper lateral cartilages. This inward pull causes collapse of upper lateral cartilage

(Bernoulli's principle). Total collapse of the internal nasal valve area duing this

scenario is prevented only by the reselience of the upper and lower lateral cartilages.

Collapse of external nasal valve area (alar area) is by contraction of dilator nari

muscles during inspiration. During expiration the positive pressure prevailing inside

the nasal cavity keeps the nasal valve area open.

Causes of nasal obstruction:

1. Previous trauma / rhinoplasty surgical procedure are the common causes of

nasal obstruction due to weakening of nasal valves

2. If there is associated nasal septal deviation then nasal obstruction becomes

exponentially increased

3. Mucociliary clearance mechanism in patients with deviated nasal septum is

slowed considerably when compared to that of normal individuals. Stagnant

secretions inside the nasal cavity may aggravate nasal obstruction

4. Penumatization of middle turbinate (Concha bullosa) an anatomical variant can

cause significant amount of obstruction in the middle meatal area. Massive concha

may cause middle meatal nasal obstructive syndrome leading on to symptoms like

headache, nasal block and anosmia. Commonly majority of these patients also have

deviated nasal septum which may aggravate nasal block.

5. Neuromuscular causes like facial palsy and aging. Facial palsy may cause

paralysis of dilator naris leading on to nasal obstruction. Aging on the other hand

could weaken the fibroareolar tissues present in the lateral nasal wall leading to

collapse of nasal valve area leading on to nasal obstruction.

6. Sinonasal inflammatory diseases. Commonly allergic rhinitis causes

congestion and enlargement of nasal turbiantes and mucosa causing nasal bock.

These patients classically have nasal obstruction on lying down.

7. Drug induced iatrogenic nasal block (Rhinitis medicamentosa). Rebound nasal

congestion is very common in these patients. These patients also have loss of ciliated

columnar cells and increase in capillary permeability causing interstitial oedema.

During early phases of rhinitis medicamentosa this oedema is reversible. If it

continues for a period of more than 3 months it gradually becomes irreversible

leading to difficult situations to manage. Systemic medical therapy like reserpine

(antihypertensive), beta blockers, antidepressents can cause nasal block due to their

actions on the autonomic nervous system.

8. Hypothyroidism may lead to nasal congestion and block due to unknown

reason. Supplements of thyroxine will mitigate these symptoms.

9. Pregancy rhinitis – (Rhinopathia gravidorum) seen commonly during the first

trimester of pregnancy can cause nasal block due to unknown mechanism.

Generalized fluid retention during pregnancy and exposure of nasal mucosa to

persistently elevated levels of oestrogen leads to persistent intertitial oedema. It has

also been suggested that elevated levels of oestrogen and progesterone during

pregnancy may cause rhinits by causing a shift in the level of neurotransmitters like

substance P and nitirc oxide.

10. Trauma may cause nasal block due to the following factors: tissue oedema

causing physical blockage to airflow, secondary sinusitis, and impaired sensation to

air flow due to damage sustained by nasal receptors.

11. Neoplams involving the nasal cavity can cause nasal block. Nasal block in

these patients may be associated with other non specific symptoms like epistaxis and

anosmia prompting the patient to seek medical attention.

Patients with fixed anatomical nasal obstruction may experience intermittent

symptoms secondary to nasal cycle and other autonomic phenomenon. By and large

normal nasal cycle is usually unnoticed by the patient. When there is associated

anatomical fixed nasal obstruction then the patient becomes aware of the presence of

nasal cycle.

Factors controlling nasal resistance:

In normal healthy subjects the nasal airway resistance is determined by the degree of engorgement

of venous erectile tissue, as well as the accessory muscles of respiration which keep the nasal

airway patent. The venous erectile tissue of nasal mucosa has dense adrenergic innervation which

when stimulated cause intense vasoconstriction thereby decreasing the nasal airway resistance.

Normally there is a continuous sympathetic vasoconstrictor tone to the nasal erectile tissue keeping

the nasal airway resistance under check. Reduction in this sympathetic tone increases the nasal

airway resistance. The parasympathetic tone in the nose controls nasal secretion, but has little role

in nasal resistance.

Role of complete history / clinical examination in diagnosing the cause for nasal

obstruction:

It is very important to elicit a complete history from the patient. This will invariably

point towards the correct cause for nasal block. These patients must be diligently

quizzed for prolonged use of drugs, nasal drops which could cause iatrogenic nasal

obstruction.

History of previous surgeries in the nose which includes cosmetic surgery should be

sought. This can invariably point towards the possible cause of block.

Presence of midface deformities (congenital / due to injuries) should also carefully

sought for. History of mouth breathing and halitosis will invariably confirm the

problem of nasal block.

Nasal cavities should be examined for evidence of sinusitis. Any discharge from the

nasal cavity indicates infection. Adenoid hypertrophy should be ruled out in young

children with nasal obstruction as it is the commonest cause in them.

Assessment of facial nerve function:

Facial nerve integrity should be assessed in these patients. Facial nerve paralysis will

hamper the splinting muscles of the ala of the nose causing collapse of the airway on

inspiration.

Examination of the nasal cavity pertaining to airflow dynamics:

Nasal cavity should be examined with specific focus on the probable sites of nasal

resistance. Evaluation should begin with specific focus on external support structures

followed by a detailed assessment of internal support sturctures. Nasal valve area

should be carefully assessed by performing Cottle's test. In this test the cheek of the

patient is pulled outwards and upwards. If it affords relief from nasal block then

obstruction should be considered to be due to anamalous / abnormal nasal valve area.

False negative Cottle's test is possible when the presence of synechiae in the nasal

valve area prevents opening up of this zone when this test is being performed.

As a first step the internal nasal valve area should be examined endonasally as this

area contributes the maximum to the airway resistance. This area should be

examined just by lifting the tip of the nose. Introduction of nasal speculum would

distort this area and hence should be avoided.

CT scan showing a large concha occupying the whole nasal cavity

Malignant nasal mass seen occupying the nose

CT scan showing hypertrophied nasal mucosa on both sides due to allergy

A simple technique which can be used as an alternative to Cottle's test is using a nasal

speculum to lateralize the upper lateral cartilage from the inside of the nose and the

patient is asked whether there is improvement in symptoms. This test has the added

advantage of direct observation of the nasal valve area as it is widened.

Diagnostic nasal endoscopy:

This is the most efficient way of completely examining the interiors of the nasal

cavity. 30 degrees 4 mm nasal endoscope is preferred for this purpose because of its

wide viewing angle. Ideally speaking the nasal endoscopic examination should be

performed before and after nasal decongestion. If nasal obstruction improves on

decongestion alone then nasal obstruction could be due to mucosal inflammatory

disorder affecting the inferior turbinates. If there is no response to nasal decongestion

then the probable cause for nasal obstruction could be:

1. Nasal valve area obstruction

2. Septal deviation

3. Bony hypertrophy of inferior turbinate

4. Rhinitis medicamentosa

During diagnostic nasal endoscopy the presence of anatomical variations should also

be observed. Common anatomical variations that could cause nasal block include:

1. Septal deviation

2. Presence of concha bullosa

3. Intranasal masses

4. Presence of adenoid enlargement

Diagnostic alogrithm for nasal block

Nasal endoscopy is an useful tool in assessing subtle nasal mucosal inflammatory

changes like mucosal nodularity, friable mucosa and synechiae.

Role of radiology in assessing patients with nasal block:

CT scan is helpful in evaluating bony structural abnormalities like deviated nasal

septum, choanal atresia, concha bullosa, inferior turbinate hypertrophy, F.B., rhinolith

etc.

MRI because of its excellent soft tissue imaging capacity is very useful in identifying

lesions like meningocele, encephalocele etc.

Objective evaluation of nasal block:

The following tests would help us to objectively evaluate nasal block.

1. Hygrometry: This is one of the first methods to objectively assess nasal airway

patency. This technique was first described by Zwaardemaker in 1884. This

procedure is performed by asking the patient to breathe on a mirror. A comparison is

made between the diameter of the fog produced by each nasal airway.

2. Hum test: This test was first performed by Spiess in 1902. He assessed the

nasal airway by the change in timbre of the sound caused due to nasal block. He

performed the test after decongesting one nose, blocking the decongested nose and

asking the patient to hum a tune. The change in timbre caused due to block in the

non decongested nose is appreciated.

3. Peak nasal inspiratory flow

4. Acoustic rhinometry

5. Rhinomanometry

Peak nasal inspiratory flow:

This is a very simple, cost effective, reliable and objective measure of nasal airflow

obstruction. In 1980 Youlten developed a peak nasal inspiratory flow meter which

was non invasive, portable, simple to use and economical to own. The peak nasal

inspiratory flow rate is determined by two factors i.e. Nasal obstruction and the

maximum negative pressure generated by the lower airway. Hence changes in

inspiratory effort or lower airway resistance will alter the peak nasal inspiratory air

flow independent of nasal obstruction. To overcome this problem Taylor suggested to

assess Blockage index.

Blockage index = Peak oral flow – Peak nasal flow / Peak oral flow. According to

Taylor Blockage index correlated well with Rhinometry values.

Figure showing equipment to record Peak nasal inspiratory flow

Acoustic Rhinometry:

This was first introduced by Hilberg in 1989. This technology was originally used

for oil exploration. It was only in 1970's this technology was started to be used for

medical diagnosis. This is the most common method used to assess the nasal cavity

air way geometry. This can be used for studying:

1. Anatomical variations of nasal cavity

2. Post surgical changes inside the nasal cavity

3. Effect of drugs on nasal resistance

4. Assessing the changes in the mucovascular component of the nasal erectile

tissues.

Components of acoustic rhinomanometer:

1. Sound source

2. Wave tube

3. Microphone

4. Filter

5. Amplifier

6. Digital converter

7. Computer

Sound waves generated by acoustic rhinomanometer is transmitted through the nasal

cavity, these sound waves get reflected back from the nasal passages and is recorded

by the microphone placed at the entrance of the nasal cavity. These sound waves are

converted to digital signals and a computer recording is made which is known as the

“Rhinogram”. Rhinogram usually provides a two dimensional assessment of the

nasal airway. The cross sectional area of nasal cavity varies at different points from

the nasal rim and these variations are detected by changes in acoustic impedance.

Each notch in a rhinogram represents a constriction inside the nasal cavity.

The first notch represents the nasal valve area. This is infact the minimal cross

sectional area in the normal nasal cavity. The second notch represents the anterior

portion of the inferior / middle turbinate. The third notch represents the area of the

middle and posterior end of middle turbinate. Each notch indicates the site of nasal

airway resistance and is hence a very sensitive indicator for identifying the area

causing nasal block.

Figure showing the Rhinogram. Note the three notches as described above

Figure showing acoustic rhinomanometer

CT volumetry: This imaging modality is very senstitive in measuring nasal cavity

volumes. This imaging modality is highly accurate in measuring the volume of

anterior nasal cavity but its accuracy reduces while measuring the volume of

posterior nasal cavities.

Rhinomanometry:

This investigation involves the functional assessment of airflow inside the nasal

cavity. It involves measurement of transnasal pressure and airflow. Resistance from

each nasal cavity can be compared.

There are two types of rhinomanometry, active and passive rhinomanometry. Active

rhinomanometry involves the generation of nasal airflow and pressure with normal

breathing. Passive rhinomanometry involves the generation of nasal airflow and

pressure from an external source, such as fan or pump which drives air through the

nose.

Active rhinomanometry: can be divided into anterior and posterior methods

according to the siting of the sensor tube. In active anterior rhinomanometry, the

pressure sensing tube is taped to one nasal passage. This method measures resistance

of one nasal cavity at a time and must be repeated on the other side. The total air flow

through the nose is measured with the help of the sensor tube. In active posterior

rhinomanometry, the pressure sensing tube is held within the mouth and it detects the

post nasal pressure. Air flow through each nose can be measured by taping the

opposite nose.

While performing rhinomanometry pressure in the post nasal space can be measured

in three ways:

1. Anterior rhinomanometry involves palcement of a tranducer in the nostril not

being tested. This concept was first introduced by Coutade in 1902. Because there is

no airflow in the non test nose, the pressure at the anterior end of this nostril is

roughly equal to the pressure at the post nasal space. In this method transnasal

pressure differences and nasal airflow can be recorded at the same time. Major draw

back of this method of recording is that it cannot be relied in patients with septal

perforation.

2. Another method of measuring nasal pressure is by peroral method. This

method was popularized by Spiess in 1899. In this method the transducer is placed in

the posterior portion of oropharynx through the mouth. This method accurately

assesses the contribution of enlarged adenoid tissue to the nasal block. The major

problem with this method is that it is poorly tolerated.

3. The third method of measurement of nasal airway is by placing the sensor in

the postnasal space. This is again not very well tolerated by the patient.

Precautions taken while performing rhinomanometry:

a. The use of face mask is desirable than a nasal cannula. The face mask should form

a soft air tight seal and must not effect pull on the cheek.

b. Calibration of the equipment must be performed regularly.

c. Series of readings must be taken as a single reading is unreliable.

Nasometry:

During speech sound is transmitted through both the oral and nasal cavities. Nasal

obstruction causes a reduction in the amount of sound transmitted through the nose.

By measuring the nasal components of speech the patency of the nasal airway can be

assessed. This is known as nasalance. It is the ratio of sound energy from the nasal

and oral passages and can be measured by placing two microphones one over the

nose and the other over the mouth. Infact the measure of nasalance has been proposed

as a useful method of selecting children for adenoidectomy. It is also useful in

measuring the nasal airway patency.

Odisoft rhino:

This new technique converts the frequency of sound generated by airflow into cross

sectional area measurements. This technology was based on the premise that the

sound generated by airflow in the nose has a higher frequency depending on the

turbulence created. This technique was first developed by Serene. The equipment

has a microphone, nasal probe, sound card and a computer. The nasal probe is

connected to a microphone and is placed about 1 cm from the nostril of the patient.

The sound created by breathing is measured by the probe.

Figure showing areas of nasal cavity contributing to normal nasal resistance

Management:

Nasal obstruction due to mucosal congestion can be managed medically by topical / systemic nasal

decongestants. Treatment of acute infections with antibiotics should take precedence over nasal

decongestants.

To decide whether medical / surgical management is preferred mucosal congestion index should be

assessed.

Nasal mucosal congestion is an important determinant in deciding whether the patient needs

medical / surgical therapy. It goes without saying that if the nasal mucosa is thickened due to

mucosal oedema than it would respond better to nasal decongestants, while if the thickening is due

to underlying submucosal fibrosis then it doesn't respond to decongestants and needs to be

surgically removed to improve nasal airway patency. Nasal mucosal compliance cannot be

estimated by CT scans alone.

It has been demonstrated that tissue remodelling which is the repair response of nasal mucosa to

insults is characterised by decrease in vascular density, and an increase in fibrosis causing the nasal

mucosa to thicken irreversibly. This thickened mucosa reduces drug permeability through osmosis

causing a reduction in the effectiveness of the drug.

This measurement helps in identifying mucosal oedema from mucosal thickening due to fibrosis

involving submucosa. This can be measured by performing acoustic rhinomanometry before and

after decongesting the nose with epinephrine. If the nasal mucosal congestion index is large then

medical management is preferred and if the index is small then surgery should be resorted to in the

management of chronic rhinosinusitis. For sake of objectivity congestion index of the nasal mucosa

can be classified as normal, mild, moderate, severe and very severe.

Surgical management of nasal obstruction:

1. Septal correction – if nasal block is attributed to septal deviation / spurs

2. Anatomical abnormalities like concha bullosa should also be corrected surgically

3. Obstruction to nasal valve area as prooved by Cottle's test should be managed surgically.

Procedure:

This procedure can be performed under local anesthesia. Nasal cavity is first packed with ribbon

gauze dipped in 4% xylocaine with 1 in 100,000 units adrenaline. Xylocaine in 1% concentration

mixed with 1 in 100,000 units adrenaline is infiltrated over the prominence formed by the caudal

portion of the upper lateral cartilage. Parallel incisions are made on either side of the caudal portion

of the upper lateral cartilage. The caudal portion of the upper lateral cartilage is exposed after

removing a strip of mucosa with the underlying fibrous tissue. A 2 mm cuff of mucosa along with

overlying fibrous tissue is also removed to prevent redundant tissue formation. About 1-2 mm of the

terminal portion of the upper lateral cartilage should be resected and removed. The wound is closed

with absorbable suture like catgut. This procedure is safe to perform bilaterally also if necessary.

Diagram illustrating surgery in the nasal valve area