Here we try to answer some questions regarding Airway Stenosis by explaining what airway stenosis is and what kind of treatments are available.
Airway Stenosis is a condition where the windpipe becomes narrower or is constricted. ‘Airway’ is another word for windpipe. ‘Stenosis’ means a narrowing of a passage or opening.
Our breathing system is called the ‘respiratory system’. When you breathe in through your nose or mouth, air travels down your throat (pharynx) and through the voice box (larynx). Air then travels through the largest airway, the windpipe (trachea). The windpipe has springy hoops of a tissue called cartilage in it, which keeps it open while you breathe. The windpipe branches into two smaller airways called the bronchi, which lead to the two lungs.
The entrance to the voice box (larynx) is covered by a small flap of tissue called the epiglottis, which automatically closes when we swallow to stop food or drink from entering the airways. In the voice box, there are two vocal cords (or vocal folds), with a space between them, which is called the glottis. If you have a sub-glottal stenosis, this means that the narrowing in your windpipe is below the glottis, so it is below your vocal cords. Supra-glottic means above the glottis, so if you have a supraglottic stenosis, it is higher up, above the larynx.
Some people with an airway stenosis don’t have any symptoms. Other people can have one or more of the following symptoms:
- Shortness of breath
- Difficult or laboured breathing (dyspnoea)
- A bluish colour in the skin or mucous membranes such as in the mouth or nose (cyanosis) frequent inflammation in the lungs (pneumonitis)
- A noise that can be heard when someone is breathing if their windpipe or voice box has an obstruction in it that is louder and more harsh noise than a wheeze (stridor)
These symptoms aren’t only seen in airway stenosis, and they are found in several other more common types of problems with the respiratory system. Because of this, it is often initially misdiagnosed as asthma or bronchitis. You may also feel generally unwell and tired because of your airway stenosis.
When a airway stenosis is suspected there are several different tests that can be carried out. These include:
- X-ray of the chest and windpipe
- MRI scans (magnetic resonance imaging)
- Endoscopy. An endoscope is an instrument used to look inside the body. It is usually a small tube with a light at the end, with an optical system or miniature video so that the doctor can see an image from inside the body
- Laryngoscopy – a type of endoscope used for looking at the larynx
- Bronchoscopy – a type of endoscope used for looking at the bronchi
Doctors need to be able to see the blockage from above and below, rather than just looking at a person straight on. This is because a airway stenosis is like a thin disk sitting across the windpipe, leaving a small hole in the middle for air to pass through. Imagine a Polo mint sitting in a tube. It would just look like a thin line from the front, but if you looked at it from above, you’d see that there was something blocking the tube, with only a small hole in the middle. This is why the endoscopy tests are so useful for looking at an airway stenosis.
There are several different types of airway stenosis. These can be divided in to stenoses conditions that are present from birth (congenital), and acquired conditions, which have developed later in life. Conditions where airway stenosis can occur include:
Conditions as a result of treatments (‘iatrogenic’ conditions)
- Endotracheal intubation
- Past surgery
Conditions present from birth (‘congenital’ conditions)
- Pulmonary artery sling
External injury (penetrating or blunt)
- Wegener’s granulomatosis
Bacteria and bacterial conditions
- Mycobacterium tuberculosis
The most common cause of airway stenosis is injury during intubation. About 90% of subglottal stenosis in both children and adults are caused by ‘endotracheal intubation’, which is where a tube has been placed in the windpipe to help with breathing (sometimes we call this being on a ventilator, or ‘on life support’). Intubation can cause injury because of pressure that the tube places on the cartilage tissue either in the voice box or in the windpipe. Pressure and/or motion of the tube against the cartilage may cause loss of blood flow to these areas (ischemia) and some of the cells in the surrounding tissue can die (necrosis). Scar tissue growing in these damaged areas can become a stenosis.
In the past, airway stenosis after intubation was very common, as it happened in about 20% of patients. However, this has improved dramatically now that a new method of intubation is used, where a cuff is inflated in the larynx or trachea to provide a cushioned seal to help prevent injury. It is now estimated that about 1% of people develop an airway stenosis after intubation.
The duration of intubation is an important factor in the development of stenosis. Severe injury can be caused after 17 hours, but it might occur even sooner. The risk of injury to the larynx and trachea increases dramatically after 7 to 10 days of intubation. The size of the tube used is also important. Generally speaking, tubes should be no larger than 7-8 mm in internal diameter for adult males, and 6-7 mm for adult females, and the size of the tube needed should be adjusted according to the patient’s height.
Injury during intubation is by far the most common cause of acquired airway stenosis, and the other causes listed above are relatively rare. Congenital airway stenosis is also relatively rare, and most serious cases are diagnosed during childhood.
To see how an airway stenosis affects people’s breathing, try out this simple experiment. Simply cut out some small holes in a piece of cardboard that are about 2mm, 4mm, 6mm, 10mm and 12mm across (i.e. in diameter). Place your lips firmly against the card, and blow out as hard as you can through the card. Start by using the 4mm hole, and note the rushing sound the air makes. This sound is called stridor when heard inside the body’s airways.
Now start with the largest hole, and breathe out sharply through the card. If you don’t feel any resistance, then move to the next hole. When you feel even slight resistance – you have the result! The diameter of the hole you are blowing through is about the same as the size of your stenosis.
If you like experiments, try this about a week before and about a week after your treatment. You will be amazed by the difference after lazer surgery or dilatation. People without a stenosis usually feel resistance with the 8mm or 10mm holes, but if you have a stenosis, you might need to go down to the smaller holes to feel resistance. You can also try this experiment out with friends or family if you like; it can be really useful in giving them an idea of what you’re going through.
You can also find your stenosis using a cheap stethoscope. Breathe in and out sharply. Place the stethoscope at various points along your windpipe. You will soon come to an area of loud stridor. That is where the blockage is. The stridor will usually decrease or even more or less disappear after surgery.
Copyright Dr Michael Buck.
This information was last updated on 09/11/13. Check out our sources used.