What is the connection between the nose and the lungs?
December 28, 2020
The nose also has a hard time. Thousands of people try to fix their nose every year because they are not satisfied with its appearance: too long, large, flattened, sharp, wide… And also humpback, snub-nosed, potato or simply crooked. Some extreme athletes even cut off their nose to look like Lord Voldemort or the red Skull from the comics. In short, the attitude to the noses is not the best. Not only do they have claims in aesthetic terms, so they still flow, itch, twang, blush. They make us snore, sneeze, sniff, and make other unpleasant noises. There are times in life when a healthy, properly functioning nose is even an exception to the rule. A three-year-old’s dry nose? You can mark this day in the calendar as a holiday. The nose is a source of constant trouble. Nevertheless, it plays an important role in protecting the front lines in the sensitive contact zone between the external and internal world. This is a kind of airway checkpoint separating two worlds, often hostile to each other, and the Nose behaves uncompromisingly. Like the security services at airports, he calmly confronts the discontent of thousands of passengers who forget that the verification procedure, for all its trouble, is necessary. Would you like people to transfer directly from the car to the plane without any control?
The nose is the vanguard of the Airways. It is a growth with two holes at the end. The nose serves as a bodyguard, doorman, and scout for the lungs. Because the lungs are deaf and blind, it serves as both their eyes and ears, as well as an air conditioner, air filter, and humidifier. The nose and lungs are a strange and unequal pair, in which the little one takes care of the big one.
The nose takes its protective functions seriously and performs them very successfully. In allergic people, for example, it in many cases does not allow allergies to spread to the “lower floors” (in the bronchi) and thereby prevents dangerous allergic asthma. In Germany, allergic rhinitis affects twice as many people as allergic asthma (15% of the population versus 8-9%), and only 40% of patients with allergic rhinitis suffer from asthma at the same time, although both diseases are based on the same Allergy. In other words, a respiratory Allergy causes first complaints at the place of first contact — in the nose. For many patients, this is all it is-unpleasant, of course, but in most cases it is not dangerous. And only when the nose does not cope with its functions, the Allergy spreads to the lower respiratory tract, that is, “goes down a floor below”. The consequence is allergic asthma, which has much more serious consequences.
“Changing floors” is not only characteristic of hay fever and asthma. Such voyages can also be made by an ordinary runny nose with a cold. Have you noticed that the common cold almost always develops according to the same scenario? Why is this happening? Viruses of colds attack the same targets in the nose and bronchi — the epithelial cells of the mucous membrane. And yet the disease does not spread in a random direction, and certainly not from the bottom up, it always begins in the nose and sometimes in the throat. In most cases, this is where it ends. In less than half of all colds, symptoms (such as coughing) also appear in the lower respiratory tract. Thus, the runny nose protects the lower respiratory tract from the spread of pathogens. And only when the primary protective mechanisms of the nose give up under the onslaught of the disease, trouble begins: after 3-5 days, bronchitis is added to the runny nose, a sign of which at first is a cough, followed by sputum. Bronchitis is the result of the passage of cold viruses to the “lower floors” through the defensive orders in the nose. This explains the fact that patients with damage to the nasal mucosa (for example, as a result of chronic diseases) are much more likely to experience symptoms of bronchitis with a cold-the filter no longer works.
The phenomenon of “changing floors” also plays a role in chronic respiratory diseases. The cause of persistent cough and chronic bronchitis is often inflammation of the paranasal sinuses. At night, nasal secretions flow into the pharyngeal cavity, into the glottis, and then into the bronchi, where they cause coughing and asthmatic symptoms. Benign tumors of the nasal mucosa (polyps) can also make it difficult to breathe through the nose and provoke frequent bronchial infections, which in the long run can lead to asthma.
What is the basis of these relationships? How to explain the susceptibility of the upper and lower respiratory tract to the same diseases? And if infections “travel from floor to floor”, then how does the “Elevator”function? To understand, you need to pay attention to three important aspects.
The General plan of construction
The nose and lower respiratory tract have little in common externally, but their interior was handled by the same specialist! The structure of the mucous membranes of the nose and bronchi is so similar that when microscopically examined, they can hardly be distinguished, the difference is visible only in the deep layers of the mucosa. Where the ring muscles around the bronchi are located in the lower respiratory tract, in the nose we observe a dense interweaving of blood vessels — the so-called cavernous body, which, swollen with a cold, can greatly complicate breathing. The cleansing mechanisms of the upper and lower respiratory tracts are also similar. The removal of foreign particles is carried out by the cilia of the ciliated epithelium and the glands that produce mucus. At the same time, both the upper and lower respiratory tracts demonstrate that their structure was based on the same plan, hereditary diseases of both transport mechanisms affect both the upper and lower respiratory tracts equally. In particular, in congenital cystic fibrosis, extremely viscous mucus, typical of this disease, is observed both in the bronchi and in the nose. Hereditary diseases of the ciliary epithelium, such as primary ciliary dyskinesia, negatively affect the cleansing functions of the mucous membrane of both the nose and bronchi.
Common communication network
The nose is the first to notice that something is wrong in the air. Its early warning system either prevents harmful or irritating substances from entering the lungs, or gives the lungs the opportunity to take their own protective measures in a timely manner. To do this, the carrier uses direct and indirect communication channels, which can be compared to a cable telephone line or a wireless WhatsApp. So, when irritation of the nose sinobronchial reflex causes constriction of the bronchi. How does it work? The olfactory cells of the nose are connected to the nervous system of the lower respiratory tract through the branches of the trigeminal nerve. Harmful substances contained in the air irritate the trigeminal nerve, which causes a contraction of the bronchi. Through this direct communication channel, other defensive reflexes are simultaneously initiated, causing sneezing, tears, and coughing. All of them serve one main purpose: at all costs to prevent harmful substances, poisons, microbes or parasites from entering the lower respiratory tract and through them into the body tissues. But this complex defense mechanism can itself become a risk factor. The consequences of uncontrolled bronchial spasm for a person can be more dangerous than the harmful effects of irritating substances contained in the air. In extreme cases, this reflex also causes a spasm of the glottis.
As for the indirect mediated communication channel (WhatsApp), the connection between the nose and lungs is carried out through it through the blood. Getting pollen of plants on the nasal mucosa of an allergic person leads not only to rapid allergic inflammation of the nose, which is expressed in sneezing, itching and runny nose, but sometimes to inflammation of the bronchi, which did not come into contact with the pathogen directly. How is this possible? Answer: between the nose and lungs, communication occurs with the help of signaling substances (cytokines) contained in the blood. In our example, they appear due to an allergic inflammatory reaction in the nose and through the blood vessels reach the lower respiratory tract, where they cause a similar inflammatory reaction. A similar” transmission ” of the inflammatory reaction is possible with a cold runny nose. In some patients, the lower respiratory tract becomes inflamed even in the absence of direct contact with viruses. In this case, the nose also produces signaling substances that cause swelling of the bronchial mucosa and accumulation of mucus in them. This side reaction of the bronchi to a runny nose usually does not cause any problems, but performs an important task. Thanks to the early warning system, the protective systems of the lungs are activated in advance, and, as a rule, this is justified. However, in patients suffering from chronic lung diseases, such data transmission via WhatsApp between the nose and lungs has its drawbacks: as a result, coughing can develop and even suffocation can occur. In fact, many severe asthma attacks are caused by common cold infections in the nose even before the virus reaches the lower respiratory tract! Thus, the early warning system turns into an overreaction, which carries a danger. The lungs want to shout to the nose: “Shut up and turn off your smartphone!»
Nose as an air conditioner
The inner surface of the lungs is huge compared to the nose, so it is in danger of drying out. One of the tasks of the nose is to moisten the inhaled air and warm it to body temperature. To do this, it uses two effective mechanisms. First, the mucous membrane of the sinuses has a folded surface and, therefore, a large area. Since it is very well supplied with blood, the temperature of the blood optimally warms the incoming air. Secondly, 45 thousand glands of the nasal mucosa produce more than half a liter of mucus every day, which additionally moisturizes the air. The moisturizing capacity of the nose is huge and can be increased several times if necessary. For example, during a long flight, due to too dry air in the cabin, you can lose up to two liters of liquid! The moisturizing ability of the nose is important for air filtration. Thanks to it, substances that are soluble in water are almost completely captured and disinfected in the nose. This process is complemented by mechanical filtration with nasal shells, which reliably capture solid particles and pathogens of many diseases. Only fine dust from particles with a diameter of less than ten micrometers (that is, millionths of a meter) penetrates through the nose, and this makes it particularly dangerous for the lungs.
Most people don’t see the difference between breathing through the mouth and breathing through the nose. In fact, it is huge! If the nose performs its functions, then only warmed, moistened and pre-filtered air enters the lower respiratory tract. It is very important that babies at birth breathe only through the nose and only in the most extreme case, if the nose is blocked, switch to breathing through the mouth. But the fact that we, adults, seem to take for granted, kids brings great difficulties. They don’t have enough air, and they panic. How important nasal breathing is for the lungs, we notice only when the nose temporarily ceases to perform its functions as an air conditioner. This happens, for example, with increased physical activity, when it becomes impossible to breathe only through the nose. Have you ever seen an athlete in a triathlon finish with his mouth closed? Professional athletes often experience the effects of oral breathing. Those who are engaged in disciplines that require special endurance, suffer from asthma two to three times more often than ordinary people, and in classic winter sports even more. The often expressed suspicion that the diagnosis of “asthma” for many athletes serves only as a pretext for the use of drugs that increase endurance, should not be spread indiscriminately to everyone. Try it yourself at minus 20 degrees and 10 percent humidity to run on skis with a full load! At a breathing rate of 40-50 breaths per minute, most will have a whistle in the bronchi.
The nose as an air conditioner, along with harmful substances, also filters and neutralizes dangerous microorganisms. But if it does not cope with the filtering functions or even falls out of the supply of air to the lungs (for example, during intubation through a tube), then soon many pathogens will settle in the lower respiratory tract, resulting in bronchitis or pneumonia.
Thus, it becomes clear that otolaryngologists and pulmonologists do not in vain consider the upper and lower respiratory tract as a single system. Such an approach is necessary for the successful treatment of chronic respiratory diseases. The seeds of many diseases of the bronchi are laid in the soil in the nose. Whether they will rise depends on timely and consistent measures to prevent the transfer of the disease “from floor to floor”. Cough and chronic bronchitis, for example, are best treated together with chronic inflammation of the sinuses. The nose and bronchi cannot be separated.