What is the unified airway?
The close relationship between the upper (nose and sinuses) and lower (lungs) airways has been widely noted for decades. Patients with asthma and other lung diseases have been observed to also be afflicted with disorders of the nose and sinuses. We know that patients with asthma are much more likely to have chronic sinusitis than those without it. We also know that patients with sinusitis are much more likely to have it than those without sinusitis. More recently, scientific researchers have begun to uncover the details of this inter-relationship on a molecular level. This interrelationship of airways has been termed the “Unified Airway.”
When should I suspect that I might have asthma?
Asthma is characterized by hyper-responsiveness of the lower airway. Patients with asthma typically complain of some combination of coughing, wheezing, chest tightness, dyspnea (difficult or painful breathing), and increased mucous production. Typically these signs and symptoms of airway obstruction are reversible. Patients can experience it on a wide ranging continuum. For some, asthma “attacks” are infrequent and mild. For others, symptoms can seem continuous and may land patients in and out of the hospital on a regular basis.
In many patients, cough may be the only symptom of asthma. This may make diagnosis particularly challenging, since cough may be a manifestation of a panoply of airway problems ranging from the common cold, acid reflux, and asthma to pneumonia, aspiration, and tuberculosis. Wheezing is perhaps the most “specific” symptom of an adult patient in the general population with asthma. This means that most adult patients who wheeze, have it. Dyspnea, or shortness of breath, is often described as chest-tightness or a breathless sensation. Ironically, it is very difficult to correlate a patient’s subjective sensation of shortness of breath with an objective measurement of airway obstruction. What seems to impact this sensation most is the percentage change in a patient’s airway function rather than the absolute value of lung function. While it does remain difficult to qualify, the sensation of dyspnea is common among patients with asthma, and should not be ignored.
What are some commonalities between asthma and sinusitis?
Mucous hyper-secretion is perhaps one of the areas of greatest overlap between patients with sinusitis and asthma. A sensation of “too much mucous” is shared by patients with asthmatic symptoms, rhinosinusits (post nasal drainage), and laryngopharyngeal acid reflux. In many asthmatics, attacks are characterized by overwhelming quantities of mucous. In fact, some seem to have significant increases in the number of mucous-producing (goblet) cells, and the characteristics of their mucous is much thicker and difficult to manage. As with many of the other symptoms of patients with it, careful evaluation must be performed to rule out other causes of thick, profuse mucous including cystic fibrosis, immotile cilia syndromes, and other mechanical deformities.
How is asthma diagnosed?
Patients suspected of having it should have a thorough evaluation by a pulmonologist (lung specialist). In addition to taking a thorough history and performing a complete physical examination, pulmonologists have many adjunctive tools at their disposal for the diagnosis of asthma. Pulmonary function testing is an invaluable tool in the characterization of a patient’s lung function. While several methods exist for evaluating pulmonary function, spirometry is one of the most widely available. With simple inhalation and exhalation into a hand-held device, measurements can be obtained which characterize a patient’s lung function is detail.
Forced expiratory volume1 (FEV1) is the volume of air that a patient can expire in 1 second of maximal effort. Forced vital capacity (FVC) is the total volume of air that can be expired after a complete inhalation. In patients with normal lung function, FEV1 is approximately 80% of the FVC. In patients with asthma (and other obstructive airway diseases) there is a decrease in the FEV1/FVC ratio. These measurements can also be used to qualify a patient’s asthma. For instance, an FEV1 70-85% of the predicted value (based on normative values) characterizes mild asthma. An FEV1 60-69% of the predicted value characterizes moderate asthma, and so on. It is notable that this severity system for asthma allows for regular monitoring of the progression of a patient’s disease, as well as his or her responsiveness to medical regimens.
It is notable for its reversibility. Increase in FEV1 by 12% or more after administration of a bronchodilator supports a diagnosis of asthma. Similarly, airway obstruction can be stimulated in patients with asthma with the administration of provocative agents such as Methacholine. This “bronchial challenge” may also be used to confirm a diagnosis suspected by a positive response to a short acting bronchodilator.
There are many other tools that a pulmonologist has to diagnose and evaluate patients showing signs of these symptoms. Clinical judgment will often direct a pulmonologist toward one test or another in his or her quest for an appropriate diagnosis.
How is asthma treated?
Management requires individualized treatment plans, as every patient’s symptoms impact their lives in different ways. Moreover, the severity of symptoms may vary based on season, allergies, work environment, stress, and other factors. It is for this reason that patients must have a working relationship with the physician helping them to manage their symptoms.
Patients with asthma should be very proactive in exerting control over their environment where possible. Environmental irritants, cigarette smoke, viral infections, molds, and dust-mites can all exacerbate it and lower the threshold for asthma attacks. Overlapping illnesses — acid reflux, sinusitis, inhalant allergies, allergic rhinitis — should also be tightly controlled if possible.
There are several medications available for the management of asthma. Deciding on a specific regimen should be performed in careful consultation with a patient’s physician.
Would you tell me more about the relationship between asthma and sinusitis?
For several years now, practitioners have noted a link between patients who have it and those who have sinusitis. As noted above, patients with asthma are more likely to have sinusitis than other members of the general population, and patients with sinusitis are more likely to have asthma than other members of the general population. Specifically, the prevalence of asthmatic symptoms in patients with sinusitis is 20% compared to around 6% in the general population. The prevalence of nasal and sinus symptoms in patients with asthma is as high as 85 to 90%.
This clinical and epidemiological observation is now supported on a molecular and a histological level. The “unified airway” concept has demonstrated how the upper and lower airways are inextricably linked. Inflammation in the upper airway (nose and sinuses) may lower the threshold for inflammation in the lower airway (lungs and bronchial tree), and vice-versa. Some have suggested the presence of a “nasobronchial reflex” and a “pharyngobronchial reflex” as a physiological link between the upper and lower airways. In this “nasobronchial reflex,” when the nerves of the nasal and sinus passages are irritated, a reflex mechanism activates the parasympathetic nervous system and leads to bronchoconstriction. In the “pharyngobronchial reflex,” mucous that drains from the sinus and irritates the pharynx (back of the throat) stimulates a reflex mechanism that activates an inflammatory pathway in the bronchial tree. While these mechanisms are no longer as widely believed to be the definitive link between the upper and lower airways, they do provide an intellectual framework in which to begin to understand how these 2 seemingly distinct systems can interact.
It is now believed that the upper and lower airways are connected by systemic inflammatory mediators. Stimulation of the nasal passage, for instance, may lead to an inflammatory reaction both in the nose and sinuses, as well as the lungs. Researchers have begun to unlock the complex web of molecular pathways that link these 2 systems. It has been discovered that the inflammatory cells and mediators that are most prevalent in the nose and sinuses of patients with sinusitis are also quite evident in the lungs of patients with asthma. This is supported by similarities in the lining of these distinct organ systems and helps to explain similarities in inflammatory function.
How does treating my sinusitis affect my asthma?
If asthma and sinusitis are related entities it follows that improved management of one disease might lead to improvements in the other disease. There is, in fact, a fairly abundant amount of data to support this idea. Several studies have demonstrated that improvement in patients’ sinus disease may lead to improvement in the lung function of patients with asthma. Other studies have shown that sinus surgery in patients with asthma and sinusitis, and whose sinus disease has not improved with medical management, often leads to improvement in lung function of these patients. These patients with asthma who have undergone sinus surgery have, in several studies, been documented to require decreased amounts of medication to control their asthma.