The Unified Airway: Do We Fully Appreciate Its Impact in Otolaryngology?

Bradley F. Marple, MD, is Professor and Vice-Chairman of the Department of Otolaryngology-Head and Neck Surgery at University of Texas Southwestern Medical Center in Dallas.

I have found that it is not uncommon during the course of an office visit for a patient to offer an opinion pertaining to the role that nasal troubles play in his or her general health. Specifically, these individuals point out the fact that exacerbations of their chronic rhinosinusitis or allergic rhinitis gives rise to a worsening of asthma symptoms, decreases in exercise tolerance, and need for more frequent use of rescue medications. The coexistence and seeming interdependence of these maladies resonate with the sufferers to the point that when asked, many patients will often happily describe their personal theory of the pathophysiology of this phenomenon. And even though in many instances the explanation may be a little off the scientific mark, I am generally impressed with the consistency of these observations from patient to patient. Truth be known, when the premise of this argument is subjected to current peer-reviewed medical literature, it appears that these patient observations are reasonably close to the current conventional wisdom as it relates to respiratory diseases.

Concept of the Unified Airway

Over the course of the past two decades, the concept of inflammation involving both the upper and lower airways has become increasingly recognized and studied. When examined, asthma, allergy, and rhinosinusitis appear to behave similarly and in conjunction with one another in many cases, suggestive of an integration of the involved areas of the airway. This pattern of similarities has given rise to the concept of the unified airway model, which, simply stated, considers the entire respiratory system to represent a functional unit that consists of the nose, paranasal sinuses, larynx, trachea, and distal lung.1 The broad number of inflammatory diseases that occur within this functional unit present to a variety of specialties, including otolaryngology, pulmonology, primary care, and allergy. Similarly, literature related to this concept is distributed among the literature of each of these specialties.

Initial associations among these diseases were noted due to the concurrence of these disease processes and were later more objectively established by way of epidemiologic studies. The simple coexistence of rhinitis and asthma, as an example, was demonstrated by Corren,2 who noted that nasal symptoms were suffered by approximately 78% of a large group of patients with asthma. In another classic paper, the Finnish Twin Cohort Study,3 more than 11,000 patients were followed longitudinally to assess whether the presence of allergic rhinitis was associated with the development of other respiratory diseases over time. Questionnaires were administered in 1975, 1981, and 1990 and revealed a fourfold increase in asthma reporting at the end of the study in subjects with hay fever over normal control subjects. In 2002, Guerra et al. corroborated these findings after following 1655 patients with allergic rhinitis and 2177 normal controls over a 20-year period. As in the previous study, sufferers of allergic rhinitis were approximately three times more likely to develop asthma than were the controls.4