Jan 14, 2020
It has long been considered that the upper airways – from the nose to the vocal chords – and the lower airways – below the vocal chords – are distinct anatomical and histological entities and fall under two different specialties as regards to treatment. However epidemiologic, pathophysiologic, and clinical evidences revealed the link between upper and lower airways, changing the global view of respiratory diseases.
UAD an old concept coming back in Respiratory Experts’ topics
During the second century, Claudius Galenus identified the effect of the upper airway on the lower airway and defined the nose as a “respiratory instrument” in his work “De usu partium.” Nevertheless, the concept of the upper and lower respiratory passages being a continuum and forming a single unified airway has been highlighted only over the last 10–15 years.(1)
The concept of united airway disease (UAD) is arguing that any disease process that affects the upper airway is likely to affect the lower airway, and vice versa. Therefore, upper and lower airways are considered as a united morphological and interdependent respiratory unit known as the united airway model. (2, 3)
The most important mechanism involved in driving this unified respiratory system is inflammation, and that the development of an acute infection in the upper respiratory tract may be a risk factor for development of infections in other districts. A typical example is the development of pneumonia in the course of influenza.
UAD and respiratory infections
Another example is that over 80% of asthmatics have rhinitis, and 10%–40% of patients with rhinitis have asthma, suggesting the concept of “one airway, one disease”.
In this context, management of rhinitis and asthma must be jointly carried out, leading to better control of both diseases.
With some exceptions, a certain ‘promiscuity’ can be noted regarding the association between pathogens and specific forms of illness, to further testify that it is a unified system.
Indeed, there seems to be a correlation between viral and bacterial infection. Viral infections facilitate
bacterial colonization by modifying the local defense mechanism of the respiratory tract and induce some changes in the cell membrane that facilitate bacteria adhesion. The virus-bacteria interaction is a vicious cycle where the virus opens the door for the bacteria which, in turn, facilitates viral infection.
In a Western context, it is estimated that respiratory infections are responsible for 20% of access to doctor consultation and 75% of antibiotic prescriptions. Amidst the growing concerns about antibiotics resistance, further research into the concept of united airway could lead to fundamental changes in the ways respiratory infections are managed and prevented.
1. Licari A, Castagnoli R, Denicolò CF, Rossini L, Marseglia A and Marseglia GL (2017) The Nose and the Lung: United Airway Disease? Front. Pediatr. 5:44. doi: 10.3389/fped.2017.00044
2. Skoner DP. (2001) Allergic rhinitis: Definition, epidemiology, pathophysiology, detection, and diagnosis. J Allergy Clin Immunol.;108(1 Suppl):S2–8
3.Meltzer EO. (2000) Role for cysteinyl leukotriene receptor antagonist therapy in asthma and their potential role in allergic rhinitis based on the concept of “one linked airway disease” Ann Allergy Asthma Immunol. ;84:176–85.2