While the size of the visible opening, known as the external nares, may seem like the determining factor for airflow, the mechanics of nasal breathing are far more intricate than simple external appearance suggests. Effective nasal airflow depends on a complex internal architecture that filters, warms, and humidifies the air before it reaches the lungs. This process involves multiple anatomical structures deeper inside the nose that are much more influential than the size of the nostril opening itself.
The Critical Difference Between External Nares and Internal Airflow
The external nares, the visible nostrils, serve as the entryway but offer relatively low resistance to the flow of air into the nasal cavity. The primary determinant of airflow resistance is a much narrower passage located approximately 1.5 to 2 centimeters inside the nose, known as the nasal valve. This internal nasal valve is the narrowest point in the entire upper airway, often described as an hourglass constriction.
This critical area is formed by the juncture of the septum, the upper lateral cartilage, and the anterior head of the inferior turbinate. Because of its small cross-sectional area, the nasal valve is responsible for the majority of the total airflow resistance in the nose. Therefore, a slight narrowing in this internal area can significantly restrict breathing, regardless of how wide the external nostrils appear.
When External Structure or Nasal Alar Collapse Restrict Breathing
There are specific circumstances where the structure immediately surrounding the nostrils directly impairs breathing. This occurs primarily with a condition called nasal alar collapse, which is a dynamic issue rather than a static size problem. The nasal ala refers to the soft, cartilaginous tissue forming the side wall of the nostril.
During a deep inhalation, the rapidly moving air creates a negative pressure inside the nostril, a phenomenon related to the Bernoulli principle. If the nasal alar cartilages are weak or lack sufficient structural support, this negative pressure can cause the nostril wall to visibly “suck in” or collapse inward, momentarily obstructing the airflow. This dynamic collapse is often most noticeable during periods of increased physical exertion when a person is breathing heavily.
A weaker external structure or a naturally weak nasal valve makes a person more susceptible to this dynamic obstruction. For these individuals, the issue is the inability of the surrounding cartilage to withstand the forces of rapid inspiration, not the size of the nostril at rest.
Common Internal Causes of Nasal Airflow Obstruction
The most frequent causes of chronic, restricted nasal breathing are structural issues located deeper within the nasal cavity, completely independent of nostril size. A deviated septum occurs when the thin wall of bone and cartilage separating the left and right nasal passages is significantly displaced to one side. This misalignment can be present from birth or result from an injury, and it drastically reduces the volume of the airway on the affected side.
Another common cause is turbinate hypertrophy, which is the swelling of the turbinates, the shelf-like structures along the side walls of the nasal passages. Turbinates are lined with a highly vascular mucous membrane that functions to warm and humidify the air. They can easily become enlarged due to allergies, chronic inflammation, or infection. When the inferior turbinates swell, they can press against the nasal septum, obstructing the flow of air.
Both a deviated septum and turbinate enlargement disrupt the normal laminar, or smooth, flow of air inside the nose, causing it to become turbulent. This turbulent airflow can lead to a sensation of chronic congestion and often worsens at night due to positional changes that increase blood flow to the nasal tissues.
Diagnostic Tools and Treatment Options for Restricted Nasal Breathing
Diagnosis of restricted nasal breathing begins with a detailed physical examination and a patient history to understand the nature of the obstruction. Physicians often perform anterior rhinoscopy or nasendoscopy, using a small camera to directly visualize the nasal passages and identify issues like a deviated septum or swollen turbinates. Imaging tests, such as a CT scan, may be used to obtain a detailed view of the underlying bony and cartilaginous structures.
Functional tests, like rhinomanometry or acoustic rhinometry, objectively measure nasal airflow resistance and the physical cross-sectional area of the nasal passage. These tools help pinpoint the exact location and severity of the blockage, which is crucial for determining the correct treatment path.
For dynamic nasal alar collapse, non-surgical options include external nasal strips or internal dilators that mechanically hold the nostril open. Structural issues often require surgical intervention, such as a septoplasty to straighten a deviated septum or a turbinate reduction procedure to shrink enlarged turbinates. For nasal valve collapse, surgeons may perform procedures like alar batten grafting, where cartilage is used to reinforce the weakened side walls of the nose and prevent collapse during inspiration.