A nasopharyngeal airway (NPA), often called a nasal trumpet, is a soft, flexible tube inserted through the nose to secure an open airway. The NPA prevents the tongue or other soft tissues of the upper airway from collapsing and obstructing breathing in a patient with reduced consciousness. Correct sizing of this device is mandatory for it to work effectively, as an improperly sized airway can cause harm or fail to maintain a clear passage for airflow.
Indications for Use and Initial Assessment
The primary purpose of the NPA is to maintain airway patency, particularly in semi-conscious or unconscious patients who still retain a gag reflex. Unlike the oropharyngeal airway (OPA), the NPA is tolerated by patients with an intact gag reflex because it bypasses the back of the throat. This makes the NPA the preferred adjunct when a patient’s mouth is difficult to open, such as in cases of jaw clenching (trismus) or oral and maxillofacial trauma.
Before sizing or insertion, a rapid initial assessment of the patient’s airway is necessary. The clinician must confirm the patient requires an airway adjunct and that the nasal passage is the most appropriate route. Checking the nostrils for clear patency and looking for signs of obstruction, such as severe septal deviation or nasal polyps, is an important initial step. This assessment identifies any immediate contraindications that would prevent safe use.
Practical Measurement for Correct Length
Determining the correct length of the nasopharyngeal airway relies on external anatomical landmarks. The standard technique involves measuring the distance from the tip of the patient’s nose (the naris) to the tragus of the ear. This approximates the distance from the nostril to the epiglottis, ensuring the tube tip rests just above the larynx without entering the esophagus.
When measuring, the NPA device is held against the side of the face, following the natural curve of the airway. Do not straighten the flexible tube during this process, as this results in selecting a length that is too long. The goal is for the flared end of the NPA to rest against the nostril while the distal tip sits appropriately in the pharynx.
Selecting an NPA that is too short renders the device ineffective, failing to maintain a clear passage. If the device is too long, the tip may descend into the esophagus or stimulate the posterior pharynx. This can provoke the gag reflex and potentially lead to vomiting and aspiration.
Selecting the Appropriate Diameter Size
The diameter of the nasopharyngeal airway is determined independently of its length and is standardized using the French catheter scale (Fr). The diameter dictates how much air can flow through the tube and how easily it will pass through the nasal passage.
A general guide for selecting the diameter is to choose a size that approximates the diameter of the patient’s smallest nostril or the width of the patient’s little finger. The aim is to select the largest possible diameter that can be inserted comfortably without excessive force, maximizing airflow while minimizing mucosal trauma. Forcing a device that is too wide can cause significant injury to the delicate nasal turbinates, leading to bleeding (epistaxis).
The most common NPA sizes for adult patients typically range from 28 to 32 French (6.5 to 7.5 millimeters inner diameter). Adult female patients often use 28-30 Fr, while adult male patients commonly require 30-32 Fr. Pediatric sizes are significantly smaller, starting as low as 12 French.
Critical Safety Check: When Not to Insert
Before insertion, a thorough safety check for specific contraindications is mandatory, as these conditions override the need for the device. The most serious contraindication is the suspicion of a basilar skull fracture (BSF) or severe mid-face trauma. The cribriform plate, which separates the nasal cavity from the brain, may be fractured in these injuries.
Inserting an NPA with a suspected BSF risks the tube passing through the fracture site and entering the cranial cavity, potentially causing catastrophic brain injury or infection. Any suspicion of severe facial trauma should prompt the use of an alternative airway management strategy.
Clinical signs that suggest a BSF include:
- Bruising around the eyes (raccoon eyes).
- Bruising behind the ear (Battle’s sign).
- Leakage of cerebrospinal fluid (CSF) from the nose.
- Leakage of cerebrospinal fluid (CSF) from the ears.
Other conditions prohibit the safe use of an NPA, including severe nasal obstruction, marked septal deviation, or active, uncontrolled nosebleeds. Insertion in these cases can cause excessive bleeding, which may compromise the airway or make the device ineffective. If an NPA cannot be safely inserted, airway management must rely on other techniques, such as an oropharyngeal airway or a more advanced method.