Nasopharyngeal Airway Sizes: What the Number Means, How to Measure, and What to Stock

Коротко кажучи: 28 Fr, 7.0 mm, size 7. Each of those is a width. Length is a different number, set by each maker and usually missing from the pack, and it's the one that decides whether a nasopharyngeal airway (NPA) sits where it should. Get close with a nose-to-ear measurement, let the patient's breathing settle it, and buy from a line whose lengths you've seen on paper.

Quick Specs

What do nasopharyngeal airway sizes mean? The number is the diameter, not the length

Nasopharyngeal airway sizes are printed as a diameter. Pick up a pack and you'll see 6.0 or 7.0 (millimeters, internal diameter), or 24 or 28 Fr, sometimes both. French refers to the outside of the tube. Length? Not there. The printed number on an NPA gives the width of the tube, and the length, which decides where the tip ends up, is left off.

Why care? Because the tip has to land in one place. The NPA guideline from the Royal Children's Hospital Melbourne (RCH) says size is picked mostly by length rather than diameter, and the right length puts the tip just above the epiglottis. Width isn't irrelevant (a fat tube bleeds more, a thin one moves less air), but a nasopharyngeal airway with a decent width and the wrong length still won't sit right.

Pull out a kit list or a quote and look at the NPA line. "NPA 28 Fr x 2." "Nasopharyngeal airway, 28 Fr, adult." People search the same way ("nasopharyngeal airway 28 fr"), as if the number were the answer. Width, yes. Whether that supplier's tube reaches far enough in an adult, no idea.

The cost shows up when you compare NPA sizes across suppliers. Two 28 Fr quotes, two lengths, one price comparison that means very little. Leave length off the kit list and the cheapest tube that month is what turns up. Nobody forgets to write the diameter. It gets copied from one order to the next, while the length was never on the page to copy in the first place, so each new supplier fills the gap with its own tube.

So read the size as a width and ask the supplier for the length that goes with it. (Our own size sets and pack contents are on the набір для забезпечення прохідності носоглотки page.) The rest of this page covers why lengths differ, how good the usual sizing rules are, and what to check before an order.

Why two NPAs with the same size can sit at different depths

Two size 7s from two suppliers can be two different tubes, and the pack won't warn you. Lengths vary from maker to maker. A size number from one supplier does not promise the same tube from another.

The right length puts the tip just above the epiglottis. That's the useful spot, under the soft palate, where the tube actually props the airway open. Too short, and the tip parks behind the soft palate or tongue (often the very place that's blocked). Too long, and it can end up in the vallecula, or the patient gags. In the case below about a centimeter made that difference, which is why insertion depth comes down to NPA length far more than to the label.

The case was published in the Journal of Anaesthesiology Clinical Pharmacology in 2020. Two NPAs with the same internal diameter from different makers can differ in length, as in a reported case of 120 mm versus 130 mm. With the first tube a child's airway stayed blocked. The team swapped in a tube with the same internal diameter, 10 mm longer, and the obstruction cleared at once. Their summary: commercially available NPAs differ in length at a given internal diameter, and it varies by manufacturer.

Across sizes the range is wide. RCH lists the lengths of the tubes it stocks, 6.5 cm for its 2.5 mm tube up to 16.5 cm for the 7.5 mm. One hospital's tubes, not a standard (but proof that length per size can be written down). In 2021 a letter in the European Journal of Anaesthesiology put the complaint in its title: "Nonstandardised length of nasopharyngeal airways".

For purchasing, then, the length of a nasopharyngeal airway is a property of the product line. If someone asks you the length of a correctly sized nasopharyngeal airway, the real answer is "depends on the patient, and on whose tube". Get length per size from the maker and stick to one line; staff then practice on the same tube they'll find in the kit.

How accurate are the usual NPA sizing rules?

Not well. The usual rules are the little finger, nostril width, and nose tip to earlobe (or nostril to tragus). When researchers held them up against imaging, finger and nostril didn't match nasal anatomy, and nose-to-ear missed both ways (short in adults, too deep in children). A 2021 literature review in the Journal of Special Operations Medicine found no evidence behind the length guidance in use. That's about all the sizing of nasopharyngeal airway tubes stands on.

The table below shows what each sizing method was tested against, in whom, and what it predicted.

Five studies, one finding: landmarks estimate NPA length, they do not fit it

Each row comes from the cited source. Samples are small, and every sample was collected in an operating room or a scanner, so a single percentage shouldn't carry much weight on its own. The pattern is what matters: no external facial measurement in these studies told anyone reliably where the tip would land.

Adults first. Stoneham looked at 120 anesthetized adults and found 60% of the tubes past the tip of the epiglottis, with another 13% stuck in the vallecula. His nares-to-epiglottis measurements averaged 159 mm for men (SD 12) and 140 mm for women (SD 11), went up with body height, and didn't track the three outside measurements taken around the head and neck. And children? In 92 sedated children, no landmark method predicted NPA position reliably, and plain nostril-to-tragus would have placed the tip too far down in 71.7% of them.

One adult landmark did better. Tseng and colleagues took the optimal length as the bronchoscope's nares-to-epiglottis distance minus 1 cm and compared four facial distances against it; philtrum-to-ear tragus came closest, within 1 cm for most patients. Best of four, in one study. Useful, but nobody should call it accurate.

Limitations

Who was studied: 10, 120, 200 and 92 people, in an MRI scanner, an operating room before surgery, or under sedation for imaging. No field trauma patients. And no study looked at whether a different sizing method changed patient outcomes.

Every one of these studies was run in an operating room or an MRI scanner, and none tested whether a better sizing method changes what happens to patients. BCEHS, RCH and Merck still teach the face measurement, and this page doesn't argue with them. It only suggests treating the result as a guess that you then check.

The number on the tube is a diameter, and the landmark only estimates length. Treat a landmark measurement as a first estimate and check the fit afterwards, at the patient's airway.

How to choose an NPA size for a patient: start, measure with the tube, confirm

For an adult there are three steps, in this order: height, then the tube against the face, then the patient's breathing. That's measuring a nasopharyngeal airway in a way that fits the evidence above (and the short answer if you searched how to measure nasopharyngeal airway length).

Start from height. Stoneham's 1993 data tied the nares-to-epiglottis distance to body height, and a 2005 review, working from endoscopy, made a quick rule out of it. If you stock Portex, the 2005 review's rule of thumb is a size 6 for a woman of average height and a size 7 for a man. Sex didn't change it, and it beat the finger and nostril methods. The 2021 review in the Journal of Special Operations Medicine agrees length should follow height, then points out you can't count on knowing a casualty's height in an emergency. Height gets you a starting size. Nothing more.

Then measure with the real tube. Hold it against the side of the face: tip of the nose to the tragus of the ear in Merck's description, nostril to tragus in BCEHS's, which adds a detail worth drilling (keep the tube in its natural curve and don't straighten it). Use a tube from your own stock. Length per size changes between brands, so measuring with somebody else's tube tells you little. One more wrinkle from the Tseng data: in adults, nostril-to-tragus came out shorter than the optimal insertion length, so the face check tends to under-call length.

Pro Tip

Train the face measurement on the exact product line in your kits. After any change of supplier, re-check length at each size you stock before staff use the new tubes. In the reported case, 10 mm separated a blocked airway from an open one.

Last, confirm by the airway. Merck's procedure: assess ventilation after insertion, and swap sizes if needed. Quieter breathing. The chest rising. A bag-valve mask that suddenly moves air more easily. Those mean the tube is doing its job. Obstruction still there? Possibly too short. Gagging? Possibly too long.

The misread here is one NPA size for every adult. A nasopharyngeal airway size chart sets sizes against height or age, and some charts name a single adult default. Fine as step one. It doesn't replace the other two.

Stocking works the same way. A team kit should carry several sizes from one product line so it can fit people of different heights. A personal kit with room for one tube? Pick the size that suits most of the people carrying it and accept the compromise.

Sizing an NPA for children

Children get their own rule, and the evidence here is more direct (if modest). A 2019 study of 176 MRI scans, newborns to 12-year-olds, concluded that NPA length can be predicted using the nares-tragus distance minus 10 mm. In 2021 another team tried that rule on 92 sedated children under 12 and looked at each tube tip on MRI.

With nostril-to-tragus minus 10 mm, 37.0% of the tubes sat in the optimal position; the MRI projection said 40.2%. The authors' verdict is "least inaccurate", a useful approximation until a better formula turns up. Plain nostril-to-tragus did much worse, and none of the rules in the study removed the need to watch the child breathe during and after insertion.

Common Mistake

Using the adult nose-to-ear distance on a child and forgetting to take 10 mm off. In the 2021 MRI data, plain nostril-to-tragus would have put the tip too deep in 71.7% of children.

Start at minus 10 mm. Watch the airway closely while the tube goes in, as the 2021 authors advise, and where your pediatric protocol says otherwise, follow it.

Which NPA sizes a kit should carry, and where the NPA sits in TCCC 2026

Kits serve groups. Carry a spread of sizes from one product line, and put the NPA where current guidance places it. Several adult sizes from one maker fit more people than one tube, and sticking to the line means the length staff measured in training is the length in the bag. How wide the spread goes depends on who uses it (adults only, or children too); a team or EMS kit and an individual first aid kit (IFAK) won't end up with the same answer.

Asking what size nasopharyngeal airway for first aid kit use? For a personal kit, one tube from the middle of the adult range for whoever carries it. Vehicle and team kits: several. The size sets and pack contents are on our kit page.

Do NPAs still belong in tactical kits? They do. TCCC Guidelines (1 May 2026) list the NPA under respiration, where it is used together with a bag-valve mask. At the airway step of Tactical Field Care an unconscious casualty goes into the recovery position. The NPA comes in under respiration, for impaired ventilation with oxygen saturation stuck below 90% (92% with moderate or severe TBI): consider a properly sized NPA and ventilate with a 1000 ml bag-valve mask (BVM). In MARCH terms that's the R, after massive hemorrhage and airway.

The 2026 TCCC text still calls for a properly sized NPA, so the device remains in the guideline. "Properly sized" quietly assumes somebody has already solved the length problem on this page. Our explainer on Тактична допомога пораненим у бою (TCCC) walks through the full sequence.

NPA or oral airway (OPA)? A kit can carry both. Merck notes that an NPA is better tolerated than an oral airway in patients who still have a gag reflex. Its wording is obtunded patients with intact gag reflexes. An NPA also goes in where an oral airway can't, after oral trauma or with a jaw that won't open.

Two caveats. TCCC is military guidance, and civilian EMS protocols put the NPA in their own sequences, so build civilian kits to whatever your users train to. And the guideline names the device and its step, not how many to carry; the size spread is yours to write into the kit line.

What goes wrong with NPA sizing, and when not to use one

Sizing problems come down to depth. Too long, and the tip can pass the epiglottis or lodge in the vallecula (13% did in the 1993 adult study) or set off gagging; Merck lists gagging, with possible vomiting and aspiration, in conscious patients. Too short, and the upper airway obstruction may still be there. Test airway patency. An easy insertion proves nothing.

Nosebleeds top the list. BCEHS names epistaxis as the most common complication of NPA placement, with higher risk in patients on anticoagulants, and Merck adds sinusitis. Technique matters: Merck ties bleeding to the bevel's pointed end scraping the septum, and both references warn against force (more in the insertion section).

Some patients shouldn't get an NPA at all. These nasopharyngeal airway contraindications come from the guidance:

• A suspected basal skull fracture. Merck lists a suspected cribriform plate (basilar skull) fracture as an absolute contraindication; passage into the cranial vault has been reported, though Merck calls it rare.
• Significant nasal trauma, a relative contraindication in Merck.
• Significant maxillofacial trauma, in BCEHS (particularly Le Fort fractures that include the zygoma).

Facial injury is where the two disagree. BCEHS lists significant maxillofacial trauma; Merck says NPAs can usually be used even with major facial injuries if placement is done with care. Your protocol decides.

The skull-fracture item has a backstory. Back in 2005, a review in the Emergency Medicine Journal made the case that the intracranial-placement fear, as it's taught, traces back to just two single case reports and should be weighed in clinical context. Fair point about the evidence. The guidance hasn't moved, though, and still lists suspected basal skull fracture. So does this page.

In practice: if the patient has a suspected skull base fracture, or significant maxillofacial trauma under a protocol like BCEHS that lists it, an NPA is not the tool. Use the alternative your protocol names. No gag reflex and an oral airway that's tolerated? The NPA may not be first choice either. It's meant for a patient who is breathing, or being ventilated with a bag-valve mask, and still has some airway reflexes.

Some faults are the product's. Too small a flange lets the tube slip into the nostril; a rough bevel makes bleeding more likely. Catch both on a sample before you buy.

How to check NPA samples before a bulk order

Pass or fail a sample lot on checks you can run at the desk. Start with length. It's the easiest to skip and the one that moves the tip. Merck describes the device as flexible tubes with one end flared and the other end beveled, inserted beveled end first; the length, bevel, flange and flexibility checks come from that and from the length problem above. Marking and pack checks are plain incoming inspection.

1. Measure each sample along its curve, flange to tip, and compare it with the supplier's length table. Doesn't match its own table? Fail the lot.
2. Find the size on the tube or pack and handle it for a minute. Still readable? It has to be, because the face measurement and the kit list both depend on grabbing the right size fast.
3. Run a finger over the bevel. Burrs or sharp molding lines will scrape the septum on the way in.
4. Push on the flange. It shouldn't fold into the nostril, and an adjustable flange should stay where you set it.
5. Bend the tube. It should follow the nasal passage and spring back without kinking.
6. Don't open anything yet; just look at the sterile pack. Seal intact? Pack undamaged? Lot and expiry printed? If not, you've got a tube you can't trust and a lot you can't trace.
7. If there's natural rubber anywhere in the tube or the pack, the label should carry the 21 CFR 801.437 statement.

If any of those checks fails on even one sample, hold the order. Measure a second sample of the same size as well; two tubes from one lot that disagree are worth a phone call to the supplier.

The checks have limits. A nonconforming sample, yes, they'll catch that. How a tube behaves in a patient, no. And a sealed pack isn't proof of sterility, so ask which sterilization method the supplier uses and what the pack is validated for.

Bag the failures with the lot number and a note of what failed. When the first delivery lands, run the same checks again (samples show what a supplier can make; deliveries show what it actually ships), and put the pass criteria in the purchase order so nobody argues later about what counts as a fail.

What to request from an NPA supplier for a comparable quote

Quotes that only list French sizes can't be compared, since they leave out the property that decides fit. So every supplier gets the same questions. Put one line at the top of every request: send a length-per-size table, since a French size says nothing about length.

Two quotes that say "28 Fr" and give no length are not quotes for the same tube yet. Ask for the length at every size you plan to stock, then compare price.

— Rusun TacMed product team

Send this list with every request for quotation:

• Length at each internal diameter or French size, measured the same way each time.
• Material (PVC? silicone?) and whether any part contains natural rubber.
• If there's natural rubber, which label statement applies. 21 CFR 801.437 sets the US wording, and latex that contacts people needs a bold caution starting "Caution: This Product Contains Natural Rubber Latex". Then check the artwork.
• Ask for the sterilization method and the dating period. Samples can't show you the first, and the second tells you how long kit stock can sit before rotation.
• Ask about packaging: single or bulk, what's printed on each, whose brand. Single packs keep each tube sterile in a kit; bulk suits training stock.

Send everyone the same specification: sizes, quantity per size, packaging, label. Ask only for "NPA, 28 Fr" and every supplier quotes its own tube. The cheapest wins for the wrong reason, and the length problem turns up with the first delivery.

The decision, in the end, is a product line whose length per size you know, tested on samples and stocked across the sizes your users need. We make NPAs, so we have an interest here; that is why every study and guideline on this page is linked. Our own size sets and pack contents are on the NPA kit sizes page, and you can request a quote with a length table for the sizes you plan to stock.

Inserting an NPA: the short version every user must get right

Inserting nasopharyngeal airway tubes well depends on a few points Merck and BCEHS agree on. Train from your protocol and the product's own instructions; what follows is the short version for whoever runs that training.

• Check that the patient is breathing or being bagged, still has some gag reflex, and has none of the contraindications above.
• Measure as described above, tube in its natural curve.
• Lubricate the outside with water-soluble lubricant and keep it out of the lumen (BCEHS).
• Use the larger nostril, the wider nasal passage, unless an injury rules it out.
• Insert the NPA along the floor of the nose with the bevel facing the septum, and never force it. Straight back, not up toward the eyes.
• If it sticks, twist it a little and try again; still stuck, try the other side.
• Stop when the flange sits at the nostril, and look at the breathing again.

Each point in this NPA insertion list targets one of the failures described earlier, and skipping the reassessment misses a tube of the wrong length. If bleeding starts, BCEHS advises leaving the tube in as long as it isn't blocking the airway.

Поширені запитання

When would you use a nasopharyngeal airway?

Mostly for someone who's breathing on their own but partly blocked (snoring) and still has a gag reflex. That's Merck's main indication: noisy (sonorous) breathing from upper airway obstruction in a spontaneously breathing patient with an intact gag reflex. BCEHS uses it when a patient needs an airway adjunct and can't tolerate an oropharyngeal airway, or one can't be placed (oral trauma, trismus). Merck also says it can help with bag-valve-mask ventilation and is easier to tolerate than an oral airway while the gag reflex is intact. TCCC 2026 puts it under respiration, for a casualty being bagged whose oxygen saturation won't come up. Before any of that, rule out a suspected skull base fracture, and significant maxillofacial trauma if your protocol lists it (BCEHS does).

Чому ми написали цю статтю

Rusun TacMed makes airway adjuncts, NPAs among them. This page is for whoever specifies, buys or trains with them, and it starts from a gap in the paperwork: an NPA quoted as one number, with no length. Our own catalog lists diameter and French size but not length, so we have the same gap to fix. None of this comes from our own testing. Each figure is from the linked studies and guidelines, and the page stops where they stop. Reviewed by Jason.

Send us your size list for a quote

On our quote form, tick Airway Management and choose an estimated quantity. Use the requirements box for the sizes you need, how many of each, and whether you want a length-per-size table sent with the samples. We quote against that. Request an NPA quote →

Related articles

1. Що таке IFAK?: what else goes in the kit around the NPA.

Посилання

1. How do you size a nasopharyngeal airway. Roberts K, Porter K. Resuscitation 56(1):19-23, 2003.
2. The nasopharyngeal airway. Assessment of position by fibreoptic laryngoscopy. Stoneham MD. Anaesthesia 48(7):575-80, 1993.
3. Estimation of nares-to-epiglottis distance for selecting an appropriate nasopharyngeal airway. Tseng WC et al. Medicine 98(10):e14832, 2019.
4. Working with estimation-formulas to predict nasopharyngeal airway insertion depth in children: Looking at magnetic resonance images - A prospective observational study (WEND:LI-Study). Nemeth M et al. Resuscitation 168:95-102, 2021.
5. The nasopharyngeal airway: Estimation of the nares-to-mandible and nares-to-tragus distance in young children to assess current clinical practice. Johnson M et al. Resuscitation 140:50-54, 2019.
6. Studies on the Correct Length of Nasopharyngeal Airways in Adults: A Literature Review. Scheuermann-Poley C, Lieber A. Journal of Special Operations Medicine 21(3):45-50, 2021.
7. The nasopharyngeal airway: dispelling myths and establishing the facts. Roberts K, Whalley H, Bleetman A. Emergency Medicine Journal 22(6):394-6, 2005.
8. Nasopharyngeal airway size selection and its implication in the management of pediatric difficult airway. Thangavel et al. Journal of Anaesthesiology Clinical Pharmacology 36(4):565-6, 2020.
9. The long and short of it: Nonstandardised length of nasopharyngeal airways. Dogra N, Dhanda S. European Journal of Anaesthesiology 38(11):1202-4, 2021.
10. Nasopharyngeal Airway Insertion and Management. The Royal Children's Hospital Melbourne, clinical guideline.
11. How To Insert a Nasopharyngeal Airway. Merck Manual Professional Version.
12. PR07: Nasopharyngeal Airway. BC Emergency Health Services Clinical Practice Guidelines.
13. Tactical Combat Casualty Care (TCCC) Guidelines, 1 May 2026. Committee on Tactical Combat Casualty Care.
14. 21 CFR 801.437, User labeling for devices that contain natural rubber. U.S. Food and Drug Administration, Electronic Code of Federal Regulations.