These are the ETT numbers you will get asked on clinicals, on the floor, and eventually at 0300 with a room full of people watching. Learn them cold. This is a study reference, not medical advice — your institution’s protocol and the patient in front of you always win.
Sizing
- Average adult male: 7.5–8.0 mm ID (7.5 is the workhorse answer).
- Average adult female: 7.0–7.5 mm ID.
- Bigger isn’t better for the patient in front of you — it’s better for bronchoscopy access and secretion clearance. Know why before you defend it.
Depth: the 21/23 rule
21 cm at the lips for women, 23 cm for men is the classic starting point for oral intubation. It’s a starting point, not a landing zone — confirm with auscultation and CXR. The tip should sit roughly 3–5 cm above the carina, and remember it moves with head position: flexion advances the tube, extension withdraws it.
Cuff pressure
20–30 cmH2O. Below 20 risks aspiration and leak; above 30 starts choking tracheal mucosal perfusion. Measure it with a manometer — the pilot balloon pinch test is a habit, not a measurement.
Confirming placement
- Waveform capnography — EtCO2 across at least 5 breaths. Waveform first. A colorimetric device is a backup, not the standard.
- Bilateral breath sounds, and listen over the epigastrium.
- Chest X-ray for tip position.
If the waveform is flat and the tube “looked good going in,” the waveform is right and the ego is wrong. Reposition.
The Murphy eye question
The side hole near the tip, opposite the bevel. It exists so the tube can still ventilate if the main opening occludes against the tracheal wall or with secretions. Instructors love this one.
This entry pairs with the FM-3RT lockscreen series — the same reference art that lives on the NIGHT OPS line of shirts. Built for the ones learning to own the airway. Field issue here.