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Supraglottic Airways — LMA Types
TEXTAirway I · 9 min read
Six LMA variants solve different problems. Second-gen with drainage port is the modern default.
After this lesson you can
4 min read8 sections- Distinguish 1st vs 2nd generation SGAs and indication for each.
- Select SGA size by patient weight and seal-pressure target.
- Recognize contraindications and limits of SGA use.
- Use the SGA as a rescue device in the ASA difficult-airway algorithm.
LMA Classic — the original
Silicone, reusable up to 40 times after autoclaving.
Inflatable cuff sits at the hypopharynx, sealing the glottic inlet.
No gastric drainage channel.
Cuff pressure target ≤60 cmH₂O — over-inflation causes mucosal ischemia, sore throat, nerve injury.
Reliable for routine OR cases in fasted, non-obese, non-pregnant patients.
Largely supplanted by second-generation designs (Supreme, ProSeal, iGel) which offer better seal pressures + gastric drainage.
Still produced and used in cost-constrained settings.
LMA Supreme + ProSeal — 2nd generation
Higher seal pressures (~30 cmH₂O for ProSeal/Supreme vs ~20 for Classic) — allows positive-pressure ventilation up to that limit.
- disposable PVC
- single-use
- semi-rigid with curve that aids insertion
- silicone
- reusable
- autoclavable
- more expensive per use but cheaper long-term
The gastric drain provides EARLY WARNING if regurgitation occurs — gastric content vents externally rather than aspirating.
Modern default for elective OR LMA use.
iGel — gel cuff, no inflation
No cuff pressure to monitor or adjust.
Built-in gastric drain port (second-generation).
Most popular LMA in many modern ORs — fast insertion, no inflation step, lower mucosal pressure than inflatable cuffs, single-use disposable.
Sizes 1-5 by weight.
Some operators find seal slightly less reliable than ProSeal in obese patients, but modern comparative data show essentially equivalent performance in most populations.
Lower cost than reusable silicone after single-use disposal factored in.
Intubating LMA (Fastrach + AIR-Q)
LMA Fastrach can accept up to an 8.0 cuffed ETT blindly or under fiberoptic guidance.
AIR-Q is a similar concept with a removable connector that simplifies tube passage.
Used as a DIFFICULT-AIRWAY RESCUE (Plan B in many algorithms) and as a planned intubation conduit when direct or video laryngoscopy fails.
Largely supplanted by VL in elective settings, but still present on difficult-airway carts at most institutions.
Pairs with the Aintree exchange catheter + fiberoptic scope for guided ETT placement.
Insertion technique + troubleshooting
Position: head 'sniffing' for adults, neutral for peds.
Open mouth wide, advance device along the hard palate posteriorly until resistance felt at the hypopharynx, then inflate cuff to recommended volume.
Confirm seat by chest rise + ETCO2 waveform + bilateral breath sounds + leak check at 20 cmH₂O.
- tip folds back (re-insert with deflated cuff under direct vision or with finger guidance)
- inadequate seal (try larger size, re-position by gentle traction + push)
- gastric inflation (recognize on capnogram + bag)
- epiglottic obstruction (withdraw partially, re-advance with chin lift)
Pediatric LMA sizing
Size 1.5 (5-10 kg).
Size 2 (10-20 kg).
Size 2.5 (20-30 kg).
Size 3 (30-50 kg).
Size 4 (50-70 kg).
Size 5 (>70 kg).
LMA is standard in pediatric anesthesia for procedures not requiring full muscle relaxation — ENT (myringotomy, tonsil & adenoid where surgical access works around it), ortho extremity, hernia, circumcision.
Often EASIER than mask anesthesia in older children and adolescents (no jaw-thrust fatigue for the anesthetist, hands-free for charting).
Confirm gastric drainage port not obstructed by tongue or epiglottis.
Contraindications + relative cautions
- BMI >40 (seal compromised + reduced pulmonary compliance pushes you over the seal pressure during PPV)
- hiatal hernia with chronic symptoms
- prone position (some experienced operators use iGel or ProSeal prone with success but it's not first-line)
- severe airway anatomy abnormality
- mouth opening <2 cm
LMA does NOT prevent aspiration — the drainage port reduces but does not eliminate the risk.
The seal is only adequate to 20-30 cmH₂O so high airway pressures during obesity or laparoscopy may leak.
If in doubt, intubate.
Postop LMA complications
Dysphagia + dysphonia from cuff pressure on vocal cords — minimize by using lowest effective cuff pressure.
Nerve injury rare but reported: hypoglossal, lingual, recurrent laryngeal — can cause persistent dysphonia or tongue weakness; usually resolves over weeks.
Aspiration: pre-existing risk + intraop regurgitation; second-gen drainage reduces but doesn't eliminate.
Reflux during emergence is the highest-risk time — keep LMA in place until patient awake and protecting airway, then remove.
Avoid blind removal during awakening unless patient is breathing well and follows command.
⚠ Common pitfalls
- Inflating the cuff to maximum — > 60 cmH₂O damages mucosa and worsens seal paradoxically.
- Using a 1st-gen SGA on a full-stomach patient — no gastric port, aspiration risk.
- Sizing by 'looks about right' — go by weight; under-sized leaks, over-sized obstructs.
- Insisting on the SGA past 2 attempts when ventilation is poor — escalate to ETT or FONA.
💎 Clinical pearls
- iGel and other gel-cuff devices need no cuff inflation — saves a step, no overinflation risk.
- Use the SGA as a Plan B in the algorithm; use the intubating LMA (Fastrach) when you need to convert to ETT.
- For laparoscopic cases or steep Trendelenburg, choose 2nd-gen with a gastric port and verify seal pressure ≥30.
- Post-extubation upper-airway obstruction: a quick SGA can rescue before re-paralyzing for re-intubation.
Recap
- iGel and other gel-cuff devices need no cuff inflation — saves a step, no overinflation risk.
- Use the SGA as a Plan B in the algorithm; use the intubating LMA (Fastrach) when you need to convert to ETT.
- For laparoscopic cases or steep Trendelenburg, choose 2nd-gen with a gastric port and verify seal pressure ≥30.
- Post-extubation upper-airway obstruction: a quick SGA can rescue before re-paralyzing for re-intubation.
Mark each section done to complete the module.