Airway, Ventilation & NIV

Rapid sequence intubation

Enter weight above for calculated drug doses · Evidence: UpToDate RSI, ACEP 2020, Weingart Push-Dose Pressors

Difficult airway assessment — LEMON Before every RSI

Assess ALL 5 criteria before intubation. Any positive predictor = plan for backup airway (VL, LMA, surgical).

Look externally

Small jaw, large tongue, short neck, obesity, facial trauma, beard, blood/vomit in airway, trismus, prior neck surgery/radiation

Evaluate 3-3-2 rule

3 finger breadths mouth opening · 3 finger breadths hyoid-to-chin · 2 finger breadths thyroid notch-to-hyoid. Any <3 fingers = difficult

Mallampati score

Class I (uvula visible) = easy · Class II (partial) = some difficulty · Class III (soft palate only) = difficult · Class IV (hard palate only) = very difficult

Obstruction

Angioedema, abscess, epiglottitis, haematoma, Ludwig's angina, foreign body, tumour, tracheal deviation

Neck mobility

Cervical spine injury, arthritis, collar, halo, prior cervical surgery. Reduced extension = reduced laryngeal view

Difficult airway — beyond LEMON: MOANS · RODS · SHORT Plan your backups

LEMON predicts a difficult laryngoscopy. These three predict difficulty with your rescue options — assess them so you are not surprised when plan A fails. Any positive predictor across multiple mnemonics = double-setup, most experienced operator, double-lumen suction, and surgical airway marked and ready.

Difficult bag-mask ventilation — MOANS

Mask seal

Beard, facial trauma/blood, distorted anatomy, edentulous (cheeks collapse). High Mallampati also predicts difficult ventilation.

Obesity / Obstruction

BMI >26 or late pregnancy; upper-airway obstruction (angioedema, abscess, epiglottitis, foreign body) impedes mask ventilation.

Age >55

Loss of upper-airway tissue tone with age increases difficult-mask risk.

No teeth

Edentulous patients lose mask seal — leave dentures in for BVM, remove for laryngoscopy. Use a two-hand/two-person technique.

Stiff / Snores

Stiff lungs (high resistance/poor compliance: ARDS, asthma, pulmonary oedema, pregnancy) + sleep apnoea / snoring.

Difficult supraglottic / extraglottic device — RODS

Restricted mouth opening

Need adequate interincisor gap to seat an LMA/SGA — trismus or limited opening prevents insertion.

Obstruction

Obstruction at or below the glottis (foreign body, supraglottic mass) — an SGA sits above the cords and will not bypass it.

Distorted anatomy

Tumour, prior surgery, radiation, fixed deformity — a distorted hypopharynx prevents a proper SGA seal.

Stiff lungs / cervical spine

High airway pressures (asthma, ARDS, oedema) exceed the SGA seal pressure and leak. Stiff/immobile neck limits positioning.

Difficult cricothyrotomy — SHORT

Surgery / Scar

Prior neck surgery or scarring distorting landmarks and tracheal access.

Haematoma / infection

Haematoma, abscess, or any mass in the path of the incision over the cricothyroid membrane.

Obesity / access problem

Obesity or fixed-flexion neck deformity burying the landmarks — palpate and mark the membrane early.

Radiation

Prior neck radiation distorts and fixes tissue planes, making the membrane hard to identify and incise.

Tumour

Tumour in or near the airway, in or above the field of the cricothyrotomy.

RSI protocol — step by step

Pre-oxygenation (3+ minutes)

Goal: SpO2 100% — denitrogenate lungs to maximise apnoea safe time (3–8 min normoxic, vs 1 min without pre-ox).

• Flush-rate O2: NRB at 15 L/min + nasal cannula 15 L/min beneath mask
• Upright position 20–30° head-up (increases FRC by 15–30%)
• BVM with PEEP valve 5–10 cmH2O if obtunded
• Apnoeic oxygenation: leave NC at 15 L/min during laryngoscopy

Preparation — "STOP MAID"

Suction on · Team roles assigned · O2 flush rate · Position optimal · Monitoring (ECG/SpO2/EtCO2) · Airway equipment laid out · IV access confirmed · Drugs drawn up

Push-dose pressor ready: Ephedrine 5 mg/mL (1 mL ephedrine 50 mg/mL + 9 mL NS) OR Epinephrine 10 mcg/mL (1 mL 1:10,000 + 9 mL NS)

Pre-treatment (optional, 3 min before induction)

Blunts haemodynamic response to laryngoscopy. Indicated in TBI (prevents ICP spike), cardiovascular disease, reactive airway.

Fentanyl: — (1–3 mcg/kg, max 200 mcg) IV over 1–2 min · 3 min before induction

Induction agent — choose one

Give rapidly IV. Onset 30–60 sec. Patient loses consciousness.

Ketamine: — (1–2 mg/kg) — preferred in haemodynamic instability, bronchospasm (use 1–1.5 mg/kg in shock)
Etomidate: — (0.3 mg/kg) — haemodynamically stable; avoid in sepsis (adrenal suppression)
Propofol: — (1.5–2.5 mg/kg) — only if haemodynamically stable; significant hypotension risk

Neuromuscular blockade — give immediately after induction

Succinylcholine: — (1.5 mg/kg, max 200 mg) — fastest offset; avoid in hyperkalaemia, burns >24h, crush/denervation
Rocuronium: — (1.2 mg/kg) — preferred if succinylcholine contraindicated; reverse with sugammadex 16 mg/kg

Succinylcholine contraindicated: K+ >5.5, burns >24h, crush/denervation/UMN injury >72h, muscular dystrophy, personal/family history MH, pseudocholinesterase deficiency

Laryngoscopy & intubation (60–90 sec after NMB)

Optimise with: BURP manoeuvre (Backwards-Upwards-Right-Pressure on thyroid cartilage) · External laryngeal manipulation · Ramped position for obese patients (ear-to-sternal-notch alignment).

Confirm: Bilateral breath sounds · EtCO2 waveform (gold standard) · Chest rise · SpO2 improving · CXR for depth

Post-intubation management

Sedation: Propofol 5–50 mcg/kg/min OR Midazolam 0.03–0.1 mg/kg/hr
Analgesia: Fentanyl — (1–2 mcg/kg q1h or 25–100 mcg/hr infusion)
Ongoing NMB (if needed): Rocuronium — (10–12 mcg/kg/min infusion)

Initiate ventilator: start with lung-protective settings (see Ventilator tab). Target SpO2 92–98%, EtCO2 35–45 mmHg. Head of bed 30–45°.

Resuscitate before you intubate Optimise first

Induction + positive pressure unmasks shock. The shock-index–high, hypoxic, or acidotic patient peri-arrests at induction. If time allows, optimise the physiology BEFORE pushing drugs — it is the highest-yield safety step in emergency RSI.

Haemodynamics

Treat shock first: fluid bolus and/or pressor running before induction if shock index >0.9 or SBP <90. Reduce the induction-agent dose in shock (e.g. ketamine 0.5–1 mg/kg).

Oxygenate

Pre-oxygenate to SpO2 ≥95% if achievable: flush-rate NRB + nasal cannula 15 L/min, apnoeic oxygenation. Add PEEP/NIV for the shunt physiology that will not come up on a mask.

Position

Ear-to-sternal-notch, ramped in the obese, head-up 20–30° to raise FRC and prolong safe apnoea time. Bed at the right height, suction at the head.

Pressor primed

Push-dose pressor mixed, labelled, and in hand (see push-dose card); peripheral norepinephrine or a pump infusion spiked and ready to start the moment the pressure drops.

DSI if needed

For the agitated, hypoxic patient who will not tolerate pre-oxygenation: delayed sequence intubation — dissociative-dose ketamine to allow pre-ox, then paralyse and intubate.

Cannot intubate / cannot oxygenate (CICO)Emergency

CICO = Immediately life-threatening. Do NOT attempt more than 3 laryngoscopy attempts. Call for help early. Declare CICO loudly.

Attempt LMA / supraglottic airway

Size 3 (30–50 kg), 4 (50–70 kg), 5 (70–100 kg). Insert, ventilate. May be bridge to surgical airway.

Reverse NMB (if rocuronium used)

Sugammadex: — (16 mg/kg IV) — full reversal within 3 min. Only works for rocuronium/vecuronium.

Emergency surgical airway — scalpel-bougie-tube

Preferred technique: 1) Vertical 3 cm skin incision over cricothyroid membrane · 2) Horizontal stab incision through membrane · 3) Tracheal hook caudally · 4) Bougie inserted · 5) 6.0 ETT railroaded over bougie · 6) Inflate cuff, ventilate, confirm EtCO2

Sugammadex — reversal doses by depth of block Rocuronium / vecuronium only

Sugammadex encapsulates aminosteroid blockers (rocuronium > vecuronium). It does NOT reverse succinylcholine, cisatracurium, or other benzylisoquinolines. Dose to the depth of block. All doses are based on actual body weight.

Scenario

Depth of block

Dose

Onset

Notes

Moderate reversal

TOF ≥2 twitches (T2 reappeared)

2 mg/kg IV

~2 min

Routine reversal of moderate block. TOF ratio >0.9 typically within ~2 min — faster than neostigmine.

Deep reversal

1–2 post-tetanic counts, no TOF twitches

4 mg/kg IV

~3 min

For deep block where spontaneous recovery has not yet reached TOF twitches.

Immediate / CICO rescueCICO

Right after an intubating dose of rocuronium

16 mg/kg IV

<3 min

Reverses ~3 min after 1.2 mg/kg rocuronium. Does NOT restore spontaneous ventilation if apnoea is from the induction agent or the underlying problem — secure the airway.

Push-dose pressors Peri-intubation hypotension

Peri-intubation hypotension in 20-35% of ED intubations. Prepare vasopressors BEFORE RSI in haemodynamically compromised patients (SBP <90, shock index >1).

Agent

Preparation

Dose

Onset

Notes

Phenylephrine1st line

1 mL of 10 mg/mL + 9 mL NS = 1 mg/mL. Then 1 mL + 9 mL NS = 100 mcg/mL

50-200 mcg IV q2-5 min

60-90 sec

Pure alpha. No chronotropy. Best when tachycardia present. Reflex bradycardia possible.

EpinephrineBrady + hypotension

1 mL of 1:10,000 (0.1 mg/mL) + 9 mL NS = 10 mcg/mL

10-20 mcg IV q2 min

30-60 sec

Alpha + beta. Use when bradycardia + hypotension. Bridges to infusion.

VasopressinAlternative

1 mL of 20 units/mL + 19 mL NS = 1 unit/mL

1-2 units IV q5-10 min

1-2 min

Non-adrenergic. Useful in distributive shock. No tachycardia.

Post-intubation checklist Immediately post-RSI

Confirm ETT position

EtCO2 waveform (gold standard) + bilateral breath sounds + CXR tip 2-3 cm above carina

Secure & document

Tape or commercial holder. Note lip depth. Bite block if biting risk.

Ventilator settings

AC/VC: TV 6-8 mL/kg IBW, RR 14-16, PEEP 5, FiO2 1.0 initially then wean

Sedation & analgesia

Propofol 5-50 mcg/kg/min OR midazolam 0.02-0.1 mg/kg/h + fentanyl 25-100 mcg/h. RASS target -2

Pressure targets

Peak <35 cmH2O. Plateau <30 cmH2O. Driving pressure <15 cmH2O.

HOB + OG/NG

Head of bed 30-45 degrees. Gastric decompression via NG/OG.

VAP bundle

Cuff pressure 20-30 cmH2O. Oral care. Daily interruption planning.

Disposition

ICU handover: indication, settings, drugs given, exam findings, plan.

Crashing on the ventilator — DOPES Sudden desat / hypotension

Sudden desaturation or hypotension on the vent → ACT FIRST: DISCONNECT from the ventilator and bag manually on 100% O2 with a PEEP valve. If the patient is suddenly easy to bag the problem is the circuit/vent; if HARD to bag, suspect tension pneumothorax or tube obstruction. Then work DOPES.

Displacement

Tube migrated — oesophageal, supraglottic, or right-mainstem. Check depth at the lip, EtCO2 waveform (flat = oesophageal/no output), bilateral breath sounds, direct/video look. Re-confirm before anything else.

Obstruction

Kinked tube, biting, mucous plug, blood clot. Pass a suction catheter — if it will not pass, the tube is obstructed. Place a bite block. High peak pressures with a normal plateau point here.

Pneumothorax

Especially TENSION (positive-pressure ventilation drives it). Unilateral absent breath sounds + hypotension + high airway pressures + tracheal deviation → immediate needle/finger decompression, do not wait for CXR.

Equipment failure

O2 source disconnected/empty, circuit leak or disconnect, vent malfunction, depleted cylinder, ETT cuff leak. This is why you disconnect and hand-bag — it both diagnoses and treats equipment failure.

Stacked breaths / auto-PEEP

Air trapping in obstructive disease (asthma/COPD): rising peak pressures, hypotension, distended chest that does not fall. Treatment = disconnect to let the chest deflate, then lower RR / TV and lengthen expiratory time (see Ventilator tab).

Ventilator settings

Enter height + sex above for IBW-based tidal volume · Evidence: ARDSNet NEJM 2000, GOLD 2024, ATS/ESICM Guidelines

Tidal volume is based on Ideal Body Weight (IBW), not actual weight — obese patients have the same lung size as their height-matched non-obese counterparts. Using actual weight causes volutrauma.

Live calculated settings

Enter weight + height + sex above to generate calculated vent settings

IBW

—

Tidal volume (6 mL/kg)

—

ARDSNet / lung-protective

Tidal volume (8 mL/kg)

—

Normal lungs / post-op

Min ventilation (6×14)

—

TV × RR target range

Min ventilation (6×20)

—

Upper end for ARDS

Min TV (4 mL/kg)

—

Absolute minimum (ARDS refractory)

ARDSNet Protocol (NEJM 2000): 6 mL/kg IBW reduces mortality vs 12 mL/kg. Plateau pressure <30 cmH2O. Driving pressure <15 cmH2O. Accept permissive hypercapnia (pH >7.20). SpO2 target 88–95%.

Mode

AC/VC

Volume-controlled. Guarantees tidal volume delivery.

Tidal volume

— mL

6 mL/kg IBW (range 4–8). Calculated from height/sex above.

Resp rate

14–20

Start 14–16. Increase to compensate for low TV if needed. Max 35.

PEEP

Start 5. Use ARDSNet PEEP/FiO2 table below to titrate.

FiO2

0.60

Titrate to SpO2 88–95%. Use PEEP/FiO2 table — increase together.

I:E ratio

1:2

Standard. Avoid inverse ratio (risk of auto-PEEP).

Plateau limit

<30

Check q4h. If >30: reduce TV by 1 mL/kg to minimum 4 mL/kg. Accept lower pH.

Driving pressure

<15

Plateau − PEEP. Independent mortality predictor. Reduce TV or PEEP if >15.

ARDSNet PEEP / FiO2 table (lower-PEEP strategy)

FiO2	0.30	0.40	0.50	0.60	0.70	0.80	0.90	1.00
PEEP	5	5–8	8–10	10	10–14	14	14–18	18–24

Auto-PEEP risk: Obstructive physiology traps air → dynamic hyperinflation → haemodynamic collapse. Prioritise full exhalation: low RR, low I:E, high flow rate. Permissive hypercapnia acceptable (pH >7.20).

Mode

AC/VC

Volume control ensures delivered volume despite high airway resistance.

Tidal volume

— mL

6–8 mL/kg IBW. Small volumes reduce hyperinflation risk.

Resp rate

10–14

Low RR = more time for exhalation. Start 10–12. Permissive hypercapnia.

PEEP

3–5

Low extrinsic PEEP (3–5 cmH2O). Must measure intrinsic/auto-PEEP. Extrinsic PEEP <80% of auto-PEEP.

FiO2

Titrate

COPD: target SpO2 88–92% (avoid hypoxic drive suppression). Asthma: 92–98%.

I:E ratio

1:3 – 1:5

Prolonged expiratory phase — essential. Use highest flow rate to shorten inspiratory time.

Flow rate

60–80 L/min

High inspiratory flow shortens Ti, maximises expiratory time.

PaCO2 target

45–60+

Permissive hypercapnia acceptable if pH >7.20. Do NOT hyperventilate — causes severe auto-PEEP.

Lung-protective ventilation for all intubated patients — not just ARDS. Even normal lungs develop VILI with high tidal volumes. Start conservative; wean FiO2 and PEEP as tolerated.

Mode

AC/VC or PRVC

Volume or pressure-regulated. PRVC adapts to compliance changes.

Tidal volume

— mL

6–8 mL/kg IBW. Even normal lungs: avoid >8 mL/kg.

Resp rate

12–16

Targeting normocapnia (PaCO2 35–45 mmHg).

PEEP

Standard physiological PEEP. Prevents alveolar derecruitment at end-expiration.

FiO2

Titrate

Start 0.60, wean to <0.60 to avoid O2 toxicity. Target SpO2 92–98%.

I:E ratio

1:2

Standard 1:2. Adjust if patient-ventilator dyssynchrony noted.

Plateau

<30

Monitor plateau. In normal lungs plateau usually <25 with these settings.

PaCO2 target

35–45

Normocapnia unless underlying condition warrants otherwise.

TBI/Neuro: Hypoxia (SpO2 <90%) and hypocapnia (PaCO2 <35) are BOTH harmful — cause secondary brain injury. Normocapnia mandatory. Hyperventilation only for impending herniation (brief, bridge to intervention).

Mode

AC/VC

Tidal volume

— mL

6 mL/kg IBW. Lung-protective even in TBI.

Resp rate

14–16

Titrate to PaCO2 35–40 mmHg. Serial ABG essential. EtCO2 correlation variable in TBI.

PEEP

Standard PEEP 5. Higher PEEP reduces cerebral venous drainage — balance with oxygenation needs.

FiO2

Target 94–98%

SpO2 >94% mandatory. Avoid hyperoxia (PaO2 >300 — associated with worse outcomes).

PaCO2 target

35–40

Normocapnia. Prophylactic hyperventilation is HARMFUL (cerebral vasoconstriction → ischaemia).

Herniation protocol

PaCO2 30–35

Brief hyperventilation for acute herniation ONLY — bridge to mannitol/hypertonic saline/surgery. Not sustained.

Head position

HOB 30°

Head of bed 30–45°, neutral alignment. Reduces ICP, improves CPP.

Cardiogenic pulmonary oedema: high PEEP recruits flooded alveoli, reduces preload (beneficial in LV failure), and offloads work of breathing. Higher FiO2 requirements initially.

Mode

AC/VC or PRVC

Tidal volume

— mL

6–8 mL/kg IBW.

Resp rate

14–18

Targeting normocapnia. High RR compensates for low TV if needed.

PEEP

8–12

Higher PEEP recruits flooded alveoli. Reduces preload (good in LV failure). Monitor for RV afterload increase.

FiO2

High initially

Start 0.80–1.0. Wean as oedema clears. Target SpO2 92–98%.

I:E ratio

1:2

Plateau

<30

Note

High PEEP reduces RV preload too — monitor for RV failure in acute RV dysfunction/massive PE.

Obese patients: use IBW (not actual weight) for tidal volume. Higher PEEP needed to overcome chest wall weight and recruit dependent atelectasis. Ramped position for intubation and ventilation.

Mode

AC/VC or PRVC

Tidal volume

— mL

6–8 mL/kg IBW — critical. Using actual weight causes severe volutrauma.

Resp rate

14–18

Higher RR may be needed due to reduced FRC and increased O2 consumption.

PEEP

8–12

Higher PEEP needed to overcome chest wall weight and recruit dependent atelectasis. Titrate to oxygenation.

FiO2

Titrate

Often need higher FiO2 initially. Target SpO2 92–98%.

Position

HOB 30–45°

Reduces diaphragmatic compression, improves FRC.

Recruitment

Consider

PEEP trial or recruitment manoeuvre (sustained inflation 30–40 cmH2O × 30 sec) for refractory hypoxia.

IBW formula

Enter height above

High airway pressure alarm — peak vs plateau Troubleshoot

Perform an inspiratory hold to read the plateau. Peak reflects airway resistance; plateau reflects lung/chest-wall compliance. A peak–plateau gap >5 cmH2O = a resistance problem; a small gap with high plateau = a compliance problem.

High peak · NORMAL plateau → RESISTANCE

Kinked or bitten ETT — place a bite block

Secretions / mucous plug — pass a suction catheter

Bronchospasm — bronchodilators (asthma/COPD/anaphylaxis)

Right-mainstem migration — withdraw, re-confirm depth

Small/partially obstructed tube

Action: suction, bite block, bronchodilators, check tube depth.

High peak · HIGH plateau → COMPLIANCE

Pneumothorax — especially tension (decompress)

Right-mainstem intubation / atelectasis

Auto-PEEP / breath stacking (obstructive disease)

Pulmonary oedema / worsening ARDS / pneumonia

Abdominal compartment syndrome, ascites, chest-wall stiffness

Action: breath sounds + CXR; if unilateral absent sounds + hypotension → needle/finger decompression for tension PTX.

Auto-PEEP / breath stacking — rescue Obstructive crash

Recognise: rising peak pressures, hypotension, and a chest that stays inflated in an asthma/COPD patient on the vent. Dynamic hyperinflation raises intrathoracic pressure → falling preload → obstructive shock and PEA if untreated.

DISCONNECT the circuit

Take the patient off the vent and let the trapped air escape — watch the chest fall and listen for the prolonged escaping breath. This is both diagnostic and immediately therapeutic; if hypotension resolves, auto-PEEP was the cause. Push fluids while disconnected.

Lengthen expiratory time

On reconnection: reduce respiratory rate, reduce tidal volume, and increase inspiratory flow rate to shorten Ti — driving the I:E ratio to 1:4–1:5. Give the lungs time to empty between breaths.

Permissive hypercapnia + treat the obstruction

Accept a high PaCO2 if pH >7.20 — do NOT raise the rate to blow it off (that worsens stacking). Aggressive bronchodilators, steroids, and magnesium for the underlying bronchospasm.

Sudden hypotension + high pressures in an intubated asthmatic = auto-PEEP OR tension pneumothorax until proven otherwise. Disconnect first; if disconnection does not fix it, decompress the chest.

BiPAP / NIV / CPAP

Non-invasive ventilation — avoids intubation in appropriate patients · Evidence: NICE NG38, BTS NIV Guidelines 2016, AHA/ACC CPE Guidelines

NIV Absolute Contraindications: Respiratory arrest / Apnoea · Unable to protect airway · Facial trauma/burns/anatomy precluding mask fit · Uncooperative/agitated patient (relative) · Vomiting/high aspiration risk · Haemodynamic instability not responsive to fluids · Recent upper GI/oesophageal surgery

Live NIV / BiPAP quick reference

Select condition below — settings shown. Enter weight for any weight-related context.

IPAP start

12–16

cmH2O — titrate up by 2 q15 min

EPAP start

4–6

cmH2O

Pressure support

8–12

cmH2O (IPAP − EPAP)

Backup RR

14–16

/min

SpO2 target

88–92%

Controlled O2

Reassess ABG

1–2 hours

If pH not improving → intubate

COPD + acute hypercapnic RF: NIV reduces intubation rate by 65%, mortality by 50% (Brochard 1995, Plant 2000). First-line treatment. Target pH >7.25 on NIV; if <7.25 after 1h → intubate.

Mode

BiPAP (S/T)

IPAP start

12–16 cmH2O

Increase by 2 cmH2O q15 min to max 20–30. Target: ↓RR, ↑TV, ↓accessory muscle use.

EPAP start

4–6 cmH2O

Low EPAP (3–5) for COPD — avoid dynamic hyperinflation. Higher EPAP (6–8) if significant secretions or OSA component.

Pressure support

8–14 cmH2O

PS = IPAP − EPAP. Aim 8–14 cmH2O. Drives ventilation.

Backup RR

14–16 /min

FiO2 target

SpO2 88–92%

Controlled O2 — avoid suppressing hypoxic drive. Titrate.

Reassess

ABG at 1–2h

If pH not improving >7.25 → escalate to intubation. Do not delay.

Evidence

Brochard 1995, Plant 2000, BTS NIV 2016

Cardiogenic pulmonary oedema: CPAP equivalent to BiPAP for most patients (3CPO trial). Both superior to O2 alone — reduces intubation rate ~50%. CPAP is simpler. Use BiPAP if hypercapnia.

Mode (1st choice)

CPAP

If normocapnic — equivalent to BiPAP (3CPO trial). Simpler, better tolerated.

CPAP level

5–10 cmH2O

Start 5 cmH2O. Increase by 2 cmH2O every 5–10 min to max 10–12. Reduces preload and afterload.

Mode (if hypercapnia)

BiPAP (S/T)

BiPAP IPAP

10–16 cmH2O

BiPAP EPAP

5–8 cmH2O

FiO2

High — SpO2 >94%

Reassess

15–30 min

If not improving → reassess diagnosis. Add GTN infusion, furosemide. Early escalation if deteriorating.

Evidence

3CPO Trial (NEJM 2008)

Obesity Hypoventilation Syndrome (OHS): chronic hypercapnia + obesity (BMI >30). High EPAP needed to overcome chest wall mass. Often requires high IPAP. Treat as COPD exacerbation approach.

Mode

BiPAP (S/T)

IPAP start

16–20 cmH2O

Higher IPAP required. Titrate to clinical response and PaCO2.

EPAP start

8–12 cmH2O

Higher EPAP to overcome chest wall weight and upper airway obstruction.

Backup RR

14–16 /min

FiO2

SpO2 88–92%

Position

HOB 30–45°

Post-extubation NIV: prophylactic BiPAP in high-risk patients (hypercapnia, COPD, CHF, prolonged intubation) reduces re-intubation rate. Not effective once post-extubation respiratory failure is established — treat early or re-intubate.

Mode

BiPAP (S/T)

IPAP

12–16 cmH2O

EPAP

5–8 cmH2O

Schedule

q4h minimum

Prophylactic: scheduled sessions post-extubation × 24–48h. Rescue: apply immediately if deteriorating.

Caution

Early decision

Do not delay re-intubation. NIV should not be used to delay inevitable intubation once failure is established.

Hypoxic respiratory failure: NIV evidence weaker than for hypercapnic failure. HFNC often preferred first-line. NIV for immunocompromised (avoids intubation complications). High failure rate — monitor closely.

Mode

BiPAP or CPAP

IPAP

14–20 cmH2O

EPAP

8–10 cmH2O

Higher EPAP needed for oxygenation in diffuse lung disease.

FiO2

High — SpO2 >92%

ROX index

Monitor q1–2h

Use ROX index (HFNC tab) as failure predictor. Escalate early.

Neuromuscular disease (MG, GBS, ALS, DMD): ventilatory failure from muscle weakness rather than lung disease. High IPAP needed to overcome weak respiratory muscles. Bulbar dysfunction = relative contraindication (aspiration risk).

Mode

BiPAP (S/T)

IPAP

18–25 cmH2O

High IPAP to compensate for weak inspiratory muscles. Titrate to tidal volume >7 mL/kg.

EPAP

4–6 cmH2O

Backup RR

14–18 /min

Higher backup rate if bulbar weakness — patient may be unable to trigger.

Escalation

VC <1 L or <20 mL/kg

Intubate early in GBS/MG crisis if VC declining rapidly, NIF worsening, or bulbar dysfunction progressing.

CPAP — settings & indications

Indications

OSA / home CPAP patients — use home settings

Cardiogenic pulmonary oedema — reduces preload + afterload

Post-extubation prophylaxis (obese, high-risk)

Hypoxia without hypercapnia (consider HFNC first)

CPAP starting settings

CPAP pressure

5-10 cmH2O

Start 5. Titrate by 2 cmH2O. Max 15 cmH2O for CPE.

FiO2

0.40-1.0

Start high, titrate to SpO2 >94%.

CPAP vs BiPAP

Single pressure

BiPAP if hypercapnic or inadequate effort on CPAP alone.

High-flow nasal cannula

Evidence: FLORALI trial (NEJM 2015), ROX index (Intensive Care Med 2019)

FLORALI trial: HFNC superior to standard O2 and non-inferior to NIV in acute hypoxic respiratory failure. 90-day intubation rate significantly lower. First-line for non-hypercapnic hypoxic RF.

Starting settings

Flow rate

30–40 L/min

Start 30 L/min. Increase to 40–60 L/min for severe hypoxia. Max 60 L/min. Higher flow = better FiO2 delivery + PEEP effect (~1 cmH2O per 10 L/min).

FiO2

0.60–1.0

Start high (0.60–1.0 if severe). Titrate to SpO2 target 92–96%. Wean FiO2 first, then flow.

Temperature

37°C

Heated humidified gas. Improves tolerance and mucociliary clearance. 34°C if less tolerated.

Reassess

1–2 hours

Calculate ROX index at 2, 6, and 12h. Clinical reassessment at 30–60 min.

ROX index calculatorFailure predictor

ROX = (SpO2/FiO2) ÷ RR. Predicts HFNC failure and need for intubation. Calculate at 2h, 6h, and 12h.

SpO2 FiO2 RR

ROX ≥4.88 at 12h = low risk of intubation
ROX 3.85–4.88 = intermediate — close monitoring
ROX <3.85 = HIGH RISK — prepare for intubation

HFNC failure criteria — when to escalate

Escalate to NIV or intubation if:

ROX index <2.85 at any time or <3.85 at 12h

SpO2 <90% on FiO2 1.0 and flow 60 L/min

Rising PaCO2 or pH <7.30 (hypercapnia developing)

Increasing RR >35/min or worsening accessory muscle use

Haemodynamic instability

Altered mental status / inability to protect airway

HFNC weaning protocol

Wean FiO2 first to 0.40 while maintaining SpO2 >92%

Then reduce flow rate by 5 L/min increments q4–8h

Trial conventional O2 when flow <20 L/min and FiO2 ≤0.40

Airway equipment

ETT sizing, blade selection, LMA, surgical airway reference

ETT size & insertion depth

Adult Male

7.5–8.0

23–25 cm

Cuffed

Adult Female

7.0–7.5

21–23 cm

Cuffed

Newborn

3.0–3.5

9–10 cm

Uncuffed

6 months

3.5

11 cm

Uncuffed

1 year

4.0

12 cm

Uncuffed

2 years

4.5

13 cm

Uncuffed

4 years

5.0

14 cm

Uncuffed or cuffed −0.5

6 years

5.5

15 cm

Uncuffed or cuffed −0.5

8 years

6.0

16 cm

Consider cuffed −0.5

10 years

6.5

17 cm

Cuffed 6.0

12+ years

7.0

18–20 cm

Cuffed

Paediatric formula: Uncuffed: (age/4) + 4 · Cuffed: (age/4) + 3.5 · Depth: (age/2) + 12 cm
Confirm with: bilateral breath sounds + EtCO2 waveform + CXR (tip at carina level)

LMA / supraglottic airway sizing

<5 kg

4 mL

3.5

1.5

5–10 kg

7 mL

4.0

10–20 kg

10 mL

4.5–5.0

2.5

20–30 kg

14 mL

5.0–5.5

30–50 kg

20 mL

6.0

50–70 kg

30 mL

6.0–6.5

70–100 kg

40 mL

7.0

>100 kg

50 mL

7.0

Laryngoscope blade selection

Mac 3

Curved

Average adult

Most common; sits in vallecula

Mac 4

Curved

Large adult / long neck

Larger mouth / longer blade

Miller 2

Straight

Average adult

Lifts epiglottis directly

Miller 3

Straight

Large adult / anterior airway

Anterior larynx, long epiglottis

Mac 1–2

Curved

Paediatric (toddler–child)

Mac 1 infant; Mac 2 small child

Miller 0–1

Straight

Neonate–infant

Miller 0 neonate; preferred in infants (anterior larynx)

VL (any)

Video

Difficult airway / anticipated difficult

First-line if LEMON positive. Glidescope/McGrath/C-MAC.

Emergency surgical airway — scalpel-bougie-tubeCICO protocol

Declare CICO loudly. Stop intubation attempts. Move directly to surgical airway. Hesitation kills. Perform within 2–3 minutes of decision.

Position & identify

Neck extended. Palpate and identify cricothyroid membrane (between thyroid and cricoid cartilages). Stabilise larynx with non-dominant hand.

Skin incision

Vertical 3–4 cm skin incision over CTM — vertical avoids vessels. Index finger palpates through skin to confirm CTM location.

Horizontal stab incision

Single horizontal stab through CTM with No.10 scalpel. Caudal traction on trachea with hook through incision.

Bougie insertion

Bougie passed caudally through incision into trachea. Feel tracheal rings (clicks) and hold-up at carina to confirm tracheal placement.

ETT over bougie

Cuffed 6.0 ETT railroaded over bougie. Rotate 90° anticlockwise if resistance at arytenoids. Advance to 8–9 cm at skin.

Confirm & ventilate

Remove bougie. Inflate cuff. Ventilate. Confirm EtCO2 waveform + bilateral breath sounds. Secure tube. CXR.