Exhausted, SpO₂ 82% on 15 L, PaCO₂ 9.1 kPa and climbing — type I vs type II failure, NIV or tube, and the first safe ventilator settings.
ABCDE
Position, suction, high-flow O₂ while deciding; ABG now; NIV first for COPD/pulmonary oedema if no contraindication; if intubating — preoxygenate 3–5 min, ketamine/etomidate + rocuronium, then lung-protective settings.
Classify: type I (hypoxic, low/normal PaCO₂) vs type II (PaCO₂ >6.5 with low pH) — ABG now; NIV first-line for COPD exacerbation and acute pulmonary oedema if conscious and protecting airway
NIV trial: BiPAP (IPAP 10–15, EPAP 5) for COPD with pH <7.35, or CPAP for pulmonary oedema — reassess ABG at 1 h; failing pH/mental state → intubate
Intubate safely: preoxygenate 3–5 min (NIV/HFNO), ketamine 1–2 mg/kg (or etomidate 0.3 mg/kg) + rocuronium 1.2 mg/kg; have fluids + noradrenaline ready for post-intubation hypotension
Initial ventilator settings: AC volume control, tidal volume 6–8 mL/kg PREDICTED body weight, RR 12–16, FiO₂ 100% then wean to SpO₂ 92–96%, PEEP 5 cmH₂O
Obstructive lungs (asthma/COPD): RR 8–12, high inspiratory flow, long expiratory time — tolerate hypercapnia; hypotension on vent = auto-PEEP → disconnect and allow full exhalation
First 30 min: post-intubation ABG at 15–30 min; plateau pressure <30; confirm tube with continuous ETCO₂; cuff pressure 20–30 cmH₂O and head-of-bed 30–45° (VAP prevention); start analgesia-first sedation (light target RASS 0 to −1 — PADIS) and DVT/GI prophylaxis
Order set
- ABG before + 15–30 min after intubation
- Ketamine 1–2 mg/kg + rocuronium 1.2 mg/kg
- Noradrenaline/fluids primed for induction
- AC/VC: VT 6–8 mL/kg PBW, PEEP 5
- Continuous ETCO₂ + capnography
- Sedation: propofol or fentanyl infusion
- CXR to confirm tube position
- DVT + stress-ulcer prophylaxis
Monitor
- ContinuousETCO₂, SpO₂, airway pressures, plateau
- 15–30 minPost-intubation ABG — adjust RR for pH, not PaCO₂
- q1–4 hAuto-PEEP check in obstructive disease; sedation depth (RASS)
- DailySpontaneous awakening + breathing trials once FiO₂ ≤40% and PEEP ≤8
Escalate / ICU
- pH <7.25 on NIV or falling GCS
- Auto-PEEP with hypotension/barotrauma
- P/F ratio <150 → ARDS pathway
- Need for deep sedation/paralysis to ventilate
Criteria
IntubateGCS <8, exhaustion, refractory hypoxia, or failing pH despite NIV
VT6–8 mL/kg predicted (not actual) body weight
PlateauKeep <30 cmH₂O; driving pressure <15
ExtubateAwake, FiO₂ ≤40%, PEEP ≤8, passes SBT, cuff leak if at risk
Never
- Ventilate to a 'normal' PaCO₂ in a chronic CO₂ retainer — aim for their baseline pH
- Use actual body weight for tidal volume
- Give a long-acting paralytic then struggle to assess neurology
Key
- Predicted body weight: men = 50 + 2.3 kg per inch over 5 ft; women = 45.5 + 2.3
- Post-intubation hypotension is common — preload, pressors ready, and check for auto-PEEP
- ETCO₂ confirms the tube; a normal SpO₂ does not exclude oesophageal intubation
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Silent chest or rising PaCO₂ in asthma
- GCS falling with hypoxia
- Post-intubation hypotension (auto-PEEP, tension PTX, sedation)
- Tube at 18 cm in a tall adult (too high) — 21–23 cm typical
Differentials
- COPD/asthma exacerbation
- Pneumonia, pulmonary oedema
- Pneumothorax
- Metabolic acidosis with respiratory compensation (DKA, sepsis)
Common mistakes
- Bagging too fast pre-intubation → gastric insufflation
- High tidal volumes 'to improve the ABG'
- Sedating without analgesia
- Missing oesophageal intubation because SpO₂ lagged
Disposition & follow-up
ICU for all ventilated patients; daily SAT/SBT paired trials; tracheostomy if ventilated >7–10 days anticipated.
💊 Treatment detail — doses & preparation
Ketaminedissociative anaesthetic
DoseInduction 1–2 mg/kg IV (haemodynamically stable choice)
Preparation200 mg/20 mL vial — give over 60 s; co-give analgesia for maintenance
MonitorBP/HR rise (sympathomimetic), emergence reactions; preserves airway reflexes partly
Rocuroniumparalytic (NMB)
DoseRSI 1.2 mg/kg IV (intubation in 60 s)
Preparation50 mg/5 mL vial undiluted rapid push
MonitorDuration 30–60 min — cannot assess seizures while paralysed without EEG
PropofolIV anaesthetic
DoseSedation 5–50 mcg/kg/min infusion; refractory SE titrate to EEG
Preparation1% (10 mg/mL) lipid emulsion ready vial via syringe pump; change tubing q12 h
MonitorBP (vasodilates), triglycerides, PRIS if prolonged/high dose
Fentanylopioid analgesic
Dose25–100 mcg IV boluses; infusion 0.5–2 mcg/kg/h
Preparation100 mcg/2 mL ampoule undiluted for bolus; infusion 1 mg in 50 mL NS
MonitorRR, sedation score; less hypotension than morphine
Noradrenaline (norepinephrine)vasopressor
Dose0.05–1 mcg/kg/min IV infusion, titrate to MAP ≥65
Preparation4 mg in 250 mL D5W or NS (16 mcg/mL) via infusion pump; central line preferred — proximal peripheral vein acceptable short-term
MonitorContinuous invasive MAP; check limb perfusion, urine output; wean gradually, never stop abruptly
📖 Textbook Ch.7–8; ARDSNet; DAS 2025 (unanticipated difficult intubation)Reviewed July 2026