When to intubate in GCS?

GCS ≤ 8 requires intubation for airway protection. The patient cannot protect their own airway at this level of consciousness. Motor score is the most prognostically important component.

What is the best initial fluid for sepsis resuscitation?

Lactated Ringer's (LR) is the preferred resuscitation fluid. The SMART trial (2018) showed balanced crystalloids reduced death, new renal failure, and persistent renal dysfunction compared to normal saline.

When to start vasopressors in septic shock?

Start norepinephrine (first-line vasopressor) if MAP remains < 65 mmHg after initial 30 mL/kg crystalloid resuscitation, or earlier if patient is profoundly hypotensive. Do not delay pressors to complete full fluid resuscitation.

Why can serum uric acid be normal during acute gout?

During acute inflammation, IL-6 increases renal urate excretion and redistributes urate from plasma to tissues. Up to 40% of acute gout flares have normal serum uric acid. Joint aspiration with polarized microscopy is needed for definitive diagnosis.

How do you distinguish lupus flare from infection in SLE?

Key clues: CRP is low/normal in flare but elevated in infection. Complement (C3/C4) drops in flare but is normal/elevated in infection. Procalcitonin is elevated in bacterial infection but normal in flare. Anti-dsDNA rises in flare, stable in infection.

What is the difference between DKA and HHS?

DKA features acidosis (pH 600), hyperosmolality (> 320), and minimal ketosis -typically in Type 2 DM. DKA requires insulin drip; HHS requires aggressive fluid resuscitation first.

When to give tPA in acute ischemic stroke?

IV alteplase (tPA) can be given within 4.5 hours of last known well time in eligible patients. CT head must rule out hemorrhage first. For large vessel occlusion, mechanical thrombectomy can be performed up to 24 hours with favorable imaging.

What antibiotics for community-acquired pneumonia?

Inpatient non-ICU: ceftriaxone + azithromycin. ICU: ceftriaxone + azithromycin (add vancomycin if MRSA risk). Outpatient healthy: amoxicillin. Outpatient with comorbidities: augmentin + azithromycin or respiratory fluoroquinolone. Duration: 5 days if clinically stable for 48 hours.

How to interpret iron studies?

Iron deficiency: low ferritin (< 30), high TIBC, low iron, low transferrin saturation (< 20%). Anemia of chronic disease: normal/high ferritin (acute phase reactant), low TIBC, low iron. A ferritin of 50-100 in an inflamed patient may still represent iron deficiency.

What is the correction rate for hyponatremia?

Correct sodium no more than 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome (ODS). For symptomatic severe hyponatremia with seizures, give 3% hypertonic saline 100-150 mL bolus over 10-20 minutes. If overcorrected, use D5W + DDAVP rescue protocol.

When to start antibiotics in meningitis?

Within 30-60 minutes. Do NOT delay antibiotics for LP or CT. Draw blood cultures, start empiric antibiotics (vancomycin + ceftriaxone ± ampicillin if > 50 or immunocompromised), then perform LP when possible. Dexamethasone should be given before or with the first antibiotic dose.

DOACs vs warfarin in antiphospholipid syndrome?

DOACs are contraindicated in APS. The TRAPS trial (2018) showed rivaroxaban was inferior to warfarin with more thrombotic events in triple-positive APS patients. Warfarin with INR target 2-3 is the standard for APS, indefinitely.

How to manage scleroderma renal crisis?

ACE inhibitors (captopril) are life-saving -start immediately and titrate aggressively. Do NOT hold for rising creatinine. Steroids > 15 mg prednisone per day precipitate scleroderma renal crisis. ARBs are NOT a substitute -evidence is only for ACEi.

What are the 4 pillars of heart failure treatment?

Guideline-directed medical therapy (GDMT) for HFrEF: (1) ARNI or ACEi/ARB, (2) beta-blocker (carvedilol, metoprolol succinate, or bisoprolol), (3) MRA (spironolactone or eplerenone), (4) SGLT2 inhibitor (dapagliflozin or empagliflozin). All four should be initiated and titrated to target doses.

Mechanical Ventilation -Modes & Settings -RoundsRx

🔍 Overview -Airway Decision-Making

Indications for Intubation

Airway protection -GCS ≤ 8, inability to handle secretions, impending obstruction
Hypoxemic respiratory failure -SpO₂ < 90% despite high-flow O₂, P/F < 200
Hypercapnic respiratory failure -rising PaCO₂ with acidosis (pH < 7.25), fatigue
Impending respiratory failure -accessory muscle use, paradoxical breathing, rising work of breathing

Try NIV First (if appropriate): BiPAP/CPAP for COPD exacerbation, cardiogenic pulmonary edema, and mild-moderate hypoxemia. Avoid NIV in decreased consciousness, vomiting, hemodynamic instability, or inability to cooperate.

Key Vent Concepts

Pressure vs Volume

Volume Control (VC): You set the tidal volume -the vent delivers exactly that volume. Pressure varies. Preferred in ARDS (tight TV control).

Pressure Control (PC): You set the pressure -the volume varies depending on lung compliance. Preferred when you want to limit pressures.

Key Numbers to Know Every Morning

Tidal volume (Vt) -actual delivered TV in mL/kg IBW
Rate (RR) -set respiratory rate
FiO₂ -fraction of inspired oxygen (0.21–1.0)
PEEP -positive end-expiratory pressure in cmH₂O
Peak pressure (Ppeak) -total pressure to deliver breath (airway resistance + alveolar)
Plateau pressure (Pplat) -alveolar distension pressure (inspiratory hold). Target ≤ 30.
Driving pressure = Pplat − PEEP. Target ≤ 15. Strong predictor of ARDS mortality.
P/F ratio = PaO₂ ÷ FiO₂ -oxygenation index
SpO₂ target -88–95% in ARDS; 94–98% otherwise

💨 Oxygen Delivery Devices

Escalation Ladder -Low Flow to High Flow

Rule of thumb: Each 1 L/min of nasal cannula adds ~4% FiO₂ above room air (21%). So 2L NC ≈ 28%, 4L ≈ 36%, 6L ≈ 44%. This breaks down above 6L.

Device	Flow Rate	FiO₂ Delivered	Best For	⚠️ Limitations
Nasal Cannula (NC)	1–6 L/min	24–44%	Mild hypoxemia. Stable patients. Most common starting point.	⚠️ Uncomfortable > 6L (dries mucosa). Unreliable FiO₂ -depends on patient's minute ventilation and mouth breathing.
Simple Face Mask	5–10 L/min	35–55%	Moderate hypoxemia. Short-term use (ED, post-op).	⚠️ Must run ≥ 5 L/min to prevent CO₂ rebreathing. Claustrophobic. Can't eat/talk well.
Venturi Mask	4–12 L/min	Precise: 24%, 28%, 31%, 35%, 40%, 50%	COPD patients -need precise low FiO₂ (24–28%) to avoid suppressing hypoxic drive. Color-coded adapters.	⚠️ Max 50% FiO₂. Bulky. Used mainly for COPD.
Non-Rebreather (NRB)	10–15 L/min	60–90%	Severe hypoxemia. Pre-oxygenation before intubation. CO poisoning. Trauma.	⚠️ Reservoir bag must stay inflated. Not truly 100% -room air mixes around mask. If patient needs NRB → consider escalation.
High-Flow Nasal Cannula (HFNC)	20–60 L/min	21–100% (titratable)	Hypoxemic respiratory failure, post-extubation, immunocompromised (avoid intubation), pre-oxygenation. Delivers heated humidified O₂.	⚠️ Generates ~1 cmH₂O PEEP per 10 L/min (so 60L ≈ 6 cmH₂O). Patient must breathe spontaneously. If still desatting on HFNC 60L/100% → intubate.

When to Escalate

1

NC 1–6L -SpO₂ still < 92% → escalate

2

Simple mask / NRB 10–15L -SpO₂ still < 92% or work of breathing increasing → escalate

3

HFNC 40–60L -if SpO₂ < 92% on 60L/100% FiO₂, or RR > 30, or accessory muscle use → next step

4

NIV (BiPAP/CPAP) -if COPD exacerbation or cardiogenic pulmonary edema → try NIV before intubation

5

Intubation + Mechanical Ventilation -failing all above, declining mental status, unable to protect airway

⚠️ ROX Index (HFNC failure prediction): ROX = (SpO₂/FiO₂) ÷ RR. Check at 2, 6, 12 hours. ROX < 3.85 at 6h → high risk of HFNC failure → prepare for intubation. ROX > 4.88 → likely safe to continue HFNC.

🌬️ Non-Invasive Ventilation (NIV)

CPAP vs BiPAP

	CPAP	BiPAP
What it does	Single continuous pressure (like PEEP)	Two pressures: IPAP (inhale) + EPAP (exhale)
Helps with	Oxygenation only -splints airways open, recruits alveoli	Both oxygenation AND ventilation -IPAP augments tidal volume (blows off CO₂), EPAP = PEEP
Best for	Cardiogenic pulmonary edema, OSA	COPD exacerbation (hypercapnic failure), obesity hypoventilation, neuromuscular weakness
Typical settings	CPAP 5–10 cmH₂O	IPAP 10–20 / EPAP 5–8 cmH₂O. Start IPAP 10, EPAP 5. Titrate IPAP up by 2 q15–30 min for CO₂.
Pressure support	None (single pressure)	PS = IPAP − EPAP. Higher PS = more ventilatory support. PS of 10 cmH₂O is moderate support.

Indications for NIV

COPD exacerbation with respiratory acidosis (pH < 7.35, PaCO₂ > 45) -strongest evidence, reduces intubation by 65% Brochard, 1995
Cardiogenic pulmonary edema -CPAP or BiPAP both work. Reduces preload + afterload + recruits flooded alveoli. 3CPO, 2008
Post-extubation -prophylactic NIV in high-risk patients reduces reintubation
Immunocompromised with respiratory failure -try NIV/HFNC first to avoid vent-associated infections
Palliative / DNI patients -ceiling of care when intubation is not desired

🚫 NIV Contraindications: Arrest · GCS ≤ 8 · Vomiting/aspiration risk · Shock · Facial trauma · Airway obstruction · Uncooperative

▶ How to Pick BiPAP Settings, Step by Step (tap to expand)

Understanding IPAP, EPAP & Pressure Support

The Key Concept: BiPAP delivers two pressures. IPAP (Inspiratory Positive Airway Pressure) is the pressure during inhale. EPAP (Expiratory Positive Airway Pressure) is the pressure during exhale (functionally identical to PEEP). The difference between them is Pressure Support (PS) = IPAP − EPAP. PS is what actually pushes air into the lungs and generates tidal volume.

Setting	What It Controls	How to Titrate	Think of It As
EPAP	Oxygenation (splints alveoli open, recruits collapsed lung)	Start 5 cmH₂O. ↑ by 2 if SpO₂ < 90% despite FiO₂. Max ~10-12.	= PEEP. Treats the O₂ problem.
IPAP	Ventilation (how much air is pushed in per breath)	Start 10 cmH₂O. ↑ by 2 q15-30 min if CO₂ still high. Max ~20-25.	= Tidal volume driver. Treats the CO₂ problem.
PS (= IPAP − EPAP)	Tidal volume per breath	Higher PS → bigger breaths → more CO₂ blown off. Target PS 5-15 cmH₂O for most patients.	PS is essentially your tidal volume knob. PS of 10 ≈ TV of ~400-500 mL in most adults.
FiO₂	Oxygen concentration	Start 100%, wean to target SpO₂ 88-92% (COPD) or 92-96%. Always wean FiO₂ before weaning pressures.	Supplemental O₂. Independent of IPAP/EPAP.
Rate (backup)	Minimum breaths/min if patient doesn't trigger	Set 12-16. Usually not needed, patient triggers their own breaths.	Safety net for apnea.

The Two Knobs: Fix O₂ vs Fix CO₂

Problem	Which Knob to Turn	What to Do
SpO₂ low (oxygenation failure)	↑ EPAP (or ↑ FiO₂)	EPAP recruits alveoli and improves V/Q matching. Think of it like adding PEEP on a vent.
CO₂ high (ventilation failure)	↑ IPAP (keeping EPAP the same)	This increases PS, which increases tidal volume, which blows off more CO₂. ↑ IPAP by 2 cmH₂O every 15-30 min until pH improves.
Both	↑ EPAP for O₂, ↑ IPAP for CO₂	Always increase IPAP at least as much as EPAP to maintain the PS gap. If you raise EPAP by 2, raise IPAP by 2 also.

⚠️ Critical Rule: If you increase EPAP without increasing IPAP, you decrease PS, which decreases tidal volume, which can worsen CO₂ retention. Always maintain or increase the PS gap when raising EPAP.

Example: IPAP 12 / EPAP 5 = PS 7. If you raise EPAP to 8 but keep IPAP at 12 → PS drops to 4 → patient gets smaller breaths → CO₂ rises. Fix: raise IPAP to 15 / EPAP 8 = PS 7 maintained.

Starting Protocol & Titration

Step 1: Start BiPAP

IPAP 10 / EPAP 5 (PS = 5) -safe starting point for most patients
FiO₂ 100% (wean later based on SpO₂)
Backup rate 12-16
Fit mask snugly. Coach patient: "Breathe with the machine, let it push air in."

Step 2: Check ABG at 1 Hour

CO₂ still elevated / pH still acidotic? → ↑ IPAP by 2 (e.g., IPAP 12 → 14 → 16). Recheck in 1h.
SpO₂ still low? → ↑ EPAP by 2 (and raise IPAP by 2 to maintain PS). Or ↑ FiO₂.
Both improving? → Hold current settings. Wean FiO₂ first.

Step 3: Reassess at 2 Hours

pH improving and patient comfortable? → BiPAP is working. Continue. Recheck ABG q4-6h.
No improvement or worsening? → NIV failure. Prepare for intubation. Do NOT delay.

Clinical Example: BiPAP Preventing Intubation in COPD

🏥 Scenario: 68M with severe COPD exacerbation

Presentation: Brought in by EMS, severe respiratory distress, accessory muscle use, speaking in 1-2 word sentences. RR 32, SpO₂ 84% on 6L NC, HR 115, BP 155/90.

ABG on arrival: pH 7.22, PaCO₂ 78, PaO₂ 52, HCO₃ 30 (acute-on-chronic hypercapnic respiratory failure).

Step 1 (Time 0): Start BiPAP IPAP 10 / EPAP 5 (PS = 5), FiO₂ 50%.
→ After 15 min: RR 28, SpO₂ 89%. Still distressed. CO₂ not moving.

Step 2 (Time 15 min): ↑ IPAP to 14 / EPAP 5 (PS = 9). Keep FiO₂ 50%.
→ After 30 min: RR 24, SpO₂ 91%. Patient visibly more comfortable. Able to speak in short sentences.

Step 3 (Time 1 hour): Repeat ABG: pH 7.28, PaCO₂ 62, PaO₂ 68. pH improving, CO₂ coming down. ↑ IPAP to 16 / EPAP 5 (PS = 11).

Step 4 (Time 2 hours): ABG: pH 7.32, PaCO₂ 55, PaO₂ 72. RR 20, SpO₂ 93%. BiPAP is working. Intubation avoided.

Overnight: Continue BiPAP. Wean FiO₂ to 35%. Give Ipratropium/Albuterol (DuoNeb) nebs q4h, Methylprednisolone (Solu-Medrol) 60 mg IV daily (= prednisone 40 mg PO; switch to PO when tolerating), Azithromycin (Zithromax) 500 mg IV. Next AM: ABG 7.38 / 48 / 78. Trial off BiPAP → tolerates nasal cannula. Extubation avoided.

✅ Why this worked: Each time we raised IPAP (while keeping EPAP the same), we increased PS → bigger tidal volumes → more CO₂ blown off per breath → pH corrected. The key was titrating IPAP up aggressively every 15-30 minutes until the ABG improved. If by 1-2 hours the pH hadn't improved, this patient would have needed intubation.

Quick Reference: Common BiPAP Settings by Scenario

Scenario	Starting IPAP / EPAP	PS	Goal	Titration Target
COPD exacerbation	10-12 / 5	5-7	↓ CO₂, ↑ pH	↑ IPAP q15-30 min → max 20-25. Target pH > 7.30.
Cardiogenic pulmonary edema	10-12 / 8-10	2-4	↑ O₂, ↓ preload	Higher EPAP for recruitment. CPAP 10-12 is often enough.
Obesity hypoventilation	14-18 / 8-10	6-10	↓ CO₂	Need higher pressures due to chest wall compliance. ↑ IPAP aggressively.
Neuromuscular weakness	10-14 / 5	5-9	Augment weak inspiratory muscles	↑ IPAP if NIF declining. Low threshold for intubation (GBS, MG crisis).
Post-extubation (prophylactic)	8-10 / 5	3-5	Prevent reintubation	Low support. Alternate with HFNC. Wean over 24-48h.
DNI / comfort care	10-15 / 5-8	5-7	Symptom relief	Titrate to comfort + dyspnea relief. No ABG targets.

Special Consideration: The Obese Patient

Obesity makes BiPAP harder. Abdominal and chest wall fat reduces lung compliance, compresses the diaphragm (especially supine), and causes baseline hypoventilation. These patients need more aggressive settings than normal-weight patients.

Challenge	Why It Happens	What to Do
Higher IPAP needed	Chest wall is stiff → needs more pressure to generate the same tidal volume	Start IPAP 14-18 (not 10). May need IPAP 20-25 in BMI > 50. Don't be afraid to go higher.
Higher EPAP needed	Abdominal mass compresses diaphragm → atelectasis → V/Q mismatch → hypoxemia	Start EPAP 8-10 (not 5). Acts like higher PEEP to recruit collapsed bases.
Positioning matters hugely	Supine = diaphragm splinted by abdomen. Functional residual capacity drops.	Sit patient upright at 30-45° or reverse Trendelenburg. This alone can improve oxygenation dramatically.
Chronic CO₂ retention	Obesity hypoventilation syndrome (OHS), chronic hypercapnia with elevated bicarb	Don't normalize CO₂. Target their baseline PaCO₂ (often 50-60). Check HCO₃, if elevated, it's chronic. Over-ventilating → alkalosis → arrhythmias.
Mask leak	Facial fat makes mask seal harder	Use a full-face mask (oronasal). May need a larger size. Check for beard. Tighten straps but avoid skin breakdown.

💡 Practical Example, BMI 48 with OHS Exacerbation:
Patient arrives with pH 7.18, PaCO₂ 95, HCO₃ 34 (chronic + acute). SpO₂ 82%.
• Start: IPAP 18 / EPAP 10 (PS = 8), FiO₂ 40%, upright positioning
• 15 min: SpO₂ 88%, still tachypneic → ↑ IPAP to 22 (PS = 12)
• 1 hour ABG: pH 7.25, PaCO₂ 75. Improving. Hold settings.
• Target: pH > 7.30 and PaCO₂ toward their baseline (~55-60). Do NOT target PaCO₂ 40, that's over-ventilation for this patient.

When NIV is Failing -Escalate to Intubation

⚠️ Signs of NIV failure (reassess within 1–2 hours):
• No improvement in pH or PaCO₂ after 1–2h of BiPAP
• Worsening tachypnea (RR > 30 despite NIV)
• SpO₂ < 90% despite FiO₂ escalation
• Declining mental status (somnolence, confusion)
• Hemodynamic instability
• Patient intolerance / non-compliance with mask
Do NOT delay intubation if NIV is failing. Late intubation = worse outcomes.

🚨 Rapid Sequence Intubation (RSI)

The 7 P's of RSI

1

Preparation
Equipment: ETT (7.0–7.5 women, 7.5–8.0 men), laryngoscope (video preferred), bougie, BVM, suction, end-tidal CO₂, backup airway (LMA). Two IV lines. Monitors on. Confirm code status.

2

Pre-oxygenation
3–5 minutes of 100% O₂ via NRB or HFNC 60L/min (builds O₂ reserve in FRC). Goal: SpO₂ 100%. In obese or critically ill → apneic oxygenation: leave NC at 15L under the NRB or continue HFNC during intubation attempt.

3

Pre-treatment (optional)
Fentanyl 1–3 mcg/kg IV (blunts sympathetic surge -useful in elevated ICP, aortic dissection). Lidocaine 1.5 mg/kg IV (for elevated ICP -controversial). Most patients skip this step.

4

Paralysis with Induction (push simultaneously)
See drug table below. Induction agent → wait 20–30 seconds → paralytic.

5

Protection & Positioning
Sniffing position: neck flexed, head extended (aligns oral-pharyngeal-laryngeal axes). Elevate head of bed 20–30° in obese. Apply cricoid pressure (Sellick maneuver -controversial but still used).

6

Placement
Direct or video laryngoscopy → visualize cords → pass tube through cords → inflate cuff → confirm placement: (1) End-tidal CO₂ waveform (gold standard), (2) bilateral breath sounds, (3) misting in tube, (4) CXR for depth (2–4 cm above carina).

7

Post-intubation Management
Start sedation (propofol or midazolam + fentanyl). Set initial vent settings. Secure tube (tape or holder). NG/OG tube. Arterial line if not already placed. ABG in 30 min. CXR to confirm ETT position.

RSI Drug Table

Drug	MOA	Dose	Onset	Duration	Best For	⚠️ Avoid If
INDUCTION AGENTS
Etomidate	GABA-A agonist	0.3 mg/kg IV push	15–30 sec	5–15 min	Hemodynamically unstable -most neutral on BP. Most common RSI induction agent.	⚠️ Adrenal suppression (single dose is clinically insignificant). Avoid in septic shock? -debated.
Ketamine (Ketalar)	NMDA antagonist	1–2 mg/kg IV push	30–60 sec	10–20 min	Asthma/bronchospasm (bronchodilator), hypotension (preserves BP via sympathetic stimulation), elevated ICP (old teaching said avoid -now considered safe).	⚠️ Psychosis/schizophrenia (emergence reactions). Increases secretions -give glycopyrrolate.
Propofol (Diprivan)	GABA-A agonist	1.5–2.5 mg/kg IV push	15–30 sec	5–10 min	Status epilepticus (anticonvulsant), elevated ICP (lowers ICP).	⚠️ Causes significant hypotension -avoid in shock, hypovolemia. Egg/soy allergy (controversial).
Midazolam (Versed)	GABA-A agonist (benzo)	0.1–0.3 mg/kg IV push	1–2 min	15–30 min	Rarely used for RSI (slower onset). Backup option. Provides amnesia.	⚠️ Hypotension. Slower onset than etomidate/ketamine. Can reverse with flumazenil.
PARALYTICS (NEUROMUSCULAR BLOCKERS)
Succinylcholine (Anectine)	Depolarizing NMB -mimics ACh, sustained depolarization → paralysis	1–1.5 mg/kg IV push	30–45 sec	6–10 min	Fastest onset + shortest duration. Good when you need to quickly reassess neuro status (e.g., stroke).	⚠️ Hyperkalemia (burns > 48h, crush injury, denervation, renal failure with K⁺ > 5.5). Malignant hyperthermia (personal/family history). Myasthenia gravis.
Rocuronium (Zemuron)	Non-depolarizing NMB -competitive ACh blocker at nicotinic receptor	1.2 mg/kg IV push (RSI dose)	45–60 sec	45–70 min	When succinylcholine is contraindicated. Reversible with sugammadex (16 mg/kg for immediate reversal). Becoming first-line at many centers.	⚠️ Long duration -if can't intubate AND can't ventilate, patient is paralyzed for 45+ min (unless sugammadex available).

⚠️ Cannot Intubate, Cannot Oxygenate (CICO) -Surgical Airway
If 2 intubation attempts fail AND cannot bag-mask ventilate AND LMA fails → cricothyrotomy. Palpate cricothyroid membrane (between thyroid and cricoid cartilage) → vertical skin incision → horizontal stab through membrane → insert bougie → railroad 6.0 ETT or cric tube. This is the final rescue. Do not delay.

Difficult Airway Predictors (LEMON):
L ook externally (short neck, obesity, facial trauma, beard)
E valuate 3-3-2 (3 fingers mouth opening, 3 fingers hyoid-to-chin, 2 fingers thyroid notch-to-floor of mouth)
M allampati score (III/IV = harder)
O bstruction (epiglottitis, angioedema, tumor, hematoma)
N eck mobility (c-spine collar, ankylosing spondylitis, rheumatoid arthritis)

⚙️ Ventilator Modes Explained

▶ Ventilator Modes Explained, AC, PC, SIMV, PSV, APRV (tap to expand)

Every vent mode answers two questions: (1) What triggers a breath? (patient or machine), (2) What's guaranteed -volume or pressure?

Mode	How It Works	You Set	What Varies	Best For	⚠️ Watch For
AC/VC Assist Control / Volume Control	Every breath (patient-triggered or machine-triggered) delivers a set tidal volume.	TV, RR, FiO₂, PEEP, flow rate	Pressure (Ppeak varies with compliance/resistance)	Most common mode. Default for most intubations. ARDS (guarantees 6 mL/kg TV).	⚠️ If compliance drops → pressures rise → barotrauma. Watch Pplat.
AC/PC Assist Control / Pressure Control	Every breath delivers a set pressure for a set inspiratory time.	Pressure, I-time, RR, FiO₂, PEEP	Tidal volume (varies with compliance)	When you want to limit pressures strictly. Neonatal/pediatric. Some ARDS protocols.	⚠️ If compliance worsens → TV drops → hypoventilation. Must monitor TV closely.
SIMV Synchronized Intermittent Mandatory Ventilation	Delivers set number of mandatory breaths. Patient can take extra breaths on their own (unsupported or with PS).	TV, RR, FiO₂, PEEP, PS level	Patient's spontaneous breaths are variable	Weaning mode -gradually reduce mandatory rate as patient takes over.	⚠️ Increases work of breathing if PS too low on spontaneous breaths. Largely fallen out of favor -SBT preferred for weaning.
PSV Pressure Support Ventilation	Patient triggers every breath. Vent augments each breath with set pressure support.	PS level, FiO₂, PEEP	TV and RR (entirely patient-driven)	SBT (PS 5–8 cmH₂O), weaning assessment, awake cooperative patients.	⚠️ No backup rate -if patient becomes apneic, no breaths are delivered. Need apnea backup alarm.
APRV Airway Pressure Release Ventilation	Sustained high pressure (P-high) with brief releases to low pressure (P-low) for CO₂ clearance. Essentially inverse-ratio CPAP.	P-high, T-high, P-low, T-low	TV during releases	Refractory ARDS -keeps alveoli open with sustained high pressure. Allows spontaneous breathing.	⚠️ Complex to manage. Requires experience. Not proven superior to standard lung-protective ventilation. Hemodynamic effects from sustained high intrathoracic pressure.

Quick Decision: Which Mode?

Scenario	Mode	Why
Fresh intubation (default)	AC/VC	Guarantees tidal volume. Simple. Predictable.
ARDS	AC/VC (6 mL/kg IBW)	Must control TV tightly for lung protection.
COPD / asthma	AC/VC (low rate, long I:E)	Need guaranteed TV with long expiratory time to avoid air trapping.
High peak pressures	Switch AC/VC → AC/PC	Limits pressure delivery. But monitor TV -may drop.
Ready to wean / SBT	PSV 5–8 / PEEP 5	Minimal support. Tests if patient can breathe independently.
Refractory ARDS	APRV (by experienced team)	Last resort before ECMO. Keeps alveoli recruited.

🫁 Oxygenation vs Ventilation

The Most Important Concept on the Vent

Oxygenation and ventilation are two completely separate physiologic processes. They are fixed by different vent settings. Confusing them is the #1 mistake interns make in the ICU. If you learn nothing else about the vent, learn this table.

	🔵 Oxygenation (O₂)	🔴 Ventilation (CO₂)
What is it?	Getting oxygen INTO the blood	Getting CO₂ OUT of the blood
Measured by	PaO₂ (ABG) or SpO₂ (pulse ox)	PaCO₂ (ABG) or EtCO₂ (capnography)
Normal values	PaO₂ 80–100 mmHg, SpO₂ 94–98%	PaCO₂ 35–45 mmHg
Problem	Hypoxemia -O₂ too low	Hypercapnia -CO₂ too high Hypocapnia -CO₂ too low
Vent settings that fix it	FiO₂ (↑ = more O₂ delivered) PEEP (↑ = recruits collapsed alveoli, improves gas exchange surface area)	Respiratory Rate (↑ RR = blow off more CO₂) Tidal Volume (↑ TV = each breath removes more CO₂) Together = Minute Ventilation (MV = RR × TV)
Think of it as	How much oxygen you're putting IN the lungs	How much air you're moving THROUGH the lungs

Quick Decision Framework

🔵 Patient is HYPOXEMIC (SpO₂ low)

Step 1: ↑ FiO₂ (quick fix -increase the O₂ concentration)
Step 2: ↑ PEEP (recruit alveoli -increases surface area for gas exchange)
Step 3: Prone positioning -flip patient face-down ≥ 16h/day. Redistributes ventilation to dorsal lung (where perfusion is greatest) → improves V/Q matching. Mortality benefit in severe ARDS (P/F < 150) PROSEVA, 2013
Step 4: Inhaled nitric oxide (iNO) 5–40 ppm or inhaled epoprostenol -selective pulmonary vasodilators. Dilate vessels ONLY in ventilated alveoli → redirects blood flow to functioning lung units → improves V/Q matching + oxygenation. ⚠️ No proven mortality benefit -used as rescue/bridge therapy.
Step 5: ECMO (VV-ECMO) -when all above fail. Blood is oxygenated externally. Consider if P/F < 80 despite optimal vent + prone + iNO.

⚠️ Do NOT increase RR or TV -these do not fix oxygenation. Breathing faster doesn't put more O₂ in the blood if the alveoli can't exchange gas.

🔴 Patient is HYPERCAPNIC (CO₂ high)

Step 1: ↑ Respiratory Rate (blow off more CO₂ per minute)
Step 2: ↑ Tidal Volume (each breath removes more CO₂)
Minute Ventilation = RR × TV → this is what determines CO₂ clearance

Step 3 (if bronchospasm): Heliox (70–80% helium / 20–30% O₂) -helium is less dense than nitrogen → reduces turbulent airflow resistance → gas flows past the obstruction more easily → improves ventilation in severe bronchospasm/upper airway obstruction refractory to bronchodilators. ⚠️ Limitation: Max FiO₂ is 30% (rest is helium), so don't use if patient needs high FiO₂.

⚠️ Do NOT increase FiO₂ or PEEP -these do not remove CO₂. Giving more oxygen doesn't help ventilation.
⚠️ Watch for auto-PEEP: If RR too high (especially in COPD), patient may not fully exhale → air trapping → hemodynamic collapse.

Common Scenarios -What to Adjust

ABG Shows	Problem	Adjust	⚠️ Watch For
PaO₂ 55, SpO₂ 88%	Hypoxemia	↑ FiO₂ and/or ↑ PEEP	FiO₂ > 0.6 for > 24h → O₂ toxicity. Wean FiO₂ first, then PEEP.
PaCO₂ 65, pH 7.22	Respiratory acidosis (hypoventilating)	↑ RR or ↑ TV (↑ minute ventilation)	Auto-PEEP in COPD. Pplat > 30 if TV too high. Max RR ~35 before ineffective.
PaCO₂ 25, pH 7.55	Respiratory alkalosis (overventilating)	↓ RR or ↓ TV (↓ minute ventilation)	Patient may be anxious/in pain → treat the cause. Don't just sedate to fix CO₂.
PaO₂ 55 AND PaCO₂ 60	Both hypoxemic + hypercapnic	↑ FiO₂/PEEP (for O₂) AND ↑ RR/TV (for CO₂). If refractory → prone + iNO + ECMO.	Suggests severe disease (ARDS + dead space). Consider prone, paralytics, iNO, ECMO.
PaO₂ 120, FiO₂ 1.0	Over-oxygenating	↓ FiO₂ (wean to target SpO₂ 92–96%)	Hyperoxia harms: ↑ mortality in cardiac arrest, stroke, MI. Wean FiO₂ aggressively.

The Memory Trick

🔵

O₂ = FiO₂ + PEEP

Escalation: FiO₂ → PEEP → Prone → iNO → ECMO

🔴

CO₂ = RR × TV

"How much air am I moving?"

⚠️ Permissive hypercapnia: In ARDS, it's OK to let CO₂ run high (up to 60–70) and pH drop to ~7.20 -as long as oxygenation is maintained. The priority is lung-protective ventilation (TV 6 mL/kg, Pplat ≤ 30). Don't sacrifice lung protection to normalize a CO₂ number. Same principle applies in status asthmaticus (accept PaCO₂ 60–80 with pH > 7.20 to avoid breath stacking and auto-PEEP).

Oxygen Dissociation Curve (40-50-60 / 70-80-90 Rule)

The relationship between PaO₂ (the partial pressure of dissolved O₂) and SpO₂ (% of hemoglobin saturated) is sigmoid, not linear. Memorizing three points on the curve lets you mentally convert between the two at the bedside.

PaO₂ (mmHg)	SpO₂ (%)	What it means
40	70	Mixed venous blood. Severe hypoxemia if arterial.
50	80	Critically low. On the steepest part of the cliff.
60	90	The "knee." Above this you're on the safe plateau; below, on a cliff.
~95-100	97-100	Normal arterial. Far up the plateau.

Bedside shortcut: on the steep part of the curve (SpO₂ 70-90), SpO₂ minus 30 ≈ PaO₂. So an SpO₂ of 88 ≈ PaO₂ ~58. Above SpO₂ 90 the plateau is too flat for this trick to work, small SpO₂ changes hide much larger PaO₂ swings.

Why the curve has a knee at SpO₂ 90 / PaO₂ 60

Above the knee (PaO₂ > 60, SpO₂ > 90): flat plateau. Big PaO₂ changes produce only small SpO₂ changes. PaO₂ 100 vs PaO₂ 80 both look like 96-97% on the pulse ox.
Below the knee (PaO₂ < 60, SpO₂ < 90): steep cliff. Small PaO₂ drops produce massive SpO₂ drops. Crashes look sudden because the curve falls off fast here.
Why this matters for targets: aim for SpO₂ ≥ 92% (general) or 88-92% (COPD CO₂ retainers, permissive hypoxemia in ARDS). Sitting at 92% is at the edge, small drops can plummet quickly.

Curve shifts (the Bohr effect and friends)

Direction	Effect	Caused by
RIGHT shift	Hgb releases O₂ more easily (higher P50). Good for tissues, bad for lungs at low PaO₂.	CADET, face Right: ↑ CO₂, Acidosis, 2,3-DPG (BPG), Exercise, Temperature.
LEFT shift	Hgb holds O₂ tighter (lower P50). Hgb saturates well in the lungs but unloads poorly to tissues.	Hypothermia, alkalosis, ↓ CO₂, ↓ 2,3-BPG (stored blood), CO poisoning, methemoglobin, fetal hemoglobin.

Two states where the pulse ox lies:

CO poisoning: SpO₂ reads ~100% even though tissues are profoundly hypoxic. The pulse ox can't distinguish HbCO from HbO₂. Use co-oximetry (carboxyhemoglobin level) on a venous or arterial sample. Treat with 100% O₂ via NRB; hyperbaric for severe cases.
Methemoglobinemia: SpO₂ stuck around 85% regardless of true saturation. Suspect with cyanosis unresponsive to O₂, "chocolate brown" blood, history of dapsone, benzocaine, nitrites, or aniline dyes. Treat with methylene blue 1-2 mg/kg IV (avoid in G6PD deficiency).

P/F ratio = PaO₂ ÷ FiO₂ -the single best number to assess oxygenation on a vent.
> 300: Normal
200–300: Mild ARDS
100–200: Moderate ARDS
< 100: Severe ARDS → consider prone, paralytics, ECMO

Types of Respiratory Failure

Type	Name	Mechanism	ABG Pattern	Common Causes	Treatment Focus
Type 1	Hypoxemic	Failure of gas exchange -O₂ can't cross alveolar membrane into blood. V/Q mismatch, shunt, diffusion impairment.	PaO₂ < 60 PaCO₂ normal or low	Pneumonia, ARDS, pulmonary edema, PE, pulmonary fibrosis, atelectasis	🔵 FiO₂ + PEEP → prone → iNO → ECMO
Type 2	Hypercapnic	Failure of ventilation -can't move enough air to clear CO₂. Pump failure (muscles, drive, mechanics).	PaCO₂ > 50 pH < 7.35 PaO₂ may be low too	COPD, asthma, obesity hypoventilation, neuromuscular disease (GBS, MG, ALS), drug overdose (opioids), chest wall deformity	🔴 RR × TV (↑ minute ventilation). BiPAP first if possible.
Type 3	Perioperative	Atelectasis from anesthesia, supine positioning, diaphragm splinting (pain, abdominal distension).	PaO₂ low PaCO₂ usually normal	Post-surgical (especially abdominal/thoracic), obesity, poor pain control limiting deep breathing	Incentive spirometry, early mobilization, pain control, CPAP if needed
Type 4	Shock	Hypoperfusion → insufficient O₂ delivery to tissues despite adequate lung function. Respiratory muscles fatigue from hypoperfusion.	Lactic acidosis Mixed picture	Cardiogenic shock, septic shock, hypovolemic shock, massive PE	Treat the shock first (fluids, vasopressors, inotropes). Intubate to reduce O₂ consumption by respiratory muscles.

Why does this matter? Knowing the type tells you what to fix. Type 1 → fix oxygenation (FiO₂/PEEP). Type 2 → fix ventilation (RR/TV or BiPAP). Type 3 → prevent/reverse atelectasis. Type 4 → fix the circulation, not just the lungs.

📌 Settings

Initial Vent Settings

Parameter	Standard	ARDS	COPD/Obstructive
Mode	AC/VC or AC/PC	AC/VC	AC/VC or SIMV
Tidal Volume	8 mL/kg IBW	6 mL/kg IBW	6–8 mL/kg IBW
Rate	14–16 /min	18–22 /min	10–14 /min (avoid stacking)
FiO₂	Start 1.0, wean	Wean to keep SpO₂ 88–95%	Target SpO₂ 88–92%
PEEP	5 cmH₂O	8–16 (ARDSnet table)	Auto-PEEP concern -keep low
I:E Ratio	1:2	1:2 to 1:3	1:3 to 1:4 (more time to exhale)

📌 Trouble

Acute Deterioration on the Vent -DOPE

Patient suddenly desaturating or high pressures alarm → Call for help + use DOPE mnemonic immediately

D -Displacement

ETT displaced (too deep → right mainstem, or dislodged)
Check: confirm with laryngoscope, CXR, ETCO₂, auscultation
Fix: reposition or replace tube

O -Obstruction

Mucus plug, biting tube, kinked circuit
Check: suction catheter passes easily? Pass suction first
Fix: suction, reposition head, bite block

P -Pneumothorax

Tension pneumothorax: absent breath sounds + tracheal deviation + hypotension
Fix: needle decompression NOW (2nd ICS, MCL or 4th ICS, anterior axillary line) then chest tube. Do NOT wait for CXR if hemodynamically unstable.

E -Equipment

Vent malfunction, circuit disconnect, O₂ supply failure
Fix: disconnect from vent → manually bag the patient → troubleshoot equipment

High Peak, Normal Plateau

Peak – Plateau > 10 cmH₂O → airway resistance problem (mucus plug, bronchospasm, kinked tube). Treat: suction, bronchodilators, reposition.

High Peak AND High Plateau

Both elevated → decreased compliance problem (worsening ARDS, pneumothorax, pulmonary edema, pneumonia). Check CXR, assess clinically.

🧪 Workup

Workup

ABG pre/post intubation
CXR -ETT 2-4cm above carina
Plateau pressure -goal <30
Driving pressure -Pplat−PEEP, goal <15
Auto-PEEP -expiratory hold
Peak vs Plateau -high peak + normal plat = airway resistance; both high = compliance problem

🚨 Management

Management

Lung-protective: TV 6–8 mL/kg IBW, Pplat < 30, driving pressure < 15
ARDS: TV 6 mL/kg IBW ARDSNet, 2000, PEEP per ARDSNet table, prone if P/F < 150 PROSEVA, 2013
Daily SBT: FiO₂ ≤ 40%, PEEP ≤ 8, following commands → PSV 5/5 × 30 min
Sedation: RASS 0 to −2. Daily SAT before SBT.

💊 Medications

Medications

Drug	Dose	Route	Notes
Propofol (Diprivan)	5–50 mcg/kg/min	IV	First-line sedation. ⚠️ Propofol infusion syndrome (PRIS) risk if > 48h or > 80 mcg/kg/min (check CK, triglycerides, lactate).
Fentanyl (Sublimaze)	25–200 mcg/hr	IV	Analgesia-first approach. Preferred analgesic in ICU. Lipophilic -accumulates > 72h.
Cisatracurium	1–3 mcg/kg/min	IV	Neuromuscular blockade for severe ARDS × 48h. Must have adequate sedation first -paralyzed + aware = torture. ACURASYS, 2010
Dexmedetomidine	0.2–1.5 mcg/kg/hr	IV	Less delirium than benzos MENDS, 2007. SEDCOM, 2009. DEXCOM, 2016: reduced delirium and shorter time to extubation vs midazolam. ⚠️ Bradycardia, hypotension. No respiratory depression -can use during SBT.

NONSEDA, 2020: No sedation vs light sedation in mechanically ventilated patients showed similar outcomes, though no-sedation had more agitation episodes. Supports minimizing sedation depth when feasible.

🔓 Weaning & Extubation

Ventilator Weaning & Extubation

Step 1: Daily Spontaneous Awakening Trial (SAT)

Stop sedation infusions daily (unless contraindicated: active seizures, alcohol withdrawal, paralytics, elevated ICP)
Assess: Is patient following commands? Opening eyes? Breathing comfortably?
Restart sedation at half dose if patient fails (agitation, RR > 35, SpO₂ < 88%, distress)

Step 2: Spontaneous Breathing Trial (SBT)

Perform if SAT passes. Place on minimal vent support (CPAP 5 / PS 5–8) for 30–120 minutes.

SBT readiness criteria: FiO₂ ≤ 40%, PEEP ≤ 8, hemodynamically stable (no/low vasopressors), adequate mental status, intact cough reflex.

Pass criteria -ALL of the following:

RR < 30, SpO₂ > 90%, TV > 5 mL/kg IBW
RSBI (Rapid Shallow Breathing Index) = RR ÷ Vt (in L) < 105 -most validated weaning predictor
No distress, paradoxical breathing, or diaphoresis
HR and BP within 20% of baseline

Step 3: Extubation Checklist

Passed SBT ✓
Airway reflexes intact -strong cough, follows commands
Cuff leak test: deflate cuff → listen for air leak around tube. No leak suggests laryngeal edema → post-extubation stridor risk → give dexamethasone and delay extubation
Secretion burden manageable (not suctioning > q2h)
Consider dexamethasone 8 mg IV q8h × 4 doses starting 12h before extubation if intubated > 7 days or failed cuff leak
Anesthesia or airway team notified if anticipated difficult reintubation

⚠️ Failed Extubation: Need to reintubate within 48–72 hours -associated with significantly higher mortality (up to 25–50%). Better to wait one more day than to extubate prematurely. Risk factors for failure: age > 65, COPD, HF, weak cough, excessive secretions, high RSBI.

Post-extubation: Apply supplemental O₂ (nasal cannula or HFNC). Monitor closely for 24–48h. If high-risk for reintubation → prophylactic HFNC or NIV (BiPAP) post-extubation reduces reintubation rates.

📋 On Rounds

On Rounds

Pimp Questions

What is driving pressure and why does it matter?

Driving pressure = Pplat − PEEP. It reflects the stress on functional lung units. A driving pressure > 15 cmH₂O is independently associated with increased ARDS mortality even when TV and Pplat are within targets. It may be the most important vent parameter to minimize.

What is auto-PEEP and when does it occur?

Air trapping due to incomplete exhalation before the next breath -common in COPD/asthma. Causes hemodynamic compromise (reduced venous return) and barotrauma. Detected by expiratory hold maneuver. Treated by reducing RR, increasing I:E ratio (longer expiratory time), and bronchodilators.

The vent is alarming with high peak pressures. How do you troubleshoot?

Peak pressure = airway resistance + compliance + PEEP. High peak + normal plateau (< 30) = airway resistance problem: bronchospasm (give albuterol), mucus plug (suction), kinked ETT, biting tube (bite block/sedation), small ETT. High peak + high plateau (> 30)

What is driving pressure and why is it more important than tidal volume alone?

Driving pressure = Plateau pressure − PEEP. It represents the actual distending pressure applied to the lung parenchyma. Goal: < 15 cmH₂O. A landmark meta-analysis by Amato (2015) showed driving pressure was the ventilator variable most strongly associated with survival in ARDS -more predictive than tidal volume or plateau pressure alone.

📋 Daily Vent Check Presentation

"Mr. Patel is intubated day 3 for hypoxemic respiratory failure from aspiration pneumonia. Current vent settings: AC/VC, TV 420 mL (6 mL/kg IBW), RR 18, PEEP 8, FiO₂ 0.55. This morning's ABG: pH 7.38, pCO₂ 42, pO₂ 74 -P/F ratio 135, consistent with moderate ARDS. Pplat is 24, driving pressure 16. He had a SAT trial this morning -he was following commands but became tachypneic. We are holding the SBT today and will reassess tomorrow. He is on propofol and fentanyl, RASS −1. Fluid balance is negative 200 mL over the past 24 hours."

Clinical Examples

Case 1: ARDS, Severe Pneumonia

Presentation: 45M admitted with severe bilateral pneumonia and hypoxemic respiratory failure. SpO₂ 82% on 15L NRB, intubated emergently. ABG post-intubation: pH 7.34, PaO₂ 70 on FiO₂ 0.8 → P/F ratio 88 (severe ARDS, <100).

Vent Strategy (ARDSNet): Mode AC/VC. IBW ~63 kg → TV 6 mL/kg IBW = 378 mL (set 380 mL). RR 18, PEEP 12, FiO₂ 0.8. Confirm Pplat after first breath: target <30 cmH₂O. Driving pressure (Pplat − PEEP) target <15 cmH₂O. ARMA, 2000

Escalation: P/F ratio persists <150 after 12–16h on optimized settings → initiate prone positioning for 16h/day. Consider neuromuscular blockade (Cisatracurium (Nimbex)) if severe patient-ventilator dyssynchrony. Repeat ABG 30 min after every vent change.

Teaching point: Always use IBW, not actual body weight, for TV calculation. Over-ventilating causes ventilator-induced lung injury (VILI) and increases mortality, even a few extra mL/kg matters.

Case 2: COPD Exacerbation, Auto-PEEP Risk

Presentation: 68F with severe AECOPD, on BiPAP for 4h with worsening hypercapnia (pH 7.18, pCO₂ 92). BiPAP failure → intubated with RSI using Ketamine (Ketalar) + Succinylcholine (Anectine).

Vent Strategy: Mode AC/VC. TV 6–8 mL/kg IBW. RR 12–14/min (low rate = more time to exhale). High inspiratory flow rate (60–80 L/min) to shorten inspiratory time. Target I:E ratio 1:4 (vs. normal 1:2) to maximize expiratory time and prevent breath stacking. Start PEEP 5.

Auto-PEEP check: Perform end-expiratory hold maneuver, press hold, read auto-PEEP off the ventilator display. Auto-PEEP >5 cmH₂O = air trapping. Treatment: decrease RR, increase expiratory time, aggressive bronchodilators (Albuterol + Ipratropium); if critical, briefly disconnect ETT and allow full passive exhalation.

Permissive hypercapnia: Target pH 7.25–7.35, not a normal pCO₂. Do not raise RR to normalize CO₂, this worsens air trapping. Hemodynamic stability is the goal, not a normal ABG.

Case 3: Ventilator Weaning, SAT + SBT Protocol

Presentation: 55M intubated day 5 for massive PE with hemodynamic instability, now improving. On AC/VC, RR 14, TV 450 mL, PEEP 5, FiO₂ 0.35. SpO₂ 96%, hemodynamically stable, off vasopressors. RASS −1, follows commands, intact cough.

Step 1, SAT (Sedation Vacation): Hold Propofol and Fentanyl infusions every morning. Assess within 30 min: opens eyes to voice, follows commands, breathing comfortably? Fail criteria: agitation, RR >35, SpO₂ <88%, hemodynamic instability → restart sedation at half dose. Girard, 2008

Step 2, SBT (Spontaneous Breathing Trial): SAT passes → switch to PS 5 / PEEP 5 for 30–120 min. Readiness: FiO₂ ≤40%, PEEP ≤8, hemodynamically stable. Pass criteria: RR <35, SpO₂ >90%, no significant accessory muscle use, RSBI (f/VT in L) <105. Example: RR 18, TV 0.45L → RSBI = 40 → pass.

Decision: Passes both SAT + SBT → proceed to extubation. Fails repeatedly (≥3 attempts over multiple days) → discuss tracheostomy to facilitate long-term weaning, reduce dead space, and improve patient comfort.

Monitoring -Mechanical Ventilation

Parameter	Frequency	Target / Action
ABG	30 min after any vent change, then q4–6h	pH, PaCO2, PaO2, P/F ratio. Guides FiO2/PEEP (oxygenation) and RR/TV (ventilation) adjustments.
Daily SBT assessment	Every morning	Assess readiness: FiO2 ≤ 40%, PEEP ≤ 8, hemodynamically stable, no high-dose vasopressors, adequate mental status. RSBI < 105 (RR/TV in liters) predicts successful extubation. Girard, 2008: paired SAT + SBT improves outcomes.
Plateau pressure	q4–6h or with vent changes	Pplat < 30 cmH2O (lung protective). If exceeding → reduce TV, check for pneumothorax, bronchospasm, or mucus plugging.
Driving pressure	q4–6h	Driving pressure < 15 cmH2O (Pplat - PEEP). Strongest predictor of ARDS mortality Amato, 2015. Optimize by adjusting TV and PEEP.
SpO2 / FiO2 trending	Continuous SpO2, track P/F ratio	SpO2 target 88–95% in ARDS, 94–98% otherwise. Worsening P/F may indicate disease progression, fluid overload, or new complication.
Auto-PEEP check	q shift and with clinical concern	Expiratory hold maneuver. Auto-PEEP > 5 = air trapping → increase expiratory time (decrease RR, decrease I:E ratio). Common in COPD/asthma.
Sedation level (RASS)	q4h	Target RASS -2 to 0 (light sedation). Deeper sedation only if specific indication (prone, paralysis, severe agitation). Daily sedation awakening trial (SAT).
Daily SAT + SBT	Every morning	Girard, 2008: paired protocol -SAT first (hold sedation, assess arousal) → if passes → SBT (PS 5–8/PEEP 5 for 30–120 min). Reduces vent days and mortality.
VAE surveillance	Daily	Ventilator-associated events: new/worsening infiltrate, rising FiO2/PEEP after period of stability, fever, purulent secretions. Prevent with: HOB 30-45°, oral care, DVT/PUD prophylaxis, daily SBT.

Every vent day is a bad day. The single best thing you can do for a ventilated patient is liberate them from the ventilator. Daily SAT + SBT is the most evidence-based strategy to shorten ventilator duration.

⚡ Summary

Summary

Initial Settings

AC/VC, TV 6–8 mL/kg IBW, RR 14–18, FiO₂ 1.0 then wean, PEEP 5

ARDS Settings

TV 6 mL/kg IBW, Pplat ≤ 30, driving pressure ≤ 15, PEEP per ARDSnet table

Acute Deterioration

DOPE: Displacement, Obstruction, Pneumothorax, Equipment. Bag first if in doubt.

Weaning

Daily SAT → SBT. RSBI < 105. Pass both → extubate. Coordinate daily.

High Peak / Normal Plat

Airway resistance problem → suction, bronchodilators, reposition tube

High Peak + High Plat

Compliance problem → pneumothorax, ARDS, pulmonary edema. CXR + assess.

📄 One Pager

ICU · Ventilator · One Pager

Mechanical Ventilation

Know your numbers every morning. When in doubt -disconnect and bag. DOPE for acute deterioration. SAT + SBT daily to get them off the vent.

⚙️ Initial Settings

ModeAC/VC (most common)

Tidal volume6–8 mL/kg IBW

Rate14–16 /min

FiO₂1.0 → wean to SpO₂ 94–98%

PEEP5 cmH₂O (start)

🆘 Acute Deterioration -DOPE

D -Displacement (ETT too deep/dislodged)
O -Obstruction (mucus plug, biting)
P -Pneumothorax → needle decompress
E -Equipment failure → bag the patient

📊 Pressure Interpretation

High Peak, Normal Plat: Airway resistance → suction, bronchodilator
High Peak + High Plat: Compliance problem → PTX, ARDS, edema
Driving pressure = Pplat − PEEP. Target ≤ 15.

✅ Weaning -Daily SAT + SBT Girard 2008

Stop sedation daily (SAT)
SBT on CPAP 5 / PS 5–8 for 30–120 min
RSBI < 105 = ready to extubate
Pass both → extubate

📣 Sample Presentation

One-Liner

"Mr. Brown is a 64-year-old intubated for COPD exacerbation with hypercapnic respiratory failure. Currently on AC/VC: TV 450, RR 16, PEEP 5, FiO₂ 30%. Morning ABG: pH 7.38, pCO₂ 52, pO₂ 88."

Key Points to Cover on Rounds

Intubation indication: hypercapnic respiratory failure (pH 7.22, pCO₂ 78 on presentation, failed BiPAP). Current ABG improved: pH 7.38, pCO₂ 52 (his baseline is ~48). Vent: AC/VC, TV 450 mL (6 mL/kg), RR 16, PEEP 5, FiO₂ 30%. Plateau 22, no auto-PEEP. Sedation: propofol off, RASS 0, following commands. SAT passed, SBT with PSV 5/5 × 30 min -RR 18, TV 380, no distress. Plan: extubate today. BiPAP standby. Nebs q4h.

Airway & Ventilator Management