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NLE Respiratory Nursing — Acute Respiratory Failure & ARDSCheat Sheet

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Acute Respiratory Failure & ARDS cheat sheet — the reference card you wish you had on exam day. Condensed from the full study notes, this is the high-yield core of Acute Respiratory Failure & ARDS for NLE Respiratory Nursing. Download, print, revise.

Exam context

For the Philippine Nurse Licensure Examination (PNLE), Professional Regulation Commission (PRC) — Board of Nursing tests Respiratory Nursing under a "Core" label, with Acute Respiratory Failure & ARDS in the 4th slot across 4 chapters. NLE candidates must clear the 75% weighted average with no sub-test below 60% cut on the 2026 paper, which draws about 50 Respiratory Nursing questions. Date to watch: Bi-annual.

Acute Respiratory Failure & ARDS - Cheat Sheet

Your last-minute revision companion for Acute Respiratory Failure, ARDS, Pulmonary Embolism, and Mechanical Ventilation. Covers definitions, ABG values, management priorities, and high-yield NLE facts. Review this 30 minutes before your exam.

Sections

Formulas

Formula

Type I: PaO2 < 60 mmHg (on room air)

Meaning

PaO2 = partial pressure of oxygen in arterial blood; room air = FiO2 21%

Watch Out

Do NOT confuse with Type II. Type I = OXYGENATION problem, NOT a ventilation problem

When To Use

When patient is hypoxaemic but CO2 is normal or LOW

Formula

Type II: PaCO2 > 50 mmHg AND pH < 7.35

Meaning

PaCO2 = partial pressure of CO2 in arterial blood; pH < 7.35 = acidaemia

Watch Out

PaCO2 > 50 alone is NOT Type II if the pH is normal (respiratory adaptation in chronic COPD). MUST have pH < 7.35

When To Use

When patient retains CO2 and is acidotic — the ventilation has FAILED

Common Values

Value

80–100 mmHg

Symbol

PaO2

Quantity

PaO2 (normal)

Value

35–45 mmHg

Symbol

PaCO2

Quantity

PaCO2 (normal)

Value

7.35–7.45

Symbol

Quantity

pH (normal arterial)

Value

22–26 mEq/L

Symbol

HCO3-

Quantity

HCO3- (normal)

Value

88–92% (NOT > 94%)

Symbol

SpO2

Quantity

SpO2 (target in Type II CO2 retainer)

Section Title

Acute Respiratory Failure: Types & Definitions

Important Facts

**Restlessness and CHANGE IN MENTAL STATUS are the EARLIEST signs of hypoxaemia** — NOT cyanosis, NOT bradycardia
Early hypoxaemia: restlessness, agitation, anxiety, tachypnoea, tachycardia, hypertension
Hypercapnia: headache, drowsiness, confusion, CO2 narcosis (decreased LOC), warm flushed skin, bounding pulse
Late/ominous signs: cyanosis, bradycardia, dysrhythmias, severe decreased LOC, respiratory arrest
ABG is the DEFINING diagnostic test — must be serial to track trend
Type I → oxygen INCREASES oxygenation (not shunt-based); Type II → oxygen is cautious in CO2 retainers (risk of removing hypoxic drive)

Key Definitions

Term

Acute Respiratory Failure

Example

Pneumonia causing Type I failure (hypoxaemia), or opioid overdose causing Type II (CO2 retention)

Definition

Inability of the lungs to maintain adequate gas exchange, defined by ABG criteria (Type I: PaO2 < 60 mmHg; Type II: PaCO2 > 50 mmHg + pH < 7.35).

Term

Type I (Hypoxaemic) Failure

Example

ARDS, pneumonia, pulmonary oedema, pulmonary embolism

Definition

PaO2 < 60 mmHg on room air; the lung CANNOT OXYGENATE blood properly (V/Q mismatch, shunt, diffusion impairment).

Term

Type II (Hypercapnic) Failure

Example

COPD exacerbation, drug overdose, neuromuscular disease (Guillain-Barré, myasthenia gravis), chest-wall deformity

Definition

PaCO2 > 50 mmHg with pH < 7.35; the lung CANNOT VENTILATE (remove CO2) adequately.

Term

V/Q Mismatch

Example

ARDS, atelectasis, pneumonia

Definition

Blood perfuses alveoli that are not ventilated, or ventilated alveoli are not perfused; causes hypoxaemia unresponsive to low O2.

Term

Shunt

Example

ARDS (intrapulmonary shunt), right-to-left cardiac shunt (cyanotic heart disease)

Definition

Deoxygenated blood bypasses ventilated alveoli and returns to systemic circulation; refractory to O2 therapy.

Diagrams To Know

ABG interpretation algorithm (acute vs chronic; respiratory vs metabolic)
Mechanisms of hypoxaemia (hypoventilation, diffusion impairment, V/Q mismatch, shunt, low FiO2)
Breathing pattern changes in respiratory failure (early tachypnoea → late bradypnoea)

Common Values

Value

< 18 mmHg

Symbol

PCWP

Quantity

Pulmonary capillary wedge pressure (PCWP) in ARDS

Value

~6 mL/kg of predicted body weight

Symbol

Quantity

Tidal volume in ARDS lung-protective ventilation

Value

< 30 cm H2O

Symbol

Pplat

Quantity

Plateau pressure target (to avoid barotrauma)

Section Title

Acute Respiratory Distress Syndrome (ARDS)

Important Facts

**Most common ARDS trigger: SEPSIS** (followed by aspiration, trauma, pancreatitis, near-drowning, massive transfusion, transfusion-related acute lung injury — TRALI)
**Hallmark: REFRACTORY HYPOXAEMIA** — does NOT improve with supplemental O2 (because it is shunt, not V/Q mismatch)
Pathophysiology: Trigger → diffuse alveolar–capillary damage → protein-rich oedema floods alveoli → surfactant loss → atelectasis → V/Q mismatch + shunt
Onset: rapidly progressive over HOURS to a few DAYS after the inciting event
Chest X-ray: **bilateral diffuse 'white-out' infiltrates**, 'ground-glass' appearance (NOT focal, NOT unilateral)
ABG: early **respiratory alkalosis** (hyperventilation) → progresses to **respiratory acidosis** as patient tires
Oedema is **NON-CARDIOGENIC** — normal PCWP (< 18 mmHg) on Swan-Ganz catheter distinguishes from cardiogenic pulmonary oedema
ARDS is a clinical diagnosis; no specific laboratory test confirms it (ABG, CXR, clinical context)

Key Definitions

Term

ARDS (Acute Respiratory Distress Syndrome)

Example

Sepsis-induced ARDS (most common), aspiration pneumonia, massive transfusion, severe trauma

Definition

Severe, acute, diffuse inflammatory lung injury characterised by refractory hypoxaemia, non-cardiogenic pulmonary oedema, and bilateral infiltrates on chest X-ray.

Term

Refractory Hypoxaemia

Example

PaO2 remains < 60 mmHg even on FiO2 100% or non-rebreather mask

Definition

Hypoxaemia that does NOT improve despite high-concentration supplemental oxygen (shunt-based); the hallmark of ARDS.

Term

Non-cardiogenic Pulmonary Oedema

Example

Protein-rich fluid floods alveoli despite normal cardiac function and normal pulmonary capillary wedge pressure (PCWP < 18 mmHg)

Definition

Pulmonary oedema due to INCREASED CAPILLARY PERMEABILITY (not elevated hydrostatic pressure); occurs in ARDS.

Term

Surfactant Loss

Example

Stiff lungs that are difficult to ventilate; require higher pressures or PEEP to keep open

Definition

In ARDS, inflammatory damage destroys surfactant-producing cells; alveoli collapse (atelectasis), reducing lung compliance and worsening hypoxaemia.

Diagrams To Know

ARDS pathophysiology cascade: trigger → endothelial damage → increased permeability → protein-rich oedema → surfactant loss → atelectasis → hypoxaemia
Difference between ARDS (non-cardiogenic) and cardiogenic pulmonary oedema (PCWP, CXR pattern, treatment)

Common Values

Value

5 cm H2O

Symbol

PEEP

Quantity

PEEP (low)

Value

10–15 cm H2O

Symbol

PEEP

Quantity

PEEP (moderate-severe ARDS)

Value

< 30 cm H2O

Symbol

Pplat

Quantity

Plateau pressure target

Value

≤ 0.60 (60%)

Symbol

FiO2

Quantity

FiO2 (wean toward)

Section Title

ARDS Management: Mechanical Ventilation & PEEP

Important Facts

**Nearly ALL ARDS patients require mechanical ventilation with PEEP** — spontaneous breathing cannot maintain oxygenation
**PEEP is the cornerstone of ARDS ventilation** — keeps alveoli open at end-expiration, recruits collapsed alveoli, improves shunt
Excessive PEEP → decreases venous return → ↓ cardiac output → hypotension (monitor haemodynamics)
**Lung-protective ventilation reduces mortality in ARDS** — lower tidal volumes, lower plateau pressure (< 30 cm H2O)
**Prone positioning improves oxygenation** in moderate-to-severe ARDS by redistributing perfusion and improving V/Q matching; consider early
Wean PEEP gradually as oxygenation improves — do not reduce too rapidly (risk of alveolar collapse)
ARDS is progressive — compliance often worsens before improving; expect plateau pressures to increase despite lung-protective strategy
Treat the UNDERLYING CAUSE** (e.g., antibiotics for sepsis, source control) — mechanical ventilation buys time

Key Definitions

Term

PEEP (Positive End-Expiratory Pressure)

Example

Typical PEEP 5–15 cm H2O; higher in severe ARDS (up to 20 cm H2O with recruitment manoeuvres)

Definition

Positive pressure maintained at the END of expiration to keep collapsed alveoli open and improve oxygenation.

Term

Lung-Protective Ventilation

Example

ARDSNet protocol: Vt 6 mL/kg, Pplat < 30 cm H2O, PEEP 5–15 based on severity

Definition

Low tidal volumes (~6 mL/kg of predicted body weight) + PEEP to minimize barotrauma/volutrauma and improve survival in ARDS.

Term

Barotrauma / Volutrauma

Example

High-pressure alarm with pneumothorax in a ventilated ARDS patient

Definition

Lung injury caused by excessive pressure (barotrauma) or excessive tidal volumes (volutrauma) during mechanical ventilation; risk of pneumothorax.

Term

Prone Positioning

Example

30+ minutes of prone positioning per session in moderate-to-severe ARDS can improve PaO2 by 20–30%

Definition

Turning the patient face-down while intubated to improve V/Q matching and oxygenation in moderate-to-severe ARDS.

Diagrams To Know

PEEP effect: alveolar recruitment curve (low PEEP = some alveoli closed; optimal PEEP = recruitment; excessive PEEP = overdistension)
ARDSNet lung-protective ventilation protocol flowchart

Common Values

Value

< 500 ng/mL (varies by lab)

Symbol

D-dimer

Quantity

D-dimer (normal, excludes PE)

Section Title

Pulmonary Embolism (PE)

Important Facts

**Classic presentation: sudden-onset dyspnoea, pleuritic chest pain, tachycardia, tachypnoea, anxiety, sense of IMPENDING DOOM**
**Risk factors: Virchow's Triad** — stasis (immobility, post-op, prolonged travel), hypercoagulability (cancer, pregnancy, OCP, dehydration), endothelial injury (trauma, surgery, central lines)
**Most common source of PE: DVT from legs/pelvis**; also fat embolism (trauma), air embolism, amniotic fluid
**Gold-standard diagnostic test: CT pulmonary angiography (CTPA)**
**D-dimer:** HIGH = non-specific (many causes); NORMAL = helps RULE OUT PE in low-risk patients
ABG: usually **hypoxaemia + respiratory alkalosis (low CO2 from hyperventilation)**
ECG findings: typically **sinus tachycardia**; classic 'S1Q3T3' (tall S wave in I, Q wave in III, T-wave inversion in III) is UNCOMMON
Haemoptysis, low-grade fever may occur (infarction if distal PE)
Look for **coexisting DVT** (unilateral calf swelling, warmth, tenderness, positive Homan's/Wells score)

Key Definitions

Term

Pulmonary Embolism (PE)

Example

DVT from the leg travels to pulmonary artery; causes acute dyspnoea, hypoxaemia, shock

Definition

Obstruction of the pulmonary artery or a branch, usually by a thrombus that dislodges from a deep vein (DVT) and lodges in the lungs.

Term

Virchow's Triad

Example

Post-operative immobility (stasis) + surgery (injury) + oral contraceptive use (hypercoagulability) = high PE risk

Definition

Three factors that predispose to thrombus formation: **venous stasis** (immobility), **hypercoagulability** (cancer, pregnancy, oral contraceptives), **endothelial injury** (trauma, surgery, lines).

Term

Massive PE

Example

Acute severe dyspnoea, hypotension, elevated JVP, right-heart strain on ECG, cardiopulmonary collapse

Definition

PE with haemodynamic instability (hypotension, syncope, shock, signs of right-heart strain); requires aggressive management (thrombolytics or embolectomy).

Diagrams To Know

PE risk assessment: Virchow's Triad + clinical presentation → CTPA/D-dimer
Haemodynamic classification of PE: massive (unstable) vs submassive vs low-risk

Section Title

PE Management & Anticoagulation

Important Facts

**PE priority: OXYGEN + elevate head of bed + reassurance + anticoagulation**
**Anticoagulation is the mainstay** — prevents clot propagation and allows natural fibrinolysis
**Thrombolytics ONLY for massive (unstable) PE** — haemodynamic instability (hypotension, shock), right-heart strain, high mortality risk
**Prevention is heavily tested:** early ambulation, compression stockings, intermittent pneumatic compression (IPC), prophylactic anticoagulation in at-risk patients
**Post-operative PE prophylaxis:** mechanical (early ambulation, compression) + pharmacological (enoxaparin, fondaparinux) depending on risk
**Watch for pulmonary infarction:** distal PE may cause infarction → pleuritic pain, haemoptysis, pleural effusion (days later)

Key Definitions

Term

Anticoagulation

Example

Patient with PE starts unfractionated heparin IV, transitions to warfarin (or DOAC) for long-term therapy

Definition

Using drugs (heparin, warfarin, DOACs) to prevent thrombus formation and progression; the mainstay of PE treatment.

Term

Thrombolytics (Fibrinolytics)

Example

Unstable PE with hypotension and shock → consider alteplase infusion

Definition

Drugs (alteplase, streptokinase) that dissolve existing clots; reserved for **massive PE with haemodynamic instability** due to high bleeding risk.

Term

IVC Filter

Example

PE patient with active bleeding or severe thrombocytopenia (cannot anticoagulate) → IVC filter

Definition

Mechanical device placed in the inferior vena cava to trap emboli and prevent PE; used when anticoagulation is contraindicated.

Diagrams To Know

PE treatment algorithm: massiveUnstable (thrombolytics) vs submassive/low-risk (anticoagulation)
DVT/PE prophylaxis protocol by risk category

Common Values

Value

1.5–2.5x control (usually 60–80 seconds)

Symbol

aPTT

Quantity

aPTT target (on heparin)

Value

2.0–3.0

Symbol

INR

Quantity

PT/INR target (warfarin for PE/DVT)

Value

≥ 100K (watch for drop > 50% or < 100K → suspect HIT)

Symbol

Plt

Quantity

Baseline platelet count (before heparin)

Value

80 U/kg IV

Symbol

UFH dose

Quantity

Heparin bolus (UFH)

Value

1 mg per 100 U heparin IV slow

Symbol

Protamine

Quantity

Protamine dose

Section Title

Anticoagulant Drugs: Pharmacology & Monitoring

Important Facts

**Heparin (UFH & LMWH): watch for HIT** — monitor platelets (baseline, Day 3–5, Day 10); platelet drop of > 50% or absolute < 100K is suspicious
**Heparin antidote: Protamine sulfate** (1 mg per 100 U heparin IV slow); gives within 15 min of last heparin dose
**Warfarin: SLOW onset (2–5 days)** — overlap with heparin for ≥5 days AND until INR 2.0–3.0 for ≥24 hours
**Warfarin interactions:** alcohol, NSAIDs, antibiotics, statins, azole antifungals ↑ INR; vitamin K, barbiturates ↓ INR
**Warfarin patient teaching:** maintain CONSISTENT vitamin-K intake (green leafy vegetables), avoid binge drinking, many drug interactions, monthly INR checks
**Warfarin antidote: Vitamin K** (10 mg IV slow over 1–2 hours, or oral if minor bleeding); also fresh frozen plasma (FFP) or prothrombin complex concentrate (PCC) for major bleeding
**DOACs: fixed dosing, no monitoring, but NO antidote** (except dabigatran → idarucizumab); easier for patient compliance
**BLEEDING is the key adverse effect of ALL anticoagulants** — teach signs (bruising, bleeding gums, blood in urine/stool), use soft toothbrush, electric razor, avoid trauma

Key Definitions

Term

Unfractionated Heparin (UFH)

Example

Patient with PE: UFH bolus 80 U/kg IV, then infusion; draw aPTT at 6 hours, adjust rate; monitor for HIT

Definition

IV anticoagulant with immediate onset; requires aPTT monitoring (target 1.5–2.5x control); reversed by protamine sulfate.

Term

Low-Molecular-Weight Heparin (LMWH, e.g., Enoxaparin)

Example

Enoxaparin 1 mg/kg SC q12h; check baseline and follow-up creatinine (renal clearance); also reversed by protamine

Definition

Subcutaneous anticoagulant with more predictable kinetics; usually NO routine aPTT monitoring; reversed partially by protamine.

Term

Warfarin

Example

Start warfarin on Day 1 (overlap with heparin for ≥5 days and until INR 2.0–3.0 for ≥24 hours); long-term therapy; teach consistent vitamin-K intake

Definition

Oral anticoagulant with delayed onset (2–5 days); monitored by PT/INR (target 2.0–3.0 for PE/DVT); reversed by vitamin K.

Term

Direct Oral Anticoagulants (DOACs)

Example

Rivaroxaban 15 mg once daily after DVT/PE; simpler than warfarin; dabigatran reversed by idarucizumab

Definition

Oral anticoagulants (rivaroxaban, apixaban, dabigatran) with fixed dosing and predictable pharmacokinetics; no routine INR monitoring.

Term

Heparin-Induced Thrombocytopenia (HIT)

Example

Patient on UFH: platelets drop from 200 to 80K on Day 5 → stop heparin immediately, check HIT antibody (4Ts score), switch to DTI or argatroban

Definition

Immune reaction to heparin causing platelet aggregation, thrombocytopenia, and paradoxical thrombosis; occurs 3–10 days after heparin start.

Diagrams To Know

Anticoagulant choice flowchart (UFH vs LMWH vs warfarin vs DOAC based on indication, renal function, compliance)
HIT timeline: days 3–10 after heparin start; platelet count drops; stop heparin; switch to DTI

Common Values

Value

~6 mL/kg of predicted body weight

Symbol

Quantity

Tidal volume (lung-protective in ARDS)

Value

12–16 breaths/min (adjust for patient tolerance)

Symbol

Quantity

Respiratory rate

Value

5 cm H2O

Symbol

PEEP

Quantity

PEEP (general)

Value

0.40–1.0 (40–100%), then wean to 0.40–0.60

Symbol

FiO2

Quantity

FiO2 (initial in severe hypoxaemia)

Value

21–23 cm at the teeth

Symbol

ETT depth

Quantity

ETT depth (oral, adult male)

Section Title

Mechanical Ventilation Basics & Nursing Care

Important Facts

**Confirm & secure the endotracheal tube:** bilateral equal breath sounds, capnography (ETCO2 detection), chest X-ray (tip above carina, ~2 cm from entrance to trachea)
**Keep manual resuscitation (bag-valve-mask) bag at the bedside** — ready for accidental extubation or ventilator failure
**Suction ONLY as needed** (not routine schedule); hyperoxygenate before suctioning (100% O2 × 30 sec); limit pass to 10–15 seconds
**VAP (Ventilator-Associated Pneumonia) prevention bundle:**
— Elevate head of bed 30–45° (prevent gastric reflux and aspiration)
— Daily sedation interruption + readiness-to-wean assessment (spontaneous breathing trial, extubation criteria)
— Oral care with chlorhexidine 0.12% rinse twice daily
— DVT prophylaxis (compression, early ambulation, prophylactic anticoagulation)
— Stress-ulcer prophylaxis (H2 blocker or PPI)
**High-pressure alarm:** suggests OBSTRUCTION — check for secretions (suction), kinked tubing, patient biting tube, or bronchospasm; may need sedation or neuromuscular blockade
**Low-pressure alarm:** suggests LEAK or DISCONNECTION — check tubing circuit, cuff, connections; if unsure, **manually ventilate with bag-valve-mask and call for help**
**NEVER ignore an alarm** — always assess the patient first, then the machine
**Wean O2 first, then pressure/volume, then rate**; gradual weaning prevents rebound hypoxaemia and respiratory muscle fatigue
Patient cannot speak with ETT; provide communication method (writing pad, eye blink, yes/no cards); involve family

Key Definitions

Term

FiO2 (Fraction of Inspired Oxygen)

Example

Room air = 0.21; non-rebreather = up to 0.95; mechanical ventilator can deliver 0.21–1.0

Definition

Proportion of oxygen in the inspired air delivered by the ventilator; expressed as decimal (0.21 = 21% = room air) or percentage.

Term

Tidal Volume (Vt)

Example

Patient 70 kg: Vt = 6 mL/kg × 70 = 420 mL per breath

Definition

Volume of air delivered by the ventilator with each breath; set on the ventilator (usually 400–600 mL, or ~6 mL/kg in lung-protective strategy).

Term

Respiratory Rate (RR)

Example

Mode: A/C with RR 14; ventilator delivers 14 breaths/min if patient doesn't exceed that

Definition

Number of breaths delivered per minute by the ventilator (or patient's spontaneous rate); typically 12–16 breaths/min.

Term

Ventilator Mode

Example

A/C 12: 12 supported breaths/min; if patient breathes faster, all breaths are supported. SIMV 8: 8 breaths supported; patient can breathe spontaneously beyond 8

Definition

How the ventilator assists breathing: assist-control (A/C, every breath supported), SIMV (some breaths supported, some spontaneous), pressure support (PS, patient initiates, ventilator supplies pressure).

Diagrams To Know

ETT placement verification: bilateral breath sounds, capnography, chest X-ray
Ventilator alarm response flowchart (high pressure vs low pressure → troubleshooting steps)
Weaning protocol: daily spontaneous breathing trial, extubation readiness criteria

Common Values

Value

≥ 94%

Symbol

SpO2

Quantity

SpO2 target (most patients)

Value

88–92%

Symbol

SpO2

Quantity

SpO2 target (COPD/Type II CO2 retainer)

Value

20–30 cm H2O

Symbol

Pcuff

Quantity

ETT cuff pressure (to prevent aspiration & erosion)

Value

> 35 breaths/min (sign of severe distress or impending failure)

Symbol

Quantity

RR (critical high)

Value

< 8 breaths/min (sign of respiratory depression; intubation indicated)

Symbol

Quantity

RR (critical low)

Section Title

Nursing Assessment & Interventions in Respiratory Failure

Important Facts

**Priority Maslow assessment: Airway → Breathing → Circulation**
**RESTLESSNESS is the FIRST sign of hypoxaemia** — assess mental status (change = hypoxaemia until proven otherwise)
**Use SBAR handover:** Situation (what happened), Background (relevant hx), Assessment (your impression), Recommendation (action needed)
**Positioning:** upright (Fowler's 45–90°) for all respiratory patients; allows gravity to assist breathing, improves V/Q matching
**Oxygen therapy:** titrate to achieve SpO2 ≥ 94% in most patients; exceptions: Type II (CO2 retainer) target 88–92%; avoid removing hypoxic drive
**Monitor vital signs continuously:** RR (↑ early sign of distress), HR (↑ with hypoxaemia), BP (↓ in shock/tension pneumothorax), SpO2 (≥ 94%, ≤ 88–92% in CO2 retainers)
**Frequent ABG draws** in acute failure: initial, after intervention, q1–2h if unstable; **always assess for trends, not isolated values**
**Protect the airway:** keep NPO if intubation expected; suction mouth regularly; maintain ETT cuff (20–30 cm H2O to prevent aspiration and tube erosion)
**Prepare for intubation:** have airway equipment ready (laryngoscope, blades, ETTs of various sizes, stylet, manual resuscitation bag), know the indication (hypoxaemia not responding to O2, inability to protect airway, RR < 8 or > 35, exhaustion)

Key Definitions

Term

Accessory Muscle Use

Example

Patient in respiratory failure: intercostal retractions, suprasternal retractions, abdominal paradox

Definition

Recruitment of sternocleidomastoid, scalene, and abdominal muscles during breathing; sign of respiratory distress and increased work of breathing.

Term

Work of Breathing (WOB)

Example

ARDS patient: stiff lungs (low compliance) → high WOB → muscle fatigue → respiratory failure

Definition

Energy expended to breathe; increases with airway obstruction, decreased compliance, or increased minute ventilation.

Term

Respiratory Muscle Fatigue

Example

Patient with Type II failure tiring out → RR decreases, CO2 rises further, LOC decreases → intubation needed

Definition

Inability of the respiratory muscles (diaphragm, intercostals) to sustain breathing due to excessive work and inadequate oxygen/nutrient supply.

Diagrams To Know

Respiratory distress assessment: RR, use of accessory muscles, stridor, ability to speak full sentences, mental status
Intubation readiness: indication, equipment, patient position, post-intubation care

Section Title

Patient Education & Prevention in PE/DVT

Important Facts

**Anticoagulant safety teaching (for PE/DVT patients):**
— Report unusual bleeding (nosebleeds, bleeding gums, blood in urine/stool, large bruises)
— Take dose at the same time daily (especially warfarin for consistency)
— Keep INR monitoring appointments (warfarin every 2–4 weeks, then monthly)
— Maintain CONSISTENT vitamin-K intake (avoid binge eating/avoiding green vegetables)
— Avoid NSAIDs and alcohol unless approved by provider
— Wear medical alert bracelet (on anticoagulant)
**DVT/PE prevention for patient:**
— Stay mobile; do NOT sit for long periods (> 2 hours without movement)
— Ankle pumping exercises on long flights/car rides (10 reps, q30 min)
— Stay hydrated (8–10 glasses water/day)
— Wear prescribed compression stockings correctly (put on before getting out of bed)
— Elevate legs when resting
**Ventilated patient communication:** explain the tube (cannot speak but can hear), importance of sedation/analgesia, that family can visit/talk, expected duration

Key Definitions

Term

Thromboembolism Prophylaxis

Example

Post-operative patient: early ambulation + compression stockings + enoxaparin SC q12h

Definition

Preventive measures (mechanical and/or pharmacological) to reduce the risk of DVT and PE in hospitalized or high-risk patients.

Term

Compression Stockings / Intermittent Pneumatic Compression (IPC)

Example

Sequential IPC devices applied to legs during and after surgery to prevent DVT

Definition

Mechanical devices that enhance venous return by external compression; used to prevent stasis.

Diagrams To Know

PE risk stratification: Wells score, revised Geneva score (for clinical assessment of PE probability)

Must Remember

**Type I failure = PaO2 < 60 mmHg (oxygenation problem); Type II = PaCO2 > 50 + pH < 7.35 (ventilation problem).** Know the difference — it changes management (high O2 vs controlled O2 + ventilation support).
**RESTLESSNESS & CHANGE IN MENTAL STATUS are the EARLIEST signs of hypoxaemia.** Do NOT wait for cyanosis or bradycardia; those are LATE, ominous signs.
**ARDS hallmark = REFRACTORY HYPOXAEMIA** (does NOT improve with supplemental O2) + bilateral 'white-out' infiltrates + non-cardiogenic (PCWP < 18 mmHg). Most common trigger = SEPSIS.
**PEEP keeps alveoli open at end-expiration and improves oxygenation in ARDS.** Lung-protective ventilation uses low Vt (~6 mL/kg) to avoid barotrauma. Excessive PEEP → decreased venous return & hypotension.
**PE classic presentation = sudden dyspnoea, pleuritic chest pain, tachycardia, anxiety, impending doom.** Risk = Virchow's Triad (stasis, hypercoagulability, endothelial injury). Gold standard = CTPA. Priority = O2 + head elevation + anticoagulation.
**Anticoagulant ABCs: Heparin → aPTT monitoring (target 1.5–2.5x), antidote protamine, watch HIT. Warfarin → PT/INR (2.0–3.0), antidote vitamin K, manage vitamin-K intake. BLEEDING is the #1 adverse effect of all anticoagulants.**
**Ventilator HIGH-PRESSURE alarm = obstruction (suction/assess); LOW-PRESSURE = leak/disconnection (check circuit).** If unsure → manually ventilate with bag-valve-mask & call for help. NEVER ignore alarms.
**VAP prevention bundle: Head of bed 30–45°, daily sedation break & wean assessment, oral care (chlorhexidine), DVT/stress-ulcer prophylaxis.** Nearly all VAP is preventable.
**ETT verification: bilateral equal breath sounds, capnography (ETCO2), chest X-ray (tip 2 cm above carina).** Keep manual resuscitation bag at bedside. Suction only as needed (hyperoxygenate first, limit 10–15 sec).
**In Type II CO2 retainers (COPD, opioid overdose): target SpO2 88–92% (NOT > 94%).** High O2 may remove hypoxic drive & worsen CO2 retention. Use controlled O2 + BiPAP/intubation if needed.

Last Minute Tips

**When you see 'restlessness/agitation' on an exam, think HYPOXAEMIA first** — it is the earliest sign. Cyanosis & bradycardia come much later. Always assess ABG/SpO2 in an agitated patient.
**ARDS ≠ simple pneumonia.** If the exam says 'bilateral infiltrates + refractory hypoxaemia + normal cardiac function,' it is ARDS. Think sepsis, aspiration, trauma as triggers. The key word = REFRACTORY to O2.
**PE question? Look for Virchow's Triad risk factors** (immobility post-op, OCP, cancer, surgery) + sudden dyspnoea + pleuritic pain + anxiety. If haemodynamically unstable → consider thrombolytics. If stable → anticoagulation.
**Anticoagulant questions: Remember the 'rule of five':** (1) Heparin watch aPTT & HIT; (2) Warfarin watch INR & vitamin K; (3) LMWH no monitoring; (4) DOACs no monitoring & fixed dose; (5) Bleeding is universal risk. Antidotes: protamine (heparin), vitamin K (warfarin).
**Ventilator alarms are high-yield exam material.** High pressure = obstruction (suction it). Low pressure = leak (check tubing). When in doubt on a real patient, manually ventilate with the bag-valve-mask & call for backup. Exam will ask 'what is your FIRST action?' — answer is assess the patient, then the machine.

Comparison Tables

Rows

Values

OXYGENATION fails
VENTILATION fails

Property

Primary problem

Values

< 60 mmHg
Normal or ↑ (but CO2 ↑)

Property

ABG: PaO2

Values

Normal or ↓ (hyperventilation)
> 50 mmHg

Property

ABG: PaCO2

Values

Normal or ↑ (respiratory alkalosis)
< 7.35 (respiratory acidosis)

Property

ABG: pH

Values

YES, improves with supplemental O2 (except shunt)
NO, high O2 does NOT improve; must fix ventilation

Property

Response to O2

Values

V/Q mismatch, shunt, diffusion impairment, low FiO2
Hypoventilation, weak muscles, airway obstruction, depressed drive

Property

Mechanism

Values

Pneumonia, ARDS, PE, atelectasis, cardiogenic oedema
COPD exacerbation, opioid overdose, Guillain-Barré, neuromuscular disease, chest wall deformity

Property

Common causes

Values

Restlessness, agitation, tachycardia, tachypnoea
Headache, drowsiness, confusion, warm flushed skin, bounding pulse

Property

Early signs

Values

HIGH-concentration O2 (non-rebreather, CPAP/BiPAP)
CONTROLLED O2 (target SpO2 88–92%); support ventilation (BiPAP, intubation)

Property

O2 management

Values

O2 + treat cause (antibiotics for pneumonia, etc.)
O2 cautiously + non-invasive/invasive ventilation + treat cause

Property

Treat with

Columns

Feature
Type I (Hypoxaemic)
Type II (Hypercapnic)

Table Title

Type I vs Type II Respiratory Failure

Rows

Values

Increased capillary permeability (non-cardiogenic)
Elevated hydrostatic pressure (heart failure)

Property

Mechanism

Values

< 18 mmHg (normal)
> 18 mmHg (elevated)

Property

PCWP (Swan-Ganz)

Values

Protein-rich (exudate); high protein/plasma protein ratio
Protein-poor (transudate); low protein/plasma ratio

Property

Oedema fluid

Values

Hours to days after trigger (sepsis, aspiration, trauma)
Gradual, related to heart failure progression

Property

Onset

Values

Bilateral diffuse 'white-out', ground-glass (peripheral sparing possible)
Bilateral, often perihilar (batwing pattern), pleural effusions

Property

CXR pattern

Values

REFRACTORY (no improvement with supplemental O2)
Improves with O2 (responsive)

Property

Hypoxaemia response to O2

Values

Sepsis, aspiration, trauma, pancreatitis, near-drowning, massive transfusion
Left ventricular dysfunction, mitral stenosis, fluid overload

Property

Triggers

Values

Mechanical ventilation + PEEP + low Vt + treat cause
Diuretics, ACE inhibitor, vasodilators, mechanical support

Property

Treatment

Columns

Feature
ARDS
Cardiogenic Pulmonary Oedema

Table Title

ARDS vs Cardiogenic Pulmonary Oedema

Rows

Values

IV infusion
Immediate (minutes)
aPTT (target 1.5–2.5x control)
Protamine sulfate
Watch for HIT; expensive; reversible

Property

Unfractionated Heparin (UFH)

Values

SC q12h
2–4 hours
Usually NONE (predictable)
Protamine (partial)
Renal clearance; simpler than UFH; not reversible

Property

LMWH (Enoxaparin)

Values

Oral
2–5 days (slow)
PT/INR (target 2.0–3.0)
Vitamin K (slow) or FFP/PCC (fast)
Overlap with heparin ≥5 days; many drug interactions; vitamin K foods matter

Property

Warfarin

Values

Oral
Rapid (hours)
NONE (fixed dose)
Idarucizumab (dabigatran only); others = no specific reversal
Simple dosing; good compliance; newer agents

Property

DOAC (Rivaroxaban, Apixaban, Dabigatran)

Columns

Drug
Route
Onset
Monitoring
Antidote
Notes

Table Title

Anticoagulant Drugs: Comparison

Rows

Values

Secretions, kinked tubing, patient biting ETT, bronchospasm, coughing, condensation in circuit
Suction, check tubing, assess breath sounds, consider sedation
Auscultate bilateral breath sounds; check SpO2 & vital signs; if unsure → manually ventilate with bag-valve-mask

Property

HIGH-PRESSURE alarm

Values

Leak in tubing, disconnected circuit, ETT cuff deflated, ETT displacement
Check tubing connections, assess cuff pressure, check ETT position, assess breath sounds
Capnography reading drops (no ETCO2 = disconnection); SpO2 falls; if unsure → manually ventilate with bag-valve-mask

Property

LOW-PRESSURE alarm

Values

Patient disconnected, ventilator malfunction, RR drops below set rate (patient not breathing)
Check connections, assess patient responsiveness, check settings
Patient must be breathing or manually ventilated; call for help if apnoea

Property

Apnoea alarm

Values

O2 source malfunction, tubing disconnected
Check O2 tubing, check wall O2 supply pressure, check ventilator display
Verify SpO2; may need backup O2 source

Property

FiO2 alarm

Columns

Alarm Type
Common Causes
Immediate Action
Assessment

Table Title

Ventilator Alarms: Causes & Actions

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Chronic Obstructive & Restrictive Pulmonary Disorders

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