NLE Respiratory Nursing — Respiratory Assessment & DiagnosticsCheat Sheet
A printable cheat sheet for Respiratory Assessment & Diagnostics, built for NLE reviewers who want one go-to reference in the final stretch. Covers formulas, key definitions, common question types, and the Professional Regulation Commission (PRC) — Board of Nursing-specific twists you will see on NLE day.
Exam context
For the Philippine Nurse Licensure Examination (PNLE), Professional Regulation Commission (PRC) — Board of Nursing tests Respiratory Nursing under a "Core" label, with Respiratory Assessment & Diagnostics in the 1st 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.
Respiratory Assessment & Diagnostics - Cheat Sheet
Your last-minute exam companion for respiratory physical assessment, ABG interpretation, oxygen delivery systems, and chest-tube management. Master the high-yield concepts that appear repeatedly on the NLE.
Sections
Common Values
Value
12–20 breaths/min
Symbol
RR
Quantity
Normal respiratory rate (adult)
Value
~5 g/dL
Symbol
N/A
Quantity
Deoxygenated Hb threshold for visible cyanosis
Section Title
Respiratory Physical Assessment (IPPA)
Important Facts
- Normal adult respiratory rate: 12–20 breaths/min.
- IPPA order is critical: Inspection → Palpation → Percussion → Auscultation (never percuss first).
- Always compare side to side for symmetry and baseline abnormalities.
- Pursed-lip breathing = expiratory braking; slows airflow, reduces air trapping in emphysema.
- Tripod position = severe dyspnoea; patient leans forward on arms to fix chest muscles.
- Nasal flaring + retractions = increased respiratory effort = urgent assessment needed.
Key Definitions
Term
Tactile fremitus
Example
Pneumonia patient with increased fremitus over left lower lobe = consolidation present.
Definition
Vibration felt on chest wall when patient phonates 'ninety-nine'; increases over consolidation, decreases over effusion/pneumothorax.
Term
Accessory muscle use
Example
COPD exacerbation with visible intercostal and subcostal retractions = severe dyspnoea.
Definition
Use of scalene, sternocleidomastoid, and intercostal muscles during breathing; indicates increased work of breathing and respiratory distress.
Term
Barrel chest
Example
Emphysema patient with characteristic barrel chest appearance and pursed-lip breathing.
Definition
Increased anteroposterior (A-P) diameter of thorax from chronic air trapping and loss of elastic recoil.
Term
Cyanosis (central vs peripheral)
Example
Central cyanosis in acute pneumonia with PaO2 <60 mmHg; peripheral cyanosis in cold or shock.
Definition
Central: lips/tongue blue = true hypoxaemia (late sign, needs ~5 g/dL deoxygenated Hb); Peripheral: fingers/toes = poor perfusion.
Term
Clubbing
Example
Bronchiectasis or lung cancer patient with digital clubbing.
Definition
Finger/toe enlargement from chronic hypoxaemia; indicates long-standing respiratory or cardiac disease.
Diagrams To Know
- Normal vs abnormal breath sound waveforms
- Thoracic anatomy: lobes, segments, landmarks (2nd intercostal = sternal angle)
Section Title
Breath Sounds & Adventitious Findings
Important Facts
- Crackles = FLUID or ATELECTASIS; wheezes = AIRWAY NARROWING.
- Stridor = immediate airway emergency; prepare for intubation.
- Bilateral symmetric wheezes in asthma; unilateral/asymmetric findings suggest lobar disease.
- Absent breath sounds = severe obstruction, pleural effusion, pneumothorax, or massive consolidation.
- Egophony: ask patient to say 'E'; if sounds like 'A' = consolidation (increased transmission).
- Whispered pectoriloquy: patient whispers '1–2–3'; normally faint but loud over consolidation.
Key Definitions
Term
Vesicular breath sounds
Example
Expected finding on healthy patient's bilateral lung base assessment.
Definition
Soft, low-pitched, heard over most lung fields; normal.
Term
Bronchovesicular breath sounds
Example
Heard at T1–T4 anteriorly and posteriorly between lobes.
Definition
Intermediate pitch/intensity, heard over main bronchi (paratracheal, between scapulae).
Term
Bronchial/tracheal breath sounds
Example
Bronchial breath sounds in pneumonia over consolidated area = consolidation confirmed.
Definition
Loud, high-pitched, hollow, heard only over trachea; abnormal anywhere else (suggests consolidation).
Term
Crackles (rales)
Example
Fine crackles in pulmonary oedema (heart failure); coarse in pneumonia (secretions).
Definition
Discontinuous, fine popping sounds from fluid in airways or atelectasis (alveoli opening); heard in early inspiration.
Term
Wheezes
Example
Widespread expiratory wheezes in acute asthma attack.
Definition
Continuous, musical, high-pitched; from narrowed airways; typically expiratory but can be biphasic in severe obstruction.
Term
Rhonchi
Example
Patient with pneumonia and thick secretions in bronchi.
Definition
Low-pitched, snoring, rattling; from secretions in large airways; usually clears with cough.
Term
Stridor
Example
Post-extubation stridor from vocal cord swelling or laryngeal oedema.
Definition
High-pitched, crowing sound heard WITHOUT stethoscope; upper-airway obstruction; EMERGENCY.
Term
Pleural friction rub
Example
Pleurisy or pulmonary infarction with pleural irritation.
Definition
Grating, scratchy sound from inflamed pleura (visceral and parietal); worse on deep breathing.
Diagrams To Know
- Breath sound characteristics table (pitch, intensity, duration, location)
- Decision tree: abnormal sound → crackles (fluid/atelectasis) or wheeze (airway) or stridor (upper airway)
Formulas
Formula
ROME Method: Respiratory Opposite, Metabolic Equal
Meaning
CO2 moves OPPOSITE to pH (Respiratory); HCO3 moves SAME direction as pH (Metabolic).
Watch Out
Students often confuse which way CO2 and HCO3 move. REMEMBER: Respiratory Opposite (high CO2 = low pH), Metabolic Equal (low HCO3 = low pH).
When To Use
Every time you interpret ABGs; always interpret pH first, then use ROME.
Common Values
Value
7.35–7.45
Symbol
pH
Quantity
pH
Value
35–45 mmHg
Symbol
PaCO2
Quantity
PaCO2
Value
22–26 mEq/L
Symbol
HCO3
Quantity
HCO3
Value
80–100 mmHg
Symbol
PaO2
Quantity
PaO2
Value
95–100%
Symbol
SaO2
Quantity
SaO2
Section Title
Arterial Blood Gas (ABG) Analysis
Important Facts
- Normal ABG values (MUST MEMORIZE): pH 7.35–7.45, PaCO2 35–45, HCO3 22–26, PaO2 80–100, SaO2 95–100%.
- Always START with pH to determine if acidosis or alkalosis.
- Use ROME: check if the PaCO2 and HCO3 are CONSISTENT with the pH abnormality.
- Look for COMPENSATION: if one system is abnormal, the other may shift to normalize pH.
- Uncompensated: one system abnormal, pH abnormal, no compensation yet.
- Fully compensated: one system abnormal, pH normalized, other system has shifted fully.
- Partially compensated: one system abnormal, pH still abnormal, other system has partially shifted.
- A-a gradient (Alveolar-arterial): calculates expected PaO2; widened gradient = pulmonary disease (not hypoventilation).
- Remember: SpO2 DOES NOT reflect ventilation; normal SpO2 can hide CO2 retention.
Key Definitions
Term
pH
Example
pH 7.30 = acidosis; pH 7.50 = alkalosis.
Definition
Measure of acidity/alkalinity; <7.35 = acidosis, >7.45 = alkalosis, 7.35–7.45 = normal.
Term
PaCO2 (respiratory component)
Example
PaCO2 50 = hypoventilation/CO2 retention (COPD, respiratory depression); PaCO2 30 = hyperventilation.
Definition
Partial pressure of CO2 in arterial blood; 35–45 mmHg normal; reflects ventilation adequacy.
Term
HCO3 (metabolic component)
Example
HCO3 16 = metabolic acidosis (DKA, diarrhoea, shock); HCO3 30 = metabolic alkalosis (vomiting, antacid overdose).
Definition
Bicarbonate; 22–26 mEq/L normal; reflects kidney acid–base regulation and metabolic status.
Term
PaO2 (oxygenation)
Example
PaO2 60 = hypoxaemia; requires oxygen therapy and investigation.
Definition
Partial pressure of oxygen in arterial blood; 80–100 mmHg normal; indicates gas exchange.
Term
SaO2 (oxygen saturation)
Example
SaO2 88% = mild hypoxaemia; SaO2 <80% = severe, life-threatening.
Definition
Percentage of Hb bound to oxygen; 95–100% normal; indirect measure of PaO2.
Term
Respiratory acidosis
Example
COPD exacerbation: pH 7.30, PaCO2 60, HCO3 24 (uncompensated respiratory acidosis).
Definition
pH <7.35 + PaCO2 >45 (high CO2); lungs cannot eliminate CO2; uncompensated if HCO3 normal.
Term
Respiratory alkalosis
Example
Anxiety, pain, early sepsis: pH 7.50, PaCO2 28, HCO3 24.
Definition
pH >7.45 + PaCO2 <35 (low CO2); hyperventilation blows off CO2.
Term
Metabolic acidosis
Example
DKA or lactic acidosis: pH 7.25, PaCO2 32, HCO3 14 (respiratory compensation expected).
Definition
pH <7.35 + HCO3 <22 (low bicarbonate); kidney dysfunction, organic acid accumulation, or loss of base.
Term
Metabolic alkalosis
Example
Post-vomiting or NG suction: pH 7.50, PaCO2 40, HCO3 32.
Definition
pH >7.45 + HCO3 >26 (high bicarbonate); loss of acid or gain of base.
Diagrams To Know
- ABG interpretation flowchart (pH → acid/base → PaCO2/HCO3 direction → diagnosis)
- ROME method quick reference table
Reactions Or Equations
Note
Used to calculate expected PaO2 on room air (FiO2 21%) to detect pulmonary disease.
Equation
Alveolar Gas Equation: PAO2 = (PB − PH2O) × FiO2 − (PaCO2 / R)
Conditions
PB = barometric pressure (760 at sea level), PH2O = water vapour pressure (47 mmHg), R = respiratory quotient (0.8), FiO2 = fraction of inspired oxygen.
Common Values
Value
95–100%
Symbol
SpO2
Quantity
Normal SpO2
Value
90–94%
Symbol
SpO2
Quantity
Mild hypoxaemia
Value
80–89%
Symbol
SpO2
Quantity
Moderate hypoxaemia
Value
<80%
Symbol
SpO2
Quantity
Severe hypoxaemia
Section Title
Pulse Oximetry
Important Facts
- Normal SpO2: 95–100% on room air.
- SpO2 is UNRELIABLE in: poor perfusion, hypothermia, motion, nail polish, carbon monoxide poisoning (falsely elevated), anaemia.
- CRITICAL: SpO2 does NOT measure ventilation; patient can have normal SpO2 while retaining CO2 → always confirm with ABG if concerned.
- Pulse oximetry relies on pulsatile flow; non-pulsatile states (atrial fibrillation, cardiac arrest) may give false readings.
- Carbon monoxide binds Hb with high affinity → SpO2 falsely HIGH; must check carboxyhaemoglobin level.
- In anaemia, SpO2 may appear normal despite inadequate oxygen content because fewer Hb molecules are available to desaturate.
- Rightward shift of Hb-O2 dissociation curve (fever, acidosis, 2,3-DPG ↑) = Hb releases O2 more easily → tissue oxygenation improved despite lower SpO2.
Key Definitions
Term
SpO2 (oxygen saturation via pulse oximetry)
Example
SpO2 94% on room air in healthy patient; SpO2 88% in hypoxaemic COPD.
Definition
Non-invasive estimate of percent Hb saturated with oxygen; normal 95–100%; unreliable in poor perfusion/hypothermia.
Diagrams To Know
- Limitations of SpO2 in various clinical conditions
Formulas
Formula
FEV1/FVC Ratio = (Forced Expiratory Volume in 1 sec) / (Forced Vital Capacity) × 100%
Meaning
FEV1 = volume of air exhaled in first 1 second; FVC = total volume exhaled from maximal inspiration; ratio differentiates obstructive vs restrictive.
Watch Out
REVERSED values between obstruction and restriction are a common exam trap. Remember: Obstruction = FEV1/FVC DOWN (<70%); Restriction = FVC down but ratio normal/HIGH.
When To Use
PFT interpretation; <70% = obstructive disease (asthma, COPD), ≥70% = restrictive disease or normal.
Common Values
Value
≥70% of predicted
Symbol
N/A
Quantity
Normal FEV1/FVC ratio
Value
<70%
Symbol
N/A
Quantity
Obstructive disease FEV1/FVC
Value
Normal/high (≥70%) with low FVC
Symbol
N/A
Quantity
Restrictive disease FEV1/FVC
Value
50–79% predicted
Symbol
N/A
Quantity
Mild COPD FEV1
Value
30–49% predicted
Symbol
N/A
Quantity
Moderate COPD FEV1
Value
<30% predicted
Symbol
N/A
Quantity
Severe COPD FEV1
Value
≥80% personal best
Symbol
PEFR
Quantity
PEFR green zone
Value
50–79% personal best
Symbol
PEFR
Quantity
PEFR yellow zone
Value
<50% personal best
Symbol
PEFR
Quantity
PEFR red zone
Section Title
Pulmonary Function Tests (PFTs) & Spirometry
Important Facts
- FEV1/FVC ratio is the KEY DISCRIMINATOR between obstructive and restrictive patterns.
- Obstructive: FEV1/FVC <70% (airflow limitation); restrictive: FEV1/FVC ≥70% (volume limitation).
- Asthma is reversible obstruction (improves with bronchodilators); COPD is irreversible (no full reversal).
- PEFR traffic-light zones: Green ≥80% personal best = good control; Yellow 50–79% = use reliever; Red <50% = emergency.
- Teach patient to establish personal best PEFR first (when asthma well-controlled), then monitor trends.
- Predicted values vary by age, sex, height, and race; compare patient's result to predicted for their demographics.
- Effort-dependent test; poor effort = falsely low values → may need repeat testing.
Key Definitions
Term
FEV1 (Forced Expiratory Volume in 1 second)
Example
FEV1 75% of predicted = mild obstruction; FEV1 <50% = severe COPD.
Definition
Volume of air forcibly exhaled in first 1 second; indicator of airway resistance and ventilatory power.
Term
FVC (Forced Vital Capacity)
Example
FVC 60% of predicted = restrictive disease (pulmonary fibrosis, obesity).
Definition
Total volume of air that can be forcibly exhaled from maximal inspiration; reduced in restrictive disease.
Term
Obstructive disease
Example
Asthma: low FEV1/FVC; REVERSES with bronchodilator. COPD: low FEV1/FVC; does NOT fully reverse.
Definition
Airflow obstruction on exhalation; FEV1/FVC <70%; examples: asthma, COPD, bronchiectasis.
Term
Restrictive disease
Example
Pulmonary fibrosis: FVC 50% predicted, FEV1/FVC 82% (normal ratio despite low volumes).
Definition
Reduced lung volume capacity; FVC ↓ but FEV1/FVC normal/high; examples: pulmonary fibrosis, chest-wall deformity, obesity.
Term
PEFR (Peak Expiratory Flow Rate)
Example
Patient's personal best PEFR 500 L/min; current reading 380 L/min = 76% = yellow zone (caution).
Definition
Maximum flow rate during forced expiration; used at home in asthma; reported as % of personal best.
Diagrams To Know
- Obstructive vs restrictive PFT pattern comparison
- FEV1/FVC ratio interpretation flowchart
Common Values
Value
21–23 cm (oral); confirm on CXR tip above carina
Symbol
N/A
Quantity
Normal ETT depth from teeth
Section Title
Chest X-Ray (CXR) Assessment
Important Facts
- Always REMOVE metal (jewellery, buttons, zippers) before CXR.
- Confirm patient NOT pregnant or shield appropriately (RA 9173 radiation safety).
- No special preparation; no fasting required.
- Look for ETT/central-line placement: ETT tip should be 2–3 cm above the carina; central line should NOT be in the heart.
- Consolidation = WHITE; hyperinflation = dark/lucent (air-filled); effusion = opaque at base with blunted angle.
- Mediastinal shift = indicates tension (emergency); trachea/heart shifted away from pneumothorax side.
- Bilateral infiltrates = possible pulmonary oedema (heart failure) vs bilateral pneumonia vs ARDS.
- Look for signs of respiratory distress: elevation of hemidiaphragms, mediastinal widening, air bronchograms.
Key Definitions
Term
Consolidation/infiltrate
Example
Right lower lobe pneumonia shows right lower lobe infiltrate.
Definition
White/opaque appearance on CXR from fluid/cells filling alveolar spaces; seen in pneumonia, pulmonary oedema, pulmonary infarction.
Term
Hyperinflation
Example
COPD patient with CXR showing flattened diaphragms and hyperlucent lung fields.
Definition
Increased air in lungs; flattened diaphragms and increased anteroposterior (A-P) diameter on CXR; seen in COPD/emphysema.
Term
Pleural effusion
Example
Heart failure with bilateral pleural effusions; left lower costophrenic angle blunted.
Definition
Fluid accumulation in pleural space; blunted costophrenic angles and fluid level on CXR.
Term
Pneumothorax
Example
Tension pneumothorax: collapsed right lung, trachea shifted left, hypotension, distended neck veins (EMERGENCY).
Definition
Air in pleural space; collapsed lung with visible pleural line and mediastinal shift (if tension).
Term
Atelectasis
Example
Post-operative atelectasis from shallow breathing and secretion retention.
Definition
Alveolar collapse; appears as white/opaque area; caused by obstruction, compression, or loss of surfactant.
Diagrams To Know
- Normal CXR landmarks and anatomy
- Common pathological CXR findings (consolidation, effusion, pneumothorax, hyperinflation)
Formulas
Formula
FiO2 (Fraction of Inspired Oxygen) by Device
Meaning
Percentage of inspired gas that is oxygen; varies by device and flow rate; critical for matching therapy to patient need.
Watch Out
MOST COMMON ERROR: assuming nasal cannula can deliver high FiO2 (it cannot exceed ~44%), or forgetting that flow >6 L/min does NOT increase FiO2 on nasal cannula. COPD target = 88–92%, NOT 94–98%.
When To Use
Every oxygen order; match FiO2 to patient's oxygenation target (88–92% for COPD, 94–98% for others).
Common Values
Value
24–44% FiO2 at 1–6 L/min
Symbol
N/A
Quantity
Nasal cannula FiO2 range
Value
40–60% FiO2 at 5–10 L/min (min 5 L/min)
Symbol
N/A
Quantity
Simple face mask FiO2 range
Value
60–80% FiO2 at 6–11 L/min
Symbol
N/A
Quantity
Partial rebreather mask FiO2 range
Value
80–95% FiO2 at 10–15 L/min
Symbol
N/A
Quantity
Non-rebreather mask FiO2 range
Value
24%, 28%, 31%, 35%, or 40% (fixed, precise)
Symbol
N/A
Quantity
Venturi mask FiO2 options
Value
88–92% (controlled oxygen)
Symbol
SpO2
Quantity
COPD target SpO2
Value
94–98%
Symbol
SpO2
Quantity
Standard target SpO2 (non-COPD)
Section Title
Oxygen Therapy — Delivery Devices & FiO2
Important Facts
- Oxygen is a DRUG and requires an order in most settings per RA 9173.
- Nasal cannula FiO2: roughly 4% increase per L/min above room air (21%). At 1 L/min ≈ 24%; at 6 L/min ≈ 44%.
- Simple mask MINIMUM 5 L/min to prevent CO2 accumulation in mask dead space.
- Partial/non-rebreather: keep reservoir bag 1/3 to 1/2 full on inspiration; if it completely collapses, increase flow or switch device.
- Non-rebreather is EMERGENCY oxygen; highest concentration available in low-flow systems.
- Venturi mask = precise FiO2; unaffected by respiratory pattern; ideal for controlled oxygen therapy.
- COPD SpO2 TARGET = 88–92% (NOT 94–98%); higher SpO2 can suppress hypoxic drive and cause CO2 retention.
- NEVER fully withhold oxygen from hypoxic patient; instead, titrate carefully and monitor ABGs in COPD.
- Provide HUMIDIFICATION at flows >4 L/min to prevent mucosal drying, nosebleeds, and skin breakdown.
- NO SMOKING / NO OPEN FLAME near oxygen (fire hazard); secure cylinders upright; post signage.
Key Definitions
Term
Nasal cannula
Example
Patient on nasal cannula 3 L/min = ~32% FiO2; comfortable, can eat and talk.
Definition
Low-flow system; delivers 24–44% FiO2 at 1–6 L/min; allows eating/talking; comfortable; flows >6 L/min dry mucosa without increasing FiO2.
Term
Simple face mask
Example
Post-operative patient on simple mask 6 L/min = ~50% FiO2; prevents CO2 rebreathing.
Definition
Low-flow system; delivers 40–60% FiO2 at 5–10 L/min; MINIMUM 5 L/min needed to flush exhaled CO2 from mask.
Term
Partial rebreather mask
Example
Moderate hypoxaemia: partial rebreather 8 L/min with bag maintained at appropriate fill level.
Definition
Low-flow with attached reservoir bag; delivers 60–80% FiO2 at 6–11 L/min; keep bag 1/3 to 1/2 full on inspiration.
Term
Non-rebreather mask
Example
Acute hypoxaemia (PaO2 <60): non-rebreather 15 L/min with bag inflated; emergency oxygen delivery.
Definition
Low-flow, highest concentration; reservoir bag + one-way valves prevent rebreathing; delivers 80–95% FiO2 at 10–15 L/min; bag must STAY INFLATED.
Term
Venturi mask
Example
COPD patient: Venturi mask 28% FiO2 to maintain SpO2 88–92% without suppressing hypoxic drive.
Definition
High-flow, fixed-performance system; delivers PRECISE FiO2 (24%, 28%, 31%, 35%, 40%) regardless of breathing pattern; DEVICE OF CHOICE IN COPD.
Term
Hypoxic drive
Example
COPD patient given 100% O2 → loses hypoxic drive → hypoventilation → CO2 rises dramatically (CO2 narcosis).
Definition
In chronic CO2 retainers (COPD), hypoxaemia is PRIMARY respiratory stimulus (not CO2); excessive oxygen removes this drive → CO2 retention/respiratory depression.
Diagrams To Know
- Oxygen delivery device FiO2 ranges and clinical use selection
- Flow rate titration decision tree (match patient need to device)
Common Values
Value
100–300 mL (more after surgery, less after trauma)
Symbol
N/A
Quantity
Normal drainage first 24 hours
Value
>100 mL/hour or sudden increase
Symbol
N/A
Quantity
Drainage threshold for physician report
Value
Varies; 20–36 Fr; larger for fluid, smaller for air
Symbol
N/A
Quantity
Typical chest tube diameter
Value
At least 30–50 cm below
Symbol
N/A
Quantity
Height of chest tube below insertion site
Section Title
Chest Tubes & Water-Seal Drainage Systems
Important Facts
- TIDALING IS NORMAL; sudden absence may mean lung re-expanded (check patient first) OR tube kinked/clogged (assess immediately).
- Intermittent bubbling on expiration/cough = normal in pneumothorax; continuous bubbling = AIR LEAK (abnormal).
- Keep drainage system BELOW chest level AT ALL TIMES to prevent backflow of fluid into pleura.
- DO NOT routinely clamp, milk, or strip the tube unless specifically ordered by physician.
- Clamping a tube with air leak = TENSION PNEUMOTHORAX RISK → do not clamp without direct order.
- Monitor amount, colour, and rate of drainage; mark level with tape and time q1h initially.
- Assess patient's work of breathing, SpO2, breath sounds, and chest symmetry with each assessment.
- Chest tube DISLODGED: immediately cover site with sterile occlusive dressing taped on 3 SIDES (flutter-valve effect); tape all 4 sides = traps air = tension risk.
- Tube DISCONNECTED from system: submerge tube end in sterile water/saline bottle to re-establish seal; get new system.
- Encourage deep breathing, coughing, incentive spirometry to promote lung re-expansion.
- Report excessive drainage (>100 mL/h), sudden increase, change in colour (fresh blood = active bleed), or new/persistent air leak.
- Manage pain adequately before coughing/movement to maximize cooperation.
- Chest tube removal: usually after air leak stops, drainage minimal (<30 mL/day), and lung well-expanded on CXR; post-removal CXR ordered to rule out re-collapse.
Key Definitions
Term
Chest tube
Example
Pneumothorax or pleural effusion patient with chest tube to drain pleural contents.
Definition
Catheter inserted into pleural space to drain air, fluid, blood, or pus; re-expands lung and restores negative intrapleural pressure.
Term
Three-chamber drainage system
Example
Classic Pleur-Evac or Atrium system used in most hospitals for closed chest drainage.
Definition
Standard water-seal system: collection chamber (drainage), water-seal chamber (one-way valve), suction-control chamber (regulates suction level).
Term
Tidaling (fluctuation)
Example
Gentle tidaling in water-seal chamber = tube patent, normal intrapleural pressure cycling.
Definition
Rise and fall of fluid level in water-seal chamber with each breath; NORMAL and EXPECTED.
Term
Intermittent bubbling in water-seal chamber
Example
Fresh pneumothorax with intermittent bubbling as air is gradually removed.
Definition
Air bubbles intermittently released from pleural space, especially on expiration/cough; NORMAL when air is being evacuated (pneumothorax) or initially post-op.
Term
Continuous bubbling in water-seal chamber
Example
Continuous bubbling in water-seal = systematically check connections, then clamping order to locate leak source.
Definition
Constant stream of bubbles = AIR LEAK; either in patient's lung/insertion site or in tubing/system → MUST FIND AND FIX.
Term
Air leak detection (clamping sequence)
Example
Continuous bubbling: clamp at chest tube insertion, then progressively down tubing; identify where leak is located.
Definition
Clamp progressively from patient toward drainage unit; if bubbling stops, leak is between clamp and patient; if continues, leak is in system.
Term
Tension pneumothorax
Example
Clamped chest tube with ongoing air leak → pressure builds → sudden deterioration with hypotension, JVD, tracheal deviation.
Definition
One-way leak allows air INTO pleural space but not OUT; causes complete lung collapse, mediastinal shift, hypotension, distended neck veins, absent breath sounds, tracheal deviation → CARDIAC ARREST EMERGENCY.
Diagrams To Know
- Three-chamber drainage system diagram with normal vs abnormal findings
- Chest tube troubleshooting flowchart (tidaling absent? Bubbling continuous? Drainage excessive?)
- Air leak detection clamping sequence
Section Title
Arterial Puncture & ABG Collection
Important Facts
- ALWAYS perform Allen test BEFORE radial artery puncture to confirm collateral circulation.
- Preferred puncture sites: radial (wrist), femoral (groin), brachial (elbow) in order of preference.
- AFTER puncture: apply firm pressure for AT LEAST 5 MINUTES (longer if patient on anticoagulants) to prevent haematoma/complications.
- Use heparinized syringe (1–2 mL heparin); flush to coat syringe and expel excess heparin (excess heparin falsely lowers PaCO2).
- Collect 2–3 mL of blood; no air bubbles (air changes PaO2); expel any air immediately.
- SEAL syringe cap immediately to prevent gas exchange with room air.
- Transport to lab IMMEDIATELY or place on ice (slows metabolism, prevents time-dependent changes in pH/PaCO2).
- Label with patient name, time collected, FiO2, temperature, and anticoagulant therapy.
- Note respiratory rate, oxygen therapy, and any sedation as these affect results.
Key Definitions
Term
Allen test
Example
Compress both radial and ulnar arteries, ask patient to make fist (blanches hand), release ulnar pressure; if hand flushes in <5 sec, test positive (safe for radial puncture).
Definition
Bedside test to confirm ulnar artery collateral flow before radial artery puncture; prevents hand ischaemia if radial artery injured.
Diagrams To Know
- Allen test positive vs negative findings
- Correct arterial puncture technique
Common Values
Value
>50% FiO2 for >24–48 hours = risk of toxicity
Symbol
N/A
Quantity
Critical oxygen exposure time
Section Title
Complications of Respiratory Conditions & Oxygen Therapy
Important Facts
- Oxygen toxicity risk increases with high FiO2 AND prolonged duration; >50% FiO2 for >48 hours is concerning.
- Prevent absorption atelectasis with PEEP, frequent position changes, incentive spirometry.
- CO2 narcosis is a medical emergency in COPD; reduce oxygen immediately to target SpO2 88–92% and consider non-invasive ventilation.
- Tension pneumothorax is a CARDIAC ARREST-LEVEL EMERGENCY; immediate needle decompression (2nd intercostal space midclavicular line) followed by chest tube insertion.
- Mucosal drying and nosebleeds from high-flow oxygen without humidification; add humidifier at flows >4 L/min.
- Skin breakdown behind ears and over nose from face mask; use protective padding, rotate masks, relieve pressure regularly.
- Aspiration risk increases with decreased consciousness, supine position, and endotracheal intubation; maintain aspiration precautions.
Key Definitions
Term
Oxygen toxicity
Example
Patient on 100% O2 for >48 hours may develop oxygen toxicity; switch to lower FiO2 or switch support modality (e.g., non-invasive ventilation).
Definition
Lung injury from prolonged exposure to high FiO2 (>50% for >24–48 hours); causes substernal discomfort, dry cough, decreased vital capacity, worsening gas exchange.
Term
Absorption atelectasis
Example
High-flow oxygen without PEEP can predispose to atelectasis; use appropriate PEEP to recruit alveoli.
Definition
Alveolar collapse from absorbed gases when breathing high-concentration oxygen; occurs because N2 (normally holds alveoli open) is replaced by O2 (rapidly absorbed into blood).
Term
CO2 narcosis
Example
COPD patient on 100% O2 → suppressed hypoxic drive → hypoventilation → CO2 rises → develops confusion and lethargy.
Definition
CNS depression from elevated CO2; manifests as drowsiness, headache, confusion, asterixis (flapping tremor); seen in severe CO2 retainers given excessive oxygen.
Term
Tension pneumothorax
Example
Post-thoracotomy with clamped chest tube and ongoing air leak → sudden deterioration, hypotension, JVD → requires immediate needle decompression/tube release.
Definition
Air enters pleural space but cannot exit; builds pressure → collapses lung, shifts mediastinum, compresses heart → hypotension, distended neck veins, absent breath sounds, tracheal deviation → CARDIAC ARREST.
Diagrams To Know
- Signs and symptoms of oxygen toxicity and CO2 narcosis
- Tension pneumothorax clinical presentation and emergency management
Must Remember
- NORMAL ABG VALUES (memorize exactly): pH 7.35–7.45, PaCO2 35–45 mmHg, HCO3 22–26 mEq/L, PaO2 80–100 mmHg, SaO2 95–100%. Use ROME: Respiratory Opposite, Metabolic Equal.
- BREATH SOUNDS: Crackles = FLUID (pneumonia, pulmonary oedema); Wheezes = AIRWAY NARROWING (asthma, COPD); Stridor = UPPER-AIRWAY OBSTRUCTION (emergency).
- OXYGEN DEVICES: Nasal cannula 24–44% at 1–6 L/min (flow >6 L/min useless); Simple mask 40–60% at ≥5 L/min; Non-rebreather 80–95% (keep bag inflated); VENTURI = PRECISE FiO2 = COPD device.
- COPD SpO2 TARGET = 88–92% (NOT 94–98%). Excess oxygen suppresses hypoxic drive → CO2 retention/CO2 narcosis. Never fully withhold O2; titrate carefully and monitor ABGs.
- FEV1/FVC RATIO: <70% = OBSTRUCTIVE (asthma, COPD); ≥70% = RESTRICTIVE (pulmonary fibrosis). Asthma is reversible with bronchodilators; COPD is NOT fully reversible.
- CHEST TUBE: Tidaling is NORMAL and EXPECTED. Intermittent bubbling on expiration = normal. CONTINUOUS bubbling in water-seal = AIR LEAK (find and fix). Keep system BELOW chest level. Do NOT routinely clamp (risks tension pneumothorax).
- CHEST TUBE DISLODGED: Cover site with sterile occlusive dressing taped on 3 SIDES (flutter valve); tape all 4 sides = traps air = tension risk. Notify physician immediately.
- TUBE DISCONNECTED: Submerge tube end in sterile water/saline bottle to re-establish water seal; get new drainage system. Do NOT let air enter pleural space.
- ARTERIAL PUNCTURE: ALWAYS do Allen test BEFORE radial puncture. AFTER: hold firm pressure ≥5 minutes (longer if anticoagulated) to prevent haematoma. Use heparinized syringe, no air bubbles, seal immediately, transport on ice.
- TENSION PNEUMOTHORAX (EMERGENCY): Tracheal deviation, hypotension, distended neck veins, absent breath sounds, cyanosis. Caused by clamped chest tube with air leak. Requires immediate needle decompression (2nd ICS midclavicular) then chest tube insertion.
Last Minute Tips
- On any ABG question, START with pH (acidosis vs alkalosis), then check PaCO2 and HCO3 direction using ROME. Candidates often guess the disorder without this systematic approach—it costs 30 seconds but ensures accuracy.
- For oxygen delivery device questions, MEMORIZE FiO2 ranges by device. Nasal cannula CAN'T exceed 44% no matter what; if exam asks for 50% FiO2, the answer is NOT nasal cannula. Simple mask minimum 5 L/min or CO2 accumulates.
- Chest tube troubleshooting: 'Continuous bubbling in water-seal chamber' almost ALWAYS means AIR LEAK on exams. Know the clamping sequence: clamp near patient first; if bubbling stops, leak is patient-side; if continues, leak is system-side.
- COPD oxygen target is the SINGLE MOST MISSED point on the NLE. SpO2 88–92% is NOT a 'typo'—it's intentional because higher O2 kills the hypoxic drive. Candidates overtreat COPD and inadvertently cause CO2 narcosis.
- When reading a CXR finding, correlate with clinical signs. Pleurisy on exam (painful, pleural rub) but no effusion on CXR = early/resolving pleuritis. Effusion on CXR without signs = watch, may be heart failure. Don't diagnose from imaging alone.
Comparison Tables
Rows
Values
- Low-pitched, soft, rustling
- Inspiration > expiration
- Over most lung fields
- Normal
Property
Vesicular
Values
- Medium pitch, hollow
- Equal inspiration & expiration
- Over main bronchi, between scapulae
- Normal location; abnormal elsewhere
Property
Bronchovesicular
Values
- High-pitched, loud, hollow
- Expiration > inspiration
- Over trachea only
- Abnormal over lungs (suggests consolidation)
Property
Bronchial/tracheal
Values
- Discontinuous, fine popping
- Early inspiration (fine); late inspiration (coarse)
- Usually bibasal, lower lobes
- Fluid/atelectasis: pneumonia, pulmonary oedema, heart failure
Property
Crackles (rales)
Values
- Continuous, musical, high-pitched
- Usually expiratory; can be biphasic
- Diffuse or localized
- Airway narrowing: asthma, COPD, bronchitis
Property
Wheezes
Values
- Low-pitched, snoring, rattling
- Usually expiratory
- Large airways (central)
- Secretions in airways; may clear with cough
Property
Rhonchi
Values
- High-pitched, crowing
- Inspiratory (laryngeal); biphasic (subglottic)
- Audible without stethoscope
- Upper-airway obstruction: EMERGENCY
Property
Stridor
Values
- Grating, scratchy, creaking
- Throughout breathing cycle
- Area of pleural irritation
- Pleurisy, pulmonary infarction
Property
Pleural friction rub
Columns
- Sound Type
- Pitch & Quality
- Duration
- Location
- Clinical Significance
Table Title
Breath Sounds Comparison (Normal vs Abnormal)
Rows
Values
- <7.35 (acidosis)
- >45 (HIGH — respiratory component)
- Normal (24) or elevated (compensation)
- Hypoventilation: COPD exacerbation, respiratory depression, chest trauma
Property
Respiratory Acidosis
Values
- >7.45 (alkalosis)
- <35 (LOW — respiratory component)
- Normal (24) or low (compensation)
- Hyperventilation: anxiety, pain, early sepsis, hypoxaemia
Property
Respiratory Alkalosis
Values
- <7.35 (acidosis)
- Normal (40) or LOW (respiratory compensation)
- <22 (LOW — metabolic component)
- Acid gain or base loss: DKA, lactic acidosis, diarrhoea, renal failure
Property
Metabolic Acidosis
Values
- >7.45 (alkalosis)
- Normal (40) or HIGH (respiratory compensation)
- >26 (HIGH — metabolic component)
- Base gain or acid loss: vomiting, NG suction, antacid overdose, diuretics
Property
Metabolic Alkalosis
Columns
- Disorder
- pH
- PaCO2
- HCO3
- Cause/Example
Table Title
ABG Interpretation — Four Primary Disorders (ROME Method)
Rows
Values
- Airflow obstruction (resistance ↑)
- Lung volume/capacity ↓
Property
Pathophysiology
Values
- <70% (low)
- ≥70% (normal or high)
Property
FEV1/FVC ratio
Values
- Normal or slightly low
- Significantly LOW (reduced capacity)
Property
FVC
Values
- Normal or HIGH (air trapping)
- LOW (reduced volume)
Property
TLC (Total Lung Capacity)
Values
- HIGH (air trapping, residual volume ↑)
- Normal
Property
RV/TLC ratio
Values
- Asthma, COPD, bronchiectasis, cystic fibrosis
- Pulmonary fibrosis, sarcoidosis, chest-wall deformity, obesity, kyphoscoliosis
Property
Examples
Values
- Asthma: reversible (improves); COPD: NOT fully reversible
- No bronchodilator response
Property
Bronchodilator response
Values
- Dyspnoea on exertion, wheezing, cough, barrel chest, pursed-lip breathing
- Dyspnoea on exertion, dry cough, reduced exercise tolerance, restrictive pattern
Property
Clinical presentation
Columns
- Feature
- Obstructive
- Restrictive
Table Title
Obstructive vs Restrictive Pulmonary Disease
Rows
Values
- Low-flow
- 24–44%
- 1–6 L/min
- Flow >6 L/min does NOT ↑ FiO2; dry mucosa >4 L/min; allow eating/talking
- Mild hypoxaemia, comfort, long-term O2
Property
Nasal cannula
Values
- Low-flow
- 40–60%
- 5–10 L/min
- MINIMUM 5 L/min to flush CO2 from mask dead space; prevents rebreathing
- Moderate hypoxaemia
Property
Simple face mask
Values
- Low-flow
- 60–80%
- 6–11 L/min
- Reservoir bag attached; keep bag 1/3–1/2 full on inspiration; high concentration
- Higher FiO2 needs; moderate-to-severe hypoxaemia
Property
Partial rebreather mask
Values
- Low-flow
- 80–95% (highest low-flow)
- 10–15 L/min
- Reservoir + one-way valves; keep bag INFLATED; highest non-invasive O2
- EMERGENCY: severe hypoxaemia, acute decompensation
Property
Non-rebreather mask
Values
- High-flow (fixed)
- 24%, 28%, 31%, 35%, or 40% (PRECISE)
- Varies by setting (typically 4–8 L/min)
- Precise FiO2 REGARDLESS of breathing pattern; unaffected by tidal volume
- GOLD STANDARD in COPD; controlled, low-concentration O2
Property
Venturi mask
Columns
- Device
- System Type
- FiO2 Range
- Flow Rate
- Key Points
- Best Use
Table Title
Oxygen Delivery Systems — FiO2 & Clinical Use
Rows
Values
- Gentle rise and fall with breathing = NORMAL
- Sudden absence = lung re-expanded OR tube kinked/clogged; continuous vigorous bubbling = air leak
- Assess patient; ensure tubing patent; if concerned, check for air leak with clamping sequence
Property
Tidaling (fluctuation) in water-seal chamber
Values
- Intermittent bubbling during expiration/cough (air being evacuated) = NORMAL in pneumothorax
- CONTINUOUS bubbling = AIR LEAK; abnormal
- Systematically check connections, then clamp progressively from patient to identify leak source
Property
Bubbling in water-seal chamber
Values
- First 24 h: 100–300 mL (post-op) or less (post-trauma); decreases daily
- >100 mL/h or sudden increase; bright red/frank blood (active bleed)
- Notify physician; monitor carefully; may indicate infection, recurrent leak, or bleeding
Property
Drainage amount
Values
- Serous/serosanguinous (yellow-red); gradually clears
- Fresh bright red (active bleeding); cloudy/foul-smelling (infection)
- Frank blood: may indicate intercostal vessel injury; foul odour: assess for empyema
Property
Drainage colour
Values
- Gentle continuous bubbling (wet system) or dial set appropriately (dry system)
- Vigorous bubbling (too much suction); no bubbling (suction OFF or disconnected)
- Adjust suction level per order; ensure system connected; do not increase beyond prescribed level
Property
Suction-control chamber bubbling
Values
- Improving effort; equal bilateral breath sounds; SpO2 ≥94%; symmetrical chest rise
- Increased dyspnoea; absent breath sounds unilaterally; hypoxaemia; asymmetrical chest
- Assess tube patency; check for re-collapse or tension pneumothorax; escalate care if deteriorating
Property
Patient work of breathing / breath sounds
Columns
- Finding
- Normal/Expected
- Abnormal
- Action
Table Title
Chest Tube Water-Seal System — Normal vs Abnormal Findings
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