Grades of Finger Clubbing

4-Grade System (most widely used)

5-Grade System (alternative)

Key Clinical Signs & Tests

Lovibond's Sign (Profile Sign)

Schamroth's Window Test

• Place the dorsal surfaces of the terminal phalanges of corresponding fingers (especially ring fingers) back-to-back.
• Normal: A small diamond-shaped window is visible at the bases of the nail beds.
• Positive (clubbing): The window is obliterated — the earliest detectable sign of clubbing.
• Sensitivity 77–87%, specificity 90%, positive LR ~8.

Fluctuation Test

Phalangeal Depth Ratio (PDR)

Pathophysiology (brief)

1. Increased soft tissue in the distal phalanx — driven by hypoxia-induced upregulation of VEGF, PDGF, HIF-1α, HIF-2α, and increased microvessel density.
2. Peripheral arteriovenous shunting — megakaryocytes and platelets bypass pulmonary/hepatic filtration and release growth factors directly in digital capillaries.

Causes (by grade severity)

Dyspnea Grading Scales

1. Modified Medical Research Council (mMRC) Dyspnea Scale

Clinical use: mMRC ≥2 indicates significant symptom burden in COPD (GOLD criteria). It is also a component of the BODE index (mMRC 0–1 = 0 points; 2 = 1 point; 3 = 2 points; 4 = 3 points). — Fishman's Pulmonary Diseases and Disorders; Harrison's 22E

2. New York Heart Association (NYHA) Functional Classification

Note: NYHA class does not correlate well with objective measures such as LV ejection fraction or peak VO₂ consumption. — Harrison's Principles of Internal Medicine 22E

3. Modified Borg Scale

Numerical rating scales (0–10) and visual analog scales (10 cm line) are equivalent in reliability. The Borg scale is a variant with verbal anchors at key points. All have been validated against each other. — Murray & Nadel's Textbook of Respiratory Medicine

4. American Thoracic Society (ATS) 5-Point Dyspnea Scale

5. Baseline Dyspnea Index (BDI) / Transition Dyspnea Index (TDI)

• Magnitude of task that elicits dyspnea (e.g., hills vs. level ground)
• Impact on activities of daily living
• Effort required to produce dyspnea

Summary Comparison

6-Minute Walk Test (6MWT)

Definition

Protocol (ATS Guidelines)

Contraindications

Normal Values

• Men: 6MWD = (7.57 × height cm) − (5.02 × age) − (1.76 × weight kg) − 309
• Women: 6MWD = (2.11 × height cm) − (2.29 × weight kg) − (5.78 × age) + 667

Minimal Clinically Important Difference (MCID)

Clinical Indications

1. Measuring response to interventions — pulmonary rehabilitation, pharmacotherapy (PAH, heart failure), lung transplant, LVRS
2. Functional status assessment — COPD, cystic fibrosis, heart failure, IPF, peripheral vascular disease
3. Pre-transplant evaluation — eligibility and timing for lung transplantation
4. Prognosis prediction — component of the BODE index in COPD; correlates with mortality in COPD, IPF, PAH, heart failure
5. Titrating supplemental oxygen — assess exertional hypoxemia and oxygen flow requirements
6. Preoperative risk assessment — predictor of postoperative outcomes

BODE Index (uses 6MWD)

A BODE score >7 → ~30% 2-year mortality; score 5–6 → ~15%; score <5 → <10%. — Fishman's Pulmonary Diseases and Disorders

Comparison with Other Exercise Tests

Key Advantages & Limitations

• Simple, cheap, no specialised equipment
• Reflects daily activity functional capacity better than maximal tests
• Well validated; widely used in RCTs
• Correlates with QoL measures; changes in 6MWD correlate with improvements in dyspnea

• Submaximal — most patients do not reach maximal exercise capacity
• Cannot identify the specific physiologic cause of exercise limitation (unlike CPET)
• Practice/learning effect — 2nd test is typically ~25 m longer than 1st
• Results sensitive to corridor length, encouragement style, and patient motivation
• No universally accepted reference standards across all age groups

Pneumothorax

Classification

1. Spontaneous Pneumothorax

Primary Spontaneous Pneumothorax (PSP)

• Occurs without underlying lung disease
• Caused by rupture of apical pleural blebs (small cystic spaces within or immediately under the visceral pleura)
• Typical patient: tall, thin, young males (15–35 yrs); smokers
• ~50% recurrence after first episode
• CT findings of multiple blebs/bullae → higher recurrence risk

Secondary Spontaneous Pneumothorax (SSP)

• Occurs in the presence of underlying lung disease
• More life-threatening due to reduced pulmonary reserve
• Causes:
  • COPD (most common — bleb/bulla rupture)
  • Cystic fibrosis
  • Asthma
  • AIDS/Pneumocystis jirovecii pneumonia
  • Metastatic cancer (especially sarcoma)
  • TB, lung abscess
  • Catamenial pneumothorax — in women, within 72 hours of menses onset (related to endometriosis)

2. Traumatic Pneumothorax

• From penetrating (stab, gunshot) or blunt chest trauma
• Present in 40% of blunt thoracic trauma and 20% of penetrating injuries
• Includes iatrogenic causes:
  • Transthoracic needle aspiration
  • Thoracentesis
  • Central venous catheter insertion (subclavian/internal jugular)
  • Mechanical ventilation (barotrauma/volutrauma)
  • Positive pressure ventilation (alveolar overdistention → rupture)

3. Tension Pneumothorax

• Air enters the pleural space via a one-way valve mechanism — cannot escape
• Progressive air trapping → rising intrapleural pressure
• Causes:
  • Contralateral mediastinal shift
  • Compression/kinking of SVC and IVC → ↓ venous return → ↓ cardiac output
  • Obstructive shock
• Most common in: mechanically ventilated patients; also traumatic and resuscitation settings

Clinical Features of Tension Pneumothorax

4. Open Pneumothorax (Sucking Chest Wound)

• Chest wall defect allows air entry through the wound with breathing
• If wound size ≈ trachea size → air preferentially enters wound rather than airway → impairs ventilation
• Management: 3-sided occlusive dressing (Heimlich flutter valve) → allows air egress but not entry → followed by operative repair

Diagnosis

Chest X-Ray

• Hyperlucent area with absent bronchovascular markings peripheral to a visible visceral pleural line
• Lung collapse toward hilum
• Tension: mediastinal shift to contralateral side + hemidiaphragm depression

CT Chest

• Most sensitive; detects occult pneumothoraces
• Quantifies size; identifies blebs/bullae; guides management decisions

Ultrasound (POCUS)

"A lung point represents the edge of the pneumothorax where the lung has fallen away from the parietal pleura" — Murray & Nadel's

Size Assessment

Management

Tension Pneumothorax — Medical Emergency

Treat clinically before imaging

1. Immediate needle decompression (temporising):
   • 14–16G cannula (adults), 18G (children); ≥3–5 cm length
   • 2nd intercostal space, midclavicular line (traditional)
   • OR 4th/5th ICS, midaxillary line (preferred by ATLS — less chest wall thickness, avoids internal mammary vessels)
   • Confirmed by air escaping under pressure or rapid haemodynamic improvement
2. Definitive: Tube thoracostomy (chest drain)

Primary Spontaneous Pneumothorax

Secondary Spontaneous Pneumothorax

Traumatic Pneumothorax

• Most treated with tube drainage unless very small
• Hemopneumothorax: two chest tubes — one superior (air), one inferior (blood)
• Iatrogenic: supplemental O₂ or aspiration first; tube if fails

Chest Tube Management

• Attached to water seal device
• Routine suction not recommended (does not improve outcomes)
• Suction (−20 cm H₂O) reserved for lung failure to re-expand after 24–48h
• Remove when lung fully re-expanded and air leak ceased
• Clamp test ×4 hours before removal

Recurrence Prevention

• VATS with bleb resection + mechanical/talc pleurodesis: nearly 100% effective
• Chemical pleurodesis alone: if not surgical candidate
• Indications for surgery (first episode PSP): occupational hazard (pilots, divers), remote travel, CT showing multiple blebs

Complications

• Tension pneumothorax → obstructive shock → death if untreated
• Re-expansion pulmonary oedema (rare — after large pneumothorax evacuation)
• Re-expansion hypotension (rare)
• Chest tube complications: malposition, pleural infection, pain

Metabolic Equivalent of Task (MET)

Definition

MET Scale: Activities by Level

Clinical Classification of Functional Capacity

The critical clinical threshold is 4 METs. — ACC/AHA 2014 Guidelines

Clinical Significance — Perioperative Risk Assessment

ACC/AHA Guideline Recommendation

• ≥4 METs functional capacity → patient may proceed directly to surgery (low perioperative cardiac risk)
• <4 METs OR uncertain functional capacity → consider exercise/pharmacologic cardiac stress testing if results would alter management

Why 4 METs?

• Based on exercise testing studies linking poor functional capacity with elevated major adverse cardiac events (MACE) perioperatively
• ≥4 METs ≈ ability to climb 1 flight of stairs or do light gardening — activities of moderate exertion

Practical Bedside Markers for ≥4 METs

Assessment Tools

1. Duke Activity Status Index (DASI)

• Take care of yourself (eating, dressing, bathing) — 2.75 pts
• Walk 200 yards on level ground — 2.75 pts
• Climb a flight of stairs or walk up a hill — 5.50 pts
• Run a short distance — 8.00 pts
• Do heavy housework (moving furniture) — 8.00 pts
• Play golf / doubles tennis / dance — 6.00 pts
• Strenuous sports (singles tennis, basketball, skiing) — 7.50 pts

2. MET-REPAIR Questionnaire

3. Objective Testing

• 6-Minute Walk Test — poor performance → increased major postoperative complications
• Incremental Shuttle Walk Test
• CPET (gold standard) — directly measures VO₂ max, anaerobic threshold

Important: Resting LVEF is NOT a proxy for functional capacity — exercise capacity can vary considerably among patients with similar resting EF. — Miller's Anesthesia 10e

MET in Other Contexts

Key Formula

1 MET = 3.5 mL O₂/kg/min ≈ 1 kcal/kg/hour