Chest Wall Injuries
Fractured Ribs & Flail Chest
Pathophysiology: Simple rib fractures compromise ventilation primarily through pain. Pain limits chest excursion, reducing tidal volume and preventing coughing, which leads to atelectasis (alveolar collapse) and subsequent pneumonia.
Flail Chest: Occurs when $\ge$3 adjacent ribs are fractured in $\ge$2 places, creating a floating segment.
Mechanism: The segment moves paradoxically (in during inspiration, out during expiration).
Clinical Reality: The paradoxical movement itself is rarely the cause of hypoxia. The underlying Pulmonary Contusion (bruising of the lung parenchyma) causes alveolar haemorrhage and oedema, creating a severe Ventilation/Perfusion (V/Q) mismatch and hypoxia.
Cognitive Bias in Minor Injuries
Scenario: A stoic patient with "minor" chest injuries underplays their symptoms.
Risk: Anchoring Bias (locking onto the patient's self-assessment) or Affective Bias (respecting their stoicism) may lead to undertriage.
Strategy: Rely on objective physiological markers. Even if the patient smiles, a Respiratory Rate >24, SpO2 <94%, or inability to cough effectively are "hard signs" of respiratory compromise. Palpate the chest wall for crepitus regardless of patient complaints.
Management Priorities
- Analgesia: This is a resuscitation intervention. Without pain relief, the patient cannot ventilate. Use multimodal analgesia (Paracetamol + Opioids +/- Ketamine).
- Respiratory Support: Titrate Oxygen to SpO2 94-98%. If flail segment/contusion is causing failure, consider CPAP (cautiously, watching for pneumothorax) or positive pressure ventilation (BVM).
- Splinting: Do not tape/sandbag flail segments (restricts expansion). Use a bulky dressing or patient's arm for comfort only.
Mass Casualty Consideration
Scenario: MCI, patient with flail chest, SpO2 92%, RR 32. Limited resources.
Adaptation:
1. Positioning: Sit upright (maximises FRC).
2. Analgesia Conservation: Prioritise IV/IM opiates for this patient to reduce work of breathing (WOB).
3. Oxygen: If limited, target SpO2 >90%.
4. Triage: This is a "Red/Immediate" patient due to RR >30 and potential for rapid decompensation (tension/contusion).
Pleural Space Pathology
The Vacuum Seal
The parietal and visceral pleura are held together by negative intrapleural pressure. Breaching this seal allows air or blood to enter, collapsing the lung.
| Condition | Pathophysiology | Clinical Signs |
|---|---|---|
| Simple Pneumothorax | Air enters pleural space. Lung collapses. Ventilation reduced but haemodynamics stable. | Reduced breath sounds (unilateral), Hyper-resonant percussion. |
| Haemothorax | Blood enters pleural space (intercostal vessels/lung parenchyma). Causes Hypovolemia (blood loss) + Hypoxia (lung compression). | Reduced breath sounds, Dullness to percussion, Signs of Shock (Pale, Tachycardic). |
| Open Pneumothorax | "Sucking Chest Wound". Chest wall defect >2/3 diameter of trachea allows air to preferentially enter wound vs trachea. | Visible bubbling wound, severe distress. |
Differentiation: Haemothorax vs. Pneumothorax
Scenario: High-speed collision, hypotensive, reduced sounds right side.
Differentiation:
1. Percussion: Pneumothorax is Hyper-resonant (hollow drum). Haemothorax is Dull (thud).
2. History: Deceleration trauma often tears vessels (Haemothorax).
3. Neck Veins: Flat in Haemothorax (hypovolemia). Distended in Tension Pneumothorax (obstructive).
Treatment Impact:
Haemothorax: Needs volume replacement (Blood > Fluids) and rapid transport for tube thoracostomy/surgery. Needle decompression is useless (needles can't drain thick blood).
Pneumothorax: Observe. If hypotensive, treat as Tension (see below).
Tension Pneumothorax (Obstructive Shock)
Pathophysiology
A "one-way valve" defect allows air into the pleural space during inspiration but prevents escape during expiration.
Sequence of Death:
1. Intrapleural pressure rises > atmospheric pressure.
2. Ipsilateral lung collapses completely.
3. Mediastinum shifts to the opposite side.
4. Superior and Inferior Vena Cava are kinked/compressed.
5. Preload drops to zero -> Cardiac Output fails -> Obstructive Shock -> PEA Arrest.
Sentinel Signs (Indications for Decompression)
Tension pneumothorax is a Clinical Diagnosis. Do not wait for X-rays. You need:
- Progressive Respiratory Distress (Air Hunger).
- Unilateral decreased/absent breath sounds.
- Signs of Haemodynamic Compromise (Hypotension, SBP <90mmHg, losing radial pulse).
Note: Tracheal deviation is a very late sign (often post-mortem). JVD may be absent if the patient is hypovolemic (concomitant bleeding).
Assessment in Difficult Environments
Scenario: Noisy scene (helicopter/traffic), patient won't lie flat. Auscultation impossible.
Decision Tools:
1. Look: Asymmetrical chest rise? Surgical emphysema (swelling neck/chest)?
2. Monitor: Improving SpO2? Rising EtCO2 (good) or falling EtCO2 (poor perfusion)?
3. Palpate: Tracheal position (suprasternal notch).
4. Decision: If SBP is crashing and mechanism fits, decompress. "Life over Limb".
Needle Thoracocentesis (Decompression)
The Procedure & The Evidence
Goal: Convert a Tension Pneumothorax into a Simple/Open Pneumothorax to restore venous return.
Device Selection (Pros/Cons):
1. Standard 14G IV Cannula (4.5-5cm): Pros: Ubiquitous, cheap. Cons: High Failure Rate (42-50%) at 2nd ICS MCL due to chest wall thickness (Lesperance et al., 2018). Kinks easily.
2. Long Catheters (8cm+): Pros: Reaches pleural space in >90% of patients. Cons: Risk of deep injury (lung/heart) if placed incorrectly.
3. Commercial Devices (e.g., ARS, Spear): Pros: Reinforced (won't kink), open tip. Cons: Cost.
Site Selection Debate (Inaba et al., 2012):
2nd ICS Mid-Clavicular Line (MCL): Traditional. Risk: Often too thick (pectoralis muscle). High failure rate.
5th ICS Anterior Axillary Line (AAL): Modern Alternative. Benefit: Thinner chest wall. Risk: Closer to heart (left side) and liver/spleen if landmarks missed.
Risk vs. Benefit Analysis
Complications: Iatrogenic pneumothorax (creating one where none existed), vascular injury (intercostal artery), cardiac tamponade (if too medial), infection.
Weighing the Risk: Untreated tension pneumothorax is fatal. If the patient is hypotensive and hypoxic due to chest trauma, the risk of a needle is acceptable compared to the certainty of cardiac arrest. If the patient is normotensive, WAIT and monitor.
Communicating the Intervention
Closed Loop Communication:
"I suspect Tension Pneumothorax on the LEFT. Signs are absent air entry and SBP 80."
"I am preparing to decompress the LEFT chest."
"Decompression complete. Rush of air heard. Reassessing vitals now."
Cardiac & Great Vessel Trauma
Pericardial Tamponade
Pathophysiology: Blood fills the pericardial sac (tough, fibrous, non-stretchy). As little as 100-200mL acutely can compress the ventricles.
Result: Ventricles cannot fill (diastolic failure) -> Cardiac Output drops -> Obstructive Shock.
Beck's Triad (Classic but Rare):
1. Hypotension (Narrow pulse pressure).
2. Distended Neck Veins (JVD).
3. Muffled Heart Sounds.
Management: "Fill the Tank"
If pericardiocentesis (needle drainage) is outside scope:
- Fluid Bolus: Administer fluids to increase venous pressure (Preload). You are trying to use hydrostatic pressure to force blood into the compressed heart.
- Rapid Transport: This is a surgical emergency (Thoracotomy). Scoop and Run.
- Advocacy: Pre-alert the hospital specifically: "Suspected Tamponade. Penetrating chest trauma. Hypotensive and Tachycardic. Requires immediate surgical review."
Sternal Fracture & Cardiac Contusion
Mechanism: Blunt force (steering wheel/seatbelt).
Risk: Myocardial Contusion (bruising of heart muscle). Can lead to arrhythmias (PVCs, VT, VF) or pump failure (cardiogenic shock).
Management: 12-Lead ECG monitoring is mandatory for all sternal fractures.
Penetrating Trauma
Impaled Objects
Rule: Do NOT remove unless it obstructs CPR or the airway.
Action: Stabilise with bulky dressings (donut ring). Vibration/movement of the object can lacerate the aorta or lung.
Open Pneumothorax
Action: Apply an occlusive dressing (Chest Seal). Prefer vented seals (allows air out, not in). If using 3-sided dressing, monitor closely for development of Tension Pneumothorax (if the valve clogs).