Pneumothorax & Chest Trauma

Normal pleural pressure is negative, and that gradient is the only thing holding the elastic lung out against the chest wall. When the visceral pleura ruptures, air enters the pleural space, the gradient collapses, and the lung recoils inward until pressures equalize or the rupture seals. In a spontaneous pneumothorax the barrier fails when an acute rise in transpulmonary pressure — a cough, a strain, a Valsalva — exceeds the tensile strength of the alveolar wall. The usual weak point in an otherwise healthy young lung is an apical subpleural bleb or bulla, found in up to 77% of primary spontaneous cases; smoking loads the small airways with inflammatory cells and multiplies the risk.

Two classifications run in parallel. By cause: primary spontaneous (PSP) — no underlying lung disease, typically a tall, thin young smoker; secondary spontaneous (SSP) — a diseased lung, most often COPD with rupturing bullae; and traumatic — blunt or penetrating injury, including the iatrogenic pneumothorax that follows a needle biopsy, a central venous line, or positive-pressure ventilation. By physiology: simple (no communication with the atmosphere, no mediastinal shift), open (a chest-wall defect connects the pleural space to the outside — the "sucking" chest wound), and tension (progressive air accumulation under pressure that shifts the mediastinum and collapses the circulation). Size is read as the rim between lung edge and chest wall: < 2 cm = small, > 2 cm = large (StatPearls), and a 2.5 cm air space equals roughly a 30% pneumothorax.

Two management ideas fall straight out of the physics. Oxygen shrinks a pneumothorax: 100% supplemental oxygen lowers the alveolar nitrogen partial pressure, and the nitrogen-rich pleural air is absorbed up to four times faster than the untreated 1–2% of volume per day. And a chest tube works by removing air, blood, or fluid so that the negative intrathoracic pressure is restored and the lung can re-expand — every rule about that tube exists to protect that negative pressure.

Tension pneumothorax is a one-way valve at the pleural breach: tissue lets air in during inspiration and blocks its exit during expiration, so intrapleural pressure climbs with every breath. The lung on that side collapses completely; then the whole mediastinum shifts toward the opposite side. The shift kinks and compresses the superior vena cava, venous return falls, and cardiac output drops — obstructive shock. Falling output raises pulmonary vascular resistance and deepens the hypoxemia, and the spiral ends in cardiac arrest. The early picture is severe respiratory distress, tachypnea, tachycardia, chest retractions, and cyanosis; the late picture adds hypotension, jugular venous distension, unilateral absent breath sounds with hyperresonance, altered mental status, and tracheal deviation away from the affected side. Tracheal deviation is the sign every student memorizes and the one to trust least: it is explicitly a late and unreliable finding, and waiting for it is waiting for the arrest.

That is why tension pneumothorax is a clinical diagnosis. Do not let a chest radiograph or CT delay decompression in an unstable patient — reliance on any single finding delays life-saving intervention. In a ventilated patient the cue set changes: rising peak and plateau pressures, high-pressure alarms, desaturation, and hypotension announce the tension before any exam finding does, and barotrauma from positive-pressure ventilation is the leading iatrogenic cause of tension (about 70% of cases), with central venous catheterization next. Positive-pressure devices of any kind — the ventilator, noninvasive ventilation, high-flow nasal cannula — applied to an undrained pneumothorax push air through the leak and manufacture the tension you are trying to avoid.

The fix is mechanical: decompress immediately — one needle attempt, then a chest tube. The site has moved. Current recommendations favor a lateral approach at the 4th or 5th intercostal space, between the anterior and mid-axillary lines, because the traditional 2nd intercostal space, midclavicular line, has high failure rates from chest-wall thickness and too-short needles; the 2nd ICS midclavicular site remains the alternative. Use a long (≥ 8 cm) large-bore catheter and enter just above the rib to spare the neurovascular bundle that runs under the rib below. Tube thoracostomy then resolves about 90% of pneumothoraces; the tube goes in at the triangle of safety — 5th intercostal space, anterior-to-mid-axillary line, along the upper rib border. Give 100% oxygen, and avoid positive-pressure ventilation until the chest is drained. Hold one differential in mind: cardiac tamponade sits on the same ATLS primary-survey list of immediate life threats (airway injury, tension pneumothorax, cardiac tamponade, massive hemothorax, flail chest, open pneumothorax) and shares the JVD and hypotension — but tamponade has muffled heart sounds with clear, equal breath sounds, while tension has absent breath sounds, hyperresonance, and tracheal shift.

An open pneumothorax appears when chest trauma creates a communication between the pleural cavity and the outside world: with every inspiratory effort air is drawn through the wall defect instead of down the trachea — the "sucking" chest wound. The first-aid physics is a three-sided occlusive dressing: taped on three sides, it lifts on expiration to let air escape and seals on inspiration to stop air entering, and it is followed by a chest tube. A commercial vented chest seal applies the same principle (air out, not in) and is now preferred prehospital. What you never do is seal the wound on all four sides without a chest tube — an improperly sealed occlusive dressing over an ongoing leak converts an open pneumothorax into a tension pneumothorax.

Hemothorax is blood in the pleural space. The bleeding comes from intercostal or internal mammary arteries, the great vessels, mediastinum, myocardium, lung parenchyma, diaphragm, or abdomen — in blunt trauma, most often intercostal vessels torn by rib fractures and bleeding lung tissue. Each hemithorax can hold about 40% of a patient’s circulating blood volume, so a massive bleed does two things at once: it drains the circulation into the chest (hypovolemic shock from lost preload) and it compresses the lung with the mass of blood (tension physiology). The exam pattern is the mirror image of pneumothorax: respiratory distress and decreased breath sounds, but dullness to percussion rather than hyperresonance, and in shock flat neck veins rather than the distended veins of tension. Chest trauma is the most frequent cause, and motor-vehicle collisions account for 70–80% of blunt chest trauma; thoracic injuries occur in about 60% of multi-trauma cases and cause 20–25% of trauma deaths — and they rarely occur alone, so the rest of the body is searched for associated injuries.

Management scales with volume. A minimal hemothorax (< 300 mL) is observed; a moderate or large one gets a 28–32 F chest tube placed posteriorly at the 4th–5th intercostal space while a hemostatic resuscitation runs alongside — and most patients are managed with the drain alone. The numbers that send a patient to thoracotomy are the ones the nurse watching the collection chamber must know: ≥ 1,500 mL on initial drainage, or ongoing bleeding of ≥ 200 mL/h for 2–4 hours. Blood left behind is not benign: a retained hemothorax carries a 26.8% empyema incidence and can organize into fibrothorax with lung entrapment, which is why it is cleared by VATS or intrapleural thrombolysis.

Ribs 4–10 are the ones that break; ribs 1–3 are so protected that a fracture there signals severe trauma. Older adults break ribs in falls on osteoporotic bone and die of it more often; a child’s elastic ribs rarely fracture at all, so a rib fracture in a child warrants investigation for child abuse. The physiology that kills is not the bone but the pain cascade: chest-wall pain → splinting (reduced chest-wall movement and cough) → hypoventilation and failed secretion clearance → atelectasis → pneumonia, and from there ARDS and pulmonary embolism. Older adults with rib fractures carry higher mortality — a single fracture doubles the risk compared with a younger patient — and each additional broken rib raises mortality by about 19% and pneumonia risk by about 27%. Lower rib fractures also prompt a screen for liver and spleen injury.

Flail chest is fractures of 3 or more consecutive ribs in at least 2 places, which frees a segment of chest wall to move on its own. It deteriorates by three mechanisms. First, paradoxical motion: the free segment collapses inward during inspiration as the intact chest wall expands outward, so ventilation is ineffective and dead space rises. Second, the pulmonary contusion beneath it is nearly universal and is the major cause of the hypoxemia. Third, the pain-induced splinting cascade above. Paradoxical motion is the sign the exam wants, but a splinting patient can hide it — it may become visible only after extubation or once the intercostal muscles fatigue — so the diagnosis is primarily clinical. Mortality runs 10–20%, typically from associated injuries, and recovery takes 6–12 months, some of it with chronic pain and deformity. Motor-vehicle collisions cause about 75% of flail chests and falls in the elderly 15%.

Pulmonary contusion is a lung parenchymal injury without a laceration of lung or vessel. Blunt force disrupts the blood–air barrier, blood and fluid leak into the alveoli, surfactant falls, alveoli collapse, and the result is V/Q mismatch and intrapulmonary shunt → hypoxemia in proportion to the contusion’s size. The trap is timing: a mild injury can be asymptomatic on arrival and emerge or worsen over 24–48 hours, and the chest X-ray can lag the injury by 6–48 hours. It is the most common lung injury in blunt chest trauma (30–75% of cases) with a mortality of 10–25%, and it heals in 5–7 days with supportive care — oxygen, pain control, pulmonary hygiene, careful fluid management (over-resuscitation floods the injured alveoli), and low-tidal-volume ventilation if intubated. Prophylactic corticosteroids and antibiotics are not recommended.