Etiology and mechanisms of development
The entry of air into the pleural cavity occurs when the integrity of the pleural layers is compromised. There are two main pathways for the formation of this syndrome:
- Rupture of the visceral pleura. It originates from the lung tissue. The main pathologies leading to such a rupture include bullous emphysema of the lungs, a ruptured lung abscess emptying into the pleura, and a tuberculous cavity.
- Injury to the chest wall. A traumatic wound that compromises the integrity of the parietal pleura, allowing air to enter the cavity from the outside environment.
Inspection and palpation of the chest
During the physical examination of a patient with air accumulation in the pleural cavity, a number of specific signs related to changes in volume and pressure within the hemithorax are revealed.
First, visual inspection reveals pronounced chest asymmetry. On the affected side, smoothing of the intercostal spaces is observed. Second, the dynamics of respiratory movements are evaluated: the affected half of the chest noticeably lags behind the healthy side during breathing.
On palpation, air accumulation manifests as a weakening of vocal fremitus (fremitus vocalis). The air cushion in the pleural cavity acts as an insulator that impedes the normal conduction of sound vibrations from the vocal cords to the surface of the chest wall.
Percussion findings
Topographic and comparative percussion play a key role in the differential diagnosis of pneumothorax. The main percussive sign of gas accumulation is a tympanic (or hyperresonant) sound over the affected area. It is important to distinguish it from the dull percussion sound that occurs in hydrothorax (fluid accumulation).
With a significant volume of air in the pleural cavity, the lower boundary of the tympanic sound shifts downward. This occurs due to the unfolding and expansion of the costodiaphragmatic recesses.
Combination of gas and fluid A specific pattern is observed if gas and fluid accumulate simultaneously in the pleural cavity (this condition is classified as hydropneumothorax, pyopneumothorax, or hemopneumothorax). In this case, percussion reveals a distinct horizontal fluid level:
- In the lower zone, a dull sound is determined, caused by the presence of liquid contents.
- In the upper zone, a tympanic sound is preserved, corresponding to free gas.
Auscultation and tension pneumothorax
The auscultatory pattern of pneumothorax in typical cases is characterized by a sharp weakening or complete absence of vesicular breath sounds on the affected side. This is due to the fact that the expanded lung is compressed, and the layer of air shields the breath sounds.
Internal tension (valvular) pneumothorax This is a specific and extremely dangerous variant of the syndrome. Its mechanism is that the resulting communication between the bronchus and the pleura acts as a one-way valve. During inspiration, air enters the pleural cavity freely, but upon expiration, the opening closes, preventing air from escaping. Thus, with each respiratory cycle, pressure inside the pleural cavity builds up.
The auscultatory phenomenon in this pathology is unique: bronchial breathing is auscultated. A distinguishing feature is that, unlike the lung tissue consolidation (infiltrate) syndrome, in tension pneumothorax, bronchial breathing is heard only during inspiration — precisely at the moment when the next portion of air under pressure enters the pleural cavity through the formed valve.
Briefly: answers to topical questions
What radiological signs confirm the presence of pneumothorax?
Radiological signs of true pneumothorax include the presence of a thin visceral pleural line whose orientation matches the contour of the collapsed lung, and the absence of blood vessels beyond it. In the supine position, atypical signs are revealed:
- Deep sulcus sign (deep sulcus sign) — a deep, finger-like lateral costodiaphragmatic recess.
- «Double diaphragm» sign (double diaphragm sign) — a visible anterior recess in the form of an oblique line mimicking the adjacent diaphragm.
- Increased lucency — ipsilateral generalized hyperlucency or a band parallel to the diaphragm and mediastinum.
What effect does a tension (valvular) pneumothorax have on the mediastinal organs?
Tension pneumothorax causes progressive compression of the lung and displacement of the mediastinal organs toward the healthy side.
Mechanism: air is sucked into the pleural cavity during inspiration but cannot escape during expiration due to the soft-tissue valve.
Clinically, this is accompanied by:
- hemodynamic disturbances: drop in blood pressure (collapse), rapid weak pulse;
- respiratory disturbances: marked dyspnea, acrocyanosis.
In hydropneumothorax, percussion reveals a clear division: "tympanic on top, dull on the bottom" (in the upper zone, a tympanic sound over gas; in the lower zone, a dull sound over fluid, separated by a strict horizontal level).
Class and exam questions
How to distinguish pneumothorax from hydrothorax on percussion?
In pneumothorax (air accumulation), a tympanic or hyperresonant sound is determined. In hydrothorax (fluid accumulation), the percussion sound will be dull.
What happens to vocal fremitus in pneumothorax?
Vocal fremitus (fremitus vocalis) on the affected side is sharply weakened, as the accumulated air poorly conducts sound vibrations from the bronchi to the chest wall.
During which phase of respiration is bronchial breathing heard in tension pneumothorax?
In internal tension pneumothorax, bronchial breathing is auscultated exclusively during inspiration — at the moment when a portion of air passes through the valve from the bronchus into the pleural cavity.
What else to study on this topic
- Bullous emphysema of the lungs as a cause of spontaneous pneumothorax
- Drained lung abscess and tuberculous cavity in the etiology of visceral pleural rupture
- Differential diagnosis of types of hydropneumothorax: hydro-, pyo-, and hemopneumothorax
- Pathogenesis and mechanics of internal tension (valvular) pneumothorax
- Differences between the auscultatory pattern of tension pneumothorax and lung tissue infiltrative consolidation syndrome
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