A collapsed lung, medically termed a pneumothorax, occurs when air leaks into the space between the lung and the chest wall, known as the pleural space. This trapped air exerts pressure on the outside of the lung, causing it to partially or fully deflate. The condition primarily alters the transmission of sound produced by normal breathing. Medical professionals focus on the absence or significant reduction of the expected sounds of air movement, rather than a distinct, unusual sound.
The Physical Cause of Altered Sounds
The lungs and the inner chest wall are normally separated by the thin, fluid-filled pleural space, which maintains a negative pressure that keeps the lung fully expanded. When a tear or hole forms in the lung or the chest wall, air escapes into this space, disrupting the delicate pressure balance. This accumulation of free air prevents the lung tissue from fully inflating with each breath.
The sound of healthy breathing is generated by air moving through the bronchial tubes and into the small air sacs, or alveoli. This sound then travels through the lung tissue and chest wall to be heard externally with a stethoscope. The presence of a layer of air in the pleural space acts as a physical barrier that dampens and blocks the transmission of sound, causing the usual sounds of breathing to be muffled or disappear entirely.
What Clinical Professionals Listen For
During a physical examination, a clinical professional uses a stethoscope to perform auscultation, which involves listening to the sounds within the body. The most telling auditory finding in a person with a pneumothorax is a significant decrease or total absence of breath sounds over the affected area of the chest. This finding is often compared to the clear, normal vesicular breath sounds heard over the healthy lung on the opposite side.
With a pneumothorax, the air pocket between the chest wall and the collapsed lung tissue prevents the sound from effectively reaching the stethoscope. The resulting “diminished” or “absent” breath sounds indicate that little to no air is moving through the lung tissue on that side. Furthermore, when the chest wall over the affected area is tapped, or percussed, the extra air in the pleural space can produce a louder, more hollow sound, known as hyperresonance.
Other Symptoms Experienced by the Patient
While the primary clinical sign is the change in breath sounds, the patient typically experiences a range of physical symptoms that accompany the air leak. The onset of a collapsed lung is often marked by a sudden, sharp chest pain on the affected side. This pain is typically described as pleuritic, meaning it worsens when the patient attempts to take a deep breath or cough.
Patients also commonly experience shortness of breath, which can range from mild to severe depending on the size of the pneumothorax. The rapid accumulation of air can lead to quick, shallow breathing as the body struggles to compensate for the reduced lung capacity. Some individuals may report a sensation of chest tightness or pressure, or a feeling of being easily fatigued. In rare cases, if air has leaked into the tissues beneath the skin, a person might feel a crackling sensation, called subcutaneous emphysema, which can sometimes be heard as a crackling noise when the area is touched.
Recognizing a Medical Emergency
A collapsed lung always requires professional evaluation, but certain symptoms signal a rapidly escalating, life-threatening emergency. A condition known as a tension pneumothorax occurs when the air leak acts like a one-way valve, allowing air in but not out, causing pressure to build relentlessly. This high pressure can push the heart and major blood vessels to the opposite side of the chest, severely compromising blood flow and heart function.
Signs that indicate this level of severity include rapidly worsening shortness of breath and severe chest pain that is not relieved by rest. Visible symptoms requiring immediate emergency care are a blue discoloration of the skin, lips, or nails, known as cyanosis, which signifies dangerously low blood oxygen levels. The combination of severe respiratory distress, a very fast heart rate, and low blood pressure suggests the need for immediate intervention to relieve the pressure and stabilize the patient.