The human body relies on two lungs to perform gas exchange, which involves drawing oxygen into the bloodstream and expelling carbon dioxide as a waste product. While two lungs provide maximum respiratory capacity, the body possesses a remarkable ability to adapt to significant loss of organ function. It is possible to survive and live a relatively complete life even if one lung is entirely absent. The remaining lung, provided it is healthy, can take over the necessary function to sustain the body’s oxygen requirements during rest and light activity.
Why Someone Might Have Only One Lung
The most common reason for a person to have only one lung is a surgical procedure known as a pneumonectomy, which involves the complete removal of one of the two organs. This major operation is typically reserved for severe medical conditions where the entire lung is compromised beyond repair. The primary indication for a pneumonectomy is often extensive lung cancer, particularly when the tumor is centrally located or has spread widely throughout the organ.
The procedure may also be performed to address severe, localized infections that have caused irreversible damage to the lung tissue. Examples include aggressive cases of tuberculosis or fungal infections that destroy the lung’s structure. Additionally, a pneumonectomy can become necessary following extensive chest trauma, such as a severe accident or penetrating injury, if the damage to the vessels and airways is irreparable.
A secondary, far rarer cause is a congenital condition known as pulmonary agenesis, where one lung fails to develop completely during embryonic life. Patients with unilateral agenesis who survive infancy often present with a functional single lung, as their bodies have adapted to the condition from birth.
Physiological Adjustments for Single Lung Survival
The body’s mechanical and physiological compensations utilize the remaining space and maximize gas exchange. The most noticeable mechanical change is the compensatory hyperinflation of the remaining lung, causing it to expand and occupy a portion of the empty chest cavity. This expansion is accompanied by a shift of the mediastinum, the central compartment containing the heart and major blood vessels, toward the empty side.
This mediastinal shift and the elevation of the diaphragm on the side of the removal help to reduce the size of the void left by the missing organ. The space itself, initially filled with air following surgery, gradually fills with fluid over weeks and months, further stabilizing the internal structures. Crucially, the entire pulmonary blood flow, which previously split between two lungs, is rerouted to the single remaining lung, effectively doubling the flow through its vascular network.
The remaining lung tissue becomes significantly more efficient at oxygen extraction and carbon dioxide removal. This efficiency is achieved through an increase in the respiratory rate and depth of breathing, which ensures sufficient oxygenation even with a reduced alveolar surface area. While the total lung capacity is reduced, this combination of mechanical expansion and functional optimization allows for the maintenance of normal blood oxygen levels during periods of rest.
Daily Life and LongTerm Outlook
Living with a single lung requires certain adjustments. Individuals with one lung commonly experience a reduced tolerance for strenuous aerobic exercise, often feeling short of breath during heavy exertion like running or rapidly climbing stairs. However, many people can still perform daily tasks and participate in light to moderate exercise without difficulty.
The long-term outlook largely depends on the reason for the removal and the overall health of the remaining lung. If the pneumonectomy was performed due to trauma and the remaining lung is healthy, the prognosis for a long, productive life is generally favorable. For those whose surgery was necessitated by cancer, the long-term survival is determined by the prognosis of the underlying disease.
Protecting the remaining lung becomes the primary focus of long-term care. Avoiding smoking and exposure to toxic fumes is necessary to preserve the delicate lung tissue. Individuals must also be diligent in managing respiratory illnesses, such as the flu or common cold, as any infection that compromises the single lung poses a greater health risk.