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Elastic recoil allows the lungs to expand and contract during inhalation and exhalation. It is made possible by elastic fibrous cells in the lungs, and can be impaired in people with chronic lung disease. Patients with airway constriction may have problems with springback and may require assisted ventilation.
Elastic recoil is the tendency of the lungs to bounce back as people inhale and exhale, preventing the lungs from collapsing on exhalation and allowing them to fill up on inhalation. This feature can be seen with other air-filled objects such as balloons and bladders used by underwater organisms to control diving. In sick people, springback may be reduced, putting patients at risk for airway collapse and other breathing difficulties.
When people inhale, their lungs fill rapidly with air. Surfactant, a lubricant in the lungs, changes the surface tension in the lungs and allows the alveoli, small bubble-like structures that line the lungs, to expand. At the same time, the pressure within the pleural cavity, the space surrounding the lungs, decreases to allow the lungs to expand with inhalation. If the pressure remained constant, the lungs would be squeezed inside the chest as people inhale.
On expiration, the lungs empty of air, the surfactant allows the alveoli to shrink, and the interpleural pressure increases. The lungs go through this cycle every time people breathe. Pressure changes can make breathing difficult because people cannot fully expand their lungs. Similarly, there is also a risk of lung collapse if the relationship between interpleural pressure and surface tension within the lungs is disturbed.
Elastic recoil is made possible by highly elastic fibrous cells in the structure of the lungs. These cells can easily stretch to accommodate the lungs as they expand and compress as the lungs contract during exhalation. Other body cells are stiffer and less capable of allowing for elastic recoil. People with chronic lung disease that leads to scarring and plaque buildup in the lungs may have impaired elastic recoil as their lungs are no longer as flexible. Essentially, the lungs are like a balloon inside the chest, expanding and contracting as air moves in and out.
Patients with airway constriction who can only take small breaths may have problems with springback, as the lungs may not expand enough during inhalation and a collapsed lung may develop. When patients undergo assisted ventilation because they cannot breathe on their own, the ventilation device is carefully adjusted to allow the patient’s lungs to expand fully, without causing lung damage by forcing too much air into the lungs or by delivering air with too much pressure and stopping the balance of tension and pressure within the chest.
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