Which of the following is a potential effect of immobility that can lead to reduced lung expansion?

A. Muscle atrophy is the wasting away of muscle tissue due to lack of physical activity, which primarily affects skeletal muscles like the quadriceps. While severe atrophy of the intercostal muscles can eventually weaken respiratory effort, it is not the immediate clinical effect that causes reduced lung expansion. This condition is a long-term musculoskeletal consequence of prolonged bed rest and deconditioning. B. Impaired perfusion refers to the inadequate flow of blood through the pulmonary or systemic capillaries, affecting gas exchange at the alveolar level. While immobility can contribute to perfusion issues like pulmonary emboli, it does not directly restrict the mechanical expansion of the lung tissue. Perfusion is a circulatory process, whereas lung expansion is a mechanical, ventilatory process of the respiratory system. C. Atelectasis is the collapse of alveoli that occurs when patients remain immobile and engage in shallow, restricted breathing patterns. The lack of deep inspiration and surfactant distribution causes the air sacs to deflate, significantly reducing the surface area available for gas exchange. This mechanical collapse is a direct result of reduced lung expansion and can lead to secondary hypoxemia and pneumonia. D. Venous stasis is the slow or stagnant flow of blood in the veins, typically in the lower extremities, increasing the risk of thrombus formation. Although this is a major complication of immobility, it pertains to the vascular system rather than the respiratory mechanics of the lungs. Venous stasis does not have a direct anatomical effect on the ability of the lungs to expand.