Final answer:
The two main reasons lungs cannot meet tissue's O2 needs are V/Q mismatch and changes in lung compliance and resistance.
Step-by-step explanation:
Lungs are unable to meet the tissue's oxygen needs due to two main reasons:
- V/Q mismatch: This occurs when there is a mismatch between ventilation (airflow to the alveoli) and perfusion (blood flow to the capillaries surrounding the alveoli). If there is inadequate ventilation or perfusion in certain regions of the lungs, oxygen cannot efficiently diffuse across the respiratory membrane, leading to decreased oxygen delivery to the tissues.
- Decreased compliance and increased resistance: Changes in the compliance and resistance of the lungs can affect breathing and gas exchange. For example, in restrictive diseases like fibrosis, the lungs become stiff and less compliant, making it harder for air to be inhaled. In conditions such as asthma or emphysema, the airways become obstructed, increasing resistance and hindering the flow of air. These alterations can impede the delivery of oxygen to the tissues.