Final answer:
Impaired oxygen diffusion with normal breathing is most commonly seen at high altitudes due to lower partial pressure of oxygen. Special physiological adaptations help maintain adequate oxygen delivery to tissues. External respiration involves oxygen and carbon dioxide exchanging places through diffusion based on concentration gradients.
Step-by-step explanation:
Impaired oxygen diffusion with normal air movement in and out of the lungs is most often observed at high altitudes. This happens because the partial pressure of oxygen is lower at high altitudes, resulting in a reduced difference in partial pressures between the alveoli and blood. Consequently, less oxygen crosses the respiratory membrane, and fewer oxygen molecules are bound by hemoglobin. However, bodily adaptations such as increased proportions of oxygen release into tissues and increased production of 2,3-BPG help maintain sufficient oxygen delivery to tissues. Factors like V/Q mismatch, reduced lung compliance, or increased airway resistance can also impair gas exchange without necessarily affecting the amount of air entering or exiting the lungs.
Gas exchange during respiration includes external respiration, where gas exchange between the blood and the body's cells is driven by diffusion. Oxygen diffuses from a higher concentration in the alveoli to a lower concentration in the capillaries, where it binds to hemoglobin in red blood cells (RBCs). Conversely, carbon dioxide diffuses from a higher concentration in the blood to a lower concentration in the lungs to be exhaled.