Gas Exchange across Respiratory Surfaces

Free Response

What does FEV1/FVC measure? What factors may affect FEV1/FVC?


FEV1/FVC measures the forced expiratory volume in one second in relation to the total forced vital capacity (the total amount of air that is exhaled from the lung from a maximal inhalation). This ratio changes with alterations in lung function that arise from diseases such as fibrosis, asthma, and COPD.

What is the reason for having residual volume in the lung?


If all the air in the lung were exhaled, then opening the alveoli for the next inspiration would be very difficult. This is because the tissues would stick together.

How can a decrease in the percent of oxygen in the air affect the movement of oxygen in the body?


Oxygen moves from the lung to the bloodstream to the tissues according to the pressure gradient. This is measured as the partial pressure of oxygen. If the amount of oxygen drops in the inspired air, there would be reduced partial pressure. This would decrease the driving force that moves the oxygen into the blood and into the tissues. P O 2 is also reduced at high elevations: P O 2 at high elevations is lower than at sea level because the total atmospheric pressure is less than atmospheric pressure at sea level.

If a patient has increased resistance in his or her lungs, how can this be detected by a doctor? What does this mean?


A doctor can detect a restrictive disease using spirometry. By detecting the rate at which air can be expelled from the lung, a diagnosis of fibrosis or another restrictive disease can be made.