apex vs base of lung dead space and ahunt

Here we will consider the more common causes.

Reduced ventilation can occur for a number of reasons. Hydrostatic pressure is decreased at the apex of the lung, resulting in decreased flow and decreased perfusionĪs perfusion increases with gravity, the apical and middle zones of the lung see the greatest relative increase in their perfusion rate with an increased cardiac output, such as during exercise.Ĭlinical Relevance – Reduced Ventilation of the Lungs.Pleural pressure is increased at the base of the lungs, resulting in more compliant alveoli and increased ventilation.Gravity triggers these changes in ventilation and perfusion through two different mechanisms:

As such the overall value in the average human lung is closer to 0.8. Areas of lung below the heart have increased perfusion relative to ventilation due to gravity, reducing the V/Q ratio. The different ratios for different areas are due to the relation of the area to the heart. This means that ventilation exceeds perfusion towards the apex, and that perfusion exceeds ventilation towards the base. For example, when standing up straight, the ratio is roughly 3.3 in the apex of the lung, and only 0.63 in the base. However, the ratio varies depending on the part of the lung concerned. The ideal V/Q ratio would be 1 for maximally efficient pulmonary function. The perfusion (Q) of the lungs refers to the total volume of blood reaching the pulmonary capillaries in a given time period. In an average man, the ventilation rate is roughly 6L/min. This is calculated by multiplying the tidal volume (volume of air inhaled and exhaled in a single breath) by the respiratory rate. The ventilation rate (V) refers to the volume of gas inhaled and exhaled from the lungs in a given time period, usually a minute.

Apex vs base of lung dead space and ahunt