Read More: How do you count the number of colonies on a plate? How does dead space affect alveolar ventilation?īackground. Alveoli with no perfusion have a V/Q of infinity (Q=0), whereas alveoli with no ventilation have a V/Q of 0 (V=0). What is significance of dead space?ĭead space has particular significance in the concept of ventilation (V) and perfusion (Q) in the lung, represented by the V/Q ratio. Ergo, increasing dead space has the same effect as reducing the tidal volume. Of the tidal volume, only the non-dead fraction participates in gas exchange. What happens when dead space is increased?Īt a fundamental level, increasing the dead space functionally indistinguishable from hypoventilation: Dead space is a fraction of the total tidal volume. Although multiple studies have failed to show this expected effect consistently, it is still widely used in cases of ARDS. How do you lower dead space?Īdjustments in ventilation rates and the use of positive end-expiratory pressure (PEEP) are used to decrease dead space. Other causes include pulmonary embolism, pulmonary hypotension, and ARDS. The commonest causes of increased alveolar deadspace are airways disease–smoking, bronchitis, emphysema, and asthma. The end result is the smaller distal airways with a tendency to early collapse, dilated alveolar ducts, and fewer gas exchange surfaces. … Elastic elements of the lung parenchyma are lost with age. However, expiratory flow changes very little. Why does dead space increase with age?ĭead space increases with age because the larger airways increase in diameter. The normal value is in the range of 130 to 180 mL and depends on the size and posture of the subject. The anatomic dead space is the gas volume contained within the conducting airways. What is anatomical dead space in the lungs? This happens when there is a lack of blood flow where the alveoli have enough air to oxygenate blood or there is a lack of air in an area where the blood flow is normal.

Physiological dead space or physiological shunts, arise from a functional impairment of the lung or arteries.

Causes of dead space ventilation