Alveolar Dead Space

A et pco 2 reflects alveolar dead space as a result of a temporal a spatial and an alveolar mixing defect in the normal lung.

Alveolar dead space. Dead space is the portion of each tidal volume that does not take part in gas exchange. Normal values of a et pco2 is 2 5 mm hg. Alveolar dead space is the volume of gas within unperfused alveoli and thus not participating in gas exchange either.

The ratio of physiologic dead space to tidal volume is usually about 1 3. Alveolar dead space increases with tidal volume so that the sum of anatomical and alveolar physiological dead space remains about 32 of tidal volume fig. Monitoring clinical progress of a critical patient.

Alveolar dead space is sum of the volumes of those alveoli which have little or no blood flowing through their adjacent pulmonary capillaries i e alveoli that are ventilated but not perfused and where as a result no gas exchange can occur. General anesthesia multifactorial including loss of skeletal muscle tone and bronchoconstrictor tone. Anatomical dead space the airways of the mouth nose pharynx larynx trachea bronchi and bronchioles.

It is usually negligible in the healthy awake patient. The cause of the increase in alveolar dead space during uncomplicated general anaesthesia is not immediately obvious. Hence a et pco 2 is an indirect estimate of v q mismatching of the lung.

Alveolar dead space the difference between anatomical dead space and physiologic dead space representing the space in alveoli occupied by air that does not participate in oxygen carbon dioxide exchange alveolar ventilation. It varies in different parts of the lungs and under different conditions. A et pco2 as an index of alveolar dead space there is a positive relationship between alveolar dead space and a et pco 2.

Anatomic dead space is the total volume of the conducting airways from the nose or mouth down to the level of the terminal bronchioles and is about 150 ml on the average in humans.