Alveolar Ventilation-Perfusion Relationships

Running Head: ALVEOLAR VENTILATION-PERFUSION RELATIONSHIPS
ALVEOLAR VENTILATION-PERFUSION RELATIONSHIPS
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ALVEOLAR VENTILATION-PERFUSION RELATIONSHIPS1
The exchange of gases in between the alveoli of the lungs and the pulmonary capillary
blood occurs with the help of a mechanism coined as the diffusion. The diffusion of the two
gases that includes oxygen and the carbon dioxide takes place passively leading to occurrence of
the difference of concentration across the alveolar-capillary barrier (Aoki et al, 2018). These
differences in the concentration level are observed to be maintained by the alveolar ventilation
and the perfusion caused by the pulmonary capillaries.
The left-to-left anatomic shunt ultimately results in a slight drop in the PaO2 from a range
of 100 mmHg present in the end of the pulmonary capillaries to the 95 mmHg in the vein. The
A-a- gradient is mainly considered to help in the measurement of the slight drop in the oxygen
partial pressure levels caused by shunting in the alveoli (PAO2) to the pulmonary vein (PAO2).
These physiological conditions may lead to extreme V/Q ratios higher than the normal range,
which may cause disparities in breathing. It has also been observed that lowering the level of
ventilation of the shunted blood leads to the increase in the A-a gradient that ultimately leads to
the rise of hypoxemia in patients (Sarkar, Niranjan & Banyal, 2017), which becomes difficult to
control even with exterior supplementation of oxygen through oxygen therapy. Thereby, it
becomes very important for the healthcare officials to be more aware of the situation and
regularly check on the vitals to prevent any such occurrences.
The exchange of the gases in the alveoli occurs mainly due to the process of diffusion. It
has been observed that both the gases, oxygen and carbon dioxide have limited perfusion. The
deoxygenated blood coming from the pulmonary arteries has a 40 mmHg of PVO2 and the
alveolar air has been recorded to possess a PAO2 of 100 mmHg, which ultimately results in the
movement in the capillaries until the equilibration of the arterial blood at 100 mmHg (PAO2).
These conditions affect the membrane thickness and increases the solubility of the gases along