Question

Pathophysiology of Gas Exchange: what is the use of a Chest tube: what ABG’s labs are indicative of a pneumothorax: and what does pulse oximetry measure?

Answer 1

Transport of blood oxygen and carbondioxide is essential for internal respiration to occur. Oxygen is carried in the blood in chemical combination with hemoglobin and solution in plasma water.

Oxyhemoglobin is ans unstable compound that under certain conditions readily dissociates releasing oxygen. Factors that increase dissociation include low oxygen levels, low pH and raised temperature. In active tissues there is increased production of carbondioxide and heat, which leads to increased release of oxygen. In this way oxygen is available to tissues in greatest need. When oxygen leaves the erythrocyte, the deoxygenated hemoglobin turns purplish in colour.

Carbondioxide is one of the waste products of metabolism. It is excreted by the lungs and is transported by three mechanisms as bicarbonate ions, erythrocytes snd others dissolved in the plasma.

In pneumothorax, ABG results shows higher level of carbondioxide and low levels of oxygen, indicating hypoxaemia and hypercapnia.

A chest tube is used to to evacuate fluid and air from the pleural space and to restablish a negative intrapleural pressure so that the lung can reexpand.

Pulse oximetry is a noninvasive method and is used for determining arterial hemoglobin oxygen saturation. It is based on spectrophotometric measurement of the degree of oxygen which binds to hemoglobin at a point in time when the signal represents that of the arterial blood.