Question

4. Wheezing Wynona

Wynona, a 62 year-old female, comes to the clinic complaining of fatigue and persistent shortness of breath, which becomes worse during exercise. She has a history of respiratory infections and has a chronic cough that is worse in the morning. She worked for 20 years in an automobile manufacturing plant and was laid off 5 years ago. Wynona has smoked cigarettes since he was a teenager and currently estimates smoking one pack of cigarettes a day.

8. [1 point] What would you expect Wynona’s Arterial Blood Gas (ABG) test results to reveal (i.e. serum pH, PCO₂, PO₂ and serum HCO₃^-)?

9. In the case of an exacerbation of her condition would providing Wynona with pure oxygen be recommended? Explain how such a pure oxygen treatment would affect her ABG values.

10. Certain long-acting Beta-adrenergic agonists used to treat COPD trigger bronchodilation by i) inhibiting myosin kinase and ii) blocking membrane Ca²⁺ channels in bronchiolar smooth muscle cells. Explain how each of these actions will promote relaxation in smooth muscle cells.

Answer 1

Her arterial blood gas :

pH : Decreased.

pCO2 : Increased.

pO2 : Decereased.

serum HCO3 : increased.

From the above mentioned symptoms, it is obvious that the patient is suffering from Respiratory acidosis, which is a condition that occurs when the lungs cannot remove enough CO2 produced by the body as result CO2 accumulates in the body because of which pH decreases, there be could decrease in oxygen levels because of the fact that there is improper exchange of gases in the alveoli and as body's compensation mechanism, serum bicarbonate levels could be increased.

Pure oxygen would be recommended, especially if their oxygen saturation is low (mostly in condition like COPD oxygen saturation is low), by giving pure oxygen, pO2 level increases, which in turn can cause pCO2 levels to drop, so that pH can be increased..

Beta-adrenergic agonist are drugs of choice in a condition like COPD, they are classified as bronchodilators,( smooth muscle relaxation) which means they will dilate the airways in the lungs so that breathing becomes easy. When there is increased calcium ions than these calcium ion binds to calmodulin, Calcium-calmodulin activates myosin light chain kinase,  an enzyme that is capable of phosphorylating myosin light chains (MLC) in the presence of ATP, this leads to cross bridge formation as a result muscle contraction occurs. Vascular smooth muscle relaxation occurs when there is reduced phosphorylation of MLC. This can result from reduced release of calcium by the SR or reduced calcium entry into the cell, and inhibition of MLCK by increased intracellular concentration of cAMP.