Question

Emma Norton, aged 26, is admitted to hospital with an acute exacerbation of her COPD. Using your knowledge of the respiratory system (M2) and the cardiovascular system (M3), please answer the following questions below. Be sure to clearly label the different parts:

PART A / Emma undergoes a pulmonary lung function test. How would her total lung capacity test and her FEV1/FVC values compare to normal physiological values?

PART B / In hospital, Emma is placed on oxygen but develops respiratory depression. Explain why Emma stops breathing when she is administered oxygen.

PART C / Emma's COPD has caused pulmonary hypertension and subsequent failure of the right ventricle. What are the roles of venous pressure and capillary hydrostatic pressure in causing edema?

PART D /  Emma's right ventricular failure has caused a decrease in cardiac output. Explain which hormonal system will be activated and how it compensate for this.

Answer 1

Part- A:

Total lung capacity is the maximum volume of air the lungs can accommodate or in other wors i the sum of all volume of air in lungs after maximum inspiration. The normal value varies between 4-6L. The FEV1/FVC ratio also called as as Tiffeneau-Pinelli index is the ratio of the forced expiratory volume in the first one second to the forced vital capacity of the lungs. This explains the percentge of lung size in first second. Emma's pathological condition would be indicated by lower FEV1/FVC ratio (<70%) represent obstruction in the airways as in asthma, COPD  emphysema that reduces the lung recoil pressure

Part B:

Acute exacerbation of COPD leads to CO2 retention leads to respiratory depression. Other most common reason for this is opiate overdose also accompanied with reduced conscious level. Emma's condition requires the removal of hypoxia due to COPD with supplemental O2 often ending up in hypoventilation which in turn leads to hypercarbia, apnea ultimately cause respiratory failure and Emma stops breathing .

Part C:

When outward venous hydrostatic pressure exceeds the level of oncotic pressure, accumulation of fluid in tissues would result manifesting as peripheral edema or otherwise elevated central venous pressures. Capillary hydrostatic pressure (CHP) is the pressure exerted by blood on the capillary wall influences the fluid accumulation when increased venous pressures, higher voume conditions, heart failure and venous obstruction. Decreased plasma oncotic pressure due to hypoproteinemia also account for edema.

Part D:

Heart failure causes reduced cardiac output is regulated via feedback mechanisms in order to maintain homeostatic arterial pressure by triggering vasoconstrictions innervated by sympathetic adrenergic nervous system resulting in increasing systemic vascular resistance. This resulting in activation of specific endocrine component called renin, angiotensin, and aldosterone triggers vasoconstriction which stimulate more sodium and water resorption.