Question

Case Study: Respiratory distress

Learning Outcomes:

Apply physiological and biochemical knowledge to analyze case studies on pathological states.

Communicate biological information effectively in written work.

Apply physiology to relevant societal impacts.

Directions: Please read the provided case study and then answer the following questions. The answers should be complete but do not feel that you need to write extensive paragraphs. Concise answers convey the information fine.

An 18--year-old college student comes into the doctor’s office concerned about her breathing. She has experienced intermittent, reversible episodes of chest tightness with coughing, wheezing, and hyperpnea (deep, labored breathing). She states that expiration is more difficult than inspiration. She is most comfortable sitting forward with arms leaning on some support. X-rays revealed mild overinflation of the chest. Results from laboratory and pulmonary function tests are as follows:

Frequency	20 breaths/min
Vital capacity (VC)	2.9 L
FEV1.0	1.4 L
FEV1.0/FVC	56%
Functional residual capacity (FRC)	3.89 L
Total lung capacity (TLC)	6.82 L
PaO2	71 mm Hg
PaCO2	25 mm Hg
Pulse	108 b/min
BP	120/76 mm Hg

Intermittent use of a bronchial smooth muscle dilator (1:1000 epinephrine by nebulizer) for several days caused marked improvement, resulting in the following laboratory and pulmonary function tests:

VC	4.15 L
FEV1.0	3.1 L
FEV1.0/FVC	>75%
FRC	3.7 L
TLC	5.96L
PaO2	88 mm Hg
PaCO2	37 mm Hg
Pulse	129 b/min
BP	122/78 mm Hg

1. What disorder does this individual have? Is it primarily obstructive or restrictive? Why?

2. How is the residual volume (RV) determined?

a. What is this individual’s RV before the bronchiodilator?

b. What is this individual’s RV after the bronchiodilator?

3. Why is expiration more difficult than inspiration in this individual?

4. What is indicated by the marked improvement in respiratory function with the bronchiodilator ?

5. What happened to the individual’s pulse rate when given the bronchiodilator and why?

6. What causes the hypoxemia and the hypocapnemia in this person?

7. A beta2 specific-adrenergic agent was prescribed for further use. Based on your knowledge of beta1 and beta2 receptors, why is this a good suggestion?

8. An anticholinergic agent was also suggested. How might this help the breathing problem?

Answer 1

1. This individual have a obstructive disorder because he/she have difficulty in exhaling all the air from the lungs.

2. Residual volume is determined by

RV= Functional residual capacity - expiratory volume.

a) Individuals RV before the bronchodilator : 3.89 - 1.4 = 2.49L

b) Individual RV after the bronchodilator: 3.7-3.1 = 0.6 L

3. Expiration is more difficult in this individual because airways are narrowed and there is less amount of space for the movement of air in and out of the lungs resulting in chest tightness and wheezing sound.

4. It is indicated that because of bronchodilators client's bronchi and bronchioles are dilated and more airflow is to the lungs.

5. After administration of bronchodilator individual's pulse rate gets high (tachycardia) because drugs like bronchodilator and beta 2 receptors causes stimulation of sympathetic receptors in heart resulting in tachycardia and palpitations.

6. Hypoxemia is the low amount of oxygen in the blood,this occur because of ventilation/perfusion mismatch resulting in low level of O₂ in blood.

Whereas,hypocapnemia is the low amount of CO₂ in the blood.Hypocapnemia occurs due to rapid breathing,breathing from mouth,anxiety resulting in hyperventilation.

7. Beta2 adrenergic receptors (ADRB₂) is a good suggestion because it helps in dilation of bronchial passages resulting in bronchodilation and it also helps in blocking allergic response in patients with asthma.

Beta2 receptors are located in the bronchioles of the lungs and Beta 1 receptors are located in the heart.

8. Anticholinergics helps in improving breathing problem as they bind to receptors present in lungs ( muscarinic receptors) and blocks the secretion of acetylcholine which in turn leads to bronchodilation.