Question

A 155 lb., 60-year-old man had a chronic productive cough, exertional dyspnea, mild cyanosis, and marked slowing of forced expiration. His pulmonary function and laboratory tests follow: Frequency 15 breaths/min Alveolar ventilation 4.1 L/min Vital capacity (VC) 2.2 L Functional residual capacity (FRC) 4.0 L Total lung capacity (TLC) 5.2 L Maximum inspiratory flow rate 252 L/min Maximum expiratory flow rate 21 L/min PaO2 63 mm Hg PaCO2 38 mm Hg Pulmonary function tests after bronchodilator therapy: Frequency 15 breaths/min Alveolar ventilation 4.25 L/min VC 2.4 L FRC 4.0 L TLC 5.2 L Maximum inspiratory flow rate 252 L/min Maximum expiratory flow rate 24 L/min PaO2 63 mm Hg PaCO2 37 mm Hg

1 What is the disorder of this man?

2 Is this mainly a restrictive or an obstructive disorder? Explain.

3 Why is the bronchodilator therapy ineffective for this patient?

4 What causes the hypoxemia?

5 Calculate the residual volume (RV) for this person before and after the bronchodilator therapy. RV = TLC - VC.

Answer 1

1	The person is suffering from emphysema.
2	It is a disorder-obstructive in nature, with very less degree of restriction as revealed by maximum inspiratory flow rate (63 % of normal) and maximum expiratory flow rate (7% of normal).
3	The main reason for ineffectiveness of bronchodilator therapy is because the person does not have bronchoconstriction. However, there is enhancement in destruction of alveoli.
4	The cause of hypoxia includes: Increase in functional residual capacity or residual volume A decrease in surface area of alveoli which hampers and reduces alveolar surface area available for exchange of gas.
5	RV=TLC-VC RV prior to bronchodilator therapy = 3.0 L RV after bronchodilator therapy = 2.8 L