Pulmonary Function Tests MCQs

Both the central chemoreceptors, located on or near the ventral surface of the medulla, and the peripheral chemoreceptors, in the carotid and aortic bodies, cause an increase in ventilation in response to an increase in PaCO2. The peripheral chemoreceptors also cause an increase in ventilation in response to a decrease in arterial pH and a decrease in PaO2, but the central chemoreceptors are unresponsive to hypoxemia and do not cause an increase in ventilation in response to a decrease in arterial pH because the blood-brain barrier is relatively impermeable to hydrogen ions. Neither the central chemoreceptors nor the carotid bodies are stimulated by a decrease in arterial blood pressure or O2 content. Reference: Ganong, pp 662, 672-677, 686-688. Levitzky, pp 114-116, 180-182, 201-210.

The alveoli at the apex of the lung are larger than those at the base so their compliance is less. Because the compliance is reduced, less inspired gas goes to the apex than to the base. Also, because the apex is above the heart, less blood flows through the apex than through the base. However, the reduction in airflow is less than the reduction in blood flow, so that the V/Q ratio at the top of the lung is greater than it is at the bottom. The increased V/Q ratio at the apex makes PACO2 lower and PAO2 higher at the apex than they are at the base. Reference: Ganong, pp 643-644, 662-663, 686-688. Levitzky, pp 123-128. Stead et al., pp 25-27.

In order of frequency, the extrapulmonary sites most commonly involved in TB are the lymph nodes , pleura , genitourinary tract , bones and joints, meninges, peritoneum, and pericardium. Reference :Harrison's Principles of Internal Medicine, 21 st Ed, Ch: 178 Pg: 1364

In rh incompatibility, there will be hemolysis and the picture will be similar to any other hemolytic anemia. In hemolytic jaundice, in the blood we will get indirect bilirubinemia. Liver function tests will be normal. Since unconjugated bilirubin is bound to albumin, it will not be excreted in urine and hence urine will be colorless. Whatever bilirubin is formed will be conjugated by the liver and excreted through the bile, where in the gut it will be converted into stercobilin and subsequently to urobilin. A part of the urobilin will enter the systemic circulation where it will be excreted in the urine.

Digoxin follows first order kinetics and has a half-life of 36 to 48 hours in a patient with normal renal function. Sixty-five per cent of the drug absorbed remains in the system after one day. Subsequent doses gradually accumulate until a steady state is achieved after four to five days. The bioavailability of digoxin is around 70%. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 1949

Clubbing is not a feature of COPD, its presence should raise the suspicion of an underlying lung malignancy. Physical findings of COPD: Nicotine staining of fingernails Signs of respiratory distress: pursed lip breathing, accessory muscle use, tripod position, inspiratory in drawing of ribs (esp lower ribs, ka Hoover's sign) Cachexia (poor prognostic finding) Signs of hyper inflated lungs: barrel chest, hyper resonance on percussion Auscultation: coarse crepitations (fibrosis), polyphonic rhonchi Signs of right heart failure (cor pulmonale): Elevated JVP, Pedal edema, ascites. Labs may show a 2° polycythaemia and chronic respiratory acidosis with metabolic alkalosis. Reference: Harrison's Principles of internal medicine 21st edition, chapter. 292 page number. 2185

Because most inspired air is distributed to the middle and lower lung zones, these areas are most commonly involved in primary TB. In the majority of cases, the lesion heals spontaneously and becomes evident only as a small calcified nodule. Pleural reaction overlying a subpleural focus is also common. The Ghon focus, with or without overlying pleural reaction, thickening, and regional lymphadenopathy, is referred to as the Ghon complex. Reference : Harrison's Principles of Internal Medicine, 21 st Ed, Ch: 172 Pg: 1362

The patient has bronchiectasis , in which the common complication is difficulty expectorating, postural drainage of secretions is helpful. Reference : Harrison's Principles of Internal Medicine, 21 st Ed, Ch:290 Pg: 2175