Asthma & COPD MCQs

Methacholine is a cholinergic agonist, which causes constriction of bronchial smooth muscle. Bronchoconstriction reduces airway radius, which increases airway resistance, and thus the resistive work of breathing. Methacholine-induced bronchoconstriction decreases the anatomic deadspace but has no significant effect on the lung compliance, and thus does not affect the elastic work of breathing. Reference: Ganong, pp 649-650, 654, 657-659. Levitzky, pp 34-36, 49-50.

The A-a O2 gradient is the partial pressure difference between the alveolar gas and arterial blood. The PaO2 has been measured. The alveolar oxygen tension must be calculated using the modified alveolar gas equation PAO2 = PIO2 - PaCO2/ R PAO2 = [0.21 x (760 - 47 mmHg)] - 60 mmHg/0.8 PAO2 = 150 mmHg - 75 mmHg = 75 mmHg (A-a) O2 gradient = 75 mmHg - 60 mmHg = 15 mmHg The patient's low arterial oxygen tension (hypoxemia; hypoxic hypoxia) results from a low PAO2 due to hypoventilation (as evidenced by the elevated PaCO2), and thus the (A-a) O2 gradient is within the normal range. Reference: Levitzky, pp 75, 180-181, 262.

This patient having essential tremor which is symmetrical, worsens with voluntary movements, and resolves completely at rest. Increased activation of β adrenoceptors has been implicated in essential tremor, and management commonly involves administration of propranolol. However, the more selective β1 blocker metoprolol may be equally effective and is more suitable in a patient with pulmonary disease like asthma. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg no. 511

There is a mild respiratory acidosis (pH > 7.3 and pCO2 > 60 mmhg) and base excess is also not elevated (in this case only -1). There is metabolic compensation, as indicated by a high bicarbonate ( >30). The patient's history of COPD suggests that he has chronic hypoxia and chronic CO2 retention, hence causing the picture of chronic respiratory acidosis. Reference : Harrison's Principles of Internal Medicine, 21 st Ed, Ch: 55, Pg: 359

The most common presentation of extrapulmonary TB in both HIV-seronegative individuals and HIV- infected patients (35% of cases worldwide and >40% of cases in the United States in recent series), lymph node disease is particularly frequent among HIV-infected patients and among children. In the United States, besides children, women (particularly non-Caucasians) seem to be especially susceptible Once caused mainly by M. bovis, tuberculous lymphadenitis today is due largely to M. tuberculosis. Lymph node TB presents as painless swelling of the lymph nodes, most commonly at posterior cervical and supraclavicular sites (a condition historically referred to as scrofula) Reference : Harrison's Principles of Internal Medicine, 21 st Ed, Ch: 178 Pg: 1364

The first line anti tubercular drugs are: INH,rifampicin, pyrazinamide, ethambutol, streptomycin. The second line agents are the drugs that are having a low effectiveness and tolerability and hence are used only for the treatment of resistant tuberculosis. The WHO has categorized them into 3 groups. Group A: Fluoroquinolones(Moxifloxacin and levofloxacin). Linezolid, Bedaquiline Group B: Clofazimine and cycloserine Group C: Delamanid, Imipenem-cilastatin/meropenem, amikacin/streptomycin, prothionamide and PAS. The first line agents Ethambutol and pyrazinamide are also included in group c. High dose INH is also used for the treatment of MDR TB

Ans. is 'a' i.e., To avoid emergence of persistors Two phase chemotheraphv o There are two phase of treatment of tuberculosis i) Intensive phase This is short phase in the early course of treatment and lasts for 1- 3 months. Three or more drugs are given to kill as many bacilli as possible, which prevents emergence of persisters. The risk of relapse is also lessened. Continuation phase It is aimed at sterilizing the smaller number of dormant or persisting bacilli.

Ans. is 'a' i.e., Prevent resistance o Multidrug treatment in TB is given to ? i) Prevent emergence of persisters ii) Prevent relapse iii) Prevent emergence of resistance iv) shorten the duration of treatment