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Question 1
Incorrect
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Carbon dioxide is transported in the blood approximately:
Your Answer: 80% as bicarbonate ions, 15% as carbamino compounds and 5% dissolved in plasma.
Correct Answer: 60% as bicarbonate ions, 30% as carbamino compounds and 10% dissolved in plasma.
Explanation:Carbon dioxide is transported in the blood from tissues to the lungs in three ways as bicarbonate ions (60%), as carbamino compounds with proteins (30%) or simply dissolved in plasma (10%).
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 2
Incorrect
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The following all cause a left shift in the oxygen dissociation curve EXCEPT for:
Your Answer: Decrease in PCO 2
Correct Answer: Decrease in pH
Explanation:An increased affinity of haemoglobin for oxygen, shown by a left shift in the oxygen dissociation curve, is caused in the lungs by a rise in pH, a fall in PCO2,a decrease in temperature and a decrease in 2,3 -DPG. Carbon monoxide (CO) binds 240 times more strongly than O2to haemoglobin and by occupying O2-binding sites, reduces oxygen capacity. CO also increases oxygen affinity, shifting the oxygen haemoglobin curve to the left and making O2release to tissues more difficult.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 3
Correct
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Regarding airway resistance, which of the following statements is CORRECT:
Your Answer: Airway resistance is predominantly determined by the radius of the airway as described by Poiseuille's law.
Explanation:Flow through airways is described by Darcy’s law which states that flow is directly proportional to the mouth-alveolar pressure gradient and inversely proportional to airway resistance. Airway resistance is primarily determined by the airway radius according to Poiseuille’s law, and whether the flow is laminar or turbulent. Parasympathetic stimulation causes bronchoconstriction and sympathetic stimulation causes bronchodilation, but mediated by beta2-adrenoceptors. Muscarinic antagonists e.g. ipratropium bromide cause bronchodilation.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 4
Incorrect
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Regarding gas exchange at the alveolar-capillary membrane, which of the following statements is CORRECT:
Your Answer: Movement of particles across the membrane ceases once equilibrium has been reached.
Correct Answer: Transfer of oxygen is usually perfusion-limited.
Explanation:Gas exchange between alveolar air and blood in the pulmonary capillaries takes place by diffusion across the alveolar-capillary membrane. Diffusion occurs from an area of high partial pressure to an area of low partial pressure, thus the driving force for diffusion is the alveolar-capillary partial pressure gradient. Diffusion occurs until equilibrium is reached, but random movement of particles continues to occur and this is known as dynamic equilibrium. The diffusing capacity for oxygen (DLO2) cannot be measured directly but the rate of diffusion in the lungs can be estimated by measuring the diffusing capacity of the lungs for carbon monoxide (DLCO), not by measuring total lung capacity. The rate of transfer of a gas may be diffusion or perfusion limited; carbon monoxide transfer is diffusion-limited, oxygen transfer is usually perfusion-limited.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 5
Incorrect
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Compliance is greater in all but which one of the following:
Your Answer: Elderly
Correct Answer: Pulmonary oedema
Explanation:Compliance changes at different lung volumes. Initially at lower lung volumes the compliance of the lung is poor and greater pressure change is required to cause a change in volume. This occurs if the lungs become collapsed for a period of time. At functional residual capacity (FRC) compliance is optimal since the elastic recoil of the lung tending towards collapse is balanced by the tendency of the chest wall to spring outwards. At higher lung volumes the compliance of the lung again becomes less as the lung becomes stiffer. At all volumes, the base of the lung has a greater compliance than the apex. Patients with emphysema have increased compliance. Compliance is affected by a person’s age, sex and height.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 6
Correct
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Which of the following is NOT an indication for a H1 receptor antihistamine:
Your Answer: Gastroesophageal reflux disease
Explanation:Antihistamines are competitive inhibitors at the H1-receptor (in contrast to H2 receptor antagonists used to decrease gastric acid secretion in gastroesophageal reflux disease).
Indications:
Allergic rhinitis and conjunctivitis
Urticarial rashes, pruritus, insect bites and stings
Angioedema
Anaphylaxis (second line adjunct to adrenaline)
Nausea/vomiting and prevention of motion sickness
Insomnia -
This question is part of the following fields:
- Pharmacology
- Respiratory
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Question 7
Incorrect
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Which of the following states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each of the gases in the mixture:
Your Answer: Boyle's law
Correct Answer: Dalton's law
Explanation:Dalton’s law states that when two or more gases, which do not react chemically, are present in the same container, the total pressure is the sum of the partial pressures of each gas.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 8
Incorrect
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Regarding dynamic compression of the airways, which of the following statements is CORRECT:
Your Answer: It is brought about by reflex activation of parasympathetic nerves.
Correct Answer: It occurs during forced expiration.
Explanation:Dynamic compression occurs because as the expiratory muscles contract during forced expiration, all the structures within the lungs, including the airways, are compressed by the positive intrapleural pressure. Consequently the smaller airways collapse before the alveoli empty completely and some air remains within the lungs (the residual volume). Physiologically this is important as a completely deflated lung with collapsed alveoli requires significantly more energy to inflate. Dynamic compression does not occur in normal expiration because the intrapleural pressure is negative throughout the whole cycle.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 9
Incorrect
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A 33 year old lady with a known nut allergy was having dinner at a Thai restaurant. She suddenly complained of lip and tongue swelling and difficulty breathing and is brought to ED by ambulance with suspected anaphylaxis. She received intramuscular adrenaline in the ambulance.
The most appropriate doses of the second line treatments for anaphylaxis are which of the following?Your Answer: 5 mg chlorphenamine and 200 mg hydrocortisone
Correct Answer: 10 mg chlorphenamine and 200 mg hydrocortisone
Explanation:Second line drugs to reduce the severity and duration of anaphylactic symptoms are intravenous or intramuscular chlorpheniramine and hydrocortisone. The recommended dose is 10 mg chlorpheniramine and 200 mg hydrocortisone in adults.
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This question is part of the following fields:
- Pharmacology
- Respiratory
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Question 10
Incorrect
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The second generation antihistamine, cetirizine is a less-sedating antihistamine than the older antihistamine, chlorphenamine because:
Your Answer:
Correct Answer: It is less lipid-soluble so less able to cross the blood brain barrier.
Explanation:All older antihistamines such as chlorphenamine cause sedation. The newer antihistamines e.g. cetirizine cause less sedation and psychomotor impairment than the older antihistamines because they are much less lipid soluble and penetrate the blood brain barrier only to a slight extent.
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This question is part of the following fields:
- Pharmacology
- Respiratory
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SESSION STATS - PERFORMANCE PER SPECIALTY
