EXAM TIPS & FEEDBACK
The questions covered in the SGD reflect what can possibly appear on exams. Past exam questions are made available to students in this section for self-study purposes. Since some questions are used repeatedly in exams, students are advised to try and answer them whenever time permits. The more students are acquainted with answering these questions, the more prepared they will be in upcoming exams. However, answering these questions does NOT guarantee that you will pass future exams. A lot will depend on how much you actually understand about the topic, underlying and related pathophysiology and compensatory mechanisms.
Year | Question | Time |
2002/3 | ? | |
2003/4 | ABG: Interpret the acid-base status & compensation: pH 7.29, pCO2 50 mmHg, [HCO3-] 25 mmol/L | 10 min. |
2004/5 | Describe the mechanisms of hydrogen ion excretion by the kidney. | 15 min. |
2005/6 | Describe the role of the respiratory system in acid-base homeostasis. | 15 min. |
2006/7 | No essay question | |
2007/8 | No essay question | |
2008/9 | ? |
Problems faced by students and errors made on acid-base exams
Problems encountered by students during exams and errors & inconsistencies discovered by examiners are highlighted in this section so that students become aware of persistent problems when learning this topic and work around them. It is hoped that students do not repeat these same mistakes in future.
General mistakes: Poor English, flow of answers & reasoning, haphazard answer, poor handwriting, untidy, misspellings, use of red/pink ink
1. Need to improve English in order to write meaningful sentences.
2. Not organized and writing begins all over the page. Cramped writing.
3. Poor handwriting makes it difficult to mark answer.
4. Sub-headings are not underlined, not properly numbered or not indicated.
5. Too many cancelled words and changes in text make reading difficult.
6. A large portion of text is crossed out (cancelled) on every page.
7. Cancelled portion of graphs.
8. Equations are not properly written or are not labeled. Unclear terms used.
9. Answer written is not applicable (does not answer the question, irrelevant).
10. Terrible disjointed flowcharts. Or no diagram.
Category 1: Acid-base symbols, equations, equilibriums, imbalances, shifts, relationships between HH terms and acid-base changes in blood
1. Unsure of symbols, inventing new but meaningless symbols: PHCO3-, [PCO2]
2. Problem understanding equilibrium shifts (how & why, right shift, left shift).
3. Unsure of terms used in the Henderson-Hasselbalch (HH) equation.
4. Buffer ratio: Wrong primary lesion with wrong compensatory mechanism.
5. Wrong statements about HH equation and equilibrium shifts.
6. Wrong spelling: alkolisis, respiratory alkolisis
7. Undecided which terms to use to describe specific changes: decrease vs. increase, low vs. high, normal vs. abnormal, partial vs. full, increase vs. decrease toward normal
8. Contradictory relationship: Alkaline load causes ↓pH; pH↑ due to [H]↑
9. False statement: When the pH in blood increase, the concentration of the H+ ions will increase.
Category 2: Acid load, alkali load, ingestion, intake, uptake
1. Long definitions.
2. Incorrect words: intake vs. uptake.
3. Vague descriptions:
- increase uptake of acid
- in acidic situation
- increase uptake of alkaline food
- during hypoxia and acclimatization.
- When someone ingest the acidic food.
Category 3: Problem understanding concepts & definitions on ventilation (hyperventilation, hypoventilation) and relating them to acid-base changes
1. Unable to grasp the meaning of exhalation and inhalation.
2. Unable to relate role of lung to PCO2 changes in blood.
3. Misunderstands ventilation. Incorrect concept about PCO2 and ventilation.
4. Wrong statement about the effect of hypoventilation on PCO2.
5. Vague statements:
- prevent loss of CO2 by respiratory mechanism.
- Increase loss of CO2 by respiratory mechanism.
6. Conflicting statements:
- ↑HCO3- in metabolic acidosis;
- ↓HCO3- in metabolic alkalosis.
7. Wrong compensatory response in hyper- & hypoventilation.
8. Wrong primary lesion with wrong compensatory mechanism.
9. Order of compensatory mechanisms is reversed.
10. Descriptive terms for blood are carelessly used for lung action.
Category 4: Problem understanding chemoreceptors
1. Jumble up chemoreceptors (central & peripheral).
2. Incorrect detection of substances by chemoreceptors.
3. Problem relating ventilation with suppression & stimulation of chemoreceptors.
4. Sequence of events following stimulation of chemoreceptors.
Category 5: Wrong answers
1. Answers on Rbc metabolism instead of respiratory system.
2. Answers on renal instead of respiratory system.
3. Answers on hypokalaemia & hyperaldosteronism instead of respiratory system.
Prof Faridah
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