Question 296#

What is the initial physiological response to the Valsalva manoeuvre?

A. Reduction in cardiac output

Correct Answer D:

Valsalva manoeuvre:

The Valsalva manoeuvre describes a forced expiration against a closed glottis. This leads to increased intrathoracic pressure which in turn has a number of effects on the cardiovascular system.

Uses:

• To terminate an episode of supraventricular tachycardia
• Normalizing middle-ear pressures

Stages of the Valsalva manoeuvre:

1. Increased intrathoracic pressure
2. Resultant increase in venous and right atrial pressure reduces venous return
3. The reduced preload leads to a fall in the cardiac output (Frank-Starling mechanism)
4. When the pressure is released there is a further slight fall in cardiac output due to increased aortic volume
5. Return of normal cardiac output

Question 297#

A study is proposed to ascertain whether childhood obesity in girls increases the risk of polycystic ovarian syndrome.

What is the most appropriate form of study design?

A. Cohort study

Correct Answer A:

A cohort study would provide more robust evidence than a case-control study.

Study design:

The following table highlights the main features of the main types of study:

Question 298#

Which one of the following is least likely to cause hypernatraemia?

A. IV saline infusion

Correct Answer C:

Hypernatraemia:

Causes of hypernatraemia:

• Dehydration
• Osmotic diuresis e.g. hyperosmolar non-ketotic
• Diabetic coma diabetes insipidus
• Excess IV saline

Question 299#

A 52-year-old obese lady with type 2 diabetes mellitus is interested in changing her diet.

Which one of the following foods has the highest glycaemic index?

A. Baked potato

Correct Answer A:

Whilst white rice has a glycaemic index of 87 brown rice has a much lower value of 58.

Glycaemic index:

The glycaemic index (GI) describes the capacity of a food to raise blood glucose compared with glucose in normal glucose-tolerant individuals. Foods with a high GI may be associated with an increased risk of obesity and the post-prandial hyperglycaemia associated with such foods may also increase the risk of type 2 diabetes mellitus. 

The glycaemic index is shown in brackets. Glucose, by definition, would have a glycaemic index of 100.

Question 300#

Of the following scenarios, which one would indicate it was inappropriate for the patient to take an airline flight?

A. A 54-year-old woman who had a laparoscopic cholecystectomy 5 days ago

Correct Answer B:

Following the application of a plaster cast patients should wait 24 hours before short flights (< 2 hours) and 48 hours before longer flights. This is due to the fact that air may be trapped beneath the cast.

Fitness to fly:

The Civil Aviation Authority (CAA) has issued guidelines on air travel for people with medical conditions; please see the link provided.

Cardiovascular disease:

• Unstable angina, uncontrolled hypertension, uncontrolled cardiac arrhythmia, decompensated heart failure, severe symptomatic valvular disease: should not fly
• Uncomplicated myocardial infarction: may fly after 7-10 days
• Complicated myocardial infarction: after 4-6 weeks
• Coronary artery bypass graft: after 10-14 days
• Percutaneous coronary intervention: after 5 days

Respiratory disease:

• Pneumonia: should be 'clinically improved with no residual infection'
• Pneumothorax: absolute contraindication, the CAA suggest patients may travel 2 weeks after successful drainage if there is no residual air. The British Thoracic Society used to recommend not travelling by air for a period of 6 weeks but this has now been changed to 1 week post check x-ray

Pregnancy:

• Most airlines do not allow travel after 36 weeks for a single pregnancy and after 32 weeks for a multiple pregnancy
• Most airlines require a certificate after 28 weeks confirming that the pregnancy is progressing normally

Surgery:

• Travel should be avoided for 10 days following abdominal surgery
• Laparoscopic surgery: after 24 hours
• Colonoscopy: after 24 hours
• Following the application of a plaster cast, the majority of airlines restrict flying for 24 hours on flights of less than 2 hours or 48 hours for longer flights

Haematological disorders:

• Patients with a haemoglobin of greater than 8 g/dl may travel without problems (assuming there is no coexisting condition such as cardiovascular or respiratory disease)