Question 266#

You are asked to design a study to assess whether living near electricity pylons is a risk factor for childhood - leukaemia.

What is the most appropriate type of study design?

A. Cross-over trial

Correct Answer D:

As the outcome (childhood leukaemia) is relatively rare a cohort study would take an extremely long time to provide significant results.

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

Question 267#

You are a ST1 doctor in medicine. Whilst on-call you review a 60-year-old woman who is known to have COPD. She has been admitted with an infective exacerbation and has not responded to nebulizers and intravenous aminophylline. Her most recent blood gases show a worsening respiratory acidosis. You feel that non-invasive ventilation (NIV) is needed and bleep the on-call physio. After discussing the blood gas results over the phone she says that NIV is not indicated in her opinion and refuses to set it up.

What is the most appropriate action?

A. Phone her back in 30 minutes and exaggerate the clinical picture to persuade her to come in

Correct Answer D:

By far the best option here is to speak to the consultant on-call. The physio may be experienced in providing NIV but it is ultimately a medical decision about whether to start a treatment.  

Accepting her opinion is a poor option as she has not reviewed the patient herself and is only giving an opinion on the basis of blood gases. 

Setting up NIV equipment requires training. If done incorrectly it could potentially harm a patient.

Transferring an acutely unwell patient simply because the physio won't come in is not appropriate. Lying about clinical information is a very poor option. 

Question 268#

Dobutamine is an example of:

A. Alpha-1 agonist

Correct Answer E:

Adrenoceptor agonists:

Alpha-1 agonists:

• Phenylephrine

Alpha-2 agonists:

• Clonidine

Beta-1 agonists:

• Dobutamine

Beta-2 agonists:

• Salbutamol

Beta-3 agonists:

• Being developed, may have a role in preventing obesity (stimulation causes lipolysis) 

Question 269#

Which one of the following best describes the Hering-Bruer reflex?

A. Lung distension causing slowing of the respiratory rate

Correct Answer A:

Respiratory physiology: control:

Control of respiration:

• Central regulatory centres
• Central and peripheral chemoreceptors
• Pulmonary receptors

Central regulatory centres:

• Medullary respiratory centre
• Apneustic centre (lower pons)
• Pneumotaxic centre (upper pons)

Central and peripheral chemoreceptors:

• Central: raised [H+] in ECF stimulates respiration
• Peripheral: carotid + aortic bodies, respond to raised pCO₂ & [H⁺], lesser extent low pO₂

Pulmonary receptors:

• Stretch receptors, lung distension causes slowing of respiratory rate (Hering-Bruer reflex)
• Irritant receptor, leading to bronchoconstriction
• Juxtacapillary receptors, stimulated by stretching of the microvasculature

Question 270#

What is the most common adverse effect experienced by women taking the progestogen only pill?

A. Irregular vaginal bleeding

Correct Answer A:

Progestogen only pill: advantages/disadvantages:

Advantages:

• Highly effective (failure rate = 1 per 100 woman years)
• Doesn't interfere with sex
• Contraceptive effects reversible upon stopping
• Can be used whilst breast-feeding
• Can be used in situations where the combined oral contraceptive pill is contraindicated e.g. in smokers > 35 years of age and women with a history of venous thromboembolic disease

Disadvantages:

• Irregular periods: some users may not have periods whilst others may have irregular or light periods. This is the most common adverse effect
• Doesn't protect against sexually transmitted infections
• Increased incidence of functional ovarian cysts
• Common side-effects include breast tenderness, weight gain, acne and headaches. These symptoms generally subside after the first few months