Exam Intelligence

Image via Wikipedia Critical Temperature is the temperature above which, no matter how much pressure you apply, you cannot force a gas to become a liquid. Interestingly enough, though, if you apply sufficiently high pressures, you can form a solid. Essentially, distinct liquid and solid phases of a substance no longer exist.

If you measure the vapour pressure of a substance at the critical temperature, that pressure is called the critical pressure. Alternatively it could be defined as the pressure which is required to liquefy a vapour at its critical temperature.

A substance is a vapour when it is in equilibrium with the substance in another phase, and a gas when there is no liquid or solid present. Therefore, by definition, except at the extremely high pressures mentioned above, any substance above its critical temperature, is a gas. A liquid does not have to boil, nor a solid to sublime (change state directly from solid to vapour/gas-Ed.) to form a vapour. You can draw a serious of lines, plotted on a graph where the x-axis shows volume, and the y-axis shows pressure, which correspond to different temperatures and called isotherms, which demonstrate what will happen to a substance as you increase temperature with a given volume (or pressure). The one with most relevance of course is nitrous oxide…(see here).

Pseudo-critical temperature is the critical temperature of a mixture of gases. In anaesthesia it is commonly used to describe the temperature at which a 50:50 mixture of oxygen and nitrous oxide separates (laminates) forming liquid nitrous oxide and gaseous oxygen, which occurs at (depending on the pressure) temperatures in the range -7 to -5.5 degrees Celsius in cylinders, and lower temperatures in a pipeline (due to lower pressures) at around -20 degrees Celsius.

Image via Wikipedia Critical Temperature is the temperature above which, no matter how much pressure you apply, you cannot force a gas to become a liquid. Interestingly enough, though, if you apply sufficiently high pressures, you can form a solid. Essentially, distinct liquid and solid phases of a substance no longer exist.

If you measure the vapour pressure of a substance at the critical temperature, that pressure is called the critical pressure. Alternatively it could be defined as the pressure which is required to liquefy a vapour at its critical temperature.

A substance is a vapour when it is in equilibrium with the substance in another phase, and a gas when there is no liquid or solid present. Therefore, by definition, except at the extremely high pressures mentioned above, any substance above its critical temperature, is a gas. A liquid does not have to boil, nor a solid to sublime (change state directly from solid to vapour/gas-Ed.) to form a vapour. You can draw a serious of lines, plotted on a graph where the x-axis shows volume, and the y-axis shows pressure, which correspond to different temperatures and called isotherms, which demonstrate what will happen to a substance as you increase temperature with a given volume (or pressure). The one with most relevance of course is nitrous oxide…(see here).

Pseudo-critical temperature is the critical temperature of a mixture of gases. In anaesthesia it is commonly used to describe the temperature at which a 50:50 mixture of oxygen and nitrous oxide separates (laminates) forming liquid nitrous oxide and gaseous oxygen, which occurs at (depending on the pressure) temperatures in the range -7 to -5.5 degrees Celsius in cylinders, and lower temperatures in a pipeline (due to lower pressures) at around -20 degrees Celsius.

FINAL FRCA Short answer questions by James Nickells, Maan Hasan, Vino Ramachandra and Neville Robinson (ISBN: 0-7279-1289-5; Publisher: BMJ Books)

Published way back in 1998, this book is looking a bit dated now, and that’s not just in terms of it’s cover, but also it’s typeface (better known as font, nowadays). The layout is in the form of nine exam papers which are the same format as the current paper, and include some old favourites, such as writing notes on statistical tests, describing the anatomy of the trachea, stress ulcers in ICU and anaesthetising in an MRI. From this point of view it gives you the opportunity to set a timer, and sit down and do “a practice paper under exam conditions”.

The model answers are simply laid out with bullet points and subheadings given to show a suggested framework, and the explanations are generally short and sweet. The questions chosen for inclusion were quite cleverly chosen for the principles of management and principles of answering, and answers are still applicable today. However, because the book is from 1998 some of the answers can be out of date and/or dated. For example magnets are no longer recommended for routine use (Anaesthesia 2006) with pacemakers. After a prolonged re-read, however, no massive glaring problems were discovered, and any issues there are with answers are fairly obvious, on the whole, and should only cause a minor irritation to the reader.

Less wordy than some other SAQ books in its answers, this proved a useful revision aid for it’s simle layout and simple answers. There are no “for extra bonus points” points, instead the authors stuck to the KISS principle. (Keep it simple, silly - Ed.)

Would we recommend it? Difficult one. Questions in this book are covered in other books which also cover more topics. I preferred the style and layout of the answers in this to some of the other books, but not everyone will do. Overall, it wouldn’t be top of the list, because other books have slightly more to offer, but it’s a useful adjunct to revision.

FINAL FRCA Short answer questions by James Nickells, Maan Hasan, Vino Ramachandra and Neville Robinson (ISBN: 0-7279-1289-5; Publisher: BMJ Books)

Published way back in 1998, this book is looking a bit dated now, and that’s not just in terms of it’s cover, but also it’s typeface (better known as font, nowadays). The layout is in the form of nine exam papers which are the same format as the current paper, and include some old favourites, such as writing notes on statistical tests, describing the anatomy of the trachea, stress ulcers in ICU and anaesthetising in an MRI. From this point of view it gives you the opportunity to set a timer, and sit down and do “a practice paper under exam conditions”.

The model answers are simply laid out with bullet points and subheadings given to show a suggested framework, and the explanations are generally short and sweet. The questions chosen for inclusion were quite cleverly chosen for the principles of management and principles of answering, and answers are still applicable today. However, because the book is from 1998 some of the answers can be out of date and/or dated. For example magnets are no longer recommended for routine use (Anaesthesia 2006) with pacemakers. After a prolonged re-read, however, no massive glaring problems were discovered, and any issues there are with answers are fairly obvious, on the whole, and should only cause a minor irritation to the reader.

Less wordy than some other SAQ books in its answers, this proved a useful revision aid for it’s simle layout and simple answers. There are no “for extra bonus points” points, instead the authors stuck to the KISS principle. (Keep it simple, silly - Ed.)

Would we recommend it? Difficult one. Questions in this book are covered in other books which also cover more topics. I preferred the style and layout of the answers in this to some of the other books, but not everyone will do. Overall, it wouldn’t be top of the list, because other books have slightly more to offer, but it’s a useful adjunct to revision.

If like us you are a member of the AAGBI then you will recently have received a copy of their latest glossy on Red Cell Transfusion. Sadly they don’t appear to have put it up on their website yer, and we’ve not had time to review it, but we will try to keep an eye on the website and put up a link as soon as we can.

Keep an eye on the site as we get closer to the closing date for entry and we will put up a list of what we consider are likely to be the hot topics from the previous 12 months. Also, watch James Shorthouse’s blog over at Passing the Final, as he keeps a good update going, which often includes the hot topics.