Grammar help

[Karen2005]

I am checking a document that has been proofread and have come across a couple of queries from the proofreader.

Currently a sentence reads:

"General anaesthesia is used in nearly all cases with full muscle relaxation".

However, the proofreader asks whether commas should be inserted as follows which would change the meaning of the sentence:

"General anaesthesia is used, in nearly all cases, with full muscle relaxation"

Am I correct in thinking that the first sentence means that general anaesthesia is used in nearly all cases and the second sentence means that full muscle relaxation brought about in nearly all cases? I need to make sure my thinking is correct before refering the query back to the author.

Secondly, a sentence currently reads:

"Large pleural effusion can also opacify a hemithorax, but is associated with mass affect with mediastinal shift away from affected side".

Should mass affect be changed to mass effect?

Thank you!

[Lil O'lady]

The first sentence could be read to suggest that local anaesthetic is used in some cases that present themselves with full muscle relaxation.

The second sentence is clearer, letting the reader know that different anaesthesia is occasionally used, but that where a general is used full muscle relaxation occurs.

Effect is used as a noun, affect as a verb: http://www.wisegeek.com/what-is-the-difference -between-affect-and-effect.htm
I am diffident about responding to this part as it may be that medical phraseology uses the phrase 'mass affect' to mean a particular event. eg if you substitute mass affect with 'haemorrage' - used as both a noun and a verb in medicine.

[Milvus]

Affect and effect can be used as verbs.
To effect a change is to cause or make a change
To affect a change is to alter a change
but I wouldn't make a guess on "mass affect" without knowing the subject. "Mass affect" could be a technical term in its own right.

[Karen2005]

Thank you both for your answers.

Yes, I think I need to refer the affect/effect question to one of my medical colleagues. You are quite right it could be a technical term.

[sqad617]

Sentence 1 is correct.
Sentence 2 is correct.

Both grammatically and medically.

[slaney]

The radiological term is "mass effect".

[Peter Pedant]

Oh, yes I see
the first one is ambiguous
and you need to decide what you mean
and alter the word order

general anaesthesia in nearly all cases

or muscle relaxation in nearly all cases

and no 2
mass effect

mass affect here is wrong