This is most definelty a fixed expression. Whether the most appropriate for your text is impossible say, since you've given us no context at all. Could you at any rate tell us what the text is and give us the entire sentence?

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Note added at 11 mins (2008-03-01 16:41:34 GMT)
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"Watching him, it was difficult to escape the impression of a man grappling with fate "
( From: http://tinyurl.com/yu9kya )

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Note added at 13 mins (2008-03-01 16:43:00 GMT)
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"One cannot
escape the impression that in practice "normalization"
signifies the defense of the "status quo" in socialism
or the restoration: of it. One cannot escape the
impression that "normalization" in Czechoslovakia
signifies in fact the desire to block the attempt
to develop a new course (which opened up a great
future for socialism in its present phase), and to
restore a static, non-dialectical situation in socialism."
( From: http://tinyurl.com/2el7z9 )

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Note added at 14 mins (2008-03-01 16:44:21 GMT)
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"Yet, at the same time, a great laxity is observable in enforcing the penalties denounced by the law upon proved wantonness of life; and it is impossible to escape the impression that there existed a general consensus, from which even the clergy only slowly came to express clear dissent, that some allowance should be made to laymen in the matter of the sins they were “inclined to.” "
( From: http://tinyurl.com/yvgnww )

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Note added at 15 mins (2008-03-01 16:45:54 GMT)
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http://tinyurl.com/28pxco (Over 26,200 more examples in context)

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Note added at 40 mins (2008-03-01 17:10:50 GMT)
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Thank you for suppyling the context. Obviously, in a text such as that, the short form of 'it's' that I gave in my answer would need to be used in its full form, 'it is'.