Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of resuscitation-device maker ZOLL Medical (Nasdaq: ZOLL) were alive and well today, gaining as much as 19% in intraday trading on heavier-than-average volume.

So what: The obvious driver for today's gains was ZOLL's fiscal-second-quarter results. Compared to last year's second quarter, ZOLL's revenue rose 14% to $123 million, while earnings per share jumped 59% to $0.27. Wall Street analysts were looking for $0.20 in per-share profit on $121 million in sales.

Now what: ZOLL's LifeVest product was a big winner during the quarter, with year-over-year sales jumping 60% to $27 million. While this is good from a top-line perspective, it's even better for profitability, as the LifeVest is a higher-margin product and helped boost the company's gross margin from 55% to 58%. ZOLL's CEO expects further strong growth from LifeVest and further gains in profitability as a result. Of course, investors who want a piece of this growth are going to have to pay up for it -- ZOLL's stock currently trades at 34 times expected fiscal 2012 earnings.

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