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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Fool contributor Matt Koppenheffer does not have a financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.