CSS Table help

I am making responsive tables in wordpress, using code i found on css tricks.

/*
		Label the data
		*/
		td:nth-of-type(1):before { content: "Valve Size"; }
		td:nth-of-type(2):before { content: "Catalog Number"; }
		td:nth-of-type(3):before { content: "Tissue Annulus Diameter (mm)"; }
		td:nth-of-type(4):before { content: "Internal Diameter (mm)"; }
		td:nth-of-type(5):before { content: "Flare Diameter (mm)"; }
		td:nth-of-type(6):before { content: "Sewing RingDiameter<sup>1</sup>(mm)"; }
		td:nth-of-type(7):before { content: "Overall Height (mm)"; }
		td:nth-of-type(8):before { content: "Orifice height (mm)"; }
		td:nth-of-type(9):before { content: "Internal Orifice Area (cm<sup>2</sup>)"; }

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What i need is to beable to print cm2 as a header,   at the minute it is printing the html also.  OBviously it works at full size, but once it goes responsive, then i loose the ability to use cm2

How can i do this please ?