Help sim900 gsm shield+arduino uno:How send a integer afetr convert it in sting

Hi everybody! I'm working about a prjoect with arduino uno and sim9àà gsm shield. So i have to get pressure measurement and send it in my phone with sms alert! when a pressure thershold is over. So i'm working in windows, and i want to send the pressure value. But i've seen that i 've to convert it before in a string. i tried with "itoa function" but this no work.

So please could you help me to send integer pressure values in my phone with sms?