You can send multiple sensor measurements in one request by appending additional measurements to the request using '...&fieldx=...'. All your sensors need to be connected to one device. If the sensors are attached to sperate devices, you can have them poist to differnet channels and then use a MATLAB analysis script to combine the data into a new combined data channel if required. For example:
https://api.thingspeak.com/update.json&api_key=xxxxxxxxxxxxxxxx&field1=1&field2=22&field3=333
