Can I make this code shorter?

Can I make this code shorter?

Yes, you can. Look at using arrays.

const int pressureIn1 = A0;  // Analog input pin that the potentiometer is attached to
const int pressureOut1 = 5; // Analog output pin that the LED is attached to
const int pressureIn2 = A1;  // Analog input pin that the potentiometer is attached to
const int pressureOut2 = 6; // Analog output pin that the LED is attached to

becomes

const int pressureIn[] = { A0, A1 };  // Analog input pins that the potentiometers are attached to
const int pressureOut[] = { 5, 6 }; // Analog output pins that the LEDs are attached to

Similarly, everywhere you read from the pins one at a time, use a for loop to read them together.

int outpoutValue1 = 0;        // value output to the PWM (analog out)
int outputValue2 = 0;        // value output to the PWM (analog out)

Consistency is good...

You have a lot of global variables that should be local to loop.

  {
    for(int i = 0; i < medianSize1; i++)   
    {                                       
      rangeValue1[i] = analogRead(pressureIn1);
      rangeValue2[i] = analogRead(pressureIn2);       
      delay(1);  //wait between analog samples
    } 
    isort(rangeValue1, medianSize1);
    isort(rangeValue2, medianSize2);
  }

The outer curly braces are not needed. Get rid of them.