Press the brown/sauté button, set temperature to high, and then press start. Allow preheating. Add olive oil, onion, garlic, carrots, and the celery. Sauté for 2 minutes. Add the thyme and the bay leaf.  Place the chicken breasts on top of the vegetables, then pour in one cup of the chicken broth. Place the lid on the pot and lock. Press the soup function(or manually set to pressure cook on high) and adjust the cooking time to 10 minutes. At the end of cooking use the natural pressure release method and allow it to naturally release for 10 minutes. 

Remove the chicken, thyme and the bay leaf.  Add the remaining broth to the pot, select the brown/sauté function to high temperature and bring to a boil. Add the orzo and cook to al dente according to the directions on the box. While the orzo is cooking, shred the chicken. When the desired doneness of the orzo is reached stir in the shredded chicken. Squeeze in the lemon juice and salt and pepper to taste. Serve hot with crackers or bread and enjoy!