Select Sauté. Add the oil, onion, carrots, and celery. Cook, stirring, until the onion begins to soften. Add the garlic and stir briefly.
Cancel Sauté. Pour in a little broth and scrape the base clean. Add the remaining broth, chicken, bay leaf, thyme, and pepper. Check the filled level against the exact cooker manual before sealing.
Select Pressure Cook, High, for 10 minutes. Allow pressure to release naturally until the float valve drops. Open the lid only when fully depressurized.
Check the chicken with a thermometer: it must reach 165°F. If needed, continue cooking until it does. Transfer to a board and shred; discard the bay leaf.
Select Sauté with the lid off. Add the egg noodles and simmer, stirring, for the package cooking time or until tender. Return the shredded chicken and heat through. Add lemon juice and salt to taste.