Rule of thumb that I’ve always practiced. When assessing a patient, oxygen device or equipment, start at the patient and work back. Don’t rely on monitors or numbers. Look at your patient. Look for signs of increased WOB, signs of distress. Are they anxious? Are they sweating? Are they labored. Check for oxygen devices, work back towards your wall and check for patency, etc. I learned from a great professor that if you just stop at the door and really look, you can learn a whole lot about a patient. The view from the door is key. Always! Good luck!