Diaphragm dysfunction (loss of diaphragm strength) is common in the intensive care unit (ICU) patients using ventilators. The diaphragm is the main muscle of respiration and its dysfunction can prolong mechanical ventilation and increase mortality risk. The ventilator settings determine how much air and pressure the patient gets every breath and how much air is left on the lungs after they breathe out. The amount of air left on the lungs influence diaphragm strength measurements which can affect clinical decisions, such as weaning patients off ventilators. This research aims to explore the relationship between the amount of air left in the lungs and diaphragm strength to create a method of correcting measurements of diaphragm strength according to how much air the patients have in the lungs after they breath out. The investigators will test healthy individuals to understand this relationship, then verify if it holds true for ventilated patients by comparing results from both groups.