Identifying the Optimal IMT Dose in ICU

200,000 adults are admitted to intensive care in the UK each year. Many of these patients need help with their breathing and are put on a machine called a ventilator. Research shows that many patients using a ventilator quickly develop weakness in their main breathing muscle, called the diaphragm. This weakness can cause a longer time on the ventilator, a longer hospital stay, and higher chances of health problems or death. Inspiratory muscle training is a breathing exercise where the patient breathes against resistance through a small device (like breathing through a straw). It aims to improve the strength of the diaphragm and reduce how long patients are on the ventilator. Why is this research needed? Research shows that current breathing exercise programmes do not help patients come off the ventilator or go home quicker. This may be because these breathing exercises strengthen the wrong muscles (those in the chest and neck, that are not efficient). These exercises can also be distressing for patients. What will be done in this research? This research aims to develop a breathing exercise programme that focusses on strengthening the diaphragm. We will also make sure patients do not find the breathing exercise too distressing. This research will measure how the breathing muscles respond to four different levels of breathing exercise and ask patients to feedback on each level. 1. At each breathing exercise level, the effort of the breathing muscles will be measured using a small tube inserted into the nostril and small sticky patches on the chest and neck. We aim to find the level where the diaphragm is being pushed to work hard but other muscles in the chest and neck are not. 2. After each breathing exercise level patients will be asked how they found it - for example, easy, pleasant, scary. This procedure will be repeated 1-3 times over seven days with at least 24 hours between each measurement