MSTN and pneumonia: In strictly bedridden healthy adults, muscle strength decreases by 1% per day, while in the ICU, patients with severe pneumonia on mechanical ventilation and sedation and analgesia are generally in a state of complete or near-complete braking, with poorer status of various physiological functions, which severely affects the balance of myostatin synthesis and catabolism and makes them more susceptible to myocardial injury [22].