As a result of randomization, the IMT group consisted of 16 participants with a mean age of 70 ± 9.57 years. IMT was administered to the participants twice a day following routine physiotherapy, which included breathing exercises and mobilization.

As a result of randomization, the NMES group consisted of 16 participants with a mean age of 65.31 ± 8.38 years. Following routine intensive care physiotherapy, which included breathing exercises and mobilization, NMES was applied to the diaphragm muscle for 40 minutes.

Routine ICU physiotherapy includes: conventional chest physiotherapy, consisting of diaphragmatic breathing, thoracic expansion exercises, postural drainage, cough training, and in-bed ROM exercises and mobilization. In addition to routine ICU physiotherapy, patients received NMES on the diaphragm with surface electrodes. Electrodes were placed at four channels with two electrodes on both sides of the xiphoid at the level of the intercostal space of the 7th and 8th ribs, superiorly and inferiorly. In addition, two electrodes with two channels were placed superiorly and inferiorly at the midaxillary level of the intercostal space of the 7th and 8th ribs. A total of 4 channels and 8 electrodes were used with modified burst series biphasic current 30 Hz (Aussie current).

Inspiratory muscle strength (Pimax) was assessed by a desktop spirometer with Pimax module (Pony Fx, COSMED, Rome, Italy). A catheter mount piece was placed in front of the pressure measurement part of spirometer to perform the measurement in intubated participants. Participants were encouraged throughout the measurements to achieve maximum strength and coordination. The measurements were repeated three times, and the average of these values was recorded. To prevent respiratory muscle fatigue, at least a one-minute break was provided between trials. Results were reported in cmH2O units.

Physical function levels of patients were evaluated by Physical Function Intensive Care Unit Test-scored (PFIT-s). Physical Function Intensive Care Unit Test-scored has 4 test components; shoulder flexion strength, knee extension strength, sit to stand assistance, step cadence. Before the test, the participant was expected to correctly answer 2 of 5 questions to assessing the cooperation. Participants' vital signs were noted before and after the test. Participants are scored on a total scale ranging from 0 to 10. A score of 0 signifies total dependence and poor muscle strength, whereas a score of 10 represents functional independence and optimal muscle strength.

Respitatory parameters were assessed by mechanic ventilator (The Engstrom Carestation, GE Health Care 2016). The test procedure; device was switched to CPAP mode, Psupport was set to 10 cmH2O and PEEP was set to 5 cmH2O to overcome the physiological resistance of the ventilator circuit. The patient was instructed to take deep breaths for one minute. As the measurements required patient motivation and coordination, the tests were conducted by providing appropriate verbal commands. Inspiratory tidal volume (TVi) and expiratory tidal volume (TVe) were recorded in milliliters (ml).