This is a single-center, prospective, physiological study.

The study will enroll the traumatic lung injury patient who has at least 2 rib fractures requiring mechanical ventilation being on partially assisted breathing mode and on activity as tolerated (AAT) order with or without C-collar. Once being confirmed to meet the inclusion criteria, the research team will apply the EIT on the patient and start recording as well as perform lung ultrasound in the specific areas of interest in the selected time points of the study. The MV ventilator setting and some vital sign data will be also collected at selected time points of study. The EIT will continuously record from 5 minutes when patient is on supine position, then the investigators will turn patient using positioning wedge pillow to the sides with 30-minute EIT recording each side, lastly, the investigators will turn patient back to supine and continuously record for 30 minutes. The study will use the same protocol to perform in 3 different settings of mechanical ventilation (weaning process) i.) during partially assisted breathing, ii.) during high setting of spontaneous breathing and iii.) during low setting of spontaneous breathing.

This study will be conducted while the patient is partially assisted on a breathing machine and have been clinically indicated to mobilize as tolerated while in the weaning process in the ICU.

The investigators will use EIT to visualize where air goes in the patient's lungs and lung ultrasonography to visualize lung inflation in specific areas. EIT is a measurement often used in the ICU since it allows easy visualization and is a non-invasive technique. The sensors measure electrical current changes during inspiration and expiration and will not cause any pain or radiation concerns. The EIT belt (3-cm diameter) will be placed around the chest without causing adverse event/discomfort/pain to the injured thorax area and recording will occur for 5 minutes during the first supine position, then 30 minutes for each side of left and right lateral position using the 30 Degree wedge pillow to support. The pillow is routinely applied to every ICU patient when eligible to be positioned on their side. As routine practice, patients are turned on each side every 2 hours to prevent pressure sores. Lastly, the investigators will do a final 30-minute recording when the patient is turned back onto their back. The duration of study will be approximately 95 minutes per session, which includes placing the patient in the four positions (on the back, the left side, the right side and returning to the back). The investigators will perform the same protocol at three different times when they are at different stages of weaning off the breathing machine: i) during partially assisted breathing, ii.) during a high setting of spontaneous breathing and iii.) during low setting of spontaneous breathing). These 3 breathing machine's settings indicate the patient is on the pathway of weaning off the breathing machine. The total study hours will be 4.75 hours (3 sessions) and each breathing machine's setting will be adjusted by clinical team over time. The investigators will proceed with the measurements only with agreement from the clinical team. The investigators will analyze the data collected offline with a dedicated software afterwards.

This study may require arterial blood gas analysis at baseline and after the procedure, only if there is an arterial line in place. The information from the sample provides the investigator the status of participant's breathing and breathing machine settings. It allows for any appropriate adjustments to the breathing machine. After these study procedures are completed, data will also be collected from the participant's chart and combined with relevant information from the breathing machine settings and vital functions at each stage of position changes. Confidentiality will be maintained throughout the entire study.

Inclusion Criteria:

1. Age of ≥ 18 years
2. Traumatic lung injury with at least 2 rib fractures with or without chest tube and requiring mechanical ventilation
3. On any mode of ventilation including partially assisted breathing mode
4. With an "activity as tolerated (AAT) order" with or without C-collar

Exclusion Criteria:

1. Refusal of consent
2. Palliative or end of life condition
3. Contraindication to EIT placement: pacemaker/defibrillator implantation, burns at the area of EIT placement
4. Vasopressor: greater than 0.4 mcg/kg/min of norepinephrine infusion

The patients will be selected from intensive care units.

Electrical impedance tomography images and ultrasound images may be shared with no participant identification.