Subjects identified as being administered low dose opioids during an elective lower extremity orthopedic surgery per standard of care will undergo an ultrasound shear wave elastography examination while performing different breathing techniques.

Subjects identified as being administered mid dose opioids during an elective lower extremity orthopedic surgery per standard of care will undergo an ultrasound shear wave elastography examination while performing different breathing techniques.

Subjects identified as being administered higher dose opioids during an elective lower extremity orthopedic surgery per standard of care will undergo an ultrasound shear wave elastography examination while performing different breathing techniques.

Three different fentanyl doses (used for sedation) will be evaluated on their effects on shear wave elastography (SWE) and breathing

Measured by the ultrasound elastography of the diaphragm muscle reported in KPa