Table 4.

Key considerations for continuing assessment of lung function.

	LUS	VRI
Approach	Detects the sound wave interaction with reflecting interfaces such as the lung tissue via a specialized probe	Measures breathing sound distribution in the airway and converts it to vibration energy with an electronic stethoscope/microphone
Imaging	Maps from the sound propagation that is reflected from the lung tissue or rib cage	Maps the ventilation distribution into a grayscale figure for lung function assessment
Indications	Assesses lung health regionally and globally Flexible, bedside, and home-based monitoring are possible Frequent, semi-continuous monitoring due to a nonhazardous approach Comparable assessment outcome of lung function compared to CT and chest X-rays	Assesses lung health regionally and globally Flexible, bedside, and home-based monitoring are possible. Frequent, semi-continuous monitoring due to a nonhazardous approach Maps the vibration energy with one planar posterior measurement Good correlation of lung function assessment compared to LUS and chest X-rays
Disadvantages	Requires specialized training to operate the equipment Requires trained personnel to interpret the assessment outcome Assessment outcome may be affected by the patient’s body size [44]	Requires a controlled environment and additional equipment, such as a vacuum pump Expensive system at USD 50,000 [50] as compared to a typical LUS system at about USD 33,000 [14]