Ultrasound to assess diaphragmatic function in the critically ill—a critical perspective

Abstract

Ultrasound of the diaphragm in critically ill patients has become a diagnostic technique of emerging interest among clinicians and scientists. The advantages include that it is widely available, noninvasive and examination can be performed after relatively short training and at low costs. It is used to estimate muscle mass by measurement of muscle thickness and diagnose weakness by the assessment of diaphragm movement during unassisted breathing. Thickening of the muscle during inspiration has been used to quantify force generation. The enthusiasm that surrounds this topic is shared by many clinicians and we agree that ultrasound is a valuable tool to screen for diaphragm dysfunction in intensive care unit (ICU) patients. However, in our opinion much more studies are required to validate ultrasound as a tool to quantify breathing effort. More sophisticated ultrasound techniques, such as speckle tracking imaging are promising techniques to evaluate respiratory muscle function in patients, including the critically ill.

Diaphragm function and weaning from mechanical ventilation: an ultrasound and phrenic nerve stimulation clinical study

“…The use of diaphragm ultrasound is growing in the ICU [ 28 , 29 ]. It has many advantages over phrenic nerve stimulation, which requires costly equipment and extensive technical expertise.…”

Assessing breathing effort in mechanical ventilation: physiology and clinical implications

“…Ultrasound has gained in popularity as a diagnostic tool in clinical management and research in the ICU (14). The role of ultrasound to evaluate respiratory muscle function and effort have been discussed in recent articles (65,73). Components of the respiratory muscle pump, including the diaphragm, abdominal wall muscles and accessory muscles, are positioned relatively superficial and are readily accessible for ultrasound.…”

“…Advantages of ultrasound include the non-invasive nature, low-costs, steep learning curve and straightforward calculations which allows bedside evaluation of breathing effort (73). However, several technical and methodological limitations apply to ultrasound assessment of breathing effort.…”

“…However, several technical and methodological limitations apply to ultrasound assessment of breathing effort. Because the diaphragm is very thin, small errors in measurement can result in large overestimation and underestimation of thickness and thickening fraction (73). Additionally, the left hemidiaphragm is harder to visualize than the right side (78).…”

Perioperative care with an ultrasound device is as Michael Jordan with Scotty Pippen: at its best!

“…Also, the use of POCUS in evaluating diaphragm functionality is of interest. Research has shown that the use of POCUS to measure diaphragm thickness, motion and thickening fraction can quantify diaphragm atrophy and predict weaning success (7,8).…”