I have used these in an Emergency Dept setting with mixed success.
If your patient moves in any way, the machine will result in an error. It requires your patient to be flat (with legs elevated) and completely still. This might be more feasible on an intubated patient, but on an awake/alert patient, it can get complicated. The other issues I have seen are the time requirements to obtain your readings. While the actual test might be 5 minutes, you are often in there for 15+ troubleshooting the machine.
I've seen this machine help us make an educated clinical decision and thus avoided invasive interventions/monitoring. Often times this can be utilized as an 'I told you so' tool when working with physicians. If you choose to opt for the fluid challenge option (500cc) and you KNOW your patient just needs a bolus, this is an intervention to suggest to get your patient that bolus and prove they are responsive to it
I think there can be much improvement on this device. Do yourself a favor and use regular pillows instead of the pillow provided (unless you keep it inflated all the time.)