May 6 2020
FDA grants EUA to muscle stimulator to reduce mechanical ventilator usage
Great news? Not so fast. FDA dolls out EUAs (emergency use authorizations) like free candy. The newest perl is approval of the VentFree device, which was tried on … 10 (ten) patients!
The device delivers electric shock to abdominal muscles synchronized with exhalation. I have a very simple explanation of how it works: if a reader of this blog was ever kicked into his belly, one must remember deeply exhaling and unable to take a breath for sometime, which may lead to a syncope (“passing out”).
Indeed, exhalation is the most important part of breathing cycle. We cannot inhale properly unless able to exhale - get air out of our lungs. There will be no place to accommodate fresh air, even with strong muscles. The volume of air we exhale with each breathing cycle at rest is approximately 500 cc (0.5 liter). It is called Tidal volume. The total lung volume in a healthy person is 5 to 6 liters, e.g. more than 90% of air remains in our lungs. The tidal volume increases to 1.5 liter with exercise.
The normal breath rate is 12-14 per minute. The healthy person can sustain breath rate increase to 24 per minute or even more for up to 24-hours.
Why 24-hours? The muscles of breathing: intercostal, abdominal, diaphragm, and upper chest muscles literally get tired, just as any other muscles in our body. The muscle fatigue develops due to exhaustion of energy (just as happens in a battery) and accumulation of by-products of muscle energy cycle, most notably lactic acid.
Hence, there is only so much Work of Breathing (WOB) we can do. What happens next? We either die or non-invasive - BiPAP (also referred to as BPAP - Bilevel Positive Airway Pressure) or invasive assisted ventilation (“ventilator”) must be employed. These allow muscles to rest, get “new charge” and expel toxic metabolites.
So, why is electrical stimulation a good idea? It is not. Have you seen tired horse being whipped? How long that horse would last without rest and “refuel”? Not very long…
In the only published study of this device (in the open source online journal Critical Care), with 10 patients in treatment group and 10 patients in control group, 8 and 6 patients respectively survived ICU admission. There was no statistical difference between groups by any of the analyzed parameters.
Dr. Why’s bottom line:
It makes no sense to whip exhausted horse;
The low level of evidence required to get FDA “seal of approval” is appalling;
I would like to refer both the inventors and FDA geniuses to the 1998 article published in the Veterinary Clinics of North America Equine Practice titled “The exhausted horse syndrome ” which spells out circumstances, biochemical causes, and measures to be taken to treat the animal.
Here is the abstract:
Exhaustion occurs in most equestrian sports, but it is more frequent in events that require sustained endurance work such as endurance racing, three-day eventing, trial riding, and hunting. Exhaustion is also more likely when an unfit, unacclimatized, or unsound horse is exercised. Mechanisms that contribute to exhaustion include heat retention, fluid and electrolyte loss, acid-base imbalance, and intramuscular glycogen depletion. Clinical signs include elevated temperature, pulse, and respiratory rate; depression; anorexia; unwillingness to continue to exercise; dehydration; weakness; stiffness; hypovolemic shock; exertional myopathy; synchronous diaphragmatic flutter; atrial fibrillation; diarrhea; colic; and laminitis. Treatment includes stopping exercise; rapid cooling; rapid large volume intravenous or oral fluid administration; and nonsteroidal anti-inflammatory drug administration.
Got the point?