Mechanical ventilation, diaphragm weakness and weaning: A rehabilitation perspective

Abstract

Most patients are easily liberated from mechanical ventilation (MV) following resolution of respiratory failure and a successful trial of spontaneous breathing, but about 25% of patients experience difficult weaning. MV use leads to cellular changes and weakness, which has been linked to weaning difficulties and has been labeled ventilator induced diaphragm dysfunction (VIDD). Aggravating factors in human studies with prolonged weaning include malnutrition, chronic electrolyte abnormalities, hyperglycemia, excessive resistive and elastic loads, corticosteroids, muscle relaxant exposure, sepsis and compromised cardiac function. Numerous animal studies have investigated the effects of MV on diaphragm function. Virtually all of these studies have concluded that MV use rapidly leads to VIDD and have identified cellular and molecular mechanisms of VIDD. Molecular and functional studies on the effects of MV on the human diaphragm have largely confirmed the animal results and identified potential treatment strategies. Only recently have potential VIDD treatments been tested in humans, including pharmacologic interventions and diaphragm “training”. A limited number of human studies have found that specific diaphragm training can increase respiratory muscle strength in FTW patients and facilitate weaning, but larger, multicenter trials are needed.

Risk Factors for Pediatric Extubation Failure: The Importance of Respiratory Muscle Strength*

“…Ventilator induced diaphragm dysfunction is present in up to 50% of mechanically ventilated adults, and leads to impaired weaning and extubation failure (23–25, 27, 28, 33–35). While many adult studies use diaphragm ultrasound (23, 27, 28, 36, 37), we used a direct measure of strength (aPiMax), and found that that respiratory muscle weakness is nearly as common in children (35%).…”

Age related differences in diaphragm muscle fiber response to mid/long term controlled mechanical ventilation

“…In clinical practice, once the respiratory failure and the other sources of instability are solved, the weaning process from the mechanical ventilation can be started. Weaning takes about 40% of the time spent on the ventilator and it is further complicated and delayed by additional problems in 20 to 30% of mechanically ventilated patients (BouAkl et al, 2012;Daniel Martin et al, 2013;McConville and Kress, 2012). Complicated weaning increases the ICU stay by 50% with elderly patients being more severely affected than the young (Crul et al, 2013;Esteban et al, 2002;Zarzhevsky et al, 2001aZarzhevsky et al, , 2001b.…”

Year in review 2013: Critical Care- respirology

“…Several authors who have studied diaphragm strength invasively have reported that patients with greater diaphragm strength are more likely to successfully wean than patients with weaker diaphragms [ 75 , 76 ]. Animal and limited human studies have found that anti-oxidants and physical activity can block or attenuate ventilator-induced diaphragm dysfunction by short-term mechanical ventilation use [ 77 ], but more work investigating cellular and functional changes in the human diaphragm following mechanical ventilation is needed.…”