4 “Whereas previously the answer might have been to increase the tidal volume, current philosophy has shifted to a stronger focus on protection of the lung with the use of smaller tidal volumes.”Ī seminal study5 of 861 adult patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) set today’s tidal volume standard: 6 mL/kg. “Is it better to use a smaller tidal volume and let the partial pressure of arterial carbon dioxide (PaCO 2) increase despite the associated risks (eg increased intracranial hypertension from respiratory acidosis) or use larger tidal volumes to normalize the PaCO 2 but increase the risk of lung injury?” ask the authors of a 2013 review of VILI in the New England Journal of Medicine. Key components of lung protection rely on low tidal volumes and adequate positive end expiratory pressure (PEEP.) That strategy has been embraced relatively recently. ![]() By using pressure limitation, the respiratory system mechanics are going to dictate the allowable tidal volume: the smaller the lung inflatable volume, the smaller the Vt will be for a given pressure,” he wrote. That’s why in peds we mainly use pressure controlled ventilation. Also, volume controlled ventilation-often used in adults-is not really suitable for children with uncuffed endotracheal tubes because of leakage. So I think that both for children and adults an individualized titration of mechanical ventilation is indicated. “The optimal tidal volume is unclear as well as the level of PEEP that has to be set. The lung protective strategies currently available in pediatrics are similar to what is used in adult care, which Kneyber said is acceptable-to a point. Next to this, there are huge differences in immune response to injurious stimuli in young children the immune response is mainly anti-inflammatory rather than pro-inflammatory.” “For instance, lung volumes differ, the elastic properties of the chest wall are different (young children have much more elastic chest wall) and the structure itself of the lung is different during the first two years of life. “There are huge differences in respiratory physiology between especially young children and adults,” Martin Kneyber, MD, PhD, a pediatrician at the University Medical Center of Groningen in the Netherlands told RT in an email. They are especially tough for pediatricians to contend with, given that most lung protective strategies have been tested in adults, rather than children. Positive pressure ventilation was eventually embraced, but the risks suspected by Fothergill have proven real. ![]() “The lungs of one man may bear, without injury, as great a force as those of another man can exert which by the bellows cannot always be determin’d.” 3 2 “It has been suggested to me by some that a pair of bellows might possibly be applied with more advantage in these cases, than the blast of a man’s mouth, but if any person can be got to try the charitable experiment by blowing, it would seem preferable to the other,” wrote English physician John Fothergill in 1744. Risks of mechanical ventilation have been recognized as early as the 18th century. An article in Anaesthesiology Intensive Therapy 1 explains the difference: “VALI refers to exacerbation of pre-existing lung injury due to factors related to mechanical ventilation, whereas VILI is used for injury to previously unaffected lungs or intentional experimental lung injury in animals.” ![]() These injuries are called ventilator-associated (VALI) or ventilator-induced lung injuries (VILI). Even noninvasive ventilation carries risks, most notably pressure injuries from face or nasal masks. Side effects of mechanical ventilation include over-distension of the lungs (volutrauma or barotrauma) biological cascade resulting in inflammation (biotrauma) damage caused by continuously forcing open collapsed lung units (atelectrauma) infection and pulmonary edema. Ventilators save lives, but they can also do real damage. ![]() A look at some of the most effective clinical efforts to prevent ventilator-associated lung injuries for pediatrics.
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