Efficacy and Safety of a Lung Recruitment Protocol in Children With Acute Lung Injury

I. Introduction A. Background Lung units which participate in gas exchange are known as 'recruited' lung. Patients with lung injury suffer from a proportion of units which do not participate in gas exchange (i.e. the derecruited state), at times resulting in impaired gas exchange. Derecruitment of alveoli may also cause intrapulmonary shunting and worsen lung injury through atelectotrauma7. Outcomes in acute respiratory distress syndrome have improved significantly Is this really true? since clinicians have begun to employ lung protective strategies, including low-tidal volume ventilation and permissive hypercapnea8, 9. However, low-tidal volume ventilation has been recognized to decrease recruited lung volume, a phenomenon which persists despite the aggressive positive end-expiratory pressure (PEEP) strategy employed in ARDSNet studies4. Atelectasis associated with low-tidal volume ventilation is relieved through the use of so-called sign breaths, or recruitment breaths10. Further, the proportion of lung remaining in the derecruited state may contribute to the morbidity and mortality associated with acute respiratory distress syndrome (ARDS)11. In adults, several strategies have been utilized to recruit the lung: sustained inflation (SI) and the maximal recruitment strategy. The so-called open lung approach (OLA) includes an SI followed by the setting of PEEP to the measured lower inflection point of the PV curve. An alternative approach to setting PEEP is a decremental PEEP titration, which includes the sequential lowering of PEEP until a predetermined decrement in PaO2 or SaO2 occurs. Studies which have not included a strategy for maintaining lung recruitment following a recruitment maneuver have all been studied.

The impact of lung recruitment in the long-term course of ARDS is not yet clear. It is clear that lung recruitment is most effective earlier in the course of ALI/ARDS. Grasso et al demonstrated that patients who received a recruitment maneuver on day 1±0.3 of ARDS could be recruited, versus patients recruited on day 7±1. Similarly, Gattinoni et al11 and Crotti et al5 found limited recruitment in patients who were well along in the course of ARDS. Borges et al,6 Tugrul et al,12 and Girgis et al all recruited patients early in the course of ARDS, and each found marked lung recruitment, on average, in all the patients studied. Each of these studied demonstrated an ability to improve oxygen saturations and (sometimes studied) end-expiratory lung volume. While no study has examined the effect of this change on morbidity or mortality, in children hypoxemia is known to be a common cause of morbidity. Importantly in children, treatment of hypoxia often drives escalating ventilator settings, the use of high frequency oscillatory ventilation (HFOV) or the use of extra-corporeal membrane oxygenation (ECMO). Early recruitment in children with ALI/ARDS may prevent the need for escalation of care towards these more invasive, and risk-imposing therapies.

Currently, there are no clinical practice guidelines or standard of care regarding lung recruitment strategies for children with lung injury. To date, no studies have been performed in children documenting the efficacy or safety of any of the strategies utilized in intensive care. The primary aim of this study is to demonstrate the efficacy and safety of sustained inflation and maximal recruitment maneuvers in children with lung injury.

B. Lung Recruitment Maneuvers

1. Sustained Inflations (SI) Sustained inflations (SI) are commonly utilized in the intensive care unit as a recruitment maneuver. In SI, the patient is given a prolonged positive pressure breath (usually between 30 and 45 cm H2O) lasting between 15 and 40 seconds. Clinically, this maneuver is applied following a derecruitment, such as suctioning, or when the patient exhibits hypoxemia. This strategy is currently employed in the Children's Hospital Boston Medical-Surgical Intensive Care Unit in some patients with lung injury, though there is no published evidence of its safety or efficacy in children. Could we put the 3 SI studies in premature infants that use 20-40 cmH20 followed by CPAP? 1 was a rabbit study. The studies described below regard sustained inflation recruitment maneuvers.