Lung Recruitment in Patients with the Acute Respiratory Distress Syndrome

Abstract

In ARDS, the percentage of potentially recruitable lung is extremely variable and is strongly associated with the response to PEEP.

Visual anatomical lung CT scan assessment of lung recruitability

“…Fifty sets of two complete lung CT scans of ALI/ARDS patients were analyzed, randomly taken from a database of a multicenter study investigating lung recruitment [11] and from a database of unpublished data investigating the effect of PEEP (www.clinicaltrial.gov number INTC0068 2942). All patients met the standard criteria for ALI/ ARDS [13].…”

“…The lung recruitability was computed as the difference in the percentage of consolidated/collapsed tissue passing from an airway pressure of 5 to 45 cmH 2 O, obtained as the mean of values assigned by two expert radiologists [11]. The lung CT images were visualized by using a freely available piece of software (Efilm workstation, Canada).…”

“…Thus at the present time, quantitative lung CT scan analysis remains the reference method for computing PEEP-induced lung recruitment [10,11]. However, this analysis requires dedicated software and a manual delineation of the perimeter of the lungs in each CT image [10].…”

Forced oscillation technique: an alternative tool to define the optimal PEEP?

“…There may be several reasons to explain the lack of beneficial or even harmful effects of using inappropriate PEEP levels: (1) acute lung injury (ALI)/ARDS patients show great variability of alveolar recruitment in response to PEEP [12]; (2) A fixed combination of PEEP/FiO 2 ratio may have induced alveolar over-distension in some patients [9]; and (3) The use of P plat -guided protective ventilation may not be an appropriate approach because of alterations of transpulmonary pressure due to chest wall impairment [10]. On the other hand, the use of low PEEP levels combined with low tidal volume ventilation has been demonstrated to cause lung injury by repeated alveolar collapse and re-opening [4].…”

“…The application of adequate levels of PEEP in the management of ARDS patients remains a critical issue for further investigation [11]. A large portion of potentially recruitable lung units seems to be an independent risk factor for mortality in ARDS [12], thus the benefit of reducing tidal recruitment by increasing PEEP levels may prevail over the effect of increasing alveolar over-distension in this subgroup of patients [13]. A reliable tool at bedside to set desirable PEEP and VT is critical [11].…”