A rationale for lung recruitment in acute respiratory distress syndrome

Increased permeability-oedema and atelectasis in pulmonary dysfunction after trauma and surgery: a prospective cohort study

BACKGROUND

Trauma and surgery may be complicated by pulmonary dysfunction, acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), but the mechanisms are incompletely understood.

METHODS

We evaluated lung capillary protein permeability non-invasively with help of the 67Ga-transferrin pulmonary leak index (PLI) technique and extravascular lung water (EVLW) by the transpulmonary thermal-dye dilution technique in consecutive, mechanically ventilated patients in the intensive care unit within 24 h of direct, blunt thoracic trauma (n = 5, 2 with ARDS), and within 12 h of indirect trauma by transhiatal oesophagectomy (n = 8), abdominal surgery for cancer (n = 6) and bone surgery (n = 4). We studied transfusion history, haemodynamics, oxygenation and mechanics of the lungs. The lung injury score (LIS, 0-4) was calculated. Plain radiography was also done to judge densities and atelectasis.

RESULTS

The PLI and EVLW were elevated above normal in 61 and 30% of patients, respectively, and the PLI directly related to the number of red cell concentrates given (rs = 0.69, P < 0.001), without group differences. Oxygenation, lung mechanics, radiographic densities and thus the LIS (1.0 [0.25-3.5]) did not relate to PLI and EVLW. However, groups differed in oxygenation and airway pressures and impaired oxygenation related to the number of radiographic quadrants with densities (rs = 0.55, P = 0.007). Thoracic trauma patients had a worse oxygenation requiring higher airway pressures and thus higher LIS than the other patient groups, unrelated to PLI and EVLW but attributable to a higher cardiac output and thereby venous admixture. Finally, patients with radiographic signs of atelectasis had more impaired oxygenation and more densities than those without.

CONCLUSION

The oxygenation defect and radiographic densities in mechanically ventilated patients with pulmonary dysfunction and ALI/ARDS after trauma and surgery are likely caused by atelectasis rather than by increased permeability-oedema related to red cell transfusion.

Preliminary Experience with Airway Pressure Release Ventilation in a Trauma/Surgical Intensive Care Unit

BACKGROUND

Airway pressure-release ventilation (APRV) is a pressure-limited, time-cycled mode of mechanical ventilation. The purpose of this study was to evaluate our initial experience with the use of APRV in acutely injured, ventilated patients.

METHODS

Since March 2003, APRV has been used selectively in adult trauma patients with or at risk for acute lung injury/acute respiratory distress syndrome. Data were obtained before and during the 72 hours after switching to APRV. A retrospective analysis of these data was then performed.

RESULTS

Complete data were available on 46 of 60 patients (77%) for the first 72 hours of APRV. Before APRV, the average Pao2/Fio2 ratio was 243 and the average peak airway pressure was 28 cm H2O. Peak airway pressure decreased 19% (p = 0.001), Pao2/Fio2 improved by 23% (p = 0.017) and release tidal volumes improved by 13% (p = 0.020) over the course of the analysis.

CONCLUSION

APRV significantly improved oxygenation by alveolar recruitment and allowed for a reduction in peak airway pressures. This relatively new modality had favorable results and appears to be an effective alternative for lung recruitment in traumatically injured patients at risk for acute lung injury/acute respiratory distress syndrome.