Mechanical ventilation
Numerous lines of evidence have demonstrated that inappropriate
mechanical ventilatory settings can produce
further lung damage to patients with ARDS. Ventilatorinduced
lung injury seems to be attributed to endinspiratory
overdistension and a low end-expiratory lung
volume, allowing repeated collapse and re-expansion with
each respiratory cycle (tidal recruitment). Tidal recruitment
results in high shear force on alveolar walls and small airways
during inflation, especially at the interfaces between
collapsed and aerated alveoli. Therefore, low tidal volume
(6 mL/kg of predicted body weight), limitation of plateau
pressure (less than 28–30 cm H2O), and appropriate PEEP
is a key component of a lung-protective ventilatory strategy
(LPVS) [21]. Since then, the lung-protective mechanical
ventilation strategy has been the standard practice for the
management of ARDS. In a retrospective observational
study of 104 patients with ARDS caused by pandemic influenza
A/H1N1 infection admitted to 28 ICUs in South
Korea, low-tidal volume (TV) mechanical ventilation still
benefited patients with ARDS caused by viral pneumonia.
Patients with TV less than or equal to 7 mL/kg required
ventilation, ICU admission, and hospitalization for fewer
days than those with TV greater than 7 mL/kg (11.4 vs.
6.1 days for 28-day ventilator-free days, 9.7 vs. 4.9 days for
28-day ICU-free days, and 5.2 vs. 2.4 days for 28-day
hospital-free days, respectively). A tidal volume greater
than 9 mL/kg (hazard ratio, 2.459; P = 0.003) and the Sequential
Organ Failure Assessment score (hazard rate,
1.158; P = 0.014) were significant predictors of 28-day ICU
mortality [22].