Bhabajyoti Bora, Nibedita Devi, Prathana Goswami, Mihir Kumar Goswami
BACKGROUND Acute lung injury (ALI) and its most severe manifestation, acute respiratory distress syndrome (ARDS), are defined by physiological criteria i.e. ratio of PaO2 to inspiratory oxygen fraction (FIO2) ≤ 300 mmHg for ALI and ≤ 200 mmHg for ARDS, independent of positive end expiratory pressure (PEEP)) and by bilateral pulmonary infiltrates as radiological criteria. The ARDS Definition Task Force proposes a new classification according to the severity of ARDS, i.e. mild: PaO2/FIO2 > 200 mmHg and ≤ 300 mmHg; moderate: PaO2/FIO2 >100 mmHg and ≤200 mmHg; and severe: PaO2/FIO2 ≤100 mmHg, because of its better predictive value for mortality. Principles of protective ventilator settings for patients with ALI/ARDS are low tidal volume (i.e. VT 6 mL per kg ideal body weight, plateau pressure <30 cm H2O and peak pressure <35 cm H2O). Permissive hypercapnia may be helpful to realize protective mechanical ventilation. Protection of the lungs may also be provided by the pump-driven venovenous ECMO or pump less ILA. Cardiac failure must be excluded based either on pulmonary artery wedge pressure (<18 mmHg) or on clinical evaluation of left ventricular function, if the invasive measurement is unavailable, which is the ground reality of the unfortunate situation here in the medical colleges of Assam as well as in India.
