May only be temporary benefit
Hemodynamic instability with drop off in preload
CO2 retention
May worsen oxygenation by shunting blood to poorly aerated<unk>  (opposing physiological hypoxic pulmonary vasoconstriction)
May worsen ventilator-induced<unk>  injury with volutrauma/barotrauma
Pneumothorax
Contraindications
Unstable BP
pneumothorax or high risk of pneumothorax (blebs, necrotising pneumonia)
ARDS > 1 wk (relative contraindication)
Unstable BP
pneumothorax or high risk of pneumothorax (blebs, necrotising pneumonia)
ARDS > 1 wk (relative contraindication)
Lung recruitment maneuver
Pulmonary antibiotics
High frequency oscillation ventilation
Airway pressure release ventilation
Needle cricothyrotomy
Thoracic lavage
Mechanical ventilation 
Bag valve mask ventilation