Generally accepted indications for mechanical ventilatory support include
Anticipation and early aggressive treatment of pulmonary insufficiency by mechanical ventilatory support are critical in managing the seriously ill patient. Readily measured changes that can be used to determine either the need for intubation or the appropriate time for weaning from mechanical respiratory support include arterial blood gas levels, dead space-tidal volume ratio (VD /VT ), alveolar-arterial oxygen tension difference , vital capacity, and respiratory rate. Indications for mechanical ventilation include a respiratory rate over 35 breaths/min, vital capacity less than 15 mL/kg, greater than 350 kPa after 15 min on 100% oxygen, VD /VT greater than 0.6, PaO2 less than 60 kPa, and PaCO2 greater than 60 kPa.
PaO2 of less than 70 kPa and PaCO2 of greater than 50 kPa while breathing room air
Alveolar-arterial oxygen tension difference of 150 kPa while breathing 100% O2
Vital capacity of 40-60 mL/kg
Respiratory rate greater than 35 breaths/min
Fluid & Electrolyte