Intraocular pressure and mechanical ventilation.

Mechanical ventilation increases superior vena cava pressure and should theoretically increase episcleral venous pressure and intraocular pressure (IOP). A Keeler Pulsair Non Contact Tonometer was used to measure the IOP's of six subjects with no history of glaucoma or ocular hypertension. At 30 min of supine mechanical ventilation of tidal volume with low (7 to 15 cm H2O) peak inspiratory pressures, the IOP's were no different than at the end of a 30-min control period of supine spontaneous ventilation. However, using high (60 cm H2O) peak inspiratory pressures for 1 min after tidal volume ventilation, IOP's were 32.7% higher than at the end of the supine spontaneous ventilation control period (p < 0.05). Patients requiring long-term mechanical ventilation at high peak inspiratory pressures may be at increased risk of vision impairment secondary to machine-induced increase of IOP.