Volume-controlled ventilation with Breas LTV 1000 ventilators under hypobaric conditions. A lung simulator analysis.

DOI: 10.36210/BerMedJ/epub02202022

Abstract

The successful functioning of ventilators under varying ambient conditions depends strongly on barometric pressure and gas density. We examined volume-controlled ventilation using the LTV 1000 Breas ventilator under hypobaric conditions in a typical high altitude profile. The LTV 1000 ventilator administers significantly higher tidal volumes at altitudes above 5000 feet (PBARO=633 mmHg), surpassing the reference ranges (VT ±10%) of all selected tidal volumes. The mean volume increase was 235±66 mL for VT=500 mL, 296±83 mL for VT=700 mL and 414±77 mL for VT=1000 mL. The reason for this lies in the physical changes defined by Boyle’s Law, which lead to volume expansion at low pressure and faulty flow measurements of expiratory volumes due to changes in gas density. Appropriate monitoring is thus recommended when using the LTV 1000 ventilator in volume-controlled ventilation mode under varying ambient conditions above 5000 feet. The analysis produces a reference value for the reduction in the ground normal tidal volume of 3% per 1000 feet.