Performance of portable ventilators at altitude

Area of Science:

• Aerospace Medicine
• Critical Care
• Biomedical Engineering

Background:

• Aeromedical transport of critically ill patients necessitates reliable equipment performance at altitude.
• Barometric pressure changes can impact mechanical ventilator function, affecting tidal volume (VT) delivery.
• Maintaining consistent VT is crucial for lung protection during patient transport.

Purpose of the Study:

• To evaluate the altitude compensation capabilities of three mechanical ventilators: Impact 731, Hamilton T1, and CareFusion Revel.
• To determine if ventilators can maintain consistent tidal volume (VT) delivery across varying altitudes and pressures.
• To assess ventilator performance for critical care transport applications.

Main Methods:

• Three ventilators (Impact 731, Hamilton T1, Revel) were tested at pediatric and adult tidal volumes (VT).
• Testing occurred at simulated altitudes of 8,000, 16,000, and 22,000 ft with varying positive end-expiratory pressure and oxygen levels.
• Delivered VT was measured using a pneumotachograph connected to a test lung in an altitude chamber and compared to set VT.

Main Results:

• The Impact 731 ventilator delivered VT within 10% of set VT across all tested altitudes and adult settings.
• The Hamilton T1 and CareFusion Revel showed significant deviations in VT delivery at higher altitudes.
• Circuit compressible volume affected initial VT delivery at sea level for the Revel and 731.

Conclusions:

• The Impact 731 demonstrated superior altitude compensation, actively adjusting for barometric pressure changes.
• Altitude compensation relies on active software algorithms, with only the Impact 731 effectively implementing this.
• The Impact 731's performance ensures reliable lung protection during aeromedical transport.