The Site of Oxygen Delivery Into a Home Ventilator Affects Recorded Volumes

Long-term home mechanical ventilation is increasingly used by patients with chronic respiratory failure. Storage of medical data in the cloud is expanding, and ventilation can be monitored remotely. The aim of this bench study was to determine whether tidal volume (V_T) can be affected by the location of supplemental oxygen placement.

We tested 4 home ventilators in a bench test using a dual-chamber test lung to test the addition of supplemental oxygen placement via a connector in the circuit (ie, front intake port) versus via the manufacturer's rear intake port, with different oxygen supply flows of 2, 4, 6, and 8 L/min. We compared the effectively delivered V_T as measured with a pneumotachograph (ie, measured V_T) versus the V_T reported by each home ventilator (ie, monitored V_T).

For all of the home ventilators, the monitored V_T and measured V_T were comparable when the rear oxygen intake was used, regardless of oxygen flow. However, when the front oxygen intake was used, the monitored V_T as measured by the ventilators was significantly lower than the measured V_T, with the greatest difference reaching 29% for the highest oxygen flow tested (8 L/min).

The monitored V_T may be inaccurate if oxygen is added with a connector in the circuit, which may have consequences on both the individual level and collective level (ie, big data analysis). Physicians who analyze data from home ventilators should be aware of the site of oxygen supplementation and promote use of only the rear oxygen intake.