Principal Investigator Alexander Slocum
Respiratory disease, often culminating in respiratory failure, is a significant and rapidly growing problem in developing countries. Access to mechanical ventilation is critical for avoiding devastating vital organ injury, fetal hypoxemia and/or death, however mechanical ventilators are in short supply largely due to their high acquisition ($10,000-$30,000) and maintenance costs; significant training and personnel requirements related to the complexity of current hospital ventilators; and inequitable or geographically limited distribution of existing mechanical ventilators. Hospitals in developing countries often use refurbished, but still costly, ventilators ($2,000-15,000); borrow from each other; or forego mechanical ventilation entirely, resulting in substantial morbidity and mortality.
We have developed an early prototype adult ventilator. The current prototype is an Assist-Control ventilator with a variable tidal volume (200-750 cc), respiratory rate (5-30) with minute ventilation ranging from 1.5 to 21 liters per minute. The novel cam mechanism compresses a bag resuscitator, a widely available and inexpensive device (approximately $10-12). The crescent-shaped cam allows smooth, repeatable deformation to ensure constant air delivery. As it rotates, the cam makes rolling contact along the surface of the bag. The tidal volume delivered is an approximately linear function of the cam angle, integrating the flow delivered. The cam is molded with an integral partial gear, driven by a pinion (small gear) attached to a stepper motor. This device could be used for ventilation with an endotracheal tube and for non-invasive ventilation with a mask. The current early prototype operates in an assist-control (AC) mode, used for the vast majority of adult patients ventilated in critical care units. The operator selects the tidal volume appropriate to the patient, usually 6-8 mL/kg for adults and a minimum respiratory rate, providing a minimum assured minute ventilation (Ve). If the patient is breathing above the set rate, negative inspiratory pressure that exceeds 2 cm H20 vacuum triggers the ventilator to deliver the set tidal volume. The working prototype has low power requirements, running for 3.5 hours on one battery charge at its most demanding setting. It is portable, weighing 9 lb and measuring 11.25 x 6.7 x 8 inches. This prototype cost less than $400 to make, but in mass production the cost will likely be less than half this amount.