Although most health care professionals meet advanced cardiovascular life support (ACLS) guidelines when ventilating through a self-inflating bag, they do so with wide ranges in various ventilatory end points, which may in turn affect systolic blood pressure. However, a new study has shown that a novel, turbine-driven ventilator meets the same guidelines while providing greater consistency, making it an attractive option in CPR situations.
“For those of us who have done CPR with a bag-valve mask, we sometimes get a bit overzealous,” said Scott Allen, MD, a resident at the University of Utah, Salt Lake City. “We have one job and we want to do it well, so we squeeze like crazy. The Department of Bioengineering at the University of Utah has been developing a portable, battery-powered ventilator that runs off a turbine and doesn’t need a compressed gas source.”
To test the portable ventilator’s relative adherence to ACLS guidelines, Dr. Allen and his colleagues paired 24 ACLS-certified health care practitioners into groups of two. Each team performed four randomized rounds of two-minute cycles of CPR on an intubated manikin, with individuals alternating between compressions and breaths. Two rounds of CPR were performed with a bag-valve self-inflating mask, and two were performed with the new portable ventilator.
The ventilator was set to deliver eight breaths per minute, with a pressure limit of 22 cm H2O. The researchers measured respiratory rate, tidal volume, peak airway pressure and compression interruptions (i.e., hands-off time). Teams also attempted to mask ventilate the extubated manikin with the ventilator and the self-inflating bag.
As reported at the 2014 annual meeting of the International Anesthesia Research Society (abstract S-83), the mean respiratory rate with the ventilator was 8±0.1, compared with 10.1±2.2 for the self-inflating bag. “Although the mean respiratory rate with the self-inflating bag was within the guidelines, the variation was pretty wide. Some people were at 20 per minute while others were at five per minute,” Dr. Allen said.
Mean tidal volume was found to be 0.482±0.022 L with the ventilator and 0.626±0.084 L with the self-inflating bag, respectively, whereas mean peak inspiratory pressure was 22.15±0.314 cm H2O and 31.88±4.47 cm H2O, respectively (Figure). “Some people were close to 50 cm H2O and others were about 20 cm H2O.”
Mean hands-off time was greater with the self-inflating bag (6.41±1.45 seconds) than the ventilator (5.25±2.10 seconds).
The investigators also examined the amount of air that leaked from the respective masks during nonintubated ventilation. The turbine-driven ventilator delivered 2.7 L tidal volume, of which 0.43 L entered the lungs. The self-inflating bag, on the other hand, delivered 0.45 L, of which 0.26 L entered the lungs. “So even though there was much less percentage of a mask leak with the self-inflating bag, the overall volume of air that got into the lungs was higher with the ventilator.”
Although still being developed at the institution, this type of device may ultimately prove its utility in a number of clinical situations, Dr. Allen explained. “In a CPR situation, it will allow people—maybe in an ambulance or an emergency situation—to use this ventilator without having to squeeze the bag, thus freeing up their hands for other things.”
Robert S. Greenberg, MD, associate professor of acute and critical care medicine and pediatrics at the Johns Hopkins Hospital, in Baltimore, said he was not particularly surprised that the turbine-driven ventilator delivered near-perfect respiratory rates and tidal volumes. “The notion of a turbine mechanism to generate the volume to ventilate may be especially interesting in places where there is no—or inconsistent—compressed gases … as in austere environments,” he told Anesthesiology News.