Manual ventilation with a bag mask is a safe method to use while transporting patients from the cardiac surgery operating room (OR) to the ICU, a study has found.
Manual ventilation caused a greater excursion in end-tidal carbon dioxide (EtCO2) than machine ventilation of intubated patients during a short transport from surgery to the ICU, but this did not translate into any difference in hemodynamic changes, according to E. Orestes O’Brien, MD, clinical chief of the Anesthesiology Critical Care Medicine Service at Thornton Hospital and Sulpizio Cardiovascular Center, in La Jolla, Calif., who was the lead author of the study.
“We found significant changes in [EtCO2], but no significant changes in vital signs or pulmonary pressures,” said Dr. O’Brien, who is also associate clinical professor, Department of Anesthesiology at the University of California, San Diego. The findings were presented at the 2017 annual meeting of the Society for Critical Care Medicine (abstract 157).
Dr. O’Brien and his colleagues randomly assigned 36 patients to one of two groups: The first received manual ventilation with a self-inflating bag-valve resuscitator and the second was attached to a portable transport ventilator (LTV 1200 Series Ventilator, CareFusion).
Key Fact: A Short Transport Time
The researchers measured each patient’s vital signs, including blood pressure, heart rate, respiratory rate, blood oxygen saturation levels, exhaled tidal volume and EtCO2 every two minutes during transport. They also measured each patient’s pulmonary artery pressures just before and just after transport, and recorded the initial values in the ICU.
The anesthesiologist who provided the anesthesia during the procedure performed the manual ventilation. The respiratory therapist set the ventilators to deliver a tidal volume and respiratory rate equal to the values used during the patient’s surgery.
Average transport times were five minutes for patients ventilated by hand and 5.47 minutes for patients using a transport ventilator (P=0.369). The difference in all measured changes in EtCO2 between manually and machine-ventilated patients during transport was 2.74 mm Hg (P=0.013). The difference between OR and ICU EtCO2 in each cohort was 1.31 mm Hg (P=0.067).
“Some problems with transport ventilators have been reported,” Dr. O’Brien said. “These include mechanical failure, early battery discharge, and failure of the device to deliver preset tidal volumes when the compliance of the lung is changing, as sometimes happens during transport.”
Despite these problems, Dr. O’Brien said that based on the study, he could not conclude that hand ventilation was preferable. “I can conclude that it is not worse than machine ventilation. Machines don’t result in more stable vital signs at the end of transport than hand ventilation does. The take-home message is that hand ventilation is safe for transport after cardiac surgery. We don’t always have to use a transport ventilator to have a stable, safe transport between OR and ICU.”
Dr. O’Brien added that all of the transports in the study were accomplished in relatively brief periods of time. “The results of longer transports may be different.”
Gregory J. Schears, MD, an anesthesiologist and intensivist at Mayo Clinic, in Rochester, Minn., who was asked to comment on the study, said due to the short duration of transport, one may not see much of an impact compared with transports lasting 15 minutes or more. “Also, it would be difficult to blind the groups. Thus, the individual bagging may be paying more attention to the EtCO2 than under non-study conditions and is keeping the number closer to the original pretransport value.”
He added that for some postcardiotomy patient populations, changes in EtCO2 can have a significant effect on hemodynamics during a vulnerable time. “Regardless of the approach, attention must be paid to not allow the number to drift outside an acceptable range for a given patient.”