Misty-Ox (MO)® nebulizer was developed to overcome shortcomings of conventional air-entrainment devices. The MISTY OX ® is designed to deliver FIO2s from 0.60 to 0.96 with total gas flows from 42 to 80 L/min. The THERA MIST® nebulizer is designed to deliver FIO2s from 0.36-0.96 with total gas flows from 47 to 74 L/min. We sought to determine the actual delivered FIO2 when using the MISTY OX® and the THERA MIST® via aerosol mask in normal subjects.
Following informed consent, 12 healthy volunteers, had a size 8 french nasal catheter (NC) inserted through one of the nares with the tip positioned at the level of the uvula. Subjects were placed on the THERA MIST® connected to large bore tubing and an aerosol mask. Oxygen therapy was then initiated at a set FIO2 of 0.60 at 15 L/min, then 0.80 and 0.95 at flush for a period of five minutes. The subjects were also placed on the Misty-Ox ® connected to large bore tubing and an aerosol mask. Oxygen therapy was then initiated at a set FIO2 of 0.65, 0.85 and 0.96 at 40 L/min flow using a high-flow flowmeter for a period of five minutes. With the subject breathing normally the gas was analyzed at three sites: the nebulizers’ outlet, the subjects’ lip and from the subjects’ pharynx. A previously calibrated oxygen analyzer measured the FIO2 of these samples. Three samples were obtained from each site, at each FIO2 setting and the mean and standard deviations were calculated.
Means, standard deviations and ranges for the analyzed oxygen concentrations are included in the Table.
Delivered FIO2 using the Thera Mist and the Misty Ox nebulizers can vary significantly from the set value. The delivered O2 can be 10 - 20 percent below the set value.
Care should be taken when interpreting patients’ clinical response to oxygen therapy when using these devices. Patient may be receiving a FIO2 much less than anticipated based on the nebulizer setting.
Analyzed FIO2 (SD) for High Oxygen Concentration Devices*DeviceThera MistMisty OxSet FIO2.0600.800.950.650.850.96Location of AnalysisNebulizer Outlet.53 (.03).74(.05).86(.05).64(.03).80(.03).86(.04)Subject’s Lip.56 (.04).72(.06).84(.05).63(.03).79(.04).84(.04)Oropharynx.47 (.03).65(.05).75(.06).56(.04).70(.06).73(.06)*
Mean (SD) of all subjects
Donna Gardner, None.