Index
It is a medical device for delivering a known oxygen concentration to patients on controlled oxygen therapy.
The Venturi mask is also known as an air entrainment mask .
The mask was invented by Moran Campbell at McMaster University School of Medicine as a replacement for intermittent oxygen treatment, a practice he described as “bringing a drowning man to the surface, occasionally.”
Venturi masks are considered high-flow oxygen therapy devices.
This is because Venturi masks are capable of providing full inspiratory flow at a specific fraction of inspired oxygen (FiO2) for patient therapy.
Kits generally include multiple jets, which are generally color-coded, to establish the desired fraction of inspired oxygen (FiO2).
Other brands of masks have a rotating accessory that controls the air entrainment window, which affects the oxygen concentration.
This system is often used with entrained air nebulizers to provide humidification and oxygen therapy.
Mechanism
The mechanism of action is generally incorrectly cited based on the Venturi effect. Even though there is no evidence for this, many textbooks and magazine articles cite this as the mechanism.
However, a fixed performance oxygen delivery system, even though it is often called a Venturi mask, works on the principle of jet mixing.
With the Venturi mask system, the oxygen inlet connects to a specific color-coded entrainment device at the base of the mask that provides a set fraction of inspired oxygen (FIo2) at a set oxygen intake rate.
Various entrainment devices can provide an inspired oxygen fraction (FIo2) of 0.24 to 0.5, with an oxygen input of 4 to 15 L / min and a total flow delivered to the patient (including trapped air) of 35 to 45 L / min. min.
If the patient’s peak inspiratory flow exceeds this total flow, a lower fraction of inspired oxygen (FIo2) is inspired.
The Venturi mask is ideal for a patient with chronic obstructive pulmonary disease (COPD) who has a low to moderate oxygen requirement but is at risk for hypercarbia with uncontrolled oxygen therapy.
Uses of the Venturi mask
Supply of supplemental oxygen at a precise concentration.
The Venturi mask is commonly used for oxygen delivery, particularly in patients in whom an inappropriately high fraction of inspired oxygen (FiO2) must be avoided.
Oxygen is supplied at high speed through a small hole, and shear forces cause the room air and oxygen to mix.
The fraction of inspired oxygen (FiO2) can be adjusted using mask adapters of different orifice sizes.
The gas flow delivered to the patient always exceeds the minute ventilation, which prevents entrainment of room air around the mask and oxygen dilution, but the oxygen flow rate requires adjustment for each orifice size.
Delivering oxygen at flow rates that exceed minute ventilation provides a target fraction of inspired oxygen (FiO2) and also ensures adequate carbon dioxide removal.
While the precise fraction of inspired oxygen (FiO2) can be obtained and varied according to patient demand with the Venturi mask, options are limited to a specific size and number of adapters, and oxygen flow rates are increasingly required high to deliver a higher fraction of inspired oxygen (FiO2).
Flow problems
Air entrainment masks, although considered high-flow systems, cannot always guarantee full flow with oxygen percentages greater than 35% in patients with high inspiratory flow demands.
The problem with air entrainment systems is that as the fraction of inspired oxygen (FiO2) increases, the ratio of air to oxygen decreases. For example, for 30%, the ratio is eight parts air to one part oxygen.
For 40% the ratio decreases to 3: 1. Since the jets in Venturi masks generally limit the flow of oxygen to 12 to 15 liters per minute, the total flow decreases as the ratio decreases.
With an oxygen flow rate of 12 liters per minute and a fraction of 30% inspired oxygen (FiO2), the total flow would be 108 L / min. At a fraction of 40% of the inspired oxygen setting (FiO2), the total flow would decrease to 48 L / min.
Comparison of OxyMask and Venturi mask
While the Venturi mask is effective in providing accurate oxygen concentrations (FiO2), it requires relatively high oxygen flow rates to achieve this.
The OxyMask is a new oxygen delivery mask that uses a small “diffuser” to concentrate and direct oxygen to the nose and mouth, providing high concentrations of oxygen at a relatively low flow rate.
Our hypothesis is that this system delivers oxygen more efficiently and more comfortably than the conventional Venturi mask.
We studied this hypothesis by assessing supplemental oxygen in oxygen-dependent patients through an OxyMask and Venturi mask in a randomized, single-blind, crossover design.
Although the technology of the diffuser has been evaluated before, it has been predominantly in healthy volunteers, in which the diffuser was placed in a plastic pen connected to an earpiece.
Only previous research has used the OxyArm in oxygen-dependent patients.
However, the authors did not provide information on the severity of the disease, including measurements of lung function and arterial blood gases.
Consequently, it is unknown how the severity of the disease, including the presence of chronic carbon dioxide retention, affects the effectiveness of diffusion technology. Also, the diffuser has not been evaluated while being placed on a face mask.
These differences in patient population and mask design may limit the application of this new technology in patients with severe lung disease.
Consequently, we conducted a pilot study in a group of stable oxygen-dependent patients to determine whether OxyMask can deliver oxygen more safely and efficiently than the Venturi system in this patient population.
Mask efficiency
Based on the study design, blood oxygen saturation (SaO2) did not differ significantly between oxygen titrations using the original OxyMask or Venturi mask.
The oxygen flow rate was significantly lower when using the OxyMask during the low and high oxygen saturation (SaO2) titrations.
Oxygen flow was significantly higher for both masks during high oxygen saturation (SaO2) (P <0.001), and the difference in flow rate when using OxyMask compared to the Venturi mask was greater during high oxygen saturation. (SaO2) (P <0.001).
Inspired oxygen partial pressure (PO2) was significantly higher and expired oxygen partial pressure (PO2) significantly lower when using OxyMask compared to the Venturi mask.
Inspired and expired oxygen partial pressure (PO2) was significantly higher during high oxygen saturation (SaO2) (P <0.001), and the difference in oxygen partial pressure (PO2) when using OxyMask compared to the Venturi mask it was higher during oxygen saturation (SaO2) (P <0.05).
Minute ventilation and inspired and expired partial pressure of carbon dioxide (PCO2) were significantly higher when using the original oxygen mask than the Venturi mask.
Transcutaneous carbon dioxide partial pressure (PCO2), heart rate, and nasal to oral respiration ratio did not change significantly throughout the study.
Similarly, the study design required that there be no difference in blood oxygen saturation (SaO2) during the comparison of the modified oxygen mask and the Venturi mask.
The oxygen flow rate was significantly lower when using the modified OxyMask compared to the Venturi mask.
Oxygen flow was significantly greater during high oxygen saturation (SaO2) (P <0.001) and the difference in flow rate while wearing the modified OxyMask compared to the Venturi mask was greater during high oxygen saturation ( SaO2) (P <0.001).
The inspired partial pressure of oxygen (PO2) was significantly higher and the expired partial pressure of oxygen (PO2) was significantly lower when using the modified oxygen mask than the Venturi mask.
The inspired and expired partial pressure of oxygen (PO2) was significantly higher during high oxygen saturation (SaO2) and the difference in inspired partial pressure of oxygen (PO2) when using the modified OxyMask compared to the Venturi mask was greater during high oxygen saturation (SaO2).
Although the inspired partial pressure of carbon dioxide (PCO2) was significantly higher when using the modified OxyMask compared to the Venturi mask, the magnitude of the increase was approximately half that observed with the original OxyMask.
Also, unlike what was found with the original OxyMask, the minute ventilation and expired partial pressure of carbon dioxide (PCO2), in addition to the transcutaneous partial pressure of carbon dioxide (PCO2), were not significantly different when using the modified OxyMask compared to the Venturi mask.
Heart rate and the ratio of nasal to oral respiration did not change significantly throughout the study. Analysis of chronic hypercapnic patients alone showed similar results.
Satisfaction mask
There was a trend for a higher mask comfort rating for the original OxyMask than for the Venturi mask, but this difference did not reach statistical significance on the comfort scale.
Similarly, mask comfort ratings tended to be higher for the modified OxyMask than for the Venturi mask, but this difference did not reach statistical significance.
The rave reviews on the original and modified OxyMask were that it was quiet, lightweight and fitted better, was less wet and less intrusive than the Venturi mask.
