Efficiency of different flows for apneic oxygenation when using high flow nasal oxygen application – a technical simulation

Abstract

Background Preoxygenation and application of apneic oxygenation are standard to prevent patients from desaturation e.g. during emergency intubation. The time before desaturation occurs can be prolonged by applying high flow oxygen into the airway. Aim of this study was to scientifically assess the flow that is necessary to avoid nitrogen entering the airway of a manikin model during application of pure oxygen via high flow nasal oxygen. Methods We measured oxygen content over a 20-min observation period for each method in a preoxygenated test lung applied to a human manikin, allowing either room air entering the airway in control group, or applying pure oxygen via high flow nasal oxygen at flows of 10, 20, 40, 60 and 80 L/min via nasal cannula in the other groups. Our formal hypothesis was that there would be no difference in oxygen fraction decrease between the groups. Results Oxygen content in the test lung dropped from 97 ± 1% at baseline in all groups to 43 ± 1% in the control group (p < 0.001 compared to all other groups), to 92 ± 1% in the 10 L/min group, 92 ± 1% in the 20 L/min group, 90 ± 1% in the 40 L/min group, 89 ± 0% in the 60 L/min group and 87 ± 0% in the 80 L/min group. Apart from comparisons 10 l/ min vs. 20 L/min group (p = .715) and 10/L/min vs. 40 L/min group (p = .018), p was < 0.009 for all other comparisons. Conclusions Simulating apneic oxygenation in a preoxygenated manikin connected to a test lung over 20 min by applying high flow nasal oxygen resulted in the highest oxygen content at a flow of 10 L/min; higher flows resulted in slightly decreased oxygen percentages in the test lung.

Influence of positive end-expiratory pressure on arterial blood pressure in mechanically ventilated trauma patients in the field

“…Thus, while certain interventions may be sound in the laboratory setting, real-life clinical settings may be complex to prove them in the field. There are multiple methods for oxygenation and ventilation 19 20 21 22 23 24 25 26 27 and multiple reasons to apply (moderate) PEEP levels in multiple trauma patients: one of the most important is the prevention of atelectasis resulting in less shunting volume and finally better oxygenation. Further, many multiple trauma patients suffer from severe thoracical trauma where PEEP may be lifesaving by alveolar stabilization.…”

Should We Use High-Flow Nasal Cannula in Patients Receiving Gastrointestinal Endoscopies? Critical Appraisals through Updated Meta-Analyses with Multiple Methodologies and Depiction of Certainty of Evidence

“…The high gas flow passing through a constricted area could decrease the downstream pressure leading to a vacuum effect, a phenomenon also observed in venturi mask [38]. Wetsch et al [39] performed a simulation study which used HFNC for apnea oxygenation. Interestingly, highest oxygen content was reached at a flow of 10 to 20 L per minutes.…”

Identification of the Optimal Position of a Nasal Oxygen Cannula for Apneic Oxygenation - A Technical Simulation

“…Different strategies to deliver oxygen have been described, such as specifically modified oxygenation laryngoscopes, [3,4] oxygenation oropharyngeal tubes, or intratracheal oxygen insufflation with a bronchoscope. [5][6][7] In those studies, the deeper the oxygen was applied, the more effective it was. [6,7] However, we still do not know the optimum depth, or the turning point in the human airway at which oxygen insufflation is more effective than nasal insufflation, and where it is comparably effective as intratracheal insufflation.…”

“…[5][6][7] In those studies, the deeper the oxygen was applied, the more effective it was. [6,7] However, we still do not know the optimum depth, or the turning point in the human airway at which oxygen insufflation is more effective than nasal insufflation, and where it is comparably effective as intratracheal insufflation. While intratracheal oxygen is most effective, it may be technically more difficult and may impair visibility and ease of tracheal tube insertion during intubation attempts, especially in difficult airways.…”