Analysis of the fraction of delivered oxygen by noninvasive ventilation devices working as invasive ventilators in pandemic times

Purpose: In the context of the COVID-19 pandemic, mandatory ventilation with noninvasive ventilation (NIV) devices is a valid option when intensive care/anesthesia ventilators are unavailable. The fraction of delivered oxygen (FDO2) by NIV devices in intubated patients is unknown.Method: We simulated intubated patients with normal and sick lungs. NIV was used in pressure control mode with protective lung ventilatory settings. O2 flow was added into the NIV circuit in incremental steps of 1 L/min (from 1 to 15 L). The FDO2 in breathing gases was measured by a paramagnetic O2 sensor placed behind the endotracheal tube. Three NIV circuit options were analyzed: 1) leak at HME filter close to the patient, 2) anesthesia Bain circuit with leak distal to the patient, and 3) leak throughout a non-rebreathing valve near the patient.Results: FDO2 increased proportional to the supplemental O2 flow in all NIV options and in both kinds of patients. The range of FDO2 came from 0.25 to 0.98 in both, healthy and sick lungs. At 5 L/min, FDO2 was 0.53±0.04 and 0.47±0.02 in option 1 and 0.53±0.04 and 0.47±0.02 in option 2 for healthy and sick lungs, respectively. In option 3, 5 L/min of O2 reached 0.84±0.08 in healthy and 0.74±0.09 in sick lungs. Conclusions: In all setups, FDO2 was proportional to the administered O2 flow and it covered the range of FDO2 values commonly observed in ventilated patients.

In Vitro Study of Magnetic Resonance Imaging Artifacts of Anesthetic Devices

Introduction: Deep sedation or general anesthesia is usually required for Magnetic Resonance Imaging when patients cannot remain motionless in the suite. Various anesthetic devices have been used to maintain the airway and ventilate the lungs during this period but some of them produce artifacts that pose difficulties in the interpretation of images. The aim of this study was to identify the devices that produced artifacts during Magnetic Resonance Imaging.Methods: Twelve anesthetic devices were considered: oro-pharyngeal airway, naso-pharygeal airway, face mask with reservoir bag, nasal cannula, endotracheal tube, disposable Ambu Laryngeal Mask Airway, Laryngeal Mask Airway Unique, Disposable Laryngeal Tube Sonda, i-gel, Ambubag, Bain Circuit, Jackson Rees Circuit.Magnetic Resonance Imaging was performed with each device placed on the top of a phantom simulator respectively to resemble the position in vivo.Results: The artifacts with Disposable Laryngeal Tube Sonda, Laryngeal Mask Airway Unique and endotracheal tube were related to ferromagnetic material in the pilot valve were similar. No artifacts were found with oro-pharyngeal airway, naso-pharygeal airway, nasal cannula, endo-tracheal tube with pilot valve detached, face masks with reservoir bag (metal removed), Ambu bag (without Adjustable Pressure Limiting valve), i-gel , disposable Ambu Laryngeal Mask Airway, Bain Circuit and Jackson Rees Circuit.Conclusions: Anesthetic devices not containing any ferromagnetic material are recommended for use during MRI scanning to reduce artifacts.

In vitro study of Magnetic Resonance Imaging artifacts of anesthetic devices

Background: Deep sedation or general anesthesia is usually required for Magnetic Resonance Imaging when patients cannot remain motionless in the suite. Various anesthetic devices have been used to maintain the airway and ventilate the lungs during this period. Some of them produce artifacts that pose difficulties in the interpretation of images. The aim of this study was to identify the devices that produced artifacts during Magnetic Resonance Imaging.Methods: Twelve anesthetic devices were considered: oro-pharyngeal airway, nasopharygeal airway, face mask with reservoir bag, nasal cannula, endotracheal tube, disposable Ambu Laryngeal Mask Airway, Laryngeal Mask Airway Unique, Disposable Laryngeal Tube Sonda, i-gel, Ambu bag, Bain Circuit, Jackson Rees Circuit. Magnetic Resonance Imaging was performed with each device placed on the top of a phantom simulator respectively to resemble the position in vivo.Results: The artifacts with Disposable Laryngeal Tube Sonda, Laryngeal Mask Airway Unique and endotracheal tube were related to ferromagnetic material in the pilot valve and were similar. No artifacts were found with oro-pharyngeal airway, nasopharygeal airway, nasal cannula, endo-tracheal tube with pilot valve detached, face masks with reservoir bag (metal removed), Ambu bag (without Adjustable Pressure Limiting valve), i-gel , disposable Ambu Laryngeal Mask Airway, Bain Circuit and Jackson Rees Circuit.Conclusion: Anesthetic devices that produce Magnetic Resonance Imaging artifacts are disposable Laryngeal Tube Sonda, Laryngeal Mask Airway Unique and Endotracheal Tube.Journal of Society of Anesthesiologists of Nepal 2015; 2(1): 13-16