Delivery of high flow oxygen through nasal vs. tracheal cannulas: A bench study.

Background: The use of high flow oxygen therapy (HFOT) has significantly escalated during the COVID-19 pandemic. HFOT can be delivered through both dedicated devices and ICU ventilators. HFOT can be administered to a patient via a nasal cannula (NC). In intubated patients, a tracheal cannula (TC) is used instead. In this study, we aim to compare the work of breathing (WOB) using a TC or NC and to explore whether differences exist among HFOT devices. Methods: Seven HFOT devices (three dedicated and four ICU ventilators) were connected to a manikin head (Laerdal Medical) through a NC (Optiflow 3S, large size, Fisher and Paykel Healthcare) or a TC (OPT 970 Optiflow+, Fisher and Paykel Healthcare). Each device was also attached to a manikin head that was connected to a lung simulator (ASL5000, Ingmar Medical), set at 40 ml/cmH2O compliance, 10 cmH2O/L/s resistance, and sinusoidal inspiratory effort (muscular pressure 10 cmH2O, rate 30 breaths/min). HFOT was delivered at 40 L/min and at 21% inspired oxygen fraction. The total WOB per breath and its resistive and elastic components were automatically analyzed breath by breath over the last 20 breaths by using Campbell's diagram. Results: The WOB and its resistive and elastic components were significantly lower with the TC than with the NC for every device, and systematically lower with the reference device than with others. These differences were, however, very small and may be not clinically relevant. Conclusion: The WOB is lower with the TC than with the NC and with the reference device, compared with the most recent devices.

Delivery of high flow oxygen through nasal vs. tracheal cannulas: A bench study

Background The use of high flow oxygen therapy (HFOT) has significantly escalated during the COVID-19 pandemic. HFOT can be delivered through both dedicated devices and ICU ventilators. HFOT can be administered to a patient via a nasal cannula (NC). In intubated patients, a tracheal cannula (TC) is used instead. In this study, we aim to compare the work of breathing (WOB) using a TC or NC and to explore whether differences exist among HFOT devices. Methods Seven HFOT devices (three dedicated and four ICU ventilators) were connected to a manikin head (Laerdal Medical) through a NC (Optiflow 3S, large size, Fisher and Paykel Healthcare) or a TC (OPT 970 Optiflow+, Fisher and Paykel Healthcare). Each device was also attached to a manikin head that was connected to a lung simulator (ASL5000, Ingmar Medical), set at 40 ml/cmH2O compliance, 10 cmH2O/L/s resistance, and sinusoidal inspiratory effort (muscular pressure 10 cmH2O, rate 30 breaths/min). HFOT was delivered at 40 L/min and at 21% inspired oxygen fraction. The total WOB per breath and its resistive and elastic components were automatically analyzed breath by breath over the last 20 breaths by using Campbell's diagram. Results The WOB and its resistive and elastic components were significantly lower with the TC than with the NC for every device, and systematically lower with the reference device than with others. These differences were, however, very small and may be not clinically relevant. Conclusion The WOB is lower with the TC than with the NC and with the reference device, compared with the most recent devices.

A Bench Comparison of the Effect of High-Flow Oxygen Devices on Work of Breathing.

BACKGROUND: Oxygen therapy via high-flow nasal cannula (HFNC) has been extensively used during the COVID-19 pandemic. The number of devices has also increased. We conducted this study to answer the following questions: Do HFNC devices differ from the original device for work of breathing (WOB) and generated PEEP? METHODS: Seven devices were tested on ASL 5000 lung model. Compliance was set to 40 mL/cm H2O and resistance to 10 cm H2O/L/s. The devices were connected to a manikin head via a nasal cannula with FIO2 set at 0.21. The measurements were performed at baseline (manikin head free of nasal cannula) and then with the cannula and the device attached with oxygen flow set at 20, 40, and 60 L/min. WOB and PEEP were assessed at 3 simulated inspiratory efforts (-5, -10, -15 cm H2O muscular pressure) and at 2 breathing frequencies (20 and 30 breaths/min). Data were expressed as median (first-third quartiles) and compared with nonparametric tests to the Optiflow device taken as reference. RESULTS: Baseline WOB and PEEP were comparable between devices. Over all the conditions tested, WOB was 4.2 (1.0-9.4) J/min with the reference device, and the relative variations from it were 0, -3 (2-4), 1 (0-1), -2 (1-2), -1 (1-2), and -1 (1-2)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test). PEEP was 0.9 (0.3-1.5) cm H2O with Optiflow, and the relative differences were -28 (22-33), -41 (38-46), -30 (26-36), -31 (28-34), -37 (32-42), and -24 (21-34)% with Airvo 2, G5, HM80, T60, V500, and V60 Plus devices, respectively, (P < .05 Kruskal-Wallis test). CONCLUSIONS: WOB was marginally higher and PEEP marginally lower with devices as compared to the reference device.

Simultaneous ventilation in the Covid-19 pandemic. A bench study.

COVID-19 pandemic sets the healthcare system to a shortage of ventilators. We aimed at assessing tidal volume (VT) delivery and air recirculation during expiration when one ventilator is divided into 2 test-lungs. The study was performed in a research laboratory in a medical ICU of a University hospital. An ICU (V500) and a lower-level ventilator (Elisée 350) were attached to two test-lungs (QuickLung) through a dedicated flow-splitter. A 50 mL/cmH2O Compliance (C) and 5 cmH2O/L/s Resistance (R) were set in both A and B test-lungs (A C50R5 / B C50R5, step1), A C50-R20 / B C20-R20 (step 2), A C20-R20 / B C10-R20 (step 3), and A C50-R20 / B C20-R5 (step 4). Each ventilator was set in volume and pressure control mode to deliver 800mL VT. We assessed VT from a pneumotachograph placed immediately before each lung, pendelluft air, and expiratory resistance (circuit and valve). Values are median (1st-3rd quartiles) and compared between ventilators by non-parametric tests. Between Elisée 350 and V500 in volume control VT in A/B test- lungs were 381/387 vs. 412/433 mL in step 1, 501/270 vs. 492/370 mL in step 2, 509/237 vs. 496/332 mL in step 3, and 496/281 vs. 480/329 mL in step 4. In pressure control the corresponding values were 373/336 vs. 430/414 mL, 416/185 vs. 322/234 mL, 193/108 vs. 176/ 92 mL and 422/201 vs. 481/329mL, respectively (P<0.001 between ventilators at each step for each volume). Pendelluft air volume ranged between 0.7 to 37.8 ml and negatively correlated with expiratory resistance in steps 2 and 3. The lower-level ventilator performed closely to the ICU ventilator. In the clinical setting, these findings suggest that, due to dependence of VT to C, pressure control should be preferred to maintain adequate VT at least in one patient when C and/or R changes abruptly and monitoring of VT should be done carefully. Increasing expiratory resistance should reduce pendelluft volume.