Data automated bag breathing unit for COVID-19 ventilator shortages.

BACKGROUND: The COVID-19 pandemic has caused a global mechanical ventilator shortage for treatment of severe acute respiratory failure. Development of novel breathing devices has been proposed as a low cost, rapid solution when full-featured ventilators are unavailable. Here we report the design, bench testing and preclinical results for an 'Automated Bag Breathing Unit' (ABBU). Output parameters were validated with mechanical test lungs followed by animal model testing. RESULTS: The ABBU design uses a programmable motor-driven wheel assembled for adult resuscitation bag-valve compression. ABBU can control tidal volume (200-800 ml), respiratory rate (10-40 bpm), inspiratory time (0.5-1.5 s), assist pressure sensing (- 1 to - 20 cm H2O), manual PEEP valve (0-20 cm H2O). All set values are displayed on an LCD screen. Bench testing with lung simulators (Michigan 1600, SmartLung 2000) yielded consistent tidal volume delivery at compliances of 20, 40 and 70 (mL/cm H2O). The delivered fraction of inspired oxygen (FiO2) decreased with increasing minute ventilation (VE), from 98 to 47% when VE was increased from 4 to 16 L/min using a fixed oxygen flow source of 5 L/min. ABBU was tested in Berkshire pigs (n = 6, weight of 50.8 ± 2.6 kg) utilizing normal lung model and saline lavage induced lung injury. Arterial blood gases were measured following changes in tidal volume (200-800 ml), respiratory rate (10-40 bpm), and PEEP (5-20 cm H2O) at baseline and after lung lavage. Physiological levels of PaCO2 (≤ 40 mm Hg [5.3 kPa]) were achieved in all animals at baseline and following lavage injury. PaO2 increased in lavage injured lungs in response to incremental PEEP (5-20 cm H2O) (p < 0.01). At fixed low oxygen flow rates (5 L/min), delivered FiO2 decreased with increased VE. CONCLUSIONS: ABBU provides oxygenation and ventilation across a range of parameter settings that may potentially provide a low-cost solution to ventilator shortages. A clinical trial is necessary to establish safety and efficacy in adult patients with diverse etiologies of respiratory failure.

Critical-thinking ability in respiratory care students and its correlation with age, educational background, and performance on national board examinations.

BACKGROUND: Critical thinking is an important characteristic to develop in respiratory care students. METHODS: We used the short-form Watson-Glaser Critical Thinking Appraisal instrument to measure critical-thinking ability in 55 senior respiratory care students in a baccalaureate respiratory care program. We calculated the Pearson correlation coefficient to assess the relationships between critical-thinking score, age, and student performance on the clinical-simulation component of the national respiratory care boards examination. We used chi-square analysis to assess the association between critical-thinking score and educational background. RESULTS: There was no significant relationship between critical-thinking score and age, or between critical-thinking score and student performance on the clinical-simulation component. There was a significant (P = .04) positive association between a strong science-course background and critical-thinking score, which might be useful in predicting a student's ability to perform in areas where critical thinking is of paramount importance, such as clinical competencies, and to guide candidate-selection for respiratory care programs.

Delivered oxygen concentrations using low-flow and high-flow nasal cannulas.

INTRODUCTION: Nasal cannulas are commonly used to deliver oxygen in acute and chronic care settings; however, there are few data available on delivered fraction of inspired oxygen (F(IO(2))). The purposes of this study were to determine the delivered F(IO(2)) on human subjects using low-flow and high-flow nasal cannulas, and to determine the effects of mouth-closed and mouth-open breathing on F(IO(2)). METHODS: We measured the pharyngeal F(IO(2)) delivered by adult nasal cannulas at 1-6 L/min and high-flow nasal cannulas at 6-15 L/min consecutively in 10 normal subjects. Oxygen was initiated at 1 L/min, with the subject at rest, followed by a period of rapid breathing. Gas samples were aspirated from a nasal catheter positioned with the tip behind the uvula. This process was repeated at each liter flow. Mean, standard deviation, and range were calculated at each liter flow. F(IO(2)) during mouth-open and mouth-closed breathing were compared using the dependent test for paired values, to determine if there were significant differences. RESULTS: The mean resting F(IO(2)) ranged from 0.26-0.54 at 1-6 L/min to 0.54-0.75 at 6-15 L/min. During rapid breathing the mean F(IO(2)) ranged from 0.24-0.45 at 1-6 L/min to 0.49-0.72 at 6-15 L/min. The mean F(IO(2)) increased with increasing flow rates. The standard deviation (+/- 0.04-0.15) and range were large, and F(IO(2)) varied widely within and between subjects. F(IO(2)) during mouth-open breathing was significantly (p < 0.05) greater than that during mouth-closed breathing. CONCLUSIONS: F(IO(2)) increased with increasing flow. Subjects who breathed with their mouths open attained a significantly higher F(IO(2)), compared to those who breathed with their mouths closed.