Effects of oxygen insufflation rate, respiratory rate, and tidal volume on fraction of inspired oxygen in cadaveric canine heads attached to a lung model

Background Although pulmonary function is minimally changed by neuraxial blockade in most cases, ventilatory arrest may ensue in rare cases. The authors examined the mechanism of apnea in a rabbit model of sudden ventilatory arrest during the combination of epidural anesthesia and hypoxia. Methods Rabbits were studied during alpha-chloralose sedation and spontaneous ventilation through a tracheostomy tube. Heart rate and mean arterial pressure were monitored by intraarterial cannulation. Respiratory rate and tidal volume were measured by pneumotachograph. Responses were recorded during administration of oxygen at inspired oxygen concentrations of 11% for 2.5 min and 0% for 40 s, before and after either thoracolumbar epidural blockade (0.4 ml/kg lidocaine, 1.5%) or intramuscular lidocaine (15 mg/kg). In a third group of animals, epinephrine was given intravenously during epidural blockade to return mean arterial pressure to baseline values before hypoxia. In a fourth group of animals, which did not get lidocaine, sympathetic blockade and hypotension were produced with intravenously administered trimethaphan rather than epidural blockade. Results Thoracolumbar epidural anesthesia decreased mean arterial pressure from 76 +/- 4 mmHg (mean +/- SE) to 42 +/- 2 mmHg. Apnea during hypoxia occurred in 90% of these animals (nine of ten) but in only 11% of animals (one of nine) after intramuscularly administered lidocaine (P < 0.01). Treatment of epidural hypotension with epinephrine prevented apnea (zero of nine animals). Apnea during hypoxia occurred in 50% (three of six) of animals given trimethaphan. Apnea in all groups was sudden in onset, with no preceding decreases in respiratory rate or tidal volume. Conclusions Epidural anesthesia results in a narrowed margin of safety for oxygen delivery to the brain and predisposes subjects to ventilatory arrest during hypoxia. This results from the combined effects of decreased blood oxygen content, which is due to decreased inspired oxygen concentration superimposed on circulatory depression due to neural blockade.

Download Full-text

On the Transition from Control Modes to Spontaneous Modes during ECMO

Journal of Clinical Medicine ◽

10.3390/jcm10051001 ◽

2021 ◽

Vol 10 (5) ◽

pp. 1001

Author(s):

Krista Stephens ◽

Nathan Mitchell ◽

Sean Overton ◽

Joseph E. Tonna

Keyword(s):

Respiratory Rate ◽

Multivariate Regression ◽

Arterial Oxygen ◽

High Fidelity ◽

Positive End Expiratory Pressure ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Fraction Of Inspired Oxygen ◽

Inspired Oxygen ◽

Ventilated Patients

The transition from control modes to spontaneous modes is ubiquitous for mechanically ventilated patients yet there is little data describing the changes and patterns that occur to breathing during this transition for patients on ECMO. We identified high fidelity data among a diverse cohort of 419 mechanically ventilated patients on ECMO. We examined every ventilator change, describing the differences in >30,000 sets of original ventilator observations, focused around the time of transition from control modes to spontaneous modes. We performed multivariate regression with mixed effects, clustered by patient, to examine changes in ventilator characteristics within patients, including a subset among patients with low compliance (<30 milliliters (mL)/centimeters water (cmH2O)). We found that during the transition to spontaneous modes among patients with low compliance, patients exhibited greater tidal volumes (471 mL (364,585) vs. 425 mL (320,527); p < 0.0001), higher respiratory rate (23 breaths per minute (bpm) (18,28) vs. 18 bpm (14,23); p = 0.003), greater mechanical power (elastic component) (0.08 mL/(cmH2O × minute) (0.05,0.12) vs. 0.05 mL/(cmH2O × minute) (0.02,0.09); p < 0.0001) (range 0 to 1.4), and lower positive end expiratory pressure (PEEP) (6 cmH2O (5,8) vs. 10 cmH2O (8,11); p < 0.0001). For patients on control modes, the combination of increased tidal volume and increased respiratory rate was temporally associated with significantly low partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) ratio (p < 0.0001). These changes in ventilator parameters warrant prospective study, as they may be associated with worsened lung injury.

Download Full-text

Association of ROX Index with Mechanical Ventilator Use in Sepsis Patients in the Emergency Department

Journal of Clinical Medicine ◽

10.3390/jcm11020342 ◽

2022 ◽

Vol 11 (2) ◽

pp. 342

Author(s):

Sejoong Ahn ◽

Jonghak Park ◽

Juhyun Song ◽

Jooyeong Kim ◽

Hanjin Cho ◽

...

Keyword(s):

Respiratory Rate ◽

Operating Characteristic ◽

Hazard Ratio ◽

Adjusted Hazard Ratio ◽

Tissue Oxygen Saturation ◽

Mechanical Ventilator ◽

Tissue Oxygen ◽

Failure Assessment ◽

Fraction Of Inspired Oxygen ◽

Inspired Oxygen

Detecting sepsis patients who are at a high-risk of mechanical ventilation is important in emergency departments (ED). The respiratory rate oxygenation (ROX) index is the ratio of tissue oxygen saturation/fraction of inspired oxygen to the respiratory rate. This study aimed to investigate whether the ROX index could predict mechanical ventilator use in sepsis patients in an ED. This retrospective observational study included quick sequential organ failure assessment (qSOFA) ≥ 2 sepsis patients that presented to the ED between September 2019 and April 2020. The ROX and ROX-heart rate (HR) indices were significantly lower in patients with mechanical ventilator use within 24 h than in those without the use of a mechanical ventilator (4.0 [3.2–5.4] vs. 10.0 [5.9–15.2], p < 0.001 and 3.9 [2.7–5.8] vs. 10.1 [5.4–16.3], p < 0.001, respectively). The area under the receiver operating characteristic (ROC) curve of the ROX and ROX-HR indices were 0.854 and 0.816 (both p < 0.001). The ROX and ROX-HR indices were independently associated with mechanical ventilator use within 24 h (adjusted hazard ratio = 0.78, 95% CI: 0.68–0.90, p < 0.001 and adjusted hazard ratio = 0.87, 95% CI 0.79–0.96, p = 0.004, respectively). The 28-day mortality was higher in the low ROX and low ROX-HR groups. The ROX and ROX-HR indices were associated with mechanical ventilator use within 24 h in qSOFA ≥ 2 patients in the ED.

Download Full-text

Recommendations for Mechanical Ventilation during Donor Care

Progress in Transplantation ◽

10.1177/152692480001000107 ◽

2000 ◽

Vol 10 (1) ◽

pp. 33-40 ◽

Cited By ~ 16

Author(s):

David J. Powner ◽

Joseph M. Darby ◽

Susan A. Stuart

Keyword(s):

Carbon Dioxide ◽

Mechanical Ventilation ◽

Cardiac Output ◽

Oxygen Uptake ◽

Tidal Volume ◽

Organ Procurement ◽

Mechanical Ventilator ◽

Positive End Expiratory Pressure ◽

Fraction Of Inspired Oxygen ◽

Inspired Oxygen

The organ procurement coordinator usually directs adjustments to the mechanical ventilator during donor care. It is often difficult to achieve optimal oxygen uptake and carbon dioxide removal while avoiding barotrauma or undesirable effects on the cardiac output. Interrelationships among a variety of ventilator parameters must be understood in order to achieve the desired goal of providing the best organs possible. These recommendations review the key ventilator parameters of tidal volume; positive end-expiratory pressure; auto–positive end-expiratory pressure; fraction of inspired oxygen; and flowrate and frequency and their interactions in controlling peak, plateau, and mean and end-expiratory airway pressures.

Download Full-text

Data automated bag breathing unit for COVID-19 ventilator shortages

Intensive Care Medicine Experimental ◽

10.1186/s40635-021-00419-2 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Aleksandra B. Gruslova ◽

Nitesh Katta ◽

Andrew G. Cabe ◽

Scott F. Jenney ◽

Jonathan W. Valvano ◽

...

Keyword(s):

Respiratory Failure ◽

Tidal Volume ◽

Respiratory Rate ◽

Mechanical Test ◽

Low Cost ◽

Lung Model ◽

Oxygen Flow ◽

Normal Lung ◽

Arterial Blood ◽

Bench Testing

Abstract 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.

Download Full-text

Automated Bag Breathing Unit for COVID-19 Ventilator Shortages

10.21203/rs.3.rs-488517/v1 ◽

2021 ◽

Author(s):

Aleksandra Gruslova ◽

Nitesh Katta ◽

Andrew G Cabe ◽

Scott F Jenney ◽

Jonathan W Valvano ◽

...

Keyword(s):

Respiratory Failure ◽

Tidal Volume ◽

Respiratory Rate ◽

Mechanical Test ◽

Low Cost ◽

Lung Model ◽

Oxygen Flow ◽

Normal Lung ◽

Arterial Blood ◽

Bench Testing

Abstract 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 sec), 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 4-16 L/min using a fixed oxygen flow source of 5 L/min. ABBU was tested in Berkshire pigs (n=6, weight of 112±5.8 lb) 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.

Download Full-text

Prospective Randomized Double-Blind Study Comparing l-Epinephrine and Racemic Epinephrine Aerosols in the Treatment of Laryngotracheitis (Croup)

PEDIATRICS ◽

10.1542/peds.89.2.302 ◽

1992 ◽

Vol 89 (2) ◽

pp. 302-306

Author(s):

Yeheskel Waisman ◽

Bruce L. Klein ◽

Douglas A. Boenning ◽

Grace M. Young ◽

James M. Chamberlain ◽

...

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Adverse Effects ◽

Respiratory Rate ◽

Double Blind Study ◽

Double Blind ◽

Treatment Groups ◽

Fraction Of Inspired Oxygen ◽

To Receive ◽

Inspired Oxygen

Aerosolized racemic epinephrine, but not l-epinephrine, is commonly used in treating croup. The efficacy and adverse effects of nebulized racemic and l-epinephrine in the treatment of laryngotracheitis were compared. Children 6 months to 6 years of age with a croup score of 6 or above were assigned in a randomized double-blind fashion to receive either racemic (n = 16) or l-epinephrine (n = 15) aerosols. Croup score, heart rate, blood pressure, respiratory rate, fraction of inspired oxygen, and oxygen saturation were recorded before treatment and at 5, 15, 30, 60, 90, and 120 minutes after the aerosol. Patients in both groups showed significant transient reduction of the croup score and respiratory rate following the aerosol (P < .001), but there were no differences between treatment groups when croup score, heart rate, blood pressure, and respiratory rate were assessed over time. It is concluded that l-epinephrine is at least as effective as racemic epinephrine in the treatment of laryngotracheitis and does not carry the risk of additional adverse effects. l-Epinephrine is also more readily available worldwide, is less expensive, and can be recommended for this purpose.

Download Full-text

Pronation Technique in ARDS Patients

ABOUTOPEN ◽

10.33393/abtpn.2020.2159 ◽

2020 ◽

Vol 7 (1) ◽

pp. 21-23

Author(s):

Raffaele Di Fenza ◽

Hedwige Gay ◽

Martina Favarato ◽

Isabella Fontana ◽

Roberto Fumagalli

Keyword(s):

Intensive Care ◽

Intensive Care Units ◽

Distress Syndrome ◽

Daily Practice ◽

Volume Distribution ◽

Intensive Care Unit Staff ◽

Safe Technique ◽

Fraction Of Inspired Oxygen ◽

And Diffusion ◽

Inspired Oxygen

In severe acute respiratory distress syndrome (ARDS), characterized by the ratio of arterial partial pressure of oxygen over fraction of inspired oxygen (P/F) less than 150 mm Hg, pronation cycles are the only intervention that showed improved survival, in combination with protective ventilation. The physiological advantages of performing pronation cycles, such as the improvement of oxygenation, better tidal volume distribution with increased involvement of dorsal regions, and easier drainage of secretions, overcome the possible complications, that is, endotracheal tube occlusion or misplacement, pressure ulcers, and brachial plexus injury. However, the incidence of complications is dramatically lower in intensive care units with expertise, adopting prone positioning in daily practice. In this video we are proposing step by step an easy and ergonomic technique to perform pronation maneuvers in patients with severe ARDS. Recent literature suggests that a high percentage of these patients are treated without undergoing pronation cycles. The main purpose of this video is to help increase the number of intensive care units worldwide commonly performing pronation cycles in patients that have indications to be pronated, in order to decrease healthcare burden and costs directly caused by ARDS. Proper intensive care unit staff training is fundamental in minimizing the risks associated with the maneuver for both patients and operators; and diffusion of a safe technique encouraging the operators is the second main purpose of this video.

Download Full-text