maria madden - Academia.edu (original) (raw)
Papers by maria madden
Respiratory Care, Oct 1, 2019
Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict... more Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict successful extubation and liberation from mechanical ventilation. The original study used a T-piece during a spontaneous breathing trial (SBT) and showed an RSBI less than 105 to be the acceptable parameter for successful extubation. The current standard in most institutions is to perform SBT and measure an RSBI while using the ventilator, typically with Pressure Support (PS) of 5 cm H2O and PEEP of 5 cm H2O. We hypothesized that an SBT using PS of 0 cm H2O, PEEP of 0 cm H2O with automatic tube compensation (ATC) would create a significant difference in the accuracy of using RSBI as a predictor for successful extubation when compared to PS of 5 cm H2O and PEEP of 5 cm H2O. Methods: After IRB approval, we performed a retrospective chart review study of all patients admitted to R Adams Cowley Shock Trauma Center in the Multi-Trauma Critical Care (MTCC) during 2015 that had SBT performed with the two various SBT settings to determine the reintubation rate. Data were also collected on patients that required noninvasive ventilation (NIV) or high flow nasal cannula (HFNC) post-extubation. Results: There were 201 patients extubated that completed an SBT on PS of 5 cm H2O PEEP of 5 cm H2O and 12.56% required re-intubation which wasn’t significant but double the rate of 5.3% of 95 patients that were reintubated when using an SBT of on PS of 0 cm H2O, PEEP of 0 cm H2O, and ATC. Conclusions: The more ventilation support provided during an SBT, the less likely an RSBI
Respiratory Care, Oct 1, 2018
Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered an... more Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered and flow cycled. Spontaneous breaths on PSV are triggered, which alters spontaneous breaths from sinusoidal to decelerating assisted mechanical breaths. Because PSV breaths are assisted, they may be under-compensated or overcompensated for the artificial airway resistance based on the amount of support set at the ventilator. Alternatively, CPAP with the use of automatic tube compensation (ATC) provides dynamic inspiratory flow in proportion to the pressure drop across the artificial airway size (length and diameter). As a result, the sinusoidal flow pattern of spontaneous breathing is preserved with an unassisted breath. Electrical Impedance Tomography (EIT) technology provides non-invasive and radiation-free medical imaging. In addition, EIT provides regional information of changes in ventilation, which could help with gaining information on where a regional distribution of ventilation occurs during spontaneous modes of ventilation such as PSV and CPAP. We chose to use EIT to observe patients in various spontaneous modes. Methods: This observational study, approved by the University of Maryland Institutional Review Board (IRB) enrolled ICU patients receiving mechanical ventilation set in either PSV or CPAP. The PulmoVista 500 EIT device by Draeger Medical (Lubeck, Germany) was used to visualize regional distribution of ventilation. Results: Four patients were observed during PSV that were transitioned to CPAP or proportion pressure support (PPS) per physician orders. After transitioning from an assisted mode (PSV) to an unassisted mode (CPAP or PPS), dorsal and mid-dorsal ventilation was seen to have increased in each patient. The gas distribution to the mid-dorsal and dorsal increased by an average of 9. 25% in all four patients. Two of the patients did see an increase in gas distribution by 13% and two by 4% and 7% within min of transitioning to the unassisted mode of ventilation. Conclusions: This small observational study demonstrated the benefit of preferential volume distribution with unassisted breathing. Further research in comparing assisted versus unassisted ventilation is warranted.
Frontiers in Physiology, Jul 25, 2022
In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge a... more In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): "Scientific orthodoxy kills truth". In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of "lung protective" ventilation. Unfortunately, inadequacies of the current conceptual model-that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the "baby lung"-is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV's clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.
Respiratory Care, Nov 2, 2021
Providing supplemental oxygen to hospitalized adults is a frequent practice and can be administer... more Providing supplemental oxygen to hospitalized adults is a frequent practice and can be administered via a variety of devices. Oxygen therapy has evolved over the years, and clinicians should follow evidence-based practices to provide maximum benefit and avoid harm. This systematic review and subsequent clinical practice guidelines were developed to answer questions about oxygenation targets, monitoring, early initiation of high-flow oxygen (HFO), benefits of HFO compared to conventional oxygen therapy, and humidification of supplemental oxygen. Using a modification of the RAND/UCLA Appropriateness Method, 7 recommendations were developed to guide the delivery of supplemental oxygen to hospitalized adults: (1) aim for S pO 2 range of 94-98% for most hospitalized patients (88-92% for those with COPD), (2) the same S pO 2 range of 94-98% for critically ill patients, (3) promote early initiation of HFO, (4) consider HFO to avoid escalation to noninvasive ventilation, (5) consider HFO immediately postextubation to avoid re-intubation, (6) either HFO or conventional oxygen therapy may be used with patients who are immunocompromised, and (7) consider humidification for supplemental oxygen when flows > 4 L/min are used.
Annals of Intensive Care, Jan 6, 2020
Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximatel... more Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximately 39%. One of the only treatments is supportive: mechanical ventilation. However, improperly set mechanical ventilation can further increase the risk of death in patients with ARDS. Recent studies suggest that ventilation-induced lung injury (VILI) is caused by exaggerated regional lung strain, particularly in areas of alveolar instability subject to tidal recruitment/ derecruitment and stress-multiplication. Thus, it is reasonable to expect that if a ventilation strategy can maintain stable lung inflation and homogeneity, regional dynamic strain would be reduced and VILI attenuated. A time-controlled adaptive ventilation (TCAV) method was developed to minimize dynamic alveolar strain by adjusting the delivered breath according to the mechanical characteristics of the lung. The goal of this review is to describe how the TCAV method impacts pathophysiology and protects lungs with, or at high risk of, acute lung injury. We present work from our group and others that identifies novel mechanisms of VILI in the alveolar microenvironment and demonstrates that the TCAV method can reduce VILI in translational animal ARDS models and mortality in surgical/trauma patients. Our TCAV method utilizes the airway pressure release ventilation (APRV) mode and is based on opening and collapsing time constants, which reflect the viscoelastic properties of the terminal airspaces. Time-controlled adaptive ventilation uses inspiratory and expiratory time to (1) gradually "nudge" alveoli and alveolar ducts open with an extended inspiratory duration and (2) prevent alveolar collapse using a brief (sub-second) expiratory duration that does not allow time for alveolar collapse. The new paradigm in TCAV is configuring each breath guided by the previous one, which achieves real-time titration of ventilator settings and minimizes instability induced tissue damage. This novel methodology changes the current approach to mechanical ventilation, from arbitrary to personalized and adaptive. The outcome of this approach is an open and stable lung with reduced regional strain and greater lung protection.
Critical Care Medicine, Dec 1, 2016
Objective In addition to a clinical exam, apnea testing is critical for confirmation of cessation... more Objective In addition to a clinical exam, apnea testing is critical for confirmation of cessation of neurologic function [brain death]. However, traditional apnea exams place clinicians in a difficult position where maintaining oxygenation and hemodynamic stability in patients who are typically unstable have been associated with adverse events such as hypoxia, hypotension, pneumothorax, arrhythmias, derecruitment, and even cardiac death. The purpose of this retrospective case series was to assess whether apnea testing using carbogen was a safe, reliable alternative. Methods A retrospective chart review was conducted of brain death exams and apnea tests performed for brain death determination in a university hospital and trauma center. Apnea tests were completed either using the “Traditional Method” (TM) by removing the patient from the ventilator and assessed for presence of spontaneous breathing by movement of the chest wall or the “Carbogen Method” (CM) where patients remain on th...
Frontiers in Physiology
In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge a... more In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): “Scientific orthodoxy kills truth”. In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of “lung protective” ventilation. Unfortunately, inadequacies of the current conceptual model–that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the “baby lung” - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controve...
Respiratory Care, Oct 1, 2018
Critical Care Medicine, 2016
Respiratory Care, 2019
Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict... more Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict successful extubation and liberation from mechanical ventilation. The original study used a T-piece during a spontaneous breathing trial (SBT) and showed an RSBI less than 105 to be the acceptable parameter for successful extubation. The current standard in most institutions is to perform SBT and measure an RSBI while using the ventilator, typically with Pressure Support (PS) of 5 cm H2O and PEEP of 5 cm H2O. We hypothesized that an SBT using PS of 0 cm H2O, PEEP of 0 cm H2O with automatic tube compensation (ATC) would create a significant difference in the accuracy of using RSBI as a predictor for successful extubation when compared to PS of 5 cm H2O and PEEP of 5 cm H2O. Methods: After IRB approval, we performed a retrospective chart review study of all patients admitted to R Adams Cowley Shock Trauma Center in the Multi-Trauma Critical Care (MTCC) during 2015 that had SBT performed w...
Respiratory Care, 2018
Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered an... more Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered and flow cycled. Spontaneous breaths on PSV are triggered, which alters spontaneous breaths from sinusoidal to decelerating assisted mechanical breaths. Because PSV breaths are assisted, they may be under-compensated or overcompensated for the artificial airway resistance based on the amount of support set at the ventilator. Alternatively, CPAP with the use of automatic tube compensation (ATC) provides dynamic inspiratory flow in proportion to the pressure drop across the artificial airway size (length and diameter). As a result, the sinusoidal flow pattern of spontaneous breathing is preserved with an unassisted breath. Electrical Impedance Tomography (EIT) technology provides non-invasive and radiation-free medical imaging. In addition, EIT provides regional information of changes in ventilation, which could help with gaining information on where a regional distribution of ventilation oc...
Background: The world is in the midst of the COVID-19 viral pandemic and the number of patients r... more Background: The world is in the midst of the COVID-19 viral pandemic and the number of patients requiring mechanical ventilation may exceed the number of ventilators available. New information is being sought on the feasibility of using one ventilator on multiple patients should the need arise. In this study, we hypothesized that two rabbits could be simultaneously mechanically ventilated using a simple, readily available, dual circuit. Methods: Two pairs of New Zealand White rabbits (n=4) were anesthetized and hooked up to a simple dual circuit and ventilated in the Airway Pressure Release Ventilation mode. Arterial and venous lines were placed for arterial blood gases, hemodynamic monitoring and fluid administration. Following one hour of ventilation, a surfactant washout was performed and mechanical ventilation resumed. Animals were euthanized after an additional one hour of ventilation. Results: Both Pairs of rabbits had a similar pre-injury PaO2/FiO2 ratio. Following injury, al...
Frontiers in Physiology, 2020
Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serio... more Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serious medical problem, with one of the only treatments being supportive care in the form of mechanical ventilation. It is very difficult, however, to mechanically ventilate the heterogeneously damaged lung without causing secondary ventilatorinduced lung injury (VILI). The acutely injured lung becomes time and pressure dependent, meaning that it takes more time and pressure to open the lung, and it recollapses more quickly and at higher pressure. Current protective ventilation strategies, ARDSnet low tidal volume (LVt) and the open lung approach (OLA), have been unsuccessful at further reducing ARDS mortality. We postulate that this is because the LVt strategy is constrained to ventilating a lung with a heterogeneous mix of normal and focalized injured tissue, and the OLA, although designed to fully open and stabilize the lung, is often unsuccessful at doing so. In this review we analyzed the pathophysiology of ARDS that renders the lung susceptible to VILI. We also analyzed the alterations in alveolar and alveolar duct mechanics that occur in the acutely injured lung and discussed how these alterations are a key mechanism driving VILI. Our analysis suggests that the time component of each mechanical breath, at both inspiration and expiration, is critical to normalize alveolar mechanics and protect the lung from VILI. Animal studies and a meta-analysis have suggested that the time-controlled adaptive ventilation (TCAV) method, using the airway pressure release ventilation mode, eliminates the constraints of ventilating a lung with heterogeneous injury, since it is highly effective at opening and stabilizing the time-and pressure-dependent lung. In animal studies it has been shown that by "casting open" the acutely injured lung with TCAV we can (1) reestablish normal expiratory lung volume as assessed by direct observation of subpleural alveoli; (2) return normal parenchymal microanatomical structural support, known as alveolar interdependence and parenchymal tethering, as assessed by morphometric analysis of lung histology; (3) facilitate regeneration of normal surfactant function measured as increases in surfactant proteins A and B; and (4) significantly increase lung compliance, which reduces the pathologic impact of driving pressure and mechanical power at any given tidal volume.
Annals of Intensive Care, 2020
Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximatel... more Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximately 39%. One of the only treatments is supportive: mechanical ventilation. However, improperly set mechanical ventilation can further increase the risk of death in patients with ARDS. Recent studies suggest that ventilation-induced lung injury (VILI) is caused by exaggerated regional lung strain, particularly in areas of alveolar instability subject to tidal recruitment/derecruitment and stress-multiplication. Thus, it is reasonable to expect that if a ventilation strategy can maintain stable lung inflation and homogeneity, regional dynamic strain would be reduced and VILI attenuated. A time-controlled adaptive ventilation (TCAV) method was developed to minimize dynamic alveolar strain by adjusting the delivered breath according to the mechanical characteristics of the lung. The goal of this review is to describe how the TCAV method impacts pathophysiology and protects lungs with, or at hi...
Journal of Trauma and Acute Care Surgery, 2018
The acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the curren... more The acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the current treatment being supportive in the form of mechanical ventilation. However, mechanical ventilation can be a double-edged sword; if set properly, it can significantly reduce ARDS associated mortality but if set improperly it can have unintended consequences causing a secondary ventilator induced lung injury (VILI). The hallmark of ARDS pathology is a heterogeneous lung injury, which predisposes the lung to a secondary VILI. The current standard of care approach is to wait until ARDS is well established and then apply a low tidal volume (LVt) strategy to avoid over-distending the remaining normal lung. However, even with the use of LVt strategy, the mortality of ARDS remains unacceptably high at ~40%. In this review, we analyze the lung pathophysiology associated with ARDS that renders the lung highly vulnerable to a secondary VILI. The current standard of care LVt strategy is critiqued as well as new strategies used in combination with LVt to protect the lung. Using the current understanding of alveolar mechanics (i.e. the dynamic change in alveolar size and shape with tidal ventilation) we provide a rationale for why the current protective ventilation strategies have not further reduced ARDS mortality. New strategies of protective ventilation based on dynamic physiology in the microenvironment (i.e. alveoli and alveolar ducts) are discussed. Current evidence suggests that alveolar inflation and deflation is viscoelastic in nature, with a fast and slow phase in both alveolar
ackground: Reusable respirators are an important alternative source of respiratory protection in ... more ackground: Reusable respirators are an important alternative source of respiratory protection in healthcare to alleviate N95 supply shortages faced during surge demand. These respirators must be cleaned and disinfected after use to assure safety for reuse. Objective: This study aimed to evaluate whether use of conveniently available hospital chemical disinfectants alone removes influenza virus and facial contaminants similarly to use of a soap and waterbased cleaning regimen along with disinfectant. Methods: CleanSpace® Halo reusable respirators were contaminated with simulated facial oils and influenza A virus via fine mist spray. Facial contamination was verified by use of fluorescent lotion. Half of the respirators were processed by cleaning in soap and water followed by wiping with a standard hospital chemical disinfectant; the other half were only wiped with chemical disinfectants. Disinfectants included: 70% isopropyl alcohol, 0.5% hydrogen peroxide, 0.55% quaternary ammonium ...
Critical care (London, England), Jan 24, 2018
The pathophysiology of acute respiratory distress syndrome (ARDS) results in heterogeneous lung c... more The pathophysiology of acute respiratory distress syndrome (ARDS) results in heterogeneous lung collapse, edema-flooded airways and unstable alveoli. These pathologic alterations in alveolar mechanics (i.e. dynamic change in alveolar size and shape with each breath) predispose the lung to secondary ventilator-induced lung injury (VILI). It is our viewpoint that the acutely injured lung can be recruited and stabilized with a mechanical breath until it heals, much like casting a broken bone until it mends. If the lung can be "casted" with a mechanical breath, VILI could be prevented and ARDS incidence significantly reduced.
Respiratory Care, Oct 1, 2019
Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict... more Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict successful extubation and liberation from mechanical ventilation. The original study used a T-piece during a spontaneous breathing trial (SBT) and showed an RSBI less than 105 to be the acceptable parameter for successful extubation. The current standard in most institutions is to perform SBT and measure an RSBI while using the ventilator, typically with Pressure Support (PS) of 5 cm H2O and PEEP of 5 cm H2O. We hypothesized that an SBT using PS of 0 cm H2O, PEEP of 0 cm H2O with automatic tube compensation (ATC) would create a significant difference in the accuracy of using RSBI as a predictor for successful extubation when compared to PS of 5 cm H2O and PEEP of 5 cm H2O. Methods: After IRB approval, we performed a retrospective chart review study of all patients admitted to R Adams Cowley Shock Trauma Center in the Multi-Trauma Critical Care (MTCC) during 2015 that had SBT performed with the two various SBT settings to determine the reintubation rate. Data were also collected on patients that required noninvasive ventilation (NIV) or high flow nasal cannula (HFNC) post-extubation. Results: There were 201 patients extubated that completed an SBT on PS of 5 cm H2O PEEP of 5 cm H2O and 12.56% required re-intubation which wasn’t significant but double the rate of 5.3% of 95 patients that were reintubated when using an SBT of on PS of 0 cm H2O, PEEP of 0 cm H2O, and ATC. Conclusions: The more ventilation support provided during an SBT, the less likely an RSBI
Respiratory Care, Oct 1, 2018
Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered an... more Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered and flow cycled. Spontaneous breaths on PSV are triggered, which alters spontaneous breaths from sinusoidal to decelerating assisted mechanical breaths. Because PSV breaths are assisted, they may be under-compensated or overcompensated for the artificial airway resistance based on the amount of support set at the ventilator. Alternatively, CPAP with the use of automatic tube compensation (ATC) provides dynamic inspiratory flow in proportion to the pressure drop across the artificial airway size (length and diameter). As a result, the sinusoidal flow pattern of spontaneous breathing is preserved with an unassisted breath. Electrical Impedance Tomography (EIT) technology provides non-invasive and radiation-free medical imaging. In addition, EIT provides regional information of changes in ventilation, which could help with gaining information on where a regional distribution of ventilation occurs during spontaneous modes of ventilation such as PSV and CPAP. We chose to use EIT to observe patients in various spontaneous modes. Methods: This observational study, approved by the University of Maryland Institutional Review Board (IRB) enrolled ICU patients receiving mechanical ventilation set in either PSV or CPAP. The PulmoVista 500 EIT device by Draeger Medical (Lubeck, Germany) was used to visualize regional distribution of ventilation. Results: Four patients were observed during PSV that were transitioned to CPAP or proportion pressure support (PPS) per physician orders. After transitioning from an assisted mode (PSV) to an unassisted mode (CPAP or PPS), dorsal and mid-dorsal ventilation was seen to have increased in each patient. The gas distribution to the mid-dorsal and dorsal increased by an average of 9. 25% in all four patients. Two of the patients did see an increase in gas distribution by 13% and two by 4% and 7% within min of transitioning to the unassisted mode of ventilation. Conclusions: This small observational study demonstrated the benefit of preferential volume distribution with unassisted breathing. Further research in comparing assisted versus unassisted ventilation is warranted.
Frontiers in Physiology, Jul 25, 2022
In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge a... more In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): "Scientific orthodoxy kills truth". In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of "lung protective" ventilation. Unfortunately, inadequacies of the current conceptual model-that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the "baby lung"-is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controversial modes of mechanical ventilation that shows promise in experimental and clinical data. Over the last 3 decades APRV has evolved from a rescue strategy to a preemptive lung injury prevention approach with potential to stabilize the lung and restore alveolar homogeneity. However, several obstacles have so far impeded the evaluation of APRV's clinical efficacy in large, randomized trials. For instance, there is no universally accepted standardized method of setting APRV and thus, it is not established whether its effects on clinical outcomes are due to the ventilator mode per se or the method applied. In addition, one distinctive issue that hinders proper scientific evaluation of APRV is the ubiquitous presence of myths and misconceptions repeatedly presented in the literature. In this review we discuss some of these misleading notions and present data to advance scientific discourse around the uses and misuses of APRV in the current literature.
Respiratory Care, Nov 2, 2021
Providing supplemental oxygen to hospitalized adults is a frequent practice and can be administer... more Providing supplemental oxygen to hospitalized adults is a frequent practice and can be administered via a variety of devices. Oxygen therapy has evolved over the years, and clinicians should follow evidence-based practices to provide maximum benefit and avoid harm. This systematic review and subsequent clinical practice guidelines were developed to answer questions about oxygenation targets, monitoring, early initiation of high-flow oxygen (HFO), benefits of HFO compared to conventional oxygen therapy, and humidification of supplemental oxygen. Using a modification of the RAND/UCLA Appropriateness Method, 7 recommendations were developed to guide the delivery of supplemental oxygen to hospitalized adults: (1) aim for S pO 2 range of 94-98% for most hospitalized patients (88-92% for those with COPD), (2) the same S pO 2 range of 94-98% for critically ill patients, (3) promote early initiation of HFO, (4) consider HFO to avoid escalation to noninvasive ventilation, (5) consider HFO immediately postextubation to avoid re-intubation, (6) either HFO or conventional oxygen therapy may be used with patients who are immunocompromised, and (7) consider humidification for supplemental oxygen when flows > 4 L/min are used.
Annals of Intensive Care, Jan 6, 2020
Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximatel... more Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximately 39%. One of the only treatments is supportive: mechanical ventilation. However, improperly set mechanical ventilation can further increase the risk of death in patients with ARDS. Recent studies suggest that ventilation-induced lung injury (VILI) is caused by exaggerated regional lung strain, particularly in areas of alveolar instability subject to tidal recruitment/ derecruitment and stress-multiplication. Thus, it is reasonable to expect that if a ventilation strategy can maintain stable lung inflation and homogeneity, regional dynamic strain would be reduced and VILI attenuated. A time-controlled adaptive ventilation (TCAV) method was developed to minimize dynamic alveolar strain by adjusting the delivered breath according to the mechanical characteristics of the lung. The goal of this review is to describe how the TCAV method impacts pathophysiology and protects lungs with, or at high risk of, acute lung injury. We present work from our group and others that identifies novel mechanisms of VILI in the alveolar microenvironment and demonstrates that the TCAV method can reduce VILI in translational animal ARDS models and mortality in surgical/trauma patients. Our TCAV method utilizes the airway pressure release ventilation (APRV) mode and is based on opening and collapsing time constants, which reflect the viscoelastic properties of the terminal airspaces. Time-controlled adaptive ventilation uses inspiratory and expiratory time to (1) gradually "nudge" alveoli and alveolar ducts open with an extended inspiratory duration and (2) prevent alveolar collapse using a brief (sub-second) expiratory duration that does not allow time for alveolar collapse. The new paradigm in TCAV is configuring each breath guided by the previous one, which achieves real-time titration of ventilator settings and minimizes instability induced tissue damage. This novel methodology changes the current approach to mechanical ventilation, from arbitrary to personalized and adaptive. The outcome of this approach is an open and stable lung with reduced regional strain and greater lung protection.
Critical Care Medicine, Dec 1, 2016
Objective In addition to a clinical exam, apnea testing is critical for confirmation of cessation... more Objective In addition to a clinical exam, apnea testing is critical for confirmation of cessation of neurologic function [brain death]. However, traditional apnea exams place clinicians in a difficult position where maintaining oxygenation and hemodynamic stability in patients who are typically unstable have been associated with adverse events such as hypoxia, hypotension, pneumothorax, arrhythmias, derecruitment, and even cardiac death. The purpose of this retrospective case series was to assess whether apnea testing using carbogen was a safe, reliable alternative. Methods A retrospective chart review was conducted of brain death exams and apnea tests performed for brain death determination in a university hospital and trauma center. Apnea tests were completed either using the “Traditional Method” (TM) by removing the patient from the ventilator and assessed for presence of spontaneous breathing by movement of the chest wall or the “Carbogen Method” (CM) where patients remain on th...
Frontiers in Physiology
In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge a... more In the pursuit of science, competitive ideas and debate are necessary means to attain knowledge and expose our ignorance. To quote Murray Gell-Mann (1969 Nobel Prize laureate in Physics): “Scientific orthodoxy kills truth”. In mechanical ventilation, the goal is to provide the best approach to support patients with respiratory failure until the underlying disease resolves, while minimizing iatrogenic damage. This compromise characterizes the philosophy behind the concept of “lung protective” ventilation. Unfortunately, inadequacies of the current conceptual model–that focuses exclusively on a nominal value of low tidal volume and promotes shrinking of the “baby lung” - is reflected in the high mortality rate of patients with moderate and severe acute respiratory distress syndrome. These data call for exploration and investigation of competitive models evaluated thoroughly through a scientific process. Airway Pressure Release Ventilation (APRV) is one of the most studied yet controve...
Respiratory Care, Oct 1, 2018
Critical Care Medicine, 2016
Respiratory Care, 2019
Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict... more Background: The rapid shallow breathing index (RSBI) is a measurement that may be used to predict successful extubation and liberation from mechanical ventilation. The original study used a T-piece during a spontaneous breathing trial (SBT) and showed an RSBI less than 105 to be the acceptable parameter for successful extubation. The current standard in most institutions is to perform SBT and measure an RSBI while using the ventilator, typically with Pressure Support (PS) of 5 cm H2O and PEEP of 5 cm H2O. We hypothesized that an SBT using PS of 0 cm H2O, PEEP of 0 cm H2O with automatic tube compensation (ATC) would create a significant difference in the accuracy of using RSBI as a predictor for successful extubation when compared to PS of 5 cm H2O and PEEP of 5 cm H2O. Methods: After IRB approval, we performed a retrospective chart review study of all patients admitted to R Adams Cowley Shock Trauma Center in the Multi-Trauma Critical Care (MTCC) during 2015 that had SBT performed w...
Respiratory Care, 2018
Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered an... more Background: Pressure Support Ventilation (PSV) is a spontaneous mode that is patient triggered and flow cycled. Spontaneous breaths on PSV are triggered, which alters spontaneous breaths from sinusoidal to decelerating assisted mechanical breaths. Because PSV breaths are assisted, they may be under-compensated or overcompensated for the artificial airway resistance based on the amount of support set at the ventilator. Alternatively, CPAP with the use of automatic tube compensation (ATC) provides dynamic inspiratory flow in proportion to the pressure drop across the artificial airway size (length and diameter). As a result, the sinusoidal flow pattern of spontaneous breathing is preserved with an unassisted breath. Electrical Impedance Tomography (EIT) technology provides non-invasive and radiation-free medical imaging. In addition, EIT provides regional information of changes in ventilation, which could help with gaining information on where a regional distribution of ventilation oc...
Background: The world is in the midst of the COVID-19 viral pandemic and the number of patients r... more Background: The world is in the midst of the COVID-19 viral pandemic and the number of patients requiring mechanical ventilation may exceed the number of ventilators available. New information is being sought on the feasibility of using one ventilator on multiple patients should the need arise. In this study, we hypothesized that two rabbits could be simultaneously mechanically ventilated using a simple, readily available, dual circuit. Methods: Two pairs of New Zealand White rabbits (n=4) were anesthetized and hooked up to a simple dual circuit and ventilated in the Airway Pressure Release Ventilation mode. Arterial and venous lines were placed for arterial blood gases, hemodynamic monitoring and fluid administration. Following one hour of ventilation, a surfactant washout was performed and mechanical ventilation resumed. Animals were euthanized after an additional one hour of ventilation. Results: Both Pairs of rabbits had a similar pre-injury PaO2/FiO2 ratio. Following injury, al...
Frontiers in Physiology, 2020
Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serio... more Acute respiratory distress syndrome (ARDS) causes a heterogeneous lung injury and remains a serious medical problem, with one of the only treatments being supportive care in the form of mechanical ventilation. It is very difficult, however, to mechanically ventilate the heterogeneously damaged lung without causing secondary ventilatorinduced lung injury (VILI). The acutely injured lung becomes time and pressure dependent, meaning that it takes more time and pressure to open the lung, and it recollapses more quickly and at higher pressure. Current protective ventilation strategies, ARDSnet low tidal volume (LVt) and the open lung approach (OLA), have been unsuccessful at further reducing ARDS mortality. We postulate that this is because the LVt strategy is constrained to ventilating a lung with a heterogeneous mix of normal and focalized injured tissue, and the OLA, although designed to fully open and stabilize the lung, is often unsuccessful at doing so. In this review we analyzed the pathophysiology of ARDS that renders the lung susceptible to VILI. We also analyzed the alterations in alveolar and alveolar duct mechanics that occur in the acutely injured lung and discussed how these alterations are a key mechanism driving VILI. Our analysis suggests that the time component of each mechanical breath, at both inspiration and expiration, is critical to normalize alveolar mechanics and protect the lung from VILI. Animal studies and a meta-analysis have suggested that the time-controlled adaptive ventilation (TCAV) method, using the airway pressure release ventilation mode, eliminates the constraints of ventilating a lung with heterogeneous injury, since it is highly effective at opening and stabilizing the time-and pressure-dependent lung. In animal studies it has been shown that by "casting open" the acutely injured lung with TCAV we can (1) reestablish normal expiratory lung volume as assessed by direct observation of subpleural alveoli; (2) return normal parenchymal microanatomical structural support, known as alveolar interdependence and parenchymal tethering, as assessed by morphometric analysis of lung histology; (3) facilitate regeneration of normal surfactant function measured as increases in surfactant proteins A and B; and (4) significantly increase lung compliance, which reduces the pathologic impact of driving pressure and mechanical power at any given tidal volume.
Annals of Intensive Care, 2020
Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximatel... more Mortality in acute respiratory distress syndrome (ARDS) remains unacceptably high at approximately 39%. One of the only treatments is supportive: mechanical ventilation. However, improperly set mechanical ventilation can further increase the risk of death in patients with ARDS. Recent studies suggest that ventilation-induced lung injury (VILI) is caused by exaggerated regional lung strain, particularly in areas of alveolar instability subject to tidal recruitment/derecruitment and stress-multiplication. Thus, it is reasonable to expect that if a ventilation strategy can maintain stable lung inflation and homogeneity, regional dynamic strain would be reduced and VILI attenuated. A time-controlled adaptive ventilation (TCAV) method was developed to minimize dynamic alveolar strain by adjusting the delivered breath according to the mechanical characteristics of the lung. The goal of this review is to describe how the TCAV method impacts pathophysiology and protects lungs with, or at hi...
Journal of Trauma and Acute Care Surgery, 2018
The acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the curren... more The acute respiratory distress syndrome (ARDS) remains a serious clinical problem with the current treatment being supportive in the form of mechanical ventilation. However, mechanical ventilation can be a double-edged sword; if set properly, it can significantly reduce ARDS associated mortality but if set improperly it can have unintended consequences causing a secondary ventilator induced lung injury (VILI). The hallmark of ARDS pathology is a heterogeneous lung injury, which predisposes the lung to a secondary VILI. The current standard of care approach is to wait until ARDS is well established and then apply a low tidal volume (LVt) strategy to avoid over-distending the remaining normal lung. However, even with the use of LVt strategy, the mortality of ARDS remains unacceptably high at ~40%. In this review, we analyze the lung pathophysiology associated with ARDS that renders the lung highly vulnerable to a secondary VILI. The current standard of care LVt strategy is critiqued as well as new strategies used in combination with LVt to protect the lung. Using the current understanding of alveolar mechanics (i.e. the dynamic change in alveolar size and shape with tidal ventilation) we provide a rationale for why the current protective ventilation strategies have not further reduced ARDS mortality. New strategies of protective ventilation based on dynamic physiology in the microenvironment (i.e. alveoli and alveolar ducts) are discussed. Current evidence suggests that alveolar inflation and deflation is viscoelastic in nature, with a fast and slow phase in both alveolar
ackground: Reusable respirators are an important alternative source of respiratory protection in ... more ackground: Reusable respirators are an important alternative source of respiratory protection in healthcare to alleviate N95 supply shortages faced during surge demand. These respirators must be cleaned and disinfected after use to assure safety for reuse. Objective: This study aimed to evaluate whether use of conveniently available hospital chemical disinfectants alone removes influenza virus and facial contaminants similarly to use of a soap and waterbased cleaning regimen along with disinfectant. Methods: CleanSpace® Halo reusable respirators were contaminated with simulated facial oils and influenza A virus via fine mist spray. Facial contamination was verified by use of fluorescent lotion. Half of the respirators were processed by cleaning in soap and water followed by wiping with a standard hospital chemical disinfectant; the other half were only wiped with chemical disinfectants. Disinfectants included: 70% isopropyl alcohol, 0.5% hydrogen peroxide, 0.55% quaternary ammonium ...
Critical care (London, England), Jan 24, 2018
The pathophysiology of acute respiratory distress syndrome (ARDS) results in heterogeneous lung c... more The pathophysiology of acute respiratory distress syndrome (ARDS) results in heterogeneous lung collapse, edema-flooded airways and unstable alveoli. These pathologic alterations in alveolar mechanics (i.e. dynamic change in alveolar size and shape with each breath) predispose the lung to secondary ventilator-induced lung injury (VILI). It is our viewpoint that the acutely injured lung can be recruited and stabilized with a mechanical breath until it heals, much like casting a broken bone until it mends. If the lung can be "casted" with a mechanical breath, VILI could be prevented and ARDS incidence significantly reduced.