Evaluation of a Rebreathing System for Use with Portable Mechanical Ventilators.

INTRODUCTION: Maximizing the capabilities of available lowflow oxygen is key to providing adequate oxygen to prevent/treat hypoxemia and conserve oxygen. We designed a closed-circuit system that allows rebreathing of gases while scrubbing carbon dioxide (CO2) in conjunction with portable mechanical ventilators in a bench model. METHODS: We evaluated the system using two portable mechanical ventilators currently deployed by the Department of Defense-Zoll 731 and AutoMedx SAVe II-over a range of ventilator settings and lung models, using 1 and 3L/min low-flow oxygen into a reservoir bag. We measured peak inspired oxygen concentration (FiO2), CO2-absorbent life, gas temperature and humidity, and the effect of airway suctioning and ventilator disconnection on FiO2 on ground and at altitude. RESULTS: FiO2 was =0.9 across all ventilator settings and altitudes using both oxygen flows. CO2-absorbent life was >7 hours. Airway humidity range was 87%-97%. Mean airway temperature was 25.4°C (SD 0.5°C). Ten-second suctioning reduced FiO2 22%-48%. Thirtysecond ventilator disconnect reduced FiO2 29%-63% depending on oxygen flow used. CONCLUSION: Use of a rebreathing system with mechanical ventilation has the potential for oxygen conservation but requires diligent monitoring of inspired FiO2 and CO2 to avoid negative consequences.

Just Say NO: Inhaled Nitric Oxide Effect on Respiratory Parameters Following Traumatic Brain Injury in Humans and a Porcine Model.

INTRODUCTION: The mechanism of post-traumatic brain injury (TBI) hypoxemia involves ventilation/perfusion mismatch and loss of pulmonary hypoxic vasoconstriction. Inhaled nitric oxide (iNO) has been studied as an adjunct treatment to avoid the use of high positive end-expiratory pressure and inspired oxygen in treatment-refractory hypoxia. We hypothesized that iNO treatment following TBI would improve systemic and cerebral oxygenation via improved matching of pulmonary perfusion and ventilation. METHODS: Thirteen human patients with isolated TBI were enrolled and randomized to receive either placebo or iNO with measured outcomes including pulmonary parameters, blood gas data, and intracranial pressure (ICP) /perfusion. To complement this study, a porcine model of TBI (including 10 swine) was utilized with measured outcomes of brain tissue blood flow and oxygenation, ventilator parameters, and blood gas data both after administration and following drug removal and clearance. RESULTS: There were no clinically significant changes in pulmonary parameters in either the human or porcine arm following administration of iNO when compared to either the placebo group (human arm) or the internal control (porcine arm). Analysis of pooled human data demonstrated the preservation of alveolar recruitment in TBI patients. There were no clinically significant changes in human ICP or cerebral perfusion pressure following iNO administration compared to controls. CONCLUSIONS: iNO had no significant effect on clinically relevant pulmonary parameters or ICPs following TBI in both human patients and a porcine model. The pressure-based recruitment of the human lungs following TBI was preserved. Further investigation will be needed to determine the degree of utility of iNO in the setting of hypoxia after polytrauma.

The Reviewer Academy of the Society of Critical Care Medicine: Key Principles and Strategic Plan.

The Society of Critical Care Medicine (SCCM) Reviewer Academy seeks to train and establish a community of trusted, reliable, and skilled peer reviewers with diverse backgrounds and interests to promote high-quality reviews for each of the SCCM journals. Goals of the Academy include building accessible resources to highlight qualities of excellent manuscript reviews; educating and mentoring a diverse group of healthcare professionals; and establishing and upholding standards for insightful and informative reviews. This manuscript will map the mission of the Reviewer Academy with a succinct summary of the importance of peer review, process of reviewing a manuscript, and the expected ethical standards of reviewers. We will equip readers to target concise, thoughtful feedback as peer reviewers, advance their understanding of the editorial process and inspire readers to integrate medical journalism into diverse professional careers.

Reporting Standards for Diagnostic Testing: Guidance for Authors From Editors of Respiratory, Sleep, and Critical Care Journals.

Diagnostic testing is fundamental to medicine. However, studies of diagnostic testing in respiratory medicine vary significantly in terms of their methodology, definitions, and reporting of results. This has led to often conflicting or ambiguous results. To address this issue, a group of 20 respiratory journal editors worked to develop reporting standards for studies of diagnostic testing based on a rigorous methodology to guide authors, peer reviewers, and researchers when conducting studies of diagnostic testing in respiratory medicine. Four key areas are covered, including defining the reference standard of truth, measures of dichotomous test performance when used for dichotomous outcomes, measures of multichotomous test performance for dichotomous outcomes, and what constitutes a useful definition of diagnostic yield. The importance of using contingency tables for reporting results is addressed with examples from the literature. A practical checklist is provided as well for reporting studies of diagnostic testing.

Accuracy of Multiple Pulse Oximeters in Stable Critically Ill Patients.

BACKGROUND: An accurate SpO2 value is critical in order to optimally titrate oxygen delivery to patients and to follow oxygenation guidelines. Limited prospective data exist on real-world performance of pulse oximeters in critically ill patients. The objective of this study was to assess accuracy and bias of the SpO2 values measured by several oximeters in hospitalized subjects. METHODS: We included stable adults in the ICU with an arterial catheter in place. Main exclusion criteria were poor SpO2 signal and SpO2 > 96%. In each subject, we simultaneously evaluated 4 oximeters: Nonin (Plymouth, Minnesota) embedded in the FreeO2 device (OxyNov, Québec City, Québec, Canada), Masimo (Radical-7, Masimo, Irvine, California), Philips (FAST, Philips, Amsterdam, the Netherlands), and Nellcor (N-600, Medtronic, Minneapolis, Minnesota). Arterial blood gases were drawn and simultaneously each oximeters' SpO2 values were collected. SpO2 values were compared to the reference (arterial oxygen saturation [SaO2 ] value) to determine bias and accuracy. The ability for oximeters to detect hypoxemia and the impact of oximeters on oxygen titration were evaluated. RESULTS: We included 193 subjects (153 male, mean age 66 y) in whom 211 sets of measurements were performed. The skin pigmentation evaluated by Fitzpatrick scale showed 96.2% of subjects were light skin (types 1 and 2). One oximeter overestimated SaO2 (Philips, +0.9%), whereas the 3 others underestimated SaO2 (Nonin -3.1%, Nellcor -0.3%, Masimo -0.2%). SaO2 was underestimated with Nonin oximeter in 91.3% of the cases, whereas it was overestimated in 55.2% of the cases with Philips oximeter. Moderate hypoxemia (SaO2 86-90% or PaO2 55-60 mm Hg) was detected in 92, 33, 42, and 11% of the cases with Nonin, Nellcor, Masimo, and Philips, respectively. CONCLUSIONS: We found significant bias and moderate accuracy between the tested oximeters and the arterial blood gases in the studied population. These discrepancies may have important clinical impact on the detection of hypoxemia and management of oxygen therapy.

COVID-19 Lessons Learned: Response to the Anticipated Ventilator Shortage.

Early in the COVID-19 pandemic predictions of a worldwide ventilator shortage prompted a worldwide search for solutions. The impetus for the scramble for ventilators was spurred on by inaccurate and often unrealistic predictions of ventilator requirements. Initial efforts looked simply at acquiring as many ventilators as possible from national and international sources. Ventilators from the Strategic National Stockpile were distributed to early hotspots in the Northeast and Northwest United States. In a triumph of emotion over logic, well-intended experts from other industries turned their time, talent, and treasure toward making a ventilator for the first time. Interest in shared ventilation (more than one patient per ventilator) was ignited by an ill-advised video on social media that ignored the principles of gas delivery in deference to social media notoriety. With shared ventilation, a number of groups mistook a physiologic problem for a plumbing problem. The United States government invoked the Defense Production Act to push automotive manufacturers to partner with existing ventilator manufacturers to speed production. The FDA granted emergency use authorization for "splitters" to allow shared ventilation as well as for ventilators and ancillary equipment. Rationing of ventilators was discussed in the lay press and medical literature but was never necessary in the US. Finally, planners realized that staff with expertise in providing mechanical ventilation were the most important shortage. Over 200,000 ventilators were purchased by the United States government, states, cities, health systems, and individuals. Most had little value in caring for patients with COVID-19 ARDS. This paper attempts to look at where miscalculations were made, with an eye toward what we can do better in the future.

Shortages and Vulnerabilities of Hospital Oxygen Systems.

The COVID-19 pandemic has inundated hospitals with patients suffering from profound hypoxemia and placed a strain on health care systems around the world. Shortages of personnel, drugs, ventilators, and beds were predicted and, in many cases, came to fruition. As the pandemic wore on, there have been reports of impacts on hospital medical gas supply systems. Oxygen in particular has been a concern for hospitals in terms of supply and distribution. This article outlines procedures for estimating medical gas flow limitations within health care organizations and also methods for estimating gas consumption.

Respiratory Drive, Dyspnea, and Silent Hypoxemia: A Physiological Review in the Context of COVID-19.

Infection with SARS-CoV-2 in select individuals results in viral sepsis, pneumonia, and hypoxemic respiratory failure, collectively known as COVID-19. In the early months of the pandemic, the combination of novel disease presentation, enormous surges of critically ill patients, and severity of illness lent to early observations and pronouncements regarding COVID-19 that could not be scientifically validated owing to crisis circumstances. One of these was a phenomenon referred to as "happy hypoxia." Widely discussed in the lay press, it was thought to represent a novel and perplexing phenomenon: severe hypoxemia coupled with the absence of respiratory distress and dyspnea. Silent hypoxemia is the preferred term describing an apparent lack of distress in the presence of hypoxemia. However, the phenomenon is well known among respiratory physiologists as hypoxic ventilatory decline. Silent hypoxemia can be explained by physiologic mechanisms governing the control of breathing, breathing perception, and cardiovascular compensation. This narrative review examines silent hypoxemia during COVID-19 as well as hypotheses that viral infection of the central and peripheral nervous system may be implicated. Moreover, the credulous embrace of happy hypoxia and the novel hypotheses proposed to explain it has exposed significant misunderstandings among clinicians regarding the physiologic mechanisms governing both the control of breathing and the modulation of breathing sensations. Therefore, a substantial focus of this paper is to provide an in-depth review of these topics.

Strategies to prevent ventilator-associated pneumonia, ventilator-associated events, and nonventilator hospital-acquired pneumonia in acute-care hospitals: 2022 Update.

The purpose of this document is to highlight practical recommendations to assist acute care hospitals to prioritize and implement strategies to prevent ventilator-associated pneumonia (VAP), ventilator-associated events (VAE), and non-ventilator hospital-acquired pneumonia (NV-HAP) in adults, children, and neonates. This document updates the Strategies to Prevent Ventilator-Associated Pneumonia in Acute Care Hospitals published in 2014. This expert guidance document is sponsored by the Society for Healthcare Epidemiology (SHEA), and is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America, the American Hospital Association, the Association for Professionals in Infection Control and Epidemiology, and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise.

Critical Care Nurses' Experiences of Caring for Patients With COVID-19: Results of a Thematic Analysis.

BACKGROUND: The COVID-19 pandemic has challenged health care professionals, especially those working in intensive care units (ICUs). OBJECTIVES: To explore critical care nurses' experiences with and perceptions of the COVID-19 pandemic during the early phases of the pandemic. METHODS: Data were from national surveys conducted during March and April 2020 to assess ICU providers' perceptions of the initial phases of the pandemic. A total of 831 responses from nurses to open-ended questions were examined by using thematic analysis. The questions assessed potentially limited resources in the ICU, adequacy of staffing, and measures used to reduce the possibility of spreading COVID-19 to family members. RESULTS: Overarching themes concerned access to equipment and preventive measures taken to reduce exposure to the virus. These themes included "sheltering the patient when I don't have enough" and "protecting those I love when I am a vector of transmission." Subthemes for the first overarching theme included not having enough personal protective equipment, not enough staff and not enough properly trained staff, and not enough institutional support. Subthemes for the second overarching theme included "isolating myself from everyone I care about" and "isolating everything I touch from everyone I care about." CONCLUSIONS: This thematic analysis identified several concerns of ICU nurses related to caring for patients in the initial phases of the COVID-19 pandemic. Ensuring adequate supplies, staffing, and administrative and emotional support are provided to frontline health care providers during the ongoing pandemic remains essential.

Optimal NIV Medicare Access Promotion: Patients With COPD: A Technical Expert Panel Report From the American College of Chest Physicians, the American Association for Respiratory Care, the American Academy of Sleep Medicine, and the American Thoracic Society.

This document summarizes the work of the COPD Technical Expert Panel working group. For patients with COPD, the most pressing current coverage barriers identified were onerous diagnostic requirements focused on oxygenation (rather than ventilation) and difficulty obtaining bilevel devices with backup rate capabilities. Because of these difficulties, many patients with COPD were instead sometimes prescribed home mechanical ventilators. Critical evidence supports changes to current policies, including randomized controlled trial evidence suggesting a mortality benefit from bilevel positive airway pressure with backup rate and updated clinical practice guidelines from the American Thoracic Society as well as the European Respiratory Society. To achieve optimal access to noninvasive ventilation for patients with COPD, we make the following key recommendations: (1) removal of the need for overnight oximetry testing; (2) the ability to initiate therapy using bilevel devices with backup rate capability; and (3) increased duration of time to meet adherence criteria (ie, a second 90-day trial period) in those patients actively engaged in their care. Clear guidelines based on medical necessity are also included for patients who require initiation of or switch to a home mechanical ventilator. Adoption of these proposed recommendations would result in the right device, for the right type of patient with COPD, at the right time. Finally, we emphasize the need for adequate clinical support during initiation and maintenance of home noninvasive ventilation in such patients.