Basing Respiratory Management of COVID-19 on Physiological Principles

Current directions, conceptions and viewpoints on 2019-nCoV (Review)

On December 31, 2019, the first case of a novel coronavirus infection was reported in Wuhan, China. The ongoing outbreak of the 2019 novel coronavirus (2019-nCoV) has caused immense global concern. According to the recommendations of the International Health Regulations Emergency Committee and the facts and cases that 215 other countries have also reported to date, the World Health Organization Director-General announced that the outbreak of 2019-nCoV constitutes a public health emergency of international concern and a severe threat to the human health worldwide. To date, the prevalence of the virus has continued in waves and is increasing globally. The present review briefly introduces the epidemiology of 2019-nCoV, as well as viral structural characteristics, and receptors and cells that may act after entering the body, laboratory examinations, imaging and pathological features, clinical manifestations, complications, treatment and management.

Use of Helmet-Based Noninvasive Ventilation in Air Medical Transport of Coronavirus Disease 2019 Patients

Helmet-based noninvasive ventilation (NIV) is a viable option for the safe transport of potential or known coronavirus disease 2019 patients. Given the most likely modes of transmission through droplets, aerosols, and fomite contact, airway procedures such as endotracheal intubation place air medical crews and other health care providers at high risk for exposure. This, together with data that suggest that a large cohort of coronavirus disease 2019 patients have better outcomes if we can avoid intubating them, creates a need for a safe method of NIV or high-flow oxygen delivery during transport. Commonly used and successful in-hospital regimens for these patients are high-flow nasal cannula and continuous positive airway pressure or bilevel positive airway pressure. In some studies, helmet NIV has been shown to be a viable, if not superior, alternative to these therapies for patients with acute hypoxemic respiratory failure. Furthermore, because it is a sealed and closed space that completely isolates the patient's airway and breathing, it provides a very high degree of protection from exposure to pathogens transmitted through droplets or aerosols. This article discusses practical implementation of helmet NIV in air medical transport.

Lower limb deep vein thrombosis in COVID-19 patients admitted to intermediate care respiratory units

COVID-19 has been associated with an increased risk of thrombotic events; however, the reported incidence of deep vein thrombosis varies depending, at least in part, on the severity of the disease. Aim of this prospective, multicenter, observational study was to investigate the incidence of lower limb deep vein thrombosis as assessed by compression ultrasound in consecutive patients admitted to three pulmonary medicine wards designated to care for patients with COVID-19 related pneumonia, with or without respiratory failure but not requiring admission to an intensive care unit. Consecutive patients admitted between March 27 and May 6, 2020 were enrolled. Patients were excluded if they were less than 18-year-old or if compression ultrasound could not be performed for any reason. Patients were assessed at admission (t0) and after 7 days (t1). Major and non-major clinically relevant bleedings were recorded. Sixty-eight patients were enrolled. Two were excluded due to anatomical abnormalities that prevented compression ultrasound; sixty patients were retested at (t1). All patients were started on antithrombotic prophylaxis, unless therapeutic anticoagulation was required. Deep vein thrombosis as assessed by compression ultrasound was observed in 2 patients (3%); one of them was later deemed to represent a previous episode. No new episodes were detected at t1. One major and 2 non-major clinically relevant bleedings were observed. In the setting of patients with COVID-related pneumonia not requiring admission to an intensive care unit, the incidence of deep vein thrombosis is low and our data support not screening asymptomatic patients.

Caution against precaution: A case report on silent hypoxia in COVID-19

Introduction

Silent hypoxia is an entity that has been described in patients diagnosed with COVID-19. It is typically described as objective hypoxia in the absence of proportional respiratory distress. The physiological basis for this phenomenon is controversial, and its prognostic value is unclear. We present a case below, of a 66-year-old female presenting with severe hypoxia that was managed without mechanical ventilation.

Presentation of case

A 66 year old female with multiple comorbidities initially presented with a cough, fever and an oxygen saturation of 70% on room air in the absence of respiratory distress or altered mentation. She subsequently tested positive for COVID-19 and was admitted to the intensive care unit; received oxygen via high flow nasal cannula and continuous positive pressure mask. The patient remained in the intensive care unit for 40 days under close observation and exhibited multiple episodes of silent hypoxia on weaning oxygen. She was discharged on room air with an oxygen saturation >90% after 56 days. The patient was not intubated during her stay.

Discussion and conclusion

Clinicians face a clinical dilemma on whether to intubate a “silently hypoxemic” patient, who displays hypoxia out of proportion to clinical examination. The decision is confounded by a lack of clear evidence on whether the benefits of precautionary intubation outweighs the risks, especially in the current COVID-19 pandemic. A recent paradigm shift that recommends delaying intubation further displays the need for clearer analysis of the situation. Our case demonstrates a favorable outcome of the latter approach, yet emphasizes a case-by-case approach until clearer recommendations are available.

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COVID-19 may cause severe hypoxia in the absence of respiratory distress.

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The recommendations for intubating silently hypoxemic patients are unclear.

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Pre-emptive intubation versus close observation is currently debatable.

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The benefit to risk ratio of intubation should be considered carefully when determining management.

Early predictors of in-hospital mortality in patients with COVID-19 in a large American cohort

Coronavirus disease (COVID-19) has aggressively spread across the United States with numerous fatalities. Risk factors for mortality are poorly described. This was a multicentered cohort study identifying patient characteristics and diagnostic markers present on initial evaluation associated with mortality in hospitalized COVID-19 patients. Epidemiological, demographic, clinical, and laboratory characteristics of survivors and non-survivors were obtained from electronic medical records and a multivariable survival regression analysis was conducted to identify risk factors of in-hospital death. Of 1629 consecutive hospitalized adult patients with confirmed COVID-19 from March 1st thru March 31, 2020, 1461 patients were included in final analysis. 327 patients died during hospitalization and 1134 survived to discharge. Median age was 62 years (IQR 50.0, 74.0) with 56% of hospitalized patients under the age of 65. 47% were female and 63% identified as African American. Most patients (55%) had either no or one comorbidity. In multivariable analysis, older age, admission respiratory status including elevated respiratory rate and oxygen saturation ≤ 88%, and initial laboratory derangements of creatinine > 1.33 mg/dL, alanine aminotransferase > 40 U/L, procalcitonin > 0.5 ng/mL, and lactic acid ≥ 2 mmol/L increased risk of in-hospital death. This study is one of the largest analyses in an epicenter for the COVID-19 pandemic. Older age, low oxygen saturation and elevated respiratory rate on admission, and initial lab derangements including renal and hepatic dysfunction and elevated procalcitonin and lactic acid are risk factors for in-hospital death. These factors can help clinicians prognosticate and should be considered in management strategies.

Evidence-Based Management of the Critically Ill Adult With SARS-CoV-2 Infection

Human infection by the novel viral pathogen SARS-CoV-2 results in a clinical syndrome termed Coronavirus Disease 2019 (COVID-19). Although the majority of COVID-19 cases are self-limiting, a substantial minority of patients develop disease severe enough to require intensive care. Features of critical illness associated with COVID-19 include hypoxemic respiratory failure, acute respiratory distress syndrome (ARDS), shock, and multiple organ dysfunction syndrome (MODS). In most (but not all) respects critically ill patients with COVID-19 resemble critically ill patients with ARDS due to other causes and are optimally managed with standard, evidence-based critical care protocols. However, there is naturally an intense interest in developing specific therapies for severe COVID-19. Here we synthesize the rapidly expanding literature around the pathophysiology, clinical presentation, and management of COVID-19 with a focus on those points most relevant for intensivists tasked with caring for these patients. We specifically highlight evidence-based approaches that we believe should guide the identification, triage, respiratory support, and general ICU care of critically ill patients infected with SARS-CoV-2. In addition, in light of the pressing need and growing enthusiasm for targeted COVID-19 therapies, we review the biological basis, plausibility, and clinical evidence underlying these novel treatment approaches.

COVID-19 respiratory support in the emergency department setting

Introduction

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19), may result in severe complications, multiorgan dysfunction, acute respiratory failure, and death. SARS-CoV-2 is highly contagious and places healthcare workers at significant risk, especially during aerosol-generating procedures, including airway management.

Objective

This narrative review outlines the underlying respiratory pathophysiology of patients with COVID-19 and discusses approaches to airway management in the emergency department (ED) based on current literature.

Discussion

Patients presenting with SARS-CoV-2 infection are at high risk for acute respiratory failure requiring airway management. Among hospitalized patients, 10–20% require intensive care unit admission, and 3–10% require intubation and mechanical ventilation. While providing respiratory support for these patients, proper infection control measures, including adherence to personal protective equipment policies, are necessary to prevent nosocomial transmission to healthcare workers. A structured approach to respiratory failure in these patients includes the use of exogenous oxygen via nasal cannula or non-rebreather, as well as titrated high-flow nasal cannula and non-invasive ventilation. This review offers several guiding principles and resources designed to be adapted in conjunction with local workplace policies for patients requiring respiratory support.

Conclusions

While the fundamental principles of acute respiratory failure management are similar between COVID-19 and non-COVID-19 patients, there are some notable differences, including a focus on provider safety. This review provides an approach to airway management and respiratory support in the patient with COVID-19.

Severity of respiratory failure at admission and in-hospital mortality in patients with COVID-19: a prospective observational multicentre study

OBJECTIVES

COVID-19 causes lung parenchymal and endothelial damage that lead to hypoxic acute respiratory failure (hARF). The influence of hARF severity on patients' outcomes is still poorly understood.

DESIGN

Observational, prospective, multicentre study.

SETTING

Three academic hospitals in Milan (Italy) involving three respiratory high dependency units and three general wards.

PARTICIPANTS

Consecutive adult hospitalised patients with a virologically confirmed diagnosis of COVID-19. Patients aged <18 years or unable to provide informed consent were excluded.

INTERVENTIONS

Anthropometrical, clinical characteristics and blood biomarkers were assessed within the first 24 hours from admission. hARF was graded as follows: severe (partial pressure of oxygen to fraction of inspired oxygen ratio (PaO2/FiO2) <100 mm Hg); moderate (PaO2/FiO2 101-200 mm Hg); mild (PaO2/FiO2 201-300 mm Hg) and normal (PaO2/FiO2 >300 mm Hg).

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome was the assessment of clinical characteristics and in-hospital mortality based on the severity of respiratory failure. Secondary outcomes were intubation rate and application of continuous positive airway pressure during hospital stay.

RESULTS

412 patients were enrolled (280 males, 68%). Median (IQR) age was 66 (55-76) years with a PaO2/FiO2 at admission of 262 (140-343) mm Hg. 50.2% had a cardiovascular disease. Prevalence of mild, moderate and severe hARF was 24.4%, 21.9% and 15.5%, respectively. In-hospital mortality proportionally increased with increasing impairment of gas exchange (p<0.001). The only independent risk factors for mortality were age ≥65 years (HR 3.41; 95% CI 2.00 to 5.78, p<0.0001), PaO2/FiO2 ratio ≤200 mm Hg (HR 3.57; 95% CI 2.20 to 5.77, p<0.0001) and respiratory failure at admission (HR 3.58; 95% CI 1.05 to 12.18, p=0.04).

CONCLUSIONS

A moderate-to-severe impairment in PaO2/FiO2 was independently associated with a threefold increase in risk of in-hospital mortality. Severity of respiratory failure is useful to identify patients at higher risk of mortality.

TRIAL REGISTRATION NUMBER

NCT04307459.

IFCC Interim Guidelines on Biochemical/Hematological Monitoring of COVID-19 Patients

Routine biochemical and hematological tests have been reported to be useful in the stratification and prognostication of pediatric and adult patients with diagnosed coronavirus disease (COVID-19), correlating with poor outcomes such as the need for mechanical ventilation or intensive care, progression to multisystem organ failure, and/or death. While these tests are already well established in most clinical laboratories, there is still debate regarding their clinical value in the management of COVID-19, particularly in pediatrics, as well as the value of composite clinical risk scores in COVID-19 prognostication. This document by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Task Force on COVID-19 provides interim guidance on: (A) clinical indications for testing, (B) recommendations for test selection and interpretation, (C) considerations in test interpretation, and (D) current limitations of biochemical/hematological monitoring of COVID-19 patients. These evidence-based recommendations will provide practical guidance to clinical laboratories worldwide, underscoring the contribution of biochemical and hematological testing to our collective pandemic response.

The POSITIONED Study: Prone Positioning in Nonventilated Coronavirus Disease 2019 Patients-A Retrospective Analysis

Supplemental Digital Content is available in the text.

Objectives:

Given perceived similarities between coronavirus disease 2019 pneumonia and the acute respiratory distress syndrome, we explored whether awake self-proning improved outcomes in coronavirus disease 2019-infected patients treated in a rural medical center with limited resources during a significant local coronavirus disease 2019 outbreak.

Design:

Retrospective analysis of prospectively collected clinical data.

Setting:

Single-center rural community-based medical center in Grand Island, NE.

Patients:

One hundred five nonintubated, coronavirus disease-infected patients.

Interventions:

None.

Measurements and Main Results:

After patients were educated on the benefits of awake self-proning, compliance was voluntary. The primary outcome was need for intubation during the hospital stay; secondary outcomes included serial peripheral capillary oxygen saturation measured by pulse oximetry to the Fio₂ ratios, in-hospital mortality, and discharge disposition. Of 105 nonintubated, coronavirus disease-infected patients, 40 tolerated awake self-proning. Patients who were able to prone were younger and had lower disease severity. The risk of intubation was lower in proned patients after adjusting for disease severity using Sequential Organ Failure Assessment scores (adjusted hazard ratio, 0.30; 95% CI, 0.09–0.96; p = 0.043) or Acute Physiology and Chronic Health Evaluation II scores (adjusted hazard ratio, 0.30; 95% CI, 0.10–0.91; p = 0.034). No prone patient died compared with 24.6% of patients who were not prone (p < 0.001; number needed to treat = 5; 95% CI, 3–8). The probability of being discharged alive and peripheral capillary oxygen saturation measured by pulse oximetry to the Fio₂ ratios were statistically similar for both groups.

Conclusions:

Awake self-proning was associated with lower mortality and intubation rates in coronavirus disease 2019-infected patients. Prone positioning appears to be a safe and inexpensive strategy to improve outcomes and spare limited resources. Prospective efforts are needed to better delineate the effect of awake proning on oxygenation and to improve patients’ ability to tolerate this intervention.

Emergency Department Management of COVID-19: An Evidence-Based Approach

The novel coronavirus, SARs-CoV-2, causes a clinical disease known as COVID-19. Since being declared a global pandemic, a significant amount of literature has been produced and guidelines are rapidly changing as more light is shed on this subject. Decisions regarding disposition must be made with attention to comorbidities. Multiple comorbidities portend a worse prognosis. Many clinical decision tools have been postulated; however, as of now, none have been validated. Laboratory testing available to the emergency physician is nonspecific but does show promise in helping prognosticate and risk stratify. Radiographic testing can also aid in the process. Escalating oxygen therapy seems to be a safe and effective therapy; delaying intubation for only the most severe cases in which respiratory muscle fatigue or mental status demands this. Despite thrombotic concerns in COVID-19, the benefit of anticoagulation in the emergency department (ED) seems to be minimal. Data regarding adjunctive therapies such as steroids and nonsteroidal anti-inflammatories are variable with no concrete recommendations, although steroids may decrease mortality in those patients developing acute respiratory distress syndrome. With current guidelines in mind, we propose a succinct flow sheet for both the escalation of oxygen therapy as well as ED management and disposition of these patients.

Misconceptions of pathophysiology of happy hypoxemia and implications for management of COVID-19

In the article “The pathophysiology of ‘happy’ hypoxemia in COVID-19,” Dhont et al. (Respir Res 21:198, 2020) discuss pathophysiological mechanisms that may be responsible for the absence of dyspnea in patients with COVID-19 who exhibit severe hypoxemia. The authors review well-known mechanisms that contribute to development of hypoxemia in patients with pneumonia, but are less clear as to why patients should be free of respiratory discomfort despite arterial oxygen levels commonly regarded as life threatening. The authors propose a number of therapeutic measures for patients with COVID-19 and happy hypoxemia; we believe readers should be alerted to problems with the authors’ interpretations and recommendations.

Silent hypoxia: a frequently overlooked clinical entity in patients with COVID-19

COVID-19 caused by SARS-CoV-2 may present with a wide spectrum of symptoms ranging from mild upper respiratory tract infection like illness to severe pneumonia and death. Patients may have severe hypoxaemia without proportional features of respiratory distress, also known as 'silent' or 'apathetic' hypoxia. We present a case of a 56-year-old man with COVID-19 who presented to the fever clinic of our institution with fever and cough without any respiratory distress but low oxygen saturation. The patient deteriorated over the next 2 days but eventually recovered of his illness in due course of time. This case demonstrates 'silent hypoxia' as a possible presentation in COVID-19 and emphasises the importance of meticulous clinical examination including oxygen saturation measurements in suspected or confirmed patients.

Respiratory physiology of COVID-19-induced respiratory failure compared to ARDS of other etiologies

BACKGROUND

Whether respiratory physiology of COVID-19-induced respiratory failure is different from acute respiratory distress syndrome (ARDS) of other etiologies is unclear. We conducted a single-center study to describe respiratory mechanics and response to positive end-expiratory pressure (PEEP) in COVID-19 ARDS and to compare COVID-19 patients to matched-control subjects with ARDS from other causes.

METHODS

Thirty consecutive COVID-19 patients admitted to an intensive care unit in Rome, Italy, and fulfilling moderate-to-severe ARDS criteria were enrolled within 24 h from endotracheal intubation. Gas exchange, respiratory mechanics, and ventilatory ratio were measured at PEEP of 15 and 5 cmH2O. A single-breath derecruitment maneuver was performed to assess recruitability. After 1:1 matching based on PaO2/FiO2, FiO2, PEEP, and tidal volume, COVID-19 patients were compared to subjects affected by ARDS of other etiologies who underwent the same procedures in a previous study.

RESULTS

Thirty COVID-19 patients were successfully matched with 30 ARDS from other etiologies. At low PEEP, median [25th-75th percentiles] PaO2/FiO2 in the two groups was 119 mmHg [101-142] and 116 mmHg [87-154]. Average compliance (41 ml/cmH2O [32-52] vs. 36 ml/cmH2O [27-42], p = 0.045) and ventilatory ratio (2.1 [1.7-2.3] vs. 1.6 [1.4-2.1], p = 0.032) were slightly higher in COVID-19 patients. Inter-individual variability (ratio of standard deviation to mean) of compliance was 36% in COVID-19 patients and 31% in other ARDS. In COVID-19 patients, PaO2/FiO2 was linearly correlated with respiratory system compliance (r = 0.52 p = 0.003). High PEEP improved PaO2/FiO2 in both cohorts, but more remarkably in COVID-19 patients (p = 0.005). Recruitability was not different between cohorts (p = 0.39) and was highly inter-individually variable (72% in COVID-19 patients and 64% in ARDS from other causes). In COVID-19 patients, recruitability was independent from oxygenation and respiratory mechanics changes due to PEEP.

CONCLUSIONS

Early after establishment of mechanical ventilation, COVID-19 patients follow ARDS physiology, with compliance reduction related to the degree of hypoxemia, and inter-individually variable respiratory mechanics and recruitability. Physiological differences between ARDS from COVID-19 and other causes appear small.

Pathophysiology, Transmission, Diagnosis, and Treatment of Coronavirus Disease 2019 (COVID-19): A Review

IMPORTANCE

The coronavirus disease 2019 (COVID-19) pandemic, due to the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a worldwide sudden and substantial increase in hospitalizations for pneumonia with multiorgan disease. This review discusses current evidence regarding the pathophysiology, transmission, diagnosis, and management of COVID-19.

OBSERVATIONS

SARS-CoV-2 is spread primarily via respiratory droplets during close face-to-face contact. Infection can be spread by asymptomatic, presymptomatic, and symptomatic carriers. The average time from exposure to symptom onset is 5 days, and 97.5% of people who develop symptoms do so within 11.5 days. The most common symptoms are fever, dry cough, and shortness of breath. Radiographic and laboratory abnormalities, such as lymphopenia and elevated lactate dehydrogenase, are common, but nonspecific. Diagnosis is made by detection of SARS-CoV-2 via reverse transcription polymerase chain reaction testing, although false-negative test results may occur in up to 20% to 67% of patients; however, this is dependent on the quality and timing of testing. Manifestations of COVID-19 include asymptomatic carriers and fulminant disease characterized by sepsis and acute respiratory failure. Approximately 5% of patients with COVID-19, and 20% of those hospitalized, experience severe symptoms necessitating intensive care. More than 75% of patients hospitalized with COVID-19 require supplemental oxygen. Treatment for individuals with COVID-19 includes best practices for supportive management of acute hypoxic respiratory failure. Emerging data indicate that dexamethasone therapy reduces 28-day mortality in patients requiring supplemental oxygen compared with usual care (21.6% vs 24.6%; age-adjusted rate ratio, 0.83 [95% CI, 0.74-0.92]) and that remdesivir improves time to recovery (hospital discharge or no supplemental oxygen requirement) from 15 to 11 days. In a randomized trial of 103 patients with COVID-19, convalescent plasma did not shorten time to recovery. Ongoing trials are testing antiviral therapies, immune modulators, and anticoagulants. The case-fatality rate for COVID-19 varies markedly by age, ranging from 0.3 deaths per 1000 cases among patients aged 5 to 17 years to 304.9 deaths per 1000 cases among patients aged 85 years or older in the US. Among patients hospitalized in the intensive care unit, the case fatality is up to 40%. At least 120 SARS-CoV-2 vaccines are under development. Until an effective vaccine is available, the primary methods to reduce spread are face masks, social distancing, and contact tracing. Monoclonal antibodies and hyperimmune globulin may provide additional preventive strategies.

CONCLUSIONS AND RELEVANCE

As of July 1, 2020, more than 10 million people worldwide had been infected with SARS-CoV-2. Many aspects of transmission, infection, and treatment remain unclear. Advances in prevention and effective management of COVID-19 will require basic and clinical investigation and public health and clinical interventions.

A physiological approach to understand the role of respiratory effort in the progression of lung injury in SARS-CoV-2 infection

Deterioration of lung function during the first week of COVID-19 has been observed when patients remain with insufficient respiratory support. Patient self-inflicted lung injury (P-SILI) is theorized as the responsible, but there is not robust experimental and clinical data to support it. Given the limited understanding of P-SILI, we describe the physiological basis of P-SILI and we show experimental data to comprehend the role of regional strain and heterogeneity in lung injury due to increased work of breathing.

In addition, we discuss the current approach to respiratory support for COVID-19 under this point of view.

Inpatient Care during the COVID-19 Pandemic: A Survey of Italian Physicians

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a potentially fatal disease that is of great global public health concern.

OBJECTIVE

We explored the clinical management of inpatients with COVID-19 in Italy.

METHODS

A self-administered survey was sent by email to Italian physicians caring for adult patients with COVID-19. A panel of experts was selected according to their clinical curricula and their responses were analyzed.

RESULTS

A total of 1,215 physicians completed the survey questionnaire (17.4% response rate). Of these, 188 (15.5%) were COVID-19 experts. Chest computed tomography was the most used method to detect and monitor COVID-19 pneumonia. Most of the experts managed acute respiratory failure with CPAP (56.4%), high flow nasal cannula (18.6%), and non-invasive mechanical ventilation (8%), while an intensivist referral for early intubation was requested in 17% of the cases. Hydroxychloroquine was prescribed as an antiviral in 90% of cases, both as monotherapy (11.7%), and combined with protease inhibitors (43.6%) or azithromycin (36.2%). The experts unanimously prescribed low-molecular-weight heparin to patients with severe COVID-19 pneumonia, and half of them (51.6%) used a dose higher than standard. The respiratory burden in patients who survived the acute phase was estimated as relevant in 28.2% of the cases, modest in 39.4%, and negligible in 9%.

CONCLUSIONS

In our survey some major topics, such as the role of non-invasive respiratory support and drug treatments, show disagreement between experts, likely reflecting the absence of high-quality evidence studies. Considering the significant respiratory sequelae reported following COVID-19, proper respiratory and physical therapy programs should be promptly made available.

Invasive and Non-Invasive Ventilation in Patients With COVID-19

BACKGROUND

The reported high mortality of COVID-19 patients in intensive care has given rise to a debate over whether patients with this disease are being intubated too soon and might instead benefit from more non-invasive ventilation.

METHODS

This review is based on articles published up to 12 June 2020 that were retrieved by a selective literature search on the topic of invasive and non-invasive ventilation for respiratory failure in COVID-19. Guideline recommendations and study data on patients with respiratory failure in settings other than COVID-19 are also considered, as are the current figures of the intensive care registry of the German Interdisciplinary Association for Intensive Care and Emergency Medicine (Deutsche Interdisziplinäre Vereinigung für Intensiv- und Notfallmedizin).

RESULTS

The high mortality figures among patients receiving invasive ventilation that have been reported in studies from abroad cannot be uncritically applied to the current situation in Germany. Study data on ventilation specifically in COVID-19 patients would be needed to do justice to the special pathophysiology of this disease, but such data are lacking. Being intubated too early is evidently associated with risks for the patient, but being intubated too late is as well. A particularly im - portant consideration is the potential harm associated with prolonged spontaneous breathing, with or without non-invasive assistance, as any increase in respiratory work can seriously worsen respiratory failure. On the other hand, it is clearly unacceptable to intubate patients too early merely out of concern that the medical staff might become infected with COVID-19 if they were ventilated non-invasively.

CONCLUSION

Nasal high flow, non-invasive ventilation, and invasive ventilation with intubation should be carried out in a stepwise treatment strategy, under appropriate intensive-care monitoring and with the observance of all relevant anti-infectious precautions. Germany is better prepared that other countries to provide COVID-19 patients with appropriate respiratory care, in view of the high per capita density of intensive-care beds and the availability of a nationwide, interdisciplinary intensive care registry for the guidance and coordination of intensive care in patients who need it.

COVID-Activated Emergency Scaling of Anesthesiology Responsibilities Intensive Care Unit

In response to the rapidly evolving coronavirus disease 2019 (COVID-19) pandemic and the potential need for physicians to provide critical care services, the American Society of Anesthesiologists (ASA) has collaborated with the Society of Critical Care Anesthesiologists (SOCCA), the Society of Critical Care Medicine (SCCM), and the Anesthesia Patient Safety Foundation (APSF) to develop the COVID-Activated Emergency Scaling of Anesthesiology Responsibilities (CAESAR) Intensive Care Unit (ICU) workgroup. CAESAR-ICU is designed and written for the practicing general anesthesiologist and should serve as a primer to enable an anesthesiologist to provide limited bedside critical care services.

A pragmatic approach and treatment of coronavirus disease 2019 (COVID-19) in intensive care unit

There is a new global pandemic that emerged in China in 2019 that is threatening different populations with severe acute respiratory failure. The disease has enormous potential for transmissibility and requires drastic governmental measures, guided by social distancing and the use of protective devices (gloves, masks, and facial shields). Once the need for admission to the ICU is characterized, a set of essentially supportive therapies are adopted in order to offer multi-organic support and allow time for healing. Typically, patients who require ventilatory support have bilateral infiltrates in the chest X-ray and chest computed tomography showing ground-glass pulmonary opacities and subsegmental consolidations. Invasive ventilatory support should not be postponed in a scenario of intense ventilatory distress. The treatment is, in essence, supportive.

Why COVID-19 Silent Hypoxemia Is Baffling to Physicians

Patients with coronavirus disease (COVID-19) are described as exhibiting oxygen levels incompatible with life without dyspnea. The pairing-dubbed happy hypoxia but more precisely termed silent hypoxemia-is especially bewildering to physicians and is considered as defying basic biology. This combination has attracted extensive coverage in media but has not been discussed in medical journals. It is possible that coronavirus has an idiosyncratic action on receptors involved in chemosensitivity to oxygen, but well-established pathophysiological mechanisms can account for most, if not all, cases of silent hypoxemia. These mechanisms include the way dyspnea and the respiratory centers respond to low levels of oxygen, the way the prevailing carbon dioxide tension (PaCO2) blunts the brain's response to hypoxia, effects of disease and age on control of breathing, inaccuracy of pulse oximetry at low oxygen saturations, and temperature-induced shifts in the oxygen dissociation curve. Without knowledge of these mechanisms, physicians caring for patients with hypoxemia free of dyspnea are operating in the dark, placing vulnerable patients with COVID-19 at considerable risk. In conclusion, features of COVID-19 that physicians find baffling become less strange when viewed in light of long-established principles of respiratory physiology; an understanding of these mechanisms will enhance patient care if the much-anticipated second wave emerges.

COVID-19 Compared to Other Pandemic Diseases

In December 2019, the first cases of a new contagious disease were diagnosed in the city of Wuhan, the capital of Hubei province in China. Within a short period of time the outbreak developed exponentially into a pandemic that infected millions of people, with a global death toll of more than 500,000 during its first 6 months. Eventually, the novel disease was named coronavirus disease 2019 (COVID-19), and the new virus was identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Similar to all known pandemics throughout history, COVID-19 has been accompanied by a large degree of fear, anxiety, uncertainty, and economic disaster worldwide. Despite multiple publications and increasing knowledge regarding the biological secrets of SARS-CoV-2, as of the writing of this paper, there is neither an approved vaccine nor medication to prevent infection or cure for this highly infectious disease. Past pandemics were caused by a wide range of microbes, primarily viruses, but also bacteria. Characteristically, a significant proportion of them originated in different animal species (zoonoses). Since an understanding of the microbial cause of these diseases was unveiled relatively late in human history, past pandemics were often attributed to strange causes including punishment from God, demonic activity, or volatile unspecified substances. Although a high case fatality ratio was common to all pandemic diseases, some striking clinical characteristics of each disease allowed contemporaneous people to clinically diagnose the infection despite null microbiological information. In comparison to past pandemics, SARS-CoV-2 has tricky and complex mechanisms that have facilitated its rapid and catastrophic spread worldwide.

Effectiveness and applicability of Non-Invasive Ventilation (NIV) in the Emergency Department in acute respiratory failure due to Sars-CoV-2 pneumonia

Treatment of de novo acute hypoxic respiratory failure is not recommended by current Non-Invasive Ventilation (NIV) guidelines as it does not seem to improve patients outcome. Many cases of acute hypoxic respiratory failure associated with Sars-Cov2 infection (SARI) have been observed during Sars-Cov2 pandemic. So far, data are missing regarding the use of NIV, but a correct identification of subgroups of patients based on different clinical, patho-physiological and radiological features, might be helpful for stratifying patients and choosing the correct respiratory support (invasive versus non-invasive). In case of NIV appliance, risk of environmental virus dispersion is particularly elevated; therefore, extreme attention by operators is required.

COVID-19-associated acute respiratory distress syndrome: is a different approach to management warranted?

The COVID-19 pandemic has seen a surge of patients with acute respiratory distress syndrome (ARDS) in intensive care units across the globe. As experience of managing patients with COVID-19-associated ARDS has grown, so too have efforts to classify patients according to respiratory system mechanics, with a view to optimising ventilatory management. Personalised lung-protective mechanical ventilation reduces mortality and has become the mainstay of treatment in ARDS. In this Viewpoint, we address ventilatory strategies in the context of recent discussions on phenotypic heterogeneity in patients with COVID-19-associated ARDS. Although early reports suggested that COVID-19-associated ARDS has distinctive features that set it apart from historical ARDS, emerging evidence indicates that the respiratory system mechanics of patients with ARDS, with or without COVID-19, are broadly similar. In the absence of evidence to support a shift away from the current paradigm of ventilatory management, we strongly recommend adherence to evidence-based management, informed by bedside physiology, as resources permit.

Overview: Systemic Inflammatory Response Derived From Lung Injury Caused by SARS-CoV-2 Infection Explains Severe Outcomes in COVID-19

Most SARS-CoV2 infections will not develop into severe COVID-19. However, in some patients, lung infection leads to the activation of alveolar macrophages and lung epithelial cells that will release proinflammatory cytokines. IL-6, TNF, and IL-1β increase expression of cell adhesion molecules (CAMs) and VEGF, thereby increasing permeability of the lung endothelium and reducing barrier protection, allowing viral dissemination and infiltration of neutrophils and inflammatory monocytes. In the blood, these cytokines will stimulate the bone marrow to produce and release immature granulocytes, that return to the lung and further increase inflammation, leading to acute respiratory distress syndrome (ARDS). This lung-systemic loop leads to cytokine storm syndrome (CSS). Concurrently, the acute phase response increases the production of platelets, fibrinogen and other pro-thrombotic factors. Systemic decrease in ACE2 function impacts the Renin-Angiotensin-Kallikrein-Kinin systems (RAS-KKS) increasing clotting. The combination of acute lung injury with RAS-KKS unbalance is herein called COVID-19 Associated Lung Injury (CALI). This conservative two-hit model of systemic inflammation due to the lung injury allows new intervention windows and is more consistent with the current knowledge.

Easier access to mechanical ventilation worldwide: an urgent need for low income countries, especially in face of the growing COVID-19 crisis

That positive pressure mechanical ventilation can save lives was proved during the poliomyelitis epidemics of the 1950s. Since that time there has been a growing increase in the use of ventilatory support, and it has been closely associated with the development of critical care medicine [1]. Positive pressure ventilation can be life-saving in patients with acute severe hypoxaemia that is refractory to more conservative measures. In patients with severe cardiopulmonary distress for whom the effort of breathing is intolerable, mechanical ventilation substitutes for the action of the respiratory muscles [1].

Combining easy-to-build noninvasive ventilator and open-source hardware description, may allow for adequate availability of ventilators to patients in low- and middle-income countries. This is urgently needed in the growing COVID-19 epidemic. https://bit.ly/3f8ZkUR

Hospital Preparedness for COVID-19: A Practical Guide from a Critical Care Perspective

In response to the estimated potential impact of coronavirus disease (COVID-19) on New York City hospitals, our institution prepared for an influx of critically ill patients. Multiple areas of surge planning progressed, simultaneously focused on infection control, clinical operational challenges, ICU surge capacity, staffing, ethics, and maintenance of staff wellness. The protocols developed focused on clinical decisions regarding intubation, the use of high-flow oxygen, engagement with infectious disease consultants, and cardiac arrest. Mechanisms to increase bed capacity and increase efficiency in ICUs by outsourcing procedures were implemented. Novel uses of technology to minimize staff exposure to COVID-19 as well as to facilitate family engagement and end-of-life discussions were encouraged. Education and communication remained key in our attempts to standardize care, stay apprised on emerging data, and review seminal literature on respiratory failure. Challenges were encountered and overcome through interdisciplinary collaboration and iterative surge planning as ICU admissions rose. Support was provided for both clinical and nonclinical staff affected by the profound impact COVID-19 had on our city. We describe in granular detail the procedures and processes that were developed during a 1-month period while surge planning was ongoing and the need for ICU capacity rose exponentially. The approaches described here provide a potential roadmap for centers that must rapidly adapt to the tremendous challenge posed by this and potential future pandemics.

Reducing aerosol dispersion by High Flow Therapy in COVID-19: High Resolution Computational Fluid Dynamics Simulations of Particle Behavior during High Velocity Nasal Insufflation with a Simple Surgical Mask

Objective

All respiratory care represents some risk of becoming an aerosol‐generating procedure (AGP) during COVID‐19 patient management. Personal protective equipment (PPE) and environmental control/engineering is advised. High velocity nasal insufflation (HVNI) and high flow nasal cannula (HFNC) deliver high flow oxygen (HFO) therapy, established as a competent means of supporting oxygenation for acute respiratory distress patients, including that precipitated by COVID‐19. Although unlikely to present a disproportionate particle dispersal risk, AGP from HFO continues to be a concern. Previously, we published a preliminary model. Here, we present a subsequent highresolution simulation (higher complexity/reliability) to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during HVNI, low‐flow oxygen therapy (LFO2), and tidal breathing.

Methods

This in silico modeling study of HVNI, LFO2, and tidal breathing presents ANSYS fluent computational fluid dynamics simulations that evaluate the effect of Type I surgical mask use over patient face on particle/droplet behavior.

Results

This in silico modeling simulation study of HVNI (40 L min⁻¹) with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in LFO2 (6 L min⁻¹) capture, with particle distribution escaping to the room (> 1 m from face) lower for HVNI+Mask versus LFO2+Mask (8.23% vs 17.2%). The overwhelming proportion of particulate escape was associated with mask‐fit designed model gaps. Particle dispersion was associated with lower velocity.

Conclusions

These simulations suggest employing a surgical mask over the HVNI interface may be useful in reduction of particulate mass distribution associated with AGPs.

COVID-19: hemoglobin, iron, and hypoxia beyond inflammation. A narrative review

Coronavirus disease-19 (COVID-19) has been regarded as an infective-inflammatory disease, which affects mainly lungs. More recently, a multi-organ involvement has been highlighted, with different pathways of injury. A hemoglobinopathy, hypoxia and cell iron overload might have a possible additional role. Scientific literature has pointed out two potential pathophysiological mechanisms: i) severe acute respiratory syndrome-coronavirus-2 (SARS-CoV- 2) interaction with hemoglobin molecule, through CD147, CD26 and other receptors located on erythrocyte and/or blood cell precursors; ii) hepcidin-mimetic action of a viral spike protein, inducing ferroportin blockage. In this translational medicinebased narrative review, the following pathologic metabolic pathways, deriving from hemoglobin denaturation and iron metabolism dysregulation, are highlighted: i) decrease of functioning hemoglobin quote; ii) iron overload in cell/tissue (hyperferritinemia); iii) release of free toxic circulating heme; iv) hypoxemia and systemic hypoxia; v) reduction of nitric oxide; vi) coagulation activation; vii) ferroptosis with oxidative stress and lipoperoxidation; viii) mitochondrial degeneration and apoptosis. A few clinical syndromes may follow, such as pulmonary edema based on arterial vasoconstriction and altered alveolo-capillary barrier, sideroblastic-like anemia, endotheliitis, vasospastic acrosyndrome, and arterio- venous thromboembolism. We speculated that in COVID-19, beyond the classical pulmonary immune-inflammation view, the occurrence of an oxygen-deprived blood disease, with iron metabolism dysregulation, should be taken in consideration. A more comprehensive diagnostic/therapeutic approach to COVID-19 is proposed, including potential adjuvant interventions aimed at improving hemoglobin dysfunction, iron over-deposit and generalized hypoxic state.

Mechanisms of Hypoxia in COVID-19 Patients: A Pathophysiologic Reflection

Coronavirus disease-2019 (COVID-19) causes severe hypoxemia which fulfills the criteria of acute respiratory distress syndrome (ARDS) but is not accompanied by typical features of the syndrome. The combination of factors including low P/F ratios, high A-a gradient, relatively preserved lung mechanics, and normal pulmonary pressures may imply a process occurring on the vascular side of the alveolar–capillary unit. The scant but rapidly evolving data available on the pathophysiology are seemingly conflicting, indicating the relative dominance of intrapulmonary shunting or dead space in different studies. In this hypothesis paper, we attempt to gather and explain these observations within a unified conceptual framework by invoking the relative contributions of microvascular thrombosis, along with two proposed vascular mechanisms of capillary flow redistribution and flow through intrapulmonary arteriovenous anastomoses (IPAVA).

How to cite this article: Nitsure M, Sarangi B, Shankar GH, Reddy VS, Walimbe A, Sharma V, et al. Mechanisms of Hypoxia in COVID-19 Patients: A Pathophysiologic Reflection. Indian J Crit Care Med 2020;24(10):967–970.

A Multicenter Cross-sectional Questionnaire-based Study to Know the Practices and Strategies of Ventilatory Management of COVID-19 Patients among the Treating Physicians

Introduction

COVID-19 has been declared a pandemic by the World Health Organization (WHO). Many of the COVID-19 patients develop acute respiratory distress syndrome (ARDS) and require ventilatory support based on their severity for which conventional strategies are being used along with few newer strategies. We conducted this multicenter survey to know the physician's current ventilation strategies adopted for the care of COVID-19 patients.

Materials and methods

The survey was conducted after taking the ethical committee clearance. The web-based multicenter, cross-sectional questionnaire study was sent to physicians, who were involved in the management of COVID-19 patients. The questionnaire was segregated into three parts: part one consisted of general information and consent form, part two was concerned regarding demographic characteristics, and part three was concerned about their practices and strategies for ventilation of COVID-19 patients.

Results

A total of 223 responders replied for the questionnaire; 190 participated in the study saying that they are involved in the management of COVID-19 patients. The answers to the questionnaires were expressed as a percentage of total responses. 86% of the respondents said they have a designated intensive care unit (ICU) and 89% of the responders said they have an intubation/extubation protocol for suspect/confirmed COVID-19 patients. The responses of junior residents (JRs), senior residents (SRs), assistant professors/junior consultants, and professors/consultants were analyzed separately, and a few significant differences were observed. 39% of JRs were aware of prone ventilation as the most effective rescue ventilation strategy compared to 69% of consultants/professors. Extracorporeal membranous oxygenation (ECMO) strategy was also more significant in consultants/professors (40%) vs JRs (12%). The responders were also diverged based on medical college and corporate hospitals, and their responses were noted. Most commonly, responders in the corporate hospitals had a facility to ventilate COVID-19 patients in a negative pressure isolation facility compared to a nonnegative pressure room isolation facility in medical colleges.

Conclusion

Most of the responders were practicing ventilation strategies in a standard manner. JRs need to undergo further training in a few aspects of the ventilatory management, and also, they need to update themselves with newer treatment modalities as they keep evolving. Medical colleges are providing at par facility compared to corporate hospitals except for few advance care facilities.

Clinical significance

This study highlights the current practice of ventilatory management of COVID-19 patients, which is satisfactory. The survey can be used to develop study tools, to educate resident doctors, to further improve quality of care of critical COVID-19 patients.

How to cite this article

Maddani SS, Deepa HC, Rao S, Chaudhuri S. A Multicenter Cross-sectional Questionnaire-based Study to know the Practices and Strategies of Ventilatory Management of COVID-19 Patients among the Treating Physicians. Indian J Crit Care Med 2020;24(8):643–648.

Awake Prone Positioning in COVID-19 Patients

Background

The World Health Organization (WHO) has declared SARS-CoV-2 as pandemic. Patients with COVID-19 present mainly with respiratory symptoms. Prone position has been traditionally used in acute respiratory distress syndrome (ARDS) to improve oxygenation and prevent barotrauma in ventilated patients. Awake proning is being used as an investigational therapy in COVID to defer invasive ventilation, improve oxygenation, and outcomes. Hence, we conducted a retrospective case study to look for benefits of awake proning with oxygen therapy in non-intubated COVID patients.

Materials and methods

A retrospective case study of 15 COVID patients admitted from June 15 to July 1, 2020 to HDU in our hospital was conducted. Cooperative patients who were hemodynamically stable and SpO₂ < 90% on presentation were included. Oxygen was administered through facemask, non-rebreathing mask and noninvasive ventilation to patients as per requirement. Patients were encouraged to maintain prone position and target time was 10-12 hours/day. SpO₂ and P/f ratio in supine and prone position was observed till discharge. Primary target was SpO₂ > 95% and P/f > 200 mm Hg. Other COVID therapies were used according to institutional protocol.

Results

The mean SpO₂ on room air on admission was 80%. In day 1 to 3, the mean P/f ratio in supine position was 98.8 ± 29.7 mm Hg which improved to 136.6 ± 38.8 mm Hg after proning (p = 0.005). The difference was significant from day 1 to 10. Two patients were intubated. The mean duration of stay was 11 days.

Conclusion

Awake prone positioning showed marked improvement in P/f ratio and SpO₂ in COVID-19 patients with improvement in clinical symptoms with reduced rate of intubation.

Highlights

Prone position ventilation improves oxygenation by reducing V/Q mismatch.Awake prone positioning has been used along with high-flow oxygen therapy in recent pandemic of SARS-CoV-2 virus for management of mild to moderate cases.

How to cite this article

Singh P, Jain P, Deewan H. Awake Prone Positioning in COVID-19 Patients. Indian J Crit Care Med 2020;24(10):914-918.