Efficacy and safety of the investigational complement C5 inhibitor zilucoplan in patients hospitalized with COVID-19: an open-label randomized controlled trial.

BACKGROUND: The efficacy and safety of complement inhibition in COVID-19 patients is unclear. METHODS: A multicenter randomized controlled, open-label trial. Hospitalized COVID-19 patients with signs of systemic inflammation and hypoxemia (PaO2/FiO2 below 350 mmHg) were randomized (2:1 ratio) to receive standard of care with or without the C5 inhibitor zilucoplan daily for 14 days, under antibiotic prophylaxis. The primary outcome was improvement in oxygenation at day 6 and 15. RESULTS: 81 patients were randomly assigned to zilucoplan (n = 55) or the control group (n = 26). 78 patients were included in the safety and primary analysis. Most were men (87%) and the median age was 63 years. The mean improvement in PaO2/FiO2 from baseline to day 6 was 56.4 mmHg in the zilucoplan group and 20.6 mmHg in the control group (mean difference + 35.8; 95% confidence interval (CI) - 9.4 to 80.9; p = 0.12), an effect also observed at day 15. Day 28 mortality was 9% in the zilucoplan and 21% in the control group (odds ratio 0.4; 95% CI 0.1 to 1.5). At long-term follow up, the distance walked in a 6-min test was 539.7 m in zilucoplan and 490.6 m in the control group (p = 0.18). Zilucoplan lowered serum C5b-9 (p < 0.001) and interleukin-8 (p = 0.03) concentration compared with control. No relevant safety differences between the zilucoplan and control group were identified. CONCLUSION: Administration of zilucoplan to COVID-19 patients in this proof-of-concept randomized trial was well tolerated under antibiotic prophylaxis. While not reaching statistical significance, indicators of respiratory function (PaO2/FiO2) and clinical outcome (mortality and 6-min walk test) suggest that C5 inhibition might be beneficial, although this requires further research in larger randomized studies.

Loss of GM-CSF-dependent instruction of alveolar macrophages in COVID-19 provides a rationale for inhaled GM-CSF treatment.

GM-CSF promotes myelopoiesis and inflammation, and GM-CSF blockade is being evaluated as a treatment for COVID-19-associated hyperinflammation. Alveolar GM-CSF is, however, required for monocytes to differentiate into alveolar macrophages (AMs) that control alveolar homeostasis. By mapping cross-species AM development to clinical lung samples, we discovered that COVID-19 is marked by defective GM-CSF-dependent AM instruction and accumulation of pro-inflammatory macrophages. In a multi-center, open-label RCT in 81 non-ventilated COVID-19 patients with respiratory failure, we found that inhalation of rhu-GM-CSF did not improve mean oxygenation parameters compared with standard treatment. However, more patients on GM-CSF had a clinical response, and GM-CSF inhalation induced higher numbers of virus-specific CD8 effector lymphocytes and class-switched B cells, without exacerbating systemic hyperinflammation. This translational proof-of-concept study provides a rationale for further testing of inhaled GM-CSF as a non-invasive treatment to improve alveolar gas exchange and simultaneously boost antiviral immunity in COVID-19. This study is registered at ClinicalTrials.gov (NCT04326920) and EudraCT (2020-001254-22).

Video-assisted thoracic surgery in critically ill COVID-19 patients on venovenous extracorporeal membrane oxygenation.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) leads to thoracic complications requiring surgery. This is challenging, particularly in patients supported with venovenous extracorporeal membrane oxygenation (VV-ECMO) due to the need for continuous therapeutic anticoagulation. We aim to share our experience regarding the safety and perioperative management of video-assisted thoracic surgery for this specific population. METHODS: Retrospective, single-center study between November 2020 and January 2022 at the ICU department of a 1.061-bed tertiary care and VV-ECMO referral center during the COVID-19 pandemic. RESULTS: 48 COVID-19 patients were supported with VV-ECMO. A total of 14 video-assisted thoracic surgery (VATS) procedures were performed in seven patients. Indications were mostly hemothorax (85.7%). In eight procedures heparin was stopped at least 1 h before incision. A total of 10 circuit changes due to clot formation or oxygen transfer failure were required in six patients (85.7%). One circuit replacement seemed related to the preceding VATS procedure, although polytransfusion might be a contributing factor. None of the mechanical complications was fatal. Four VATS-patients (57.1%) died, of which two (50%) immediately perioperatively due to uncontrollable bleeding. All three survivors were treated with additional transarterial embolization. CONCLUSION: (1) Thoracic complications in COVID-19 patients on VV-ECMO are common. (2) Indication for VATS is mostly hemothorax (3) Perioperative mortality is high, mostly due to uncontrollable bleeding. (4) Preoperative withdrawal of anticoagulation is not directly related to a higher rate of ECMO circuit-related complications, but a prolonged duration of VV-ECMO support and polytransfusion might be. (5) Additional transarterial embolization to control postoperative bleeding may further improve outcomes.

Prospective longitudinal evaluation of hospitalised COVID-19 survivors 3 and 12 months after discharge.

Background: Long-term outcome data of coronavirus disease 2019 (COVID-19) survivors are needed to understand their recovery trajectory and additional care needs. Methods: A prospective observational multicentre cohort study was carried out of adults hospitalised with COVID-19 from March through May 2020. Workup at 3 and 12 months following admission consisted of clinical review, pulmonary function testing, 6-min walk distance (6MWD), muscle strength, chest computed tomography (CT) and quality of life questionnaires. We evaluated factors correlating with recovery by linear mixed effects modelling. Results: Of 695 patients admitted, 299 and 226 returned at 3 and 12 months, respectively (median age 59 years, 69% male, 31% severe disease). About half and a third of the patients reported fatigue, dyspnoea and/or cognitive impairment at 3 and 12 months, respectively. Reduced 6MWD and quadriceps strength were present in 20% and 60% at 3 months versus 7% and 30% at 12 months. A high anxiety score and body mass index correlated with poor functional recovery. At 3 months, diffusing capacity for carbon monoxide (D LCO) and total lung capacity were below the lower limit of normal in 35% and 18%, decreasing to 21% and 16% at 12 months; predictors of poor D LCO recovery were female sex, pre-existing lung disease, smoking and disease severity. Chest CT improved over time; 10% presented non-progressive fibrotic changes at 1 year. Conclusion: Many COVID-19 survivors, especially those with severe disease, experienced limitations at 3 months. At 1 year, the majority showed improvement to almost complete recovery. To identify additional care or rehabilitation needs, we recommend a timely multidisciplinary follow-up visit following COVID-19 admission.

Prospective longitudinal evaluation of hospitalised COVID-19 survivors 3 and 12 months after discharge

Background Long-term outcome data of coronavirus disease 2019 (COVID-19) survivors are needed to understand their recovery trajectory and additional care needs. Methods A prospective observational multicentre cohort study was carried out of adults hospitalised with COVID-19 from March through May 2020. Workup at 3 and 12 months following admission consisted of clinical review, pulmonary function testing, 6-min walk distance (6MWD), muscle strength, chest computed tomography (CT) and quality of life questionnaires. We evaluated factors correlating with recovery by linear mixed effects modelling. Results Of 695 patients admitted, 299 and 226 returned at 3 and 12 months, respectively (median age 59 years, 69% male, 31% severe disease). About half and a third of the patients reported fatigue, dyspnoea and/or cognitive impairment at 3 and 12 months, respectively. Reduced 6MWD and quadriceps strength were present in 20% and 60% at 3 months versus 7% and 30% at 12 months. A high anxiety score and body mass index correlated with poor functional recovery. At 3 months, diffusing capacity for carbon monoxide (DLCO) and total lung capacity were below the lower limit of normal in 35% and 18%, decreasing to 21% and 16% at 12 months;predictors of poor DLCO recovery were female sex, pre-existing lung disease, smoking and disease severity. Chest CT improved over time;10% presented non-progressive fibrotic changes at 1 year. Conclusion Many COVID-19 survivors, especially those with severe disease, experienced limitations at 3 months. At 1 year, the majority showed improvement to almost complete recovery. To identify additional care or rehabilitation needs, we recommend a timely multidisciplinary follow-up visit following COVID-19 admission. Most hospitalised #COVID19 survivors show promising recovery 1 year after discharge, although mild symptoms may linger. Severe impairments are rare, but this study suggests an evaluation of the individual care needs after discharge.https://bit.ly/3sZK45x

Prevalence of Chronic Pulmonary Aspergillosis in Patients Suspected of Chest Malignancy.

Chronic pulmonary aspergillosis (CPA) is a potentially life-threatening fungal lung infection, and recent research suggests CPA to be more common than previously considered. Although CPA mimics other lung diseases including pulmonary cancer, awareness of this disease entity is still sparse. This study aimed to investigate the prevalence of CPA in a population of patients under suspicion of having lung cancer. We conducted a retrospective cohort study of 1200 patients and manually collected individual health record data from previous cancer examinations, with retrospective CPA status assessment using international criteria. Among 992 included patients, 16 (1.6%) fulfilled diagnostic criteria for CPA retrospectively, of whom 15 were undiscovered at initial lung cancer examination. The prevalence of CPA in this study population was 50 times higher than the reported prevalence of the overall European population. Our findings indicate that CPA is often missed in patients suspected of malignancy in the chest. Therefore, CPA should be kept in mind as a significant differential diagnosis.

Effect of anti-interleukin drugs in patients with COVID-19 and signs of cytokine release syndrome (COV-AID): a factorial, randomised, controlled trial.

BACKGROUND: Infections with SARS-CoV-2 continue to cause significant morbidity and mortality. Interleukin (IL)-1 and IL-6 blockade have been proposed as therapeutic strategies in COVID-19, but study outcomes have been conflicting. We sought to study whether blockade of the IL-6 or IL-1 pathway shortened the time to clinical improvement in patients with COVID-19, hypoxic respiratory failure, and signs of systemic cytokine release syndrome. METHODS: We did a prospective, multicentre, open-label, randomised, controlled trial, in hospitalised patients with COVID-19, hypoxia, and signs of a cytokine release syndrome across 16 hospitals in Belgium. Eligible patients had a proven diagnosis of COVID-19 with symptoms between 6 and 16 days, a ratio of the partial pressure of oxygen to the fraction of inspired oxygen (PaO2:FiO2) of less than 350 mm Hg on room air or less than 280 mm Hg on supplemental oxygen, and signs of a cytokine release syndrome in their serum (either a single ferritin measurement of more than 2000 µg/L and immediately requiring high flow oxygen or mechanical ventilation, or a ferritin concentration of more than 1000 µg/L, which had been increasing over the previous 24 h, or lymphopenia below 800/mL with two of the following criteria: an increasing ferritin concentration of more than 700 µg/L, an increasing lactate dehydrogenase concentration of more than 300 international units per L, an increasing C-reactive protein concentration of more than 70 mg/L, or an increasing D-dimers concentration of more than 1000 ng/mL). The COV-AID trial has a 2 × 2 factorial design to evaluate IL-1 blockade versus no IL-1 blockade and IL-6 blockade versus no IL-6 blockade. Patients were randomly assigned by means of permuted block randomisation with varying block size and stratification by centre. In a first randomisation, patients were assigned to receive subcutaneous anakinra once daily (100 mg) for 28 days or until discharge, or to receive no IL-1 blockade (1:2). In a second randomisation step, patients were allocated to receive a single dose of siltuximab (11 mg/kg) intravenously, or a single dose of tocilizumab (8 mg/kg) intravenously, or to receive no IL-6 blockade (1:1:1). The primary outcome was the time to clinical improvement, defined as time from randomisation to an increase of at least two points on a 6-category ordinal scale or to discharge from hospital alive. The primary and supportive efficacy endpoints were assessed in the intention-to-treat population. Safety was assessed in the safety population. This study is registered online with ClinicalTrials.gov (NCT04330638) and EudraCT (2020-001500-41) and is complete. FINDINGS: Between April 4, and Dec 6, 2020, 342 patients were randomly assigned to IL-1 blockade (n=112) or no IL-1 blockade (n=230) and simultaneously randomly assigned to IL-6 blockade (n=227; 114 for tocilizumab and 113 for siltuximab) or no IL-6 blockade (n=115). Most patients were male (265 [77%] of 342), median age was 65 years (IQR 54-73), and median Systematic Organ Failure Assessment (SOFA) score at randomisation was 3 (2-4). All 342 patients were included in the primary intention-to-treat analysis. The estimated median time to clinical improvement was 12 days (95% CI 10-16) in the IL-1 blockade group versus 12 days (10-15) in the no IL-1 blockade group (hazard ratio [HR] 0·94 [95% CI 0·73-1·21]). For the IL-6 blockade group, the estimated median time to clinical improvement was 11 days (95% CI 10-16) versus 12 days (11-16) in the no IL-6 blockade group (HR 1·00 [0·78-1·29]). 55 patients died during the study, but no evidence for differences in mortality between treatment groups was found. The incidence of serious adverse events and serious infections was similar across study groups. INTERPRETATION: Drugs targeting IL-1 or IL-6 did not shorten the time to clinical improvement in this sample of patients with COVID-19, hypoxic respiratory failure, low SOFA score, and low baseline mortality risk. FUNDING: Belgian Health Care Knowledge Center and VIB Grand Challenges program.

Early resuscitation orders in hospitalized oldest-old with COVID-19: A multicenter cohort study.

BACKGROUND: In particular older people are at risk of mortality due to corona virus disease 2019 (COVID-19). Advance care planning is essential to assist patient autonomy and prevent non-beneficial medical interventions. AIM: To describe early (taken within 72 h after hospital admission) resuscitation orders in oldest-old hospitalized with COVID-19. SETTING/PARTICIPANTS: A cohort of patients aged 80 years and older admitted to the acute hospital in March and April 2020 with COVID-19 were retrospectively recruited from 10 acute hospitals in Belgium. Recruitment was done through a network of geriatricians. RESULTS: Overall, 766 octogenarians were admitted of whom 49 were excluded because no therapeutic relationship with the geriatrician and six because of incomplete case report form. Early decisions not to consider intensive care admission were taken in 474/711 (66.7%) patients. This subgroup was characterized by significantly higher age, higher number of comorbidities and higher frailty level. There was a significant association between the degree of the treatment limitation and the degree of premorbid frailty (p < 0.001). Overall in-hospital mortality was 41.6% in patients with an early decision not to consider intensive care admission (67.1% in persons who developed respiratory failure vs 16.7% in patients without respiratory failure (p < 0.001)). Of 104 patients without early decision not to consider intensive care admission but who developed respiratory failure, 59 were eventually not transferred to intensive care unit with in-hospital mortality of 25.4%; 45 were transferred to the intensive care unit with mortality of 64.4%. CONCLUSIONS: Geriatricians applied all levels of treatment in oldest-old hospitalized with COVID-19. Early decisions not to consider intensive care admission were taken in two thirds of the cohort of whom more than 50% survived to hospital discharge by means of conservative treatment.

Vaccine-associated enhanced disease: Case definition and guidelines for data collection, analysis, and presentation of immunization safety data.

This is a Brighton Collaboration Case Definition of the term "Vaccine Associated Enhanced Disease" to be utilized in the evaluation of adverse events following immunization. The Case Definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of vaccines for SARS-CoV-2 vaccines and other emerging pathogens. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by selected Expert Reviewers prior to submission.

Conceptions of the pathophysiology of happy hypoxemia in COVID-19.

In their letter-to-the-editor entitled "Misconceptions of pathophysiology of happy hypoxemia and implications for management of COVID-19", Tobin et al. (Respir Res 21:249, 2020) debated our views on happy hypoxemia in COVID-19 (Respir Res 21:198, 2020). We thank the authors for their interesting comments and alternative viewpoints, and we would like to clarify several important aspects raised.

Sensitivity and specificity of 14 SARS-CoV-2 serological assays and their diagnostic potential in RT-PCR negative COVID-19 infections.

BACKGROUND: Molecular detection of SARS-CoV-2 in respiratory samples is the gold standard for COVID-19 diagnosis but it has a long turnaround time and struggles to detect low viral loads. Serology could help to diagnose suspected cases which lack molecular confirmation. Two case reports are presented as illustration. OBJECTIVES: The aim of this study was to evaluate the performance of several commercial assays for COVID-19 serology. We illustrated the added value of COVID-19 serology testing in suspect COVID-19 cases with negative molecular test. STUDY DESIGN: Twenty-three sera from 7 patients with a confirmed molecular diagnosis of SARS-CoV-2 were tested using 14 commercial assays. Additionally, 10 pre-pandemic sera and 9 potentially cross-reactive sera were selected. We calculated sensitivity and specificity. Furthermore, we discuss the diagnostic relevance of COVID-19 serology in a retrospective cohort of 145 COVID-19 cases in which repetitive molecular and serological SARS-CoV-2 tests were applied. RESULTS: The interpretation of the pooled sensitivity of IgM/A and IgG resulted in the highest values (range 14-71% on day 2-7; 88-94% on day 8-18). Overall, the specificity of the assays was high (range 79-100%). Among 145 retrospective cases, 3 cases (2%) remained negative after sequential molecular testing but positive on final SARS-CoV-2 serology. CONCLUSION: Sensitivity of COVID-19 serological diagnosis was variable but consistently increased at >7 days after symptom onset. Specificity was high. Our data suggest that serology can complement molecular testing for diagnosis of COVID-19, especially for patients presenting the 2nd week after symptom onset or later.

Case Report: Convalescent Plasma, a Targeted Therapy for Patients with CVID and Severe COVID-19.

The disease course of COVID-19 in patients with immunodeficiencies is unclear, as well as the optimal therapeutic strategy. We report a case of a 37-year old male with common variable immunodeficiency disorder and a severe SARS-CoV-2 infection. After administration of convalescent plasma, the patient's condition improved rapidly. Despite clinical recovery, viral RNA remained detectable up to 60 days after onset of symptoms. We propose that convalescent plasma might be considered as a treatment option in patients with CVID and severe COVID-19. In addition, in patients with immunodeficiencies, a different clinical course is possible, with prolonged viral shedding.

Zilucoplan in patients with acute hypoxic respiratory failure due to COVID-19 (ZILU-COV): A structured summary of a study protocol for a randomised controlled trial.

OBJECTIVES: Zilucoplan (complement C5 inhibitor) has profound effects on inhibiting acute lung injury post COVID-19, and can promote lung repair mechanisms that lead to improvement in lung oxygenation parameters. The purpose of this study is to investigate the efficacy and safety of Zilucoplan in improving oxygenation and short- and long-term outcome of COVID-19 patients with acute hypoxic respiratory failure. TRIAL DESIGN: This is a phase 2 academic, prospective, 2:1 randomized, open-label, multi-center interventional study. PARTICIPANTS: Adult patients (≥18y old) will be recruited at specialized COVID-19 units and ICUs at 9 Belgian hospitals. The main eligibility criteria are as follows: 1) Inclusion criteria: a. Recent (≥6 days and ≤16 days) SARS-CoV-2 infection. b. Chest CT scan showing bilateral infiltrates within the last 2 days prior to randomisation. c. Acute hypoxia (defined as PaO2/FiO2 below 350 mmHg or SpO2 below 93% on minimal 2 L/min supplemental oxygen). d. Signs of cytokine release syndrome characterized by either high serum ferritin, or high D-dimers, or high LDH or deep lymphopenia or a combination of those. 2) Exclusion criteria: e. Mechanical ventilation for more than 24 hours prior to randomisation. f. Active bacterial or fungal infection. g. History of meningococcal disease (due to the known high predisposition to invasive, often recurrent meningococcal infections of individuals deficient in components of the alternative and terminal complement pathways). INTERVENTION AND COMPARATOR: Patients in the experimental arm will receive daily 32,4 mg Zilucoplan subcutaneously and a daily IV infusion of 2g of the antibiotic ceftriaxone for 14 days (or until hospital discharge, whichever comes first) in addition to standard of care. These patients will receive additional prophylactic antibiotics until 14 days after the last Zilucoplan dose: hospitalized patients will receive a daily IV infusion of 2g of ceftriaxone, discharged patients will switch to daily 500 mg of oral ciprofloxacin. The control group will receive standard of care and a daily IV infusion of 2g of ceftriaxone for 1 week (or until hospital discharge, whichever comes first), to control for the effects of antibiotics on the clinical course of COVID-19. MAIN OUTCOMES: The primary endpoint is the improvement of oxygenation as measured by mean and/or median change from pre-treatment (day 1) to post-treatment (day 6 and 15 or at discharge, whichever comes first) in PaO2/FiO2 ratio, P(A-a)O2 gradient and a/A PO2 ratio. (PAO2= Partial alveolar pressure of oxygen, PaO2=partial arterial pressure of oxygen, FiO2=Fraction of inspired oxygen). RANDOMISATION: Patients will be randomized in a 2:1 ratio (Zilucoplan: control). Randomization will be done using an Interactive Web Response System (REDCap). BLINDING (MASKING): In this open-label trial neither participants, caregivers, nor those assessing the outcomes will be blinded to group assignment. NUMBERS TO BE RANDOMISED (SAMPLE SIZE): A total of 81 patients will be enrolled: 54 patients will be randomized to the experimental arm and 27 patients to the control arm. TRIAL STATUS: ZILU-COV protocol Version 4.0 (June 10 2020). Participant recruitment started on June 23 2020 and is ongoing. Given the uncertainty of the pandemic, it is difficult to predict the anticipated end date. TRIAL REGISTRATION: The trial was registered on Clinical Trials.gov on May 11th, 2020 (ClinicalTrials.gov Identifier: NCT04382755 ) and on EudraCT (Identifier: 2020-002130-33 ). FULL PROTOCOL: The full protocol is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest in expediting dissemination of this material, the familiar formatting has been eliminated; this Letter serves as a summary of the key elements of the full protocol.

Haemoptysis as the first presentation of COVID-19: a case report.

BACKGROUND: Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an ongoing pandemic that profoundly challenges healthcare systems all over the world. Fever, cough and fatigue are the most commonly reported clinical symptoms. CASE PRESENTATION: A 58-year-old man presented at the emergency department with acute onset haemoptysis. On the fifth day after admission, he developed massive haemoptysis. Computed tomography (CT) angiography of the chest revealed alveolar haemorrhage, more prominent in the left lung. Flexible bronchoscopy confirmed bleeding from the left upper lobe, confirmed by a bronchial arteriography, which was successfully embolized. Nasopharyngeal swabs (NPS) tested for SARS-CoV-2 using real-time polymerase chain reaction (RT-PCR) repeatedly returned negative. Surprisingly, SARS-CoV-2 was eventually detected in bronchoalveolar lavage (BAL) fluid. CONCLUSIONS: Life-threatening haemoptysis is an unusual presentation of COVID-19, reflecting alveolar bleeding as a rare but possible complication. This case emphasises the added value of bronchoscopy with BAL in the diagnostic work-up in case of high clinical suspicion and negative serial NPS in patients presenting with severe symptoms.

Myotonic dystrophy type 1 as a major risk factor for severe COVID-19?

The coronavirus disease 2019 (COVID-19) pandemic is challenging health care systems worldwide. People with myotonic dystrophy type 1 (DM1) represent a high-risk population during infectious disease outbreaks, little is known about the potential impact of COVID-19 on patients with DM1. We studied the clinical course of COVID-19 in three hospitalized patients with myotonic dystrophy type 1 or Steinert's disease, between April 1, 2020-April 30-2020. All three had advanced Steinert's disease receiving non-invasive nocturnal home ventilatory support. Two of them lived in a residential care centre. Two patients had a limited respiratory capacity, whereas one patient had a rather preserved functional capacity but more comorbidities. Two out of three patients were obese, none of them had diabetes mellitus. Two patients received hydroxychloroquine. Despite maximal supportive care with oxygen therapy, antibiotics, intensive respiratory physiotherapy and non-invasive positive pressure ventilation, all three patients eventually died due to COVID-19. Our case series of three patients with DM1 admitted for COVID-19 confirms that they are at high risk for severe disease and poor outcome. Clinical trials are needed to define best practices and determinants of outcomes in this unique population.

The pathophysiology of 'happy' hypoxemia in COVID-19.

The novel coronavirus disease 2019 (COVID-19) pandemic is a global crisis, challenging healthcare systems worldwide. Many patients present with a remarkable disconnect in rest between profound hypoxemia yet without proportional signs of respiratory distress (i.e. happy hypoxemia) and rapid deterioration can occur. This particular clinical presentation in COVID-19 patients contrasts with the experience of physicians usually treating critically ill patients in respiratory failure and ensuring timely referral to the intensive care unit can, therefore, be challenging. A thorough understanding of the pathophysiological determinants of respiratory drive and hypoxemia may promote a more complete comprehension of a patient's clinical presentation and management. Preserved oxygen saturation despite low partial pressure of oxygen in arterial blood samples occur, due to leftward shift of the oxyhemoglobin dissociation curve induced by hypoxemia-driven hyperventilation as well as possible direct viral interactions with hemoglobin. Ventilation-perfusion mismatch, ranging from shunts to alveolar dead space ventilation, is the central hallmark and offers various therapeutic targets.