COVID-19 Does Not Lead to a “Typical” Acute Respiratory Distress Syndrome

Abstract

An intermediate VT (7-8 ml/kg PBW) ventilation strategy was applied to the first four patients to increase pulmonary efficiency to eliminate CO 2 , and this was used in the next four patients. Gas exchange consists of oxygenation and ventilation. Oxygenation is quantified by the Pa O 2 /FI O 2 ratio, and this method has gained wide acceptance, particularly since publication of the Berlin definition of ARDS (7). However, the Berlin definition does not include additional pathophysiological information about ARDS, such as alveolar ventilation, as measured by pulmonary dead space, which is an important predictor of outcome (8). Increased pulmonary dead space reflects the inefficiency of the lungs to eliminate CO 2 , which may lead to hypercapnia. In our patients with ARDS with COVID-19, hypercapnia was common at ICU admission with low VT ventilation. Assuming the anatomic portion of dead space is constant, increasing VT with constant respiratory rate would effectively increase alveolar ventilation. Any such increase in VT would decrease Pa CO 2 , which would be captured by VR (6). VR, a novel method to monitor ventilatory adequacy at the bedside (4-6), was very high in our patients, reflecting increased pulmonary dead space and inadequacy of ventilation. With an acceptable plateau pressure and driving pressure, titration of VT was performed. Pa CO 2 and VR were significantly decreased when an intermediate VT (7-8 ml/kg PBW) was applied. We suggest that intermediate VT (7-8 ml/kg PBW) is recommended for such patients. Therefore, low VT may not be the best approach for all patients with ARDS, particularly those with a less severe decrease in respiratory system compliance and inadequacy of ventilation. In summary, we found that hypercapnia was common in patients with COVID-19-associated ARDS while using low VT ventilation. VR was increased in these patients, which reflected increased pulmonary dead space and inadequacy of ventilation. An intermediate VT was used to correct hypercapnia efficiently, while not excessively increasing driving pressure. Clinicians must have a high index of suspicion for increased pulmonary dead space when patients with COVID-19-related ARDS present with hypercapnia. n Author disclosures are available with the text of this letter at www.atsjournals.org.

SARS-CoV-2 in Spanish Intensive Care Units: Early experience with 15-day survival in Vitoria

“…In contrast with reports from China or Seattle suggesting a severe ARDS, a strategy of early intubation disclosed that SARS-CoV-2 does not lead to a typical ARDS. In our experience, two thirds of our patients have initial lung compliance > 40 ml/cm H20 postintubation being consistent with a preliminary report with 16 patients by Gattinoni et al (6), suggesting that ARDS is a consequence of acute lung injury associated with delayed intubation or super-infection.…”

“…Although more information on procalcitonin is required [12], our findings suggest that no prognostic information can be inferred. This early report of characteristics of SARS-CoV-2 influenza in Spain is of interest, as most information currently available is coming from large cohorts in China, or short case series from Italy or USA (5,6,11,13) . An important characteristic is that in the current cohort, no patients were exposed to prior non-invasive ventilation, which was commonly performed using a facial mask in Wuhan or a helmet in Italy, with a protocol of earlier intubation based on hyperventilation unable to maintain Satv02 above 90%.…”

“…Because most patients in China and Italy received non-invasive ventilation, information is needed on patients following a strategy of early intubation without inducing potential ventilator-induced lung injury. Moreover, in view of the limitation of resources, it is also important to improve insight on 7-day mortality and identify different phenotypes for personalised management [6]. In the capital of Alava, a city in the Basque Country which experienced the acceleration curve before other Spanish provinces (in relation to a massive contagion in a funeral) with 216% ICU capacity being already effective on March 18 th , 2020 (see comparison with Madrid (89%), Barcelona (17%) and other provinces in figure 1), anticipating the effect in other regions.…”

COVID-19 Critical Illness Pathophysiology Driven by Diffuse Pulmonary Thrombi and Pulmonary Endothelial Dysfunction Responsive to Thrombolysis

“…4 The improvement in oxygenation noted with increased PEEP in COVID-19 "ARDS" may be attributable to decreased cardiac output, leading to decreased shunt fraction rather than to alveolar recruitment. 1 Autopsy studies from the SARS outbreak of the early 2000s, caused by SARS-CoV-1 virus, have demonstrated pulmonary thrombi, pulmonary infarcts, and microthrombi in other organs. [5][6][7][8] It appears that SARS-CoV-2 is causing similar pathophysiological derangements.…”

“…While patients with COVID-19 respiratory failure may fulfill the Berlin criteria for acute respiratory distress syndrome (ARDS), their syndrome is atypical in that they have relatively well-preserved lung mechanics. 1 The marked dissociation between pulmonary mechanics and gas exchange raises the possibility of pulmonary vascular involvement.…”