Positive end-expiratory pressure in COVID-19 acute respiratory distress syndrome: the heterogeneous effects.

BACKGROUND: We hypothesized that as CARDS may present different pathophysiological features than classic ARDS, the application of high levels of end-expiratory pressure is questionable. Our first aim was to investigate the effects of 5-15 cmH2O of PEEP on partitioned respiratory mechanics, gas exchange and dead space; secondly, we investigated whether respiratory system compliance and severity of hypoxemia could affect the response to PEEP on partitioned respiratory mechanics, gas exchange and dead space, dividing the population according to the median value of respiratory system compliance and oxygenation. Thirdly, we explored the effects of an additional PEEP selected according to the Empirical PEEP-FiO2 table of the EPVent-2 study on partitioned respiratory mechanics and gas exchange in a subgroup of patients. METHODS: Sixty-one paralyzed mechanically ventilated patients with a confirmed diagnosis of SARS-CoV-2 were enrolled (age 60 [54-67] years, PaO2/FiO2 113 [79-158] mmHg and PEEP 10 [10-10] cmH2O). Keeping constant tidal volume, respiratory rate and oxygen fraction, two PEEP levels (5 and 15 cmH2O) were selected. In a subgroup of patients an additional PEEP level was applied according to an Empirical PEEP-FiO2 table (empirical PEEP). At each PEEP level gas exchange, partitioned lung mechanics and hemodynamic were collected. RESULTS: At 15 cmH2O of PEEP the lung elastance, lung stress and mechanical power were higher compared to 5 cmH2O. The PaO2/FiO2, arterial carbon dioxide and ventilatory ratio increased at 15 cmH2O of PEEP. The arterial-venous oxygen difference and central venous saturation were higher at 15 cmH2O of PEEP. Both the mechanics and gas exchange variables significantly increased although with high heterogeneity. By increasing the PEEP from 5 to 15 cmH2O, the changes in partitioned respiratory mechanics and mechanical power were not related to hypoxemia or respiratory compliance. The empirical PEEP was 18 ± 1 cmH2O. The empirical PEEP significantly increased the PaO2/FiO2 but also driving pressure, lung elastance, lung stress and mechanical power compared to 15 cmH2O of PEEP. CONCLUSIONS: In COVID-19 ARDS during the early phase the effects of raising PEEP are highly variable and cannot easily be predicted by respiratory system characteristics, because of the heterogeneity of the disease.

Acid-Base Disorders in COVID-19 Patients with Acute Respiratory Distress Syndrome.

Our aim was to investigate the distribution of acid-base disorders in patients with COVID-19 ARDS using both the Henderson-Hasselbalch and Stewart's approach and to explore if hypoxemia can influence acid-base disorders. COVID-19 ARDS patients, within the first 48 h of the need for a non-invasive respiratory support, were retrospectively enrolled. Respiratory support was provided by helmet continuous positive airway pressure (CPAP) or by non-invasive ventilation. One hundred and four patients were enrolled, 84% treated with CPAP and 16% with non-invasive ventilation. Using the Henderson-Hasselbalch approach, 40% and 32% of patients presented respiratory and metabolic alkalosis, respectively; 13% did not present acid-base disorders. Using Stewart's approach, 43% and 33% had a respiratory and metabolic alkalosis, respectively; 12% of patients had a mixed disorder characterized by normal pH with a lower SID. The severe hypoxemic and moderate hypoxemic group presented similar frequencies of respiratory and metabolic alkalosis. The most frequent acid-base disorders were respiratory and metabolic alkalosis using both the Henderson-Hasselbalch and Stewart's approach. Stewart's approach detected mixed disorders with a normal pH probably generated by the combined effect of strong ions and weak acids. The impairment of oxygenation did not affect acid-base disorders.

Emergency Department Visits for allergy related-disorders among children: experience of a single Italian hospital during the first wave of the COVID-19 pandemic.

Introduction: The aim of this study was to compare the number of the Pediatric Emergency Department (PED) visits for young allergic patients with respiratory or cutaneous symptoms during the first wave of the coronavirus disease 19 (COVID-19) pandemic in 2020 with the same period in 2019, evaluating the percentage of positive cases to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). We carried out a retrospective analysis using data from young patients who visited the PED with cutaneous or respiratory symptoms in the period from 20th February to 12th May of the years 2020 and 2019. Data on allergy and COVID-19 nasal swab were also collected. We observed eleven (28.2%) PED visits for allergic patients with respiratory or cutaneous symptoms for the period from 20th February to 12th May of the year 2020 and ninety-three (31.8%) PED visits for the same time frame of the year 2019 (p=0.645). Only a two-month-old child out of 39 patients with non-allergic respiratory or cutaneous symptoms resulted positive for SARS-CoV-2. Specifically, we found for all the PED visits: 21 (7.2%) in 2019 vs 2 (5.1%) in 2020 for patients with urticaria/angioedema or atopic dermatitis (p=0.634); 3 (1.0%) in 2019 vs 3 (7.7%) in 2020 for patients with anaphylaxis (p=0.003); 19 (6.5%) in 2019 vs 2 (5.1%) in 2020 for those with asthma (p=0.740); 11(3.8%) in 2019 vs 1(2.6%) in 2020 for those with lower respiratory diseases, excluding asthma (p=0.706); 39(13.4%) in 2019 vs 3 (7.7%) in 2020 for those with upper respiratory diseases (URDs) (p=0.318). We also showed a substantial decrease (~80%) in all PED visits compared with the same time frame in 2019 (absolute number 263 vs 1,211, respectively). Among all the PED visits a significant reduction was mostly found for URDs [155 (12.8%) in 2019 vs 17 (6.5%) in 2020; p=0.045)]. The total number of PED visits for allergic patients with respiratory or cutaneous symptoms dropped precipitously in 2020. It is very tricky to estimate whether it was a protective action of allergy or the fear of contagion or the lockdown or a reduction in air pollution that kept children with allergy from visiting the PED. Further studies are needed to better understand the impact of underlying allergies on COVID-19 susceptibility and disease severity.