Respiratory Physiology of COVID-19 and Influenza Associated Acute Respiratory Distress Syndrome

Abstract

Background: There is ongoing debate whether lung physiology of COVID-19-associated acute respiratory distress syndrome (ARDS) differs from ARDS of other origin. Objective: The aim of this study was to analyze and compare how critically ill patients with COVID-19 and Influenza A or B were ventilated in our tertiary care center with or without extracorporeal membrane oxygenation (ECMO). We ask if acute lung failure due to COVID-19 requires different intensive care management compared to conventional ARDS. Methods: 25 patients with COVID-19-associated ARDS were matched to a cohort of 25 Influenza patients treated in our center from 2011 to 2021. Subgroup analysis addressed whether patients on ECMO received different mechanical ventilation than patients without extracorporeal support. Results: Compared to Influenza-associated ARDS, COVID-19 patients had higher ventilatory system compliance (40.7 mL/mbar [31.8–46.7 mL/mbar] vs. 31.4 mL/mbar [13.7–42.8 mL/mbar], p = 0.198), higher ventilatory ratio (1.57 [1.31–1.84] vs. 0.91 [0.44–1.38], p = 0.006) and higher minute ventilation at the time of intubation (mean minute ventilation 10.7 l/min [7.2–12.2 l/min] for COVID-19 vs. 6.0 l/min [2.5–10.1 l/min] for Influenza, p = 0.013). There were no measurable differences in P/F ratio, positive end-expiratory pressure (PEEP) and driving pressures (ΔP). Respiratory system compliance deteriorated considerably in COVID-19 patients on ECMO during 2 weeks of mechanical ventilation (Crs, mean decrease over 2 weeks −23.87 mL/mbar ± 32.94 mL/mbar, p = 0.037) but not in ventilated Influenza patients on ECMO and less so in ventilated COVID-19 patients without ECMO. For COVID-19 patients, low driving pressures on ECMO were strongly correlated to a decline in compliance after 2 weeks (Pearson’s R 0.80, p = 0.058). Overall mortality was insignificantly lower for COVID-19 patients compared to Influenza patients (40% vs. 48%, p = 0.31). Outcome was insignificantly worse for patients requiring veno-venous ECMO in both groups (50% mortality for COVID-19 on ECMO vs. 27% without ECMO, p = 0.30/56% vs. 34% mortality for Influenza A/B with and without ECMO, p = 0.31). Conclusion: The pathophysiology of early COVID-19-associated ARDS differs from Influenza-associated acute lung failure by sustained respiratory mechanics during the early phase of ventilation. We question whether intubated COVID-19 patients on ECMO benefit from extremely low driving pressures, as this appears to accelerate derecruitment and consecutive loss of ventilatory system compliance.

Comparison of Clinical Characteristics and Outcomes in Intensive Care Units Between Patients with Coronavirus Disease 2019 (COVID-19) and Patients with Influenza: A Systematic Review and Meta-Analysis

“…Most of the data were from retrospective studies, 5,10,[15][16][17][18][19][20][22][23][24][25][26][28][29][30][32][33][34][35][37][38][39][40][41][42][43][44][45][46][47] 2 articles were prospective studies, 31,34 and 3 articles did not specify the type of study. 21,27,36 Four articles specifically studied patients with influenza A, 10,21,31,36 15 articles studied patients with type A/B, 5,15,16,20,[24][25][26][27]30,32,33,…”

“…Most of the data were from retrospective studies, 5,10,15–20,22–26,28–30,32–35,37–47 2 articles were prospective studies, 31,34 and 3 articles did not specify the type of study. 21,27,36 Four articles specifically studied patients with influenza A, 10,21,31,36 15 articles studied patients with type A/B, 5,15,16,20,24–27,30,32,33,37,39,40,47 16 articles did not state the influenza type of patients, 17–19,22,23,28,29,34,35,38,…”

“…In addition, SARS-CoV-2 and influenza virus share a common route of interpersonal transmission through aerosolized or respiratory droplets, and the diagnosis of both mainly depends on reverse transcription polymerase chain reaction. 9,10 Before the COVID-19 pandemic, influenza viruses were the most common cause of severe viral pneumonia. Influenza-associated hospitalizations for critical illness (between 5% and 19% of all influenza hospitalizations) have increased considerably over the past several decades.…”

Comparing Clinical Outcomes of COVID-19 and Influenza-Induced Acute Respiratory Distress Syndrome: A Propensity-Matched Analysis

“…Routine immunization for Influenza may also provide some degree of protective immunity against Influenza, and hence against I-ARDS; no COVID-19 vaccine was available in the US until December 2020, at which point it was only available to medical professionals [13]. Interestingly, the difference in disease progression can be explained by respiratory physiology in C-ARDS vs. I-ARDS patients, as a German study explains the sharp decline in respiratory system compliance in ventilated C-ARDS patients (40.7 mL/min to 23.87 mL/mbar in 2 weeks, p = 0.037) as they are transitioned to venovenous extracorporeal membrane oxygenation (VV-ECMO) compared to I-ARDS [14].…”

Suffocation in asthma and COVID-19: Supplementation of inhaled corticosteroids with alkaline hydrogen peroxide as an alternative to ECMO

“…That is why, in critical situation in these diseases, all patients are prescribed forced mechanical lungs ventilation with oxygen [11][12][13][14]. It is also not accidental that if it is impossible to normalize oxygen content in patient's blood through his lungs, the patient's blood oxygen saturation is increased by extracorporeal membrane oxygenation (ECMO) [15][16][17][18][19][20]. But ECMO is inaccessible to most patients, the technology itself is very dangerous for their life and health and many times increases the cost of COVID-19 treatment [21,22].…”