Noninvasive respiratory support for COVID-19 patients: when, for whom, and how?

The significant mortality rate and prolonged ventilator days associated with invasive mechanical ventilation (IMV) in patients with severe COVID-19 have incited a debate surrounding the use of noninvasive respiratory support (NIRS) (i.e., HFNC, CPAP, NIV) as a potential treatment strategy. Central to this debate is the role of NIRS in preventing intubation in patients with mild respiratory disease and the potential beneficial effects on both patient outcome and resource utilization. However, there remains valid concern that use of NIRS may prolong time to intubation and lung protective ventilation in patients with more advanced disease, thereby worsening respiratory mechanics via self-inflicted lung injury. In addition, the risk of aerosolization with the use of NIRS has the potential to increase healthcare worker (HCW) exposure to the virus. We review the existing literature with a focus on rationale, patient selection and outcomes associated with the use of NIRS in COVID-19 and prior pandemics, as well as in patients with acute respiratory failure due to different etiologies (i.e., COPD, cardiogenic pulmonary edema, etc.) to understand the potential role of NIRS in COVID-19 patients. Based on this analysis we suggest an algorithm for NIRS in COVID-19 patients which includes indications and contraindications for use, monitoring recommendations, systems-based practices to reduce HCW exposure, and predictors of NIRS failure. We also discuss future research priorities for addressing unanswered questions regarding NIRS use in COVID-19 with the goal of improving patient outcomes.

Disparities in Lung Protective Ventilation in the United States

Background: Lung-protective ventilation is often used in critically ill patients with acute respiratory failure, including those without acute respiratory distress syndrome. While disparities exist in the delivery of critical care based on gender, race, and insurance status, it is unknown whether there are disparities in the use of lung-protective ventilation. The objective of our study was to determine whether gender-, racial / ethnic-, or insurance status-based disparities exist in the use of lung-protective ventilation for critically ill mechanically ventilated patients in the United States (U.S.).Methods: This was a secondary data analysis of the U.S. Critical Illness and Injury Trials Group Critical Illness Outcomes Study, a prospective multi-center cohort study conducted from 2010 - 2012. The dependent variable of interest was the proportion of patients receiving tidal volume > 8 mL/kg predicted body weight (PBW). The independent variables of interest were gender, insurance status, and race / ethnicity. Results: Our primary analysis included 1,595 mechanically ventilated patients from 59 intensive care units (ICUs) in the U.S. Women were more likely to receive tidal volumes > 8 ml/kg PBW than men (odds ratio [OR] = 3.25, 95% confidence interval [CI] = 2.58 – 4.09), though this relationship was substantially weakened after adjusting for gender differences in height (OR = 1.26 95% CI = 0.94 – 1.71). The underinsured were significantly more likely to receive tidal volume > 8 ml/kg PBW than the insured in multivariable analysis (odds ratio = 1.54, 95% confidence interval = 1.16 – 2.04). The prescription of > 8 ml/kg PBW tidal volume did not differ by racial or ethnic categories. Conclusions: In this prospective nationwide cohort of critically ill mechanically ventilated patients, women and the underinsured were less likely than their comparators to receive lung protective ventilation, with no apparent differences based on race / ethnicity alone. Differences in height between men and women do not fully explain this disparity. Future research should evaluate whether implicit bias affects tidal volume choice and other management decisions in critical care.

Hyaluronic acid plasma levels during high versus low tidal volume ventilation in a porcine sepsis model

Background Shedding of the endothelial glycocalyx can be observed regularly during sepsis. Moreover, sepsis may be associated with acute respiratory distress syndrome (ARDS), which requires lung protective ventilation with the two cornerstones of application of low tidal volume and positive end-expiratory pressure. This study investigated the effect of a lung protective ventilation on the integrity of the endothelial glycocalyx in comparison to a high tidal volume ventilation mode in a porcine model of sepsis-induced ARDS. Methods After approval by the State and Institutional Animal Care Committee, 20 male pigs were anesthetized and received a continuous infusion of lipopolysaccharide to induce septic shock. The animals were randomly assigned to either low tidal volume ventilation, high tidal volume ventilation, or no-LPS-group groups and observed for 6 h. In addition to the gas exchange parameters and hematologic analyses, the serum hyaluronic acid concentrations were determined from central venous blood and from pre- and postpulmonary and pre- and postcerebral circulation. Post-mortem analysis included histopathological evaluation and determination of the pulmonary and cerebral wet-to-dry ratios. Results Both sepsis groups developed ARDS within 6 h of the experiment and showed significantly increased serum levels of hyaluronic acid in comparison to the no-LPS-group. No significant differences in the hyaluronic acid concentrations were detected before and after pulmonary and cerebral circulation. There was also no significant difference in the serum hyaluronic acid concentrations between the two sepsis groups. Post-mortem analysis showed no significant difference between the two sepsis groups. Conclusion In a porcine model of septic shock and ARDS, the serum hyaluronic acid levels were significantly elevated in both sepsis groups in comparison to the no-LPS-group. Intergroup comparison between lung protective ventilated and high tidal ventilated animals revealed no significant differences in the serum hyaluronic acid levels.

Mechanical Ventilation with Dynamic Compliance-Guided Positive End-Expiratory Pressure in Laparoscopic Surgery with Trendelenburg Positioning: A Eandomised Controlled Study

BACKGROUND: The intraoperative cardiorespiratory effect of ventilation with individualised positive end-expiratory pressure guided by dynamic compliance (Cdyn) remains undefined. We investigated whether individualised protective ventilation would protect the heart and lung more efficiently than standard protective ventilation during abdominal laparoscopic surgery with Trendelenburg positioning.METHODS: Forty patients undergoing abdominal laparoscopic surgery were randomly divided into two groups: Group T (titrimetric PEEP) and Group I (intentional PEEP, 5 cmH2O). Parameters of right ventricular function were measured via transoesophageal echocardiography, including tricuspid annular plane systolic excursion (TAPSE), early filling-to-late filling ratio of the right ventricle, and right ventricular end-diastolic area/left ventricular end-diastolic area (RVEDA/LVEDA) ratio. Cdyn, driving pressure (∆P), ratio of dead space to tidal volume (VD/VT), and partial pressure of arterial oxygen to inspiratory oxygen fraction (PF) ratio were measured during mechanical ventilation.RESULTS: The RVEDA/LVEDA ratio in all patients increased significantly at T2 compared with T0, but there were no significant differences in TAPSE or E/A ratio between groups during the whole procedure (P>0.05). Cdyn, ∆P, and VD/VT ratios in Group T were significantly improved compared to those in Group I at T2 (P<0.05). There was no significant difference in the PF ratio between groups (P>0.05).CONCLUSIONS: Intraoperative lung-protective ventilation with Cdyn-guided PEEP improved Cdyn, ∆P, and VD/VT ratio without obvious side effects on right ventricular function compared to standard protective ventilation during laparoscopic surgery with Trendelenburg positioning, which suggests that it is a circulation-friendly way to titrate PEEP for intraoperative lung protective ventilation.TRIAL REGISTRATION: Trial registration date: 13/09/2020; Trial registration number: ChiCTR2000038212.

Tidal Volume in Pediatric Ventilation: Do You Get What You See?

Mechanical ventilators are increasingly evolving into computer-driven devices. These technical advancements have impact on clinical decisions in pediatric intensive care units (PICUs). A good understanding of the design of mechanical ventilators can improve clinical care. Tidal volume (TV) is one of the corner stones of ventilation: multiple technical factors influence the TV and, thus, influence clinical decision making. Ventilator manufacturers make various design choices regarding the phase, site and conditions of TV measurement as well as algorithmic processing choices. Such choice may impact the measurement and subsequent display of TV. A software change of the TV measuring algorithm of the SERVO-i® (Getinge, Solna, Sweden) at the PICU of the University Medical Centre Utrecht was studied in a prospective cohort. It showed, as example, a clinically significant impact of 8% difference in reported TV. Design choices in both the hardware and software of mechanical ventilators can have a clinically relevant impact on the measurement of tidal volume. In our search for the optimal TV for lung-protective ventilation, such choices should be taken into account.

Case Report: Respiratory Management With a 47-Day ECMO Support for a Critical Patient With COVID-19

This paper reports a complete case of severe acute respiratory distress syndrome (ARDS) caused by coronavirus disease 2019 (COVID-19), who presented with rapid deterioration of oxygenation during hospitalization despite escalating high-flow nasal cannulation to invasive mechanical ventilation. After inefficacy with lung-protective ventilation, positive end-expiratory pressure (PEEP) titration, prone position, we administered extracorporeal membrane oxygenation (ECMO) as a salvage respiratory support with ultra-protective ventilation for 47 days and finally discharged the patient home with a good quality of life with a Barthel Index Score of 100 after 76 days of hospitalization. The purpose of this paper is to provide a clinical reference for the management of ECMO and respiratory strategy of critical patients with COVID-19-related ARDS.

Respiratory Support of Infants With Congenital Diaphragmatic Hernia

Optimisation of respiratory support of infants with congenital diaphragmatic hernia (CDH) is critical. Infants with CDH often have severe lung hypoplasia and abnormal development of their pulmonary vasculature, leading to ventilation perfusion mismatch. It is vital that lung protective ventilation strategies are employed during both initial stabilisation and post-surgical repair to avoid ventilator induced lung damage and oxygen toxicity to prevent further impairment to an already diminished gas-exchanging environment. There is a lack of robust evidence for the routine use of surfactant therapy during initial resuscitation of infants with CDH and thus administration cannot be recommended outside clinical trials. Additionally, inhaled nitric oxide has been shown to have no benefit in reducing the mortality rates of infants with CDH. Other therapeutic agents which beneficially act on pulmonary hypertension are currently being assessed in infants with CDH in randomised multicentre trials. The role of novel ventilatory modalities such as closed loop automated oxygen control, liquid ventilation and heliox therapy may offer promise for infants with CDH, but the benefits need to be determined in appropriately designed clinical trials.

COVID-19-associated acute respiratory distress syndrome versus classical acute respiratory distress syndrome (a narrative review)

Coronavirus disease 2019 (COVID-19), caused by the novel coronavirus, Severe Acute Respiratory Syndrome-Coronavi- rus-2 (SARS-CoV-2), led to the ongoing global public health crisis. Existing clinical data suggest that COVID-19 patients with acute respiratory distress syndrome (ARDS) have worse outcomes and increased risk of intensive care unit (ICU) admission. The rapid increase in the numbers of patients requiring ICU care may imply a sudden and major challenge for affected health care systems. In this narrative review, we aim to summarize current knowledge of pathophysiology, clinical and morphological characteristics of COVID-19-associated ARDS and ARDS caused by other factors (classical ARDS) as defined by Berlin criteria, and therefore to elucidate the differences, which can affect clinical management of COVID-19-as- sociated ARDS. Fully understanding the characteristics of COVID-19-associated ARDS will help identify its early progres- sion and tailor the treatment, leading to improved prognosis in severe cases and reduced mortality. The notable mechanisms of COVID-19-associated ARDS include severe pulmonary infiltration/edema and inflammation, leading to impaired alveolar homeostasis, alteration of pulmonary physiology resulting in pulmonary fibrosis, endothelial inflammation and vascular thrombosis. Despite some distinct differences between COVID-19-associated ARDS and classical ARDS as defined by Ber- lin criteria, general treatment principles, such as lung-protective ventilation and rehabilitation concepts should be applied whenever possible. At the same time, ventilatory settings for COVID-19-associated ARDS require to be adapted in individ- ual cases, depending on respiratory mechanics, recruitability and presentation timing.