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1.
Respir Res ; 23(1): 7, 2022 Jan 12.
Article in English | MEDLINE | ID: covidwho-1622237

ABSTRACT

BACKGROUND: The comparison of respiratory system compliance (Crs) between COVID and non-COVID ARDS patients has been the object of debate, but few studies have evaluated it when considering applied positive end expiratory pressure (PEEP), which is one of the known determinants of Crs itself. The aim of this study was to compare Crs taking into account the applied PEEP. METHODS: Two cohorts of patients were created: those with COVID-ARDS and those with non-COVID ARDS. In the whole sample the association between Crs and type of ARDS at different PEEP levels was adjusted for anthropometric and clinical variables. As secondary analyses, patients were matched for predicted functional residual capacity and the same association was assessed. Moreover, the association between Crs and type of ARDS was reassessed at predefined PEEP level of 0, 5, 10, and 15 cmH2O with a propensity score-weighted linear model. RESULTS: 367 patients were included in the study, 276 patients with COVID-ARDS and 91 with non-COVID ARDS. The association between Crs and type of ARDS was not significant in both the complete cohorts (p = 0.17) and in the matched cohorts (p = 0.92). This was true also for the propensity score weighted association at PEEP 5, 10 and 15 cmH2O, while it was statistically significant at PEEP 0 (with a median difference of 3 ml/cmH2O, which in our opinion is not clinically significant). CONCLUSIONS: The compliance of the respiratory system is similar between COVID ARDS and non-COVID ARDS when calculated at the same PEEP level and while taking into account patients' anthropometric characteristics.


Subject(s)
COVID-19/therapy , Positive-Pressure Respiration , Respiratory Distress Syndrome/therapy , Aged , Anthropometry , COVID-19/diagnosis , COVID-19/physiopathology , COVID-19/virology , Female , Functional Residual Capacity , Host-Pathogen Interactions , Humans , Lung/physiopathology , Lung/virology , Lung Compliance , Male , Middle Aged , Respiratory Distress Syndrome/diagnosis , Respiratory Distress Syndrome/physiopathology , Retrospective Studies , SARS-CoV-2/pathogenicity , Treatment Outcome
2.
Ann Acad Med Singap ; 50(9): 686-694, 2021 09.
Article in English | MEDLINE | ID: covidwho-1464249

ABSTRACT

INTRODUCTION: Acute respiratory distress syndrome (ARDS) in COVID-19 is associated with a high mortality rate, though outcomes of the different lung compliance phenotypes are unclear. We aimed to measure lung compliance and examine other factors associated with mortality in COVID-19 patients with ARDS. METHODS: Adult patients with COVID-19 ARDS who required invasive mechanical ventilation at 8 hospitals in Singapore were prospectively enrolled. Factors associated with both mortality and differences between high (<40mL/cm H2O) and low (<40mL/cm H2O) compliance were analysed. RESULTS: A total of 102 patients with COVID-19 who required invasive mechanical ventilation were analysed; 15 (14.7%) did not survive. Non-survivors were older (median 70 years, interquartile range [IQR] 67-75 versus median 61 years, IQR 52-66; P<0.01), and required a longer duration of ventilation (26 days, IQR 12-27 vs 8 days, IQR 5-15; P<0.01) and intensive care unit support (26 days, IQR 11-30 vs 11.5 days, IQR 7-17.3; P=0.01), with a higher incidence of acute kidney injury (15 patients [100%] vs 40 patients [46%]; P<0.01). There were 67 patients who had lung compliance data; 24 (35.8%) were classified as having high compliance and 43 (64.2%) as having low compliance. Mortality was higher in patients with high compliance (33.3% vs 11.6%; P=0.03), and was associated with a drop in compliance at day 7 (-9.3mL/cm H2O (IQR -4.5 to -15.4) vs 0.2mL/cm H2O (4.7 to -5.2) P=0.04). CONCLUSION: COVID-19 ARDS patients with higher compliance on the day of intubation and a longitudinal decrease over time had a higher risk of death.


Subject(s)
COVID-19 , Respiratory Distress Syndrome , Humans , Lung Compliance , Phenotype , Respiratory Distress Syndrome/epidemiology , Respiratory Distress Syndrome/therapy , SARS-CoV-2
5.
Crit Care ; 25(1): 264, 2021 07 28.
Article in English | MEDLINE | ID: covidwho-1331951

ABSTRACT

As exemplified by prone positioning, regional variations of lung and chest wall properties provide possibilities for modifying transpulmonary pressures and suggest that clinical interventions related to the judicious application of external pressure may yield benefit. Recent observations made in late-phase patients with severe ARDS caused by COVID-19 (C-ARDS) have revealed unexpected mechanical responses to local chest wall compressions over the sternum and abdomen in the supine position that challenge the clinician's assumptions and conventional bedside approaches to lung protection. These findings appear to open avenues for mechanism-defining research investigation with possible therapeutic implications for all forms and stages of ARDS.


Subject(s)
COVID-19/therapy , Lung Compliance , Prone Position , Humans , Patient Positioning , Pressure , Respiratory Distress Syndrome/virology , Respiratory Mechanics
6.
BMC Pulm Med ; 21(1): 202, 2021 Jun 17.
Article in English | MEDLINE | ID: covidwho-1274550

ABSTRACT

BACKGROUND: Mechanical power (MP) of artificial ventilation, the energy transferred to the respiratory system, is a chief determinant of adequate oxygenation and decarboxylation. Calculated MP, the product of applied airway pressure and minute ventilation, may serve as an estimate of respiratory muscle workload when switching to spontaneous breathing. The aim of the study was to assess MP's discriminatory performance in predicting successful weaning from prolonged tracheostomy ventilation. METHODS: Prospective, observational study in 130 prolonged mechanically ventilated, tracheotomized patients in a specialized weaning center. Predictive weaning outcome ability of arterial blood gas analyses and indices derived from calculated MP at beginning and end of weaning was determined in terms of area under receiver operating characteristic curve (AUROC) and measures derived from k-fold cross-validation (likelihood ratios, diagnostic odds ratio, F1 score, and Matthews correlation coefficient [MCC]). RESULTS: Forty-four (33.8%) patients experienced weaning failure. Absolute MP showed poor discrimination in predicting outcome; whereas specific MP (MP normalized to dynamic lung-thorax compliance, LTCdyn-MP) had moderate diagnostic accuracy (MCC 0.38; AUROC 0.79, 95%CI [0.71‒0.86], p < 0.001), further improved by correction for corresponding mechanical ventilation PaCO2 (termed the power index of the respiratory system [PIrs]: MCC 0.52; AUROC 0.86 [0.79‒0.92], p < 0.001). Diagnostic performance of MP indices increased over the course of weaning, with maximum accuracy immediately before completion (LTCdyn-MP: MCC 0.49; AUROC 0.86 [0.78‒0.91], p < 0.001; PIrs: MCC 0.68; AUROC 0.92 [0.86‒0.96], p < 0.001). CONCLUSIONS: MP normalized to dynamic lung-thorax compliance, a surrogate for applied power per unit of ventilated lung volume, accurately discriminated between low and high risk for weaning failure following prolonged mechanical ventilation.


Subject(s)
Lung Compliance , Lung Volume Measurements , Respiration, Artificial , Ventilator Weaning , Aged , Area Under Curve , Blood Gas Analysis , Female , Humans , Male , Middle Aged , Prognosis , Prospective Studies , ROC Curve , Respiratory Insufficiency/physiopathology , Respiratory Insufficiency/therapy
7.
Crit Care ; 25(1): 199, 2021 06 09.
Article in English | MEDLINE | ID: covidwho-1262513

ABSTRACT

BACKGROUND: Heterogeneous respiratory system static compliance (CRS) values and levels of hypoxemia in patients with novel coronavirus disease (COVID-19) requiring mechanical ventilation have been reported in previous small-case series or studies conducted at a national level. METHODS: We designed a retrospective observational cohort study with rapid data gathering from the international COVID-19 Critical Care Consortium study to comprehensively describe CRS-calculated as: tidal volume/[airway plateau pressure-positive end-expiratory pressure (PEEP)]-and its association with ventilatory management and outcomes of COVID-19 patients on mechanical ventilation (MV), admitted to intensive care units (ICU) worldwide. RESULTS: We studied 745 patients from 22 countries, who required admission to the ICU and MV from January 14 to December 31, 2020, and presented at least one value of CRS within the first seven days of MV. Median (IQR) age was 62 (52-71), patients were predominantly males (68%) and from Europe/North and South America (88%). CRS, within 48 h from endotracheal intubation, was available in 649 patients and was neither associated with the duration from onset of symptoms to commencement of MV (p = 0.417) nor with PaO2/FiO2 (p = 0.100). Females presented lower CRS than males (95% CI of CRS difference between females-males: - 11.8 to - 7.4 mL/cmH2O p < 0.001), and although females presented higher body mass index (BMI), association of BMI with CRS was marginal (p = 0.139). Ventilatory management varied across CRS range, resulting in a significant association between CRS and driving pressure (estimated decrease - 0.31 cmH2O/L per mL/cmH20 of CRS, 95% CI - 0.48 to - 0.14, p < 0.001). Overall, 28-day ICU mortality, accounting for the competing risk of being discharged within the period, was 35.6% (SE 1.7). Cox proportional hazard analysis demonstrated that CRS (+ 10 mL/cm H2O) was only associated with being discharge from the ICU within 28 days (HR 1.14, 95% CI 1.02-1.28, p = 0.018). CONCLUSIONS: This multicentre report provides a comprehensive account of CRS in COVID-19 patients on MV. CRS measured within 48 h from commencement of MV has marginal predictive value for 28-day mortality, but was associated with being discharged from ICU within the same period. Trial documentation: Available at https://www.covid-critical.com/study . TRIAL REGISTRATION: ACTRN12620000421932.


Subject(s)
COVID-19/complications , COVID-19/therapy , Lung Compliance/physiology , Respiration, Artificial/methods , Respiratory Distress Syndrome/etiology , Respiratory Distress Syndrome/therapy , Adult , Cohort Studies , Critical Care/methods , Europe , Female , Humans , Intensive Care Units , Male , Middle Aged , Retrospective Studies , Severity of Illness Index
8.
Cytokine ; 148: 155618, 2021 12.
Article in English | MEDLINE | ID: covidwho-1260707

ABSTRACT

BACKGROUND: Coronavirus disease 2019 (COVID-19) is an acute respiratory disease; approximately 5% of patients developing severe COVID-19. It is known that cytokine release is associated with disease severity, but the relationship between the different clinical phenotypes and inflammatory endotypes is not well understood. OBJECTIVE: This study investigated the association between inflammatory biomarker-based endotypes and severe COVID-19 phenotypes. METHODS: Interleukin (IL) -6, C-reactive protein (CRP), C-X-C motif chemokine (CXCL) 9, IL-18, C-C motif chemokine (CCL) 3, CCL17, IL-10, and vascular endothelial growth factor (VEGF) were measured in 57 COVID-19 patients, and their association with clinical characteristics was examined using a cluster analysis. RESULTS: Significantly higher blood levels of the eight inflammatory markers were noted in patients who developed acute respiratory distress syndrome (ARDS) than in those who did not develop ARDS (non-ARDS). Using a cluster analysis, the patient groups were classified into four clusters, of which two had patients with high IL-6 and CRP levels. In the cluster with high levels of Type 1 (T1) inflammatory markers such as CXCL9 and IL-18, 85% of the patients had ARDS, 65% of the patients developed acute kidney injury (AKI), and 78% of the patients developed pulmonary fibrosis. CONCLUSIONS: In the cluster with high levels of T1 inflammatory markers, the patients frequently suffered from tissue damage, manifested as ARDS and AKI. Our findings identified distinct T1 inflammatory endotypes of COVID-19 and suggest the importance of controlling inflammation by monitoring T1 biomarkers and treating accordingly to limit the severity of the disease.


Subject(s)
COVID-19/complications , COVID-19/physiopathology , Inflammation/pathology , Pulmonary Fibrosis/complications , Pulmonary Fibrosis/physiopathology , Aged , Biomarkers/blood , COVID-19/blood , COVID-19/virology , Cluster Analysis , Disease Progression , Female , Humans , Inflammation/blood , Inflammation/complications , Lung Compliance , Male , Middle Aged , Pulmonary Fibrosis/blood , Respiratory Distress Syndrome/blood , Respiratory Distress Syndrome/complications , SARS-CoV-2/physiology
9.
A A Pract ; 15(3): e01392, 2021 Mar 09.
Article in English | MEDLINE | ID: covidwho-1151699

ABSTRACT

Ventilator shortages occurred due to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This in vitro study evaluated the effectiveness of 3-dimensional (3D)-printed splitters and 3D-printed air flow limiters (AFL) in delivering appropriate tidal volumes (TV) to lungs with different compliances. Groups were divided according to the size of the AFL: AFL-4 was a 4-mm device, AFL-5 a 5-mm device, AFL-6 a 6-mm device, and no limiter (control). A ventilator was split to supply TV to 2 artificial lungs with different compliances. The AFL improved TV distribution.


Subject(s)
COVID-19/epidemiology , COVID-19/therapy , Emergency Medical Services/methods , Lung Compliance/physiology , Printing, Three-Dimensional , Ventilators, Mechanical/supply & distribution , Humans , Lung/physiology , Male , Tidal Volume/physiology
10.
PLoS One ; 16(1): e0245578, 2021.
Article in English | MEDLINE | ID: covidwho-1034959

ABSTRACT

COVID-19 pandemic sets the healthcare system to a shortage of ventilators. We aimed at assessing tidal volume (VT) delivery and air recirculation during expiration when one ventilator is divided into 2 test-lungs. The study was performed in a research laboratory in a medical ICU of a University hospital. An ICU (V500) and a lower-level ventilator (Elisée 350) were attached to two test-lungs (QuickLung) through a dedicated flow-splitter. A 50 mL/cmH2O Compliance (C) and 5 cmH2O/L/s Resistance (R) were set in both A and B test-lungs (A C50R5 / B C50R5, step1), A C50-R20 / B C20-R20 (step 2), A C20-R20 / B C10-R20 (step 3), and A C50-R20 / B C20-R5 (step 4). Each ventilator was set in volume and pressure control mode to deliver 800mL VT. We assessed VT from a pneumotachograph placed immediately before each lung, pendelluft air, and expiratory resistance (circuit and valve). Values are median (1st-3rd quartiles) and compared between ventilators by non-parametric tests. Between Elisée 350 and V500 in volume control VT in A/B test- lungs were 381/387 vs. 412/433 mL in step 1, 501/270 vs. 492/370 mL in step 2, 509/237 vs. 496/332 mL in step 3, and 496/281 vs. 480/329 mL in step 4. In pressure control the corresponding values were 373/336 vs. 430/414 mL, 416/185 vs. 322/234 mL, 193/108 vs. 176/ 92 mL and 422/201 vs. 481/329mL, respectively (P<0.001 between ventilators at each step for each volume). Pendelluft air volume ranged between 0.7 to 37.8 ml and negatively correlated with expiratory resistance in steps 2 and 3. The lower-level ventilator performed closely to the ICU ventilator. In the clinical setting, these findings suggest that, due to dependence of VT to C, pressure control should be preferred to maintain adequate VT at least in one patient when C and/or R changes abruptly and monitoring of VT should be done carefully. Increasing expiratory resistance should reduce pendelluft volume.


Subject(s)
COVID-19/therapy , Respiration, Artificial/methods , Ventilators, Mechanical/adverse effects , Female , Humans , Lung Compliance , Lung Volume Measurements , Male , Maximal Respiratory Pressures , Respiration, Artificial/adverse effects , Respiration, Artificial/instrumentation , Ventilators, Mechanical/standards
12.
Eur J Heart Fail ; 22(12): 2228-2237, 2020 12.
Article in English | MEDLINE | ID: covidwho-965861

ABSTRACT

AIMS: Interstitial pneumonia due to coronavirus disease 2019 (COVID-19) is often complicated by severe respiratory failure. In addition to reduced lung compliance and ventilation/perfusion mismatch, a blunted hypoxic pulmonary vasoconstriction has been hypothesized, that could explain part of the peculiar pathophysiology of the COVID-19 cardiorespiratory syndrome. However, no invasive haemodynamic characterization of COVID-19 patients has been reported so far. METHODS AND RESULTS: Twenty-one mechanically-ventilated COVID-19 patients underwent right heart catheterization. Their data were compared both with those obtained from non-mechanically ventilated paired control subjects matched for age, sex and body mass index, and with pooled data of 1937 patients with 'typical' acute respiratory distress syndrome (ARDS) from a systematic literature review. Cardiac index was higher in COVID-19 patients than in controls [3.8 (2.7-4.5) vs. 2.4 (2.1-2.8) L/min/m2 , P < 0.001], but slightly lower than in ARDS patients (P = 0.024). Intrapulmonary shunt and lung compliance were inversely related in COVID-19 patients (r = -0.57, P = 0.011) and did not differ from ARDS patients. Despite this, pulmonary vascular resistance of COVID-19 patients was normal, similar to that of control subjects [1.6 (1.1-2.5) vs. 1.6 (0.9-2.0) WU, P = 0.343], and lower than reported in ARDS patients (P < 0.01). Pulmonary hypertension was present in 76% of COVID-19 patients and in 19% of control subjects (P < 0.001), and it was always post-capillary. Pulmonary artery wedge pressure was higher in COVID-19 than in ARDS patients, and inversely related to lung compliance (r = -0.46, P = 0.038). CONCLUSIONS: The haemodynamic profile of COVID-19 patients needing mechanical ventilation is characterized by combined cardiopulmonary alterations. Low pulmonary vascular resistance, coherent with a blunted hypoxic vasoconstriction, is associated with high cardiac output and post-capillary pulmonary hypertension, that could eventually contribute to lung stiffness and promote a vicious circle between the lung and the heart.


Subject(s)
COVID-19/physiopathology , Hemodynamics/physiology , Hypertension, Pulmonary/physiopathology , Hypoxia/physiopathology , Respiratory Distress Syndrome/physiopathology , Vascular Resistance/physiology , Vasoconstriction/physiology , Aged , COVID-19/therapy , Cardiac Catheterization , Cardiac Output/physiology , Case-Control Studies , Echocardiography , Female , Humans , Hypoxia/therapy , Lung Compliance/physiology , Male , Middle Aged , Respiration, Artificial , Respiratory Distress Syndrome/therapy , Retrospective Studies , SARS-CoV-2 , Ventilation-Perfusion Ratio
13.
PLoS One ; 15(11): e0242532, 2020.
Article in English | MEDLINE | ID: covidwho-945351

ABSTRACT

BACKGROUND: The COVID-19 pandemic is stretching medical resources internationally, sometimes creating ventilator shortages that complicate clinical and ethical situations. The possibility of needing to ventilate multiple patients with a single ventilator raises patient health and safety concerns in addition to clinical conditions needing treatment. Wherever ventilators are employed, additional tubing and splitting adaptors may be available. Adjustable flow-compensating resistance for differences in lung compliance on individual limbs may not be readily implementable. By exploring a number and range of possible contributing factors using computational simulation without risk of patient harm, this paper attempts to define useful bounds for ventilation parameters when compensatory resistance in limbs of a shared breathing circuit is not possible. This desperate approach to shared ventilation support would be a last resort when alternatives have been exhausted. METHODS: A whole-body computational physiology model (using lumped parameters) was used to simulate each patient being ventilated. The primary model of a single patient with a dedicated ventilator was augmented to model two patients sharing a single ventilator. In addition to lung mechanics or estimation of CO2 and pH expected for set ventilation parameters (considerations of lung physiology alone), full physiological simulation provides estimates of additional values for oxyhemoglobin saturation, arterial oxygen tension, and other patient parameters. A range of ventilator settings and patient characteristics were simulated for paired patients. FINDINGS: To be useful for clinicians, attention has been directed to clinically available parameters. These simulations show patient outcome during multi-patient ventilation is most closely correlated to lung compliance, oxygenation index, oxygen saturation index, and end-tidal carbon dioxide of individual patients. The simulated patient outcome metrics were satisfactory when the lung compliance difference between two patients was less than 12 mL/cmH2O, and the oxygen saturation index difference was less than 2 mmHg. INTERPRETATION: In resource-limited regions of the world, the COVID-19 pandemic will result in equipment shortages. While single-patient ventilation is preferable, if that option is unavailable and ventilator sharing using limbs without flow resistance compensation is the only available alternative, these simulations provide a conceptual framework and guidelines for clinical patient selection.


Subject(s)
COVID-19/prevention & control , Computer Simulation , Patient Safety , Respiration, Artificial/instrumentation , Respiratory Mechanics/physiology , SARS-CoV-2 , Ventilators, Mechanical/supply & distribution , COVID-19/epidemiology , COVID-19/virology , Carbon Dioxide , Humans , Hydrogen-Ion Concentration , Lung/physiology , Lung Compliance , Oxygen , Pandemics , Tidal Volume/physiology
15.
Intensive Care Med ; 46(12): 2385-2396, 2020 12.
Article in English | MEDLINE | ID: covidwho-917110

ABSTRACT

In ARDS patients, the change from supine to prone position generates a more even distribution of the gas-tissue ratios along the dependent-nondependent axis and a more homogeneous distribution of lung stress and strain. The change to prone position is generally accompanied by a marked improvement in arterial blood gases, which is mainly due to a better overall ventilation/perfusion matching. Improvement in oxygenation and reduction in mortality are the main reasons to implement prone position in patients with ARDS. The main reason explaining a decreased mortality is less overdistension in non-dependent lung regions and less cyclical opening and closing in dependent lung regions. The only absolute contraindication for implementing prone position is an unstable spinal fracture. The maneuver to change from supine to prone and vice versa requires a skilled team of 4-5 caregivers. The most frequent adverse events are pressure sores and facial edema. Recently, the use of prone position has been extended to non-intubated spontaneously breathing patients affected with COVID-19 ARDS. The effects of this intervention on outcomes are still uncertain.


Subject(s)
Prone Position/physiology , Respiratory Distress Syndrome/physiopathology , Respiratory Mechanics/physiology , Humans , Lung Compliance/drug effects , Lung Compliance/physiology , Respiratory Distress Syndrome/complications
16.
Am J Respir Crit Care Med ; 202(9): 1244-1252, 2020 11 01.
Article in English | MEDLINE | ID: covidwho-901518

ABSTRACT

Rationale: A novel model of phenotypes based on set thresholds of respiratory system compliance (Crs) was recently postulated in context of coronavirus disease (COVID-19) acute respiratory distress syndrome (ARDS). In particular, the dissociation between the degree of hypoxemia and Crs was characterized as a distinct ARDS phenotype.Objectives: To determine whether such Crs-based phenotypes existed among patients with ARDS before the COVID-19 pandemic and to closely examine the Crs-mortality relationship.Methods: We undertook a secondary analysis of patients with ARDS, who were invasively ventilated on controlled modes and enrolled in a large, multinational, epidemiological study. We assessed Crs, degree of hypoxemia, and associated Crs-based phenotypic patterns with their characteristics and outcomes.Measurements and Main Results: Among 1,117 patients with ARDS who met inclusion criteria, the median Crs was 30 (interquartile range, 23-40) ml/cm H2O. One hundred thirty-six (12%) patients had preserved Crs (≥50 ml/cm H2O; phenotype with low elastance ["phenotype L"]), and 827 (74%) patients had poor Crs (<40 ml/cm H2O; phenotype with high elastance ["phenotype H"]). Compared with those with phenotype L, patients with phenotype H were sicker and had more comorbidities and higher hospital mortality (32% vs. 45%; P < 0.05). A near complete dissociation between PaO2/FiO2 and Crs was observed. Of 136 patients with phenotype L, 58 (43%) had a PaO2/FiO2 < 150. In a multivariable-adjusted analysis, the Crs was independently associated with hospital mortality (adjusted odds ratio per ml/cm H2O increase, 0.988; 95% confidence interval, 0.979-0.996; P = 0.005).Conclusions: A wide range of Crs was observed in non-COVID-19 ARDS. Approximately one in eight patients had preserved Crs. PaO2/FiO2 and Crs were dissociated. Lower Crs was independently associated with higher mortality. The Crs-mortality relationship lacked a clear transition threshold.


Subject(s)
Betacoronavirus , Coronavirus Infections/epidemiology , Lung Compliance/physiology , Pandemics , Pneumonia, Viral/epidemiology , Respiratory Distress Syndrome/physiopathology , COVID-19 , Female , Follow-Up Studies , Humans , Intensive Care Units , Male , Middle Aged , Prospective Studies , Respiratory Function Tests , SARS-CoV-2
17.
Intensive Care Med ; 46(12): 2187-2196, 2020 12.
Article in English | MEDLINE | ID: covidwho-886981

ABSTRACT

PURPOSE: To investigate whether COVID-19-ARDS differs from all-cause ARDS. METHODS: Thirty-two consecutive, mechanically ventilated COVID-19-ARDS patients were compared to two historical ARDS sub-populations 1:1 matched for PaO2/FiO2 or for compliance of the respiratory system. Gas exchange, hemodynamics and respiratory mechanics were recorded at 5 and 15 cmH2O PEEP. CT scan variables were measured at 5 cmH2O PEEP. RESULTS: Anthropometric characteristics were similar in COVID-19-ARDS, PaO2/FiO2-matched-ARDS and Compliance-matched-ARDS. The PaO2/FiO2-matched-ARDS and COVID-19-ARDS populations (both with PaO2/FiO2 106 ± 59 mmHg) had different respiratory system compliances (Crs) (39 ± 11 vs 49.9 ± 15.4 ml/cmH2O, p = 0.03). The Compliance-matched-ARDS and COVID-19-ARDS had similar Crs (50.1 ± 15.7 and 49.9 ± 15.4 ml/cmH2O, respectively) but significantly lower PaO2/FiO2 for the same Crs (160 ± 62 vs 106.5 ± 59.6 mmHg, p < 0.001). The three populations had similar lung weights but COVID-19-ARDS had significantly higher lung gas volume (PaO2/FiO2-matched-ARDS 930 ± 644 ml, COVID-19-ARDS 1670 ± 791 ml and Compliance-matched-ARDS 1301 ± 627 ml, p < 0.05). The venous admixture was significantly related to the non-aerated tissue in PaO2/FiO2-matched-ARDS and Compliance-matched-ARDS (p < 0.001) but unrelated in COVID-19-ARDS (p = 0.75), suggesting that hypoxemia was not only due to the extent of non-aerated tissue. Increasing PEEP from 5 to 15 cmH2O improved oxygenation in all groups. However, while lung mechanics and dead space improved in PaO2/FiO2-matched-ARDS, suggesting recruitment as primary mechanism, they remained unmodified or worsened in COVID-19-ARDS and Compliance-matched-ARDS, suggesting lower recruitment potential and/or blood flow redistribution. CONCLUSIONS: COVID-19-ARDS is a subset of ARDS characterized overall by higher compliance and lung gas volume for a given PaO2/FiO2, at least when considered within the timeframe of our study.


Subject(s)
COVID-19/physiopathology , Respiratory Distress Syndrome/physiopathology , Adult , Aged , Blood Gas Analysis/methods , COVID-19/therapy , Cohort Studies , Female , Humans , Intensive Care Units/organization & administration , Intensive Care Units/statistics & numerical data , Italy , Length of Stay/statistics & numerical data , Lung Compliance/physiology , Male , Middle Aged , Prospective Studies , Pulmonary Gas Exchange/physiology , Respiratory Distress Syndrome/therapy , Simplified Acute Physiology Score , Tomography, X-Ray Computed/methods
18.
Respir Care ; 65(7): 920-931, 2020 07.
Article in English | MEDLINE | ID: covidwho-840991

ABSTRACT

BACKGROUND: The overwhelming demand for mechanical ventilators due to COVID-19 has stimulated interest in using one ventilator for multiple patients (ie, multiplex ventilation). Despite a plethora of information on the internet, there is little supporting evidence and no human studies. The risk of multiplex ventilation is that ventilation and PEEP effects are largely uncontrollable and depend on the difference between patients' resistance and compliance. It is not clear whether volume control ventilation or pressure control ventilation is safer or more effective. We designed a simulation-based study to allow complete control over the relevant variables to determine the effects of various degrees of resistance-compliance imbalance on tidal volume (VT), end-expiratory lung volume (EELV), and imputed pH. METHODS: Two separate breathing simulators were ventilated with a ventilator using pressure control and volume control ventilation modes. Evidence-based lung models simulated a range of differences in resistance and compliance (6 pairs of simulated patients). Differences in VT, EELV, and imputed pH were recorded. RESULTS: Depending on differences in resistance and compliance, differences in VT ranged from 1% (with equal resistance and compliance) to 79%. Differences in EELV ranged from 2% to 109%, whereas differences in pH ranged from 0% to 5%. Failure due to excessive VT (ie, > 8 mL/kg) did not occur, but failure due to excessive EELV difference (ie, > 10%) was evident in 50% of patient pairs. There was no difference in failure rate between volume control and pressure control ventilation modes. CONCLUSIONS: These experiments confirmed the potential for markedly different ventilation and oxygenation for patients with uneven respiratory system impedances during multiplex ventilation. Three critical problems must be solved to minimize risk: (1) partitioning of inspiratory flow from the ventilator individually between the 2 patients, (2) measurement of VT delivered to each patient, and (3) provision for individual PEEP. We provide suggestions for solving these problems.


Subject(s)
Airway Resistance/physiology , Coronavirus Infections , Lung Compliance/physiology , Materials Testing/methods , Pandemics , Pneumonia, Viral , Respiration, Artificial , Betacoronavirus , COVID-19 , Computer Simulation , Coronavirus Infections/epidemiology , Coronavirus Infections/therapy , Critical Care/methods , Equipment Design , Humans , Models, Biological , Pneumonia, Viral/epidemiology , Pneumonia, Viral/therapy , Respiration, Artificial/instrumentation , Respiration, Artificial/methods , SARS-CoV-2 , Ventilators, Mechanical/standards , Ventilators, Mechanical/supply & distribution
19.
Anesthesiology ; 133(4): 892-904, 2020 10 01.
Article in English | MEDLINE | ID: covidwho-772637

ABSTRACT

BACKGROUND: During the COVID-19 pandemic, ventilator sharing was suggested to increase availability of mechanical ventilation. The safety and feasibility of ventilator sharing is unknown. METHODS: A single ventilator in pressure control mode was used with flow control valves to simultaneously ventilate two patients with different lung compliances. The system was first evaluated using high-fidelity human patient simulator mannequins and then tested for 1 h in two pairs of COVID-19 patients with acute respiratory failure. Patients were matched on positive end-expiratory pressure, fractional inspired oxygen tension, and respiratory rate. Tidal volume and peak airway pressure (PMAX) were recorded from each patient using separate independent spirometers and arterial blood gas samples drawn at 0, 30, and 60 min. The authors assessed acid-base status, oxygenation, tidal volume, and PMAX for each patient. Stability was assessed by calculating the coefficient of variation. RESULTS: The valves performed as expected in simulation, providing a stable tidal volume of 400 ml each to two mannequins with compliance ratios varying from 20:20 to 20:90 ml/cm H2O. The system was then tested in two pairs of patients. Pair 1 was a 49-yr-old woman, ideal body weight 46 kg, and a 55-yr-old man, ideal body weight 64 kg, with lung compliance 27 ml/cm H2O versus 35 ml/cm H2O. The coefficient of variation for tidal volume was 0.2 to 1.7%, and for PMAX 0 to 1.1%. Pair 2 was a 32-yr-old man, ideal body weight 62 kg, and a 56-yr-old woman, ideal body weight 46 kg, with lung compliance 12 ml/cm H2O versus 21 ml/cm H2O. The coefficient of variation for tidal volume was 0.4 to 5.6%, and for PMAX 0 to 2.1%. CONCLUSIONS: Differential ventilation using a single ventilator is feasible. Flow control valves enable delivery of stable tidal volume and PMAX similar to those provided by individual ventilators.


Subject(s)
Coronavirus Infections/therapy , Pneumonia, Viral/therapy , Respiration, Artificial/methods , Ventilators, Mechanical , Acid-Base Equilibrium , Adult , COVID-19 , Continuous Positive Airway Pressure , Coronavirus Infections/complications , Feasibility Studies , Female , Humans , Lung Compliance , Male , Manikins , Middle Aged , Oxygen/blood , Pandemics , Pneumonia, Viral/complications , Positive-Pressure Respiration , Respiration, Artificial/instrumentation , Respiratory Insufficiency/etiology , Respiratory Insufficiency/therapy , Spirometry , Tidal Volume , Ventilators, Mechanical/supply & distribution
20.
Expert Rev Respir Med ; 15(2): 183-195, 2021 02.
Article in English | MEDLINE | ID: covidwho-752298

ABSTRACT

INTRODUCTION: The exponential growth of SARS-CoV-2 virus transmission during the first months of 2020 has placed substantial pressure on most health systems around the world. The complications derived from the novel coronavirus disease (COVID-19) vary due to comorbidities, sex and age, with more than 50% of the patients requiring some level of intensive care developing acute respiratory distress syndrome (ARDS). The authors carried out an extensive and comprehensive literature review on SARS-CoV-2 infection, the clinical, pathological, and radiological presentation as well as the current treatment strategies. AREAS COVERED: Various complications caused by SARS-CoV-2 infection have been identified, the most lethal being the acute respiratory distress syndrome, caused most likely by the presence of severe immune cell response and the concomitant alveolus inflammation. The new treatment strategies are updated, and the analysis of the physiopathology is included in this review. EXPERT OPINION: ARDS is one of the most frequent complications in patients with COVID-19. Information regarding the etiology and physiopathology are still unfolding and for the prevention and amelioration, good clinical management, adequate ventilatory support and the use of systemic corticoids seem to be the most efficient way to reduce mortality and to reduce hospital lengths.


Subject(s)
COVID-19/physiopathology , Respiratory Distress Syndrome/diagnosis , Respiratory Distress Syndrome/therapy , Analgesics/therapeutic use , Antiviral Agents/therapeutic use , COVID-19/diagnosis , COVID-19/therapy , Continuous Positive Airway Pressure , Cytokines/metabolism , Drug Repositioning , Humans , Hypoxia/physiopathology , Lung/diagnostic imaging , Lung Compliance/physiology , Noninvasive Ventilation , Oxygen Inhalation Therapy , Phenotype , Respiration, Artificial , Respiratory Distress Syndrome/epidemiology , Respiratory Distress Syndrome/virology , Respiratory Function Tests , SARS-CoV-2 , Thrombosis/physiopathology , Virus Replication/physiology
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