Respiratory system mechanics, gas exchange, and outcomes in mechanically ventilated patients with COVID-19-related acute respiratory distress syndrome: a systematic review and meta-analysis.

The association of respiratory mechanics, particularly respiratory system static compliance (CRS), with severity of hypoxaemia in patients with COVID-19-related acute respiratory distress syndrome (ARDS) has been widely debated, with some studies reporting distinct ARDS phenotypes based on CRS. Ascertaining whether such phenotypes exist is important, because they might indicate the need for ventilation strategies that differ from those used in patients with ARDS due to other causes. In a systematic review and meta-analysis of studies published between Dec 1, 2019, and March 14, 2022, we evaluated respiratory system mechanics, ventilator parameters, gas exchange parameters, and clinical outcomes in patients with COVID-19-related ARDS. Among 11 356 patients in 37 studies, mean reported CRS, measured close to the time of endotracheal intubation, was 35·8 mL/cm H2O (95% CI 33·9-37·8; I2=96·9%, τ2=32·6). Pooled mean CRS was normally distributed. Increasing ARDS severity (assessed by PaO2/FiO2 ratio as mild, moderate, or severe) was associated with decreasing CRS. We found no evidence for distinct CRS-based clinical phenotypes in patients with COVID-19-related ARDS, and we therefore conclude that no change in conventional lung-protective ventilation strategies is warranted. Future studies should explore the personalisation of mechanical ventilation strategies according to factors including respiratory system mechanics and haemodynamic status in patients with ARDS.

Lung function and breathing patterns in hospitalised COVID-19 survivors: a review of post-COVID-19 Clinics.

INTRODUCTION: There is relatively little published on the effects of COVID-19 on respiratory physiology, particularly breathing patterns. We sought to determine if there were lasting detrimental effect following hospital discharge and if these related to the severity of COVID-19. METHODS: We reviewed lung function and breathing patterns in COVID-19 survivors > 3 months after discharge, comparing patients who had been admitted to the intensive therapy unit (ITU) (n = 47) to those who just received ward treatments (n = 45). Lung function included spirometry and gas transfer and breathing patterns were measured with structured light plethysmography. Continuous data were compared with an independent t-test or Mann Whitney-U test (depending on distribution) and nominal data were compared using a Fisher's exact test (for 2 categories in 2 groups) or a chi-squared test (for > 2 categories in 2 groups). A p-value of < 0.05 was taken to be statistically significant. RESULTS: We found evidence of pulmonary restriction (reduced vital capacity and/or alveolar volume) in 65.4% of all patients. 36.1% of all patients has a reduced transfer factor (TLCO) but the majority of these (78.1%) had a preserved/increased transfer coefficient (KCO), suggesting an extrapulmonary cause. There were no major differences between ITU and ward lung function, although KCO alone was higher in the ITU patients (p = 0.03). This could be explained partly by obesity, respiratory muscle fatigue, localised microvascular changes, or haemosiderosis from lung damage. Abnormal breathing patterns were observed in 18.8% of subjects, although no consistent pattern of breathing pattern abnormalities was evident. CONCLUSIONS: An "extrapulmonary restrictive" like pattern appears to be a common phenomenon in previously admitted COVID-19 survivors. Whilst the cause of this is not clear, the effects seem to be similar on patients whether or not they received mechanical ventilation or had ward based respiratory support/supplemental oxygen.

Respiratory mechanics in late COVID-19 ARDS - a restrictive pattern is strongly associated with death. A cohort study.

INTRODUCTION: COVID-19 is associated with severe respiratory distress and high mortality. We investigated the evolution of the respiratory mechanics in COVID-19 acute respiratory distress syndrome (ARDS) and the occurrence of a restrictive respiratory pattern. MATERIAL AND METHODS: A retrospective, single-centre study including patients admitted to the ICU during the first wave of the pandemic (March-April 2020). RESULTS: A total of 141 consecutive patients were included. Many patients developed a restrictive pattern of respiratory mechanics during the course of the disease. Fifty-two patients died in the hospital (36.8%). In 29 cases (58% of the deceased) death was associated with a pattern of pulmonary mechanics, indicating a restrictive evolution of ARDS. Other diagnoses related to death were pulmonary embolism (n = 7, 14%), septic shock (n = 17, 33%), and other causes (n = 10, 20%), with some patients combining at least 2 of these diagnoses. In a multivariate analysis, age (OR = 1.06; 95% CI: 1.01-1.12; P = 0.029) and the administration of steroid pulses (OR = 2.7; 95% CI: 1.1-6.8; P = 0.03) were associated with the development of a restrictive pulmonary pattern and a higher level of plasmatic interleukin-6. CONCLUSIONS: COVID-19 ARDS is associated with high mortality associated with a specific pattern of respiratory mechanics and sustained activation of innate immunological response. Age and administration of high-dose steroid pulses are associated with this clinical picture.

Clinical outcomes and lung mechanics characteristics between COVID-19 and non-COVID-19-associated acute respiratory distress syndrome: a propensity score analysis of two major randomized trials. / Desfechos clínicos e características da mecânica pulmonar entre a síndrome do desconforto respiratório agudo associada à COVID-19 e a não associada à COVID-19: uma análise de escore de propensão de dois importantes ensaios randomizados.

OBJECTIVE: To compare the lung mechanics and outcomes between COVID-19-associated acute respiratory distress syndrome and non-COVID-19-associated acute respiratory distress syndrome. METHODS: We combined data from two randomized trials in acute respiratory distress syndrome, one including only COVID-19 patients and the other including only patients without COVID-19, to determine whether COVID-19-associated acute respiratory distress syndrome is associated with higher 28-day mortality than non-COVID-19 acute respiratory distress syndrome and to examine the differences in lung mechanics between these two types of acute respiratory distress syndrome. RESULTS: A total of 299 patients with COVID-19-associated acute respiratory distress syndrome and 1,010 patients with non-COVID-19-associated acute respiratory distress syndrome were included in the main analysis. The results showed that non-COVID-19 patients used higher positive end-expiratory pressure (12.5cmH2O; SD 3.2 versus 11.7cmH2O SD 2.8; p < 0.001), were ventilated with lower tidal volumes (5.8mL/kg; SD 1.0 versus 6.5mL/kg; SD 1.2; p < 0.001) and had lower static respiratory compliance adjusted for ideal body weight (0.5mL/cmH2O/kg; SD 0.3 versus 0.6mL/cmH2O/kg; SD 0.3; p = 0.01). There was no difference between groups in 28-day mortality (52.3% versus 58.9%; p = 0.52) or mechanical ventilation duration in the first 28 days among survivors (13 [IQR 5 - 22] versus 12 [IQR 6 - 26], p = 0.46). CONCLUSION: This analysis showed that patients with non-COVID-19-associated acute respiratory distress syndrome have different lung mechanics but similar outcomes to COVID-19-associated acute respiratory distress syndrome patients. After propensity score matching, there was no difference in lung mechanics or outcomes between groups.

OBJETIVO: Comparar a mecânica pulmonar e os desfechos entre a síndrome do desconforto respiratório agudo associada à COVID-19 e a síndrome do desconforto respiratório agudo não associada à COVID-19. MÉTODOS: Combinamos dados de dois ensaios randomizados sobre a síndrome do desconforto respiratório agudo, um incluindo apenas pacientes com COVID-19 e o outro incluindo apenas pacientes sem COVID-19, para determinar se a síndrome do desconforto respiratório agudo associada à COVID-19 está associada à maior mortalidade aos 28 dias do que a síndrome do desconforto respiratório agudo não associada à COVID-19 e também examinar as diferenças na mecânica pulmonar entre esses dois tipos de síndrome do desconforto respiratório agudo. RESULTADOS: Foram incluídos na análise principal 299 pacientes com síndrome do desconforto respiratório agudo associada à COVID-19 e 1.010 pacientes com síndrome do desconforto respiratório agudo não associada à COVID-19. Os resultados mostraram que os pacientes sem COVID-19 utilizaram pressão positiva expiratória final mais alta (12,5cmH2O; DP 3,2 versus 11,7cmH2O; DP 2,8; p < 0,001), foram ventilados com volumes correntes mais baixos (5,8mL/kg; DP 1,0 versus 6,5mL/kg; DP 1,2; p < 0,001) e apresentaram menor complacência respiratória estática ajustada para o peso ideal (0,5mL/cmH2O/kg; DP 0,3 versus 0,6mL/cmH2O/kg; DP 0,3; p = 0,01). Não houve diferença entre os grupos quanto à mortalidade aos 28 dias (52,3% versus 58,9%; p = 0,52) ou à duração da ventilação mecânica nos primeiros 28 dias entre os sobreviventes (13 [IQ 5 - 22] dias versus 12 [IQ 6 - 26] dias; p = 0,46). CONCLUSÃO: Esta análise mostrou que os pacientes com síndrome do desconforto respiratório agudo não associada à COVID-19 têm mecânica pulmonar diferente, mas desfechos semelhantes aos dos pacientes com síndrome do desconforto respiratório agudo associada à COVID-19. Após pareamento por escore de propensão, não houve diferença na mecânica pulmonar e nem nos desfechos entre os grupos.

Association of radiological lung pattern and respiratory mechanics with potential for lung recruitment in patients with COVID-ARDS: a retrospective cohort study.

BACKGROUND: The ventilatory management of COVID-ARDS is controversial, especially with regard to the different subtypes and associated PEEP titration. A higher PEEP may be beneficial only in patients with potential for lung recruitment. The assessment of lung recruitment may be guided by lung imaging, such as electric impedance tomography or recruitment computed tomography, but is complex and not established in routine clinical practice. Therefore, bedside identification of recruitable ARDS phenotypes can aid in PEEP titration in clinical settings. METHODS: In this retrospective consecutive cohort study in 40 patients with moderate-to-severe COVID-ARDS, we assessed lung recruitment using the recruitment-to-inflation ratio (R/I) in moderate-to-severe COVID-ARDS. Evidence of recruitment (R/I ≥ 0.5) was compared between clinical and computed tomography data. RESULTS: Of the included patients, 28 (70%) were classified as recruiters by the R/I. Lung recruitment was associated with higher compliance and was not associated with a consolidated lung pattern assessed using CT. Even in the tertile of patients with the highest compliance (37-70 ml/mbar), eight (73%) patients were classified as recruitable. Patients classified as recruitable presented a lower reticular lung pattern (2% vs. 6%, p = 0.032). CONCLUSIONS: Prediction of lung recruitment is difficult based on routine clinical data but may be improved by assessment of radiographic lung patterns. A bedside assessment of recruitment is necessary to guide clinical care. Even a high compliance may not rule out the potential for lung recruitment.

Chest wall loading during supine and prone position in patients with COVID-19 ARDS: effects on respiratory mechanics and gas exchange.

BACKGROUND: Recent reports of patients with severe, late-stage COVID-19 ARDS with reduced respiratory system compliance described paradoxical decreases in plateau pressure and increases in respiratory system compliance in response to anterior chest wall loading. We aimed to assess the effect of chest wall loading during supine and prone position in ill patients with COVID-19-related ARDS and to investigate the effect of a low or normal baseline respiratory system compliance on the findings. METHODS: This is a single-center, prospective, cohort study in the intensive care unit of a COVID-19 referral center. Consecutive mechanically ventilated, critically ill patients with COVID-19-related ARDS were enrolled and classified as higher (≥ 40 ml/cmH2O) or lower respiratory system compliance (< 40 ml/cmH2O). The study included four steps, each lasting 6 h: Step 1, supine position, Step 2, 10-kg continuous chest wall compression (supine + weight), Step 3, prone position, Step 4, 10-kg continuous chest wall compression (prone + weight). The mechanical properties of the respiratory system, gas exchange and alveolar dead space were measured at the end of each step. RESULTS: Totally, 40 patients were enrolled. In the whole cohort, neither oxygenation nor respiratory system compliance changed between supine and supine + weight; both increased during prone positioning and were unaffected by chest wall loading in the prone position. Alveolar dead space was unchanged during all the steps. In 16 patients with reduced compliance, PaO2/FiO2 significantly increased from supine to supine + weight and further with prone and prone + weight (107 ± 15.4 vs. 120 ± 18.5 vs. 146 ± 27.0 vs. 159 ± 30.4, respectively; p < 0.001); alveolar dead space decreased from both supine and prone position after chest wall loading, and respiratory system compliance significantly increased from supine to supine + weight and from prone to prone + weight (23.9 ± 3.5 vs. 30.9 ± 5.7 and 31.1 ± 5.7 vs. 37.8 ± 8.7 ml/cmH2O, p < 0.001). The improvement was higher the lower the baseline compliance. CONCLUSIONS: Unlike prone positioning, chest wall loading had no effects on respiratory system compliance, gas exchange or alveolar dead space in an unselected cohort of critically ill patients with C-ARDS. Only patients with a low respiratory system compliance experienced an improvement, with a higher response the lower the baseline compliance.

Use of a novel "Split" ventilation system in bench and porcine modeling of acute respiratory distress syndrome.

Split ventilation (using a single ventilator to ventilate multiple patients) is technically feasible. However, connecting two patients with acute respiratory distress syndrome (ARDS) and differing lung mechanics to a single ventilator is concerning. This study aimed to: (1) determine functionality of a split ventilation system in benchtop tests, (2) determine whether standard ventilation would be superior to split ventilation in a porcine model of ARDS and (3) assess usability of a split ventilation system with minimal specific training. The functionality of a split ventilation system was assessed using test lungs. The usability of the system was assessed in simulated clinical scenarios. The feasibility of the system to provide modified lung protective ventilation was assessed in a porcine model of ARDS (n = 30). In bench testing a split ventilation system independently ventilated two test lungs under conditions of varying compliance and resistance. In usability tests, a high proportion of naïve operators could assemble and use the system. In the porcine model, modified lung protective ventilation was feasible with split ventilation and produced similar respiratory mechanics, gas exchange and biomarkers of lung injury when compared to standard ventilation. Split ventilation can provide some elements of lung protective ventilation and is feasible in bench testing and an in vivo model of ARDS.

Paradoxical Positioning: Does "Head Up" Always Improve Mechanics and Lung Protection?

OBJECTIVES: Head-elevated body positioning, a default clinical practice, predictably increases end-expiratory transpulmonary pressure and aerated lung volume. In acute respiratory distress syndrome (ARDS), however, the net effect of such vertical inclination on tidal mechanics depends upon whether lung recruitment or overdistension predominates. We hypothesized that in moderate to severe ARDS, bed inclination toward vertical unloads the chest wall but adversely affects overall respiratory system compliance (C rs ). DESIGN: Prospective physiologic study. SETTING: Two medical ICUs in the United States. PATIENTS: Seventeen patients with ARDS, predominantly moderate to severe. INTERVENTION: Patients were ventilated passively by volume control. We measured airway pressures at baseline (noninclined) and following bed inclination toward vertical by an additional 15°. At baseline and following inclination, we manually loaded the chest wall to determine if C rs increased or paradoxically declined, suggestive of end-tidal overdistension. MEASUREMENTS AND MAIN RESULTS: Inclination resulted in a higher plateau pressure (supineΔ: 2.8 ± 3.3 cm H 2 O [ p = 0.01]; proneΔ: 3.3 ± 2.5 cm H 2 O [ p = 0.004]), higher driving pressure (supineΔ: 2.9 ± 3.3 cm H 2 O [ p = 0.01]; proneΔ: 3.3 ± 2.8 cm H 2 O [ p = 0.007]), and lower C rs (supine Δ: 3.4 ± 3.7 mL/cm H 2 O [ p = 0.01]; proneΔ: 3.1 ± 3.2 mL/cm H 2 O [ p = 0.02]). Following inclination, manual loading of the chest wall restored C rs and driving pressure to baseline (preinclination) values. CONCLUSIONS: In advanced ARDS, bed inclination toward vertical adversely affects C rs and therefore affects the numerical values for plateau and driving tidal pressures commonly targeted in lung protective strategies. These changes are fully reversed with manual loading of the chest wall, suggestive of end-tidal overdistension in the upright position. Body inclination should be considered a modifiable determinant of transpulmonary pressure and lung protection, directionally similar to tidal volume and positive end-expiratory pressure.

Monitoring Lung Injury Severity and Ventilation Intensity during Mechanical Ventilation.

Acute respiratory distress syndrome (ARDS) is a severe form of respiratory failure burden by high hospital mortality. No specific pharmacologic treatment is currently available and its ventilatory management is a key strategy to allow reparative and regenerative lung tissue processes. Unfortunately, a poor management of mechanical ventilation can induce ventilation induced lung injury (VILI) caused by physical and biological forces which are at play. Different parameters have been described over the years to assess lung injury severity and facilitate optimization of mechanical ventilation. Indices of lung injury severity include variables related to gas exchange abnormalities, ventilatory setting and respiratory mechanics, ventilation intensity, and the presence of lung hyperinflation versus derecruitment. Recently, specific indexes have been proposed to quantify the stress and the strain released over time using more comprehensive algorithms of calculation such as the mechanical power, and the interaction between driving pressure (DP) and respiratory rate (RR) in the novel DP multiplied by four plus RR [(4 × DP) + RR] index. These new parameters introduce the concept of ventilation intensity as contributing factor of VILI. Ventilation intensity should be taken into account to optimize protective mechanical ventilation strategies, with the aim to reduce intensity to the lowest level required to maintain gas exchange to reduce the potential for VILI. This is further gaining relevance in the current era of phenotyping and enrichment strategies in ARDS.

What is new in respiratory monitoring?

This paper provides a review of a selection of papers published in the Journal of Clinical Monitoring and Computing in 2020 and 2021 highlighting what is new within the field of respiratory monitoring. Selected papers cover work in pulse oximetry monitoring, acoustic monitoring, respiratory system mechanics, monitoring during surgery, electrical impedance tomography, respiratory rate monitoring, lung ultrasound and detection of patient-ventilator asynchrony.

Effects of Positive End-Expiratory Pressure in "High Compliance" Severe Acute Respiratory Syndrome Coronavirus 2 Acute Respiratory Distress Syndrome.

OBJECTIVES: Clinical observation suggests that early acute respiratory distress syndrome induced by the severe acute respiratory syndrome coronavirus 2 may be "atypical" due to a discrepancy between a relatively unaffected static respiratory system compliance and a significant hypoxemia. This would imply an "atypical" response to the positive end-expiratory pressure. DESIGN: Single-center, unblinded, crossover study. SETTING: ICU of Bari Policlinico Academic Hospital (Italy), dedicated to care patients with confirmed diagnosis of novel coronavirus disease 2019. PATIENTS: Eight patients with early severe acute respiratory syndrome coronavirus 2 acute respiratory distress syndrome and static respiratory compliance higher than or equal to 50 mL/cm H2O. INTERVENTIONS: We compared a "lower" and a "higher" positive end-expiratory pressure approach, respectively, according to the intervention arms of the acute respiratory distress syndrome network and the positive end-expiratory pressure setting in adults with acute respiratory distress syndrome studies. MEASUREMENTS AND MAIN RESULTS: Patients were ventilated with the acute respiratory distress syndrome network and, subsequently, with the ExPress protocol. After 1 hour of ventilation, for each protocol, we recorded arterial blood gas, respiratory mechanics, alveolar recruitment, and hemodynamic variables. Comparisons were performed with analysis of variance for repeated measures or Friedman test as appropriate. Positive end-expiratory pressure was increased from 9 ± 3.5 to 17.7 ± 1.7 cm H2O (p < 0.01). Alveolar recruitment was 450 ± 111 mL. Static respiratory system compliance decreased from 58.3 ± 7.6 mL/cm H2O to 47.4 ± 14.5 mL/cm H2O (p = 0.018) and the "stress index" increased from 0.97 ± 0.03 to 1.22 ± 0.07 (p < 0.001). The PaO2/FIO2 ratio increased from 131 ± 22 to 207 ± 41 (p < 0.001), and the PaCO2 increased from 45.9 ± 12.7 to 49.8 ± 13.2 mm Hg (p < 0.001). The cardiac index went from 3.6 ± 0.4 to 2.9 ± 0.6 L/min/m (p = 0.01). CONCLUSIONS: Our data suggest that the "higher" positive end-expiratory pressure approach in patients with severe acute respiratory syndrome coronavirus 2 acute respiratory distress syndrome and high compliance improves oxygenation and lung aeration but may result in alveolar hyperinflation and hemodynamic alterations.

Simulation to minimise patient self-inflicted lung injury: are we almost there?

Computational modelling has been used to enlighten pathophysiological issues in patients with acute respiratory distress syndrome (ARDS) using a sophisticated, integrated cardiopulmonary model. COVID-19 ARDS is a pathophysiologically distinct entity characterised by dissociation between impairment in gas exchange and respiratory system mechanics, especially in the early stages of ARDS. Weaver and colleagues used computational modelling to elucidate factors contributing to generation of patient self-inflicted lung injury, and evaluated the effects of various spontaneous respiratory efforts with different oxygenation and ventilatory support modes. Their findings indicate that mechanical forces generated in the lung parenchyma are only counterbalanced when the respiratory support mode reduces the intensity of respiratory efforts.

Respiratory decompensation with proning - when prone positioning can worsen respiratory mechanics.

Prone positioning recently gain- ed more popularity from its use in COVID-19 management. It is gene--rally considered to improve respiratory mechanics via increased lung compliance. In surgery, prone positioning is typically encountered when it is a necessity to access certain posterior anatomic structures. Though certain post-operative complications from prone positioning are well known (e.g., postoperative vision loss), the potential intraoperative complications that it can have for respiratory com-pliance and O2 saturation, in the setting of general anaesthesia, are perhaps less familiar, as only a few studies showed improved respiratory mechanics in the setting of ge-neral anaesthesia [1-3] and one study showed that prone positioning led to a 30-35% drop in respiratory compliance under general anaesthesia [4]. As the following case illustrates, proning is a critical point in the intraoperative course as it can sometimes lead to negative respiratory sequelae disrupting homeostasis.

Towards a multi-scale computer modeling workflow for simulation of pulmonary ventilation in advanced COVID-19.

Physics-based multi-scale in silico models offer an excellent opportunity to study the effects of heterogeneous tissue damage on airflow and pressure distributions in COVID-19-afflicted lungs. The main objective of this study is to develop a computational modeling workflow, coupling airflow and tissue mechanics as the first step towards a virtual hypothesis-testing platform for studying injury mechanics of COVID-19-afflicted lungs. We developed a CT-based modeling approach to simulate the regional changes in lung dynamics associated with heterogeneous subject-specific COVID-19-induced damage patterns in the parenchyma. Furthermore, we investigated the effect of various levels of inflammation in a meso-scale acinar mechanics model on global lung dynamics. Our simulation results showed that as the severity of damage in the patient's right lower, left lower, and to some extent in the right upper lobe increased, ventilation was redistributed to the least injured right middle and left upper lobes. Furthermore, our multi-scale model reasonably simulated a decrease in overall tidal volume as the level of tissue injury and surfactant loss in the meso-scale acinar mechanics model was increased. This study presents a major step towards multi-scale computational modeling workflows capable of simulating the effect of subject-specific heterogenous COVID-19-induced lung damage on ventilation dynamics.

Monitoring respiratory mechanics by oscillometry in COVID-19 patients receiving non-invasive respiratory support.

BACKGROUND: Non-invasive ventilation (NIV) has been increasingly used in COVID-19 patients. The limited physiological monitoring and the unavailability of respiratory mechanic measures, usually obtainable during invasive ventilation, is a limitation of NIV for ARDS and COVID-19 patients management. OBJECTIVES: This pilot study was aimed to evaluate the feasibility of non-invasively monitoring respiratory mechanics by oscillometry in COVID-19 patients with moderate-severe acute respiratory distress syndrome (ARDS) receiving NIV. METHOD: 15 COVID-19 patients affected by moderate-severe ARDS at the RICU (Respiratory Intensive Care Unit) of the University hospital of Cattinara, Trieste, Italy were recruited. Patients underwent oscillometry tests during short periods of spontaneous breathing between NIV sessions. RESULTS: Oscillometry proved to be feasible, reproducible and well-tolerated by patients. At admission, 8 of the 15 patients showed oscillometry parameters within the normal range which further slightly improved before discharge. At discharge, four patients had still abnormal respiratory mechanics, not exclusively linked to pre-existing respiratory comorbidities. Lung mechanics parameters were not correlated with oxygenation. CONCLUSIONS: Our results suggest that lung mechanics provide complementary information for improving patients phenotyping and personalisation of treatments during NIV in COVID 19 patients, especially in the presence of respiratory comorbidities where deterioration of lung mechanics may be less coupled with changes in oxygenation and more difficult to identify. Oscillometry may provide a valuable tool for monitoring lung mechanics in COVID 19 patients receiving NIV.

Potential for the lung recruitment and the risk of lung overdistension during 21 days of mechanical ventilation in patients with COVID-19 after noninvasive ventilation failure: the COVID-VENT observational trial.

BACKGROUND: Data on the lung respiratory mechanics and gas exchange in the time course of COVID-19-associated respiratory failure is limited. This study aimed to explore respiratory mechanics and gas exchange, the lung recruitability and risk of overdistension during the time course of mechanical ventilation. METHODS: This was a prospective observational study in critically ill mechanically ventilated patients (n = 116) with COVID-19 admitted into Intensive Care Units of Sechenov University. The primary endpoints were: «optimum¼ positive end-expiratory pressure (PEEP) level balanced between the lowest driving pressure and the highest SpO2 and number of patients with recruitable lung on Days 1 and 7 of mechanical ventilation. We measured driving pressure at different levels of PEEP (14, 12, 10 and 8 cmH2O) with preset tidal volume, and with the increase of tidal volume by 100 ml and 200 ml at preset PEEP level, and calculated static respiratory system compliance (CRS), PaO2/FiO2, alveolar dead space and ventilatory ratio on Days 1, 3, 5, 7, 10, 14 and 21. RESULTS: The «optimum¼ PEEP levels on Day 1 were 11.0 (10.0-12.8) cmH2O and 10.0 (9.0-12.0) cmH2O on Day 7. Positive response to recruitment was observed on Day 1 in 27.6% and on Day 7 in 9.2% of patients. PEEP increase from 10 to 14 cmH2O and VT increase by 100 and 200 ml led to a significant decrease in CRS from Day 1 to Day 14 (p < 0.05). Ventilatory ratio was 2.2 (1.7-2,7) in non-survivors and in 1.9 (1.6-2.6) survivors on Day 1 and decreased on Day 7 in survivors only (p < 0.01). PaO2/FiO2 was 105.5 (76.2-141.7) mmHg in non-survivors on Day 1 and 136.6 (106.7-160.8) in survivors (p = 0.002). In survivors, PaO2/FiO2 rose on Day 3 (p = 0.008) and then between Days 7 and 10 (p = 0.046). CONCLUSION: Lung recruitability was low in COVID-19 and decreased during the course of the disease, but lung overdistension occurred at «intermediate¼ PEEP and VT levels. In survivors gas exchange improvements after Day 7 mismatched CRS. TRIAL REGISTRATION: ClinicalTrials.gov, NCT04445961 . Registered 24 June 2020-Retrospectively registered.

Investigations on the Respiratory Function in COVID-19 Patients: A Prospective Cohort Study.

INTRODUCTION: Coronavirus disease 2019 (COVID-19) is a global public health crisis. However, whether it can cause respiratory dysfunction or physical and psychological disorders in patients remains unknown. Thus, this study was conducted to investigate the respiratory function, activities of daily living, quality of life, and mental status of patients with COVID-19. Participants and outcomes. Data was collected from the follow-up of eligible patients who attended the fever clinic of three hospitals in Jiangxi Province, from March to May 2020. The outcomes included respiratory muscle function, degree of dyspnea, aerobic capacity, activities of daily living, quality of life, and mental status. RESULTS: A total of 139 patients (72 men and 67 women) were included in this study. The proportions of mild, moderate, severe, and critical cases of COVID-19 were 7.1% (10 cases), 68.3% (95 cases), 20.1% (28 cases), and 4.2% (6 cases), respectively. The rates of abnormal maximal inspiratory pressure were 10.0%, 25.2%, 25.0%, and 16.7%, respectively. There were 50%, 65.3%, 50%, and 66.7% of the patients with abnormal dyspnea in the four clinical classifications, respectively. Patients generally show a decline in quality of life, anxiety, and depression symptoms. CONCLUSIONS: Respiratory dysfunction, decreased quality of life, and psychological disorders were present in each clinical classification of COVID-19. Therefore, it is necessary to carry out respiratory rehabilitation and psychological intervention for COVID-19 patients.

Respiratory Mechanics.

Today's management of the ventilated patient still relies on the measurement of old parameters such as airway pressures and flow. Graphical presentations reveal the intricacies of patient-ventilator interactions in times of supporting the patient on the ventilator instead of fully ventilating the heavily sedated patient. This opens a new pathway for several bedside technologies based on basic physiologic knowledge; however, it may increase the complexity of measurements. The spread of the COVID-19 infection has confronted the anesthesiologist and intensivist with one of the most severe pulmonary pathologies of the last decades. Optimizing the patient at the bedside is an old and newly required skill for all physicians in the intensive care unit, supported by mobile technologies such as lung ultrasound and electrical impedance tomography. This review summarizes old knowledge and presents a brief insight into extended monitoring options.