A Retrospective Observational Study to Analyze Recruitment Paradigms in the Treatment of Hypoxemic COVID-19 Patients Admitted in the Intensive Care Unit of a Tertiary Care Institute in India

Introduction: This retrospective study attempted to assess the recruitability of the lungs that were affected by acute respiratory distress syndrome (ARDS) due to COVID-19. This was done with the combined use of transpulmonary pressure monitoring (to limit the stress), measurement of end-expiratory lung volume (EELV) (to measure the actual volume gain and be within limits of strain), electrical impedance tomography (EIT), and compliance (to diagnose overdistension). Recruitment was judged clinically by an increase in the SpO2 values. Methods: Retrospective data from the charts and progress sheets were collected from 27 patients admitted to the intensive care unit (between February 2021 and June 2021) with a ratio of arterial Partial pressure of oxygen (PaO2 in mmHg) to fractional inspired oxygen (FiO2) < 150 (i.e., PaO2/FiO2 < 150) with a diagnosis of ARDS. The esophageal pressure was monitored using the polyfunctional nasogastric tube (Nutrivent (TM)). The end-expiratory volume was measured using the Carescape R860 (GE Healthcare) by the nitrogen multiple breath wash-out/wash-in (EELV) at a positive end-expiratory pressure of 5. EIT measurements were performed using the Pulmo Vista 500. We performed a recruitment maneuver using the "staircase maneuver. " Results: As per the results of our study, we found that almost 2/3rd (66.7%) of the patients affected with COVID lungs affected with ARDS were recruitable. Conclusion: The results of our study again make us believe that majority of COVID-19 lungs affected with ARDS may be recruitable in the earlier stage of the illness (within the 1st week of ARDS). Thus, in such patients, safe, monitored lung recruitment should be attempted to improve oxygenation rather than directly proning the patient, which is fraught with its own set of complications.

Severe Acute Respiratory Distress Syndrome (ARDS) or Severely Increased Chest Wall Elastance?

Esophageal manometry can be used to calculate transpulmonary pressures and optimize ventilator settings accordingly. We present the case of a 31-year-old male patient with ataxia-telangiectasia (Louis-Bar syndrome) and a BMI of 20 kg/m2, admitted to our intensive care unit for coronavirus disease 2019 (COVID-19) pneumonia. The patient soon required mechanical ventilation; however, there was very poor respiratory system compliance. Cholecystitis complicated the clinical course, and veno-venous extracorporeal membrane oxygenation (ECMO) was initiated as gas exchange deteriorated. Esophageal manometry was introduced and revealed severely increased intrathoracic pressure and chest wall elastance.

Personalized mechanical ventilation in acute respiratory distress syndrome.

A personalized mechanical ventilation approach for patients with adult respiratory distress syndrome (ARDS) based on lung physiology and morphology, ARDS etiology, lung imaging, and biological phenotypes may improve ventilation practice and outcome. However, additional research is warranted before personalized mechanical ventilation strategies can be applied at the bedside. Ventilatory parameters should be titrated based on close monitoring of targeted physiologic variables and individualized goals. Although low tidal volume (VT) is a standard of care, further individualization of VT may necessitate the evaluation of lung volume reserve (e.g., inspiratory capacity). Low driving pressures provide a target for clinicians to adjust VT and possibly to optimize positive end-expiratory pressure (PEEP), while maintaining plateau pressures below safety thresholds. Esophageal pressure monitoring allows estimation of transpulmonary pressure, but its use requires technical skill and correct physiologic interpretation for clinical application at the bedside. Mechanical power considers ventilatory parameters as a whole in the optimization of ventilation setting, but further studies are necessary to assess its clinical relevance. The identification of recruitability in patients with ARDS is essential to titrate and individualize PEEP. To define gas-exchange targets for individual patients, clinicians should consider issues related to oxygen transport and dead space. In this review, we discuss the rationale for personalized approaches to mechanical ventilation for patients with ARDS, the role of lung imaging, phenotype identification, physiologically based individualized approaches to ventilation, and a future research agenda.

Oesophageal balloon positioning by echocardiography to guide positive pressure ventilation.

Understanding the respiratory mechanics of ARDS patients is crucial to avoid ventilator-induced lung injury (VILI), and this is much more challenging if not only lung compliance is altered but the whole compliance of the respiratory system is abnormal, as in obese patients. We face this problem daily in the ICU, and to optimize ventilation, we estimate respiratory mechanics using an oesophageal balloon. The balloon position is crucial to assess reliable values. In the present technical note, we describe the use of echocardiography to confirm the correct position of this instrument.

Transpulmonary pressure measurements and lung mechanics in patients with early ARDS and SARS-CoV-2.

PURPOSE: Acute Respiratory Distress Syndrome (ARDS) secondary to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has demonstrated variable oxygenation and respiratory-system mechanics without investigation of transpulmonary and chest-wall mechanics. This study describes lung, chest wall and respiratory-system mechanics in patients with SARS-CoV-2 and ARDS. METHODS: Data was collected from forty patients with confirmed SARS-CoV-2 and ARDS at Beth Israel Deaconess Medical Center in Boston, Massachusetts. Esophageal balloons were placed to estimate pleural and transpulmonary pressures. Clinical characteristics, respiratory-system, transpulmonary, and chest-wall mechanics were measured over the first week. RESULTS: Patients had moderate-severe ARDS (PaO2/FiO2 123[98-149]) and were critically ill (APACHE IV 108 [94-128] and SOFA 12 [11-13]). PaO2/FiO2 improved over the first week (150 mmHg [122.9-182] to 185 mmHg [138-228] (p = 0.035)). Respiratory system (30-35 ml/cm H2O), lung (40-50 ml/cm H2O) and chest wall (120-150 ml/cm H2O) compliance remained similar over the first week. Elevated basal pleural pressures correlated with BMI. Patients required prolonged mechanical ventilation (14.5 days [9.5-19.0]), with a mortality of 32.5%. CONCLUSIONS: Patients displayed normal chest-wall mechanics, with increased basal pleural pressure. Respiratory system and lung mechanics were similar to known existing ARDS cohorts. The wide range of respiratory system mechanics illustrates the inherent heterogeneity that is consistent with typical ARDS.

Non-invasive method to detect high respiratory effort and transpulmonary driving pressures in COVID-19 patients during mechanical ventilation.

BACKGROUND: High respiratory drive in mechanically ventilated patients with spontaneous breathing effort may cause excessive lung stress and strain and muscle loading. Therefore, it is important to have a reliable estimate of respiratory effort to guarantee lung and diaphragm protective mechanical ventilation. Recently, a novel non-invasive method was found to detect excessive dynamic transpulmonary driving pressure (∆PL) and respiratory muscle pressure (Pmus) with reasonable accuracy. During the Coronavirus disease 2019 (COVID-19) pandemic, it was impossible to obtain the gold standard for respiratory effort, esophageal manometry, in every patient. Therefore, we investigated whether this novel non-invasive method could also be applied in COVID-19 patients. METHODS: ∆PL and Pmus were derived from esophageal manometry in COVID-19 patients. In addition, ∆PL and Pmus were computed from the occlusion pressure (∆Pocc) obtained during an expiratory occlusion maneuver. Measured and computed ∆PL and Pmus were compared and discriminative performance for excessive ∆PL and Pmus was assessed. The relation between occlusion pressure and respiratory effort was also assessed. RESULTS: Thirteen patients were included. Patients had a low dynamic lung compliance [24 (20-31) mL/cmH2O], high ∆PL (25 ± 6 cmH2O) and high Pmus (16 ± 7 cmH2O). Low agreement was found between measured and computed ∆PL and Pmus. Excessive ∆PL > 20 cmH2O and Pmus > 15 cmH2O were accurately detected (area under the receiver operating curve (AUROC) 1.00 [95% confidence interval (CI), 1.00-1.00], sensitivity 100% (95% CI, 72-100%) and specificity 100% (95% CI, 16-100%) and AUROC 0.98 (95% CI, 0.90-1.00), sensitivity 100% (95% CI, 54-100%) and specificity 86% (95% CI, 42-100%), respectively). Respiratory effort calculated per minute was highly correlated with ∆Pocc (for esophageal pressure time product per minute (PTPes/min) r2 = 0.73; P = 0.0002 and work of breathing (WOB) r2 = 0.85; P < 0.0001). CONCLUSIONS: ∆PL and Pmus can be computed from an expiratory occlusion maneuver and can predict excessive ∆PL and Pmus in patients with COVID-19 with high accuracy.

Lung mechanics in type L CoVID-19 pneumonia: a pseudo-normal ARDS.

BACKGROUND: This study was conceived to provide systematic data about lung mechanics during early phases of CoVID-19 pneumonia, as long as to explore its variations during prone positioning. METHODS: We enrolled four patients hospitalized in the Intensive Care Unit of "M. Bufalini" hospital, Cesena (Italy); after the positioning of an esophageal balloon, we measured mechanical power, respiratory system and transpulmonary parameters and arterial blood gases every 6 hours, just before decubitus change and 1 hour after prono-supination. RESULTS: Both respiratory system and transpulmonary compliance and driving pressure confirmed the pseudo-normal respiratory mechanics of early CoVID-19 pneumonia (respectively, CRS 40.8 ml/cmH2O and DPRS 9.7 cmH2O; CL 53.1 ml/cmH2O and DPL 7.9 cmH2O). Interestingly, prone positioning involved a worsening in respiratory mechanical properties throughout time (CRS,SUP 56.3 ml/cmH2O and CRS,PR 41.5 ml/cmH2O - P 0.37; CL,SUP 80.8 ml/cmH2O and CL,PR 53.2 ml/cmH2O - P 0.23). CONCLUSIONS: Despite the severe ARDS pattern, respiratory system and lung mechanical properties during CoVID-19 pneumonia are pseudo-normal and tend to worsen during pronation. TRIAL REGISTRATION: Restrospectively registered.

Quantitative-analysis of computed tomography in COVID-19 and non COVID-19 ARDS patients: A case-control study.

PURPOSE: The aim of this study was to assess whether the computed tomography (CT) features of COVID-19 (COVID+) ARDS differ from those of non-COVID-19 (COVID-) ARDS patients. MATERIALS AND METHODS: The study is a single-center prospective observational study performed on adults with ARDS onset ≤72 h and a PaO2/FiO2 ≤ 200 mmHg. CT scans were acquired at PEEP set using a PEEP-FiO2 table with VT adjusted to 6 ml/kg predicted body weight. RESULTS: 22 patients were included, of whom 13 presented with COVID-19 ARDS. Lung weight was significantly higher in COVID- patients, but all COVID+ patients presented supranormal lung weight values. Noninflated lung tissue was significantly higher in COVID- patients (36 ± 14% vs. 26 ± 15% of total lung weight at end-expiration, p < 0.01). Tidal recruitment was significantly higher in COVID- patients (20 ± 12 vs. 9 ± 11% of VT, p < 0.05). Lung density histograms of 5 COVID+ patients with high elastance (type H) were similar to those of COVID- patients, while those of the 8 COVID+ patients with normal elastance (type L) displayed higher aerated lung fraction.