Impact of Air Transport on SpO2/FiO2 among Critical COVID-19 Patients during the First Pandemic Wave in France

During the first wave of the COVID-19 pandemic, some French regions were more affected than others. To relieve those areas most affected, the French government organized transfers of critical patients, notably by plane or helicopter. Our objective was to investigate the impact of such transfers on the pulse oximetric saturation (SpO2)-to-inspired fraction of oxygen (FiO2) ratio among transferred critical patients with COVID-19. We conducted a retrospective study on medical and paramedical records. The primary endpoint was the change in SpO2/FiO2 during transfers. Thirty-eight patients were transferred between 28 March and 5 April 2020, with a mean age of 62.4 years and a mean body mass index of 29.8 kg/m2. The population was 69.7% male, and the leading medical history was hypertension (42.1%), diabetes (34.2%), and dyslipidemia (18.4%). Of 28 patients with full data, we found a decrease of 28.9 points in SpO2/FiO2 (95% confidence interval, 5.8 to 52.1, p = 0.01) between the starting and the arrival intensive care units (SpO2/FiO2, 187.3 ± 61.3 and 158.4 ± 62.8 mmHg, respectively). Air medical transfers organized to relieve intensive care unit teams under surging conditions during the first COVID wave were associated with significant decreases in arterial oxygenation.

The Influences of three Intraoperative Ventilatory Strategies on Arterial Oxygenation in Morbid Obese Patients Undergoing Laparoscopic Bariatric Surgery

Background: Maintaining satisfactory ventilation for obese patients undergoing bariatric surgery frequently poses a challenge for anesthetists. The optimal ventilation strategy during pneumoperitoneum remains obscure in obese patients. In this study, we investigated the effect of conventional ventilation, inverse ratio ventilation (IRV) and alveolar recruitment maneuver (RM) on arterial oxygenation, lung mechanics and hemodynamics in morbid obese patients undergoing laparoscopic bariatric surgery. Methods: 105 adult obese patients scheduled for elective laparoscopic bariatric surgery were randomly allocated into three groups: Conventional ratio ventilation (I:E ratio was 1:2, PEEP 5 cmH2O and no RM), Inverse Ratio Group (IRVG) (I:E ratio was 2:1 and PEEP 5 cmH2O and No RM ) and Recruitment Maneuver Group (RMG) ( RM was done and I:E ratio was 1:2). Arterial blood gases and respiratory mechanics were recorded after induction of anesthesia (T1), 5 minutes (T2), 30 minutes (T3), 60 minutes (T4) after the beginning of pneumoperitoneum and at the end of the surgery (T5). Cardiac output was recorded at (T1), (T2), (T3) and (T5). Results: At T3, T4 and T5, arterial oxygen tension was higher in RMG than IRVG than CG (P ˂ 0.05). At T3, T4 and T5, the mean airway pressure and dynamic compliance (Cdyn) were significantly higher in IRVG and RMG compared with CG (P ˂ 0.05) while at those times, the mean air way pressure and Cdyn in IRVG and RMG were comparable. Cardiac output result were comparable between all groups throughout the study period (P ˃ 0.05). Conclusions: RM and IRV had provided better arterial oxygenation and respiratory mechanics compared to conventional ventilation in morbid obese patients undergoing laparoscopic bariatric surgery. However, RM had better gas exchange than IRV.

Hepatopulmonary Syndrome with Finger Clubbing

Hepatopulmonary syndrome is a rare lung complication of liver cirrhosis, caused by pulmonary microvascular vasodilation that induces abnormal arterial oxygenation. Typical findings on physical examination are finger clubbing and cyanosis. Dyspnea is a common symptom and is worse in the upright position. Contrast echocardiography is a useful diagnostic test. Currently, the only effective treatment is liver transplantation. We report the case of a woman with cirrhosis who has hepatopulmonary syndrome with finger clubbing, confirmed by contrast echocardiography. The patient is waiting for a liver transplant.

Novel criteria to classify ARDS severity using a machine learning approach

Background Usually, arterial oxygenation in patients with the acute respiratory distress syndrome (ARDS) improves substantially by increasing the level of positive end-expiratory pressure (PEEP). Herein, we are proposing a novel variable [PaO2/(FiO2xPEEP) or P/FPE] for PEEP ≥ 5 to address Berlin’s definition gap for ARDS severity by using machine learning (ML) approaches. Methods We examined P/FPE values delimiting the boundaries of mild, moderate, and severe ARDS. We applied ML to predict ARDS severity after onset over time by comparing current Berlin PaO2/FiO2 criteria with P/FPE under three different scenarios. We extracted clinical data from the first 3 ICU days after ARDS onset (N = 2738, 1519, and 1341 patients, respectively) from MIMIC-III database according to Berlin criteria for severity. Then, we used the multicenter database eICU (2014–2015) and extracted data from the first 3 ICU days after ARDS onset (N = 5153, 2981, and 2326 patients, respectively). Disease progression in each database was tracked along those 3 ICU days to assess ARDS severity. Three robust ML classification techniques were implemented using Python 3.7 (LightGBM, RF, and XGBoost) for predicting ARDS severity over time. Results P/FPE ratio outperformed PaO2/FiO2 ratio in all ML models for predicting ARDS severity after onset over time (MIMIC-III: AUC 0.711–0.788 and CORR 0.376–0.566; eICU: AUC 0.734–0.873 and CORR 0.511–0.745). Conclusions The novel P/FPE ratio to assess ARDS severity after onset over time is markedly better than current PaO2/FiO2 criteria. The use of P/FPE could help to manage ARDS patients with a more precise therapeutic regimen for each ARDS category of severity.

The Fundamentals of Respiratory Physiology to Manage the COVID-19 Pandemic: An Overview

The growing coronavirus disease (COVID-19) crisis has stressed worldwide healthcare systems probably as never before, requiring a tremendous increase of the capacity of intensive care units to handle the sharp rise of patients in critical situation. Since the dominant respiratory feature of COVID-19 is worsening arterial hypoxemia, eventually leading to acute respiratory distress syndrome (ARDS) promptly needing mechanical ventilation, a systematic recourse to intubation of every hypoxemic patient may be difficult to sustain in such peculiar context and may not be deemed appropriate for all patients. Then, it is essential that caregivers have a solid knowledge of physiological principles to properly interpret arterial oxygenation, to intubate at the satisfactory moment, to adequately manage mechanical ventilation, and, finally, to initiate ventilator weaning, as safely and as expeditiously as possible, in order to make it available for the next patient. Through the expected mechanisms of COVID-19-induced hypoxemia, as well as the notion of silent hypoxemia often evoked in COVID-19 lung injury and its potential parallelism with high altitude pulmonary edema, from the description of hemoglobin oxygen affinity in patients with severe COVID-19 to the interest of the prone positioning in order to treat severe ARDS patients, this review aims to help caregivers from any specialty to handle respiratory support following recent knowledge in the pathophysiology of respiratory SARS-CoV-2 infection.