Obesity and diabetes: similar respiratory mechanical but different gas exchange defects

The Effects of Diabetes and Being Overweight on Patients with Post-COVID-19 Syndrome

In the aftermath of the COVID-19 pandemic, post-COVID-19 syndrome (PCS) remains a challenge and may continue to pose a major health problem in the future. Moreover, the influences of type 2 diabetes and being overweight on PCS remain unclear. This study aimed to assess these influences. We performed an observational study from October 2020 to July 2022, which included 466 patients (269 males and 197 females) with a median age of 65. They were hospitalized due to COVID-19 pneumonia and had persistent symptoms after 1 month of COVID-19 infection. The patients were divided into four groups according to the study objectives: patients with type 2 diabetes, overweight patients, overweight patients with type 2 diabetes, and average-weight patients without type 2 diabetes. The clinical and demographic data collected during hospitalization and regular visits to the Community Healthcare Center dr. Adolf Drolc Maribor were analyzed. Our results showed that type 2 diabetes patients had more difficult courses of treatment and longer hospitalizations. Moreover, more type 2 diabetes patients underwent rehabilitation than the other study groups. The prevailing symptoms of our patients with PCS were dyspnea and fatigue, mostly among female patients with type 2 diabetes. Our study also showed that more women with type 2 diabetes and overweight women with type 2 diabetes suffered from secondary infections. Furthermore, more overweight patients were treated in the intensive care unit than patients from the other groups. However, our study showed an interesting result: patients with type 2 diabetes had the shortest PCS durations. Type 2 diabetes and being overweight are risk factors for PCS onset and prolonged duration. Therefore, our data that revealed a shorter duration of PCS in type 2 diabetes patients than the other investigated groups was unexpected. We believe that answering the questions arising from our unexpected results will improve PCS treatment in general.

Monocyte adhesive hyaluronan matrix induced by hyperglycemia in diabetic lung injuries

Infiltrated pre-inflammatory monocytes and macrophages have important roles in the induction of diabetic lung injuries, but the mechanism mediating their infiltration is still unclear. Here, we showed that airway smooth muscle cells (SMCs) activated monocyte adhesion in response to hyperglycemic glucose (25.6 mM) by significantly increasing hyaluronan (HA) in the cell matrix, with concurrent 2- to 4-fold increases in adhesion of U937 monocytic-leukemic cells. The HA-based structures were attributed directly to the high-glucose and not to increased extracellular osmolality, and they required growth stimulation of SMCs by serum. Treatment of SMCs with heparin in high-glucose induces synthesis of a much larger HA matrix, consistent with our observations in the glomerular SMCs. Further, we observed increases in tumor necrosis factor-stimulated gene-6 (TSG-6) expression in high-glucose and high-glucose plus heparin cultures, and the heavy chain (HC)-modified HA structures existed on the monocyte-adhesive cable structures in high-glucose and in high-glucose plus heparin-treated SMC cultures. Interestingly, these HC-modified HA structures were unevenly distributed along the HA cables. Further, the in vitro assay with recombinant human TSG-6 and the HA14 oligo showed that heparin has no inhibitory activity on the TSG-6-induced HC-transfer to HA, consistent with the results from SMC cultures. These results support the hypothesis that hyperglycemia in airway smooth muscle induces the synthesis of a HA matrix that recruits inflammatory cells and establishes a chronic inflammatory process and fibrosis that lead to diabetic lung injuries.

Risk factors and predictive model for pulmonary complications in patients transferred to ICU after hepatectomy

OBJECTIVE

Postoperative pulmonary complications (PPCs) seriously harm the recovery and prognosis of patients undergoing surgery. However, its related risk factors in critical patients after hepatectomy have been rarely reported. This study aimed at analyzing the factors related to PPCs in critical adult patients after hepatectomy and create a nomogram for prediction of the PPCs.

METHODS

503 patients' data were collected form the Peking University People's Hospital. Multivariate logistic regression analysis was used to identify independent risk factors to derive the nomogram. Nomogram's discriminatory ability was assessed using the area under the receiver operating characteristic curve (AUC), and calibration was assessed using the Hosmer-Lemeshow goodness-of-fit test and calibration curve.

RESULTS

The independent risk factor for PPCs are advanced age (odds ratio [OR] = 1.026; P = 0.008), higher body mass index (OR = 1.139; P < 0.001), lower preoperative serum albumin level (OR = 0.961; P = 0.037), and intensive care unit first day infusion volume (OR = 1.152; P = 0.040). And based on this, we created a nomogram to predict the occurrence of PPCs. Upon assessing the nomogram's predictive ability, the AUC for the model was 0.713( 95% CI: 0.668-0.758, P<0.001). The Hosmer-Lemeshow test (P = 0.590) and calibration curve showed good calibration for the prediction of PPCs.

CONCLUSIONS

The prevalence and mortality of postoperative pulmonary complications in critical adult patients after hepatectomy are high. Advanced age, higher body mass index, lower preoperative serum albumin and intensive care unit first day infusion volume were found to be significantly associated with PPCs. And we created a nomogram model which can be used to predict the occurrence of PPCs.

Effect of body position on the redistribution of regional lung aeration during invasive and non-invasive ventilation of COVID-19 patients

Severe COVID-19-related acute respiratory distress syndrome (C-ARDS) requires mechanical ventilation. While this intervention is often performed in the prone position to improve oxygenation, the underlying mechanisms responsible for the improvement in respiratory function during invasive ventilation and awake prone positioning in C-ARDS have not yet been elucidated. In this prospective observational trial, we evaluated the respiratory function of C-ARDS patients while in the supine and prone positions during invasive (n = 13) or non-invasive ventilation (n = 15). The primary endpoint was the positional change in lung regional aeration, assessed with electrical impedance tomography. Secondary endpoints included parameters of ventilation and oxygenation, volumetric capnography, respiratory system mechanics and intrapulmonary shunt fraction. In comparison to the supine position, the prone position significantly increased ventilation distribution in dorsal lung zones for patients under invasive ventilation (53.3 ± 18.3% vs. 43.8 ± 12.3%, percentage of dorsal lung aeration ± standard deviation in prone and supine positions, respectively; p = 0.014); whereas, regional aeration in both positions did not change during non-invasive ventilation (36.4 ± 11.4% vs. 33.7 ± 10.1%; p = 0.43). Prone positioning significantly improved the oxygenation both during invasive and non-invasive ventilation. For invasively ventilated patients reduced intrapulmonary shunt fraction, ventilation dead space and respiratory resistance were observed in the prone position. Oxygenation is improved during non-invasive and invasive ventilation with prone positioning in patients with C-ARDS. Different mechanisms may underly this benefit during these two ventilation modalities, driven by improved distribution of lung regional aeration, intrapulmonary shunt fraction and ventilation-perfusion matching. However, the differences in the severity of C-ARDS may have biased the sensitivity of electrical impedance tomography when comparing positional changes between the protocol groups.Trial registration: ClinicalTrials.gov (NCT04359407) and Registered 24 April 2020, https://clinicaltrials.gov/ct2/show/NCT04359407 .

Exaggerated Ventilator-Induced Lung Injury in an Animal Model of Type 2 Diabetes Mellitus: A Randomized Experimental Study

Although ventilator-induced lung injury (VILI) often develops after prolonged mechanical ventilation in normal lungs, pulmonary disorders may aggravate the development of adverse symptoms. VILI exaggeration can be anticipated in type 2 diabetes mellitus (T2DM) due to its adverse pulmonary consequences. Therefore, we determined whether T2DM modulates VILI and evaluated how T2DM therapy affects adverse pulmonary changes. Rats were randomly assigned into the untreated T2DM group receiving low-dose streptozotocin with high-fat diet (T2DM, n = 8), T2DM group supplemented with metformin therapy (MET, n = 8), and control group (CTRL, n = 8). In each animal, VILI was induced by mechanical ventilation for 4 h with high tidal volume (23 ml/kg) and low positive end-expiratory pressure (0 cmH2O). Arterial and venous blood samples were analyzed to measure the arterial partial pressure of oxygen (PaO2), oxygen saturation (SaO2), and the intrapulmonary shunt fraction (Qs/Qt). Airway and respiratory tissue mechanics were evaluated by forced oscillations. Lung histology samples were analyzed to determine injury level. Significant worsening of VILI, in terms of PaO2, SaO2, and Qs/Qt, was observed in the T2DM group, without differences in the respiratory mechanics. These functional changes were also reflected in lung injury score. The MET group showed no difference compared with the CTRL group. Gas exchange impairment without significant mechanical changes suggests that untreated diabetes exaggerates VILI by augmenting the damage of the alveolar–capillary barrier. Controlled hyperglycemia with metformin may reduce the manifestations of respiratory defects during prolonged mechanical ventilation.

LUNG AND CHEST WALL MECHANICAL PROPERTIES IN METFORMIN-TREATED AND UNTREATED MODELS OF TYPE 2 DIABETES

The adverse respiratory consequences of type-2 diabetes mellitus (T2DM) may reflect compromised lung function and/or alterations of the chest wall because of skeletal muscle stiffening. We assessed the separate contributions of these compartments to respiratory complications in diabetes and explored the effects of metformin on respiratory abnormalities. Experiments were performed in untreated rats (control, n=7), high-fat diet-fed rats receiving streptozotocin (T2DM, n=7), and metformin-treated diabetic rats (MET, n=6). Newtonian resistance, tissue damping, and elastance were separately assessed for lung and chest wall components by measuring the esophageal pressure during forced oscillations at low (0 cmH₂O), medium (3 cmH₂O), and high positive end-expiratory pressure (PEEP) (6 cmH₂O). Tissue hysteresivity was calculated as damping/elastance. Blood gas parameters were used to assess gas exchange, and lung histology was performed to characterize collagen expression. T2DM at low PEEP compromised airway and lung tissue mechanics in association with gas-exchange defects and collagen overexpression. Abnormal chest wall mechanics in T2DM was indicated only by decreased tissue hysteresivity. No difference in lung or chest wall mechanics, gas exchange, or lung histology was observed between the MET and control groups. These findings suggest the primary involvement of the pulmonary system in the respiratory consequences of T2DM, with chest wall properties only disturbed by a shift toward the dominance of elastic forces at low PEEP. The adequacy of metformin to treat the adverse respiratory consequences of diabetes was also revealed, in addition to its well-established beneficial effects on other organs.