Diaphragmatic function is enhanced in fatty and diabetic fatty rats

Cardiac and respiratory muscle responses to dietary N-acetylcysteine in rats consuming a high-saturated fat, high-sucrose diet

NEW FINDINGS

What is the central question of this study? This study addresses whether a high-fat, high-sucrose diet causes cardiac and diaphragm muscle abnormalities in male rats and whether supplementation with the antioxidant N-acetylcysteine reverses diet-induced dysfunction. What is the main finding and its importance? N-Acetylcysteine attenuated the effects of high-fat, high-sucrose diet on markers of cardiac hypertrophy and diastolic dysfunction, but neither high-fat, high-sucrose diet nor N-acetylcysteine affected the diaphragm. These results support the use of N-acetylcysteine to attenuate cardiovascular dysfunction induced by a 'Western' diet.

ABSTRACT

Individuals with overweight or obesity display respiratory and cardiovascular dysfunction, and oxidative stress is a causative factor in the general aetiology of obesity and of skeletal and cardiac muscle pathology. Thus, this preclinical study aimed to define diaphragmatic and cardiac morphological and functional alterations in response to an obesogenic diet in rats and the therapeutic potential of an antioxidant supplement, N-acetylcysteine (NAC). Young male Wistar rats consumed ad libitum a 'lean' or high-saturated fat, high-sucrose (HFHS) diet for ∼22 weeks and were randomized to control or NAC (2 mg/ml in the drinking water) for the last 8 weeks of the dietary intervention. We then evaluated diaphragmatic and cardiac morphology and function. Neither HFHS diet nor NAC supplementation affected diaphragm-specific force, peak power or morphology. Right ventricular weight normalized to estimated body surface area, left ventricular fractional shortening and posterior wall maximal shortening velocity were higher in HFHS compared with lean control animals and not restored by NAC. In HFHS rats, the elevated deceleration rate of early transmitral diastolic velocity was prevented by NAC. Our data showed that the HFHS diet did not compromise diaphragmatic muscle morphology or in vitro function, suggesting other possible contributors to breathing abnormalities in obesity (e.g., abnormalities of neuromuscular transmission). However, the HFHS diet resulted in cardiac functional and morphological changes suggestive of hypercontractility and diastolic dysfunction. Supplementation with NAC did not affect diaphragm morphology or function but attenuated some of the cardiac abnormalities in the rats receiving the HFHS diet.

Reintubation Summation Calculation: A Predictive Score for Extubation Failure in Critically Ill Patients

Objective

To derive and validate a multivariate risk score for the prediction of respiratory failure after extubation.

Patients and methods

We performed a retrospective cohort study of adult patients admitted to the intensive care unit from January 1, 2006, to December 31, 2015, who received mechanical ventilation for ≥48 h. Extubation failure was defined as the need for reintubation within 72 h after extubation. Multivariate logistic regression model coefficient estimates generated the Re-Intubation Summation Calculation (RISC) score.

Results

The 6,161 included patients were randomly divided into 2 sets: derivation (n = 3,080) and validation (n = 3,081). Predictors of extubation failure in the derivation set included body mass index <18.5 kg/m² [odds ratio (OR), 1.91; 95% CI, 1.12–3.26; P = 0.02], threshold of Glasgow Coma Scale of at least 10 (OR, 1.68; 95% CI, 1.31–2.16; P < 0.001), mean airway pressure at 1 min of spontaneous breathing trial <10 cmH₂O (OR, 2.11; 95% CI, 1.68–2.66; P < 0.001), fluid balance ≥1,500 mL 24 h preceding extubation (OR, 2.36; 95% CI, 1.87–2.96; P < 0.001), and total mechanical ventilation days ≥5 (OR, 3.94; 95% CI 3.04–5.11; P < 0.001). The C-index for the derivation and validation sets were 0.72 (95% CI, 0.70–0.75) and 0.72 (95% CI, 0.69–0.75). Multivariate logistic regression demonstrated that an increase of 1 in RISC score increased odds of extubation failure 1.6-fold (OR, 1.58; 95% CI, 1.47–1.69; P < 0.001).

Conclusion

RISC predicts extubation failure in mechanically ventilated patients in the intensive care unit using several clinically relevant variables available in the electronic medical record but requires a larger validation cohort before widespread clinical implementation.

Body mass index, blood glucose, and mortality in patients with ischemic stroke in the intensive care unit: A retrospective cohort study

BACKGROUND

Excessive BMI was associated with lower mortality after stroke. However, some believed that excessive BMI can lead to a poor prognosis because of some physiological mechanism, such as glucose metabolism disorder. Therefore, this study aims to discuss the association between mortality, BMI, and blood glucose.

MATERIALS AND METHODS

This was a retrospective observational study and all data were extracted from the Medical Information Mart for Intensive Care III database. The exposure was BMI classified into the normal weight group and the excessive weight group. The outcome concluded 30-day, 90-day, and 1-year mortality. The association between two groups and mortality was elucidated by Cox regression models, propensity score matching (PSM) and inverse probability of treatment weighting (IPTW). The underlying effect of blood glucose on the "obesity paradox" was analyzed by causal mediation analysis.

RESULTS

According to Cox regression models, a significant beneficial effect of excessive BMI in terms of mortality was observed: 30-day mortality (HR 0.57, 95% CI 0.35-0.90, P = 0.017), 90-day mortality (HR 0.53, 95% CI 0.36-0.78, P = 0.001), and 1-year mortality (HR 0.65, 95% CI 0.46-0.91, P = 0.013). After PSM and IPTW, we got a similar conclusion. The causal mediation analysis showed that the protective effect of excessive BMI on 30-day mortality reduced with the increase of blood glucose.

CONCLUSION

For ischemic stroke patients in the Intensive Care Unit, those with excessive BMI are associated with both lower short-term mortality and lower long-term mortality, while the protective effect on 30-day mortality weakened accompanied by the increase of blood glucose.

The association between outcomes and body mass index in patients with acute respiratory distress syndrome

INTRODUCTION

Limited information exists about the relationship between body mass index (BMI) and the outcome of acute respiratory distress syndrome (ARDS).

OBJECTIVE

To evaluate the hospital mortality of patients with ARDS in relation to BMI.

MATERIALS AND METHODS

We conducted a retrospective, multicenter study including patients with ARDS. ARDS was defined according to the Berlin criteria. Body weight and height were obtained to calculate BMI. The primary outcome was in-hospital mortality. Secondary outcomes were intensive care unit (ICU) mortality, invasive positive pressure ventilation (IPPV) free days within 28 days and length of stays in the ICU and hospital.

RESULTS

Among 523 patients, 28 (5%) were underweight (BMI <18.5 kg/m² ), 299 (57%) were normal weight (BMI 18.5-24.9 kg/m² ), 159 (30%) were overweight (BMI 25-29.9 kg/m² ) and 37 (7%) were obese (BMI ≥30 kg/m² ). Increasing BMI was associated with younger age (P = 0.017), hypertension (P = 0.003) and diabetes (P = 0.02). Compared with normal weight, being overweight and obese resulted in lower mortality regardless of whether in the hospital (P = 0.019) or ICU (P = 0.044). However, after risk adjustment, only obesity was associated with lower hospital mortality (OR 0.393, 95% CI 0.169-0.914, P = 0.030). With the increase of BMI, the in-hospital mortality and ICU mortality of ARDS dropped gradually (from 57.1% to 24.3%, P = 0.021, and from 53.6% to 24.3%, P = 0.035).

CONCLUSIONS

Obesity is associated with lower mortality in patients with ARDS. With the increase of BMI, the mortality of ARDS drops gradually.

Impact of experimental obesity on diaphragm structure, function, and bioenergetics

Obesity is associated with bioenergetic dysfunction of peripheral muscles; however, little is known regarding the impact of obesity on the diaphragm. We hypothesized that obesity would be associated with diaphragm dysfunction attributable to mitochondrial oxygen consumption and structural and ultrastructural changes. Wistar rat litters were culled to 3 pups to induce early postnatal overfeeding and consequent obesity. Control animals were obtained from unculled litters. From postnatal day 150, diaphragm ultrasound, computed tomography, high-resolution respirometry, immunohistochemical, biomolecular, and ultrastructural histological analyses were performed. The diaphragms of obese animals, compared with those of controls, presented changes in morphology as increased thickening fraction, diaphragm excursion, and diaphragm dome height, as well as increased mitochondrial respiratory capacity coupled to ATP synthesis and maximal respiratory capacity. Fatty acid synthase gene expression was also higher in obese animals, suggesting a source of energy for the respiratory chain. Myosin heavy chain-IIA was increased, indicating shift from glycolytic toward oxidative muscle fiber profile. Diaphragm tissue also exhibited ultrastructural changes, such as compact, round, and swollen mitochondria with fainter cristae and more lysosomal bodies. Dynamin-1 expression in the diaphragm was reduced in obese rats, suggesting decreased mitochondrial fission. Furthermore, gene expressions of peroxisome γ proliferator-activated receptor coactivator-1α and superoxide dismutase-2 were lower in obese animals than in controls, which may indicate a predisposition to oxidative injury. In conclusion, in the obesity model used herein, muscle fiber phenotype was altered in a manner likely associated with increased mitochondrial respiratory capability, suggesting respiratory adaptation to increased metabolic demand.NEW & NOTEWORTHY Obesity has been associated with peripheral muscle dysfunction; however, little is known about its impact on the diaphragm. In the current study, we found high oxygen consumption in diaphragm tissue and changes in muscle fiber phenotypes toward a more oxidative profile in experimental obesity.

[Preoperative risk and perioperative management of obese patients]

The obese patient is at an increased risk of perioperative complications. Most importantly, these include difficult access to the airways (intubation, difficult or impossible ventilation), and post-extubation respiratory distress secondary to the development of atelectasis or obstruction of the airways, sometimes associated with the use of morphine derivatives. The association of obstructive sleep apnea syndrome (OSA) with obesity is very common, and induces a high risk of peri- and postoperative complications. Preoperative OSA screening is crucial in the obese patient, as well as its specific management: use of continuous positive pre, per and postoperative pressure. For any obese patient, the implementation of protocols for mask ventilation and/or difficult intubation and the use of protective ventilation, morphine-sparing strategies and a semi-seated positioning throughout the care, is recommended, combined with close monitoring postoperatively. The dosage of anesthetic drugs should be based on the theoretical ideal weight and then titrated, rather than dosed to the total weight. Monitoring of neuromuscular blocking should be used where appropriate, as well as monitoring of the depth of anesthesia. The occurrence of intraoperative recall is indeed more frequent in the obese patient than in the non-obese patient. Appropriate prophylaxis against venous thromboembolic disease and early mobilization are recommended, as thromboembolic disease is increased in the obese patient. The use of non-invasive ventilation to prevent the occurrence of acute post-operative respiratory failure and for its treatment is particularly effective in obese patients. In case of admission to ICU, an individualized ventilatory management based on pathophysiology and careful monitoring should be initiated.

Medical Versus Surgical ICU Obese Patient Outcome: A Propensity-Matched Analysis to Resolve Clinical Trial Controversies

OBJECTIVES

To determine the short- and long-term mortality of obese ICU patients following medical as opposed to surgical admission and the relation between obesity and mortality.

DESIGN

Retrospective analysis of prospectively collected data, using a propensity score-matched analysis of patients with medical or surgical admission.

SETTING

One French mixed medical-surgical ICU.

PATIENTS

Critically ill obese patients (body mass index ≥ 30 kg/m) and nonobese patients admitted during a 14-year period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Seven-hundred ninety-one obese patients and 4,644 nonobese patients were included, 338 (43%) and 2,367 (51%) medical and 453 (57%) and 2,277 (49%) surgical obese and nonobese patients, respectively. Mortality was significantly higher in medical than in surgical obese patients in ICU (25% vs 12%; p < 0.001) and up to 365 days (36% vs 18%; p < 0.001) post ICU admission. One-to-one propensity score matching generated 260 pairs with well-balanced baseline characteristics. After matching on propensity score, mortality was still significantly higher in medical patients both in the ICU (21% vs 13%; p = 0.03) and up to 365 days (30% vs 20%; p = 0.01) post ICU admission. Obesity was not significantly associated with mortality both in univariate analysis (140 obese patients [15%] in the dead group vs 651 [14%] in the alive group; p = 0.72) and multivariate analysis (odds ratio, 1.09 [95% CI, 0.86-1.38]; p = 0.49) after adjustment for Simplified Acute Physiology Score II, age, category of admission, history of cardiac disease, and history of respiratory disease.

CONCLUSIONS

After careful matching, the data suggest that ICU mortality in obese population was higher in the medical group than in the surgical group and remains significantly higher 365 days post ICU admission.

ARDS in Obese Patients: Specificities and Management

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Fibro-Adipogenic Remodeling of the Diaphragm in Obesity-Associated Respiratory Dysfunction

Respiratory dysfunction is a common complication of obesity, conferring cardiovascular morbidity and increased mortality and often necessitating mechanical ventilatory support. While impaired lung expansion in the setting of increased adipose mass and reduced central response to hypercapnia have been implicated as pathophysiological drivers, the impact of obesity on respiratory muscles-in particular, the diaphragm-has not been investigated in detail. Here, we demonstrate that chronic high-fat diet (HFD) feeding impairs diaphragm muscle function, as assessed in vivo by ultrasonography and ex vivo by measurement of contractile force. During an HFD time course, progressive adipose tissue expansion and collagen deposition within the diaphragm parallel contractile deficits. Moreover, intradiaphragmatic fibro-adipogenic progenitors (FAPs) proliferate with long-term HFD feeding while giving rise to adipocytes and type I collagen-depositing fibroblasts. Thrombospondin 1 (THBS1), a circulating adipokine, increases with obesity and induces FAP proliferation. These findings suggest a novel role for FAP-mediated fibro-adipogenic diaphragm remodeling in obesity-associated respiratory dysfunction.

Risk factors and outcomes for airway failure versus non-airway failure in the intensive care unit: a multicenter observational study of 1514 extubation procedures

BACKGROUND

Patients liberated from invasive mechanical ventilation are at risk of extubation failure, including inability to breathe without a tracheal tube (airway failure) or without mechanical ventilation (non-airway failure). We sought to identify respective risk factors for airway failure and non-airway failure following extubation.

METHODS

The primary endpoint of this prospective, observational, multicenter study in 26 intensive care units was extubation failure, defined as need for reintubation within 48 h following extubation. A multinomial logistic regression model was used to identify risk factors for airway failure and non-airway failure.

RESULTS

Between 1 December 2013 and 1 May 2015, 1514 patients undergoing extubation were enrolled. The extubation-failure rate was 10.4% (157/1514), including 70/157 (45%) airway failures, 78/157 (50%) non-airway failures, and 9/157 (5%) mixed airway and non-airway failures. By multivariable analysis, risk factors for extubation failure were either common to airway failure and non-airway failure: intubation for coma (OR 4.979 (2.797-8.864), P < 0.0001 and OR 2.067 (1.217-3.510), P = 0.003, respectively, intubation for acute respiratory failure (OR 3.395 (1.877-6.138), P < 0.0001 and OR 2.067 (1.217-3.510), P = 0.007, respectively, absence of strong cough (OR 1.876 (1.047-3.362), P = 0.03 and OR 3.240 (1.786-5.879), P = 0.0001, respectively, or specific to each specific mechanism: female gender (OR 2.024 (1.187-3.450), P = 0.01), length of ventilation > 8 days (OR 1.956 (1.087-3.518), P = 0.025), copious secretions (OR 4.066 (2.268-7.292), P < 0.0001) were specific to airway failure, whereas non-obese status (OR 2.153 (1.052-4.408), P = 0.036) and sequential organ failure assessment (SOFA) score ≥ 8 (OR 1.848 (1.100-3.105), P = 0.02) were specific to non-airway failure. Both airway failure and non-airway failure were associated with ICU mortality (20% and 22%, respectively, as compared to 6% in patients with extubation success, P < 0.0001).

CONCLUSIONS

Specific risk factors have been identified, allowing us to distinguish between risk of airway failure and non-airway failure. The two conditions will be managed differently, both for prevention and curative strategies.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT 02450669 . Registered on 21 May 2015.

Impact of the driving pressure on mortality in obese and non-obese ARDS patients: a retrospective study of 362 cases

PURPOSE

The relation between driving pressure (plateau pressure-positive end-expiratory pressure) and mortality has never been studied in obese ARDS patients. The main objective of this study was to evaluate the relationship between 90-day mortality and driving pressure in an ARDS population ventilated in the intensive care unit (ICU) according to obesity status.

METHODS

We conducted a retrospective single-center study of prospectively collected data of all ARDS patients admitted consecutively to a mixed medical-surgical adult ICU from January 2009 to May 2017. Plateau pressure, compliance of the respiratory system (Crs) and driving pressure of the respiratory system within 24 h of ARDS diagnosis were compared between survivors and non-survivors at day 90 and between obese (body mass index ≥ 30 kg/m²) and non-obese patients. Cox proportional hazard modeling was used for mortality at day 90.

RESULTS

Three hundred sixty-two ARDS patients were included, 262 (72%) non-obese and 100 (28%) obese patients. Mortality rate at day 90 was respectively 47% (95% CI, 40-53) in the non-obese and 46% (95% CI, 36-56) in the obese patients. Driving pressure at day 1 in the non-obese patients was significantly lower in survivors at day 90 (11.9 ± 4.2 cmH₂O) than in non-survivors (15.2 ± 5.2 cmH₂O, p < 0.001). Contrarily, in obese patients, driving pressure at day 1 was not significantly different between survivors (13.7 ± 4.5 cmH₂O) and non-survivors (13.2 ± 5.1 cmH₂O, p = 0.41) at day 90. After three multivariate Cox analyses, plateau pressure [HR = 1.04 (95% CI 1.01-1.07) for each point of increase], Crs [HR = 0.97 (95% CI 0.96-0.99) for each point of increase] and driving pressure [HR = 1.07 (95% CI 1.04-1.10) for each point of increase], respectively, were independently associated with 90-day mortality in non-obese patients, but not in obese patients.

CONCLUSIONS

Contrary to non-obese ARDS patients, driving pressure was not associated with mortality in obese ARDS patients.