Diaphragm Dysfunction in Mechanically Ventilated Patients

Ultrasound evaluation of diaphragm function in patients with cervical spinal cord injury: case report

Ultrasound evaluation of diaphragm function allows the detection of diaphragm dysfunction and the adaptation of ventilatory support in patients admitted to intensive care units. The studied patient had a C3 spinal cord injury. Ultrasound evaluation of diaphragm mobility showed that the patient suffered diaphragm dysfunction. A tracheotomy was indicated, and early ventilatory support was initiated. Ultrasound evaluation of diaphragm function in patients with cervical spinal cord injury is a useful and simple technique. It provides fast and reliable data for the diagnosis of respiratory insufficiency of neuromuscular origin.

Pleuropulmonary and diaphragmatic ultrasound in intensive care medicine

The usefulness of ultrasound for chest exploration was described in 1968. It was not until the 1990s, when its use became widespread in Intensive Care Units as a diagnostic, monitoring and procedural guide tool. The fact that it is a non-invasive tool, accessible at the bedside, with a sensitivity and specificity close to computerized tomography (CT) and with a short learning curve, have made it a mandatory technique in the management of critically ill patients. It is essential to know that there are different air/fluid ratio generated by different pathologies that gives rise to one echographic pattern or another. The identification of these patterns together with the clinical information will allow to make an accurate diagnosis in most settings of respiratory failure. Likewise, we must not forget the importance of evaluating diaphragmatic function by ultrasound during weaning from mechanical ventilation.

Diaphragmatic Dynamics and Thickness Parameters Assessed by Ultrasonography Predict Extubation Success in Critically Ill Patients

INTRODUCTION

A frequent cause of weaning and extubation failure in critically ill mechanically ventilated patients is diaphragm muscle dysfunction. Ultrasound (US) evaluation of the diaphragm yields important data regarding its thickness (diaphragm thickening fraction [TFdi]) and its movement or excursion (diaphragmatic dynamics) that reveal the presence of diaphragmatic dysfunction.

METHODS

Cross-sectional study, which included patients older than 18 years with invasive mechanical ventilation with an expected duration of more than 48 h, in a tertiary referral center in Colombia. The excursion of the diaphragm, inspiratory and expiratory thickness, and TFdi were evaluated by US. Prevalence and use of medications were evaluated, and the association with failure in ventilatory weaning and extubation was analyzed.

RESULTS

Sixty-one patients were included. The median age and APACHE IV score were 62.42 years and 78.23, respectively. The prevalence of diaphragmatic dysfunction (assessed by excursion and TFdi) was 40.98%. The sensibility, specificity, positive predictive value, and negative predictive value for TFdi < 20% was 86%, 24%, 75%, and 40%, respectively, with an area under the receiver operating characteristic (ROC) curve of 0.6. The ultrasonographic analysis of excursion of the diaphragm, inspiratory and expiratory thickness, and TFdi (>20%) allow in its set and with normal values, predict success or failure for the extubation with an area under the ROC curve of 0.87.

CONCLUSION

Diaphragmatic dynamics and thickness parameters together assessed by ultrasonography could predict the success of extubation in critically ill patients in Colombia, based on the finding of diaphragmatic dysfunction.

Bedside critical ultrasound as a key to the diagnosis of obstructive atelectasis complicated with acute cor pulmonale and differentiation from pulmonary embolism: A case report

Acute attack of dyspnea may be combined with acute cor pulmonale (ACP). Rapid and accurate identification of the etiology of ACP is the key to its diagnosis and treatment. Echocardiography is a better imaging tool in the assessment of right ventricular function. Under the guidance of the theory of cardiopulmonary interaction, ultrasonography can detect lung lesions, which causes ACP. We report the case of a 67-year-old man who received mechanical ventilation for acute respiratory failure. Right ventricular dysfunction was detected by echocardiography. Lung ultrasound showed a high risk of pulmonary embolism. However, obstructive atelectasis should not be ruled out after increasing back area ultrasonography. To avoid pitfalls, combined cardiac and lung ultrasound should be used carefully and strictly.

Prolonged Mechanical Ventilation: Outcomes and Management

The number of patients requiring prolonged mechanical ventilation (PMV) is increasing worldwide, placing a burden on healthcare systems. Therefore, investigating the pathophysiology, risk factors, and treatment for PMV is crucial. Various underlying comorbidities have been associated with PMV. The pathophysiology of PMV includes the presence of an abnormal respiratory drive or ventilator-induced diaphragm dysfunction. Numerous studies have demonstrated that ventilator-induced diaphragm dysfunction is related to increases in in-hospital deaths, nosocomial pneumonia, oxidative stress, lung tissue hypoxia, ventilator dependence, and costs. Thus far, the pathophysiologic evidence for PMV has been derived from clinical human studies and experimental studies in animals. Moreover, recent studies have demonstrated the outcome benefits of pharmacological agents and rehabilitative programs for patients requiring PMV. However, methodological limitations affected these studies. Controlled prospective studies with an adequate number of participants are necessary to provide evidence of the mechanism, prognosis, and treatment of PMV. The great epidemiologic impact of PMV and the potential development of treatment make this a key research field.

The Feasibility of Ultrasonographic Diaphragmatic Excursion in Healthy Dogs: Effect of Positioning, Diaphragmatic Location, and Body Weight of Dogs

Diaphragmatic excursion (DE) has been utilized for detecting respiratory related problems in humans. However, several factors should be considered such as the ultrasound technique and factors intrinsic to patients. Nevertheless, knowledge of the effect of these factors on DE in dogs is still lacking. The aim of this study was to evaluate the proper ultrasound technique by varying postures and diaphragmatic locations for DE measurement and to explore intrinsic factors such as diaphragmatic sides, sex, and body weight of dogs on DE. The prospective, analytic, cross-sectional study included 44 healthy dogs; 12 beagles and 32 dogs of other breeds. The experiment was divided into (i) an exploration of the proper ultrasound technique by varying postures (supine, standing, and recumbent in each of the right and left lateral positions), diaphragmatic locations (middle crus and proximal to the last rib), and diaphragmatic sublocations (xiphoid, mid, and proximal rib) for detection of DE and (ii) the evaluation of canine intrinsic factors affecting DE. The results show that the mid-diaphragmatic sublocation in the middle crus area in almost all positions revealed the highest percentage DE detection. However, DEs were revealed to be more accessible in the supine position. There was no significant difference in DE between the right and the left diaphragms or between the sexes of beagle dogs. However, body weight was significantly correlated with the DE among dogs of various sizes. In conclusion, the posture of the dogs and the diaphragmatic location can affect DE evaluation. Neither sex nor diaphragmatic side had an influence, but body weight was revealed as a major factor in DE in dogs.

Detecting Ventilator-Induced Diaphragmatic Dysfunction Using Point-of-Care Ultrasound in Children With Long-term Mechanical Ventilation

Long-term mechanical ventilation (MV) is defined as the use of MV for more than 6 hours per day for at least 3 weeks. Children requiring long-term MV include those with neuromuscular disease, central dysregulation, or lung dysfunction. Such children with medical complexity may be at risk for ventilator-induced diaphragmatic dysfunction. Ventilator-induced diaphragmatic dysfunction has been described in adult patients requiring acute MV with ultrasound (US). At this time, diaphragmatic US has not been evaluated in the pediatric post-acute care setting or incorporated into weaning strategies. We present 24 cases of children requiring long-term MV who underwent diaphragmatic US examinations to evaluate for ventilator-induced diaphragmatic dysfunction.

Early rehabilitation relieves diaphragm dysfunction induced by prolonged mechanical ventilation: a randomised control study

BACKGROUND

Prolonged mechanical ventilation (MV) induces diaphragm dysfunction in patients in the intensive care units (ICUs). Our study aimed to explore the therapeutic efficacy of early rehabilitation therapy in patients with prolonged MV in the ICU.

METHODS

Eighty eligible patients who underwent MV for > 72 h in the ICU from June 2019 to March 2020 were enrolled in this prospective randomised controlled trial. The patients were randomly divided into a rehabilitation group (n = 39) and a control group (n = 41). Rehabilitation therapy included six levels of rehabilitation exercises. Diaphragm function was determined using ultrasound (US).

RESULTS

Diaphragmatic excursion (DE) and diaphragm thickening fraction (DTF) were significantly decreased in all patients in both groups after prolonged MV (p < 0.001). The rehabilitation group had significantly higher DTF (p = 0.008) and a smaller decrease in DTF (p = 0.026) than the control group after 3 days of rehabilitation training. The ventilator duration and intubation duration were significantly shorter in the rehabilitation group than in the control group (p = 0.045 and p = 0.037, respectively). There were no significant differences in the duration of ICU stay, proportion of patients undergoing tracheotomy, and proportion of recovered patients between the two groups.

CONCLUSIONS

Early rehabilitation is feasible and beneficial to ameliorate diaphragm dysfunction induced by prolonged MV and advance withdrawal from the ventilator and extubation in patients with MV. Diaphragm US is suggested for mechanically ventilated patients in the ICU. Trial registration Chinese Clinical Trial Registry, ID: ChiCTR1900024046, registered on 2019/06/23.

Inspiratory Muscle Training Based on Anaerobic Threshold on the Functional Capacity of Patients After Coronary Artery Bypass Grafting: Clinical Trial

INTRODUCTION

Coronary artery bypass grafting (CABG) is associated with reduced ventilatory muscle strength and consequent worsening of functional capacity (FC). Inspiratory Muscle Training (IMT) can be indicated, but there is still a lack of knowledge about the use of the anaerobic threshold (AT) as a basis for prescription. The objective of this study is to evaluate if IMT based on AT modifies FC and inspiratory muscle strength of patients submitted to CABG.

METHODS

This is a clinical trial. On the first postoperative day, the patients were divided into two groups: the conventional group (IMT-C), which performed IMT based on 40% of maximal inspiratory pressure (MIP), and the IMT-AT group, which performed IMT based on AT. All patients underwent preoperative and postoperative assessment of MIP and performed a six-minute walk test (6MWT).

RESULTS

Forty-two patients were evaluated, 21 in each group. Their mean age was 61.4±10 years and 27 (64%) of them were male. There was a reduction of inspiratory muscle strength with a delta of 23±13 cmH2O in the IMT-C group vs. 11±10 cmH2O in the IMT-AT group (P<0.01) and of the walking distance with a delta of 94±34 meters in the IMT-C group vs. 57±30 meters in the IMT-AT group (P=0.04).

CONCLUSION

IMT based on AT minimized the loss of FC and inspiratory muscle strength of patients submitted to CABG.

A prospective observational study on critically ill children with diaphragmatic dysfunction: clinical outcomes and risk factors

Background

Diaphragmatic dysfunction (DD) has a great negative impact on clinical outcomes, and it is a well-recognized complication in adult patients with critical illness. However, DD is largely unexplored in the critically ill pediatric population. The aim of this study was to identify risk factors associated with DD, and to investigate the effects of DD on clinical outcomes among critically ill children.

Methods

Diaphragmatic function was assessed by diaphragm ultrasound. According to the result of diaphragmatic ultrasound, all enrolled subjects were categorized into the DD group (n = 24) and the non-DD group (n = 46). Collection of sample characteristics in both groups include age, sex, height, weight, primary diagnosis, complications, laboratory findings, medications, ventilatory time and clinical outcomes.

Results

The incidence of DD in this PICU was 34.3%. The level of CRP at discharge (P = 0.003) in the DD group was higher than the non-DD group, and duration of elevated C-reactive protein (CRP) (P < 0.001), sedative days (P = 0.008) and ventilatory treatment time (P < 0.001) in the DD group was significantly longer than the non-DD group. Ventilatory treatment time and duration of elevated CRP were independently risk factors associated with DD. Patients in the DD group had longer PICU length of stay, higher rate of weaning or extubation failure and higher mortality.

Conclusion

DD is associated with poorer clinical outcomes in critically ill childern, which include a longer PICU length of stay, higher rate of weaning or extubation failure and a higher mortality. The ventilatory treatment time and duration of elevated CRP are main risk factors of DD in critically ill children.

Trial registration

Current Controlled Trials ChiCTR1800020196, Registered 01 Dec 2018.

Use of Levosimendan in Intensive Care Unit Settings: An Opinion Paper

Levosimendan is an inodilator that promotes cardiac contractility primarily through calcium sensitization of cardiac troponin C and vasodilatation via opening of adenosine triphosphate–sensitive potassium (K_ATP) channels in vascular smooth muscle cells; the drug also exerts organ-protective effects through a similar effect on mitochondrial K_ATP channels. This pharmacological profile identifies levosimendan as a drug that may have applications in a wide range of critical illness situations encountered in intensive care unit medicine: hemodynamic support in cardiogenic or septic shock; weaning from mechanical ventilation or from extracorporeal membrane oxygenation; and in the context of cardiorenal syndrome. This review, authored by experts from 9 European countries (Austria, Belgium, Czech republic, Finland, France, Germany, Italy, Sweden, and Switzerland), examines the clinical and experimental data for levosimendan in these situations and concludes that, in most instances, the evidence is encouraging, which is not the case with other cardioactive and vasoactive drugs routinely used in the intensive care unit. The size of the available studies is, however, limited and the data are in need of verification in larger controlled trials. Some proposals are offered for the aims and designs of these additional studies.

Ventilator-induced diaphragm dysfunction in critical illness

IMPACT STATEMENT

Mechanical ventilation (MV) is life-saving for patients with acute respiratory failure but also causes difficult liberation of patients from ventilator due to rapid decrease of diaphragm muscle endurance and strength, which is termed ventilator-induced diaphragmatic damage (VIDD). Numerous studies have revealed that VIDD could increase extubation failure, ICU stay, ICU mortality, and healthcare expenditures. However, the mechanisms of VIDD, potentially involving a multistep process including muscle atrophy, oxidative loads, structural damage, and muscle fiber remodeling, are not fully elucidated. Further research is necessary to unravel mechanistic framework for understanding the molecular mechanisms underlying VIDD, especially mitochondrial dysfunction and increased mitochondrial oxidative stress, and develop better MV strategies, rehabilitative programs, and pharmacologic agents to translate this knowledge into clinical benefits.

Spontaneous breathing: a double-edged sword to handle with care

In acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) patients, spontaneous breathing is associated with multiple physiologic benefits: it prevents muscles atrophy, avoids paralysis, decreases sedation needs and is associated with improved hemodynamics. On the other hand, in the presence of uncontrolled inspiratory effort, severe lung injury and asynchronies, spontaneous ventilation might also worsen lung edema, induce diaphragm dysfunction and lead to muscles exhaustion and prolonged weaning. In the present review article, we present physiologic mechanisms driving spontaneous breathing, with emphasis on how to implement basic and advanced respiratory monitoring to assess lung protection during spontaneous assisted ventilation. Then, key benefits and risks associated with spontaneous ventilation are described. Finally, we propose some clinical means to promote protective spontaneous breathing at the bedside. In summary, early switch to spontaneous assisted breathing of acutely hypoxemic patients is more respectful of physiology and might yield several advantages. Nonetheless, risk of additional lung injury is not completely avoided during spontaneous breathing and careful monitoring of target physiologic variables such as tidal volume (Vt) and driving transpulmonary pressure should be applied routinely. In clinical practice, multiple interventions such as extracorporeal CO₂ removal exist to maintain inspiratory effort, Vt and driving transpulmonary pressure within safe limits but more studies are needed to assess their long-term efficacy.

Clinical management of chronic obstructive pulmonary disease patients with muscle dysfunction

Muscle dysfunction is frequently observed in chronic obstructive pulmonary disease (COPD) patients, contributing to their exercise limitation and a worsening prognosis. The main factor leading to limb muscle dysfunction is deconditioning, whereas respiratory muscle dysfunction is mostly the result of pulmonary hyperinflation. However, both limb and respiratory muscles are also influenced by other negative factors, including smoking, systemic inflammation, nutritional abnormalities, exacerbations and some drugs. Limb muscle weakness is generally diagnosed through voluntary isometric maneuvers such as handgrip or quadriceps muscle contraction (dynamometry); while respiratory muscle loss of strength is usually recognized through a decrease in maximal static pressures measured at the mouth. Both types of measurements have validated reference values. Respiratory muscle strength can also be evaluated determining esophageal, gastric and transdiaphragmatic maximal pressures although there is a lack of widely accepted reference equations. Non-volitional maneuvers, obtained through electrical or magnetic stimulation, can be employed in patients unable to cooperate. Muscle endurance can also be assessed, generally using repeated submaximal maneuvers until exhaustion, but no validated reference values are available yet. The treatment of muscle dysfunction is multidimensional and includes improvement in lifestyle habits (smoking abstinence, healthy diet and a good level of physical activity, preferably outside), nutritional measures (diet supplements and occasionally, anabolic drugs), and different modalities of general and muscle training.