Understanding Of Ventilator-induced Lung Injury Research Articles

Reinterpreting the ventilator-induced lung injury from the prospective of mechanical power

Mechanical power is the power that the ventilator transmits to the respirator for lung ventilation. In recent years, some researchers have suggested that mechanical power may be a good indicator for assessing ventilator-induced lung injury in general, which can be used for guiding the best mechanical ventilation strategy. While introducing the definition and calculation method of mechanical power, this paper focuses on the association and potential mechanism of mechanical power with ventilator-induced lung injury, which aims to provide a new perspective and research direction for clinical understanding of ventilator-induced lung injury.

Extracorporeal Membrane Oxygenation in Critical Care: Past, Present, and Future

AbstractExtracorporeal membrane oxygenation (ECMO) provides support for cardiac and pulmonary failure, and it was introduced into clinical practice over 40 years ago. The translation of surgical extracorporeal circulation into long-term support was enabled by the development of efficient, biocompatible artificial lungs and blood pumps. Early clinical trials in adult patients did not support clinical benefit in acute respiratory failure, but they were plagued by lack of center experience, older approaches to management, and lack of understanding of ventilator-induced lung injury. Recent clinical trials and retrospective studies, however, suggest a benefit in selected patients. Three neonatal trials for respiratory failure led to ECMO as a standard of care in this population, as well as in the pediatric population despite lack of controlled trials. Cardiac support with ECMO took a foothold in the management of pediatric congenital heart disease in the perioperative period, and subsequently expanded to adult cardiac failure for both perioperative and nonsurgical indications. Presently, ECMO is used to support a variety of etiologies of cardiac and pulmonary failure in all age groups. Expanding indications include support of septic shock, cardiopulmonary arrest, and donation after cardiac death, as well as bridging patients with chronic disease to transplant or long-term support devices. The future is focused on developing integrated support systems, overcoming the requirement for anticoagulation, and perfecting long-term implantable or paracorporeal pulmonary support systems.

Lung Metabolism During Ventilator-Induced Lung Injury

Concerns about pulmonary complications of positive pressure ventilation (1) are at least as old as the description of the Acute Respiratory Distress Syndrome (ARDS) (2). Yet, it took about a decade until experimental findings (3) shifted the focus from air leaks and oxygen toxicity to the biological effects of large excursions of the lung parenchyma (4). The demonstration that mechanical ventilation with high peak inspiratory pressures and low positive end-expiratory pressure (PEEP) could produce edema, increased alveolo-capillary permeability, leukocyte infiltration, and inflammation in normal lungs established the current understanding of ventilator-induced lung injury (VILI) (4, 5). The clinical relevance of VILI was confirmed by the demonstration of a 22% decrease in mortality of ARDS patients when lung stretch was reduced through lower tidal volumes (VT). (6). In addition to excessive lung stretch due to large VT, it has been recognized that VILI can also be caused by low end-expiratory lung volumes, even at low airway pressures. Mechanisms proposed to explain such injury include concentration of stresses in the heterogeneously expanding lung parenchyma (7), and propagation and rupture of liquid plugs producing injurious fluid mechanical stresses during cyclic recruitment-derecruitment of distal lung units (8, 9). Mitigation of these low-volume phenomena by optimizing lung recruitment with higher PEEP levels (10) and proning (11) has been beneficial in patients with moderate and severe ARDS. However, despite the large number of experimental and clinical studies, uncertainty persists about the relative contribution of overdistension versus low-volume injury to the ultimate lung damage produced by VILI (12). Topographically, in supine patients, nondependent (ventral) injury would be expected if overdistension would predominate (13), whereas dependent (dorsal) damage would be expected for predominant low-volume injury (14). The clinical relevance of the topic has been emphasized by the suggestion that the mass of opening-closing lung is an independent risk factor for death in patients with ARDS (15), and that regional forces during mechanical ventilation determine lung parenchyma abnormalities found in ARDS survivors (16).

Support of respiratory failure in the pediatric surgical patient.

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances in the understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for supporting children and adults with severe respiratory failure. This review will focus on recent laboratory and clinical data regarding the techniques of lung protective ventilator strategies, inhaled nitric oxide, liquid ventilation, and extracorporeal life support (ECLS, ECMO). Some of these modalities are commonplace, while others may have much to offer the pediatric clinician if their benefit is clearly demonstrated in future clinical trials.

Complications of mechanical ventilation.

Outcomes of critically ill patients are affected by the severity of the acute illnesses and by complications that may result from treatments. This article reviews the major complications associated with mechanical ventilation. Special emphasis is placed on recent advances in the understanding of ventilator-induced lung injury and strategies to avoid this life-threatening complication. In this update, the incidence, diagnosis, prevention, and management of complications associated with mechanical ventilation are discussed for each major organ system.

Advances in ventilatory support of the pediatric surgical patient.

Severe respiratory failure in newborn and pediatric patients is associated with significant morbidity and mortality. Basic science laboratory investigation has led to advances both in our understanding of ventilator-induced lung injury and in optimizing the supportive use of conventional ventilation strategies. Over the past few years, progress has been made in alternative therapies for ventilating both children and adults with severe respiratory failure. This review focuses on recent laboratory and clinical data detailing the techniques of permissive hypercapnia, high frequency oscillatory ventilation, inhaled nitric oxide, intratracheal pulmonary ventilation, and liquid ventilation. Some of these modalities are becoming commonplace, and others may have much to offer the clinician if their benefit is clearly demonstrated in future clinical trials.

Medical and ventilatory management of status asthmaticus.

Despite improved understanding of the basic mechanisms underlying asthma, morbidity and mortality remain high, especially in the "inner cities." The treatment of choice in status asthmaticus includes high doses of inhaled beta 2-agonists, systemic corticosteroids, and supplemental oxygen. The roles of theophylline and anticholinergics remain controversial, although in general these agents appear to add little to the bronchodilator effect of inhaled beta-agonists in most patients. Anti-leukotriene medications have not yet been evaluated in acute asthma. Other therapies, such as magnesium sulfate and heliox, have their advocates but are not recommended as part of routine care. If pharmacological therapy does not reverse severe airflow obstruction in the asthmatic attack, mechanical ventilation may be temporarily required. Based on our current understanding of ventilator-induced lung injury, optimal ventilation of asthmatic patients avoids excessive lung inflation by limiting minute ventilation and prolonging expiratory time, despite consequent hypercapnia. Unless respiratory function is extremely unstable, the use of paralytic agents is discouraged because of the increased risk of intensive care myopathy. Patients who have suffered respiratory failure due to asthma are at increased risk for subsequent death due to asthma (14% mortality at 3 years) and should receive very close medical follow-up. In general, severe asthmatic attacks can best be prevented by early intervention in the outpatient setting. In the words of Dr. Thomas Petty, "... the best treatment of status asthmaticus is to treat it three days before it occurs".