الفهرس 
Definition, Epidemiology and PathophysiologyOnly 14 pages are availabe for public view
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Abstract
The term ARDS was first used in 1967, it is not a new disease. it had
several names over the years, including shock lung, Da Nang lung
(from the Vietnam war), stiff-lung syndrome, leaky capillary
pulmonary edema, noncardiogenic pulmonary edema, acute lung
injury, adult respiratory distress syndrome, and most recently, acute
respiratory distress syndrome, or ARDS.
As of June 2012, the clinical definition ALI and ARDS has changed.
This new definition addresses some of the limitations of the previous
classification (AECC, 1994) There are 4 components of the new
Berlin Classification of ARDS.
- Timing: development of ARDS within 1 week of a known
clinical insult or appearance of new or worsening of previous
respiratory symptoms.
- Chest imaging: bilateral opacities not fully explained by
effusions, lobar/lung collapse, or nodules.
- Origin of pulmonary edema: the pulmonary artery wedge
pressure criterion < 18 mm Hg was removed from the definition.
If there is no risk factor identifiable for ARDS, an objective
evaluation with echocardiogram is required to assist in
elimination of a possible hydrostatic edema.
- Oxygenation: ARDS has three categories based on severity of
hypoxemia.
- Mild ARDS: 200 mm Hg < Pao/Fi02 < 300 mm Hg.
- Moderate ARDS: 100 mm Hg < Pao/Fi02 < 200 mm Hg.
- Severe ARDS: < 100 mm Hg Pao/Fi02.
ARDS has an estimated annual incidence in the United States of
approximately 79 cases per 1 00,000 person-years.
ARDS may be caused by conditions eliciting lung injury directly
(gastric aspiration, pulmonary contusion, pneumonia, )and those
that induce lung injury indirectly like (sepsis, trauma)
- Lung injury is an evolving condition and the pathological features of
ARDS are typically described as passing through three overlapping
phases - an inflammatory or exudative phase, a proliferative phase
and, lastly, a fibrotic phase.
Patients with ARDS typically present with respiratory distress
characterized by dyspnea, hypoxemia, bilateral alveolar infiltrates, and
diffuse crackles.
Most current therapies for acute respiratory distress syndrome (ARDS)
are supportive, aimed at improving gas exchange and preventing
complications while the underlying condition that precipitated the
ARDS is addressed
Mechanical ventilation (MV) is critical for survival of many patients
with the acute respiratory distress syndrome (ARDS). Without MV
death may occur within hours to days from acute hypoxemic and
hypercarbic respiratory failure.
However, MV can also cause additional lung injury (ventilatorinduced
lung injury, VILI)
For most patients, we suggest proceeding directly to invasive
mechanical ventilation, rather than performing an initial trial of
noninvasive positive pressure ventilation
Patient with ARDS can be supported using either volume-limited or
pressure-limited modes of ventilation.
For patient with ARDS tidal volume (VT) and respiratory rate (RR)
should be set to meet ventilatory requirements and limit VILI. A target
VT around 6-ml/kg body weight should be maintained in patients with
ARDS, regardless of the mode of ventilation (VCV or PCV). In
addition, Effort should be made to maintain plateau pressure below 30
cmH2O.
The routine use of ventilatory approaches of open lung ventilation,
high PEEP, and recruitment maneuvers and prone ventilation warrant
- further investigation. However, they can be considered in patients with
moderate to severe ARDS.
Despite evidence that HFOV improves oxygenation, it does not
reduce, and may increase, in-hospital mortality in adult patients with
adult respiratory distress syndrome (ARDS) compared with a
ventilation strategy of low tidal volume and high positive endexpiratory
pressure.
We suggest that patients with severe, but potentially reversible, acute
respiratory failure that is unresponsive to conventional management be
evaluated for ECMO if it is available within the medical center.
Potential therapies for ARDS are being evaluated in an attempt to
improve clinical outcomes in ARDS; however, these therapies have
not become routine in adults with ARDS because either there are
physiological benefits without definitive patient-important benefits or
the patient-important effects are uncertain .like (Exogenous surfactant
therapy and antioxidant therapy, Inhaled nitric oxide, inhaled
prostacyclin, and inhaled prostaglandin E1, and liquid ventilation (LV)
Preclinical data and preliminary data in humans suggest that human
mesenchymal stem cells may prove promising as a means to
ameliorate lung injury and promote tissue repair in patients with
ARDS
ARDS is associated with appreciable mortality, with estimates ranging
from 26 to 58 percent. In-hospital survival appears to have improved
over time.
Survivors of ARDS can develop cognitive, psychological, and
physical impairments that may last for months to years following their
acute illness.