Respiratory distress syndrome is a complication of SHOCK, systemic SEPSIS and viral respiratory infections. It was ?rst described in 1967, and – despite advances with assisted ventilation
– remains a serious disease with a mortality of more than 50 per cent. The maintenance of adequate circulating blood volume, peripheral PERFUSION, acid-base balance and arterial oxygenation is important, and assisted ventilation should be instituted early.
In newborns the mechanism is diferent, being provoked by an inability of the lungs to manufacture SURFACTANT.... respiratory distress syndrome
The exact trigger is unknown, but it is thought that, whatever the stimulus, chemical mediators produced by cells of the immune system or elsewhere in the body spread and sustain an in?ammatory reaction. Cascade mechanisms with multiple interactions are provoked. CYTOTOXIC substances (which damage or kill cells) such as oxygen-free radicals and PROTEASE damage the alveolar capillary membranes (see ALVEOLUS). Once this happens, protein-rich ?uid leaks into the alveoli and interstitial spaces. SURFACTANT is also lost. This impairs the exchange of oxygen and carbon dioxide in the lungs and gives rise to the clinical and pathological picture of acute respiratory failure.
The typical patient with ARDS has rapidly worsening hypoxaemia (lack of oxygen in the blood), often requiring mechanical ventilation. There are all the signs of respiratory failure (see TACHYPNOEA; TACHYCARDIA; CYANOSIS), although the chest may be clear apart from a few crackles. Radiographs show bilateral, patchy, peripheral shadowing. Blood gases will show a low PaO2 (concentration of oxygen in arterial blood) and usually a high PaCO2 (concentration of carbon dioxide in arterial blood). The lungs are ‘sti?’ – they are less e?ective because of the loss of surfactant and the PULMONARY OEDEMA.
Causes The causes of ARDS may be broadly divided into the following:... acute respiratory distress syndrome (ards)
Treatment is with ventilation and oxygen for the underlying cause.... respiratory failure
respiratory distress syndrome (RDS; hyaline membrane disease) the condition of a newborn infant in which the lungs are imperfectly expanded. Initial inflation and normal expansion of the lungs requires the presence of a substance (*surfactant) that reduces the surface tension of the air sacs (alveoli) and prevents collapse of the small airways. Without surfactant the airways collapse, leading to inefficient and ‘stiff’ lungs. The condition is most common and serious among preterm infants, in whom surfactant may be deficient. It lasts 5–10 days, with worsening on days 2–3. Breathing is rapid, laboured, and shallow, and microscopic examinations of lung tissue in fatal cases has revealed the presence of *hyalin material in the collapsed air sacs. The condition is treated by careful nursing, intravenous fluids, and oxygen, with or without positive-pressure ventilation (see noninvasive ventilation). Early surfactant replacement therapy has been shown to reduce the severity of RDS and when given prophylactically it has been demonstrated to improve clinical outcome. See also adult respiratory distress syndrome.... respiratory distress