Card Set Information
What are the mechanism of lung changes in ARDS?
What happens with ARDS acutre respiratory failure?
- decreased oxygen exchange hypoxemia
- decrease lung volume- atelectasis
Results in confusion, decreased responsiveness, progressive metabolic and respiratory acidosis, cariac arrhythmias, shock
Acute respiratory failure- deteriorating trent- end result of many pulmonary conditions
Partial pressures of respiratory gases
What are the acute respiratory failures?
Severe hypoxemia PaO2 < 50mmHg norm 80-100
Hypercapnia PaCO2 >50 norm 35-45
Ph decreasing <7.3 norm 7.35-7.45
What happens as a result of acute respiratory failure?
complicated by relex pulmonary vasoconstriction from the hypoxia or acidosis
impairs lung perfusion and increases cardiac workload
What are the gas diffusion problems of Acute respiratory failure?
Partial pressure- gas concentration or partial pressure changes, obstruction.
Diffusion- SA, respiratory membrane thickness, fluid excess
Posture- upright ventilation and perfusion best in lower lobe, upper lobe less compliant than lower lobes, BP lower in apices (top/ apex) of the lung.
Supine/ side lying change regional perfusion and ventilation
What is the normal ventilation and perfusion ratio of the lungs?
- Normal approx 0.8- 0.9
- Limited autoregulation
What happens if there is a mismatch with the perfusion and ventilation of the lungs?
- Inadequate ventilationbut good perfusion = blood is not ventilated resulting in right to left shunt - decrease systems O2 and hypoxemia
- Inadequate perfusion but well ventilated = alveolar dead space
How much O2 is dissolved in the plasma?
How is O2 transported?
bounded to haemoglobin
O2 exchanges between 20-40 PO2 and when only 50% of Hb is saturated.
The exchange depends on O2, CO2, temp and plasma pH.
How much carbon dioxide is dissolved in plasma?
What % of CO2 is loosely bound to the globin portion of Hb?
How is most of the CO2 carried around the body?
diffused into RBC for carbonic acid- bicarbonate buffer system for serum pH maintenance
Acid- Base Balance
Summary Acidosis- Alkalosis: