Saturday, February 16, 2013
Respiratory failure - Definition, classification and difference between acute and chronic type
Respiratory failure may be classified as hypercapnic or hypoxemic.
Hypercapnic respiratory failure is defined as an arterial PCO2 (PaCO2 ) greater than 45mmHg.
Hypoxemic respiratory failure is defined as an arterial PO2 (PaO2 ) less than 55 mmHg when the fraction of oxygen in inspired air (FiO2) is 0.60 or greater.
In many cases, hypercapnic and hypoxemic respiratory failure coexist.
Distinctions between acute and chronic respiratory failure are summarized in the table below.
In general, acute hypercapnic respiratory failure is defined as a PaCO2 greater than 45 mmHg with accompanying acidemia (pH less than 7.30). The physiological effect of a sudden increase in PaCO2
depends on the prevailing level of serum bicarbonate anion. In patients with chronic hypercapnic respiratory failure e.g. COPD, a long-standing increase in PaCO2 results in renal compensation and an increased serum bicarbonate concentration. A superimposed acute increase in PaCO2 has a less dramatic effect than does a comparable increase in a patient with a normal bicarbonate level.
Distinction between acute and chronic hypoxemic respiratory failure may not be readily made on the basis of arterial blood gas values only. The presence of markers of chronic hypoxemia (e.g., polycythemia or cor pulmonale) provides clues to a long-standing disorder, whereas abrupt changes in mental status suggest an acute event.
Hypokalemia is defined as a serum potassium level of less than 3.5 mmol/L. normal = 3.5-5.5 mmol/L The preferred method of replacement is v...
Romberg's test is done to assess the integrity of the dorsal columns of the spinal cord. It is not a test to assess the cerebellar funct...
Definition: Edema is an abnormal presence of excessive fluid in the interstitial space. Pathophysiology: The movement of water and...
The mediastinum is divided into superior and inferior, the plane of division being a line from the manubriosternal joint to the lower surfac...
The Gram stain was developed in 1884 by the Danish bacteriologist Hans Christian Gram. It is one of the most useful staining procedures beca...
The plantar response is an important test to identify an upper motor neuron lesion. To elicit it, the muscles of the lower limbs...
A simple mnemonic to remember how the carpal bones are arranged is: " S he L ooks T oo P retty; T ry T o C atch H er" S cap...
The ECG changes in hypokalemia is mainly due to a delayed ventricular repolarisation. The changes normally do not correlate well with the p...
Mitral facies is one of the cutaneous manifestations of systemic diseases. The pathology in question here is mitral stenosis. Mitral fa...