Sweat chloride Flashcards
Principle fo Iontophoresis
sweat glands on a localized are fo skin are activated by TEH iontophoretic introduction fo pilocarpine. In the process fo iontophoresis, an electric potential is established so that pharmacologically active ions carry a current and are thereby introduced into the skin
The reagent used in iontophoresis
a positive electrode moistened with pilocarpine NITRATE is used to induce the positively charged pilocarpine radicals to move away from the electrode and into the skin.
How is sweat collected?
The pilocarpine stimulated sweat glands respond by producing sweat, which is collected on a piece fo filter paper. and analyzed by using the chloride titrator.
Two electrochemical methods involved in chloridometry
coulometric and amperometric
The purposes of nitric acid
the sample is diluted in a nitric acetic acid solution to which a small amount of gelatin indicator has been added. provides good electrolytic conductivity
The purpose of acetic acid
Essentially renders the silver chloride formed during the titration insoluble by making the solution less polar; thereby yielding a very sharp endpoint. also helps prevent the reduction of silver chloride at the indicator electrode
The purpose of gelatin
Produces a smoother, more uniform current flow by equalizing any high spots on the electrode.
Coulometric
A constant direct current potential is passed between two silver electrodes in the generator circuit. The amount of electricity produced after all of the substance is reached is quantitated.
Amperometric
Current is measured as it flows through the working electrode in an electrochemical cells. a rapid increase in the conductivity of the solution which si detected by a pair of silver electrodes in the indicator circuit.
The purpose of sweat chloride testing.
The gold standard test for diagnosis of Cystic Fibrosis.
Discuss how the genetic defect present in CF disrupts the functions of the Airways
Clogging and infection fo bronchial passages impede breathing. The infection progressively destroy the lungs. Lung disease accounts for most deaths from CF
Discuss how the genetic defect present in CF disrupts the functions of the Liver
Plugging of small bile ducts impedes digestion and disrupts liver function in perhaps 5% of patients.
Discuss how the genetic defect present in CF disrupts the functions of the pancreas
Occlusion of ducts prevents the pancreas from delivering critical digestive enzymes to the bowel in 85% of patients. Diabetes can result as well
Discuss how the genetic defect present in CF disrupts the functions of the Small intestine
Obstruction fo the gut by thick stool necessitates surgery in about 10% of newborns
Discuss how the genetic defect present in CF disrupts the functions of the reproductive tract
Absence fo fine ducts, such as the vas deferens, renders 95% of males infertile. occasionally, women are made infertile by a dense plug of mucus that blocks sperm from entering the uterus.
The genetic inheritance of CF
Transmitted as an autosomal recessive trait.
Expected range for patients older than 6 months
0-39 mmol/L
Expected range for patients up to and including 6 months fo age
0-29 mmol/L
Abnormal critical value for any age
> or equal to 60 mmol/L
indeterminate range for patients older than 6 months
40-59 mmol/L
indeterminate range for patients up to and including 6 months of age
30-59 mmol/L
List at least five symptoms that a patient would exhibit that might cause a physician to order sweat chloride analysis
Pulmonary sx- (difficulty breathing-wheezing, rasping, asthma-like sx, decreased pulmonary function, lesions, recurrent respiratory infections, chronic congestion, cough)
Digestive sx- (failure to thrive (poor weight gain), pancreatic insufficiency, frequent bowel movements0 greasy stools-foul odor)
Other sx; meconium ileus, prolapsed rectum, liver disease, nasal polyps
List two organisms that are commonly the causative agent for infections present in cystic fibrosis patients.
Staphylococcus aureus and Pseudomonas aeruginosa.
List the investigators names associated with this test methodology
Gibson and Crook
Explain CFTR
The gene defect for CF affects CFTR, which prevents chloride from being transported across the cell membranes. This will cause the cells to draw water in from the surrounding tissue. In the lungs and digestive tract this will cause the secretions in the area to become thicker than normal as water is drawn from them. This secretion will build up and cause the symptoms of CF
