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CYSTIC
FIBROSIS
Presented by Lisa Waseleski, R.N.
Learning objectives:
• The learner will describe normal structures and
functions of the respiratory system.
• The learner will describe normal structures and
functions of the pancreas.
• The learner will describe characteristics of an
autosomal recessive disorder in relation to cystic
fibrosis.
• The learner will describe the pathophysiology and
clinical manifestations of cystic fibrosis.
• The learner will describe the diagnosis and treatment
of cystic fibrosis.
Structures of the respiratory
system:
The respiratory system includes the following structures:
nasal cavity
pharynx
epiglottis
larynx
carina
trachea
right and left main stem bronchus
segmental bronchi
terminal bronchioles
acinus
thoracic cavity/lungs
mediastinum
diaphragm
Functions of the respiratory
system
• The air-conducting passages that bring air into the lungs are the
nose, pharynx, larynx, trachea, bronchi and bronchioles.
• Ciliated mucous membranes line the respiratory tract. Air is
filtered, warmed and humidified upon entering the nasal cavity.
• Air passes from the pharynx into the larynx.
• A triangular space between the vocal cords, the glottis, opens
into the trachea and forms the division between the upper and
lower respiratory tracts.
Continued from the previous
slide:
• The trachea and bronchi form the tracheobronchial tree.
• The trachea branches into the right and left main stem bronchi
known as the carina.
• The right and left main stem bronchi divide to become the lobar
bronchi, then segmental bronchi, then terminal bronchioles.
• Beyond the terminal bronchiole is the acinus, the pulmonary
functional unit, gas exchange takes place here.
• 300 million alveoli or small air sacs are contained within each
lung.
Continued from the previous
slide:
• Alveolar lining cells: type 1 and 2 pneumocytes are responsible
for the secretion of the lipoprotein surfactant.
• The lungs are elastic cone shaped organs that lie within the
thoracic cavity.
• The central mediastinum separates the lungs.
• The diaphragm forms the floor of the thoracic cavity and
separates it from the abdominal cavity.
• Pulmonary and bronchial blood vessels, bronchi, nerves and
lymphatics enter each lung at the hilus to form the root of the
lung.
• The right lung is divided into three lobes and is larger compared
to the left lung which has two lobes.
Pulmonary circulation:
• The lung has a dual blood supply from the bronchial and
pulmonary arteries.
• The bronchial circulation provides oxygenated blood from the
systemic circulation to meet the metabolic needs of lung tissue.
• The bronchial arteries originate from the thoracic aorta and
travel along the posterior walls of the bronchi.
• The smaller bronchial veins drain into the pulmonary veins.
The large bronchial veins empty into the superior vena cava and
return blood to the right atrium.
• The bronchial circulation does not take part in gas exchange
causing a shunt of unoxygenated blood, approximately 2-3% of
cardiac output.
• The pulmonary artery arising from the right ventricle provides
mixed venous blood to the lungs, where gas exchange takes place.
Continued from the previous
slide:
• A network of pulmonary
capillaries surround the
alveoli providing the
necessary exchange of
gases between the blood
and the alveoli.
• Oxygenated blood is
returned through the
pulmonary veins to the left
ventricle where it is
distributed to the cells via
systemic circulation.
Structures and functions of the
pancreas:
• The pancreas is a compound tubuloalveolar gland,
approximately 6-8 inches in length and 1 ½ inches wide.
• The pancreas lies retroperitoneal and is divided into three major
segments: the head, the body, and tail.
• The pancreas resembles a bunch of grapes, the branches of
which are the ducts terminating into the main pancreatic duct,
or the duct of Wirsung.
• Small ducts from each acinus empty into the main ducts. The
main duct extends through the length of the gland and joins the
common bile duct at the ampulla of Vater before entering the
duodenum.
Continued from the previous
slide:
• The pancreas is made up of two
types of cells: the exocrine cells
and the endocrine cells.
• The exocrine cells produce the
components of pancreatic juice.
• The endocrine cells produce insulin
and glucagon.
Characteristics of autosomal
recessive inheritance and cystic
fibrosis:
• Gene is on an autosome.
• Expressed only in homozygotes (aa); heterozygotes (Aa) are
phenotypically normal carriers.
• Males and females are equally affected.
• Horizontal inheritance pattern is present
• When both parents are carriers, each offspring has a 50%
chance of being a carrier, a 25% chance of having the disease
and a 25% chance of being normal.
• Early age onset of disease is common.
Continued from the previous
slide:
• Cystic Fibrosis is one of the most common autosomal recessive
diseases in Caucasian populations affecting approximately 1 in
2500 individuals.
• The gene responsible for CF (cystic fibrosis) is located on the
long arm of chromosome 7. The CF gene protein product
(CFTR) encodes for a protein that functions as a chloride
channel.
Pathophysiology of cystic
fibrosis:
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CFTR mutations result in abnormalities of chloride transport across
epithelial cells on mucosal surfaces.
The failure of epithelial cells to conduct chloride and water transport
result in dry and viscid secretions in the respiratory tract, pancreas, GI
tract, sweat glands and other exocrine tissues.
Changes in the chemical properties of mucous may lead to obstructions
in the respiratory and digestive systems.
In the respiratory system, the viscous mucous obstructs airways and
creates conditions that lead to repeated infections in the lungs.
CF interferes with the normal functions of the liver, pancreas and other
digestive organs, causing problems with digestion and absorption of
nutrients.
Diagnosis and treatment of
cystic fibrosis:
• Diagnosis is usually made within the first few years of life. A
sweat electrolyte test, sodium >90 chloride>60 is diagnostic for
cystic fibrosis. Infants and children may present with a delay in
passing meconium, may have foul smelling pale and greasy
stools, and have frequent respiratory infections. Nasal polyps
and sinusitis are common findings in these patients.
• Treatment is aimed at the management of pulmonary
dysfunction. Aerosol treatments with bronchodilators and
mucolytic agents in conjunction with chest physiotherapy at
least twice per day to prevent respiratory infection are crucial.
An aerosol recombinant human deoxyribonuclease (DNase) is
effective in clearing thick mucous.
Continued from the previous
slide:
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Prompt treatment of respiratory infection with aerosol or IV antibiotics
is necessary.
In 1993, researchers developed a mucus-thinning drug called
pulmozyme specifically for CF patients. This drug decreases lung
infections and increases lung function. (Smith MD, 2001).
Regular exercise is helpful to move lung secretions.
Pancreatic enzymes given prior to every meal help to enhance
digestion.
A diet rich in proteins and calories is essential to meet growth needs.
Vitamins and other dietary supplements are important to add more
nutrients to the diet.
Patients with severe digestive problems may require supplemental tube
feeding or IV nutrition.
Psychosocial support is important to assist the patient cope with this
chronic illness.
Continued from the previous
slide:
• Ibuprofen, when given at a dose sufficient to achieve a peak
plasma concentration between 50 and 100 ug/ml over several
years, has been shown to slow the rate of decline in pulmonary
function, especially in children age 5-13. (Merck Manual, Sec.
19, Ch 267).
• Heart-lung and bilateral lung transplants have been performed
successfully in patients with advanced cardiopulmonary disease.
• Mutation analysis can be used for prenatal diagnosis and carrier
testing in families with a previously affected child.
References/Internet Sources
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Guyton, A.C.& Hall, J. E. (2000). Textbook of medical physiology
(ioth ed.) Philadelphia: W.B. Saunders
Pagana, K.D. & Pagana T.J. (2002). Mosby’s manual of diagnostic
and laboratory tests (2nd ed.) St Louis: Mosby
Price, S.A. & Wilson, L.M. (2003). Pathophysiology, clinical concepts of
disease processes (6th ed.) St Louis: Mosby
The Merck Manual of Diagnostics and Therapy, (copyright 1995-2003)
section 19. Pediatrics, chapter267. Cystic Fibrosis Topics.
Retrieved March 30, 2003 from
http://www.merck.com/pubs/mmanual/section19/chapter267/267
a.htm
•
The Merck Manual of Diagnostics and Therapy, (copyright 19952003) section 12. Immunology: Allergic Disorders, chapter 149.
Transplantation Topics. Retrieved March 30, 2003 from
http://www.merck.com/pubs/mmanual/section12/chapter149/149
f.htm
References/Internet Sources:
• Pace, B. (2000). Cystic fibrosis. Journal of American Medical
Association, 284:1884. Retrieved March 26, 2003 from
http:www.medem.com/search/article_display.cfm?path=n:
&mstr=/ZZZIX1MDUEC.html…
• Understanding Cystic Fibrosis. ( 2001). WebMD Medical
Reference, Retrieved March 29, 2003 from
http://aolsvc.health.webmd.aol.com/content/article/10/168
0_54803