P215 Discussion

April 3, 2002

Dr. Nephew

Problem A. Breathing

Most of us take breathing for granted; it is not something we think about every minute of everyday. In other words, "Breathing happens" but how? If you really think about breathing in all its glory, several questions come to mind…..

  1. What are the structural parts of the respiratory system? obvious
  2. What are the two primary functions of the respiratory system? Deliver Oxygen; get rid of CO2
  3. What are alveoli, how many are there in the lung, and why do we have so many of them? Thin-walled air sacs; 300 million in the lungs; large surface area for gas exchange
  4. Where is the actual site of gas exchange in the respiratory system? alveoli
  5. By what process does gas exchange occur? simple diffusion
  6. What are the two principal gases involved in this process? Oxygen and CO2
  7. Is the wall of the alveoli thick or thin? How thick or thin is it? Thin- one cell

Problem B. Disorders of the airways.

Asthma- Matt has had mild asthma for much of his life. Symptoms occur only occasionally, eg. on exposure to allergens or certain pollutants or after a viral respiratory infection. Within the past two years, he has developed exercise-induced asthma. It is a particular problem when he runs outdoors on cold, dry winter days. Like so many asthma sufferers, Matt treats the chief symptoms (difficult ventilation) with inhaled medications he can spray into his mouth when needed. One of the drugs is called a "beta 2 adrenergic agonist" because it binds to beta 2 adrenergic receptors like the chemical messengers normally present in the body and, after binding to the receptors, produces a similar effect. The other drug is a corticosteroid (Vanceril, as an example).

  1. What are the clinical hallmarks of asthma? Recurrent, episodic bouts of coughing, shortness of breath, chest tightness and wheezing.
  2. What is happening to the airways during an episode of asthma? Increased responsiveness of the trachea and bronchi to various stimuli, widespread narrowing of the airways, contraction of airway smooth muscle, mucosal thickening from edema and cellular infiltration, inspissation in the airway lumen of abnormally thick, viscous plugs of mucus.
  3. Briefly describe the pathogenesis of asthma, i.e, what is the cause of the disease? Classic immunological model- IgI antibodies bound to mast cells in the airway mucosa, upon re-exposure to antigen, cause release of histamine, prostaglandins, proteases (immediate brochoconstriction); sustained bronchoconstriction and inflammation due to cytokines produced by lymphocytes (interleukins, GMCSF, TNF,).
  4. What are the basic mechanisms that allows beta receptor agonist (albuterol) and the steroid (vanceril) to relieve the symptoms of asthma? Activation of beta2 receptors in respiratory and vascular smooth muscle promotes smooth muscle relaxation; corticosteroids are anti-inflammatory agents and promote mucosal antiinflammation by reducing cytokine production.
  5. Why might inhaling a lot of cold air (30 F, 25% humidity) precipitate an asthmatic attack? Vasoconstriction vs inflammation?

Problem C. Respiratory problems faced by newborns (premature babies).

The biggest problem facing babies born prematurely is that they can’t breath. "Premies" with IRDS (infant respiratory distress syndrome) are unable to to reinflated their alveoli during each inspiration.

  1. Why not? (HINT: Think about surface tension of the alveoli and the secretion that is essential for preventing collapse of the alveoli). Surface tension in the alveolus is too high.
  2. Where is the defect? Not enough surfactant
  3. Specifically where and when is the essential secretion made? Made during the last two months of fetal development.
  4. What can be done about it? Positive pressure respirators (force air into lungs), spray natural or synthetic surfactant into lungs.
  5. Using your imagination and creativity, how would you cure IRDS? Gene therapy, surfactant pump

Problem D. Birth defects of the respiratory system

Cystic fibrosis (CF) is the most common lethal genetic disease in the US. CF strikes one out of every 2400 children. Every day two children die of it.

  1. What are the respiratory symptoms of CF? Overproduction of viscous fluid that clogs the respiratory passages, fatal respiratory infections.
  2. What is the cause of CF? Defect in CFTR protein (Chloride channel that controls flow of Cl; less Cl is secreted, less water follows, thick mucus).
  3. CF is caused by a defect in a single gene, resulting in the production of a faulty protein. Knowing that this disease involves only one gene, and using your imagination and creativity, what kind of approach would you take to cure CF? Lung transplant, gene therapy

Problem E. Case Study

On an icy road recently, the driver slid into the path of an oncoming car and was hit broadside. When the paramedics arrived and freed the driver from the wreckage, she was deeply cyanotic and her respiration had stopped. Her heart was still beating, but her pulse was fast and thready. The EMTs reported that when he arrived, her head was cocked at a peculiar angle and it looked like she had a fracture at the level of the C2 vertebrae. After arrival to the hospital, the following observations were made: Right thorax compressed; ribs 7-9 fractured; Right lung atelectasis. Based on these observation, answer the following questions.

  1. How might the peculiar head position of explain the accident victim’s cessation of breathing? C2 fracture would interupt transmission of signals from brain stem down the phrenic nerve to the diaphragm. Diaphragm paralysis; no breathing.
  2. What procedures do you think should have been initiated immediately by the EMTs? Immobilize head and neck. Intubate airway to permit ventilation to lungs.
  3. Why is the accident victim cyanotic? What is cyanosis? Cyanosis is a decrease in the degree of oxygen saturation of hemoglobin. Decrease breathing results in fall in alveolar P02, resulting in less diffusion of oxygen between the lungs and bloodstream. Arterial PCO2 will increase as well. Both promote unloading of oxygen from hemoglobin.
  4. Assuming the victim survives, how will the accident affect her lifestyle in the future? Quadraplegia (paralysis of all four limbs).
  5. What is atalectasis and why is only the right lung affected? Collapse of a lung. Right thorax is compressed; only right lung is affected. Lungs are in separate pleural cavities, only right lung collapsed.
  6. How do the recorded injuries relate to atalectasis? Fractured ribs probably punctured her lung tissue and allowed air within the lung to enter the pleural cavity.
  7. What treatment will be done to reverse atalectasis? What is the rationale for this treatment? Reverse atalectasis by

Problem F. Lung Cancer

Smoking is responsible for the largest number of premature deaths in the United States. According to the Centers for Disease Control, smoking claims the lives of 430,000 adults in the United States each year. Your risk of developing lung cancer is ten times greater if you smoke. In addition, researchers are finding that smoking also may contribute to other types of cancer, including cancer of the larynx, oral cavity, esophagus, urinary bladder, kidney, pancreas, stomach, breast, uterine and cervix.

  1. Why is lung cancer detected late?
  2. Are there different types of lung cancer?
  3. Why is secondhand smoke harmful?
  4. How is lung cancer treated?
  5. Is there a genetic link to lung cancer? If so, does it matter if you are a man or a woman SMOKER?

Why is lung cancer detected late? Once symptoms have occurred, lung cancer is often incurable. Many smokers dismiss the early signs of cancer, such as a persistent cough. ou may wrongly assume that your coughing and wheezing are related to a "smoker's cough."

Are there different types of lung cancer? Yes, there are two. Small cell cancer, sometimes called oat cell cancer, occurs almost exclusively in smokers and accounts for 20 percent of lung cancers. It is a fast-growing tumor, which quickly spreads to other organs. Nonsmall cell lung cancer is more common and appears in three types of lung cancer: squamos cell (the most common in men), adenocarcinoma (the most common in women), and large cell.

Why is secondhand smoke harmful? Because of the way tobacco burns, secondhand smoke contains twice as much tar and nicotine per unit volume as does smoke inhaled from a cigarette. It contains three times as much of a cancer-causing compound called 3,4 benzpyrene, five times as much carbon monoxide and possibly 50 times as much ammonia. Secondhand smoke from pipes and cigars may be even more harmful.

How is lung cancer treated? When surgery is indicated, patients may undergo a wedge resection, which removes a small section of lung, a lobectomy, which removes an entire lobe or a pneumonectomy, removal of an entire lung. Small peripheral tumors can be diagnosed and treated with video-assisted thoracoscopy. During this procedure, a tube is inserted to collapse the lung to one-quarter of its normal size. This creates a space through which a pen-sized instrument can be inserted through the chest wall to biopsy and remove small tumors. Radiation therapy is now more precise with

the use of MRI and CT imaging, allowing design of a 3-D treatment plan. Research is underway to make chemotherapy more effective by timing and sequencing dosage with radiation and surgery.

What is the genetic link to lung cancer? According to a report published in The Journal of the National Cancer Institute in late 1999, a genetic mutation found in about 10 percent of lung cancers is linked to aggressive tumors and a four times higher risk of dying from the disease. The mutation, called K-ras, is three times more common in women smokers than in men.

Problem G. High Altitude on the Respiratory System

Most people live at an altitude of 8000 feet (2400 meters) or less. Let say for Spring Break, a P215 person traveled directly from Bloomington to Vail, CO to ski. There was no time for the body to acclimatize (make any respiratory or hematopoietic adjustments), and the P215 person’s body responded adversely.

  1. What might be some of the adverse responses of the body of the P215 person to traveling quickly above 8000 feet? Headaches, shortness of breath, nausea, dizziness.
  2. What is air made of? Nitrogen (79%), Oxygen (21%); Carbon dioxide and water (both less than 1%)
  3. It is easier to breath at sea level then at the top of the mountain K2. Are the percentages of the components of air the same at sea level vs K2? Why is it more difficult to breath at high altitude? Partial pressure of oxygen is less.
  4. When we demand an all out effort from our respiratory and cardiovascular systems, how might the kidney respond? Increase production of erythropoietin, which stimulates the bone marrow to produce more red blood cells (but takes time).

 

P215 Discussion

April 3, 2002

Dr. Nephew

QUIZ

1. The alveolar capillary membrane has gas on one side and blood on the other. Gas exchanges occur readily by

  1. Active transport
  2. Simple diffusion
  3. Pressure diffusion.

2. True or False. Albuterol and vanceril are examples of long-term controllers of asthma.

3. During an asthma attack, reversal of smooth muscle contraction is most easily achieved by administration of which of the following?

  1. Corticosteroids
  2. Leukotriene pathway inhibitors (alter prostaglandin production)
  3. beta adrenoreceptor simulators
  4. B and C
  5. All of the above

4. The "detergent" like substance that interferes with the cohesiveness of water molecules and reduces the surface tension of alveolar fluid is called

A. Tide

B. Surfactant

C. Surfin’ USA

5. True or False. Some cases of cystic fibrosis have been cured by using gene therapy to replace the defective gene with a healthy gene.

6. The lungs are really stretchy and this is referred to lung compliance. Anything that lowers lung compliance will making breathing

a. Easier

b. Harder

7. True or False. There is less oxygen at 8000m than at sea level.

8. True or False. Once symptoms have occurred, lung cancer is often incurable.