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PHYSIOLOGY

11. A subject is connected at FRC to a bag containing 2L of 8% He, 92% O2. He rebreathes from the bag until mixing is complete; at which time the fraction of He is 4.6%. What is the value of FRC?

A. 1.15L

B. 1.48L (can you please explain this answer)

C. 2.48L

D. 3.48L

E. It cannot be calculated from the information given

The minimum time it takes a normal person to go from residual volume (RV) to total lung capacity (TLC) is less than the minimum amount of time to go from TLC to RV. The most probable explanation for this effect is:

A. the chest wall tends to spring outward when the respiratory system is at RV.

B. the chest wall is less compliant at RV.

C. inspiratory muscles are stronger than expiratory muscles.

D. the lungs have less recoil at TLC.

E. the airways tend to collapse during forced expiration. (can you please explain why this is the answer)

Two gases, A and B have the same partial pressure difference across the alveolar capillary barrier. Gas A has a molecular weight of 36 and solubility of 24 while gas B has a molecular weight of 16 and solubility of 2. What is the rate of diffusion of gas A through the barrier compared to gas B?

A. 12:1

B. 8:1 (can you explain why B is the answer?)

C. 6:4

D. 4:1

E. They are the same.

If an individual with a tidal volume of 500 ml and a dead space volume of 100 ml were to exercise and double the CO2 production, with no change in respiratory rate, what tidal volume would be required to maintain their original PCO2 of 40 mm Hg?

A. 1200 ml

B. 1100 ml

C. 1000 ml

D. 900 ml (can you explain why the answer is D?)

E. 800 ml

39. What is the total amount of oxygen in the arterial blood (in ml O2 /100ml blood) of an individual who has PO2=90mm Hg, PCO2=40mm Hg, Hb=15g/100ml, hemoglobin saturation = 95%, (solubility coefficient of O2=0.003 ml O2/100 ml blood/mm Hg; at saturation Hb binds 1.34 ml O2/g)

A. (0.95 x 15) + (95 x 0.003)

B. (90 x 1.34 x 15) + (95 x 0.003)

C. ((90 - 40) x 1.34 x 0.95) + (90 x 0.003)

D. (0.95x 1.34 x 15) + (90 x 0.003) (can you explain why the answer is D?)

E. none of the above

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Patrina Schowalter
Patrina SchowalterLv2
28 Sep 2019
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Related questions

The minimum time it takes a normal person to go from residual volume (RV) to total lung capacity (TLC) is less than the minimum amount of time to go from TLC to RV. The most probable explanation for this effect is: A. the chest wall tends to spring outward when the respiratory system is at RV. B. the chest wall is less compliant at RV. C. inspiratory muscles are stronger than expiratory muscles. D. the lungs have less recoil at TLC. E. the airways tend to collapse during forced expiration. (can you please explain why this is the answer)

Case Study 1: Case Presentation

John, a healthy twenty-eight year old electrical engineer, was driving home from work one evening when he experienced sudden stabbing pain in his right pectoral and right lateral axillary regions. He began to feel out of breath and both his respiratory rate and heart rate increased dramatically. As luck would have it, John passed a hospital each day on his way home and was able to get himself to the hospital’s emergency room. The emergency room physician listened to John’s breathing with a stethoscope and requested blood gas analysis and a chest x-ray. John answered a few of the doctor’s questions. The doctor noted that John had no history of respiratory problems but was a heavy smoker.

After viewing the chest radiograph, the doctor informed John that he had experienced a spontaneous pneumothorax, or what is commonly called a collapsed lung. The doctor explained that a hole had opened in John’s right lung and that this hole had allowed air to leak into the cavity surrounding the lung. Then, as a result of the lung’s own elastic nature, the lung had collapsed. The doctor said he could not be certain of the cause of the pneumothorax, but smoking cigarettes had certainly increased the likelihood of it happening. He told John he was fortunate the pneumothorax was small, which meant that relatively little air had escaped from the lung into the surrounding cavity, and it should heal on its own. He instructed John to quit smoking, avoid high altitudes, flying in nonpressurized aircraft, and scuba diving. He also had John make an appointment for a re-check and another chest x-ray.

Case Background

Spontaneous pneumothorax occurs when a blister on the surface of the lung opens, allowing air from the lung to move into the pleural cavity. This occurs because alveolar pressure is normally greater than the pressure in the pleural cavity. As air escapes from the lung, the lung tissues will recoil, and the lung will begin to collapse. The lung will continue to collapse until the difference between the alveolar pressure and pleural pressure disappears or until the collapsing of the lung causes the opening to seal.

The pneumothorax decreases the efficiency of the respiratory system, which in turn results in decreased blood oxygen concentration, increased respiratory rate, and increased heart rate. If the pneumothorax is small, the air that escapes into the pleural cavity can be reabsorbed into the lung once the opening has sealed shut. If the pneumothorax is large, a needle or chest tube may have to be inserted into the pleural cavity to draw the air out and allow for the reexpansion of the lung.

Questions

Define the following terms and explain how they may have been affected by John’s spontaneous pneumothorax.

Visceral pleura

Parietal pleura

Pleural cavity

As a result of a pneumothorax, the lung tissues recoil, and the lung collapses. Explain how recoil and collapse are prevented in a healthy lung?

How does elastic recoil function in breathing?

Why was John instructed to avoid high altitudes and flying in nonpressurized aircraft?

Case Study 2: The Case of the Coughing Housewife

Jessica, a fifty-nine year old mother of four, moved from a ranch in Colorado to Los Angeles, after the death of her husband, to be closer to her oldest son and his family. She has been in Los Angeles for 18 months and has noticed that she is experiencing shortness of breath which has worsened over the last six months. For the last week, she has been coughing and bringing up yellow mucus. She also noticed swelling in her ankles so she decided to visit a physician about her condition.

Jessica's family and medical history include a negative history of asthma or allergies, lack of occupational or home exposure to asbestos, a previous smoking history (one package of cigarettes per day between the ages of 16 and 52), episodes of bronchitis, treated with antibiotics on an outpatient basis, and a positive history of heart disease (father at 52 and brother at 56). Jessica has no history of serious illness, including heart disease, and her weight is within five pounds of her "desired" weight. She usually coughs in the morning to "clear her throat", but there is usually only a small amount of white mucus.

Her nurse practitioner conducts a general physical examination with the following results. Jessica's skin is normal (no rashes or cyanosis) and her nervous system is functioning normally. Her body temperature was 98.4oF while her pulse was regular at 95 beats per minute with an occasional premature beat. Jessica's blood pressure was within normal limits, however her jugular veins were slightly distended. Her respiratory rate was 28 breaths per minute; she breathed with pursed lips and used her accessory respiratory muscles more than would be expected. Jessica presented with a barrel chest and mild dyspnea when climbing onto the examination table. When listening to her breathing, the nurse practitioner noticed that Jessica had prolonged expiration accompanied by expiratory wheezes. Evaluation of her abdomen indicated no masses or tenderness, but she presented with both hepatomegaly and splenomegaly. All of her extremities were normal with the exception of bilaterally pedal edema.

Based on these results, the nurse practitioner suspected a pulmonary disorder and, after consultation with a physician, ordered laboratory tests (blood and sputum), spirometry and chest x-rays. The results of the laboratory tests were as follows: plasma bicarbonate = 38 mEq/L, hematocrit = 49%, white blood cell count = 9000, pH = 7.38; PaCO2 = 56, and PaO2 = 54. Analysis of the sputum sample indicated the presence of epithelial cells, polymorphonucleocytes and gram positive diplococci. Jessica's 1 second forced expiratory volume (FEV1) was 1.5 L/sec and her forced vital capacity (FVC) was 4 L. These values were 40% and 83% of normal, respectively. Results of the chest x-ray indicated scarring and hyperinflation of the lungs.

The results of these tests coupled with the physical examination and history lead to a diagnosis of emphysema. Jessica was prescribed antibiotics for the infection and oxygen by nose as well as a b2-agonist nebulizer as an acute treatment and requested to stay for observation and stabilization. After Jessica's condition was stabilized she was discharged and given a prescription for an inhaler containing a b2-agonist to be used as needed. She was also encouraged to exercise regularly and follow the nutritional guidelines she was given. Jessica was also informed that if the symptoms either worsened or did not lessen within the next week, to return and her treatment would be reevaluated and would possibly include nocturnal oxygen and an inhaler containing corticosteroids.

Answer the following questions about this case

Define the bold terms in the text. (8 points)

What risk factors and symptoms did Jessica present with prior to the physical examination that suggested a pulmonary disorder?

How did the physical examination, chest X-ray and spirometry confirm this hypothesis?

Identify muscles involved in respiration and how these muscles are responsible for the process of ventilation.

How will the b2-agonist in the inhaler help with the respiratory problems Jessica presents with?

Why is it important that a b2-agonist and not simply an b-agonist is used in the inhaler?

If her condition does not progress, why would corticosteroids be used in the inhaler?

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