Lab 4: Respiratory Physiology and Pathophysiology This exercise is completed as an in class activity and including the time for the PhysioEx 9.0 demonstration this activity requires ~ 1 hour to complete in small groups. The data for the effects of Radius on Ventilation and Comparative Spirometry come from PhysioEx 9.0, but could be provided from other sources. It is helpful to include spirograms for the Comparative Spirometry. Variable Definition Tidal volume (TV) Expiratory reserve volume (ERV) Inspiratory reserve volume (IRV) Functional vital capacity (FVC) Forced expiratory volume in 1 sec (FEV 1 ) Residual volume (RV) Total lung capacity (TLC) FEV 1 /FVC Clinical significance:
OBSTRUCTIVE VS. RESTRICTIVE LUNG DISEASES Obstructive and restrictive lung diseases share the same major symptom: shortness of breath with exertion. Individuals with obstructive lung disease have difficulty fully exhaling all the air in their lungs while individuals with restrictive lung disease have difficulty fully expanding their lungs during an inhalation. People with obstructive lung disease experience shortness of breath because damage to the lungs or narrowing of the airways causes exhaled air to leave the lungs more slowly, consequently at the end of a full exhalation, an abnormally high amount of air remains in the lungs. Restrictive lung disease most often results from conditions that cause lung stiffness; however, they can also result from stiffness of the chest wall, weak muscles, or damaged nerves that inhibit lung expansion. 1. How and why does FVC change in patients with a restrictive vs. obstructive lung disease compared to a healthy person? 2. How and why does FEV 1 change in patients with a restrictive vs. obstructive lung disease compared to a healthy person? 3. How and why does FVC/FEV 1 change in patients with a restrictive vs. obstructive lung disease compared to a healthy person?
Table 1: Effects of Radius on Ventilation Radius Flow TV ERV IRV RV FVC FEV 1 TLC Rate 5 7500 500 1200 3091 1200 4791 3541 5991 15 4 3075 205 492 1266 1908 1962 1422 3871 15 3 975 65 156 401 2244 621 436 2865 15 Calculate minute ventilation for a radius = 4. Calculate alveolar ventilation for a radius = 5 if dead space is 140 ml Table 2: Effects of Radius on FEV1/FVC Radius FEV 1 FVC FEV 1 /FVC (%) 5 4 3 Do these changes in radius classify this disease as obstructive or restrictive based upon the changes in FEV 1 /FVC and why?
Table 3: Comparative Spirometry Patient TV ERV IRV RV FVC TLC FEV 1 Normal 500 1500 3000 1000 5000 6000 4000 Emphysema 500 750 2000 2750 3250 6000 1625 Asthma 500 750 2700 2250 3750 6000 1500 + inhaler 500 1500 2800 1200 4800 6000 3840 FEV 1 /FVC (%) Emphysema: Significant destruction of alveoli and loss of elastic recoil in the lung tissue. Expiration, which is normally passive, requires significant muscular effort while inspiration may become easier because the lung is overly compliant. What 3 values changed the most (from a normal patient) in the spirogram from an emphysema patient? Why do you think the RV is increased with emphysema and how would this contribute to the barrel-chested appearance of some individuals with emphysema? Acute Asthma Attack: Smooth muscle contractions, airway inflammation and swelling, and increased mucous secretion significantly increase airway resistance. During an asthma attack, narrowed airways make it harder to breathe, and you cause coughing and wheezing. What 2 values changed the most (from a normal patient)? Based on FEV 1 /FVC ratio is asthma a restrictive or obstructive disease?
An inhaler induces bronchiole dilation and may also contain an anti-inflammatory drug. Did all the lung values return to normal with the inhaler? What value remained the farthest from normal values based on % change from normal values?
HIGH ALTITUDE EXPEDITION Sally and Helen are planning a hike up Pikes Peak and have heard about how higher altitudes can affect the amount of oxygen in your alveoli and arterial blood. Consequently, less oxygen is delivered to your working muscles as you climb to the peak which will make you feel more tired and out of breath. 1. Using Daltons Law, what is the partial pressure of oxygen (PiO2) at sea level (760 mm Hg), top of Pikes Peak (450 mm Hg) and top of Mt. Everest (253 mm Hg). 2. Using the Alveolar Gas Equation calculate the partial pressure of oxygen in the alveoli (P A O2) at sea level, top of Pikes Peak, and top of Mt Everest (assume a respiratory exchange ratio (RQ) = 0.8). http://easycalculation.com/medical/alveolar-gas-equation.php Table 1: Effects of Altitude on Oxygen Partial Pressures Altitude (ft) Barometric Pressure (mmhg) Sea Level 0 760 FiO 2 (%) PiO 2 (mm Hg) P A O 2 (mm Hg) Pikes Peak 14.114 450 Mt Everest 29,028 253
Table 2: Types of Hypoxia (decreased oxygenation) Definition Hypoxic hypoxia Causes Anemic hypoxia Ischemic hypoxia Histotoxic hypoxia
3. Which of these type(s) of hypoxia would occur as you climbed up Pikes Peak? 4. Sally recently found out that her hemoglobin level is low ([Hb]=9 g/dl) and can be classified as anemia. Calculate the arterial oxygen content of Sally and Helen s blood (Helen [Hb]=14 g/dl) using the following equation and/or online calculator. Estimate the (% saturation (SaO 2 ) using the oxygen-hb dissociation curve. Arterial oxygen content (CaO 2 )= ([Hb] x 1.36 x SaO 2 ) + (0.0031 x PaO 2 ) SaO 2 = % of hemoglobin saturated with oxygen (Normal range: 93-100%) [Hb] = hemoglobin concentration (Normal range [Adults]: Male: 13-18 g/dl; Female: 12-16 g/dl) PaO 2 = Arterial oxygen partial pressure (Normal range: 80-100 mm Hg) CaO 2 : Directly reflects the total number of oxygen molecules in arterial blood (both bound and unbound to hemoglobin) http://www-users.med.cornell.edu/~spon/picu/calc/oxycont.htm Sally Helen [Hb] g/dl PaO 2 (mm Hg) SaO 2 (%) CaO 2 (vol%) 5. Both Sally and Helen are struggling to keep up their hiking pace as they get closer to the peak; however, Sally is having much more difficulty than Helen. Why do you think Sally is having a more difficult time?