Chapter 23 Notes Continued
The Respiratory System

Spirometry and Gas Pressures

7. Spirometry: measures air volume in lungs

• Tidal Volume  500 mls
• Expiratory Reserve Volume 1200 mls
• Inspiratory Reserve Volume 3000 mls
• Inspiratory Capacity 3500 mls, TV + IRV
• Forced Vital Capacity or Vital Capacity 4700 mls, TV + ERV + IRV

• Residual Volume 1200 mls (air left in lungs after ERV)
• Total Lung Capacity 5900 mls, VC + RV
• Minute Volume 6000 mls, (Respirations per minute X TV)
• Anatomical Dead Air Space 150 mls
• Pulmonary Ventilation 4200 mls (volume of air in alveoli per minute)

• Forced Expiratory Volume at least 79% of FVC
• FEV1: amount of air forcible exhaled in first second
• FEV2: amount of air forcible exhaled in second second
• FEV3: amount of air forcible exhaled in third second

Forced Expiration online

8. Obstructive Pulmonary Diseases

• decreased ability to exhale normally
• loss of elastic recoil and increased airway resistance
• airway collapses due to breakdown of structures supporting bronchioles and air is trapped
• FEV timed measures this, FEV1 decreases
• RV is increased
• VC is often normal
• result is high carbon dioxide levels
• COPD: chronic obstructive pulmonary disease: bronchitis, emphysema,
  asthma (constriction of smooth muscle in bronchioles and inflammation,
  in COPD compressed air used for respiratory treatment not oxygen

9. Restrictive Pulmonary Disease

• compliance decreases
• loss of lung volume and total lung capacity
• FVC measures this, FVC is decreased
• lung inflammation, fibrosis, neuromuscular diseases

10. Partial pressure of Respiratory Gases

• partial pressure of gases
• 760 mmHg = sum pressure of all gases
• N = 597, O = 160, CO₂ = .3
• each gas moves independently by diffusion

Gas Pressures in the various compartments of the body

Atmospheric Air           Alveolar Air         Veins                     Arteries                 Tissue Cells
     

pO2        160 mmHg                       105 mmHg    à     40 mmHg              105 mmHg    à      40 mmHg

                                                                       O2 loading                                            O2 unloading

pCO2        .3  mmHg                        40 mmHg    ß    45 mmHg                   40 mmHg    ß     45 mmHg

pN2        597 mmHg                        569 mmHg           569 mmHg                 569 mmHg             

                                                                      alveolar capillary                                       cell membrane

                                                                           membrane

            Nitrogen narcosis
            - nitrogen has no effect on body until under pressure
            - then it dissolves in body fluids
            - at 100'  auras of the deep
            - fast decompression does not allow nitogen to escape from lungs
            - nitrogen bubbles in tissues and joints    "bends"

            High altitude sickness
            - less O₂ in atmosphere = less O₂ in alveoli
            - dizziness, vomiting, fatigue, fainting

 Morphine
- shallow breathing and slow respiration rate

Factors Affecting the Movement of Gases

11. Transport of OXYGEN

• carried on Hb molecules of red blood cells
• at a pO₂ of 105 mmHg, hemoglobin molecule is saturated
• online Hemoglobin molecule using Chime
• oxygen/hemoglobin dissociation curve shows the  relationship between percent saturation of Hb and partial pressure of O₂

- arteries: pO₂ of 100 = 98% fully saturated
- veins: pO₂ of 40 = 75% partially saturated (this is a 5   
   minute O₂ reserve)
- online description

• O₂ enters blood for 3 reasons

- difference in partial pressure
- thin alveolar capillary membrane
- breathing depth and rate

• O₂ enters the tissues for 3 reasons

- pH: low pH due to C0₂ release from tissues or lactic acid from   
  muscles, saturation curve moves to the right
- temperature: higher temperature due to metabolism, exercise, 
  fever, saturation curve moves to the right
- BPG: BPG accumulates as red blood cells do not use O₂,
   saturation curve moves to the right

• hypoxia is inadequate oxygen to cells
• oxyhemoglobin experiment online

12. Transport of CARBON DIOXIDE

• total blood CO₂ carried three ways

- dissolved in plasma, 7%
- binds onto globin portion of Hb, 23%
- as the bicarbonate ion,  HCO₃^-, 70%

- CO₂ + H₂0 ------------> H₂CO3 ----------> H⁺ +  HCO₃^-

1. CO₂ enters capillaries then red blood cells where the  
    above reaction occurs
2. H⁺ combines with Hb
3. HCO₃^- enters plasma in exchange for Cl^-
4. in lungs where pO₂ is high, reaction reverses

- H⁺ +  HCO₃^- -----------> H₂CO₃ ----------> CO₂ + H₂0

13. Nervous Control of Respiration

• Medulla Oblongata

- respiratory center
- impulses carried over PHRENIC and intercostal nerves
- inspirations for 2 seconds
- expirations 3 seconds neurons inactive

• Pons

- pneumotaxic center: inhibits inspirations allows normal  
  or forced expirations
- apneustic center; long inspirations, inhibits expirations

• Chemoreceptors

- aortic body; send impulses over X to medulla
- carotid bodies; send impulses over IX
- in hypercapnia, too much pCO₂, 
   impulses sent to inspiratory center causing  hyperventilation
- in hypocapnia, too little pCO₂,
   no impulses causing hypoventilation

14. Respiratory Acidosis/Alkalosis

• Respiratory System plays a key role in ABG’s
• pCO₂ is influenced only by respiratory parameters, THE LUNGS
• High pCO₂ means more H⁺ and a low pH
• Low pCO₂ means fewer H⁺ and a high pH
• in either case carbonic acid (a weak acid) and sodium bicarbonate
     (the salt of the weak acid) are the buffer pair to maintain a pH of   7.35
• with more H⁺, bicarbonate will remove excess and form carbonic acid
      H⁺ + HCO₃^- --------->H₂CO3
• with fewer H⁺, carbonic acid dissociates to add H⁺        
      H₂CO₃ -------> H⁺ + HCO₃^-

RESPIRATORY ACIDOSIS - HYPERCAPNIA

• causes

1. CNS depressed due to CVA's, tumors, narcotic overdose
2. neuromuscular diseases
3. chest trauma
4. acute lung disease

• increase in blood pCO₂,  (pCO₂ not eliminated at a normal rate)
• decrease in blood pH,  (pCO₂ above 45 in arteries, pH below 7.35)
•  buffer: HCO₃^-  is used as a buffer and    carbonic acid is formed from combination of H⁺ and HCO₃^-
• oxyhemoglobin curve shifts to the right
• decrease in blood pO₂ BPG is red blood cells increases and pO₂ falls
• increased respirations to blow off CO₂
• compensation by kidneys increase in blood  HCO₃^-, ( kidneys  by holding Na⁺ and  HCO₃^- (buffer) while excreting H⁺ in urine

RESPIRATORY ALKALOSIS - HYPOCAPNIA

• causes

1. CNS overstimulated - anxiety
2. high altitude
3. injury to respiratory center due to CVA's

• decrease in blood pCO₂  - pCO₂ eliminated too rapidly
• increase in blood pH  - pCO₂ below 35 in arteries, pH above 7.35
• oxyhemoglobin curve shifts to the left
• buffer: carbonic acid is used as the buffer and is depleted
• chemoreceptors increase heart rate
• compensation decrease in blood HCO₃^- kidneys eliminate   HCO₃^- (buffer) while holding H⁺  in urine