©2010 Mark Tuttle
Pulmonary Physiology (Metting)
Lectures
1. Pulmonary Gas Exchange: Ventilation and Diffusion
2. Mechanics of Breathing
3. Pulmonary Blood Flow & Ventilation/Perfusion Balance
4. O2 and CO2 Transport in the Blood: Hypoxia and Hypoxemia
5. Integration and Problem Solving I
6. Pathophysiology of Acid-base Disorders
7. Control of Breathing
8. Pulmonary Edema; Pulmonary Hemodynamic Monitoring
9. Clinical Evaluation of Pulmonary Function
10. Integration and Problem Solving II
Textbook Chapters
1. Function
2. Mechanics
3. Alveolar Ventilation
4. Pulmonary Blood Flow
5. Ventilation-Perfusion
6. Diffusion
7. O2 + CO2 Transport
8. Acid-Base
9. Control of breathing
10. Nonrespiratory functions of the lung
11. Stress
1. Pulmonary Gas Exchange: Ventilation and Diffusion
Gas
PO2
PCO2
PN2
PH2O
TOTAL
Humidified
Inspired Air
(Dead Space)
149 (20.93%)
0.3 (0.04%)
563 (79%)
47
760
Dry Air
159 (20.93%)
0.3 (0.04%)
600 (79%)
0.0
760
-1 mmHg for years > 60
Alveolar Air
104 (14.6%)
40 (5.6%)
569 (79.8%)
47
760
Expired Air
120 (16.8%)
27 (3.8%)
566 (79.4%)
47
760
Arterial Blood
100 (80-100)
40
573
47
760
Mixed Venous
Blood
40
46
573
47
760
4. O2 and CO2 Transport in the Blood: Hypoxia and Hypoxemia
Cause of Hypoxemia
Normal
PaO2
100
Normal Air
Mixed PAO2 A-aPO2
104
15
Hypoventilation
↓
↓
Normal ↑
Low V/Q
↓
Normal
↑
↓
Normal Normal pneumothorax, pneumoconio, CF, obstructed
R→L Shunt
↓
Normal
↑
↓
↓
Diffusion Impairment ↓
Normal
↑
PaCO2
40
↓
100% O2
PaO2
A-aPO2
>500
100
Underlying Condition
Skeletal, neuromuscular, Pickwickian
Normal Normal syndrome, sleep apnea
COPD, atelectasis, pneumonia, PE, ARDS,
↑↑
Normal Normal
Congenital, atelectasis, pneumonia, edema,
airway obstruction, pneumothorax
Pneumoconiosis, pulmonary edema, druginduced pulmonary fibrosis (bleomycin),
collagen–vascular diseases
Chemoreceptor reflex , Hyperventilation dominates
R-L Shunts (V/Q=0)
- Anatomic
o Normally: 3-5% of cardiac output.
Ex. Bronchial/pleural veins  pulmonary veins, Thebesian veins
- Physiological (intrapulmonary) Shunt
o  which are Q not V
Ex. Atelectasis, pneumonia, edema, airway obstruction, pneumothorax
DDx of signs of hypoxia
Hypoxemia PaO2 
O2 Absorption
O2 Delivery
O2 Utilization
Altitude
Delivery
Impairment
PB + PaO2 
Cardiac output + PaO2  Histiotoxic (ex.
Cyanide)
Hypoventilation PaCO2 
Stagnant
Cardiac output 
(hypoperfusion)
Anemia
[Hb] 
CO Poisoning
SaO2 
O2 Extraction ,
PvO2, SvO2 
©2010 Mark Tuttle
Pulmonary Physiology (Metting)
2. Mechanics of Breathing
Tidal Inspiration
• Diaphragm
• External Intercostals
Accessory Muscles
• Scalenes
• Sternocleidomastoid
• Trapezius
Expiration
• Normally passive, due to elastic
recoil of the lung
During a forced expiration
• Abdominal Muscles
• Internal Intercostal Muscles
Bronchodilation
- Sympathetic stimulation
- β2-adrenergic agonists
- VIP
- Anti-cholinergics
- Anti-leukotrienes
- Nitric oxide
- Methylxanthines
- ↑ PACO2 in small airways
- ↓ PAO2 in small airways
but ↓ PAO2 is also a
vasoconstrictor
Volumes
VT:
500 ml
IRV:
2.5 L
ERV: 1.5 L
RV:
1.5 L
Capacities
IC:
3L
FRC: 3 L
VC:
4.5 L
TLC:
6L
Bronchoconstriction
- Parasympathetic stimulation
- Acetylcholine
- α-adrenergic agonists
- Histamine
- Leukotrienes (LTD4 is 1000-fold more potent than histamine)
- Serotonin
- Thromboxane A2
- Substance P
- Adenosine (via A1 receptor) (Also is a vasodilator)
- Platelet activating factor
- Prostaglandin D2
- ↓ PACO2 in small airways
3. Pulmonary Blood Flow & Ventilation/Perfusion Balance
 PVR: Pulmonary Vasoconstriction
 PVR: Pulmonary Vasodilation
-  PAO2 (hypoxic pulmonary vasoconstriction) - Parasympathetic stimulation and acetylcholine
(M3 muscarinic receptors)
-  PACO2
Beta2 adrenergic agonists
- low pH of mixed venous blood
- Nitric oxide (endothelial-derived relaxing
- Sympathetic stimulation ()
factor)
- Norepinephrine, epinephrine, and alpha
Bradykinin
adrenergic agonists
- PGI2
- Angiotensin II
- Endothelin antagonists
- Thromboxane A2
- Endothelin
- Histamine
Passive Factors
1. Lung Volume
2. Blood Pressure, Flow, and Volume in the Pulmonary Circulation
3. Positive Pressure Ventilation
4. Gravity (hydrostatic pressures)
5. Formative Evaluation/Group Discussion: Integration and Problem Solving
Pulmonary Physiology (Metting)
6. Pathophysiology of Acid-base Disorders
Causes of Respiratory Acidosis (Hypoventilation)
I. Airway Obstruction
A. Chronic Obstructive Lung Disease
B. Upper Airway Obstruction
II. Chest Wall Restriction
A. Kyphoscoliosis
B. Pickwickian Syndrome (obesity)
III. Respiratory Center Depression
A. Anesthetics
B. Sedatives
C. Opiates
D. Brain injury or disease
E. Severe hypercapnia (PaCO2↑), hypoxia
IV. Neuromuscular disorders
A. Spinal cord injury
B. Phrenic nerve injury
C. Poliomyelitis
D. Myasthenia Gravis
E. Guillian-Barré Syndrome
F. Administration of Curare-like Drugs
G. Respiratory Muscle Diseases
Causes of Metabolic Acidosis
Hyperchloremic – Normal anion gap
I. Gastrointestinal loss of HCO3_
A. Diarrhea
B. Small bowel/pancreatic drainage / fistula
C. Ureterosigmoidostomy, jejunal loop,
ileal loop conduit
D. Drugs
II. Renal Loss of HCO3_
A. Carbonic anhydrase inhibitors
B. Renal tubular acidosis (RTA)
III. Miscellaneous
A. Dilutional acidosis
B. Hyperalimentation
Normochloremic – increased anion gap
I. Lactic Acidosis
II. Ketoacidosis
A. Diabetic
B. Starvation
C. Alcoholic
III. Ingestion of Toxic Substances
A. Salicylate overdose
B. Paraldehyde poisoning
C. Methyl alcohol ingestion
D. Ethylene glycol ingestion
IV. Failure of Acid Excretion
A. Acute renal failure
©2010 Mark Tuttle
Causes of Respiratory Alkalosis (Hyperventilation)
I. Respiratory Center Stimulation
A. CNS
1. Anxiety
2. Hyperventilation Syndrome
3. Inflammation (encephalitis, meningitis)
4. Stroke
5. Tumors
B. Drugs or Hormones
1. Salicylates
2. Progesterone
3. Hyperthyroidism
C. Reflex
1. Hypoxemia
2. High Altitude
3. Metabolic Acidosis
4. Sepsis, fever
5. Pulmonary Embolism
6. Pulmonary Edema
7. Congestive Heart Failure
8. Asthma
II. Iatrogenic Mechanical Overventilation
III. Liver Failure
Causes of Metabolic Alkalosis
I. Loss of Hydrogen Ions
A. Vomiting
B. Nasogastric Suction
C. Gastric fistulas
D. Diuretic therapy
E. Severe Magnesium or Potassium Deficiency
F. Overproduction of mineralocorticoids
(Cushing’s syndrome; Primary hyperaldosteronism; renal artery
stenosis)
G. Ingestion of mineralocorticoids
(Licorice ingestion; chewing tobacco)
H. Inherited Disorders
(Bartter’s Syndrome; Liddle’s syndrome; Gitelman’s)
II. Ingestion or administration of excess bicarbonate or other
bases
A. Intravenous bicarbonate
B. Ingestion of bicarbonate or other bases (e.g., antacids)
Pulmonary Physiology (Metting)
B. Chronic renal failure
7. Control of Breathing
8. Pathophysiology of Pulmonary Edema; Pulmonary Hemodynamic Monitoring
9. Clinical Evaluation of Pulmonary Function
10. Formative Evaluation/Group Discussion: Integration and Problem Solving II
©2010 Mark Tuttle