Updated: 1/23/2018

V/Q Mismatch

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This illustration compares ventilation (V) and blood flow (Q) in the three zones of the lung. 

V/Q Ratio
  • "Normal" V/Q = 0.8
    • V = alveolar ventilation
    • Q = pulmonary blood flow (perfusion)
  • "Normal" V/Q depends on "normal" respiratory rate, tidal volume, and cardiac output
    • PaO2 = 100 mm Hg
    • PaCO2 = 40 mm Hg
  • Ventilation/perfusion matching is essential for ideal gas exchange of O2 and CO2
    • "ideal" V/Q = 1.0
    • exercise  ↑ cardiac output  vasodilation of apical arteries
      • V/Q approaches 1.0
Distribution of V/Q in Lung
  • Ventilation and perfusion are nonuniformly distributed in normal, upright lung
  • Zone 1
    • apex of lung 
    • decreased ventilation and decreased perfusion
    • V/Q is highest (= 3.0) because of relatively greater decrease in perfusion 
      • wasted ventilation
      • PaO2 is highest and PaCO2 is lowest
        • organisms that thrive in high O2 (e.g., TB) flourish in apex of lung
  • Zone 3
    • base of lung
    • V/Q is lowest (= 0.6)
      • wasted perfusion
      • PaO2 is lowest and PaCO2 is highest
V/Q Defects
  • Dead Space (V/Q → ∞)
    • e.g., pulmonary embolism (blood flow obstruction)
    • ventilation of lung regions that are not perfused
      • wasted ventilation
      • physiologic dead space
      • no gas exchange occurs
        • PAO2 has same composition as humidified, inspired air (= 150 mm Hg)
        • PACO2 = 0 mm Hg
    • 100% O2 improves PaO2
  • Shunt (V/Q = 0)
    • e.g., airway obstruction, 
    • dependent portion of lung in ARDS can act as "shunt" 
    • perfusion of lung regions that are not ventilated
      • wasted perfusion
      • no gas exchange
        • pulmonary capillary blood has same composition as venous blood
      • 100% O2 does not improve PaO2
 

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Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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(M1.PL.27) In which of the following pathological states would the oxygen content of the trachea resemble the oxygen content in the affected alveoli? Review Topic

QID: 100830
1

Emphysema

17%

(1/6)

2

Pulmonary fibrosis

17%

(1/6)

3

Pulmonary embolism

17%

(1/6)

4

Foreign body obstruction distal to the trachea

17%

(1/6)

5

Exercise

33%

(2/6)

M1

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(M1.PL.15) A child accidentally aspirates a small pebble that lodges in the lower portion of the right inferior lobe. A radiograph is shown in Figure A. What changes are expected to occur in the arterial blood supply for this portion of the lung?
Review Topic

QID: 100818
FIGURES:
1

Increased, secondary to arterial vasodilation

0%

(0/8)

2

Increased, secondary to active hyperemia

0%

(0/8)

3

No change, due to autoregulation

25%

(2/8)

4

Decreased, secondary to arterial vasoconstriction

75%

(6/8)

5

Decreased, secondary to a decrease in surfactant synthesis

0%

(0/8)

M1

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