Physiology Flashcards
Tidal Volume
Amount of gas inspired and expired with each breath
Inspiratory Reserve Volume
Maximum amount of additional air that can be inspired from the end of a normal inspiration
Expiratory Reserve Volume
Maximum volume of additional air that can be inspired from the end of a normal expiration
Residual Volume
Volume of air remaining in the lung after a maximal expiration
(ONLY lung volume that cannot be measured w/ spirometry)
Total Lung Capacity
Volume of air contained in the lungs at the end of a maximal inspiration
TLC=RV+IRV+TV+ERV
Vital Capacity
Maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration
VC=IRV+TV+ERV
or
VC=TLC-RV
Functional Residual Capacity
Volume of air remaining in the lung at the end of a normal expiration
FRC=RV+ERV
Inspiratory Capacity
Maximum volume of air that can be inspired from end expiratory position
IC=TV+IRV
How can residual volume be measured?
- Gas Dilution Techniques
- Nitrogen Washout
- Poorly ventilated or non-ventilated areas not included in FRC
- Helium Dilution
- Poorly ventilated or non-ventilated areas not included in FRC
- Nitrogen Washout
- Body Plethysmography
- Non-ventilated areas ARE included in FRC
- Radiographic Determination
- Non-ventilated areas ARE included in FRC
Obstructive Diseases
- Emphysema
- Chronic Bronchitis
- Asthma
Decrease VC
Increase TLC, RV, FRC
Restrictive Diseases
- Fibrosis
- Sarcoidosis
- Muscular Diseases
- Chestwall Deformities
Decreased VC
Decreased TLC, RV, FRC
Pulmonary factors that can reduce vital capacity?
- Absolute reduction in distensible lung tissue
- Pneumonectomy
- Atelectasis
- Increase Stiffness of Lungs
- Alveolar Edema
- Respiratory Distress Syndrome
- Infiltrative Interstitial Lung Disease
- Increased Residual Volume
- Emphysema
- Asthma
- Lung Cysts
Extrapulmonary factors that can reduce vital capacity?
- Limited Thoracic Expansion
- Kyphoscoliosis
- Pleural Fibrosis
- Limitations on Diaphragmatic Descent
- Ascites
- Pregnancy
- Nerve or Muscle Dysfunction
- Pain from surgery or rib fracture
- Primary Neuromuscular Disease (Guillain-Barre Syndrome)
Minute Ventilation
= VT * f
Alveolar Ventilation
- = VE - Vd = (VT - Vd)f = VTf - Vdf
- If tidal volume increases alveolar ventilation increases but dead space ventilation is unchanged
- Respiratory frequency increases both alveolar ventilation and dead space ventilation and thus is less effecient at increasing alveolar ventilation
Factors Determining Alveolar PCO2
- Increased carbon dioxide production increases alveolar PCO2
- Increased alveolar ventilation will dilute alveolar PCO2
- PACO2 = (VCO2/VA) * 863 mmHg
Factors that Increase VCO2
- Exercise
- Fever
- Hyperthyroidism
Factors Determining PO2
- Increased metabolic activity increases oxygen uptake and decreases alveolar PO2
- Increased alveolar ventilation increases flow of fresh air through alveoli and increases PO2
Alveolar Gas Equation
PAO2 = PIO2 - (PACO2/R)
A-a Difference
- PAO2 is normally 5-20 mmHg greater than the PaO2
- Increases w/ pulmonary disease
- Normal range changes when breathing 100% O2
a/A PO2 Ratio
- Normally averages just over 0.8
- Ratio falls w/ pulmonary disease
- Remains fairly constant w/ supplemental oxygen
When calculating venous admixture, what can be used to estimate the end-capillary PcO2?
PAO2
Bohr Equation for Physiological Dead Space
(Vd/VT) = (PaCO2 - PECO2)/PaCO2
Right Atrial Pressure
Near 0 mmHg
Right Ventricle
Systolic = 25 mmHg
Diastolic = 0 mmHg
Pulmonary Artery
Mean = 15 mmHg
Systolic = 25 mmHg
Diastolic = 8 mmHg
Site of Major Pressure Drop in Pulmonary Circulation
Capillaries
Site of Major Pressure Drop in Systemic Circulation
Arterioles
Site of Greatest Pulmonary Vascular Resistance
Pulmonary Capillaries
What causes collapsing of of alveolar vessels?
- Expansion of extra-alveolar vessels
- Stretching of alveolar walls
Hypoxic Vasoconstriction
- Begins when PAO2 falls below 60
- Beneficial in that blood flow goes to ventilated areas where gas exchange can occur
Substances that contract pulmonary vascular smooth muscle?
- Serotonin
- Histamine
- Norepinephrine
Substances that relax pulmonary vascular smooth muscle?
- Prostaglandins
- Leukotrienes
- Isoproterenol
- Acetylcholine
Fick Equation
Q = VO2/(CaO2 - CvO2)
- Calculations will end up in dl/min
Zone 1 of the lung?
PALV > PPA > PPV
NO Flow, Completely Collapsed
Not normally found in man, but may occur w/ hemorrhage or during positive pressure ventilation
Zone 2 of the lung?
PPA > PALV > PPV
Partial Collapse
Zone 3 of the lung?
PPA > PPV > PALV
Blood Vessels Fully Open
L to R Shunt
Systemic arterial blood (oxygenated) which contaminates pulmonary arterial blood (deoxygenated)
Venous Admixture
- Physiological R to L Shunt
- Occurs when deoxygenated blood contaminates normally oxygenated blood
- Two factors that determine the effect of R to L Shunt
- Amount of deoxygenated blood that is added
- Saturation and thus the O2 content of the shunted blood
- = (CcO2 - CaO2) / (CcO2 - CvO2)
- PcO2 = PAO2
- CcO2 = 1.36 * [Hb] * ScO2
Physiological Functions of Pulmonary Circulation
- Gas Exchange
- Filter
- Blood Reservoir for L Ventricle
- Supply Nutrients to Lung Itself
- Fluid Exchange
- Angiotensin Converting Enzyme
Where does the greatest fall in oxygen tension occur?
Across Systemic Capillaries
Normal PvO2
40 mmHg
Functions of Myoglobin
- Buffer changes in tissue PO2 during changes in cellular metabolism
- Facilitate O2 diffusion through the cytoplasm to the mitochondria where the O2 is used
P50 of Myoglobin
2.7 mmHg
What affects arterial PaO2?
- Target alveolar PAO2
- Condition of gas exchange surfaces
- **Hb factors DO NOT alter PaO2**
P50 of Hemoglobin
27 mmHg
Blood PO2 of what corresponds with 50% O2 Saturation?
27 mmHg
Blood PO2 of what corresponds with 90% O2 Saturation?
60 mmHg
Blood PO2 of what corresponds with 75% O2 Saturation?
40 mmHg
Blood PO2 of what corresponds with 97% O2 Saturation?
100 mmHg
What direction does the oxygen dissociation curve shift w/ decreased hemoglobin affinity for O2?
Right
What direction does the oxygen dissociation curve shift w/ increased hemoglobin affinity for O2?
Left