Unit 3 Day 2 (Wed 4/22) Flashcards
Minute Ventilation
- volume of air flow through the lung in one minute = 6 L
- minute ventilation = tidal volume x breathing rate
Alveolar Ventilation
- V(A)
- volume of air flow in alveolar space in one minute (4.2 L)
Factors That Influence Lung Ventilation
- Obstructive disease (e.g., COPD)
- Compliance problems
- Exercise (ventilation can increase up to 10-fold)
- High altitude
- Gravity (introduces regional variations in ventilation)
Total Work Breathing
Total Work = Elastic Work + Resistance Work
Total Work Breathing
Total Work = Elastic Work + Resistance Work
- elastic work- effort it takes to expand lungs
- -high at high tidal volume and low frequency
- resistance- effort it takes to open lungs against resistance in airway
- -high at low tidal volume and high frequency
Anatomical Dead Space
- 30% of total lung volume
- dead space is volume of lung that does not exchange gas
- the dead space in that portion of the respiratory system which is external to the alveoli and includes the air-conveying ducts from the nostrils to the terminal bronchioles
Alveolar Dead Space
-The difference between physiological dead space and anatomical dead space, representing that part of the physiological dead space resulting from ventilation of relatively underperfused or nonperfused alveoli.
Physiologic Dead Space
- physiologic dead space = anatomical dead space + alveolar dead space
- the total dead space in the entire respiratory system including the alveoli
Residual Volume (RV)
-the volume of air remaining in the lungs after a maximal exhalation
Functional Residual Capacity (FRC)
-the volume in the lungs at the end-expiratory position
Total Lung Capacity (TLC)
-the volume in the lungs at maximal inflation, the sum of VC and RV
Vital Capacity (VC)
-the volume of air breathed out after the deepest inhalation.
Forced Expiratory Volume 1 (FEV1)
-Volume that has been exhaled at the end of the first second of forced expiration
Forced Vital Capacity (FVC)
-the determination of the vital capacity from a maximally forced expiratory effort
FEV1/FVC
- calculated ratio used in the diagnosis of obstructive and restrictive lung disease
- It represents the proportion of a person’s vital capacity that they are able to expire in the first second of expiration
- normal values are approximately 80%
RV, FRC, TLC, VC, FEV1/FVC in Pulmonary Fibrosis (restrictive)
- RV: dec
- FRC: dec
- TLC: DEC.
- VC: DEC.
- FEV1/FVC: no change or small inc.
RV, FRC, TLC, VC, FEV1/FVC in Bronchitis (obstructive)
- RV: inc.
- FRC: inc.
- TLC: same
- VC: dec.
- FEV1/FVC: DEC.
Partial Pressure of Inspired Oxygen (PiO2)
- can vary by altitude
- dalton’s law: PiO2 = (PB - 47 torr) x FO2
- if breathing 100% O2, FO2 = 100%, PiO2 = 713 torr
- typical PiO2 at sea leve: 150
- typical PiO2 at altitude: 40 torr
Respiratory Exchange Ratio (R)
R = CO2 produced / O2 consumed
Alveolar Gas Equation
PAO2 = PiO2 - (PACO2/R)
______ is rate-limiting step in CO2 removal from blood.
ventilation
Alveolar Ventilation Equation
PaCO2 = (VCO2/Va) x k
-can substitute PACO2 for PaCO2
Hypoventilation
-low VA and high PaCO2, happens during severe obstructive disease
Hyperventilation
-high VA and low PaCO2, happens at high altitude
Hyperpnia
-high VA and normal PaCO2, happens during exercise
Solubility Coefficient
- aO2 = 0.0013 mM/torr
- aCO2 = 0.03 mM/torr
Oxyhemoglobin Dissociation Curve
- pressure on x axis
- O2 saturation on y axis
- S shaped curve
Diffusion Disorders
- interstitial lung disease (inc. distance between alveoli and capillary)
- emphysema (dec. surface area due to breakdown in lung tissue)
Perfusion
- blood flow in lung
- factors that affect perfusion: O2 tension (in hypoxia, vasoconstriction occurs), capillary recruitment, gravity (more at bottom than top of lung)
V/Q mismatch
- V = ventilation
- Q = perfusion
- different in different parts of lung
- V/Q mismatch will lower PaO2
- V/Q mismatch can affect O2, but will not affect CO2
Causes of V/Q Mismatch
- resistance/compliance problems (mild to moderate as well as severe disease conditions can cause V/Q mismatch)
- pulmonary embolism
- gravity
Gravity Effect on Ventilation and Perfusion in Upright Person
- high perfusion in lower lung
- high ventilation in upper lung
Oxygen Off-Loading
- before oxygen can be taken up it must unbind from hemoglobin (oxygen offloading)
- reduced affinity for O2 corresponds to inc. O2 off-loading
- affected by PCO2, temp, [H+], 2, 3 diphosphoglycerate (hypoxia)
O2 Carrying Capacity
-maximal O2 that can be carried by a particular amount of Hb
DO2
-volume of O2 delivered in 1 minute
Hypoxemia
-PaO2
Ways CO2 is Carried in Blood
- dissolved gas
- bicarbonate produced in reaction with H2O (highly soluble)
- carbamino compounds- tranported on proteins (hemoglobin)
