Body Systems L19 Notes Flashcards
Name the factors effecting pulmonary compliance
Ease of lung expansion
Describe how the elasticity of connective tissue of the lungs is measured
- Measure -> Elastic recoil
- Lung volume changes -> pressure change
What is the equation for calculation of compliance?
- Compliance = δV / δP (litres/cm H2O)
Eg. Patient inhales 500ml air. Intrapleural pressure before insp. = -5cm H2O & -8cm at
end. Calc. compliance of lungs.
»_space; δV = 500 ml = 0.5L (0->500)
»_space; δP = (-8) – (-5) = -8 + 5 = -3cm
= δ = 3cm
»_space; Compliance = 0.5 / 3 = 0.1667L/cm H2O
Describe how surface tension is created
Surface tension
- Caused -> Intermolecular forces between mol. of liquid
- Air-fluid interface surface -> fluid
» Under tension -> (similar to stretching thin mem. Eg. Fluid layer between
alveolar cells & air)
What is Laplace’s law?
- Laplace’s Law:
» Relationship between pressure (P) , Surface Tension (T) & Radius (r) of an
alveolus (bubble).
What does Laplace’s law state?
> > At equilibrium -> Tendency of Incr. pressure expands alveolus
»_space; Balances tendency of surface tension to collapse alveolus
What is the equation for Laplace’s law?
> > P = 2T / r
Name a major factor influencing surface tension & describe what effect it has
- Pulmonary Surfactant:
» Reduces surface tension
-> Incr. compliance
Describe the role of pulmonary surfactant in reducing surface tension
> > Equalises pressure differences between large & small alveoli.
Maintains uniform alveolar size
Tension decreases as alveoli decr. in size
Enables adjustment of alveoli -> rates of inflation & deflation.
How does pulmonary surfactant maintain uniform alveolar size?
> > Maintains uniform alveolar size
- > Higher conc. -> Smaller alveoli - > Lower surface tension helps equalise pressure -> alveoli of different sizes. - > Easier inflation -> Smaller alveoli - > Energy required -> Alveolae expansion reduced with incr. no. of breaths.
Name the two factors which cause resistance to breathing
Lung volume
Bronchial Smooth muscle
What is airway resistance?
Airway Resistance
Major non-elastic source -> Gas flow resistance
Describe the effect of air resistance on gas flow
Incr. resistance -> Decr. gas flow
What is airway resistance determined by?
Resistance determined -> radius
Name the influencing factors on the radius of the airway
Lung volume
Bronchial Smooth muscle
Describe how lung volume influences airway resistance
- Lung Volume:
|»_space; Dilation -> Bronchi -> Lung expansion
Describe the two ways by which bronchial smooth muscle is influenced in order to influence airway resistance
Parasympathetic Nerves
Sympathtic nerves & adrenaline
Describe how the parasympathetic nerves effect the bronchial smooth muscle to influence airway resistance
- Bronchial Smooth Muscle:
» Parasympathetic Nerves
-> Bronchoconstriction
Describe how the sympathetic nerves & adrenaline effect the bronchial smooth muscle to influence airway resistance
> > Sympathetic Nerves & Adrenaline
-> Bronchodilation
What causes stimulation of bronchodilation by via the sympathetic nervous system & adrenaline?
> > Sympathetic Nerves & Adrenaline
- > Bronchodilation
- ->> Caused
- > Smoke & Dust irritance
- > Histamine (Allergic response)
What is the equation for measuring air resistance?
Measuring Airway Resistance:
- ( FEV1 / FVC ) x 100
What two equational factors influence airway resistance?
- Forced Vital Capacity (FVC)
- Forced Expiratory Volume (FEV1)
What is the forced vital capacity?
- Forced Vital Capacity (FVC)
» Forceable exhalation
» Little difference to VC
What is the forced expiratory volume?
- Forced Expiratory Volume (FEV1)
|»_space; Vol. of air expired per second
What is the forced expiratory volume used for?
> > Used -> Assess changes in airflow resistance
Eg. Athsmatic patients.
Expressed as & of FVC
What affect does inspiration have on lung volume & intra-pleural pressure?
Incr. Lung vol (ml)
Decr. Intra-pleural pressure (cm H2O)
What affect does expiration have on lung volume & intra-pleural pressure?
Decr. Lung vol (ml)
Incr. Intra-pleural pressure (cm H2O)
What kind of shape represents lung volume on a graph?
- Lung volume:
Positive Bell shaped curve -> Inspiration & Expiration
What is the peak value of lung volume on a graph?
> > Peak -> 500ml
What shape does intra-pleural pressure create on a graph?
- Intra-pleural pressure:
Negative (irregularly-shaped) bell curve -> Inspiration & Expiration
What is the peak value of intra-pleural pressure on a graph?
> > Peak -> -8 cm
What shape represents intra-pleural pressure on a graph if no airway resistance present?
> > If no airway resistance -> V-shaped graph
What effect does elastic recoil of the lungs have on inspiration & expiration?
- Elastic recoil -> lungs
Opposes inspiration
Aids expiration
What factors influence the value of airway resistance in the lungs?
Forced vital Capacity (FEV) Forced expiratory volume (FEV1) Inspiration Expiration Lung Volume Intra-pleural pressure Elastic recoil Surface tension -> Alveoli
Describe neonatal respiratory distress syndrome
• Neonatal Respiratory Distress Syndrome:
- Lack of surfactant secretion -> premature babies (28-32wks gestation)
» Reduced compliance
» Alveolar collapse -> Exhalation
» Difficulty -> Lung inflation
- 50% die without rapid treatment
What are the methods used to assess lung function?
Breath Sound
Pulmonary Function Tests
Spirometer
How is breath sound used to assess lung function?
Breath Sound
Presence -> mucous / fluid
Absence -> Breathing sounds -> Possible collapsed lung
How are pulmonary function tests used to assess lung function?
Pulmonary Function Tests
Peak Flow meter
» Measures speed of air exhalation
What is regularly used to assess lung function of chronic asthmatics?
> > Regularly used -> Chronic asthmatics
What is a spirometer used for? What units are it’s findings given in?
Spirometer
Measures lung volumes & capacities
Findings: (Litres)
What does a spirometer measure?
>> Inspiratory Reserve Volume (IRV) >> Tidal Volume (TV) >> Expiratory Reserve Volume (ERV) >> Residual Volume (RV) >> Total Lung Capacity
What are the normal Inspiratory Reserve Volume (IRV) values for men & women?
> Men -> 3.3
> Women -> 1.9
What are the normal Expiratory Reserve Volume (ERV) values for men & women?
> Men -> 1.0
> Women -> 0.7
What are the normal Residual Volume (RV) values for men & women?
> > Residual Volume (RV)
> Men -> 1.2
> Women -> 1.1
What are the normal Total Volume Capacity of the lungs (IRV) for men & women?
> > Total Lung Capacity
> Men -> 6.0
> Women -> 4.2
What is the Tidal volume?
• Tidal Volume: (TV)
- Volume of air inhaled / exhaled per breath
What is the functional residual capacity?
• Functional Residual Capacity:
- Volume of air remaining in lungs after normal, passive inhalation
What is the equation for the calculation of the functional residual capacity?
- > > Expiratory Reserve Volume + Residual Volume
What is the purpose of the functional residual capacity?
- Helps stabilise composition of alveolar air
What value cannot be measured using a spirometer?
Functional Residual capacity
What is the expiratory reserve volume (IRV)?
• Expiratory Reserve Volume: (ERV)
- Volume of air forcibly exhaled following normal tidal volume exhalation
What is the inspiratory reserve volume (ERV)?
• Inspiratory Reserve Volume: (IRV)
- Volume of air forcibly exhaled following normal tidal volume inhalation
What is the residual volume (RV)?
• Residual Volume: (RV)
- Volume of air remaining in lungs following max expiration
What is the vital capacity (VC)?
• Vital Capacity: (VC)
- Maximum volume of air expired after max. inspiratory effort
What is the equation for calculation of the vital capacity?
- VC = TV + IRV + ERV
What are the normal values of vital capacity (VC) for men & women?
- Normal Values:
» Men -> 4.8 L
» Women -> 4.2 L
What is the inspiratory capacity (IC) ?
• Inspiratory Capacity: (IC)
- Maximum volume of air inspired after normal expiration
What is the equation for calculation of the inspiratory capacity (IC)?
- IC = TV + IRV
What is the functional residual capacity (FRC)?
• Functional Residual Capacity: (FRV)
- Volume of air remaining in lungs following normal tidal expiration
What is the equation for calculation of the functional residual capacity (FRC)?
- FRC = RV + ERV
What is the total lung capacity (TLC)?
• Total Lung Capacity: (TLC)
- Maximum volume of air contained in lungs following maximum inspiratory effort
What is the equation for calculation of total lung capacity (TLC)?
- TLC = TV + IRV + ERV + RV
What are the normal values of total lung capacity (TLC) in men & women?
- Normal Values:
» Men -> 6.0 L
» Women -> 4.2 L
What two factors does the respiratory system alter to adapt to varying oxygen demands?
Respiratory rate
Tidal volume
What is the respiratory rate?
- Respiratory Rate
|»_space; No. of breaths per minute
What is the tidal volume?
- Tidal Volume
|»_space; Volume of air inhaled / exhaled per breath
What is the pulmonary ventilation rate?
• Pulmonary Ventilation Rate:
> > Volume of air inhaled / exhaled per minute
What is another term representing the respiratory minute volume?
• Pulmonary Ventilation Rate
How is the pulmonary ventilation rate / respiratory minute volume calculated?
Give an example of this equation numerically using the standard values found in humans for each component.
- Respiratory Rate x Tidal Volume
|»_space; 0.5 L x 12 /min = 6 L/min
What is the normal respiratory rate of adult humans?
12-15 breaths per min
What is anatomical dead space?
> > Anatomical Dead Space
-» Volume of air in conducting passages doesn’t participate in gas exchange
Doesn’t reach alveolar surfaces for gas exchange
What volume of air doesn’t reach alveolar exchange surfaces for every 0.5L tidal volume?
0.15L
What portion of the air in the respiratory system does not participate in gas exchange?
Volume of air in conducting passages doesn’t participate in gas exchange
What is alveolar ventilation?
• Alveolar Ventilation:
- Volume of air reaching alveoli per minute
What is the equation for alveolar ventilation? Give a numerical example of this equation using the standard values for each component
- [Respiratory Rate] x [(Tidal Volume) - (Anatomical dead space)]
» 12 x (0.5 – 0.15) = 4.2 L/min
What would produce variants between individuals’ lung measurements?
Lung size
List the circumstances of an individual which may lead them to have larger lung volumes
Males Taller individuals Athletes Individuals -> Higher Altitudes Non-smokers
List the circumstances of an individual which may lead them to have smaller lung volumes
Females Shorter Individuals Non-Athletes Individuals -> Lower Altitudes Smokers
List the factors affecting ease of lung expansion
Elasticity of connective tissue -> Lungs
Mobility -> Chest wall
Surface tension
What does airway resistance oppose?
Elastic tension
What are the normal tidal volumes (TV) for men & women?
> > Tidal Volume (TV)
> Men -> 0.5 – 4.8
> Women -> 0.5 – 3.1
