Physiology 2 Flashcards
Major inspiratory muscles
External intercostal muscles
Diaphragm
Accessory muscles of inspiration?
Pectoral
Sternocleidomastoic
Scalenus
What do accessory muscles of inspiration do?
Contracts only during forceful respiration
Muscles of active expiration?
Internal intercostal muscles
Abdominal Muscles
What do muscles of active expiration do?
Contracts only in active expiration
Total lung capacity?
Over 7L
Tidal Volume?
Volume of air entering or leaving lungs during a single breath
TV
0.5L
Inspiratory Reserve Volume?
Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
IRV
3.0L
Expiratory Reserve volume?
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
ERV
1.0L
Residual Volume?
Minimum volume of air remaining in the lungs even after a maximal expiration
RV
1.2L
Inspiratory Capacity?
Maximum volume of air that can be inspired at the end of a normal quiet expiration
IC
3.5L
Equation for Inspiratory capacity?
IC= IRV + TV
Functional Residual Capacity?
Volume of air in lungs at end of normal passive expiration
FRC
2,2L
Equation for FRC?
FRC=ERV+RV
Vital Capacity?
Maximum volume of air that can be moved out during a single breath following a maximal inspiration
VC
4.5L
Vital Capacity Equation?
VC= IRV + TV + ERV
Total Lung Capacity?
Total volume of air the lungs can hold
TLC
5.7L
Total lung capacity equation?
TLC= VC + RV
What can not be measured by spirometry?
Residual Volume - hence not able to measure total lung volume by spirometry
When does residual volume increase?
When the elastic recoil of lungs is lost eg emphysema
What are dynamic lung volumes useful in?
Diagnosis of obstructive, restrictive lung disease
Spirometry results for an airway obstruction?
FVC= low or normal
FEV1=low
FEV1/FVC= low
Spirometry Results for a Lung restriction
FVC= Low
FEV1=low
FEV1/FVC=normal
Spirometry results for combo of obstructuve and restrictive?
FVC=low
FEV1 =low
FEV1/FVC=low
Airway resistance equation?
F= change in P/ r
F=Flow
P=Pressure
R= Resistance
Primary determinant of resistance?
Radius of conducting airway
Parasympathetic Stimulation causes?
Bronchoconstriction
Sympathetic Stimulation causes?
Bronchodilatation
What happens during inspiration?
Airways are pulled open by the expanding thorax
Intrapleural pressure falls during inspiration
What happens during expiration?
Chest Recoils
Intrapleural pressure rises
What helps push air out of the lungs?
Pressure applied to alveolus
Dynamic airway compression in normal people?
Causes no problem
Increased airway resistance, increases in airway pressure upstream which helps open up the airways by increasing the driving pressure between the alveolus and the airways (the pressure downstream)
Dynamic airway compression in people with obstruction?
Causes a problem
Driving pressure is lost between alveolus and airway over obstructed segment- causes fall in airway pressure along the airway downstream = airway compression by rising pleural pressure during active expiration
When does dynamic compression of airways become worse in patients with an obstruction?
When the patient has decreased elastic recoil of lungs
What does a peak flow meter do?
Gives an estimated of peak flow rate
When is a peak flow test useful?
With patients who have an obstructive lung disease
How is peak flow rate measured?
Patient does short sharp blow into machine, best of 3 attempts is taken
What is pulmonary compliance?
A measure of how much effort has to go into stretching or distending the lungs
The less compliant the lungs are…
The more work is required to produce a given degree of inflation
Pulmonary compliance is decreased by?
Pulmonary oedema Pulmonary fibrosis Lung collapse pneumonia Absence of surfactant
Decreased pulmonary compliance causes?
A greater change in pressure is needed to produce a given change in volume = shortness of breath
Increased pulmonary compliance?
May occur if the elastic recoil of lungs is lost
Occurs in emphysema
What does compliance increase with?
Increased age
Energy required for quiet breathing?
3% of total energy expenditure
When is work of breathing increased?
Pulmonary compliance decreases
Airway resistance increases
Elastic recoil is decreased
Need for increased ventilation
