Respiratory Mechanics Lecture 2 Flashcards
What are the three muscle classifications of respiration?
Major inspiration muscles, accessory muscles of inspiration and muscles of active expiration.
What are the major inspiratory muscles?
Diaphragm and external intercostal muscles
What are the accessory muscles of inspiration?
They are the thernocleidomastoid, scalenus, pectoral. It contracts only during forceful inspiration.
What are the muscles of active expiration?
Abdominal muscles and internal intercostal muscles. It contracts only during active expiration.
What device is used to measure long volumes and capacities?
A spinometer.
What does tidal volume (TV mean?
Volume of air entering or leaving lungs during a single breath
Inspiratory reserve volume meaning?
Extra volume of aire that can be maximally inspired over and above the typical resting tidal volume.
Expiratory reserve volume meaning?
Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume.
Residual volume meaning?
Minimum volume of air remaining in the lungs even after a maximal expiration .
Inspiratory capacity meaning?
maximum volume of air that can be inspired at the end of a normal quite expiration.
IC=IRV+TV
Functional residual capacity meaning?
Volume of air in lungs at end of normal passive expiration.
FRC=ERV+RV
Vital capacity meaning?
Maximum volume of air that can be moved out during a single breath following a maximal inspiration.
VC=IRV+TV+ERV
Total Lung Capacity meaning?
Total volume of air the lungs can hold.
TLC=VC+RV
Why can’t residual volume be measured by spirometry?
This is because a spirometry can only detect the volume of air that is taken in and out of the lungs. Since the sesidual volume doesn’t leave the lungs then it can’t be measured.
What else can’t be measured because the residual volume can’t be measured?
The total lung capacity - cause it needs to know the residual volume.
What causes residual volume to increase?
When the elastic recoil of the lungs is lost. E.g emphysema.
What does volume time curve allow you to determine?
- Forced vital capacity
- Forced expiratory volume in one second.
This can then allow you to find the FEV1/FVC ratio.
What is FVC?
The maximum volume that can be forcibly expelled from the lungs following a maximum inspiration.
What is the FEV1/FVC ratio?
This is the proportion of the forced vital capacity that can be expired in the first second.
What is dynamic lung volumes useful in?
The diagnosis of obstructive and restrictive lung disease.
What is the normal FEV1/FVC ratio?
More than 70%
What does it mean if a patient has a FEV1/FVC ratio of lower than 70%?
They have obstructive lung disease.
Obstructive airways needs to have what scores for FVC, FEV1 and FEV1/FVC
Low/normal, low and low
Lung restriction needs to have what scores for FVC, FEV1 and FEV1/FVC
Low, Low, normal?
Obstructive airways with lung restriction needs to have what scores for FVC, FEV1 and FEV1/FVC
low, low, low
What is the air resistance equation?
Flow=total pressure/resistance
What is the resistant in the airflow normally?
Very low so air moves with a small pressure gradient.
What is the primary determinant of airway resistance?
The radius of the conducting airway.
What diseases can cause significant resistance to airflow?
COPD (Chronic Obstructive Pulmonary Disease) or asthma. Expiration in these causes are more difficult than inspiration.
Why does expiration is more difficult than inspiration with who have an obstructive airway?
This is because the intrapleural pressure falls during inspiration but raises during expiration.
This means that
What is the dynamic airway compression?
The rising pleural pressure during active expiration compresses the alveoli (pushes air out) and airways (tends to compress it - not good).
What is the benefit of the dynamic airway compression to normal people?
The increased airway resistance cause an increase in airway pressure upstream. This helps open the airways by increasing the driving pressure between the alveolus and airways.
What is the problem with dynamic airway compression during active expiration in patients with airway obstruction?
The driving pressure between the alveolus and airway is lost over the obstructed segment. This causes a fall in airway pressure along the airway downstream resulting in airway compression.
What are diseased airways likely to do?
Collapse
How can the problem of obstruction become worse?
If the patient also has a decreased elastic recoil of lungs.
What does a peak flow meter do?
gives an estimates of the peak flow rate which assesses the airway function.
What type of diseases is the peak flow meter useful for?
Obstructive lung disease.
What is pulmonary compliance?
It is the measure of effort that 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 what?
Pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant.
What does decreased pulmonary compliance mean?
The greater change in pressure in is needed to produce a given change in volume.
What can a decrease pulmonary compliance cause?
A restrictive pattern of lung volumes in spirometry.
How can compliance be increased?
By the loss of elastic recoil of the lungs.
increased compliance occurs in what?
Emphysema
compliance also increases with…?
Age
