Lecture 22: Pulmonary ventilation-Exam 3 Flashcards
Inspiratory muscles
Respiratory diaphragm External intercostal muscles Sternomastoids Serratus anterior muscles Scalene muscles
Expiratory muscles
Expiration is passive at rest
Forceful expiration done by :
abdominal muscles
internal intercostals
Difference between volumes and capacitiies
Total lung capacity=sum of all lung capacities
Lung capacity= combination of lung volumes
Lung volumes are not anatomical compartments
Pulmonary volumes
Tidal volume (500 mL): volume of air inspired and expired with each breath at rest
Inspiratory reserve volume (3000 mL): Volume of air that can be inspired in addition to tidal volume with forceful inspiration
Expiratory reserve volume (1100 mL): Additional volume of air that can be expired at end of tidal volume by forceful expiration
Residual volume (1200 mL): volume of air remaining in lungs after forceful expiration
Pulmonary capacities
Inspiratory capacity (3500 mL): Sum of volumes above resting capacity=tidal volume + inspiratory reserve volume Functional residual capacity (2300 mL): Sum of volumes below resting capacity=expiratory reserve volume+residual volume Vital capacity (4600 mL): Sum of all volumes that can be inspired or exhaled=inspiratory capacity + expiratory reserve volume Total lung capacity (5800 mL): Sum of all volumes=vital capacity+residual volume
Minute ventilation
Total volume of gases moved into or out of the lungs per minute
= breaths per minute x tidal volume
Alveolar ventilation
Total volume of gases that enter spaces participating in gas exchange per minute
= breaths per minute X (tidal volume-dead space)
Tidal volume-dead space= respiratory bronchioles + perfused alveoli=.35 L
Dead space
2 types:
Anatomic dead space: trachea, bronchi and bronchioles
Physiological dead space: anatomic dead space +ventilated alveoli with poor or absent perfusion (negligible in healthy individuals)
Physiological dead space= total dead space= 1/3 of tidal volume=0.15L
Calculating dead space
Dead space does not participate in ventilation
Contains negligible CO2
CO2 n perfused alveoli= arterial blood pressure PaCO2
Vd=Vt X (PaCO2-PeCO2)/PaCO2
PeCO2= amount of CO2 in expired air
Pleural pressure
Pressure of the fluid between parietal and visceral pleura
Measured in centimeters of water
During inspiration -5 to -7.5 cm H2O
During expiration -7.5 to -5 cm H2O
Alveolar pressure
Pressure of the air inside alveoli
During inspiration 0 to -1 cm H2O
During expiration 0 to + 1 cm H2O
Transpulmonary pressure
Pressure resulting in the movement of air in and out of the lungs
Difference between alveolar pressure and pleural pressure
Lung compliance
Extent (volume) to which lungs will expand for each unit increase in the Transpulmonary pressure ( normal= 200 mL/ cm H2O)
Inverse of elastance
Surfactant
Produced by type II alveolar cells
Most important component are dipalmitoylphosphatidyl choline, surfactant apoproteins, calcium ions
Surface tension
If air passages leading from the alveoli are blocked, the surface tension in the alveoli collapses the alveoli. This creates positive pressure on the alveoli
Pressure=2 X surface tension / radius of the alveolus
No surfactant causes the surface tension to be about 4.5 times greater
