Applied Physiology: Lecture 7 - Resp Phys 1 Flashcards
(33 cards)
MAJOR FUNCTIONS OF RESPIRATION
Pulmonary Ventilation: Between atmospheric air and alveoli
Diffusion of O2 and Co2 between alveoli and blood
Transport of Co2 and O2 in the blood and body fluids and tissues
Regulation of ventilation
LUNG ANATOMY
Trachea
Right and Left Main Bronchi
Lobar Bronchi
Segmental Bronchi
Terminal Bronchioles
Respiratory Bronchioles
Alveolar Ducts
AIRWAY CONDUCTING ZONES
Have NO alveoli
What do you think they are? (tracheal, bronchi, etc.)
This is Dead space
RESPIRATORY ZONE
The Acinus
What is this comprised of?
Makes up most of the volume of the lung
Area distal to the terminal bronchioles: Respiratory bronchioles and alveolar ducts.
2.5-3 liters volume at rest
Lung Anatomy Flow Diagram
1st 16 generations are all Dead Space (33%, ~150 mLs)
After that is the Acinus
GENERAL VASCULATURE
Pulmonary artery to capillaries to vein
Bronchial circulation (conducting airways): Bronchial circulation comes off thoracic aorta. High resistance low flow.
Capillary diameter is 7 to 10 microns, thickness 0.3 microns
Each RBC spends about 0.75 seconds in the capillary network
Low resistance circuit, high flow
Normal Pa pressure 15 mmHg???
PULMONARY MECHANICS
2 ways lungs are expanded and contracted:
Diaphragm moves up and down to lengthen and shorten chest cavity
Elevation and depression of the ribs to increase and decrease diameter anterior and posterior.
Muscles of inspiration: external intercostals, sternocleidomastoid, anterior serrati, scaleni
Pull rib cage up
Muscles of expiration: abdominal recti, internal intercostals.
Move the rib cage down
You inhale
Your diaphragm drops, the chest wall expands outward
Air flows down to the terminal bronchioles like water through a hose
After the terminal bronchioles there is so much surface area that it flows by diffusion
PRESSURE CHANGES INVOLVED IN AIR MOVEMENT
The lung floats in the chest cavity.
Suspended by pleural fluid
Fluid between the lung tissue and the pleural tissue (pleural cavity)
Pleural fluid lubricates the and facilitates movement of the lungs
Pleural fluid ”continuously sucked” by lymphatic drainage. So lungs are held in that cavity but also can move freely as well.
PRESSURE CHANGES INVOLVED IN AIR MOVEMENT (Part 2)
Pleural Pressure: Pressure of fluid between lung pleura and chest wall pleura.
-5 cmH2O at rest (remember: slight suction from lymphatic system)
-7.5 cmH2O during inspiration
Events reversed in expiration
Alveolar Pressure: Pressure of the air inside the alveolus. When airway open and no flow: 0 cmH2O
Measured by esophageal pressure measurement??? (used with critically ill thoracic surgeries)
During inspiration pressure in alveoli must fall below 0cmH2O (-1cmH2O) for air to travel 500ml in 2 seconds
During expiration pressure changes to +1cmH2O
Transpulmonary Pressure: Difference between alveolar pressure and pleural pressure. Really a measurement of the elastic recoil of the lung (Normal between 10-15)
Pressure Change 2nd Pic
LUNG COMPLIANCE
By definition, the amount the lungs will expand for each unit of increase in transpulmonary pressure.
Compliance= Volume/Peak Pressure
Normal Compliance: 200 ml air per 1cm TPP increase
Compliance is determined by elastance of lung tissue and surface tension of alveoli. Also compliance of system involves chest wall compliance.
Elastic forces of lung tissue determined mainly from elastin and collagen fibers. Alveoli forces moderated by surfactant.
ROC increases compliance by effecting skeletal muscle
SURFACTANT
Water molecules want to to touch each other
Surfactant decreases surface tension of water
Surfactant is made by TYPE II alveolar epithelial cells
Surfactant is a made of phospholipids, proteins and ions
Increases alveolar and total lung compliance
WORK OF BREATHING
1: Compliance or elastic work of breathing: work required to expand the lungs against lung and chest elastic forces
2: Tissue resistance work: work required to overcome viscosity of lung and chest wall
3: Airway resistance work: work required to overcome resistance of airway movement in and out of lungs
SPIROMETRY
SPIROMETRY Values
Based on 70 kg patient
LUNG VOLUMES
- The tidal volumeis the volume of air inspired or expired with each normal breath; it amounts to about 500 milliliters in the adult male.
- The inspiratory reserve volume is the extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; it is usually equal to about 3000milliliters.
- The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; this normally amounts to about 1100 milliliters.
- The residual volume is the volumeof air remaining in the lungs after the most forceful expiration; this volume averages about 1200milliliters.
LUNG CAPACITIES
- The inspiratory capacity equals the tidal volume plus the inspiratory reserve volume. This is the amount of air (about 3500milliliters) a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount.
- The functional residual capacity equals the expiratory reserve volume plus the residual volume. This is the amount of air that remains in the lungs at the end of normal expiration (about 2300milliliters). This is the measurement of how fast a sedated patient will desaturate (KNOW THIS CALCULATION???)
- The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume. This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent (about 4600milliliters).
- The total lung capacity is the maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800milliliters); it is equal to the vital capacity plus the residual volume.
CAPACITIES= 2 OR MORE VOLUMES
FRC
The lung volume at the end of normal exhalation
The inward elastic recoil of the lung approximates the outward elastic recoil of the chest
Equals Expiratory reserve volume + residual volume
Obesity markedly reduces, due to decrease in chest wall compliance
Females 10% decrease, Pregnancy decreases
Posture: supine or prone decreases
Restrictive lung disease decreases
Phrenic Nerve paralysis decreases
General Anesthesia, intraabdominal surgery, paralysis all decrease… especially if expanding the abdominal space with CO2 (insufflation)
Functional residual capacity (FRC) and residual volume provide a buffer in the alveoli such that abrupt alterations in PaO2and PaCO2 do not occur.
In the presence of a decreased FRC, transient interruptions in breathing, as during direct laryngoscopy, may result in rapid changes in PaO2.
CLOSING CAPACITY
Small airways lacking cartilaginous support, depend on radial traction caused by elastic recoil of surrounding tissue to keep them open
Airway patency, especially basal areas, highly dependent upon lung volume
Volume at which alveoli begin to close in dependent areas is called closing capacity
These alveoli continue to be perfused, but not ventilated (collapsed alveoli)
V/Q mismatch (shunt)
Result=intrapulmonary shunt (venous admixture), promotes hypoxemia
Closing capacity (CC) is the lung volume at which the small airways in the dependent parts of the lung begin to close.
Closing capacity is the sum of closing volume and residual volume.
It denotes the lung volume from the beginning of airway closure to the end of maximal expiration. Therefore, CV=CC-RV
In normal young people, the closing volume is approximately 10% of the vital capacity, or 400 to 500 ml.
The closing volume and the closing capacity increase with age.
The closing volume is increased in patients with small-airway disease and in chronic smokers.
FRC AND CLOSING CAPACITY
FRC is either independent of age in adults or increases very slightly with increasing age.
Closing Capacity (CC), however, increases with age. Normally, CC is well below FRC. Age 44, CC=FRC in supine position. By age 66, CC exceeds FRC in upright position.
-Hypoxemia in supine position for old patients!
FRC increases approximately 30% by changing from the supine position to the upright position.
The CC, on the other hand, is independent of body position.
It is important to remember that the effects of age on CC and posture on FRC determine whether airway closure exists.
-Especially in obese patients
ALVEOLAR VENTILATION
Areas include: alveoli, alveolar sacs, alveolar ducts, respiratory bronchioles.
The rate new air reaches these areas is called alveolar ventilation.
Dead space: air that does not reach alveolar ventilation. Everything above the acinus.
The dead space stops/begins at the Y-Connector
Normal dead space: 150ml (increases with age) anatomic dead space
Physiologic dead space = alveolar dead space (areas that arent perfused in the lungs) + anatomic dead space (first 16 generations)
(WHAT IS A PE with DEAD SPACE????)
In a normal healthy adult physiologic dead space = anatomic dead space
(KNOW SHUNT FRACTION???)
ABBREVIATIONS
AIRWAY RESISTANCE
Resistance highest in the bronchioles and bronchi closest to the trachea.
Lowest below terminal bronchioles and acinus.
Due to the large surface area of the non conducting airways.
In disease states small bronchioles play a larger role in resistance of air due to their small diameter and how easily occluded they are. Edema, infection, contraction (spasm), mucus.
