Pulmonary Physiology Flashcards
Parasympathetic NS
- Causes bronchoconstriction
- (Ach & muscarinic receptors)
Sympathetic NS
- causes bronchodilation
- NE, Epinephrine & beta-2 receptors
Anatomical Dead Space
- portion of tidal volue contained in conducting airways
- doesn’t participate in gas exchange
- reflects size of conducting airways
(approx = to body weight [108lbs=108ml)
2 Reasons for Physiological Dead Space
- area ventilated but not perfused
- area perfused but not ventilated
Dead Space Types
- anatomical dead space
- physiological dead space
Physiological dead Space
-the anatomic dead space plus any other areas that don’t exchange gases (that should)=alveolar dead space
=~30% of tidal volume and should be equal to anatomical dead space
Example of Ventilated but not Perfused
- poor circulation, pulmonary embolism
- V/Q=4/0=infinity
Air distribution in lungs
- R lung bigger=more air to it
- dependent alveoli are more compliant and get more air
- air goes where gravity pulls it
Example of perfused but not ventilated
- bronchospasm, obstructions, secretions, (CF, pneumonia, Asthma)
- V/Q=0/5=0
Normal V/Q
4/5=0.8
3-Zone Model
- Zone 1: least gravity dependent; gets little blood
- Zone 2: Intermediate zone (intermittant flow based on pulmonary arterial & alveolar pressures
- Zone 3: most gravity dependent & gets the most blood
Gravity & Blood Flow
- blood flow is gravity dependent
- blood flow ~6x greater at bases of lungs than apices
Right Ventricular Stroke Volume
-increased SV=increased pulmonary artery pressure & cause zone 3 to extend farther upward in each lung
Pulmonary Vascular Resistance
-increased PVR=decreased perfusion
Elastic Recoil
- ability of lungs to return to original shape after having been stretched
- due to elastin
V/Q
- ventilation-perfusion ratio
- relationship between factors affecting alveolar gas flow and capillary blood flow
- not perfectly matched: V/Q=4L/min/5L/min=0.8
Compliance
-the ease with which the lungs expand during inspiration
low compliance=
greater pressure needed to get the same change in volume
Large compliance=
greater increase in volume for small change in pressure
Example that Increases Compliance
-Age & Emphysema
Increased Fluid in Lungs=
decreased compliance
RDS
- in premature infants born before 26-28 weeks old
- before surfactant ready
(Surfactant mature @ 35 weeks)
Surfactant
- produced by type II alveolar cells
- decreases H2O tension
- decrease amount of Mm tension needed to expand lungs
3 Factors Affecting Airway Distribution
- Airway obstruction
- Abnormal Lung or Chest wall Compliance
- Respiratory Mm weakness
Examples that Decrease compliance
- fibrosis
- alveolar edema
- (inspiratory Mm must work harder)
C=
C=change in volume/change in pressure
WOB
-amount of muscular effort needed for ventilation
-=~5% total Vo2
=~10%VC
with pathology=25% VC
5 Factors Affecting WOB
- Airway resistance
- Lung compliance
- Alveolar surface tension
- Dead space volume
- Respiratory Rate
Airway Resistance
- Q(flow of air)=change in pressure/Resistance
- airflow due to pressure gradient and airway resistance
- radius of airway biggest control of airway resistance
Bronchiole Mm Control
- respond to local changes
- increased CO2 in alveolus causes vasodilatoin to increase airflow
Increased WOB=
-decreased tidal volume and RR–>decreased alveolar ventilation
–>less O2 to blood and body
Assessment of Perfusion
- IV injection of technetium labeled human albumin
- will lodge in pulmonary capillaries in proportion to perfusion
- gamma cameras detect
Control mechanisms during disease
- O2 levels decreased and CO2 levels increase or stay same
- peripheral chemoreceptors fire in response to low O2 levels–><60PaO2 mmHg
Cold Spots
areas not ventilated or perfused
Assessment of Ventilation
- pt inhales radioactive xenon
- gamma camera detects location of gas in lungs
Diabetes
-diabetic ketoacidosis–>decreased pH (increased H+) –>firing of peripheral chemoreceptors–>increased ventilation to blow off excess acid
Slow-Wave Sleep
- decreased sensory stimulation
- decreased central control mechanisms
- decreased alveolar ventilation
- PaCO2 2-3mmHg higher than waking
2 kinds of sleep apnea
- central
- obstructive
Eupnea
- normal rate and rhytm
- 12-20breaths/min
Tachypnea
-increased rate with normal rhythm
>20breaths/min
Hyperventilation
- increased rate/depth
- commonly from anxiety due to signals from cortex/limbic system that modify normal breathing
Apnea
-no breathing
Bradypnea
- decreased rate with normal rhythm
- <12 breaths/min
hypoventilation
shallow inspirations, often irregular
Kussmaul’s Respiration
- deeper and faster respirations
- to compensate for metabolic/ketoacidosis (blow off excess acid/CO2)
Glossopharyngeal Breathing
- frog breathing
- used by high SCI injury pt to force air into lungs using tongue and palate
Central Sleep Apnea
- failure of respiratory center
- from encephalitis, brain stem infarction, bulbar polio
- idiopathic: Odine’s curse–>use conscious effort to control ventilation
REM Sleep
- irregular breathing
- decreased Mm activity–>sleep obstructive apnea
-wakes person up with high PaCO2 or low O2 stimulate carotid chemoreceptors
Airway Receptors
- in nose, nasopharynx, larynx and trachea
- respond to increased airway pressure or irritants
- results in sneezing, coughing, bronchospasm or laryngospasm
3 respiratory reflexes
- Hering-Breuer Reflex
- Juxtacapillary (J) Receptors
- Airway receptors
Hering-Breuer Reflex
- protective receptors in smooth Mm of airways from trachea to bronchioles
- when stimulated via vagus nerve to DRG to shut off inspiration
- respond to lung over expansion
- Tidal volume of 1.5 liter before firing
Juxtacapillary Receptors
- within alveolar walls near pulmonary capillaries
- sense increased fluid pressure w/n caps or interstitial space
- signal via vagus nerve to cause rapid shallow breathing
- may be in pts with pulm edema
Cheyne-Stokes Respiration
- gradual increased rate and depth then slower with alternate periods of apnea
- usually due t slow blood flow from heart to brain or change in feed back sensitivity to CSF
- pt with cardiac failure, head injury (sign of impeding death)
Obstructive Sleep Apnea
- results from collapse/closure of pharynx, glottis or larynx
- associated w/ obesity, hypersomnolence, hypoxemia, R heart failure, collapse of throat
- most common: older men
- Pickwickian Syndrome
Biot’s Respiration
- faster and deeper respirations with abrupt pause
- often due to increased ICP
