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ANE 590 Module 2 Respiratory Physiology
Terms in this set (291)
Which cartilages of the Larynx are unpaired?
Which cartilages of the Larynx are paired?
4 and 5. Arytenoids
6 and 7. Corniculates
8. and 9. Cuneiforms
What intrinsic muscles of the Larynx act on the Laryngeal inlet?
-Closed by the aryepiglottic muscle. -Opened by the thyroepiglottic muscle.
What intrinsic muscles of the Larynx act on the Glottic slit?
-Open the posterior cricoarytenoid muscles.
-Closed by the interarytenoid muscle and the lateral cricoarytenoid muscles.
What intrinsic muscles of the Larynx act on the True Vocal Cords?
-Lengthened by the cricothyroid muscles
-shortened by thyroarytenoid muscles.
NERVE SUPPLY TO THE LARYNX
The superior and inferior laryngeal nerves are branches of which cranial nerve?
Cranial nerve X
What are the 2 branches of the superior laryngeal nerve?
arise from the ganglion of the vagus nerve and divides into:
The external and the internal.
What muscles does the external segment of the superior laryngeal nerve branch to?
The inferior constrictor muscle of the pharynx & the cricothyroid muscle.
It lengthens or increases tension of vocal cords.
Damage to the external segment of the superior laryngeal nerve results in what?
Damage to the internal segment of the superior laryngeal nerve results in what?
What part of the larynx does the internal segment of the superior laryngeal nerve provide sensation to?
From the laryngeal side of the epiglottis down to the true vocal cords.
Where does the inferior/recurrent laryngeal nerves arise from?
Vagus nerve at 2 different levels (left and right).
Where is the left recurrent laryngeal nerve located?
Descends with the vagus and loops around the arch of the aorta to the neck.
Where is the right recurrent laryngeal nerve located?
Travels with the vagus to the subclavian artery, loops around the subclavian up to the neck.
What can damage to the recurrent laryngeal nerve lead to?
Unilateral or bilateral vocal cord paralysis with hoarseness or dyspnea.
What supplies blood to the larynx?
-superior thyroid artery (branch of the external carotid artery) and also the inferior thyroid artery (branch of the thyrocervical trunk)
what kind of tissue is the trachea lined with?
pseudo stratified ciliated columnar epithelium
where does the trachea extend from?
inferior larynx to the carina
On average, what is the distance from incisors to the carina?
26 cm (10.4 inches)
What is the diameter of the trachea?
What artery supplies blood to the trachea?
Inferior thyroid artery
what kind of tissue is the bronchi?
At what angle does the right bronchus take off from the trachea?
25 degrees. It is wider and shorter than the left.
how many lobar bronchi does the right bronchus divide into?
3 lobar bronchi
mainstem bronchus ends at how many cm from the carina?
2-2.5cm from the carina and gives rise to the RUL bronchus
after the RUL, the right main bronchus continues as what?
3 cm as the bronchus intermedius then divides into the middle and lower lobes
At what angle does the left bronchus take off from the trachea?
how many cm long is the left mainstem?
how many lobar bronchi does the left main divide into?
2 lobar bronchi
-left upper lobe bronchus: divides into upper half and lower half (lingular branch)
-left lower lobe bronchus
LUNG LOBES AND SEGMENTS
each generation is referred to as a ?
-mainstem is the first generation
what is third generation called?
How many generations occur before the alveoli?
What are the last structures perfused by the bronchial circulation and are at the end of the conducting airways?
What bronchioles are perfused by pulmonary circulation?
T/F, Gas exchange occurs in the terminal bronchioles?
What part of the airway is the first site where gas exchange occurs?
in adults, how many generations of respiratory bornchioles are there?
respiratory bronchioles lead into what?
4-5 generations of alveolar ducts which turn into alveolar sacs that then open into alveolar clusters
what are the pores of kohn?
-holes in the alveolar walls
-function as collateral ventilation= ventilation occurs when lung is partially deflated = even distribution
-equalize pressure in adjacent alveoli
-prevent lung collapse
RESPIRATORY AIRWAYS AND ALVEOLAR CAPILLARY MEMBRANE
What are the 2 primary functions of the pulmonary system?
(1) Transport of respiratory gases
(2) Production of a wide variety of local and humoral substances.
What is the conducting zone?
rom the nose to the terminal bronchioles
-conduct gas without exchanging gas with the blood.
it is impertive to exceed deadspace to ensure gas exchange?
deadspace is how many mL/kg?
What is the anatomic dead space of a male patient 6 feet tall and weighing 130 kg?
IDW = 50kg + 2.3kg
(height[in.] - 60); IDW=77.6; Anatomic dead space = 2ml/IDW kg 77.6kg
2 = 155.2 ml
does gas exchange occur in the respiratory zone?
What structures comprise the respiratory zone?
what are the denset capillary networks in the body?
pulmonary capillary beds
Which type of alveolar cell covers 80% of the alveolar surface?
Type I (flat, squamous cell)
Which type of alveolar cell manufactures surfactant?
Type II (polygonal cells)
Which type of alveolar cell are alveolar macrophages?
pulmonary vascular system
What are the 2 major circulatory systems supply blood to the lungs?
Pulmonary vascular networks and bronchial vascular networks.
pulmonary vascular system delivers mixed venous blood from the RV to to the pulmonary capillary bed via two pulmonary arteries?
How many pulmonary arteries are there?
2 pulmonary arteries
How many pulmonary veins are there?
4 pulmonary veins
pulmonary veins run independtly along the intra lobar connective tissue planes?
what provides O2 to the alveoalr parenchyma?
pulm. capillary system
what does the bronchial vascular system provide oxygen to?
conductive airways and pulmonary vessels
What is considered a "normal" shunt between the anatomic connections of the bronchial and pulmonary venous circulation?
2%-5% of the total cardiac output
What are the subdivisions of the mediastinum?
Superior, Anterior, Posterior, and Middle
describe the superior division of the mediastinum?
-above the sternal angle from superior to thoracic inlet
-contain the thymus, esophagus, trachea, and great vessels
describe the middle division of the mediastinum?
-between ant and post divisions.
-bound lateral by the parietal pleura
-contain the heart, distal trachea, mainstem bronchi, and great vessels
describe the posterior division of the mediastinum?
-between the vertebral colum and posterior pericardium
-contain the esophagus, thoracic, aorta, and thoracic duct
describe the anterior division of the mediastinum?
-between the sternum and pericardium
-contains the thymus
what does the parietal pleura attach to?
what the visceral pleura cover?
What is the medical name for air in pleural space?
lung collapse and thorax springs out
what is a tension pneumo?
inspired air that accumulates in the pleural space and is not expelled
-air under pressure
elastic recoil of the lungs tends to favor?
lung collapse once the negative pressure of the pleural space is disrupted
What is the medical name for blood in pleural space?
What is the medical name for serous fluid in pleural space?
What is the medical name for pus in pleural space?
Empyema or pyothorax
What is the medical name for organized blood clot in pleural space?
What is the medical name for lymph in pleural space?
What muscles contract during normal breathing? (eupnea)
Diaphragm and external intercostals
How does contraction of inspiratory muscles affect intrathoracic pressure and volume of thoracic cavity?
Causes ↓ intrathoracic pressure → the volume of thoracic cavity to ↑
what law describes ventilation?
increase volume created a decrease in pressure
What nerve innervates the diaphragm?
Each half of the diaphragm is innervated by a branch of the phrenic nerve arising from C 3, 4 and 5 ("keeps me alive!")
eupneic expiration results from what?
passive recoil of chest wall
when do internal intercostal muscle become activated?
when do abd muscle become activated?
forced exhalation (coughing)
when do sternocleidomastoid and scalene muscle contract?
-with the diaphragm and intercostal muscles for forceful exhalation (can be used for forceful inhalation)
MECHANICS OF VENTILATION: ELASTIC RESISTANCE
T/F, Intrapleural pressure is positive?
False; it is negative
chest expands outward
lungs tend to collapse
why do the lungs tend to remain in an inflated state?
-outward force of the thoracic cage exceeds the inward force of the lung
What is functional residual capacity?
gas volume in the lungs when the outward and inward forces on the lung are equal.
It is the volume of air remaining in the lung at the end of a normal expiration.
gravity creates a more subatm pressure in the dependent or non dependent areas of the lung?
where do surface tension forces occur at?
air fluid interface
-reduces area of the interface
-favors alveolar collpase
gas fluid interface lining the alveoli behave like a bubble, what must happen for this bubble to remain inflated?
-gas pressure within the bubble, which is contained by surface tension must be increased by surrounding gas pressure
Surface tension of the liquid in the lung ____ during inspiration and _____ during expiration?
what happens to alveolar radius during exhalation?
why dont the alveoli collapse during exhalation?
t= surface tension
r=radius of bubble
alveolar collapse is:
1. directly proportional to?
2. indirect. proportional to ?
1. surface tension
2. alveolar size
what happens to pressure within the alveoli when the radius decreases?
-creates gas flow from larger to smaller alveoli
-maintains structural stability and prevents lung collapse
What are the physiological advantages of surfactant?
(1) A low surface tension in the alveoli increases the compliance of the lung and reduces the work of expanding it with each breath (2) Stability of the alveoli is promoted.
function of pulmonary surfactant?
-decreases surface tension
-directly proportional to its concentration in the alveolus
a smaller alveoli would have more or less concentration of surfactant?
-more surfactant= reduces surface tension more
an overdistended alveoli would have more or less concentration of surfactant?
-les surfactant= surface tension increases
What is the definition of elastic work?
-work required to overcome the elastic recoil of the pulmonary system.
-This occurs during inspiration as expiration is passive during normal breathing.
What is the definition of resistive work?
Work to overcome resistance to gas flow in the airway and includes equipment-imposed resistance such as the ETT.
What is the definition of compliance (Cl)?
The change in volume divided by the change in pressure.
What is static compliance?
The pressure-volume relationship for a lung when the air is not moving.
How does emphysema change static compliance?
How does restrictive pulmonary disease affect compliance?
compliance is dependent on what?
on the compliance curve/ sigmoid curve , what does the vertical line at the end of expiration represent?
on the compliance curve/ sigmoid curve, where do we normally breathe?
steepest part of the curve
in restrictive pulmonary disease, what happens to the compliance curve/ sigmoid curve?
-shifts to the right
decreased compliance =
-Larger changes in intrapleural pressure needed to create the same TV
-Expend more elastic work to get the same volume into the lungs
-Tend to breathe more rapid and shallow
-CPAP will increase TV and slow RR
T/F, patients with restrictive pulmonary disease tend to breath more rapid and shallow?
What are some conditions that reduce compliance?
alveolar edema (prevents inflation of some alveoli)
unventilated lung for a long period;
increased pulmonary venous pressure
What are some conditions that increased compliance?
normal aging lung.
What does chest wall compliance equal?
CW = ΔChest volume/ΔTransthoracic pressure
What does total compliance of lung and chest wall together equal?
what happens to chest wall compliance in the supine position?
-decreases DT weight of abd contents on diaphragm
How does increased gas flow affect resistance?
Increases in proportion to gas flow
laminar flow occurs where?
distal to small bronchioles
where is turbulent flow noted?
How does gas density affect resistance?
They are directly proportional
How does radius of respiratory tract affect resistance?
They are inversely proportional. If radius is halved, resistance ↑ 16-fold
How does length of respiratory tract affect resistance?
Directly proportional. Doubling the length doubles the resistance.
What is laminar flow?
Low flow rates move through a straight tube result in a series of concentric cylinders of gas flowing at different velocities. They are parallel to sides of tube and have a velocity of zero at the cylinder wall. The maximum velocity at the center of the advancing "cone." Viscosity is relevant under laminar flow.
What is turbulent flow?
Occurs when resistance to gas flow is significant. Random movement of gas movement of gas molecules down air passages. It is very loud and audible.
What are 4 conditions that will change laminar flow to turbulent flow?
(1) High gas flows
(2) Sharp angles within the tube
(3) Branching in the tube
(4) Decrease in the tube's diameter.
How is airway resistance related to lung volume?
VOLUME RELATED AIRWAY COLLPASE
low lung volumes and loss of radial traction does what?
increases contribution of small airways to total resistance
-airway resistance becomes inverse to lung volume
-increasing lung volume with PEEP can reduce airway resistance
FLOW RELATED AIRWAY COLLAPSE
what does forced exhalation cause?
-reversal of normal transmural pressure
-dynamic airway compression= limits airflow during a forced expiration
*results in a large pressure drop across intrathoracic airways
What is the definition of Equal Pressure Point?
The point along the airways where dynamic compression occurs.
what does pursed lip breathing or premature termination of exhalation cause?
-helps prevent reversal of transmural pressure gradients and trapping of air
what is anatomic dead space?
-gases in non respiratory airways
what is alveolar dead space?
alveoli that are not perfused
What is physiologic dead space?
The sum of anatomic and alveolar dead space.
It refers to areas of the lung that are ventilated but poorly perfused.
what is the normal dead space in ml/kg?
2 ml/ kg or 1 mL/lb
-nearly all anatomic
Which lung receives more alveolar ventilation?
Right > Left
What part of the lung is better ventilated, upper or lower lung areas?
Lower lung areas. (dependent)
-alveoli in upper lungs are max inflated and non compliant
-smaller alveoli in dependent areas are more compliant and undergo greater expansion
what is the normal CO?
how many mL of CO undergo pulm cap gas exchange?
going from the supine to the erect position decreases pulmonary blood volume by how much %?
How does Trendelenburg affect pulmonary blood volume?
What is the most powerful stimulus of pulmonary vasoconstriction?
Pulmonary arterial and alveolar hypoxia reduces pulmonary blood flow from non-dependent areas to dependent areas and prevents hypoxemia.
HYPOXIC PULMONARY VASOCONSTRICTION
HPV and bronchoconstriction allow the lungs?
-maintain v/q matching
-stimulated by alveolar hypoxia
-severe decrease blood flow
-decreases regional pulmonary blood flow= bronchoconstriction and diminished degree of dead space ventilation
HPV and bronchoconstriction protect the lungs, particular in one lung ventilation?
when a shunt or dead space occurs, what happens to the lung?
-becomes a silent unit in which little V and Q occur
What is hypoxic pulmonary vasoconstriction (HPV)?
Contraction of smooth muscle in the walls of the small arterioles in the hypoxic region. The PO2 of the alveolar gas, not the pulmonary arterial blood, chiefly determines the response.
What are some factors that reduce the effectiveness of HPV?
Excessive tidal volume or PEEP
Hypocapnia, Acidosis, Hypothermia
Volatile agents > 1.5 MAC
Calcium channel blockers (may),
Why is the distribution of pulmonary perfusion not uniform?
-dependent portions receive greater flow than the upper portions.
-Gravity exerts a significant influence on blood flow.
What are the relationship between the pressure in the alveoli (PA), in the arteries (Pa), in the veins (Pv) and the pulmonary interstitial pressure (Pi) in the different zones of West?
Zone 1: PA > Pa > Pv
Zone 2: Pa > PA > Pv
Zone 3: Pa > Pv > PA
Zone 4: Pa > Pi > Pv > PA
describe zone 1?
-alveolar dead space
-alveolar pressure occludes the pulmonary capillaries
describe zone 2?
-pulmonary capillary flow is intermittent
-varies during respiration
-according to arterial-alveolar pressure gradient
describe zone 3?
-pulmonary capillary flow is continuous
-proportional to the arterial-venous pressure gradient
V/Q PERFUSION RATIOS
What is the overall V/Q ratio?
(V) Alveolar ventilation ~ 4L/min
(Q) Pulmonary capillary perfusion ~5 L/min
no ventilation causes what?
no perfusion causes what?
alveolar dead space
throughout the lungs, V/Q can range from?
pulmonary venous blood from areas with low V/Q ratios has?
-low tension and high CO2 tension
-tends to depress arterial O2 tension more prfound than CO2 tension
compensatory increase in O2 uptake cannot take place where V/Q is normal?
-pulmonary end capillary blood is max sat. with O2
What is a shunt?
Mixed venous blood from the right heart returns to the left heart without being re-saturated with O2 in the lungs.
Overall effect dilutes arterial O2 content.
What are absolute shunts?
-Lung units where V/Q is "0"
-Cannot partially correct with increased FiO2
What are relative shunts?
Low but finite V/Q ratio
Can partially correct with increased FiO2
What are the effects of anesthesia on Gas exchange?
-Increased dead space
-Increased intrapulmonary shunting.
-Increased scatter of V/Q ratios.
-Atelectasis and airway collapse increases venous admixture (physiologic shunt) 5% to 10%
Inhlation agents can inhibit hypoxic pulmonary vasoconstriction at what MAC?
What are the effects of prolonged high FiO2?
It increases the absolute shunt and can result in "absorption atelectasis," a complete collapse of alveoli with previously low V/Q once all O2 within the alveoli is absorbed.
CENTRAL RESPIRATORY CENTERS
Where does the basic breathing rhythm originate?
What group of cells are primarily active during inspiration?
Dorsal Respiratory Group
What group of cells are primarily active during expiration?
Ventral Respiratory Group
Where is the pneumotaxic center located?
The upper pons (upper pontine)
Where is the apeustic center located?
The lower pons (lower pontine)
Where are the central chemoreceptors located?
Ventral surface of the medulla
What does the central chemoreceptors sense?
-changes in CSF H+.
-Elevated PaCO2 elevates CSF H+ and activates the chemoreceptors.
what does secondary stimulation of the adjacent respiratory medulla do?
increase alveolar ventilation
what does a very high PaCO2 depress?
the vent response = CO2 narcosis
What is the apneic threshold?
PaCO2 at which ventilation is zero.
Awake state: cortical influences prevent apnea.
what depresses central chemoreceptor activity?
Where are peripheral chemoreceptors located?
-Carotid bodies at the bifurcation of the common carotid arteries
-aortic bodies surrounding aortic arch
Which peripheral chemoreceptors are the most important?
The carotid bodies.
What does the peripheral chemoreceptors sense?
-Decreases in arterial PO2/ perfusion
-increases in arterial PCO2.
what is the most important factor that influences the carotid chemoreceptors?
-receptor activity does no increase until PaO2 <50
the carotid bodies interact with the central respiratory center via what nerve?
At what PO2 does the maximum peripheral chemoreceptor response occur?
PO2 < 50 mm Hg
What nerve connects the peripheral chemoreceptors and the central respiratory centers?
Glossopharyngeal nerves (afferent pathway)
What nerve carries the impulse from pulmonary stretch receptors?
The impulses travel in the vagus nerve via large myelinated fibers.
stretch receptors are located in what areas of the lungs?
-smooth muscle of airway
What is the Hering-Breuer inflation reflex?
-Slowing of respiratory frequency due to an increase in expiratory time.
-Inhibit inspiration when lung is inflated to excessive volumes.
What is the deflation reflex?
-shortening of exhalation when lung is delfated
-plays minor role
Where are irritant receptors located?
What do irritant receptors react with?
Noxious gases, smoke, dust, and cold gases.
Reflex increase in RR, bronchoconstriction, coughing.
Where are J (Juxtacapillary) receptors located and what are their response?
-located in interstitial space within alveolar walls
-Induce dyspnea in response to expansion of interstitial space volume and various chemical mediators following tissue damage.
what are muscle and joint receptors?
-located in pulm. muscles and chest wall
-important for exervise
-pathological condition assocaited with decreased compliance
EFFECTS OF ANESTHESIA
how does GA affect ventilation?
-promotes hypoventilation via:
1. central depression of chemoreceptor
2. depression of external intercostal muscle activity
increased anesthetic depth causes what?
1. apneic threshold increases
2. slope of MV curve decreases
*partially reversed by surgical stimulation
-peripheral response to hypoxemia is more sensitive than the central CO2 response with GA?
-peripheral response is abolished by even sub anesthetic doses
How much does anesthesia decrease FRC?
Additional 15 to 20% beyond which occurs in the supine position alone.
dorsal (dependent) part of the diaphragm moves where when lying in the supine position?
-rib cage moves inward due to loss of muscle tone from GA?
bronchodilating properties of IA tends to overcome increased resistance due to decreased FRC?
How is O2 carried in the blood?
In 2 forms, dissolved and combined with Hgb.
The amount of dissolved oxygen is proportional to the partial pressure. What law does this obey?
For each mmHg of PO2, how much ml O2/100mL of blood are there?
0.003 mL O2/100 mL blood
arterial PO2 of 100mmhg?
0.3 mL O2/100 mL blood
What is the structure of heme?
-Iron-porphyrin compound that is joined to protein globin
-4 polypeptide chains
-there are 2 types of chains, alpha and beta.
Normal adult Hgb is what form?
Normal fetal Hgb is what form?
F, it is gradually replaced over the first year of postnatal life.
What Hgb form has valine instead of glutamic acid in the beta chain?
Hgb S (sickle)
-has reduced O2 affinity= shifts O2 curve to the right
Hgb S cause what type of shift in the dissociation curve?
What are the properties of Hgb S?
Reduced O2 affinity. The deoxygenated form is poorly soluble and crystalizes within the red cell. The cell shape changes from biconcave to crescent or sickle shaped with increased fragility and a tendency to thrombus formation.
what does the oxyHGB dissociation curve describe?
-non linear tendency for O2 to bind to HGB
-at an SaO2 of 90% or less, small differences in HGB saturation reflect large changes in PaO2
at PaO2 >60 mmhg, the standard dissociation curve is flat, why?
-O2 content of the blood does not change significantly even with large increases in O2 partial pressure
when SaO2 is 90% what is PaO2?
60 mmHg= curve becomes steep!
What is termed when all the available binding sites are occupied by O2?
What is the oxyhemoglobin dissociation curve?
It describes the non-linear tendency for oxygen to bind to Hgb.
What causes an oxygen dissociation curve shift to the right?
↑ in Temp, PCO2, H+, and 2,3-DPG. Sickle cell
*anything that increases metabolism
What causes an oxygen dissociation curve shift to the left?
↓ in Temp, H+, PCO2, 2,3-DPG. Hgb F. Carboxyhemoglobin. Methemoglobin.
*anything the decreases metabolism
What is 2,3-DPG?
End-product of RBC metabolism.
What is normal P50?
-PaO2 at which HGB is 50% saturated
26-27 mm Hg at 37C at a pH of 7.4
Greater than 27 mmHg is referred to as a shift to the right.
Less than 26 mmHg is referred to as a shift to the left.
as P50 decreases, O2 affinity increases
How much more soluble is CO2 compared to O2?
What are the 3 forms CO2 is carried in the blood?
Dissolved CO2 (~10%)
carbamino compounds (~30%).
What is the most important carbamino compound?
What is the Haldane effect?
Deoxygenation of the blood increases its ability to carry CO2.
T/F, Oxygenated Hb is more acidic than reduced Hb?
Why is reduced HGB less acidic than O2 form?
HGB is a proton acceptor
reduced HGB (deoxyHGB) help with the loading or unloading of CO2?
loading of CO2
oxygenation in the pulmonary capillary (oxyHGB) helps with the loading or unloading of CO2?
unloading of CO2
What is the avg O2 consumption?
250mL/min with a CO of 5L/min
What is the most important source of oxygen?
O2 contained in the lungs at FRC
What is FRC times FiO2?
0.21 x 2300 ml = ~ 480 ml of O2 in the lungs
Hypoxemia in ~ 90 seconds
-Increase FIO2 prior to apnea
FIO2 1.0 x 2300 ml = 2300 ml of O2
Delays hypoxemia for 4 - 5 minutes
What are the physiologic changes in respiratory function associated with aging?
(1) Dilation of alveoli
(2) Enlargement of the airspaces
(3) Decrease in exchange surface area
(4) Loss of supporting tissue
(5) Decreased lung recoil leads to an increase in residual volume and FRC.
What is intrapleural pressure?
-between the parietal pleura of chest wall and visceral pluera covering lung
-Usually slightly subambient (-2 to -3 mmHg) because lungs recoil inward and chest wall recoils outward.
when are inward and outward forces equal?
What is intrapulmonary pressure?
-Zero at end-expiration
-negative at start of inspiration (air enters lungs because intrapulmonary pressure is less than atmospheric pressure)
what is TV?
amt of gas inspired or expired with each breath
What is inspiratory reserve volume?
Max amt of additional air that can be inspired from the end of a normal inspiration
What is expiratory reserve volume?
Maximum volume of additional air that can be expired from the end of a normal expiration.
What is closing volume?
Denotes the lung volume from the beginning of airway closure to the end of maximum expiration, the residual volume.
What is residual volume?
The volume of air remaining in the lung after a maximal expiration.
This is the only lung volume which cannot be measured with a spirometer.
what are lung capacities?
-subdivision of total volume that include two or more of the 4 basic lung volumes
-2 or more volumes represent a capacity
What is total lung capacity?
The volume of air contained in the lungs at the end of a maximal inspiration.
What is vital capacity?
The maximum volume of air that can be forcefully expelled from the lungs following a maximal inspiration.
What is the formula for FRC?
What is inspiratory capacity?
Maximum volume of air that can be inspired from end expiratory position.
What is closing capacity?
-Lung volume at which the small airways in dependent parts of the lung begin to close.
-It is the sum of closing volume and residual volume.
-It is unaffected by posture.
it is normally below FRC
what is FRC?
-volume of air in lung at end of a normal expiration
-FRC= RV+ ERV
-affected by posture
What happens when closing capacity exceeds FRC?
Airway closure even during normal tidal breathing.
-airway closure during normal TV breathing= V/Q mismatch and drop in PaO2
when does CC exceed FRC?
-person with normal lungs beyond age 45 when supine and beyond 65 when standing
PULMONARY FUNCTION TESTS
What is FEV1?
the volume of air that is forcefully exhaled in one second.
What is FVC?
the volume of air that can be maximally forcefully exhaled.
What is FEV1/FVC?
Ratio of FEV1 to FVC,
expressed as a %.
normal: 0.8 or 80%
What is FEF25-75?
the average forced expiratory flow during the mid (25-75%) portion of the FVC.
What is PEF?
Peak expiratory flow rate-
the peak flow rate during expiration
What are the changes in pulmonary function tests in restrictive diseases?
It is a proportional decrease in all lung volumes.
FVC and FEV1, FRC, TLC
what kind of ventilation is tolerated in patients with restrictive disease?
small Tv with high RR
What are the changes in pulmonary function tests in obstructive diseases?
Small airway obstruction to expiratory flow.
Normal to low:
normal to high:
FRC and TLC
what kind of ventilation is tolerated in patients with obstructive diseases?
-high volumes and lower RR= allows time for exhalation
-be cautious of barotrauma
When should patient who smoke stop prior to an elective procedure?
At least 2 months
What is the most important determination of the risk of PPC?
The operative site
*highest risk in non lap upper abd sx
followed by lower abd and intrathoracic operations
What is the single most important consideration to prevent PPC?
extrathoracic airway obstruction causes problems with inspiration or expiration?
intrathoracic airway obstruction causes probelms with inspiration or expiration?
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