Flashcards in Control of ventilation & Pulmonary mechanics Deck (102):
The central chemoreceptors are stimulated by _______ H+; an increase in cerebral spinal fluid CO2 automatically leads to an ______ in H+.
______ drives normal respiration.
The peripheral chemoreceptors are stimulated by ______ PCO2, ______ pH, and/or _____ PaO2 (<60mmHg).
increased; decreased; decreased
The _______ nerve carries sensory impulses from the carotid bodies, and the _____ nerve carries sensory impulses from the aortic bodies and also from stretch receptors in the lung parenchyma.
glossopharyngeal nerve--> carotid bodies
vagus nerve---> aortic bodies and lung parenchyma
The glossopharyngeal nerve carries sensory impulses from the _______, and the vagus nerve carries sensory impulses from the _______ and also from stretch receptors in the _______.
The glossopharyngeal nerve carries sensory impulses from the carotid bodies, and the vagus nerve carries sensory impulses from the aortic bodies and also from stretch receptors in the lung parenchyma.
The diaphragm is the muscle of inspiration. ______ % of TV alone is all due to the diaphragm. The rest is from the _________ nerve.
50-75%; external intercostal
_______ are our built in ABG's.
-only kick in when PaO2 <60
Why is it BAD to give chronic O2 patients too much O2?
because they rely on their chemoreceptors--> their chemoreceptors kick in when PaO2 <60... we knock out this function when giving them O2
DRG stands for:
doral respiratory group
VRG stands for:
ventral respiratory group
DRG generates the basic rhythm of respiration, it is found in the medulla, and may be considered the ________.
The VRG can influence BOTH _______ and ________.
inspiration and expiration (internal intercostals)
*probably comes into play when high levels of ventilation are required
The pneumotaxic center is located _________. The apneustic center is located ________.
pneumo: high in the pons
apneu: low in the pons
The ________ SHUTS OFF inspiration.
*apneustic center also has similar function
The ______ work together to control the RATE and DEPTH of inspiration.
pneumotaxic and apneustic centers
The smooth muscle of the bronchi and bronchioles has receptors that FIRE when STRETCHED, which reflexly tends to INHIBIT inspiration. This is called the _______.
In adults, the Hering-Breuer reflex does not become important until TV exceeds ____.
In neonates the Hering-Breuer reflex is _______ and ______.
STRONG and RELEVANT
*protective mechanism for preventing excess lung inflation
In the Hering-Breuer reflex, the ______ nerve carries afferent (sensory) information.
Central chemoreceptors respond to _________.
*H+ concentration in CSF increases as PaCO2 increases and decreases as PaCO2 decreases--> normally CO2 drives ventilation
Peripheral chemoreceptors respond to 3 things???:
1) decreased PaO2 <60
2) increased H+ concentration
3) increased PaCO2
When the partial pressure of CO2 in CSF increases, the H+ and HCO3- ion concentrations increase immediately.... who's principle or law applies?
Le Chatliers---> derives from law of mass action---> want to achieve equilibrium
Ventilation and perfusion in the UPRIGHT, SPONT VENT, NON-INTUBATED person is BEST in the ______ lung.
The intrapleural space (potential space) is found between parietal pleura of internal chest wall and visceral pleura covering the lung. The intrapleural pressure is "negative" (subatmospheric) b/c the lungs recoil inward and the chest wall recoils outward--> when the inward and outward forces are equal this is called FRC. Which part is altered in the obese patient? In the patient with emphysema?
obese= chest wall
in both instances FRC is altered
~ 3L FRC is normal in the upright, spont breathing 70kg person
During inspiration intrapleural pressure becomes more _______. Air enters the lung because the intrapulmonary pressure is ______.
negative (subatmospheric--> can't actually have a negative pressure)
The _______ couple the lungs to the chest wall.
_______ pressure (pressure between the inside of the chest wall and lungs) is ALWAYS negative (subatmospheric) during normal tidal breathing.
Intrapleural pressure becomes more ______ during inspiration and less _______ during expiration. Intrapulmonary pressure is ______ during inspiration and more ______ during expiration.
Intrapleural becomes more negative during inspiration and less negative during expiration.... intrapulmonary is negative during inspiration and positive during expiration
What are 2 scenarios when intrapleural pressure may become positive?
1) during forced expiration
2) expiratory effort against a closed glottis (valsalva)
Describe the alveoli size in inspiration and expiration in the UPRIGHT, SPONT VENT, NON-INTUBATED patient.
non-dependent alveoli started big and got bigger (so not much change overall); dependent alveoli started small and for bigger (so larger change= BEST ventilation)
*think of a hanging slinky in regards to alveoli
1 atm= ____ mmHg= ______ cm H2O
The dependent lung is dependent on the diaphragm... if you lose diaphragmatic tone you lose _____.
Calculate normal ventilation perfusion mismatch.
V= 4 L/Min (norm MV)
----------------- = 0.8
Q= 5 L/min (norm CO)
0.8 is good but not quite keeping up with perfusion... if it is >1.0 then the perfusion is not keeping up with ventilation
ex) V/Q=3.5...... ventilation is delivering O2 3.5 times quicker than blood flow can take it away
In the awake and spont ventilating pt that is standing, how does PAO2 and PACO2 compare in the apex and base of the lungs?
increased PAO2 in apex, less PACO2 d\t less exchange... INVERSE at base
In the awake and spont ventilating pt that is lying supine (prone or lateral decubitus), how does PAO2 and PACO2 compare in the apex and base of the lungs?
it would be the same in apex as it is the base
Describe how positive pressure ventilation affects the ventilation and perfusion of the lung in a patient lying lateral decubitus that is ANESTHETIZED AND PARALYZED.
the dependent lung is compressed by the weight of the abdominal contents (paralyzed); with positive pressure ventilation, inspiratory gases are preferentially distributed to the nondependent lung--> clinically significant V/Q mismatch--> nondep lung is well ventilated but poorly perfused (deadspacing)..... the dependent lung is well perfused, but poorly ventilated (shunting)
Absolute shunt = ________
V/Q = 0
Venous admixture, or partial shunt= _______
0< V/Q < 0.8
Partial alveolar deadspace, or partial deadspacing= _____
0.8< V/Q < infinity
V= 0 L/min
------------------- = 0
Q= 5 L/min
the above is an example of what?
ex) tumor obstructing the bronchus
V= 4 L/min
------------------- = infinity
Q= 0 L/min
the above is an example of what?
ex) pulmonary emboli
PaO2 ALWAYS ______ when there is a V/Q mismatch.
Name 3 causes of low PaO2.
1) low inspired O2
3) V:Q mismatching
How can you determine the difference between hypoventilation or V/Q mismatch as a source of low PaO2 in a patient?
you must calculate the alveolar arterial blood gradient for O2 and/or CO2
*if the gradient is HIGH then it is the result of mismatch, if it is NORMAL then the pt is hypoxic
There would be _____ A-a gradients if the lungs had PERFECT matching of ventilation and perfusion.
*but normal lungs exhibit some V/Q mismatching (0.8--> more perfusion than ventilation)
The normal PAO2-PaO2 gradient is ______ when breathing room air.
5-15 mmHg (this increases when inspired O2 increases)
*while breathing 100% O2 the normal Aa gradient is <100
The normal PACO2-PaCO2 gradient is ______ when breathing room air.
*regardless of inspired O2
What is a way of obtaining the average PACO2?
PACO2 = ETCO2
How do you calculate the PAO2-PaO2 gradient?
just subtract one from the other
How can you estimate the PaO2 in a healthy patient?
multiply the % O2 by 5
60% x 5= 300 mmHg = PaO2
How can you estimate the PAO2 in a healthy patient?
multiply the % O2 by 6
60% x 6= 360 mmHg = PAO2
What is the normal PaO2/PAO2 ratio, and what does a decrease in this ratio reflect?
a decrease reflects a possible shunt
What is a right to left shunt?
intracardiac shunt--> blood pumped by right heart passes to left heart without being oxygenated
*from anatomic defect or that blood passes through lungs without coming in contact with oxygen in alveoli--> as in ARDS
What is a left to right shunt?
intracardiac shunt--> blood is pumped from left heart back to right as in a neonate when blood is shunted through the ductus arteriosus or formamen ovale
In ANY position, the dependent regions of the lungs are better perfused and better ventilated in the ______.
awake, spontaneously breathing subject
Ventilation perfusion ratios are normally ____ in dependent lung areas and ______ in nondependent lung areas.
What are the two results of normal slight V/Q mismatching?
1) O2 A-a gradient of 5-15mmHg..... arterial blood is 5-15mmHg less than the partial pressure of oxygen in mixed alveolar gas
2) CO2 A-a gradient 2-10mmHg..... CO2 in arterial blood slightly exceeds the partial pressure of CO2 in mixed alveolar gas
What are the 4 zones of West?
just move the "A" to the right for the first 3
IV)= not normal--> wet lungs--> edema--> additional pressure was added
*remember wherever Alveolar pressure is in the "pecking" order is the name of the zone
Explain zone 1.
since arterial pressure is basically negligible--> alveolar pressure exceeds pulmonary artery pressure--> the distensible capillaries of the alveolar wall are collapsed--> No blood flow in Zone I
Explain zone II.
pulmonary artery pressure exceeds alveolar pressure--> there is blood flow in zone 2, and blood flow is proportional to pulm artery pressure minus alveolar pressure (Pa-PA gradient)---> after blood passes through the alveoli of zone 2 it falls into the pulmonary venous system like a waterfall--> zone 2 is waterfall zone
Explain zone III.
blood flow is proportional to the pulmonary artery pressure minus pulmonary vein pressure gradient. The tip of a Swanz Ganz catheter should be placed in zone 3
Explain zone IV.
BF is proportional to the pulmonary artery pressure minus pulmonary interstitial fluid pressure gradient. zone 4, like zone 1 is a pathological zone that normally is not present. zone 4 is present with pulmonary edema
West's zones describe ______ in the lungs.
Zone _____ is better ventilated, better perfused, has a lower V/Q mismatch/ratio, has a less negative intrapleural pressure, and smaller alveoli.
Preoxygenation with 100% O2, and spontaneous ventilation with a tight fitting mask for ____ minutes can furnish up to _____ min of O2 reserve following apnea.
5 min provides 10 min reserve
Why do we preoxygenate=denitrogenate?
to fill the FRC with O2--> provides a reservoir to maintain PaO2 during apnea
What is the normal oxygen consumption? (VO2)
Given the patient has normal O2 consumption (VO2), how long will it take for a patient to develop deleterious side effects following apnea if 2500mL of O2 is found in FRC after preoxygenation?
2500/250= 10 min
What is hypoxic pulmonary vasoconstriction?
-in response to alveolar hypoxia, the alveolar arterioles constrict, thereby decreasing shunt blood flow
Name some pharmacologic things that can decrease hypoxic pulmonary vasoconstriction.
1) direct-acting vasodilators--> nitroprusside, nitroglycerin, hydralazine--> increasing shunt and decreasing PaO2
2) volatile anesthetics--> at higher concentrations (> 1 MAC)
What 3 measures cannot be measured directly with spirometry?
Name 3 methods for measuring FRC.
1) helium dilution
2) nitrogen washout
3) body plethysmography (based on Boyle's Law)
What is FEV1?
forced exp volume in one second
What is FVC?
forced vital capacity--> volume of gas that can be exhaled during a forced expiratory maneuver
What is a ratio that is useful to distinguish between restrictive and obstructive diseases?
What is FEF 25-75?
rate of flow occurring in a forced expiratory flow from the point where 25% of the FVC has been exhaled to the point where 75% has been exhaled---> BEST test for assessing small airway disease
Name common obstructive airway diseases.
Airways are obstructed--> asthma, COPD (bronchitis, emphysema)
Name common restrictive airway diseases.
expansion of lungs and/or chest wall is restricted--> pulmonary fibrosis, pneumothorax, chest wall disease (scoliosis), neuromuscular disease (amyotrophic lateral sclerosis, myasthenia gravis)
What is a normal FEV1?
What is a normal FVC?
What is a normal FEV1/FVC ratio?
normal is usually >0.7
Using the FEV1/FVC ratio how can you tell whether or not it is restrictive disease or obstructive disease?
obstructive if FEV1 and FVC are LOW
FEV1/FVC ratio 0.7
Restrictive, Obstructive, or Normal?
both are relatively normal
Restrictive, Obstructive, or Normal?
both are LOW
this is restrictive
Restrictive, Obstructive, or Normal?
possible obstructive disease
A normal flow volume loop looks like _______. restrictive? obstructive?
an upside down ice cream cone or a pointed side up guitar pic
restrictive: baby ice cream cone.... restricted= smaller volumes
obstructive: one side of the ice cream cone appears caved in and lung volumes are greater
______ is shown on a flow volume loop to be impaired when there is a variable extrathoracic obstruction.
_______ is shown on a flow volume loop to be impaired when there is a variable intrathoracic obstruction.
________ is shown on a flow volume loop to be impaired when there is a large, fixed airway obstruction.
inspiration and expiration
As you move along a tube the pressure will ______.
decrease---> physiologic basis of airway closure
How are CC and CV measured?
by nitrogen washout and helium dilution methods
How does closing volume in the older healthy adult differ than that of a young healthy adult?
airway closure tends to close in the TV instead of after TV... causing air trapping
In a young, healthy adult.... if vital capacity is 4,500mL when would airway closure begin?
typically 10% of VC in young and healthy... so,
4500 x 0.10= 450mL so airway closure begins when 450mL of the VC has been exhaled
The volume at which airway closure begins ______ progressively with age.
Closing volume is _______ in obstructive pulmonary disease.
*emphysema--> loss of collagen and elastin
*chronic bronchitis--> airways are narrower--> pressure drop along the airways is greater
*asthma--> airways narrowed
What are other conditions that can increase closing volume?
smoking, bronchospasm, airway secretions, fluid retention, anesthesia/surgery
Does pulmonary compliance increase or decrease with age? Why?
it increases with age--> elastin and collagen breakdown with age, so the lung tissue becomes easier to distend (elasticity decreases)
How does FRC change with age?
since the lung does not recoil inward with as much force, FRC increases slightly with age (~10%)
Does chest wall compliance increase or decrease with age?
Peripheral chemoreceptors are most sensitive to _____.
decreased Pa O2 (<60)
What is the problem if the patient has a segment of lung with a ventilation:perfusion ratio of zero?
The patient has a left to right shunt (not sure, I thought it was right to left)