Card Set Information
What are the lung volumes as seen on spirometry?
Tidal Volume (Vt)
: 500mL, normal amount of gas that enters or leaves in a single respiratory cycle
Functional Residual Capacity (FRC)
: 2700mL, volume of gas left in lungs at end of Vt (passive expiration)
Inspiratory capacity (IC)
: 4000mL, volume of gas that can be inspired from FRC
Inspiratory Reserve Volume (IRV)
: 3500mL, volume of gas that can be additionaly inhaled after normal inspiration
Expiratory Reserve Volume (ERV)
: 1500mL, volume of gas that can be additionaly exhaled after normal expiration
Residual Volume (RV)
: 1200mL, amount of gas left in lungs after maximal expiration
Vital Capacity (VC)
: 5500mL, maximal volume that can be expired after maximal inspiration
Total Lung Capacity (TLC)
: 6700mL, total amount of gas in lungs after maximal inspiration.
Draw a mental spirometry lung volume curve?
What cannot be measured using spirometry, what is used instead?
Residual Volume (RV), or anything containing RV (TLC, FRC)
What is total ventilation?
Total ventilation (ve)= Vt x RR.
Where does anatomic dead space end, what is a good way to approximate anatomic dead space?
Persons weight in pounds (i.e. 150lbs = 150mL dead space).
What constitutes alveolar dead space?
Alveoli containing air but without blood flow in surrounding capillaries.
What is the physiologic dead space?
Total dead space: anatomical + alveolar dead space.
What is alveolar ventilation?
Alveolar ventilation (Va) = (Vt-Vd) x RR
: Tidal volume
: Dead space.
What is the difference between increasing depth of breathing versus rate of breathing?
: increases actual alveolar ventilation because dead space does not change
: more ventilation of dead space.
What is the major muscle of inspiration?
Chest wall second.
What is the major muscle of expiration?
: passive process, relaxation of inspiratory muscles
: Abdominal muscles.
What are the two main forces acting on the lung?
: acts to collapse lung
: usually subatmospheric (negative pressure), acts to expand the lung (or collapse when positive pressure).
What happens to systemic venous return and R ventricular output with inspiration?
Both are increased.
What happens to venous return to L heart and L ventricular output in inspiration?
Both are decreased.
What is the reflex increase in heart rate with inspiration (sinus arrythmia)?
Expansion of R atrium -> drop in BP -> reflex increase in HR.
What does a valsalve maneuver do?
Increase intrapleural pressure
Increase central venous pressure
Decrease venous return.
What is the point of PEEP?
: positive end expiratory pressure
prevents collapse of small alveoli (atelectasis).
What are the changes that occur with a simple pneumothorax?
Intrapleural pressure increases
Lung recoil decreses (lung collapses)
Chest wall expands.
Tension pneumothorax most commonly occurs in?
Patients on positive-pressure ventilator.
What is compliance?
What happens to compliance as lungs inflate?
Very compliant lungs have decreased?
Stiff lungs have increased?
What are the two components of lung recoil?
: collagen and elastin fibers, larger lungs have greater recoil
: Greatest component of recoil.
How does the law of LaPlace involve two different sized alveoli?
If wall tension is the same in both alveoli, the smaller alveolus will have greater pressure
i.e. more likely to collapse.
What are the three main functions of surfactant?
Lowers surface tension
: lowers lung recoil, increases compliance
Lowers surface tension more in smaller alveoli
: decreases tendency for atelectasis
Decreases capilllary filtration pressure
: Decreases negative intrathoracic pressure.
What is the cause of infant respiratory distress syndrome, another name?
Deficiency of surfactant
Hyaline Membrane Disease.
What are the two main causes of adult respiratory distress syndrome (ARDS)?
: injury to endothelial capillary membrane by neutrophils
: direct injury to lung epithelium.
What are the three main symptoms of ARDS?
Increased lung recoil, decreased compliance
Resistance of an airway equals?
What bronchi represent most of the airway resistance?
First and second.
What produces bronchoconstriction?
Parasympathetic nerve stimulation.
What produces bronchodilation?
What is normal FEV1/FVC?
What characterizes obstructive pulmonary disease, what is it measured as?
Increase in airway resistance
Decreased expiratory flow rates
What characterizes restrictive pulmonary disease, what is it measured as?
Inrease in lung recoil, decreased compliance
Most lung volumes decreased, especially FRC, RV
How do you calculate the partial pressure of a gas?
Pgas = Patm x Fgas
: partial pressure of gas
: concentration of gas
: atmospheric pressure.
How do you calculate the partial pressure of an inspired gas?
PIgas= Fgas x (Patm-PH2O).
What does partial pressure of water (PH2O) depend on?
at 37 C
: 47 mm Hg.
What is the normal Alveolar-arterial (A-a) gradient?
5-10 mm Hg.
What two factors affect alveolar PCO2 (PACO2)?
Metabolic production of CO2
: constant under normal circumstances
: inversely related to PACO2.
What is the equation showing factors that affect Alveolar PO2 (PAO2)?
PAO2 = (Patm-47)FIO2 x PACO2/R
: Respiratory exchange ration = o.8.
What factors affect diffusion of a gas between alveoli and capillaries (gas exchange)?
Fick Law of Diffusion
Vgas= A/T x D x (P1-P2)
: rate of gas diffusion
: surface area of lung
: Thickness of membrane
: Pressure gradient.
What are the two terms to describe dynamics of substance transfer b/w capillaries and interstitium?
: the substance equalizes
: the substance does not equalize.
What is a classic, always diffusion limited substance?
Carbon Monoxide (CO).
What is a normal CO uptake?
What is the normal carrying capacity for O2?
.2mL O2/1 mL blood.
What shifts the O2-Hb curve to the left?
Increased CO2 (Bohr Effect)
Increased H+ (decreased pH)
What shifts the O2-Hb curve to the right?
Everything opposite as left
Fetal Hemoglobin (HbF)
Stored blood (loss of 2,3-DPG).
About 90% of CO2 is carried as?
Plasma Bicarbonate (H2CO3).
What enzyme is needed to convert CO2 into bicarbonate, where is it found?
Insede red cell
CO2 + H2O -> H2CO3 -> H+ + HCO3-.
What is the main drive for ventilation under normal conditions?
CO2 (H+) on central chemoreceptors.
Where are the central chemoreceptors found, what do they sense?
Close to surface of medulla
: CO2 freely crosses BBB, bicarbonate dissociates -> H+.
What are the two peripheral receptors and afferent nerves?
: Carotid sinus, Glossopharyngeal nerve IX -- most important
: Aortic arch, Vagus nerve X.
What do the peripheral receptors respond to?
PO2 in very hypoxic situations.
Which receptors adapt, which do not?
Central chemoreceptors adapt
Peripheral do not.
What nerve communicates the medulla (breathing center) to the diaphragm?
A lesion at what levels would preveng diaphragmatic breathing?
Complete C1 or C2.
What is Apneustic breathing?
Prolonged inspiration with shortened expiration
Lesion in caudal pons.
What is Biot's breathing?
Alternating apnea with periods of identical depth breaths
Seen in increased intracranial pressure and midbrain lesions.
What is Cheyne-Stokes breathing?
Alternating apnea with periods of "crescendo-decrescendo" depth breaths
Seen in infants and sleep, also some midbrain lesions.
What are four causes of hypoxemia?
Pulmonary (right to left) shunt
What happens to the A-a gradient with hypoventilation?
Decrease of PO2 equal in all compartments (Alveolar, end capillary, systemic arterial).
What does an A-a gradient greater than 10 usually signify?
What is a clue of a pulmonary shunt?
Failure to correct hypoxemia with supplemental oxygen.
Which alveoli recieve more ventilation, apex or base?
: higher compliance (less inflated at rest)
Apex have more negative pressure -> more inflated at rest -> lower compliance.
What is the ideal ventilation/perfusion (V/Q) ratio, what does it mean when it is lower, higher?
: 0.8, pH= 7.4
V/Q < 0.8
: underventilated, pH <7.4
V/Q > 0.8
: overventilated, pH > 7.4.