CB L22-24: Lung volumes and capacities

Why is intrapleural pressure negative?

Lungs are elastic and would collapse and expel all air if it wasn't for the negative intrapleural pressure that holds them against the chest wall intra-alveolar pressure and atmospheric pressure are the same so those are normalized to zero intrapleural pressure is less so it is a negative number its all relative

how do you calculate the PO2 in the alveolus at sea level?

PAO2 = FiO2 (Pb-47) - (PaCO2/R) - predicts the change in alveolar PO2 that will occur for a given change in arterial PCO2 PAO2 = alveolar PO2 FiO2 = concentration of O2 Pb = barometric PaCO2 = arterial PCO2 R = V/Q mismatch (usually 0.8)

How do you calculate PO2 in the AIRWAY at SEA LEVEL

PO2 = FO2 * (Pb-Ph20) Ph20 = 47 so .21* (760-47) PO2 = 150 mmHg this is breathing 100% O2 if you were breathing 50% O2 it would be (760-47)*2 * .21

how do you calculate the PO2 in the atmosphere at sea level?

PO2 = FO2 * Pb PO2 = 0.21 * 760 PO2 = 160 mmHg

what would happen if alveolar pressure and barometric pressure were the same?

Pa=Pb --> no flow because no pressure gradient

how do you calculate the PO2 in the atmosphere at denver?

Pb = 625mmHg so PO2 = FO2 * Pb .21 * 625 = 131 mmHg

what is the partial pressure equation?

Pg = Fg * Pb -partial pressure of a gas is Pg (g change for the gas like Po2, Pn2, etc.) -Fg is fractional concentration (its molar fraction) -Pb is barometric pressure, this is what changes, the fractional concentration doesn't

What is anatomical dead space?

The amount of gas that stays in the pipes, the conduction zone. the internal volume of all conducting (non-gas exchaning) airways from the nose and mouth to the respiratory bronchioles

What is the atmospheric pressure at sea level?

760 mmHg

what is FEV1/FVC for obstructive diseases?

< 80% like w/ epmhysema FEV1 is reduced d/t increased resistance to airflow or lungs not contracting quickly enough from increased compliance

what is FEV1/FVC for restrictive diseases?

> 80% decreased compliance limits inspiratory volumes without impairing expiration limited inspiratory volumes result in smaller FEV1 and FVC volumes

At the very start of Expiration at sea level, the CO2 partial pressure in the Anatomic Dead Space is normally about A.0 mmHg B.40 mmHg C.65 mmHg D.100 mmHg E.150 mmHg

A there is no CO2 in the air so there should be none in the anatomic dead space, in the alveolar dead space would be a different question

You go snorkeling with a friend, he decided that he wants to snorkel at a deeper depth so he rigs an extension onto his snorkel. He would: A.be able to see cooler things B.need to breath at a smaller tidal volume C.need to breath at a larger tidal volume D.need to breath at a lower frequency E.need to breath at a higher frequency

A (Just kidding, but really) C you increased the dead space by increasing the length of snorkel holding air

what is restrictive lung disease?

A large group of disorders that restrict or reduce lung volume and tidal volume. Include loss of functioning of the alveoli-capillary unit (impairment in gas exchange), altered mechanical function of the thorax and pulmonary system, and secondary cardiovascular dysfunction. -reduced lung expansion -hard to get air IN -like a stiff balloon

what is residual volume?

Air in lungs after maximal expiration. Cannot be measured on spirometry

What is inspiratory reserve volume?

Amount of air that can be forcefully inhaled after a normal tidal volume inhalation the extra volume above tidal IRV

For a maximal inspiration followed by a maximal expiration, the total volume expired is A. Tidal volume (TV) B. Vital capacity (VC) C. Functional residual capacity (FRC) D. Expiratory reserve volume (ERV) E. Residual volume (RV)

B

What is the partial pressure of oxygen in the atmosphere at sea level (barometric pressure = 760 mm Hg) A. 600 mm Hg B. 160 mm Hg C. 0.3 mm Hg D. 47 mm Hg E. 0.0 mm Hg

B

what is obstructive lung disease?

Big mucus-filled lungs, trouble breathing out limitation of airflow due to partial or complete obstruction hard to get air OUT

In a normal subject breathing ambient air on the top of mount everest... A- fractional composition of O2 is < 15% B- fractional composition of O2 is > 21 % C- partial pressure of oxygen in the atmosphere is > 160 mmHg D- partial pressure of oxygen in the atm is < 160 mmHg

D composition of O2 doesn't change so A and b are wrong barometric pressure is greater at sea level which pO2 is 160 so at a higher altitude the po2 will not increase

A healthy 22-year-old man breathes in as much air as he can and then exhales as much air as possible. The lung volume at maximum inspiration is 6.0 L and the lung volume after maximum expiration is 1.0 L. His tidal volume at rest is 0.5 L and his functional residual capacity is 3.5 L. What is his vital capacity? A.3.0 L B.3.5 L C.4.0 L D.5.0 L E.5.5 L

D 6 - 1

What is transpulmonary pressure?

Difference between the intrapulmonary and intrapleural pressures (Ppul - Pip). Keeps the airways open. aka dif between alveolar pressure and pleural pressure (Palv-Plp)

We use Alveolar Ventilation Rate instead of Minute ventilation to discuss the lung's ability to release CO2 because normally at rest, A.during inspiration, only 300 ml of fresh air enters the mouth. B.during expiration, only 300 ml of air leaves the alveoli. C.during expiration, only 300 ml of air leaves the mouth. D.the tidal volume is normally less than the Anatomic Dead Space. E.only the first 300 ml of air leaving the alveoli passes through the mouth

E

What is Boyle's Law?

The relationship between the pressure and volume of a gas. P varies inversely with V. P1V1 = P2V2. at a constant temperature system, decreasing the volume increases the pressure bc inc number of collisions against the container walls opposite for increasing volume

What is FEV1/FVC?

This is the percentage of the vital capacity which is expired in the first second of maximal expiration. In healthy patients the FEV1/FVC is usually around 80%.

what is emphysema?

a condition in which the air sacs of the lungs are damaged and enlarged, causing breathlessness. leads to irreversible airflow obstruction -lungs lose elasticity, breathing out becomes difficult, air is trapped in overinflated lungs -slinky is too floppy so it can't contract back to normal -lungs are stretched too much and can't recoil/collapse -the surface area for gas exchange decreases, alveolar sacs aren't tiny balloons, they are big inelastic bags that you can't get air out of

how does air get into the lungs?

air flows into the lungs if pressure on the OUTSIDE (Patm) is GREATER than pressure on the INSIDE aka bulk flow! High pressure --> low pressure PA < Pb --> inspiration increased intrathoracic volume and decreased pressure = expansion

how does air get out of the lungs?

air flows out of the lungs if pressure on the inside is greater than pressure on the outside PA > Pb decreased volume leads to increased pressure to move air out of the lungs

What is expiratory reserve volume?

air that can still be breathed out after normal expiration forced exhalation, the max exhalation ERV

at end expiration, what are the conducting airways filled with?

alveolar air, not fresh air, breath from the previous breath that is mixed

What is alveolar dead space?

alveoli that cease to act in gas exchange due to collapse or obstruction not 100% of ventilated alveoli are perfectly perfused leading to V-Q mismatch and wasted ventilation like if there is capillary blockage, there is no oxygen exchange into the blood

what is tidal volume?

amount of air inhaled and exhaled during a normal breathing cycle. TV

What is physiological dead space?

anatomical dead space + alveolar dead space the portion of each tidal breath that is not involved in gas exchange

what are examples of obstructive lung disease?

asthma, chronic bronchitis, emphysema, COPD, CF

why does the chest expand as a single unit?

cohesive forces lungs normally wanna collapse but when the ribcage expands the lungs follow d/t forces when the diaphragm contracts and increases thoracic volume, the lung slides against the thoracic wall and lung volume increases by a similar amount

what is the FEF25-75 for obstructive diseases compared to normal?

decreased

what is the FEV1 for obstructive diseases compared to normal?

decreased

what is the FEV1 for restrictive diseases compared to normal?

decreased

what is the FVC for obstructive diseases compared to normal?

decreased

what is the FVC for restrictive diseases compared to normal?

decreased

what is the FEV1/FVC for obstructive diseases compared to normal?

decreased (< 80)

what is dalton's law?

each gas in a mixture of gases exerts its own pressure as if no other gases were present barometric pressure = sum of partial pressures of all the other gases Pb = PN2 + PO2 + Pother

what happens to the volumes and capacities of the lungs in restrictive diseases?

everything decreases in comparison to normal can't fill as much bc tough, means there is less to expel as well

what is pulmonary fibrosis?

excessive amount of fibrous or connective tissue in the lung causes lung tissue to become damaged and scarred -harder for lungs to expand during inhalation -impairs diffusion of O2 and CO2 -THICK walls, harder to inflate, impairs oxygen diffusion (CO2 can still diffuse and dilate)

ERV

expiratory reserve volume additional volume below the TV that can be expired

what is functional residual capacity?

expiratory reserve volume + residual volume FRC

at end inspiration, what are the conducting airways filled with?

fresh air

FRC

functional residual capacity volume remaining in the lungs after normal tidal volume expiration ERV + RV

how does the FVC change for emphysema?

harder to get air out, takes a longer time to expel 100% of VC

what is the FEF25-75 for restrictive diseases compared to normal?

increased

what is the FEV1/FVC for restrictive diseases compared to normal?

increased (> 80)

IC

inspiratory capacity TV + IRV

IRV

inspiratory reserve volume additional volume above the TV that can be expired

what happens to airflow once it passes the nose and mouth?

it enters dead space where no gas exchange occurs but a volume is held

what happens to the TLC, RV, and FRC in emphysema?

it increases! the ability to get air IN is not changed, the ability to get air OUT is greatly reduced the volume increases due to trapped air

what happens when a knife penetrates the ribs and lungs?

it separates the cohesive forces, so allows the lungs to collapse and the ribs to expand

what is forced expiratory flow?

measurement of expiratory FLOW RATE (V/t) over middle half of the FVC FEF 25-75 forced expiratory flow between 25 an 75% FVC how rapidly air goes out faster is greater slope, slower is slower slope

what is ventilation?

movement of air in and out of the lungs per unit time measured in volume/time v w/ a dot over it

what is pressure directly proportional to?

nRT (number of molecules in a container, temperature aka kinetic energy) -more molecues = more collisions = more pressure -heating a gas will increase velocity (KE) producing more collisions and increase pressure

does the percentage of gases change with altitude?

no, always 78% N2 21% O2 1% Ar what changes is their partial pressure depending on the atmospheric pressure

what are the cohesive forces of the intrapleural space?

pleural sac forms a double membrane surrounding the lungs, similar to a fluid filled balloon surrounding an air filled balloon allows for the membranes to slide the cohesive forces help keep the different spaces together without actually being connected

what is alveolar pressure?

pressure of air inside the lung alveoli

what is pleural pressure?

pressure of the fluid in the thin space between the lung pleura and the chest wall pleura

what is the volume you can't get out?

residual volume

RV

residual volume volume of gas remaining in lungs after a maxed forced expiration

what are the symptoms of pulmonary fibrosis?

shortness of breath, a dry cough, chest pain, fatigue and weakness, They have a faster breathing rate than normal finger clubbing

what are the symptoms of emphysema?

shortness of breath, wheezing, coughing, barrel chest, hypoxemia, inc risk of cor pulmonale (d/t RH more work leads to RHF), hyperventilation dec CO, weight loss, muscle wasting

what is the kinetic theory of gas?

the constant motion of particles in a gas allows a gas to fill a container of any shape or size 1. Gases consist of molecules. 2. Gas molecules randomly move and collide with one another and with walls of container. 3. Pressure is caused by collision of gas molecules with walls. 4. The pressure exerted by a gas or mixture of gases depends upon the number of collisions that take place. 5. The greater the number of gas molecules in a given space, the greater the number of collisions and hence, the higher the measured gas pressure.

What is atmospheric pressure?

the pressure exerted by the weight of the atmosphere, around 760 aka barometric pressure

what is vital capacity?

the volume of air that the patient can exhale after a maximal inhalation. everything but residual volume

what happens to the ERV and vital capacity in emphysema?

they decrease exhalation is slower and volume exhaled is reduced TV may increase because lungs are more compliant

TV

tidal volume normal quiet breathing that involves inspiration and expiration

what is inspiratory capacity?

tidal volume + inspiratory reserve volume

TLC

total lung capacity sum of all lung volumes

VC

vital capacity volume expired after maximal inspiration (IC + IRV)

what is total lung capacity?

vital capacity + residual volume

What is forced vital capacity (FVC)?

volume of air exhaled from full inhalation to full exhalation a measurement of ventilation the forced exhalation volume in a normal lung will take about 3 seconds for 100% of VC to be expired

what is VE?

volume of air expired per minute VE = Vt*f -tidal volume, frequency normal is 6 L/min (0.5 L/breath * 12bpm)

what is alveolar ventilation?

volume of air that reaches the respiratory zone volume of fresh air entering or leaving the alveoli per minute

why is alveolar ventilation different than minute ventilation?

you have air trapped in conduction airways that does not participate in gas exchange, the air trapped never reaches the alveoli, so its ventilation is lower than minute ventilation it is a better measure of respiratory function

what is atmospheric pressure at high altitudes?

~ 520 torr/mmHg

what is the alveolar ventilation equation?

"VA=(VT-VD)f use ideal body weight for VD" Vd is dead space in the lungs normal is ~ .15L so 4.2 L/min alveolar ventilation

A patient is artificially ventilated during surgery at a rate of 20 breaths/min and a tidal volume of 250 ml/breath. Assuming a normal Anatomical Dead Space is 150 ml, the alveolar ventilation in this patient is A.1000 ml B.2000 ml C.3000 ml D.4000 ml E.5000 ml

(250-150)*20 B

what causes pulmonary fibrosis?

-Environmental particles (contaminants) are inhaled -Causes: -->Asbestos -->Silica -->Coal -->Dust -history of smoking -male gender

how do you measure anatomic dead space?

-expire maximally -inspire 100% oxygen -exhale while measuring nitrogen content of expired air 1st air that leaves will be fully o2, but after that air from the alveoli (n2) is dead space air

what are some examples of restrictive lung disease?

-interstitial lung disease -pulmonary fibrosis -obesity -chest wall damage -neuromuscular diseases

what is the normal respiratory rate?

12-20 breaths per minute (f)

what is the tidal volume of normal breathing?

500 mL/breath