Respiratory Physiology I Flashcards by Joanna Brown

List the muscles of expiration

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List the muscles of inspiration

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Contraction of the inspiratory muscles reduces _____ and increases ______. What law is this an example of?

thoracic pressure

thoracic volume

Boyle’s Law

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During inspiration, which muscle(s) increase A-P diameter?

Which muscle(s) increase superior-inferior dimension?

External intercostals

Diaphragm

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What are the accessory muscles of inspiration?

Sternocleidomastoid

Scalenes

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Active exhalation is carried out by:

What’s a good mnemonic for this?

the abdominal muscles

I let the air out of my TIREs:

Transverse Abdominus

Internal Oblique

Rectus Abdominus

External Oblique

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What vital capacity is required in order to form a good cough?

15 ml/kg

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The functional divisions of the airway can be divided into three zones:

Conducting

Transitional

Respiratory

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The conducting zone begins at the ____ and ends at the ______

Nares

Terminal Bronchioles

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______ is the last structure perfused by the bronchial circulation

Terminal bronchioles

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The transitional zone contains:

the respiratory bronchioles

Dual function of air conduction and gas exchange

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The respiratory zone consists of _____ and _____

Alveolar Ducts

Alveolar Sacs

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List the levels of the airway, from the trachea down

Trachea
Bronchi
Bronchioles
Respiratory Bronchioles
Alveolar Ducts
Alveolar Sacs

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What is the last are of the airway that contains cartilage?

Bronchi

Bronchioles DO NOT have cartilage

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What is the last area of the airway containing smooth mucles?

The alveolar ducts

The alveolar sacs are the only structures that do not have any

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Gas exchange occurs across ____ cells by ______

Type 1

Diffusion

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Alveolar Pressure is the pressure _______

Intrapleural pressure is the pressure _______

inside the airway

outside the airway

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Transpulmonary Pressure = ______ - ______

Alveolar Pressure - Intrapleural pressure

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If TPP is positive, the airway _______

If TPP is negative, the airway _______

Opens

Closes

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DURING TIDAL BREATHING

Transpulmonary Pressure is always ______

Intrapleural pressure is always ________

Positive (keeps airway open)

Negative (keeps lungs inflated)

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Alveolar pressure becomes slightly ______ during inspiration

and slightly _____ during expiration

negative

positive

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There are only two times when intrapleural pressure becomes positive:

Forced expiration

Pneumothorax

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What is the transpulmonary pressure?

Is air moving in or out?

-1

You use the first area in the lungs to deflate

15 - (+16) = -1

Out - Forced Expiration

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What is the TPP? Is air moving out or in?

-1 - (-8) = 7

Air is moving in (inspiration)

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Minute ventilation = ______ x \_\_\_\_\_\_\_

Tidal Volume x RR

Alveolar Ventilation = ________ x \_\_\_\_\_\_\_\_\_

(TV - dead space) x RR

What is the V_T? What is a normal V_T?

Tidal Volume is the amount of gas that is inhaled and exhaled during a breath 6-8 mlkg

What is the V_T? What is a normal V_T?

Tidal Volume is the amount of gas that is inhaled and exhaled during a breath 6-8 ml/kg

What is V_d? What is a normal V_D?

Dead space ~ 2 ml/kg (150 ml)

Any condition that increases VD also increases:

The PaCO₂ - EtCO₂ gradient Makes it harder to expire gases from the airway, causing CO2 retention

How can you predict PaO2 by age?

How do you calculate static compliance?

How do you calculate Dynamic Compliance?

What are some factors that increase dead space?

Anything that increases the volume of the conducting zone OR Reduces pulmonary blood flow e.g. Hypotension (reduces pulmonary blood flow) Atropine (bronchodilates, which increases the volume of the conducting zone) PPV (increases ventilation relative to perfusion, which is another way of saying that dead space is increased)

What are some factors that decrease dead space?

Anything that reduces the volume of the conducting zone or increases pulmonary blood flow e.g. ETT, LMA, neck flexion

What are the four types of dead space?

Anatomic Alveolar Physiologic Apparatus

What are two examples of apparatus dead space?

Heat and Moisture Exchanger Face Mask

What is physiologic dead space?

Anatomic dead space + alveolar dead space

What causes alveolar dead space?

Decreased pulmonary blood flow

What is the Vd/Vt ratio?

Ratio between dead space and ventilation

What is the Vd/Vt for a 65 kg woman with a Vt of 350 ml?

We assume adults have a Vd of 2 ml/kg, which would mean she has 130 ml dead space 130 ml/350ml = 0.37

How does mechanical ventilation effect Vd/Vt?

It increases it to about 50% (0.5) BECAUSE It increases the V/Q ratio, which essentially means it increases dead space

What is the most common cause of increased Vd/Vt under general anesthesia?

Decreased cardiac output If etCO2 abruptly decreases, this should be your first suspicion before looking for other causes of increased dead space

What disease states cause increased Vd?

Decreased CO COPD PE

Neck flexion and extension have what effect on Vd?

Flexion: reduces the amount of hypopharynx open, and therefore reduces dead space Extension: opens the hypopharynx, increasing dead space

In a circle system, dead space begins at:

the Y piece

How is physiologic dead space calculated?

The Bohr Equation

Many clinicians use ______ and ______ to estimate dead space

The difference between the PaCO2 and the etCO2

In the textbook patient: V = Q = V/Q =

4 L/min 5 L/min .8

What is compliance?

Change in Volume \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Change in Pressure

When upright, blood flow predominantly to the lung bases. Why doesn't the V/Q ratio get smaller?

Because alveoli in the base also have higher *compliance*: for a set pressure, they take in more volume more volume = more gas exchange

Which alveoli have the poorest compliance? Which have the highest?

Apex Base

Describe V/Q in the non-dependent portion of the lung

Describe V/Q in the dependent area of the lung

What determines how “ventilated” any particular alveoli is?

The alveoli with the greatest ventilation are the ones that undergo the greatest *volumetric change* Better compliance = better ventilation

Is this dead space or shunting?

Dead Space

Is this dead space or shunting?

Shunt

What is the most common cause of hypoxemia in the PACU?

Atelectasis

Blood passing through an underventilated alveoli tends to ______ CO2

retain and is unable to take in oxygen

Blood passing through an overventilated alveoli tends to ______ CO2

give off too much CO2 (more than the alveoli could empty out), but it can't take up a proportional amount of oxygen (just because you're giving off more CO2 does not mean you're getting more O2 because of the dissociation curve)

Which is usually effected by a V/Q mismatch: PAO2-PaO2 or PACO2-PaCO2 Why?

Usually just the O2 A-a gradient is effected The lung compensates by overinflating alveoli. This works at eliminating CO2, but not at getting O2 in

How does the body combat shunt?

hypoxic pulmonary vasoconstriction reduces pulmonary blood flow to hypoventilated alveoli

How does the body combat dead space?

Bronchioles constrict to minimize airflow to poorly perfused alveoli

The law of Laplace regarding spheres states that:

As the radius of a sphere increases, the wall tension increases as well

The tendency of an alveolus to collapse is directly proportional to \_\_\_\_\_\_ and indirectly proportional to \_\_\_\_\_\_

more surface tension = more likely to collapse smaller radius = more likely to collapse

Why are alveoli pressures constant, despite varying sizes?

Every alveolus has the same amount of surfactant As the radius decreases, the concentration of surfactant increases As the radius increases, the concentration of surfactant decreases the surface tension therefore remains the same

Zone 1 = Zone 2 = Zone 3 = Zone 4 =

Zone 1 is equivalent to a V/Q =

Infinity

Where does Zone 1 usually occur in the lung?

It doesn't. Purely pathological. Hypotension, PE, excessive airway pressure

Zone 3 is equivalent to a V/Q =

0 Shunting!

What West Zone should a PA cath be placed in? Why?

Zone 3 The pressure in the capillary is always higher than the alveolus, and the vessel is always open

What causes Zone 4?

Interstitial edema, usually from: 1. Increased hydrostatic pressure (fluid overload) 2. Increased negative pressure (flash pulmonary edema)

What is the most common cause of increased dead space intraoperatively?

Decreased cardiac output

What is the Bohr equation?

Compares the partial pressure of CO2 in the blood to the partial pressure in exhaled gas. Allows us to calculate dead space.

Why does it matter that FRC is reduced by anesthesia?

FRC is the reservoir of oxygen that prevents hypoxemia during apnea If the FRC is reduced, these patients will have very, very short tolerance of apneic episodes

What are the anesthesia-related causes of reduced FRC?