work In healthy lungs is...

Pressure Outside Airway

P_ao

Alveolar pressure (P_alv), often referred to as

intrapulmonary pressure

it varies during the breathing cycle

Pleural pressure (P_pl)  in the fluid of the pleural space is usually

negative (i.e., subatmospheric) during quiet breathing.

P_pl also varies during the breathing cycle.

The trans-respiratory pressure gradient (P_rs) represents

the difference in pressure between the atmosphere (body surface) and the alveoli:

P _rs  = P _alv  - P _bs

Note: Pbs same as Pao

causes gas to flow in an out of alveoli

The transpulmonary pressure gradient, or P_L, equals

the pressure difference between the alveoli and the pleural space, as shown in the following equation:

P _L  = P _alv  - P _pl

P_L is

the pressure difference that maintains alveolar inflation. (P_L is also commonly represented by the symbol P_TP.)

Note: has to keep pressure just slightly negative at all times

P _L  = P _alv  - P _pl

P_w is the pressure across the chest wall.

P _w  = P _pl  - P _bs

represents total pressure necessary
to expand or contract lungs and chest wall

During a normal breathing cycle,

glottis remains open.
P_bs and P_ao remain at 0 (i.e., atmospheric)
only changes in P_alv and P_pl are of interest.

Note: only ones that change are alveolar and pleural pressures

Thoracic expansion causes

The “negative” (i.e., subatmospheric) transrespiratory pressure gradient causes

end-inspiration

As expiration begins, the thorax

The transpulmonary pressure gradient narrows and

This positive transrespiratory pressure gradient causes

air to flow from the alveoli toward the airway opening.

Note: make sure to know which ones go more negative and positive - when

Elastic and collagen fibers found in

lung parenchyma (lung tissue)

The recoil of the lung is

What opposes lung inflation

Compliance

Measurement of pulmonary compliance in a patient requires

emphysema causes

Chest Wall Compliance

same volume as lung compliance

chest wall wants to expand, lungs want to deflate

Total Compliance

is 0.1L/cmH2O (half of each individual measure

Frictional (Nonelastic) Opposition to Ventilation

tissue viscous resistance and airway resistance.

Tissue resistance accounts for only approximately

ascites

= fluid in the abdomen

Airway resistance (Raw) accounts for

approximately 80% of the frictional resistance to ventilation.

RAW formula is opposite of compliance formula

Airway resistance in healthy adults

tracheobronchial

same as transitional

Approximately 80% of the resistance to gas flow occurs (where?)

Resistance to gas flow in

Trachea and bronchi

30%

In airways of healthy subjects, airway collapse occurs only with

The oxygen cost of breathing in healthy individuals averages

Expansion of the lower chest is (less/more?)

bases of lung receive approx four times as much ventilation as

Lung units with high compliance have ______ elastic recoil than normal. These units fill and empty ______ than do normal units.

Lung units with low compliance (high elastic recoil) ______ their volume less. They fill and empty ______ than normal.

A lung unit will have a long time constant if resistance or compliance is ______

Lung units have a short time constant when resistance or compliance is ______ .

dead space

Note: areas of the lung that don't participate in gas exchange

Minute Ventilation

V(dot)_E = RR • V_T

Alveolar Ventilation

Note: VA = RR x (VT x VD)

anatomic dead space and alveolar dead space. When these are considered together, they often are referred to as physiologic dead space.

anatomic dead space, or V_Danat. V_Danat averages approximately 1 ml per pound of ideal body weight (2.2 ml/kg).

Ideal Body Weight for a male calculates as:

IBW Male = 106 + 6(H" - 60)

IBW Female = 105 + 5(H" - 60)

answer is in pounds -

divide by 2.2 to get kg

Alveolar Dead Space

alveoli are ventilated but not perfused with mixed venous blood

The volume of gas ventilating unperfused alveoli is called

Alveoli at the apices (top corners) of the lungs have how much perfusion?

minimal or no perfusion

Note: because of gravity - less blood flow

The sum of anatomic and alveolar dead space is called

physiologic dead space (V_Dphy):

Dead Space/Tidal Volume Ratio

V_Dphy is often expressed as a ratio to tidal volume

 V_D/V_T = (P_aco2 - P_eco2)/ P_aco2

Note: paco minus peco divided by paco = dead space over tidal volume

High respiratory rates and low tidal volumes result in

a high proportion of wasted ventilation per minute (low V(dot)_A).

Note: shallow & fast

most efficient breathing pattern is

normal adult at resting metabolic conditions produces how much CO₂ per minute? 

hypoventilation

Hypoventilation is indicated by

hyperventilation

hyperpnoea

increased breathing rate

Effectiveness of ventilation

(P_bs)

equal to atmospheric pressure, usually 0

Compliance of a healthy adult lung