CCP Exam two

Respiration

Gas exchange between external environment and alveoli/cells like CO₂ and O₂. (Gas exchange happening across AC membrane)

Ventilation

Mechanical movement of air in/out the lungs like CO₂

Driving Pressure (Pressure Gradient)

Pressure difference between two points that determines flow.

Peak Inspiratory Pressure (PIP)

Measured at the mouth/nose of the highest point on inspiration (Peak pressure at inspiration)

Peak End Expiratory Pressure (PEEP)

What's left in the lungs at the end of expiration (Peak pressure at end expiration)

Transairway Pressure (Pta)

Pressure difference between mouth pressure (Pm) and alveolar pressure (Palv). (p that makes gas go in/out airways)

Pta Formula

Pta = Pm - Palv

mmHg and cmH₂O conversion factor

1.36

In healthy lungs Pta should always be

Transairway pressure should always be positive in healthy lungs.

Pta calculation during inspiration

(pm= 760 - palv= 757 = 3 mmHg), causing gas to enter the chest.

Pta calculation during expiration

(Pm = 760 - Palv = 763 (higher due to expiration from alveoli) = -3 mmHg), causing gas to leave the chest.

Transpulmonary Pressure (Ptp)

Pressure difference between alveolar pressure (Palv) and pleural pressure (Ppl).

Ptp Formula

Ptp = Palv - Ppl

Ptp Example Calculation

If Palv = 760 mmHg and Ppl = 755 mmHg, Ptp = 5 mmHg (760 - 755).

Palv and Ppl Relationship

Palv is always greater than Ppl.

Palv during Inspiration and Expiration

Palv is positive and the same on inspiration and expiration.

Transthoracic Pressure (Ptt)

Pressure difference between alveolar pressure (Palv) and body surface pressure (Pbs).

Ptt Formula

Ptt = Palv - Pbs

Ptt calculation during inspiration

If Palv = 757 mmHg and Pbs = 760 mmHg, Ptt = -3 mmHg on inspiration (Palv is less than Pbs).

Ptt calculation during expiration

If Palv = 763 mmHg and Pbs = 760 mmHg, Ptt = 3 mmHg on expiration (Palv is more than Pbs).

Ptt opposing force to

Opposing force to transairway pressure so on inspiration this pressure is always negative.

Diaphragm and Pressure Gradient

Pressure gradient is generated by contraction and relaxation of the diaphragm.

Inspiration Mechanics (Diaphragm)

Contraction of diaphragm (downward movement which increases out thoracic cavity volume = Low Ppl and Palv (our decreased pressure)

End Inspiration

Equilibrium = No delta P = No pressure/force (done breathing in)

Expiration Mechanics (Diaphragm)

Upward movement (diaphragm stops contracting) = Low thoracic volume = High Ppl and Palv (gas going out)

End Expiration

Palv equal to Pm which is equilibrium so (done breathing out)

Pleural Pressure (Ppl) Characteristic

Ppl is always negative (In contrast to Palv who is always positive on inspiration and expiration)

Pneumothorax Definition

Air in the pleural space occurring when Ppl is more positive than Pbs.

Non-Tension Pneumothorax

A two-way hole with diaphragms at the same height and mediastinum at the midline.

Tension Pneumothorax

A one-way hole trapping air in the pleural space.

Tension Pneumothorax Presentation

Mediastinum shifted to the right, collapsed lung, and depressed hemidiaphragm.

Tension Pneumothorax Urgency

An immediate emergency due to air building up close to the heart.

Normal Intrapleural Pressure

3 to 6 cmH₂O

Deep inspiration intrapleural pressure

-50 cmH₂O

Deep exhalation intrapleural pressure

70 to 100 cmH₂O

Lungs (Static Mechanics)

Natural tendency to collapse in alveoli

Chest (Static Mechanics)

Natural tendency to expand

Lungs at resting volume

Functional Resting Capacity (what keeps our lungs open like nitrogen)

Lung recoil vs. chest wall forces

Recoil forces of the lung should equal Distending force of the chest wall

Static forces of the lung

Elastic properties and Surface Tension

Lung Compliance Definition

The change in volume per unit pressure change (less compliance = harder to stretch).

Lung Compliance Formula

Change in volume (L) / change in pressure (cmH₂O).

Normal Lung Compliance

0.1 L/cmH₂O.

Compliance and Distension

CL is decreased the more distended (stretched) the alveoli are.

Overdistension

Increasing pressure without getting a change in volume, which could snap the alveoli.

Compliance and Stretch Relationship

Compliance goes up the more the lungs can stretch (amount of volume) and vice versa, as long as pressure is constant.

Static Compliance (Cstat) Formula

Vt / (Pplat - PEEP)

Static Compliance Normal Value

70 - 100 mL/cmH₂O

Cstat Conditions

Cstat has no resistance and it is when flow is static/still so insp or exp hold (mostly insp hold)

Dynamic Compliance (Cdyn) Usage

Used more often because it incorporates resistance.

Dynamic Compliance (Cdyn) Formula

Vt / (PIP - PEEP)

Cdyn Characteristics

A combination of compliance and resistance.

Dynamic Compliance Normal Value

50 - 80 mL/cmH₂O

Airway Resistance Definition

Opposition to the flow of gases through the airways.

Normal Airway Resistance

0.5 - 2.5 cmH₂O/L/Sec

Airway Resistance (Raw) Formula

(PIP - Pplat) / Flow (V)

Factors affecting Raw

-Airway length (long tube = increased Raw vice versa),

-Radius (a tube ½ = increased Raw by a factor of 16)

-Flow rate (laminar flow = decreased raw and turbulent flow = increased raw)

Hooke's Law (Elastance)

Tendency to return to original resting shape after stretching.

Elastance Formula

Change in P / Change in V.

Elastance and Compliance Relationship

Inverse (lungs with increased compliance have low elastance and vice versa).

Limit of Elastance

When pressure is applied but volume is doesn't increase so the alveoli does not snap back into place

Limit of Elastance Consequence

Alveoli rupture leading to Pneumothorax (COPD patients are prone to this).

Force and Elastic Stretch

If 1 unit of force (P) (like 1 cmH2O) is applied to an elastic body, it will stretch to 1 unit of length (V)

Liquid Molecules Attraction

Mutually attracted to each other and moving freely in all directions when surrounded by liquid molecules.

Surface Tension Definition

In a liquid-gas interface (where liquid & gas touch), the liquid molecules at the surface are attracted to the liquid molecules within the mass is surface tension (so the liquid molecules at the surface attaching to the liquid molecules in the liquid via surface tension)

Surface Tension Measurement

Measured in dynes/cm.

1 dyne/cm Definition

Force necessary to cause a tear 1cm long in the surface layer of a liquid. (The force to separate the liquid molecules at the surface and the liquid molecules in the liquid so to tear the surface tension)

what dynes/cm causes what

Can exert forces in excess of 70 dynes/cm, resulting in complete alveolar collapse.