Cardiopulmonary (Exam 1)
What is the function of ventilation?
The function of ventilation is moving air into and out of the lungs and the gas difference between the environment and the alveoli.
What happens when lung compliance decreases? Increases?
When lung compliance decreases, the stiffness of the lungs increase. (static characteristics.) Making it harder to breathe.
When lung compliance increases, the stiffness of the lungs decrease.
Describe Driving Pressure.
Driving Pressure is the pressure difference between two points in a tube or vessel, (ex. mouth and alveoli.) It is the force of moving gas or fluid through the tube or vessel.
What is Transairway Pressure?
Transairway Pressure is the barometric pressure difference between the mouth pressure (Pm) and the alveolar Pressure (Palv) It represents the driving force that forces gas in and out of the lungs. This represents RAW = Airway Resistance.
What is Transpulmonary Pressure?
Transpulmonary Pressure is the difference between the alveolar pressure and the pleural pressure. It measures Lung Compliance.
What is the function of the phrenic nerves?
The phrenic nerve controls the diaphragm, a muscle located under the lungs. The phrenic nerve signals the diaphragm muscle to contract when a person is about to inhale. When the diaphragm muscle contracts, it moves downward, leaving room for the lungs to expand. This allows air to travel through the nose and mouth before entering the windpipe.
What happens to the diaphragm during inspiration? How does it effect the intrapleural pressures?
During Inspiration, the diaphragm contracts and moves downward, increasing the thoracic volume. The intrapleural and intral-alveolar pressures decrease.
During Inspiration, the intrapleural pressure is less than the barometric pressure, therefore gas moves from the atmosphere into the lungs, until the intrapleural pressure equals the barometric pressure. this is known as end inspiration or pre exhalation.
What happens to the diaphragm during Expiration? How does it effect the intrapleural pressures?
During Expiration the diaphragm relaxes and moves upward. There is a decrease in volume, therefore an increase in intrapleural and intra-alveolar pressures.
During Expiration, the intrapleural pressure is greater then the barometric pressure. Gas moves out of the lungs and into the atmosphere until the intrapleural and the barometric pressures are equal. This is known as end expiration or pre inspiration.
What is normal intrapleural pressure change at rest?
Normal Intrapleural pressure change at rest is 3-6cmH20.
During Inspiration, it decreases 50 cmH20 sub atmospheric pressure.
During Expiration, it increases 70-100 cmH20 above atmospheric pressure.
Describe Positive Pressure Ventilation during Inspiration and Expiration and it's side effects.
Positive Pressure Ventilation is forcing positive air in. During Inspiration, Intra-alveolar and intra-pleural pressures increase above atmospheric pressure and above resting state. The diaphragm then moves downward.
Duing Expiration, the intra-alveolar pressure decreases towards atmospheric level until it equals sub atmospheric pressure. the diaphragm then moves upward to a resting level.q
What is Functional Residual Capacity.
FRC = ERV + RV
(Expiratory Reserve Volume + Residual Volume.)
It is the volume remaining the lungs after the recoil pressure of the lungs and the outward pressure of the chest cancel each other out. It accounts for 40% of total lung capacity.
Define Lung Compliance. (It's Formula, what happens when it increases or decreases.)
Lung Compliance is defined as CL = ΔV / ΔP. It reflects the elastic recoil of the lungs. NORMAL CL is 100 ML OR 0.1 LITERS.
When Lung compliance increases, the lungs accept a greater volume of air pre change in pressure.
When Lung Compliance decreases, the lungs accept less volume of air as pressure change.
Describe Hooke's Law.
Hookes law describes the physical properties of the elastic substance. It describes the lungs ability to go back to its resting state. Elastance is the opposite of compliance, it is the change in pressure/change in volume.
Describe Surface Tension and what reduces it?
Surface tension is the force of liquid gas interface that exist, the liquid gas interface is strongly attracted to liquid moles within the liquid mass. Pulmonary Surfactanct reduces surface tensions, it is measures in dynes per cm.
Describe Laplace's Law.
Laplace's Law describes how the distending pressure of a liquid sphere is influence by the surface tension of the liquid sphere.
- The Distending Pressure of a liquid sphere is directly (equal) proportional to surface tension of the liquid sphere. ex, the more surface tension, the more distending pressure needed to keep the alveoli open.
- The Distending Pressure of a liquid sphere is inversely proportional to the radius of the sphere. meaning, the smaller the radius of the sphere, the more distending pressure needed to keep it open. The bigger the radius, the less distending pressure is needed to keep it open.
What is Pulmonary Surfactant, where is it made?
Pulmonary Surfactant offsets the natural tendency for the smaller alveoli to collapse. It is produced and stored in Type 2 cells. It is made of 90% phospholipid and 10% protein. It has both a hydrophilic and hydrophobic end. It's purpose is to lower surface tension.
What are some causes of pulmonary surfactant deficiency?
Acidosis, PVC, Adult/Infant distress System. Pulmonary Edema, Embolism, Pneumonia, Excessive Pulmonary Hydration and Drowning.
what does hypoxemia involve?
what does hypoxia involve?
Hypoxemia involve (PAO2, PaO2)
Hypoxia involes all three. (PaO2, PAO2, PO2)
Define Dynamic when it refers to the lungs.
Dynamic refers to the study of forces in action. In the lungs it refers to the movement of gas in and out of the lungs and the pressure chances to move the lungs.
Describe Poiseulli's law during inspiration and exhalation.
Poiseulli's law during inspiration states that: intra-plerual pressures decrease from normal resting level which causes the bronchial airways to leghten and increase in diameter. (Passive Dialation)
Poiseulli's law during exhalation states that: intra-pleural pressures increase/ return back to resting state.
How does Poiseulli's Law regard to flow and pressure.
Poiseulli's Law arranged for flow states that flow is directly proportional to the pressure and radius and inversely proportional to the length and viscosity of the gas.
Poiseullis Law arranged for pressure states that if the flow remains constant, then decreasing the radius 1/2 of its previous size requires an increase in pressure 16 times its original level. (As the tube gets smaller, the pressure gets bigger, so it needs more pressure to take in that breath.
Describe Airway Resistance (RAW).
What is normal RAW?
Who are more prone to RAW?
Airway Resistance is defined as the pressure difference between the mouth and the alveoli divided by the flow rate.
Normal Raw is 0.5-1.5 cmH20/1/sec. = Pm - Pav
Describe the two movements of gas going through the bronchial airways, Laminar Flow and Turbulent Flow.
Laminar flow is gas that is streamlined. It contains low flow rates and low pressure gradients. (Normal breathing Flow)
Turbulent Flow is gas molecules that move through the tube more chaotically and in a random manner. (Can be due to bronchial-spasm, inflammation, secretions..)
Describe Time constants and it's effects on regions that have increased RAW and decreased RAW.
Time constants are a product of raw and static compliance. It is defined as the time it takes to inflate the lungs.
- Lung regions that have either increase airway resistance or static lung compliance require more time to inflate
- Lung regions that have decreased airway resistance or static lung compliance require less time to inflate.
How is dynamic compliance different from static compliance?
Static Compliance is determined during a period with no gas flow.
Dynamic compliance is determined during a period with gas flow.
What two parts does normal ventilation consist of?
Inspiration and Expiration.
What does Ventilatory Patterns consist of?
Ventilatory Patterns consist of the Tidal Volume (Vt) ; the Ventilatory Rate (RR) and the relationship between inspiration and expiration. (I:E ratio)
What is Tidal Volume?
Tidal Volume is the volume of air that normally moves in and out of the lungs in a quiet breath. 500 ml. Nomal Vt = 7-9 mL/Kg or 3-4 ml/lb
What is Ventilatory Rate?
Ventilatory Rate is the amount of breath taken per minute. Normally its 12-20 B/M. The normal I:E ratio is a 1:2.
Describe Minute Ventilation. (VE.)
What is the formula?
Minute Ventilation is the total amount of gas moving in and out of the lungs in 1 full minute.
VE = RR x VT
Describe the difference between alveolar ventilation and dead space ventilation.
Alveolar Ventilation is the portion of gas that reaches the alveoli (site of gas exchange) and Dead space ventilation is the portion of gas that does not reach the alveoli.
What are the 3 types of dead space ventilation?
Anatomic, Alveolar, Physiologic.
Describe what AutoPeep is? and its relationship to RAW during rapid RR?
Autopeep is (Positive End Expiratory Pressure.) Peep keeps the alveoli open during exhalation. It's gas trapped in the alveoli at the end of expiration.
It's relationship to RAW during rapid RR is that during rapid RR, a person with small airways and high RAW will make it difficult to fully deflate the lungs During expiration pressure in the lungs will be positive.
PEEP is referred to as air-trapping, intrinsic peep, Occult peep, inadvertent peep, covert peep.
How does autopeep increase WOB (Work of Breathing.)?
Autopeep increases WOB in 2 ways:
1. Patients with a FRC increases. Then airtrapping and alveolar hyperventilation decreases lung compliance, increasing WOB.
2. Diaphragm is pushed down, causing patients inspiration effort less eficient causing an increase in WOB. (ex. lungs are so inflated during exhalation that it's harder to take a fullfilling breath in. Patients have to use accessory muscles to force a breath in.)
What does normal inspiratory effort cause the alveolar pressure to do?
Normal inspiration pressure causes the alveolar to decrease -1-2cmH20 below atmospheric pressure to flow air into the alveoli.
Describe Anatomic Dead Space.
Anatomic Dead Space is the volume of gas in the conducting zone (mouth - terminal bronchioles) it's 1ml/ib or 2.2 Kt of normal body weight.
Describe Alveolar Ventilation.
Alveolar Ventilation is the volume of gas expired from the alveoli to the outside of the body.
Describe Alveolar dead space.
Alveolar dead space is the volume of air in the alveoli that does not partake in gas exchange. The alveolus in ventilated, but not pro-fused with blood flow,
What is physiologic dead space?
physiologic dead space is the sum of anatomic dead space + alveolar dead space.
What is CL = ΔV / ΔP
Lung Compliance Formula. ex.
Patient Plateu = 15
Vt = 500
CL = ΔV / ΔP
500 / 13 = 33.3 ml/cmH20 or 0.033 L/cmH20 (Based on these results lung compliance is NOT normal. It should be 100 ml or 0.1 liters)
What is =
PIP - PlateucmH20 / Volume = ?
RAW. Airway Resistance.
Normal RAW for non intubated patients = 0.5 - 1.5 cmH20
Normal Raw for Intubated patient = 5 -6 cmH20
*Note whether a problem solving question specifies if patient is intubated or not, this matters*
Lets do an example:
- Pip (mouth pressure) = 20
- Plateu = 15
= Flow (V) = 1 l/sec
(20 - 15 ) / 1 / = 5cmH20/1/sec.
( based on these results it is not normal for a patient not on a ventilator. however it is considered normal for a patient intubated on a ventilator.)
RR x Vt = ?
? = ΔPr4
ΔP / ΔV = ?
ΔV / ΔP = ?
Lung Compliance. (CL)
(Vt - Vd) x breaths/min = ?
(450 - 150) x 12 = 3600 ml or 3.6 liters/min ( This represents the amount of gas exchange that is happening.)