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69 Cards in this Set
- Front
- Back
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Define plural pressure (Ppl) and give normals at end of E and end of I
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Ppl is the pressure between the potential space of the parietal & visceral pleura;
Normal at end of E: -5 cmH2O Normal at end of I: -10 cmH2O |
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Define Transpulmonary P (Ptp)
a.k.a. alveolar distending P |
transpulmonary P is the P difference between the alveoli & pleural space
This P keeps the alveoli open |
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Define Transthoracic P (Ptt)
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Transthoracic (Ptt) is the P needed to overcome the C of the lungs & chest wall
Ptt = PA - Pbs |
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Define Transairway P (Pta)
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transairway P (Pta) is the P needed to overcome Raw; It creates the flow in the conducting airways;
Pta = Pawo - PA |
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Define Transrespiratory P (Ptr)
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Transrespiratory P (Ptr) is the P required to overcome C and Raw; It is the P required to inflate the lungs during PPV
Ptr = Ptt + Pta Ptt = PA -Pbs Pta = Pawo - PA |
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Briefly explain compliance
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C is the ease w/which a structure distends;
Increased Compliance = structure stretches easier Decreased C = Stiff, resists stretching |
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Briefly explain resistance
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R is the frictional forces associated w/ventilation due to the anatomical structure of the conductive airways, the resistance to gas flow through those airways & the tissue viscous resistance of the lungs & adjacent tissues
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Pressure Equivalents
1 mmHg = ? cmH2O 1 kPa = ? mmHg 1 ATM = ? mmHg |
1 mmHg = 1.36 cmH2O
1 kPa = 7.5 mmHg 1 ATM = 760 mmHg |
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What is the normal C in unintubated patients?
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50 - 170 mL/cmH2O
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AWAhat is the normal C of an intubated patient
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50 - 100 mL/cmH2O
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What is the equation for C?
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C = Change in V/change in P
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Transairway P (Pta) is the P difference between what two areas?
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the mouth and the alveolus
Pta = Pawo - PA |
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How is Raw calculated?
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Raw = PIP - P plateau/ Flow
(L/second) |
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How is Static Compliance calculated?
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Cs = Volume/P plateau
(mL/cmH2O) |
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What is the normal Raw of an unintubated patient?
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<2.4 cmH2O/L/sec
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What is the normal Raw of an intubated patient?
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< 6 cmH2O/L/sec
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How is the amount of pressure lost due to Raw calculated?
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PIP - PA
(determines amt. of P going to airways and amt. of P goint to alveolus) |
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An increase in PIP while the Pstatic remains the same is indicative of what airway characteristic?
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Increased Raw
when there is an increase in Raw, the PIP (amt. of P needed to deliver the Vt) increases |
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As the pressure gradient between PIP & Pstatic increases, what effect does this have?
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the Raw increases as the P gradient between PIP and Pstatic increases
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When there is no change in the P gradient between PIP and Pplateau what does this indicate?
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When there is no change in the P gradient (Pta is constant) this indicates a decrease in compliance
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How is Raw affected when both the PIP and the Pstatic are increased?
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There is no change in Raw because the P gradient is unchanged. (both values increased)
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What factor determines the I:E ratio when setting up a MV
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the Peak flow determines the I:E ratio
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An increased PF has what effect on the I:E ratio?
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an increased PF causes a decreased I:E ratio (shorter Ti and longer Te)
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A decreased PF has what effect on the I:E ratio?
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a decreased Pf causes an Increase in the I:E ratio (longer Ti and shorter Te)
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What does the Pressure Volume Curve Illustrate?
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1. at what P the alveoli are collapsing (use to set P)
2. what part of graph shows the best volume change w/the least amount of P (sloped side) 3. shows if a patient is struggling to breath and shows what PEEP needs to be set at |
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What effect does PEEP have
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PEEP keeps the alveoli from completely collapsing at the end of exhalation
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What is the normal alveolar to arterial oxygen pressure?
How is the normal value calculated according to age? |
Normal P(A-a)O2 is 5 mmHg at age 20
It increases by 4 mmHg per decade |
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In general what is the normal
P(A-a)O2 gradient with MV? |
anything less than 30 is considered normal
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What is the normal P/F ratio?
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80 to 100%
or 0.8 to 1.0 |
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What does the OHDC illustrate?
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The OHDC describes the relationship of O2 P to the Percent of Hb saturated with O2
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What does a right shift of the OHDC indicate?
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Right shift means there is a decreased affinity for O2 (Hb doesn't pick up O2 as well)
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What are some causes of a right shift of the OHDC?
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increase in:
CO2 H+ (decreased pH) temp 2,3 DPG Abnormal Hb |
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Steep portion of the curve
what happens at the tissues |
when small decrease in PaO2 there is a large unloading of O2 from Hb to the tissues (lg. amt. of O2 released from Hb at the tissues w/sm decrease in PO2)
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Flat portion of the curve
Happens at the lungs |
when small decrease in PaO2 there is a small decrease in Hb saturation.; a large decrease in PaO2 doesn't hinder the loading of O2 onto Hb
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How is minute ventilation calculated?
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MV = Vt x RR
Minute ventilation = tidal volume multiplied by Respiratory rate |
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If PaCO2 is increased by 20, what is the expected pH?
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when PaCO2 is increased by 20, then pH decreases by 0.10 unit
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if PaCO2 decreases by 10, what is the expected pH?
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when PaCO2 is decreased by 10, then pH increases by 0.10 unit
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What are the normal parameters when interpretting arterial blood gas levels?
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pH - 7.35 - 7.45
PaCO2 - 35 - 45 HCO3 - 22 - 26 PO2 - 80 - 100 |
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How are time constants calculated?
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1 time constant = time needed to fill to 63% of capacity
TC = R x C |
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Give TC values begining with 1 until TLC can be achieved.
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1 TC = 63%
2 TC = 86% 3 TC = 95% 4 TC = 97% 5 TC = 100% |
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What is the least number of time constants you want to set the ventilator for tidal volume
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at least 3 TC set for mechanical ventilation tidal volume
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In general define time constant
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it is how fast the lung units fill and empty
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Define Baseline pressure
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the P from which inspiration begins and at which expiration ends during MV; a.k.a. expiratory pressure.
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What is the normal baseline pressure
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normal baseline P is atmospheric; Positive P can be applied to increase the baseline above atmospheric
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Define Peak Pressure
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the highest pressure achieved during inspiration on PPV; a.k.a. peak pressure and PIP
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Define Plateau Pressure
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a P measurement taken during PPV after a breath has been delivered to the paitent and begfore E has begun. A condition of no flow exists, reflecting the P in the lungs and patient circuit
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Define Pressure at the End of Exhalation
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air trapped in the lungs at the end of E if not enough time is allowed for E; if no extrinsic PEEP is added and baseline P is > then normal, then air-trapping or auto peep is present
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What is the normal Plateau Pressure range?
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between 30 - 35 cmH20
or < 35 Increased plateau P will cause alveolar injury |
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What is a single circuit ventilator?
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Gas powers the ventilator and goes to patient
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What is a double circuit ventilator?
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Gas powers the ventilator and the goes & powers something else (e.g. bellows) and then that ventilates the patient
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Define Intelligent Ventilators
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Has microprocessor and uses feedback to adjust to patient needs
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Define Unintelligent Ventilator
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Doesn't read any feedback; Does only what it is set to do
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What is the equation of motion
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Pmus + Pvent = V/C + (Raw x V)
Work = Load |
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What is Triggering?
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Triggering is what starts Inspiration
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What is Cycling?
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Cycling is what starts/ends Exhalation
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Define Triggering Mechanism
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It is what starts inspiration
(e,g, time, patient, flow, pressure) |
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Define Cycling Mechanism
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It is what ends inspiration or starts expiration.
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How are all infant ventilators set up to deliver oxygen
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All infant ventilators are pressure limited and time cycled using PCV
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What are some reasons that the delivered volume is different from the set volume?
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1. Tubing/System leak (a leak will cause PIP & MV to decrease)
2. Tube Compressibility/Compliance |
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What is the most common cycling mechanism when using PS mode?
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Flow cycling is the most common cycling mechanism when using PS
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In order for PS to be active, what must be present
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the patient must be actively breathing in order for Pressure Support to be affective
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Flow triggering has what type of effect on WOB
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Flow triggering decreases the WOB
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What is the difference between Hypoxemic RF and Hypercapnic RF?
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In hypoxemic RF, there is low PaO2 while the PaCO2 is normal or low which means pt is able to ventilate, but not oxygenate
In hypercapnic RF, there is a high PaCO2 and hypoxemia is usually present as well, but the pt is unable to sustain adequate ventilation |
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What are some pathological conditions that can cause an increase in the PIP?
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bronchospasm, retained secretions, edema, CHF, ARDS, Fibrosis, pneumothorax, atelectasis, pleural effusion
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What are some pathological conditions that can cause an increase in the Pstatic?
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CHF, ARDS, Pleural effusion, pneumothorax, atelectasis
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What is the normal P/F ratio?
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80/.21 = 375
100/.21 = 475 Normal P/F ration 375-475 |
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What is the Equation of Motion
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Muscle Pressure + Vent. P =
Elastic recoil P + Flow Resistance P |
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Give the Equation for the Equation of Motion
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Pmus + Ptr = V/C + (Raw x V)
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What is the equation
for tidal volume |
Flow(Volume/Time)
x Inspiratory time = Tidal Volume |
