O2 Therapy + MV - Exam 2 Flashcards
What is low-flow oxygenation?
Oxygenation that has variable air entrainment
-Patient breath is a combined mix of air and oxygen
What affects oxygen delivery in low-flow oxygenation?
- reservoir
-nasopharynx and oropharynx are anatomic reservoirs - flow rate
- ventilation pattern of patient
-increased TV and RR reduces inspired FiO2 - fit
Nasal cannula (Liter flow, FiO2%) Low/High flow?
1-6L
FiO2 - 4% increase for each 1L
Low flow
Simple mask (Liter flow, FiO2%) Low/high flow?
No reservoir
Liter flow 5-8L
FiO2 - 35-60%
-FiO2 DECREASES with MV increase
Low flow
Partial rebreather (Liter flow, FiO2%) Low/high flow?
Has reservoir, No valve=150mL anatomic dead space -rebreathed
10L + Flow
FiO2 60-80%
Low flow
Non-rebreathing mask (Liter flow, FiO2%) Low/high flow?
Unidirectional valve + reservoir bag (should be 1/3-1/2 full with 8-15L/min)
10L Flow=FiO2 100%
Low flow
Face tent (liter flow, FiO2%) Low/high flow?
4-8L flow
FiO2 30-55%
Low flow
-good for eyes, post-nasal, and plastic cases
T-piece/trach mask (liter flow, FiO2%) low/high flow?
4-8L/min with FiO2 30-55%
-BYPASSES NASO+OROPHARYNX SO NO AIR ENTRAINMENT
-could decrease FiO2 without a reservoir
Low flow
What is a high flow system?
-Flow rate and reservoir > MV to supply the precise O2 and air mix
-Flow is specific and consistent FiO2 REGARDLESS of MV
FiO2% ranges from 24-50%
-larger port=less FiO2
-higher flow does NOT increase FiO2
Oxygen administration is contraindicated in which patient population?
COPD
-loss of hypoxic drive
What is absorption atelectasis?
Nitrogen washout in the alveoli causing alveolar collapse (atelectasis)
What is oxygen toxicity?
High conc O2 (>50%) given >48hr
-removing hypoxic drive(COPD!)
-use minimal FiO2 on venturi mask, goal is SaO2 88-92%
-increase free radical formation causing damaged membranes, proteins, and lung structures**
What is retinopathy of prematurity?
Retinopathy of Prematurity; blindness occurring in premature infants and newborns as a result of high PaO2, not high FiO2
Three indications for mechanical ventilation?
Acute hypoventilation/apnea
High V/Q
Low V/Q
What are causes of VALI? (Ventilator associated lung injury?)
- Volutrauma
-Overextension of alveoli (too much TV) - Barotrauma
-Positive pressure effects such as pneumothorax (too much PEEP) - Atelectrauma
-Collapse and reinflation of alveoli (not enough PEEP/too much FiO2) - Biotrauma
-Release of inflammatory mediators (disease process)
How to prevent VALI from barotrauma?
-Peep < 15 cmH2O
-PEEP = BMI x 0.3
Pt is 80kg and 6’1. 6’1=73in=185.42cm=1.85m
(80/3.438) = 23.3 BMI
PEEP = 6.98cmH2O
What is tidal volume?
Vt is volume per breath
What is minute ventilation?
MV = Vt x RR
The volume of gas inhaled and exhaled in a minute
What is laminar flow?
Streamlined flow: Molecular movement when there is little friction
What is turbulent flow?
Chaotic and Random flow: Molecular movement with friction (increased resistance)
What is peak flow?
Velocity at which gas is delivered to patient
50-80 L/min
What is peak pressure?
Highest pressure reached during ventilator breath
Spontaneous breath: Patient effort
MV: Inspiratory pressure + inspiratory flow rate
Increased by PEEP
Volume Control
Preset TV, RR, I:E ratio
PIP can change
-pressure and volume limit usually
-Inspiratory pressure is 10-15 cmH2O higher than peak pressure of normal breath
higher pressure for same ventilation as PCV
Controlled Ventilation
A type of ventilation in which the anesthetist controls the respiratory rate, the tidal volume, and the peak inspiratory pressure. In this type of ventilation, the patient does not make spontaneous respiratory efforts.
assist control ventilation
For spontaneous breathers:
-DETECTED breath receives preset VOLUME, WILL give breath on TIMER if pt is apneic
-can induce breath stacking and resp alk
Preset: TV, RR, Insp. Flow, PEEP, FiO2
PIP: VARIABLE
intermittent mandatory ventilation (IMV)
Gives mandatory breaths and if pt takes spont breaths they are not supported by machine, but can happen based on patient’s own ability
-TV and RR set but if pt breathes spont they can increase MV bc Vt is variable if spont
-PIP variable
SIMV
Must set pressure support for spontaneous breaths, delivers set volume
PIP variable
Same as IMV, however it will not deliver a mandatory breath on top of a spontaneous breath-weaning mode
-Senses mandatory breaths and synchronizes, still delivers set amount of TV/ MV while avoiding bucking/stacking
Pressure control
Preset RR, Insp. flow, PIP, PEEP, FiO2, I:E ratio
VARIABLE TV
Ventilation is delivered until the set peak pressure is reached
-better ventilation at lower pressures
-good for lap + robot cases, COPD, one lung
What is protective ventilation?
6-8 mL/kg(IBW) TV
14-16 RR
15-20 PEEP
With pressure control-less barotrauma
reduces sheer pressure, optimized recruitment, higher mean airway pressure for better exchange, helps wean
-better post heart and post (non obese) abdom cases
What is pressure control inverse ratio ventilation
Longer inspiratory period than expiratory period
airway pressure release ventilation (APRV)
mode of mechanical ventilation that allows unrestricted, spontaneous breaths throughout the ventilatory cycle
-inverse IE ratio, 2:1
-on inspiration the patient receives a preset level of continuous positive airway pressure, and pressure is periodically released through exhalation to aid expansion
-avoid in pt with increased resistance and air trapping
Pressure control volume guarantee/pressure-regulated volume control (PRVC)
TV consistent
Inspiratory pressure variable, but programmed by anesthetist
What is SIMV/PSV modes? (SIMV with pressure support)
Mandatory volume and respiratory rate, but also supports spontaneous breath with pressure
What is pressure support with protection? (PSV-PRO)
-lets pt spont breathe but switches to ACV or SIMV if apneic (10-30s) and switches back if they breathe again
-Preset: FiO2 + PEEP, PIP is capped
-Variable: Vt, insp flow rate, RR, PIP (adjusts to overcome resistance)
-good for maintenance and emergence bc supports EtCO2 and MV while preventing barotrauma + WOB
-senses pt’s effort and delivers pressure breath with every respiration to increase Vt
-often used as add on for ACV or SIMV
ARMS methods?***
CPAP after surgery
-sustained inflation: 50-90sec to PIP of 40cmH20
-incremental increasing of PEEP: stepwise manner, 4-20cmH2O
PEEP during surgery, ARMS Q 1hr or if pO2 drops**
What is PEEP?
Increases end-expiratory airway pressure to a value higher than atmospheric to keep alveoli inflated
When is PEEP contraindicated?
COPD
What PEEP settings cause barotrauma?
PEEP > 10 cmH2O
Mean airway pressure > 30 cmH2O
PIP > 50 CMH2O
How does PEEP affect the CV and neurologic systems?
Decreases BP
Increases ICP
What is CPAP? BiPaP? Indications?
CPAP: Positive pressure with inspiration
Spontaneous breathing
BiPAP: Positive pressure on inspiration and expiration
Spontaneous breathing
Indications: COPD with hypercapnia, cardiogenic pulmonary edema, hypercapnic/hypoxic respiratory failure
What causes increased compliance?
Emphysema, COPD
What causes decreased compliance?
Pneumothorax, CHF, atelectasis, abdominal distention, pleural effusion
How to set RR for SIMV?
Set RR to create 80% of minute ventilation demands
What is plateau pressure?
Pressure applied to the small airways and alveoli
-Measured by end-inspiration hold of 0.5-1 second
35 cmH2O < barotrauma
Peak flow rate for most patients
60 L/min
Pressure trigger sensitivity for most patients
-1 to -3 cmH2O
PSV
Preset PEEP
Preset FiO2
VARIABLE TV
Preset PAP
Delivers supportive pressure on inspiration until flow reaches a set level (generally 25% of peak flow)
WOB is inversely proportional to level of pressure support and flow rate
Normal MV
5-7L/min
How can you estimate the correct level of PEEP usage?
Lower inflection point + 2 cmH20
Definition of ARDS (numbers)
PaO2/FiO2 < 200
How to prevent VALI from volutrauma?
Use VT 6-7 mLs/kg IBW
How to prevent VALI from atelectrauma?
-Minimize FiO2 30-40%
-Low I:E ratio 1:1.5
-Use ARMS
VCV is best used on which pts:
Set MV (RR and Vt) meets the desired goal for body
-medically paralyzed
-sedated
-coma
-lack of pt incentive to increase MV
PCV is best used on which pts?
Improves compliance
-preg, laproscopic cases, obese, ARDS, system leak or LMA
Controls PIP to avoid risk of barotrauma
-LMA use, emphysema, neonates
Better Vt for less pressure
-laproscopic cases
SIMV PSV
-volume controlled
-pressure support can be added to help pt with any spont breaths, weaning mode
SIMV PC
-pressure controlled
-pressure support can be added to help pt with any spont breaths, weaning mode
PC VG
-pressure set, Vt set(MV)
-PIP changes (if compliance/ resistance changes) within range of PMax to achieve Vt with minimal pressure
-can be added on to SIMV, AC, CMV, and PSV
PSV PRO ideal pt
LMA
-protects from apnea, helps reduce WOB, gives pressure when pt attempts breath
CPAP + PSV
-gives constant support pressure once vent senses insp effort
-spont breathing that happens is shown via color change on wave
If on NC @ 4L/min, what is FiO2?
~37%
4*L/min +21 =FiO2
What is FiO2 of 2L/min NC
29%
FiO2=21+(4*L/min)
Venturi mask
good for:
-pt who need minimal FiO2 but need to maintain hypoxic drive
-pt with increased MV and abnormal RR needing predictable/consistent FiO2
-uses low flow O2 with entrained RA and Bernoulli principle to cause high escape velocity
Using venturi mask with an aerosol on an asthmatic pt can cause:
bronchospasm
HFNC
-gives between 21-100% FiO2
-humidified
-flow rate ~ 50-60L/min
-greater control over variables
HF Mask + T Piece w/ Nebs
-used when FiO2 must be >40%
-max flow 14-16L/min
-Higher FiO2 uses less air entrainment
Herbicide poisoning or bleomycin (cancer drug/abx) can cause which problems if given with O2?
-ARDS, pulm toxicity
1 effect on PaO2=
FiO2
3 phase variables of mech vent:
Trigger- initiates breath
Limit- governs the gas delivery
Cycle- initiates expiration
What do loops monitor?
-Vt
-Inspiratory flow
-Expiratory flow
-Triggering
-Compliance and Resistance
Flow Volume Loop
-What is measured here
Expiration
Flow Volume Loop
-What is measured here
Flattened Inspiratory flow curve
Flow Volume Loop
-What is measured here
Gas Trapping
-flow curve isn’t returning to 0
Flow Volume Loop
-What is measured here
Inspiration
Flow Volume Loop
-What is measured here
Reduced peak inspriatory flow rate
Flow Volume Loop
-What is measured here?
Expiratory flow is “scooped out”
Flow Volume Loop
-What is happening in this?
-What can you do?
Obstructive lung disease in a MV pt in a flow volume loop(COPD)
-characteristic scooped expiratory flow
-increase I:E ratio to 1:3
What is this loop showing?
Normal MV F/V loop
What is this loop showing?
Circuit leak in a MV F/V loop
What is this loop showing?
Fixed obstruction of large airway or main bronchus in a MV F/V loop
What is this loop showing?
Obstructive airway disease in a MV F/V loop
What is this loop showing?
Obstructive airway disease with air trapping in MV F/V loop
What is this loop showing?
Reduced lung volume but preserved compliance in MV F/V loop
What is this loop showing?
Restrictive lung disease showing DECREASED COMPLIANCE in MV F/V loop
-pulm fibrosis
What is this loop showing?
Secretions in a MV F/V loop
What is this loop showing?
Mixed reactive and obstructive lung disease in a MV F/V loop
In this F/V loop which is measured at the X, compliance or resistance?
lung compliance
In this F/V loop which is measured at the X, compliance or resistance?
resistance
What kind of loop is this, and what mode is the vent in?
Pressure/Volume loop
-PCV
Explain what is happening here
-Pressure volume loop
-Vent mode: VCV
-Shows the patient is receiving increasingly higher PIP to achieve a certain volume
-BEAKING
-diminishing volume return from added pressure overdistending alveoli
-DECREASING COMPLIANCE
If your pressure-volume curve shows the circuit is measuring a PEEP of 8cmH2O but you set the PEEP to 5cmH2O, what could be happening?
Set 5 PEEP is extrinsic so 3 of that 8 is intrinsic
-auto PEEP from air trapping, breath stacking?
WOB (elastic work + resistive work) =
WOB = pressure x volume
(elastic work + resistive inspiratory work)
Increase in convexity of inspiratory loop is r/t which lung pathology?
COPD
-inspiration is wider, overcoming more resistance
During VCV your P/V loop has this shape, what is most appropriate next step??
Switch to PCV, too much pressure could lead to barotrauma
Mean airway pressure (Paw) depends on 5 things:
-PIP
-PEEP
-RR
-I time
-flow
Ppeak vs PIP=
PPeak is peak airway pressure, measured at end EXPIRATION
-sum of resistive pressure, elastic pressure and PEEP(intrinsic too)
PIP is peak inspiratory pressure, measured at end
What is this loop showing, what conditions could contribute?
-P/V loop
-DECREASING COMPLIANCE
-ARDS, CHF, Atelectasis
What is this loop showing, what conditions could contribute?
-p/v loop
-INCREASING compliance
-Emphysema, surfactant therapy
Giving PEEP to a pt with COPD can cause what?
worsening shunt
-COPD pts already have a physiological shunt, PEEP worsens the oxygenation despite better vascular perfusion
What is FiO2 (Fraction of Inspired O2)
Concentration of O2 in a mixture
What is Tidal Volume and what is the typical range?
(TV/Vt) - Amount of vol given per breath, measured in mL
6-12 mL/kg - Normal Range
4-? mL/kg - Protective Measures
What is Minute Ventilation?
Vol of gas exchange per min = Tidal vol (Vt) x Respiratory Rate (RR)
Define PEEP
Positive End Expiratory Phase
Purpose: Maintains Pos Press in lungs; during exh pat doesn’t completely exh,
WHY? Keeps alveoli open improving gas distribution
What is Maximum Pressure (Pmax) and the typical ranges?
What can happen if this is not controlled?
Max lung pressure provider determines is safe
12-100 cmH20 to prevent barotrauma
What is Peak Airway Pressure (Ppeak) and what is it dependent on?
Total press needed to deliver Tidal Volume (Vt)
Dependent on Airway Resistance, Lung Compliance, and Chest Wall factors aka (PIP)
PIP = PEEP + Set insp. pressure
What is Inspiratory Time (Tinsp) and the typical ranges?
Time duration (s) of inspiratory phase of mandatory breath
1.7-2s - Adult (corresponds w/ 1:E 1:2)
1.2s - Peds
What is Flow Trigger and what are the typical ranges?
Amount of pt effort (flow) required to trigger a breath; syncs vent when pt inits breath.
2 L/min - Adult
1 L/min - Peds
0.4 L/min - Neonates
STAR What can be used as a flow trigger?
Flow, time, pressure, or vol
Insert pic from PPT “Hi its me”
High vs Low trigger sensitivities? What happens when it’s too low?
High = more effort
Low = less effort, too low, surgeon can trigger
Note: Defaults on bot of monitor can change per vent mode
What is a trigger window and how is it used?
% of end-expiratory time pt can trigger a mechanical breath
-if vent senses pt insp effort in trigger window, it delivers the next vol, press, or PCV-VG breath with insp time on vent
-if no effort, vent gives normal preset breath
-breaths out of the TW are pressure supported
????? Range: 0 = 80%, N2 = 25%
STAR I:E Ratio
Length of insp period vs. exp period
-Compromise bet ventilation and oxygenation
1:2 = normal - exp time is 2 times longer than insp time
1:3 = COPD/Asthma, reduces air trapping, more time to get vol out
What is PIP?
Peak Inspiratory Pressure
-highest pressure measured in respiratory cycle; total inspiratory work by ventilator;
-indicator of dynamic compliance
-generated by vent ot overcome airway and alveolar resitance
(res x flow) + (elastance of resp syst x TV) + (PEEP)
Kink in the circuit or OETT, Laryngospasm or bronchospasm can cause what w.r.t PIP and plateau?
High PIP normal plateau = elevated resistance
Auto PEEP, right mainstem intubation, or atelectasis can cause what w.r.t PIP and plateau?
High PIP high plateau = issue with compliance
(+/- resistance)
What are the trigger variables of the respiratory cycle and what are they based on?
Time, Pressure, Flow, Volume
Based on Patient
What are the target variables of the respiratory cycle and what can they effect?
Pressure, Flow, Volume
Can prevent risks to pt:
-excessive airway pressures or Vts?
Does not cause an end to insp but causes a ceiling effect
T or F: Exhalation is passive
True
What is Atelectasis and how quickly does it typically take to develop?
Collapse of lung tissue with loss of volume
2-3min after start of surgery
What is a Vital Capacity Maneuver and what does it do?
Vent mimicks provider manually bagging
-Gives 40cmH20 for 30-60s
What is a Cycling Maneuver?
programmable steps to allow inc and dec of PEEP during mech vent
- Looks like stairs on screen
CPAP def and range?
Restores and maintains FRC - improving oxygenation
lung recruitment maneuver
5-10cmH20
PEEP causes the baseline end expiratory pressure to shift in which direction?
Right
Physiologic PEEP vs Therapeutic PEEP values
5 cmH20 - Phys (intrinsic)
5-30 cmH20 - Ther (extrinsic)
What are some complications of PEEP?
-Decreased venous return
-Barotrauma
-Increased ICP
-Alterations in kidney function d/t decreased renal perfusion
BiPAP and ranges?
IPAP (insp) 8-10 cmH20 start, 20 cmH20 max
EPAP (exp) 3-5 cmH20 start, 10 cmH20 max
-
Successful NPPV should decrease RR and PaCO2 by how much?
> 8 cmH20; correct respiratory acidosis
What is an advantage of adjunct vent over invasive vent
manages pulmonary insufficiency from COPD, pulmonary edema, or respiratory failure.
What is a disadvantage of adjunct vent
Increased aspiration risk
Contraindications with adjunct vent
-Hemodynamic instability
-acute MI
-dysrhythmias
-recent GI surgery
What can trigger the High Airway Pressure alarm?
-Plateau pressure (static) above threshold
-Peak inspiratory pressure (dynamic) above threshold
-can show resistance + compliance
-increased airway resistance, decreased compliance
What can trigger the Continuous Pressure Alarm and what are the causes?
-Pressure > 10 cmH20 for longer than 15s
-Gas is unable to exit the sys
Causes:
-vent pressure relief valve stuck
-O2 flush valve activated
-APL closed
-The scavenging sys is obstructed
What can the sub-atmospheric alarm
Pressure in circuit is negative
-pt going towards pt? inspiration?
What can cause the Low-pressure alarm, what is the threshold time, and how do you prevent false negatives
-Circuit does not reach its min threshold within specific per of time
-Threshold is usually 15s
-Prevent false neg by setting pressure limit to just under patients peak inspiratory pressure
Hypoxemia definition
low conc of oxygen in blood
PaO2 < 80 mmHg
Can cause Hypoxia
Define Arterial Oxygen (PaO2)
Partial Pressure of O2 in arterial blood
N = 75-100 (correlates w/ SpO2 90-100%)
Define Alveolar oxygen (PAO2)
Partial Pressure of O2 of the alveoli
N= = 60-70 ~ 90-100%
Define Arterial oxygen saturation (SaO2)
% of hemoglobin binding sites in the blood that are carrying O2
A:A Gradient
PAO2 - PaO2
N = 15mmHg
What can A:A gradient tell you?
if UP, can be fixed w/ supp O2
-VQ mismatch (COPD)
-Difussion impairment (fibrosis)
-shunting
O2 Therapy Indications
MV > flowrate, pt is inspiring more RA ??????
Low Flow vs High Flow
Low Flow (variable perf)
High Flow (fixed perf)
What is the average adult inspiratory flow rate?
20-35 L/min
Relationship between Low Flow and minute ventilation
when min ventiliation exceeds the flow rate, more room air is inspired
Relationship between High Flow and minute ventiliation
Provides constant and precise FiO2 INDEPENDENT of the patient’s minute ventilation.
Relationship between High Flow and entrainment port
Size of entrainment port determines FiO2, varies 24-50%
Larger port -> more room air entrained -> lower FIO2
What does the actual conc of FiO2 depend on for Low Flow
-Reservoir
-O2 Flow Rate
-Pt Vent pattern
-Proper Fit
What are the diff types of Low Flow
Nasal Cannula
Simple Face Mask
Nonrebreathing Mask
Partial Rebreathing Mask
Face Tent
Trach Mask
What are the diff types of High Flow
Venturi Mask
Masks & T-pieces w/ nebulizers (14-16 L/min)
Nasal Cannula high flow (50-60 L/min = 21-100% O2)
Relationship between FiO2 and minute ventilation for a nasal cannula low flow
FiO2 decs as Min Vent incs (RR X TV)
How much flow can a simple face mask provide and what is the min rate and whY?
35-60% FiO2 with 5-8 L/min flow
5 L/min min to avoid rebreathing of CO2
For a Nonrebreathing Mask, what flow is required to get close to 100% FiO2 inhalation?
10 L/min
For the nonrebreathing mask reservoir, how much flow would correspond to the bag looking ~1/3 to 1/2 full
15-18 L/min
Describe a Partial Rebreathing Mask and
-Valveless system w/ reservoir bag, 150 mL of exhaled gas + O2 makes anatomic dead space
-O2 flow must be > 5 L/min
Define Trach mask and what it can cause when an insufficient reservoir is used?
-Like reg mask, but bypassing of the nasopharynx and oropharynx. Does not allow for air entrainment
-Insufficient reservoir can cause a decrease in FiO2
