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Mech Vent #4
Modes of Mechanical Ventilation
Question | Answer |
---|---|
What type of pressure ventilation involves normal respirations, Chest cuirass, and iron lung? | Negative pressure |
5 examples of positive pressure ventilators are | CMV, A/C, IMV, SIMV, CPAP |
Positive pressure ventilators can be ____ vs ____ controlled | pressure, volume |
There is ____ and ____ modes available for PPV | adaptive, dual |
2 types of non conventional ventilation | HFOV (cpap with a wiggle), APRV (cpap with spontaneous breaths) |
During spontaneous breathing when does pressure equalize? | at end inspiration and end exhalation |
How does PPV create transairway pressure? | by increasing airway opening pressure above alveolar pressure |
PPV generate gas flow, therefore ____ ____, by producing a positive pressure gradient | tidal volume |
2 things to consider when using PPV | alveolar/capillary filling occurs during active phase of inspiration which is usually neg pressure and under PPV, vascular flow can be impeded |
Modes of PPV from the most support to the least support | CMV, A/C, IMV, SIMV, CPAP |
Advantages of volume controlled | Ensures minimal VE |
Disadvantages of volume controlled | pressure variable:barotrauma/volutrauma possible, volume limited by high pressure alarm |
Advantages of pressure limited | less risk of barotrauma d/t set inspiratory pressure |
Disadvantages of pressure controlled | doesnt ensure VE; Vt variable |
What 2 things are variable on pressure controlled vent | volume(dependent on set pressure) and Flow |
4 types of triggers | Time, patient, pressure, flow |
What is the control used to adjust ventilator sensory of patient inspiratory effort called | sensitivity |
What are the 2 types of sensitivity controls? | pressure (ex:IPPB), and Flow |
How does a perssure trigger work? | ventilator senses a drop in pressure below the baseline, senses pt negative inspiratory effort |
Pressure transducers are placed at these 3 locations | proximal airway- at teh wye connector, internally where gas flow leaves the unit, and where exhaled gas leaves the unit |
Which trigger type is more sensitive, pressure or flow? | flow |
How does a flow trigger work? | when a pt initiates a breath base flow returning to the vent is reduced thus triggering inspiration |
Describe Controlled Mandatory Ventilation | Time triggered, machine breath, volume or pressure cycled |
What does CMV control to equal VE? | (Vt or Pressure) + RR=VE |
What are the indications for CMV? | Need to control VE completely; need to control chest expansion completely like with flail chest |
Complications of CMV? | pt is totally vent dependent, alarams are essential, unable to assess weaning and seizures interrupt delivery of breath |
Time/breath/cycle for A/C vent | Patient or Time triggered, machine driven, volume cycled |
Indications for A/C mode | full ventilatory support, need to support high VE with low O2 consumption, sedation after intubation |
Advantages of A/C mode | Decrease WOB(pt trigger only), pt controls RR therefore VE (resp compensation, normalize CO2) |
Complications of A/C mode | hyperventilation(resp alkalosis), pain/anxiety/CNS disease, Biots or Cheyne stokes respirations |
Describe IMV mode | first widely used mode that allowed partial ventilatory support, facilitates weaning, increase muscle strength. Not widely used today |
Complications of IMV | breath stacking(spont effort immediately followed by mechanical breath) which leads to increased PIP, barotrauma, cardiac compromise |
What is baotrauma/volutrauma? | lung injury that occurs from hyperinflation of alveoli past rupture point (PIP>50, Pplat>35) |
SIMV triggers/type of breaths/cycling mechanism | trigger:mandatory(time or pt triggered/assisted), Type:mechanical, assisted, or spontaneous; Cycle:mechanical/assisted(preset Vt or pressure), Spontaneous:pt determines Volume |
What is the synchronization window? | time interval just prior to time triggering in which the ventilator is responsive to the patient's spontaneous breath |
Indications for SIMV | parital vent support, pt can actively participate in VE |
If the set rate is high(8-12) in SIMV mode | can provide total support (SIMV with no spontaneous rate is the same as A/C) |
Setting the rate low (<8) in SIMV: | facilitates weaning, strengthens respiratory muscles, decreases mean airway pressure making spont breaths have a lower peak pressure than mandatory |
Complications of SIMV: | low rate can increase WOB causing muscle fatigue/failure |
What mode of PPV has a positive baseline pressure continuously applied to the circuit and airway during both I and E? | CPAP |
in this mode of PPV the ventilator delivers a time triggerd breath and allows patient to breath at own Vt bw mechanical breaths. | IMV |
In this mode of PPV the ventilator delivers a set Vt or pressure at a time triggered rate but the patient can trigger a mechanical breath above preset rate | A/C |
In this mode of ventilation patient can not trigger mechanical or spontaneous breath so there is no negative deflection on graphics. The pt must be sedated or paralyzed.Not commonly used | CMV |
In order for this mode of PPV to be used the pt must be spontaneously breathing, have adequate lung function to maintain normal PaCO2, and are not at risk for hypoventilation | CPAP |
3 things pressure support does? | augments spontaneous Vt, Decreases spontaneous RR, and reduces patient WOB, Raw |
How does pressure support decrease spontaneous RR? | increased volume decreases need for high RR to achieve required VE, decreases deadspace ventilation |
Desired RR is less than __ | 25 |
What is Vt dependent upon with Pressure support mode? | set inspiratory pressure, lung compliance, and airway resistance |
What makes flow variable in PS? | dependent upon flow needed to maintain pressure plateau |
PS:trigger, breath, cycle | patient triggered, spontaneous, pressure limited, flow cycled |
CPAP with PS is | BiPap |
CPAP with no PS is | CPAP |
Management of PS | begin with 5-10cwp, increase in increments of 3-5cwp |
Titrate PS according to what 3 things? | Spont Vt 5-7ml/kg IBW, RR less than 25, Decrease in WOB |
This is not a “stand alone” mode | PEEP |
Effects if PEEP | recruit alveoli, increase FRC(oxygenation), increase alveolar surface area(gas diffusion), increase compliance, prevent VILI |
Complications of PEEP | cardiac compromise, increase intrathoracic pressure, decrease venous return, decrease CO and BP |
Indications for PEEP | refratory hypoxemia and 5cwp is considered physiologic to replace glottic closure |
PEEP mgmt | 5cwp=physiologic, increase in increments of 3-5cwp while watching BP, decrease to previous level or zero for low BP, treat low BP with vol expansion or vasopressors then increase PEEP again while observing BP |
What is compliance | volume change per unit pressure |
Inverse ratio ventilation is ___ controlled | pressure |
Long I, Short E causes what? | air trapping, auto PEEP and prevents alveolar collapse |
Auto-PEEP= | increased oxygenation, peep effects, increased FRC, PaO2, and surface area |
How does IRV prevent alveolar collapse? | critical opening pressure reduced, pressure needed for ventilation is less, improves ventilation |
Complications of IRV | barotrauma, requires paralysis sedation, cardiovascular compromise similar to PEEP effect |
Mandatory minute ventilation activates when | a pts spont breathing is less than minimum set VE, ventilator increases ventilation |
The method of increased ventilation with MMV varies upon what? | ventilator model(some icrease RR, some Vt, and some PSV) |
What should VE be set to achieve? | satisfactory PaCO2 |
Advantages of MMV | promotes spont breathing, minimal support but protects against hypoventilation and resp acidosis, permits weaning but compensates for apnea |
Disadvantages/complications of MmV | doesnt protect against RSB(deadspace breathing), High RR with low Vt = patient breathing above VE(MMV remains inactive but PaCO2 increases, resp acidosis) |
Describe Pressure control(PCP | Vt variabl, Inspiration begins at preset pressure, Plat is created and maintained for preset I-time, Flow is variable dependent on flow required to maintain pressure plat |
Pressure control generates a ____ flow to increase the airway pressure to a preset pressure limit | high |
When is inspiration terminated in Pressure Control | when the preset I-Time is reached |
Indications fro PC | low lung compliance-high PIP during volume ventilation (PIP > 50, Plat>35); ARDS-ARDS net protocol |
Advantages of PC | PIP is reduced while maintaining adequate oxygenation and ventilation, reduced risk of barotraumas |
Management of PC | Pip is set to achieve a goal Vt, unless pt is allowed to become hypercapnic in the interest of limiting PIP; VT and VE must be carefully monitored |
What is APRV? | airway pressure release ventilation |
What happens during inspiration of APRV | applie positive airway pressure to augment spont breathing (High CPAP level, reduces WOB, Increases MAP to increase O2, allow spont inspiration at any point during the breath-elevated pressure delivery) |
What happens during exhalation with APRV | positive pressure is periodically released to allow exhalation (brief 1-2 seconds), decreases FRC and allows for exhalation and release of CO2 |
APRV is inappropriate for what kind of patients? | those at risk for an inadequate spontaneous RR |
APRV can resemble IRV when | expiratory pressure release time is less than spontaneous effort |
Why is APRV beneficial alternative to IRV | does not require paralytics |
APRV: trigger/limit/cycle | time triggered but pt is allowed to breathe spontaneously at any time; mandatory and spont pressure limited; time cycled d/t preset I-time |
Describe HFOV | reduces risk of lung destruction by keeping alveoli open at constant pressure, oscillates very rapidly (high RR, Hertz, small volumes), early intervention is key! |
Managing oxygenation with HFOV | Mean airway pressure, FiO2, alveolar recruitment |
Managing ventilation with HFOV | amplitude-delta “P”, Hertz, % I time, cuff deflation, permissive hypercapnia |
Amplitude delta “P” | change in stroke volume, force delivered by piston by setting power, CWF-chest wiggle factor |
Hertz | (1 hertz=60rr), set at 3-6 Hz, decrease rate to eliminate CO2 |
% I time determines delivery of | Paw |
Patient care HFOV | Sx PRN, humidity circuit, bronchodilator, sedate or paralyze, pronation, fluid bolus prn, vasopressors, bronchoscopy |
Assesment HFOV | Hr, SpO2, BP, CWF, Auscultate, CXR, ABG |