ventilator review

Ventilator Review

Indications

• Prophylactically (neuromuscular, impending failure, pre-op, post op)

• Airway protection (sedated, stroke, trauma, drug OD)

• Ventilatory failure (pH less than 7.25, CO2>50)• Shunts/oxygenation failure

Impending Ventilatory Failure

• Pt maintains marginally acceptable blood gas values at the expense of significant increased WOB.

• Progressive acidosis and hypoventilation ensue.

Severe Hypoxemia

• Pa02 < 60 mm Hg on Fi02 of 50% or greater.

Prophylactic Ventilatory Support

• Risk of pulmonary complications

• Reduce hypoxia of major body organs

• Reduce cardiopulmonary stress

Initial Settings• Generic startup:

– AC or SIMV modes– PC, VC or PRVC– FIO2 40-60%– Rate 8-12– VT 6-8 ml/kg or PC 15-25 cmH2O– Flow 40-60L, I-time 0.8-1.25– Sensitivity 1-3 flow or pressure– PEEP 0-5– Rise time 50%, 0.2-0.4 seconds

Combinations

• AC-PC• AC-VC• AC-PRVC• SIMV-VC (PS, TC, VS)• SIMV-PC (PS, TC, VS)• SIMV-PRVC (PS, TC, VS)• Spontaneous (PS, TC,

VS, PAV)

• APRV• HFOV• HFPV• HFJV

Settings/Monitored Data• PEEP• FIO2• I-time• Flow• Sensitivity• Rate• Mode• Breath Type• VT• Pressure limit• Rise time• Pressure Support• Volume Support• Tubing Compensation

• MAP• PIP• Total rate• Minute Ventilation• Plateau pressure• Dynamic/static

compliance• WOB, Time constant• Spontaneous/mech

Volume

Initial Setup

• Acute air trapping (Asthma/COPD exacerbation) Restrictive disease (ARDS, PN, Pulmonary fibrosis)– AC or SIMV– VC with lower VT 3-5 ml/kg with rate 15-25 OR PC

15-25 with rate 15-25 OR PRVC low VT range– FIO2 depending on previous ABG/FIO2 setting– IT 0.7-0.9, Flow 60L, achieve appropriate I:E ratio

Initial Setup• If you have a ABG prior to startup, adapt initial settings

per blood gas and prior device• Ex: if patient has extreme respiratory/met acidosis:

hyperventilate patient if patient was actively breathing prior to being on vent, if patient apneic, then use normal vent settings

• Use PEEP for patients with shunts, pulmonary edema• Suggest sedation for initial ventilator stabilization

(Versed, Ativan, Deprivan, Fentanyl, Morphine, Precedex…)

Alarms

• High PIP: 10-15 above (observed pressure)• Low PIP: 5 below (observed pressure)• High rate: 10-15 above total rate• Ve: 2-3 L above/below• VT: 200-100 above/below• Apnea alarms 20 seconds• ALWAYS READJUST ALARMS PER PT CHANGES

OR VENT CHANGES

MODES• AC, SIMV, CPAP/Spontaneous• AC all breaths are mechanical, patient can

trigger a breath only, but machine will complete the breath for the patient

• SIMV both mechanical and spontaneous breaths, must calculate spontaneous VT, support Spont breath with PSV, VS or TC

• CPAP all breaths are spontaneous

Settings Review• Trigger: What begins inspiration, either time,

flow or pressure; or via NAVA. The time applies to non patient triggered breaths. Control trigger by setting sensitivity

• Set sensitivity 1-3. If the sensitivity is set >3 may lead to difficulty triggering breath on and induce WOB, if set to low may cause auto-triggering

• Set in all modes (including CPAP, PSV still needs a trigger!)

• Assess triggering by looking at pressure-time graph or pressure-volume loop

Work to Trigger

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Adjust sensitivity per patients ability, missed triggers will lead to asynchrony

Assisted Breath

Inspiration

Expiration

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Assisted Breath

VT Clockwise to Counterclockwise

Settings Review• Cycle: This is what cycles the breath off. Either flow,

pressure or volume. Pressure and volume limits are the most common

• Volume: Set appropriate per patients size. If patient has restrictive lungs or is air trapping severely, use 3-5 ml/kg range otherwise 6-8

• Set in VC and PRVC. Too much volume can cause volutrauma/barotrauma

• Assess with Volume-time or Pressure-volume graphic

Setting Review

• Volume control used to set a consistent minute ventilation.

• In VC you set the VT, flow and flow pattern. The pressure and I-time are variable

• On PRVC the volume is only targeted not guaranteed, will fluctuate with changing breathing patterns. You set target VT, I-time, pressure limit and rise time.

PV loop

• Note over distention

• Patient triggers• Asynchrony• RAW

Pressure-Volume Loop Changes

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The pressure-volume loop changes, flattening out and moving to the right. What could cause this to happen?

Changes in Compliances

Indicates a drop in compliance (higher pressure for the same volume)

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Did anybody say decrease in compliance? The difference between the white arrow and the red arrow represents a change in compliance as indicated by an increase in pressure without a corresponding increase in tidal volume.

Setting Review

• Pressure Limit: Set 15-25, increase to increase VT, decrease to lower VT

• Set in PRVC and Pressure control but…• All breath types have pressure limits set in the

alarms, in the alarm setting, the high pressure alarm becomes the pop-off, patient will not be able to exceed this level. This is why it is important to set alarms appropiately.

Time

Minimal Pressure Overshoot

Pressure Relief

Slow rise Moderate rise Fast rise

P

V.

Flow Acceleration PercentAKA: Rise Time

Pressure time graph

• Used to assess patient triggering• Used to assess inadequate flow rate/double

breaths• Assess level of PEEP• Assess rise time• Assess Plat time

Setting Review

• Generally Pressure control is used for patients with restrictive disease, but can be used with any patient

• Helps with patients asynchrony because patient dictates their own flow pattern.

• In PC, you set Pressure limit, I-time and rise time. Volume and flow are variable

• Pressure limited, time cycled

Ventilator Review

• MODES:• AC: start with this mode if patient is apneic or if

patient’s spontaneous breaths are inadequate or erratic. Patient can trigger breaths but machine will complete the breath at preset limits

• SIMV: May start with this mode on any patient who is apneic if you suspect he/she will regain spontaneous breathing. Otherwise, use only if spontaneous breaths are adequate. Must set a PSV in this mode or VS or TC

Ventilator Review

• CPAP/Spontaneous: May start for Type I failure, patient must have ability to breathe spontaneously without much need for ventilatory support. Must have a PSV or ATC or VS

• PRVC: duel mode, set in either AC or SIMV mode. Set pressure limit, target VT…Does not work well with erratic breathing patterns

PSV

• PSV only applies to spontaneous inspiratory breaths, used to augment spontaneous VT, set to achieve spontaneous VT of 5-7ml/KG, set above measured RAW

• Start with a PSV of about 6-10, titrate or increase as needed. PSV max = 20-25

• Pressure limited, patient cycled, set sensitivity and rise time, e-sens

Pressure Support Ventilation - PSV

• Applies a preset pressure plateau to the patient’s airway for the duration of spontaneous breathing.

• Used only in ventilator modes that allow for spontaneous breathing

Pressure Support Ventilation - PSV

• Patient has control over– Tidal Volume– Inspiratory Time– RR

– What is the cycling mechanism for Pressure supported breaths?

Ventilator Review

• APRV: for restrictive lungs only, spontaneously breathing

• HFOV: for restrictive lungs only, sedate/paralyze.

• ASV: used as a single mode, from start to finish, not for ARDS or neurological breathing patterns

Ventilator Review

• Flow: Set only in Volume control. When set use either constant or decelerating patterns. Increased flow= decreased I-time. Give patients with COPD increased flows to meet demands and give long E-time. Increase when you increase VT, or change flow pattern

• I-time: Set in PRVC, PCV. Increase or decrease to achieve appropriate I:E, increased rates=decreased I-time. Inverse used for restrictive diseases to increase oxygenation

Setting Flow• The easiest rule of thumb to follow is that a patient

requires a peak flow roughly four times that of the minute ventilation (if the MV is 15 liters, the patient requires a PF of >60 liters). However if the patient is breathing spontaneously, then bedside adjustment is required to ensure that flow matches patient efforts. The peak flow should be set slightly higher if a decelerating waveform pattern is being used, and, in particular, those with airflow obstruction

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A higher expiratory flow rate and a decreased expiratory time denote a lower expiratory resistance. A decrease in expiratory resistance may also be observed after the patient receives a bronchodilator (e.g. MDI or aerosolized neb tx). Monitoring the duration of the therapy’s effect can help determine the indicated frequency of therapy.

Flow Patterns• Constant/Square:

– Causes lower I-time, less MAP, higher PIP– Only set in VC– Can increase oxygenation– Generally uncomfortable for your patients

Flow Patterns• Ramp

– Can be set in volume, automatic pattern in PC– Will increase MAP, and prolong I-time– When switching from constant to ramp, you may

have to increase flow to maintain same I-time, I:E ratio

Pressure time graph

• Used to assess patient triggering• Used to assess inadequate flow rate/double

breaths• Assess level of PEEP• Assess rise time• Assess Plat time

Flow vs.Time Curve

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Constant Flow Descending Ramp

Flow-Time Curve

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Insp. Pause

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Patient / Ventilator SynchronyVolume Ventilation Delivering a Preset Flow and Volume

Adequate Flow

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What options do we have?

Air Starvation

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Patient / Ventilator SynchronyThe Patient Is Out breathing the Set Flow

What we see here is a patient’s inspiratory flow demand greater than the peak flow set on the ventilator, which can lead to patient/ventilator dysynchrony. What are we going to do to amend this situation?

Humidification• The gas delivered to patient during mechanical ventilation should

be filtered, humidified, and heated• Heated humidifier (requires heated circuit, delivers 100% RH) or

HME• HME only supplies about 50% humidity• Contraindicated with

– Dehydration– Thick secretions– Hypoventilation– Prolonged use >72 hours– Patients who are hyperventilating

PEEP• Increases the baseline airway pressure.• Optimal PEEP:

– Increase PaO2 (above 60 at minimum not over 100, with least amount of hemodynamic effects)

– Assess intrinsic PEEP with flow-time and expiratory pause

• Two major indications– Shunt and refractory hypoxemia– Decreased FRC and lung compliance

• Atelectasis, pulmonary edema, air trapping

Complications of PEEP• Decrease venous return (decreases CO, decreases

blood to kidney, GI tract, liver…) Causes ADH release and fluid accumulation

• Barotrauma• Increased ICP• Alterations in renal function and H20 balance• Alterations in liver function.• ASSESS hemodynamics (CVP, PAP, PCWP, Blood

Pressure/MAP, urine output, lab values…)

Effects on Intrapleural Pressure

PEEP increases intrapleural pressureThe extent of the increase is determined by:

1. The amount of PEEP applied2 The stiffness of the individual’s lung

Effects on Intrapleural Pressure

The > the pulmonary compliance, the > the transmission of PEEP to the intrapleural space and the greater the increase in intrapleural pressure.

Effects on FRC

Regardless of the condition of the lung at the time of application, PEEP increases FRC

FRC is increased by these primary mechanisms:1. Lungs are elastic. Any increase in end expiratory pressure increases over all

lung volume.

Effects on FRC

FRC is increased by these primary mechanisms:The diameter of conducting airway can increase 1

to 2 mm as PEEP is applied.In pts with a decrease FRC as a result of alveolar

collapse caused by surfactant instability, PEEP maintains alveoli inflated after they are recruited by the peak airway pressure.

Effect on Pulmonary Compliance

Because PEEP increases FRC, it alters pulmonary compliance.

Effect on Pulmonary Compliance

Monitoring of effective static compliance can be used to help to determine the “optimal” or most appropriate PEEP level- Best compliance

changes in VT will change the PEEPconsidered optimalVt should always be constant during

PEEP titration

Effect of PEEP on Deadspace

Because PEEP increases FRC by distending alveoli, deadspace is usually increased in:- Patients with normal lungs- Patients with COPD- Pts with non-homogeneously distributed disease process

Effect of PEEP on Deadspace

Because stabilization of recruited alveoli, appropriated PEEP levels usually decrease deadspace in pts with ALI/ARDS

Some have proposed monitoring deadspace or changes in CO2 at a constant VE as an indication of appropriate PEEP level

Effect of PEEP on the Cardiovascular System

Is a reduction in CO as a result of increased impedance to venous return by an increased in intrathoracic pressure

This increase in pressure decreases end diastolic volume and stroke volume of both ventricles

Higher levels of PEEP markedly increase right ventricular afterload, increasing end-diastolic volume and decreasing ejection fraction

Effect of PEEP on the Cardiovascular System

This reduces left ventricular distensibilityThis results in a decrease in left ventricular

end-diastolic volume and stroke volume

Effect of PEEP Therapy on PaO2

Because PEEP therapy causes a minor increase in the partial pressure of oxygen in the lung, a small increase in PaO2 may be noted even in the healthy lung.

In patients with ALI/ARDS, PaO2 levels also demonstrated only a small increase as the PEEP level is increased and will not markedly increase until PEEP is sufficient to avoid de-recruitment of recruited alveoli has been set.

Effect of PEEP Therapy on PaO2

When appropriate PEEP is set, PaO2 values may increase significantly.

PEEP PaO2 cm H20 mmHg 0 45 5 48 10 53 12 56 15 110

Effect on Intrapulmonary Shunt

Increasing PEEP levels result in a decrease in intrapulmonary shunt.

As recruited alveoli are maintained open with PEEP, ventilation/perfusion matching improves and shunting decreases.

Intrapulmonary shunt may continue to decrease even when CO is significantly decreased.

Indication For PEEP Therapy

ALI/ARDS- Atelectasis and consolidation- Decrease lung compliance- Decrease FRC- Refractory hypoxemia- Increased intrapulmonary shunting- Altered surfactant function

Indication For PEEP Therapy

Secondary Indications- Acute cardiogenic pulmonary edema- Chest Trauma- Apnea of prematurity- Obstructive Sleep Apnea- COPD- Asthma

Ventilator Induced Lung Injury (VILI)

The application of mechanical Ventilation can cause lung injury:- Oxygen toxicity- Barotrauma- Volume trauma- Atelectrauma- Biotrauma

Oxygen Toxicity

High inhaled oxygen concentration results in the formation of oxygen free radicals.

Radicals cause ultra changes in the lung similar to acute lung injury.

Animals - 100% O2 causes death in 48-72 hours.

Healthy humans - 100% O2 develop inflammatory changes in 24 hours.

Ideally the FIO2 should be < 60%.

Barotrauma

Is the most acute and immediate severe form of ventilator induced lung injury.

Is literally air within a body space or compartment.

It is a result of disruption of the alveolar capillary membrane that allows air to dissect along facial planes and accumulate within the pleural space or some other compartment.

Potential Complications of MV

• Ventilator malfunction– Manually ventilate patient

• Cardiovascular compromise– Monitor vital signs– Support cardiac output: volume replacement,

inotropes• Barotrauma

– Alveolar rupture due to overdistention– Monitor PIP, breath sounds

Potential Complications of MV

• Infection

– ET tube bypasses natural airway defense mechanisms• Nosocomial pneumonia, aspiration pneumonia

– Good hand washing, provide mouth and tube care• Psychological

– Patients may be extremely anxious and/or agitated– Give consistent, calming explanations, offer reassurance– Sedation, anti-anxiety agents frequently indicated

I:E Ratio

• The ratio of inspiratory to expiratory time.• Kept 1:2 to 1:4• Inverse ratios uncommon• Increase E-time with COPD, increase E-time to

correct air-trapping• Calculate I:E ratios

– I-time, TCT, E-time

I:E Ratio

• Longer I times used to increase mean airway pressure and improve oxygenation.

• Longer E times used on pts to reduce the possibility of air trapping and auto peep.

Factors Effecting I:E Ratio• Flow rate

• Tidal Volume

• RR

• Peak Flow

• Flow Pattern

• Inspiratory Time

I:E ratios

• When you make changes to rate of tidal volume/or pressure limit, you may have to adjust flow or I-time to maintain I:E ratio

• Auto-peep from inadequate exhalation can lead to patient ventilator asynchrony

Selection of FiO2

• Goal: To achieve clinically acceptable PaO2 between 60 - 100 mmHg.

• If PaO2 is within desired range before vent support, use same FiO2 when ventilation is started.

• For emergencies: Start at 100% FiO2.– CHF/Pulmonary Edema– CO poisoning– Smoke Inhalation/Burns

• All others 40-60%

Selection of FiO2

• If baseline ABG is not available, select an initial high FiO2 (40-60%) to benefit patients with presumed severe hypoxemia.

• If starting at 100% FiO2, reduce this as quickly as possible. Continuous use is not recommended:– Reabsorption (or resorption) atelectasis– Oxygen toxicity

Selection of FiO2

• FiO2 can be adjusted after ventilation has started based initially on an SpO2 of > 92% (PaO2 60 mmHg).

• If > than 50% - 60% is needed due to intrapulmonary shunting, add PEEP.

Manipulation• Non-compensated Respiratory Acidosis:• You need to increase Ve. On AC mode this is

done by:– Increasing VT (8-12 range), watch PIP’s– Increasing PIP, watch total PIP– Increasing rate, unless patient is breathing over BUR– increase Ve target if on MMV or ASV modes– Remove any unnecessary mechanical deadspaceOn SIMV mode: you can increase rate even if patient is

over BUR, or increase VT/PIP or increase PSV to increase Spontaneous VTe

Ventilator Review

• On HFOV: To decrease PaCO2– Increase AMP, then decrease Hz, Induce leak

around ETT cuff. – To increase PaCO2 do the opposite– To improve PaO2, increase FIO2 and MAP

• On APRV: – To decrease PaCO2 Increase HP or Increase LT or

decrease low Pressure

Ventilator Review

• Uncompensated Respiratory Alkalosis• On ACV mode:

– Decrease rate first if patient is not breathing over BUR.

– Decrease VT or PIPOn SIMV decrease Rate, VT/PIP or PSV OR change to CPAP mode

Ventilator Review• Vent Check:

– Check ventilator orders, check for new orders and assure old orders. Weaning orders? Pertinent procedures that would require transport or procedures that would require your presence like a bronch?

– Assess patients chart first know patients Hx and why they are on the ventilator

– CXR, CT scan and all other pertinent diagnostic tests– ABG, CBC, other pertinent labs– Sedation– Hemodynamics, BP, arrthymias and cardiac status

Ventilator Review• Vent Check

– Note if patient is in isolation– Assess patient’s vital signs– Check BS, HR, Spo2, cardiac rhythm, BP and

hemodynamics– Assess capnography if applicable– Note presence of Foley and its contents, chest tubes,

NG tubes, PICC lines, IV’s, A-lines…– Note medications hanging in room– Note patients ETT tape or holder, does it need to be

changed

Ventilator Review

• Vent Check– Note ETT size and location at lip.– Note patient and their sensorium – Perform MLT/MOV or check cuff pressure directly– Ensure tubing is free from condensation, if patient

is on a heater, drain circuit into water trap, ensure heater water is filled. If HME, ensure it is not occluded, if it is, change it

– Note inline suction ballard, if heavily soiled, change it

Ventilator Review• Vent Check

– Check patients settings, mode, VT/Pip, rate, rise time, sensitivity…also alarm settings and apnea settings

– Assess ventilator graphics, note presence of over distension, air leaks, auto-peep, secretions…

– Record monitored data including: PIP, VTE/VTI, Ve, Rate, Static Compliance, Dynamic compliance, MAP, total PEEP…

– Check suction pressure, suction patients lungs as needed and also mouth with yonker

– Document all pertinent information– If you do not document it wasn’t done!

Ventilator Review

• Vent Check– Your first vent check should be the most time consuming. – Any changes that are made, make sure the patients RN is

aware– As a student you will not be making any changes without

approval from your preceptor– Typically a brief summary is written regarding the patient.

Put any changes you made or ABG’s you drew here and maybe the plan for the day

– Inline HHN or MDI’s should be given AFTER you have done your check and suctioned patient (if it was needed)

Ventilator Review

• Vent Check– The patient should have a resusitation bag at

bedside, plugged into oxygen. If the patient is on PEEP, ensure there is a peep valve.

– The ventilator should be plugged into the red outlet incase of power outage

– Note signs in room for Dialysis Shunts– A spare trach should be in the room for trach

patients

Ventilator Review

• Transporting patients:– The hospital will either make you attach the

patient to a transport ventilator or you will bag the patient to their destination

– You may have to bring along the ventilator and attach it once you reach the area you are transporting to, in this case, simply select same patient so that all the settings remain

– Have a full E-tank available. Assist in the pushing of gurney and also the attachment of monitors

Troubleshooting

• If the ventilator is alarming and the immediate fix is not apparent, you must take the patient off and bag them until the problem can be solved

• For high pressure alarms: assess patient for asynchrony, fighting ventilator, mucus, change in compliance, increase RAW, bronchospasm, biting tube…. Inform your preceptor if you can not resolve the issue yourself. For example patient is biting tube, inserting an oral airway, don’t do it alone

Consider the following

• Secretions in airway • Tube block• Kinking of tube• Biting the tube• Water in the tube• Cuff herniation• Rt. bronchial intubation • Fighting the ventilator

•Cough•Increased airway resistance•Bronchospasm•Decreased compliance•Atelectasis•Fluid overload•Pneumothorax

Troubleshooting

• If the low pressure, or low Vte alarm is sounding. – Check for obvious leaks, if a leak if found plug it– Check cuff pressure, if blown, let your preceptor

know, the ETT may have to be changed– If patient self extubated, and it is plainly obvious

(tube is seen hanging from patients mouth), finish the extubation, bag as needed and call for help

Troubleshooting

• 18 yr old man intubated for organophosphorus poisoning and intermediate syndrome was on the following settings: AC 12, VT 550, FIO2 30%

• He suddenly desaturates. You notice that his resp rate is 35/min, heart rate is 120/min, BP is 90/70mmHg.

• Auscultation reveals equal vesicular breath sounds. What would you do?

Troubleshooting

• A 35 yr old man with status epilepticus following organochloride ingestion is being ventilated in the ICU. You are called because of desaturation and persistent low pressure alarms. How would you tackle the situation?

Consider the following

• Cuff leak.• Leak in the circuit • Loose connections • ET tube displacement• Disconnection• Inadequate flow• Low supply gas pressures

Low pressure alarm

• FiO2 to 100%• Check all connections for leaks. Start from ventilator

inspiratory outlet—humidifier—inspiratory limb—nebulizer—Y junction—dead space—et tube cuff—expiratory limb—expiratory valve.

• If inspiratory effort excessive-inadequate flow—increase inspiratory flow, decrease Ti, increase TV

• Check gas pressures• If all normal and problem persists, change ventilator

High pressure alarm

•FiO2 to 100%•Look at chest movement, auscultate air entry.

AUSCULTATION

UNEQUAL AIR ENTRY•Collapse,

•tube malposition•pneumothorax

DECREASED AIR ENTRY BILATERALLY

Tube/tracheal block

WHEEZESBronchospasm

Ventilator Alarms• Low Pressure

– Loss of circuit pressure– Loss of system pressure– Premature termination of inspiration– Inappropriate ventilator settings– Set 5 – 10 cm below peak pressure

Ventilator Alarms

• Low PEEP/CPAP

– Set at 2 – 5 cm H2O below PEEP level

– Due to leaks

Ventilator Alarms• High RR Alarm

– Set 10-15 breaths over observed rate– Indicates tachypnea and resp distress– Auto cycling of ventilator

• Low RR Alarm– Not less than 6 – 8 (preferred) breaths per minute

Ventilator Alarms

• Low exhaled Ve

– 10% - 15% below average minute volume

Ventilator Alarms• Low exhaled tidal volume

– Set 100-200 ml lower than exhaled Vt– Could also be estimated at 10% - 15% below set Vt

– Indicates• Leaks/Disconnects• Severe air trapping• Decrease compliance in PCV• LOW VTE ALARM WILL SOUND AS HIGH PRESSURE ALARMS

SOUNDS, SINCE VOLUME WILL PREMATURLY TERMINATE

Ventilator Alarms• Apnea

– Set back up parameters with 20 second time interval.

– Ensures a minimum number of breaths will be delivered to the patient.

Ventilator Alarms

• Oxygen (FiO2)

– 5% above and below set FiO2

Auto PEEP• Air trapping related to airway obstruction,

rapid RR, long inspiratory times, insufficient expiratory time.

• Seen with auto peep maneuver and flow vs. time wave form.

Reducing Auto PEEP• Reduce airway obstruction through

bronchodilators/steroids.• Increase expiratory time

– Decrease RR– Increase inspiratory flow rate– Decrease tidal volume– Decrease inspiratory time

Weaning• If the patient is to be weaned…

– Perform weaning parameters. This may be done through the ventilator on most modern vents. If you are to do a VC or MIP, the patient is typically on CPAP mode without PEEP and minimal PSV if any. Assess VC, MIP, MEP several times for reproducibility

– While weaning note vital signs, RSBI, Vte, RR, SpO2…– If patient fatigues to the point that their vitals decline, you

should place them back on previous mode/settings– You may get a ABG after a short time frame while weaning

to assess effectiveness– Weaning can be done numerous ways…SBT, CPAP trials, to

Bipap…

Compliance changes

• Static vs dynamic• Know formula and causes for each• Static: use inspiratory hold to assess plateau,

increasing plat=decreasing static compliance. Assess by looking at press-vol loop

• Caused by ARDS, pulm edema, atelectasis, pneumothorax, obesity…

• Dynamic: Decreased with increases in RAW

Adequate Plateau Time

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Compliance

• Trend static and dynamic compliance• Decreasing static compliance= changing to

lung protective strategies, low volumes/high rates and peep, APRV, HFV…

• Decreasing Dynamic compliance = suction, bronchodilator, bite block, heated humidity…

Management Options – Inspiratory Time

Principle of Use

– Increase in inspiratory time (TI) causes increase in

– Increase in aids in maintaining integrity of alveoli and

recruiting atelectatic alveoli

– Associated with improvement in

– Associated with improvement of PaO2 in patients with ARDS

Management Options – Bronchial Hygiene

• Postural drainage

• Percussion

• Adequate humidification

• Ambulation, sitting up, turning patient

Management Options – Patient Positioning

• Ambulation, sitting up helpful in improving

oxygenation

• Turning patient from side to side aids in

bronchial hygiene

Management Options – Patient Positioning

Prone Positioning

– May result in dramatic improvement in

oxygenation in patients with ARDS and ALI

– Care must be taken to ensure tubes and lines are

not displaced during turning

– May improve and reduce shunting by removing

pressure of the heart on the dorsal regions

Evaluation of Ventilation – Physical Findings

Heart Rhythms

– Abnormal rhythms

– Tachycardia

– Bradycardia Chest excursion

Altered Mental State

– Anxiety

– Confusion

– Combativeness

– Somnolence

Evaluation of Ventilation – Diagnostic Findings

Arterial Blood Gases

– Increased PaCO2

– Decreased pH

– Decreased PaCO2

Bedside Spirometry Results

– Negative inspiratory force (NIF) – < -20 cmH2O

– Spontaneous tidal volume – < 5 mL/kg IBW

– Vital capacity – < 10 mL/kg IBW

Evaluation of Ventilation – Determine Cause of Problem

Hypoventilation

– Inadequate alveolar ventilation –

A = (VT – VDS) (f)

– Increase in physiologic dead space –

VD/VT = (PaCO2 – PECO2)/PaCO2


Increase in Carbon Dioxide Production

– Stress

– Shivering

– Pain

– Asynchrony with ventilator

– High carbohydrate diet


Change in Lung and Chest Mechanics– Compliance – C = ∆V/∆P

• ∆V = VT Corrected for Tubing Compliance

• ∆P = Pplat – PEEP

Causes of decreased lung compliance– Atelectasis– Pulmonary edema– ALI/ARDS– Pneumothorax– Fibrosis


Causes of decreased thoracic compliance

– Obesity

– Pleural effusion

– Ascites

– Chest wall deformity

– Pregnancy


Causes of increased thoracic compliance

– Flail chest

– Loss of chest wall integrity

– Change in patient position


Change in Lung and Chest Mechanics

– Airway Resistance – RAW = ∆P/∆

• ∆P = (Ppeak – Pplat)

• ∆ = flow

Evaluation of Ventilation – Determine Cause of ProblemCauses of increased resistance

– Bronchospasm

– Mucosal edema

– Secretions

– Excessively high rate of gas flow

– Small endotracheal tube

– Obstruction of endotracheal tube

– Obstruction of the airway


Causes of decreased resistance

– Bronchodilator administration

– Decrease in flow of gas

– Administration of bronchial hygiene


• Loss of Muscle Strength/Neurological Input

– Rapid Shallow Breathing Index (RSBI)

• Indication of whether patients have the ability

to breathe without ventilatory support

Evaluation of Ventilation – Determine Cause of Problem Loss of Muscle Strength/Neurological Input

– Rapid Shallow Breathing Index (RSBI)

• f/VT

– If < 100 breaths/min/L, patient has ability to breathe without ventilator

– If > 100 breaths/min/L, patient will likely not be able to sustain spontaneous breathing

– Maximal inspiratory pressure

– Maximum voluntary ventilation

Evaluation of Ventilation – Management Options

Increase Alveolar Ventilation

– Increase in Mechanical Tidal Volume

• Normal Volume – 6 to 12 mL/kg IBW

• Most direct way to change alveolar ventilation

• Should normally not exceed 12 to 15 mL/kg IBW

• Associated with increase in peak inspiratory pressure

which has increased risk of trauma to lung


– Increase in spontaneous ventilation

• More advantageous to patient than increasing

mechanical tidal volume

• Augmentation by pressure support mode helps

overcome resistance of ventilator circuit and artificial

airway


Increase Alveolar Ventilation

– Increase in Mechanical Rate

• Normal Value – 12 to 18 Breaths per Minute

• Should Normally not Exceed 20 Breaths per Minute

• Prediction of Desired Rate

New rate =


Decrease Carbon Dioxide Output (Production)

– Medicate patient to relieve pain, stress, and

prevent asynchrony, decreasing work of breathing

– Maintain patient’s temperature within normal

range

– Provide appropriate nutrition


Treat Underlying Pulmonary Pathophysiology

Maintain airway in patent state

– Prevent accumulation of secretions in airway

– Use properly sized artificial airway

– Prevent occlusion of airway by patient; use bite

block

Considerations in Management – Permissive HypercapneaAllowing PaCO2 level to remain elevated above

45 mmHg

• Purpose

– Maintain plateau pressure at an acceptable level (<

30 cm H2O) by decreasing tidal volume to less than

6 mL/kg and increasing respiratory rate, thereby

minimizing trauma and cardiovascular side effects

Considerations in Management – Permissive Hypercapnea

Method

– Decrease tidal volume and increase respiratory rate, while maintaining minute volume

– If PaCO2 increases and pH decreases, either permit normal metabolic compensation or administer medications to maintain level at 7.25 to 7.35

– Institute gradually to allow PaCO2 to increase gradually over hours or days


Relative Contraindications or Cautions

– Presence of cardiac ischemia– Presence of pulmonary hypertension– Compromised left ventricular function– Right heart failure– Head trauma– Intracranial disease– Metabolic acidosis


Absolute Contraindication

– Intracranial lesions

ventilator review

Documents

patient triggered breaths

patient apneic

pressuretime graph

spontaneous vt

vssimvpc ps

spontaneous breaths

vssimvprvc ps

vsspontaneous ps