Principles of mechanical ventilation
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Principles of Mechanical Ventilation. RET 2284 Module 6.0 Ventilator Management - Improving Ventilation/Oxygenation. Improving Ventilation / Oxygenation.

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Principles of mechanical ventilation

Principles of Mechanical Ventilation

RET 2284

Module 6.0 Ventilator Management

- Improving Ventilation/Oxygenation


Improving ventilation oxygenation

Improving Ventilation / Oxygenation

The first 30 – 60 minutes following initiation of ventilation are generally spent evaluating vital signs, breath sounds, ventilator parameters, lung compliance and resistance, the artificial airway, and documenting patient response to therapy

After that initial phase, the RT is often concerned with improving ventilation and oxygenation and managing the patient-ventilator system


Improving ventilation oxygenation1

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • A change in will often be needed when a patient is first placed on mechanical ventilation to correct for respiratory alkalosis or acidosis; this is facilitated by making a change inVT or rate (f)


Improving ventilation oxygenation2

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Methods of Changing Ventilation Based on PaCO2 and pH

      If it is appropriate to keep rate (f) constant and change VT, the equations is as follows:

      Desired VT = Known PaCO2 x Known VTDesired PaCO2


Improving ventilation oxygenation3

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Methods of Changing Ventilation Based on PaCO2 and pH

      If it is appropriate to keep VT the same and change rate (f), then the equations is as follows:

      Desired f = Known PaCO2 x Known fDesired PaCO2


Improving ventilation oxygenation4

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Respiratory Acidosis

      • Volume and Pressure Ventilation Changes

        • When PaCO2 is elevated (>45 mm Hg) and pH is decreased (<7.35), respiratory acidosis is present and VA is not adequate

        • Causes

          • PE, Pneumonia

          • Airway disease (e.g., severe asthma attack)

          • Pleural abnormalities (e.g., effusions)

          • Chest wall abnormalities

          • Neuromuscular disease

          • CNS problems

.


Improving ventilation oxygenation5

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Respiratory Acidosis

      • Volume and Pressure Ventilation Changes

        Guideline:

        • VT to 8 – 12 mL/kg ideal body weight (based on patient’s pulmonary problem)

        • Maintain plateau pressure <30 cm H2O

        • If VT is already high and/or Pplateau are already high, then f should be increased

          • Read example 1, 2 and 3: Respiratory Acidosis, Increasing VT, page 259 – 260 (Pilbeam)


Improving ventilation oxygenation6

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Respiratory Alkalosis

      • Volume and Pressure Ventilation Changes

        • When PaCO2 is decreased (<35 mm Hg) and pH increases (>7.35), then respiratory alkalosis is present and alveolar ventilation is excessive

        • Causes

          • Hypoxia with compensatory hyperventilation

          • Parenchymal lung disease

          • Medications

          • Mechanical ventilation

          • CNS disorders

          • Anxiety

          • Metabolic disorders


Improving ventilation oxygenation7

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Respiratory Alkalosis

      • Volume and Pressure Ventilation Changes

        Guideline:

        • Volume ventilation: f, and if necessary, VT

        • Pressure ventilation: f, and if necessary, pressure

          • Read example 1 and 2: Respiratory Alkalosis, Decreasing the rate, page 261 (Pilbeam)


Improving ventilation oxygenation8

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Treatment of metabolic acidosis and alkalosis should focus on identifying those metabolic factors that can cause these acid-base disturbances


Improving ventilation oxygenation9

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Metabolic Acidosis

        • Causes

          • Ketoacidosis (alcoholism, starvation, diabetes)

          • Uremic acidosis (renal failure to excrete acid)

          • Loss of bicarbonate (diarrhea)

          • Renal loss of base following administration of carbonic anhydrase inhibitors (e.g., Diamox)

          • Overproduction of acid (lactic acidosis)

          • Toxin ingest that produce acidosis (salicylate, ethylene glycol [antifreeze], methanol


Improving ventilation oxygenation10

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Metabolic Acidosis

        • Treatment should first deal with the cause of the acidosis

        • Secondly, assess the need to reverse the acidemia with some form of alkaline agent


Improving ventilation oxygenation11

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Metabolic Acidosis

        • These patients are often struggling to lower their PaCO2 to compensate for the metabolic acidemia. As a consequence, these patients are at risk for developing respiratory muscle fatigue

        • If the patient is losing the struggle to maintain high with spontaneous breathing, assisted ventilation may be necessary to avoid respiratory failure. It is then appropriate to keep the pH (7.35 – 7.45)


Improving ventilation oxygenation12

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Metabolic Alkalosis

        • Causes

          • Loss of gastric fluid and stomach acids (vomiting, nasogastric suctioning)

          • Acid loss in the urine (diuretic administration)

          • Acid shift into the cells (potassium deficiency)

          • Lactate, acetate, citrate administration

          • Excessive bicarbonate loads (bicarbonate administration)


Improving ventilation oxygenation13

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Metabolic Acidosis and Alkalosis

      • Metabolic Alkalosis

      • Treatment involves correcting the underlying cause and reversing those factors leading to the alkalosis. In severe cases, carbonic anhydrate inhibitors, acid infusion, and low bicarbonate dialysis my be required

        • Only in rare circumstances does partial respiratory compensation of metabolic alkalosis occur – PaCO2 will usually not rise higher than 55 mm Hg (Remember that as the CO2 rises, the PaO2 falls)


Improving ventilation oxygenation14

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Mixed Acid – Base Disturbances

      • Combined Respiratory Alkalosis and Metabolic Acidosis

        • Read case studies: Pilbeam, pg. 262 – 263

      • Combined Respiratory Acidosis and Metabolic Alkalosis

        • Read case study: Pilbeam, pg. 263


Improving ventilation oxygenation15

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Increased Physiological Dead Space

      • If pure respiratory acidosis persists even after alveolar ventilation has been increased, the patient may have a problem with increased dead space

        • Causes

          • Pulmonary emboli

          • Low cardiac output  low pulmonary perfusion

          • High alveolar pressure (PEEP)   pulmonary blood flow

          • Air trapping   pulmonary perfusion


Improving ventilation oxygenation16

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Increased Metabolism and Increased CO2 Production

      • Read case study: Pilbeam, pg. 264

      • Metabolic rate and VCO2 are increased in the following patients:

        • Fever

        • Sepsis

        • Burns

        • Multiple trauma and multiple surgical procedures

        • Hyperthyroidism

        • Seizures

.


Improving ventilation oxygenation17

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Increased Metabolism and Increased CO2 Production

      • In these patients is increased and WOB is elevated

        Treatment Options

        • Increase machine rate to WOB: may cause auto-peep

        • Add pressure support for spontaneous breaths to WOB through ET and circuit

        • Switch to PC-CMV, use sedation to WOB


Improving ventilation oxygenation18

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Intentional Iatrogenic Hyperventilation

      • Definition

        • Deliberate hyperventilation in patients with acute head injury and increased intracranial pressure (ICP)

          • Hyperventilation reduces PaCO2 which causes vasoconstriction of cerebral blood vessels and decreases blood flow to the brain and is believed to lower increased intracranial pressure ICP


Improving ventilation oxygenation19

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Intentional Iatrogenic Hyperventilation

      • Current therapy guideline for head injuries with increased ICP do not recommend prophylactic hyperventilation (PaCO2 <25 mm Hg) during the first 24 hours - may cause cerebral ischemia and cerebral hypoxemia


Improving ventilation oxygenation20

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Intentional Iatrogenic Hyperventilation

      • Hyperventilation may be needed for brief periods when acute neurological deterioration is present and ICP elevated

      • Mild hyperventilation (PaCO2 30 – 35 mm Hg) may be used for longer periods in a situation in which increased ICP is refractory to standard treatment

        The practice of iatrogenic hyperventilation still remains controversial


Improving ventilation oxygenation21

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • Definition

        • Deliberate limitation of ventilatory support to avoid lung overdistention and injury of lung

          • ARDS

          • Status asthmaticus

        • PaCO2 values are allowed to rise above normal

          • ≥50 – 150 mm Hg

        • pH values are allowed to fall below normal

          • ≥7.10 – 7.30

          • Most researchers agree pH ≥7.25 is acceptable


Improving ventilation oxygenation22

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • PaCO2 accompanied PaO2

        • O2 administration must be provided and monitored closely

      • PaCO2 stimulates the drive to breath

        • Appropriate to provide sedation to patients in whom PHY is being employed


Improving ventilation oxygenation23

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • Procedures for Managing PHY

        • Allow PaCO2 to rise and pH to fall without changing mandatory rate or volume

          • Sedate the patient

          • Avoid high ventilating pressures

          • Maintain oxygenation

        • Reduce CO2 production

          • Paralyze

          • Cool

          • Restrict glucose


Improving ventilation oxygenation24

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • Procedures for Managing PHY

        • Keep pH >7.25

          • Sodium bicarbonate

          • Tris-hydroxiaminomethane (an amino buffer)

          • Carbicarb (mixture of sodium carbonate and bicarbonate


Improving ventilation oxygenation25

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • Contraindications and Effects of PHY

        • Head trauma

        • Intracranial disease

        • Intracranial lesions


Improving ventilation oxygenation26

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      • Relatively contraindicated in the following

        • Cardiac ischemia

        • Left ventricular compromise

        • Pulmonary hypertension

        • Right heart failure


Improving ventilation oxygenation27

Improving Ventilation / Oxygenation

  • Correcting PaCO2 Abnormalities

    • Permissive Hypercapnia (PHY)

      The use of PHY is restricted to situations in which the target airway pressure is at its maximum and the highest possible rates are being used

      The risks of hypercapnia are considered by some to be preferable to the high Pplat required to achieve normal CO2 levels

      Read Case Study: Pilbeam, pg. 265 – 266


Improving ventilation oxygenation28

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Adjusting FiO2

      • Every attempt should be made to maintain the FiO2 <0.40 to 0.50 to prevent the complications of O2 toxicity while keeping the PaO2 between 60 and 90 mm Hg

        • This goal is not always possible and sometimes a higher FiO2 is required

      • The SpO2 can be used to titrate FiO2, with the goal of maintaining the SpO2 >90%

        • The SaO2 on an ABG is used to establish the relationship with the current SpO2

.


Improving ventilation oxygenation29

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Adjusting FiO2

      • ABGs are obtained after mechanical ventilation is initiated and compared with FiO2 being delivered and the SpO2 to establish their relationships

      • A linear relationship exists between PaO2 and FiO2 as long as VE, CO, Shunt, VD/VT remain fairly constant (cardiopulmonary status)

.


Improving ventilation oxygenation30

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Adjusting FiO2

      • Because of the linear correlation between PaO2 and FiO2 the following equation can be used to select the desired FiO2 to achieve a desired PaO2:

        Desired FiO2 = PaO2 (desired) x FiO2 (known)

        PaO2 (known)


Improving ventilation oxygenation31

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Adjusting FiO2

      Exercise

      After being supported on a ventilator for 30 minutes, a patient’s PaO2 is 40 mm Hg on an FiO2 of 0.50. Acid-base status is normal and all other ventilator parameters are within the acceptable range. What FiO2 is required to achieve a desired PaO2 of 60 mm Hg?


Improving ventilation oxygenation32

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Adjusting FiO2

      Desired FiO2 = PaO2 (desired) x FiO2 (known)

      PaO2 (known)

      Desired FiO2 = (60 mm Hg) (0.50 FiO2)

      40 mm Hg

      Desired FiO2 = 0.75


Improving ventilation oxygenation33

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Selection of FiO2 or Adjustment of Paw

      • Maintaining an FiO2 >60 may lead to:

        • O2 toxicity

        • Absorption atelectasis

      • Lower limits of target PaO2 is 60 mm Hg

      • Lower limits of target SpO2 is 90%

_

_


Improving ventilation oxygenation34

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Selection of FiO2 or Adjustment of Paw

      • When PaO2 remains very low on high FiO2, significant shunting, V/Q abnormalities , and/or diffusion defects are present - other methods to improve oxygenation, besides increasing FiO2, must be considered

        • Paw

          • PEEP

          • HFOV

          • APRV

_

_


Improving ventilation oxygenation35

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Selection of FiO2 or Adjustment of Paw

      • Paw can be used to increase the PaO2

      • Factors that affect Paw during PPV

        • PIP

        • PEEP

        • Auto-PEEP

        • I:E ratio

        • Respiratory rate

        • Inspiratory flow patterns

_

_

_


Improving ventilation oxygenation36

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Selection of FiO2 or Adjustment of Paw

      • Paw is a major determinant of oxygenation in patients with ARDS

        • Mean alveolar pressure  oxygenation

        • Alveolar recruitment  oxygenation

      • Typical method to increase Paw

        • PEEP

      • Other methods to increase Paw

        • HFOV

        • APRV

_

_

_

_


Improving ventilation oxygenation37

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Selection of FiO2 or Adjustment of Paw

      • Paw must be monitored closely to prevent:

        • Air trapping

        • Overdistention

        • Barotrauma (e.g. pneumothorax)

        • Venous return

        • CO

_

_


Improving ventilation oxygenation38

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Goals of PEEP

        • Enhance tissue oxygenation

        • Maintain a PaO2 above 60 mm Hg, and SpO2 ≥90% at an acceptable pH

        • Restore FRC

      • These goals my be accompanied by the opportunity to reduce the FiO2 to safer levels (<0.50) as PEEP becomes effective

        • Must maintain cardiovascular function and avoid lung injury


Improving ventilation oxygenation39

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Minimum or Low PEEP

        • PEEP at 3 – 5 cm H2O to help preserve a patient’s normal FRC

      • Therapeutic PEEP

        • PEEP >5cm H2O

        • Used in the treatment of refractory hypoxemia caused by increased intrapulmonary shunting and V/Q mismatching accompanied by a decreased FRC and pulmonary compliance


Improving ventilation oxygenation40

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Optimal PEEP

        • The level of PEEP at which the maximum beneficial effects of PEEP occur

          • O2 transport

          • FRC

          • Compliance

          • Shunt


Improving ventilation oxygenation41

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Optimal PEEP

        • The level of PEEP is considered optimum because it is not associated with profound cardiopulmonary side effects

          • Venous return

          • CO

          • BP

          • Shunting

          • VD/VT

          • Barotrauma

          • Volutrauma

        • Accompanied by safe levels of FiO2


Improving ventilation oxygenation42

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Indications for PEEP Therapy

        • Bilateral infiltrates on chest radiograph

        • Recurrent atelectasis

        • Reduced CL

        • PaO2 <60 mm Hg on high FiO2 of >0.5

        • PaO2/FiO2 ratio <200 for ARDS and <300 for ALI

        • Refractory hypoxemia: PaO2 increases <10 with FiO2 increase of 0.2


Improving ventilation oxygenation43

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Specific clinical disorders that may benefit from PEEP

        • ALI

        • ARDS

        • Cardiogenic PE

        • Bilateral, diffuse pneumonia


Improving ventilation oxygenation44

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Increased in increments of 3 – 5 cm H2O in adults, 2 – 3 cm H2O in infants

        • Target acceptable PaO2/FiO2 ratio at a safe FiO2

          • >300 (e.g., PaO2 = 100, with FiO2 = 0.33

            (optimal, but not always realistic)


Improving ventilation oxygenation45

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Patient Appearance

          • Color, level of consciousness, anxiety – a sudden deterioration may indicate cardiovascular collapse or pneumothorax

        • Blood Pressure

          • BP of 20 mm Hg systolic drop is significant

        • Breath Sounds

          • Barotrauma, e.g., pneumothorax


Improving ventilation oxygenation46

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Ventilator Parameters

          • VT, Flow, PIP, plateau pressure, VE


Improving ventilation oxygenation47

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Static Compliance (CS)

          • As PEEP progressively restores FRC, compliance should increase


Improving ventilation oxygenation48

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Static Compliance (CS)

          • Too Much PEEP  Overdistention  CS


Optimized lung volume safe window

Optimized Lung Volume “Safe Window”

  • Overdistension

    • Edema fluid accumulation

    • Surfactant degradation

    • High oxygen exposure

    • Mechanical disruption

  • Derecruitment, Atelectasis

    • Repeated closure / re-expansion

    • Stimulation inflammatory response

    • Inhibition surfactant

    • Local hypoxemia

    • Compensatory overexpansion

Zone of

Overdistention

Injury

“Safe”

Window

Zone of

Derecruitment

and Atelectasis

Volume

Injury

Pressure


Application of peep

Application of PEEP


Improving ventilation oxygenation49

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Arterial PO2, FiO2, and PaO2/FiO2

          • The usual approach to the management of FiO2 and PEEP is to start with high FiO2 and incrementally decrease it as PEEP improves oxygenation


Improving ventilation oxygenation50

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Arterial to End-Tidal Carbon Dioxide Tension Gradient

          • Normal P(a-et)CO2 gradient is 4.5 ± 2.5 (Pilbeam)

          • Is lowest when gas exchange units are maximally recruited without being overdistended

          • If P(a-et)CO2 gradient increases minimal acceptable values, it signifies that too much PEEP has been added and is producing a drop in cardiac output and in increase in VD/VT


Application of peep1

Application of PEEP


Improving ventilation oxygenation51

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Arterial-to-Venous Oxygen Difference (C(a-v)O2) reflects O2 utilization by the tissues

          • Normal value is 5 vol%

          • Increases in C(a-v)O2 with increases in PEEP may indicate hypovolemia, cardiac malfunction, decreased venous return to the heart, and decreased cardiac output from PEEP


Application of peep2

Application of PEEP


Improving ventilation oxygenation52

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Mixed Venous O2 Tension or Saturation

          • Normal PvO2 = 35–40 mm Hg

            (minimal acceptable is 28 mm Hg)

          • Normal SvO2 = 75%

            (minimal acceptable is 50%)

          • PEEP usually improves PvO2 and SvO2

          • When PvO2 and/or SvO2 decrease, with a increase C(a-v)O2 increase, this indicates a decrease in cardiac output – TOO MUCH PEEP


Application of peep3

Application of PEEP


Improving ventilation oxygenation53

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Cardiac Output

          • Cardiac output provide key information about the body’s response to PEEP

          • PEEP improves V/Q  Oxygenation  CO

          • Too much PEEP  Overdistention  Venous return  CO


Application of peep4

Application of PEEP


Improving ventilation oxygenation54

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Application of PEEP

        • Pulmonary Vascular Pressure Monitoring

          • When using PEEP >15 cm H2O, it is important to closely evaluate the patient’s hemodyamic status, which may require the placement of a pulmonary artery catheter

          • If pulmonary artery occluding pressure (PAOP), also known as “wedge pressure,” rises markedly as PEEP is increased, the lungs may be overinflated

          • On the other hand, when PEEP rises, PAOP may be markedly decreased because of pulmonary blood flow is reduced as a result of decreased venous return to the right side of the heart


Application of peep5

Application of PEEP


Improving ventilation oxygenation55

Improving Ventilation / Oxygenation

Data From a Patient with ARDS on MV 24 Hours after Admission

VT: 700f: 6VE: 6.6FiO2: 0.8

PEEPBPHR PCWP COCSPIPPaO2PVO2

0130/65130164.828504027

  • 120/55135134.231584537

  • 135/65125185.833605035

  • 130/70120195.9365511537

  • 110/50130254.1276315029

    Can you find the optimal PEEP level?


Improving ventilation oxygenation56

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Weaning From PEEP

        • Patient should demonstrate an acceptable PaO2 on an FiO2 of <0.40

        • Must be hemodynamically stable and nonseptic

        • Lung conditions should have improved

          • CS, PaO2/FiO2 ratio

        • Reduce PEEP in 5 cm H2O increments

        • Evaluate SpO2 within 3 minutes to determine effect – if it falls <20% from previous PEEP level, the patient is ready to tolerate lower PEEP level. If SpO2 drops >20% place PEEP at previous level


Improving ventilation oxygenation57

Improving Ventilation / Oxygenation

  • Oxygenation Using FiO2 and PEEP

    • Positive End Expiratory Pressure (PEEP)

      • Weaning From PEEP

        • Wait between reductions in PEEP and reevaluate the initial criteria. If the patient is stable, reduce PEEP by another 5 cm H2O. This may take 1 hour or may require as long as 6 hours or more

        • When the patient is at 5 cm H2O, an additional evaluation is necessary. If reducing the PEEP to zero result is a worsening of the patient, then it may be appropriate to leave the patient at 5 cm H2O until extubation


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