The Many Disguises of PEEP:Case Presentations

Bradley J. Phillips, MD

Burn-Trauma-ICUAdults & Pediatrics

PEEP

Positive End Expiratory Pressure Equilibrium pressure reached at end of expiration is

some small amount of pressure greater than atmospheric

PEEP = 5 mmHg considered to be physiologic

Disquises of PEEP

• Improves O2

• Increases cardiac output

• Increases lung compliance

• Worsens O2

• Decreases cardiac output

• Barotrauma• Fluid retention• Intracranial HTN

• CO2 clearance

Gas Exchange

O2

PEEP I:E alterations Positioning

• * Prone/Lateral

Rate Tidal volume I:E alternations

Intubation Criteria

Airway protection RR > 35-40 breaths/min PaCO2 > 55 mmHg ( acute)

PaO2< 70 mmHg on 100% O2 nonrebreather

A-a gradient> 400 mmHg on 100% O2 FM High spinal injury, closed head injury, ARDS, metabolic

acidosis with clinical deterioration

Benefits of PEEP?

There is no evidence that routine use of PEEP is

beneficial in all patients!

Case #2CO2 Retention

67 yom s/p radical neck dissection for tumor of posterior pharynx

PMH: COPD - steroid x 3 yearsCAD s/p IWMI 8yrs ago

PSH: CABG x3 5 years ago

SH: Beer - 4-5/daySmoker - 1.5 ppd

Case #2

Uncomplicated procedure, admitted to ICU for mechanical ventilation

PE: elderly appearing, surgical wound on neck, JP x1old scar on sternum, S2 loud breath sound quietscaphoid abdomen

LAB: WBC 14.2, Hct 25%

CXR: Hyperinflated lung o/w clear

Case #2

Initial tx : ABX per ENT (clindamycin)Albuterol inhalerIV steroids

POD2 : ExtubatedTube feedings started

POD3: Dyspnea, RR 30/minCrackles at right base, wheezing bilaterallyABG:pH 7.21, PaCO2 74, PaO2 48 @ FiO2 0.6

Case #2

ABC’s - Intubated

CXR - right sided infiltrate in lower and apical fields

Diagnosis: ?

Initial vent setting: SIMV 12/TV 650ml/FiO2 1.0/Peep 5Agitated, BP 220/120, HR 120, RR 40Peak airway pressures 60 - 65 cmH2O

Diagnosis and tx: ?

Case #2

Sedated with midazolam (Versed) drip

1 hr later : unresponsiverapid breathing, out of phase with ventilatorPAP = 70 mmH2O

Therapy : ?

1 hr later: PAP 35 cm H2OFiO2 decreased to 0.6 with O2 sats 96%ABG: 7.36/50/94

Case #2

Evening: Desats 90%Wheezing in all fields, crackles r baseCXR: new left patchy infiltrateABG: 7.34/56/68 - Vent setting changed ???90mins: ABG PaCO2 decreased, PaO2 increased

3 hrs later: Desat 93%, no ABGVent setting changed ???ABG: 7.34/58/64Vent setting changed ???ABG: 7.30/62/63, PAP 50 mmH2O

Case #2

Vent changed - FiO2 1.0, PEEP 20 cm H2OABG 7.24/68/61

Vent changed- ??? ParameterBP 132/80 to 94/54Arterial sats 80’sCXR/EKG orderedDopamine startedABG 7.10/84/52VT - CPR started

Case #2

Trap: PEEP applied to the ventilatorauto-PEEP developed by increased RRResults: Difficulty with CO2 elimination

Trick: Limit PEEP and assess for auto-PEEPReduce RR Treat reversible component of COPD

Consider I:E manipulations

PEEP effects on pulmonary physiology and gas

exchange

PEEP effects on oxygenation frequently considered PEEP effects on ventilation often neglected Physiological dead space

• Anatomic dead space• Shunt factor• V/Q mismatch• Haldane effect

PEEP effects on pulmonary physiology and gas

exchange

Factors affected by acute lung injury and chronic airflow obstruction

PEEP low levels (5-10 cm)• reduces dead space by reducing shunt

PEEP high levels (=>15)• variable and unpredictable

• V/Q mismatched • Ventilate high V/Q regions

• Reduce CO2 elimination

• Etiology ? decreased cardiac output or directcompression of alveolar capillaries

PEEP effects on pulmonary physiology and gas

exchange

High PEEP

Impaired CO2 Removal

Haldene effect

Impaired Oxygenation

Increased anatomic dead space

Alterations of V/Q

Alterations of V/Q

(Direct compression)

Case #1

75 yof s/p colostomy for perforated diverticulum

PMH: Asthma - inhalers Meds: AlbuterolDM - 10 years Atrovent

PSH: none

SH: no EtOH or Tobacco use

Case #1Hypotension

Transferred to ICU for sepsis and ventilator management

PE: ill appearing, pale, obese female mild dyspneaT 39 HR 120, SBP 90, RR 30, sats 92%, wt 80kg

Lungs: few wheezes bilateralCV: normal S1,S2Abd: distended, open skin, mild tenderness

Ext: mild edema, slight mottled distally

LABS: WBC 18K, Hct 27 Na 131, K 3.1, Bun 15, Cr 1.6, BS 220

Case #1

Initial Tx (ABC’s) : Intubate Vent AC 12/800/80%/PEEP5

NPO/IVF/NGT/ABXInhalers tx.Dopamine qttReplete K

After intubation: SBP 80’s briefly then 95ABG: 7.32/48/70/96%

Case #1

Vent changes: Increased vent rateABG: 7.36/42/65/94%

2 hrs later: Agitated, RR 25, sats 88%ABG 7.46/32/58

? Vent changes or therapeutic interventions

Case #1

Vent changes: Increased PEEP 10ABG 7.50/28/60/90%

? Vent changes or therapeutic maneuvers?

4 hrs post op : VS: HR 130’s, BP 85/60, RR30, sats 85%

What’s happening???

PEEP effects on cardiovascular output

Positive pressure ventilation • increased intrathoraci pressure• reduced venous return• decreased Cardiac output (CO)• fluid resuscitation prior to intubation

PEEP effects on cardiovascular output

High PEEP• Increased intrathoracic pressure• Barotrauma - tension PTX

Auto-PEEP (Hyperinflation)• Increased FRC with or without PEEP set• Insufficient expiratory time to expel TV• Diseases @ risk

• Emphysema - loss of elastic recoil • Asthma - increased airway resistance

Auto-PEEP

Measurement technique• Occlusion of expiratory port• Immediately before delivery of next breath• Any increase in airway pressure above end-

expiratory level represents auto-PEEP• Timing is important, too early and falsely elevated

estimate

Auto-PEEP

Treat underlying disease• Bronchospasm• Sepsis

Sedation and paralytics Adjust ventilator mode Consider “permissive hypercapnia”

Case #3Difficult Oxygenation

54 yom s/partial gastrectomy for adenocarcinoma

PMH: HTN Meds: CardiazemGERD Axid

PSH: RIH repairLipoma excision

SH: ETOH: 1/2 case qdSmoker 1 ppd

CASE #3

POD 0: Admitted to ICUUnremarkable eventsExtubated POD1 and transferred to floor

POD 3: Acute onset of dyspnea, RR25Diaphoretic, mild cyanosis, tachycardiaTransferred to ICU

Initial work-up: ????

Case #3

Initial workup: EKG - normalCXR - RLL infilrateABG 7.50/32/50IntubatedVent SIMV 16/750 ml/100%/PS5

1 hr. later: Sedated, RR 16, SBP 110, HR 110ABG 7.38/42/56/86%

?? Vent changes ??

Case #3

Vent changes: PEEP 5.0 added, no changePEEP 10, drop in COABG 7.32/50/58/88%

What is his diagnosis?

What interventions are available to improve oxgenation?

Unilateral Lung Injury

Increased PEEP• Paradoxically increased shunting• Increased V/Q ratio

• increased in overdistended lung units• increased in ratio of deadspace to tidal volume

Therapeutics for Oxygenation

Unilateral• PEEP appropriately• Sedation• Paralytics

• reduce chest wall tone

• reduces O2 demand

• Lateral position• Differential lung

ventilation (DVL)

Bilateral (ARDS) Same as Unilateral except:

• Prone positioning• No indication for DVL• Consider Jet ventilation• Consider extracorporal

membrane oxygenation (ECMO)

Questions…..?