The Many Disguises of PEEP: Case Presentations Bradley J. Phillips, MD Burn-Trauma-ICU Adults & 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 O 2 Increases cardiac output Increases lung compliance Worsens O 2 Decreases cardiac output Barotrauma Fluid retention Intracranial HTN CO 2 clearance

Gas Exchange O 2 PEEP I:E alterations Positioning * Prone/Lateral Rate Tidal volume I:E alternations

Intubation Criteria Airway protection RR > breaths/min PaCO 2 > 55 mmHg ( acute) PaO 2 < 70 mmHg on 100% O 2 nonrebreather A-a gradient> 400 mmHg on 100% O 2 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 #2 CO2 Retention 67 yom s/p radical neck dissection for tumor of posterior pharynx PMH: COPD - steroid x 3 years CAD s/p IWMI 8yrs ago PSH:CABG x3 5 years ago SH:Beer - 4-5/day Smoker ppd

Case #2 Uncomplicated procedure, admitted to ICU for mechanical ventilation PE:elderly appearing, surgical wound on neck, JP x1 old scar on sternum, S2 loud breath sound quiet scaphoid abdomen LAB:WBC 14.2, Hct 25% CXR: Hyperinflated lung o/w clear

Case #2 Initial tx :ABX per ENT(clindamycin) Albuterol inhaler IV steroids POD2 :Extubated Tube feedings started POD3:Dyspnea, RR 30/min Crackles at right base, wheezing bilaterally ABG:pH 7.21, P a CO 2 74, P a O 2 FiO 2 0.6

Case #2 ABCs - Intubated CXR - right sided infiltrate in lower and apical fields Diagnosis: ? Initial vent setting: SIMV 12/TV 650ml/FiO 2 1.0/Peep 5 Agitated, BP 220/120, HR 120, RR 40 Peak airway pressures cmH 2 O Diagnosis and tx: ?

Case #2 Sedated with midazolam (Versed) drip 1 hr later :unresponsive rapid breathing, out of phase with ventilator PAP = 70 mmH 2 O Therapy : ? 1 hr later:PAP 35 cm H 2 O FiO 2 decreased to 0.6 with O 2 sats 96% ABG: 7.36/50/94

Case #2 Evening:Desats 90% Wheezing in all fields, crackles r base CXR: new left patchy infiltrate ABG: 7.34/56/68 - Vent setting changed ??? 90mins: ABG PaCO 2 decreased, PaO 2 increased 3 hrs later:Desat 93%, no ABG Vent setting changed ??? ABG: 7.34/58/64 Vent setting changed ??? ABG: 7.30/62/63, PAP 50 mmH 2 O

Case #2 Vent changed - FiO 2 1.0, PEEP 20 cm H 2 O ABG 7.24/68/61 Vent changed- ??? Parameter BP 132/80 to 94/54 Arterial sats 80s CXR/EKG ordered Dopamine started ABG 7.10/84/52 VT - CPR started

Case #2 Trap:PEEP applied to the ventilator auto-PEEP developed by increased RR Results: Difficulty with CO2 elimination Trick: Limit PEEP and assess for auto-PEEP Reduce 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 CO 2 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 (Direct compression)

Case #1 75 yof s/p colostomy for perforated diverticulum PMH: Asthma - inhalersMeds: Albuterol DM - 10 yearsAtrovent PSH: none SH: no EtOH or Tobacco use

Case #1 Hypotension Transferred to ICU for sepsis and ventilator management PE: ill appearing, pale, obese female mild dyspnea T 39 HR 120, SBP 90, RR 30, sats 92%, wt 80kg Lungs: few wheezes bilateral CV:normal S1,S2 Abd: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 (ABCs) :Intubate Vent AC 12/800/80%/PEEP5 NPO/IVF/NGT/ABX Inhalers tx. Dopamine qtt Replete K After intubation:SBP 80s briefly then 95 ABG: 7.32/48/70/96%

Case #1 Vent changes:Increased vent rate ABG: 7.36/42/65/94% 2 hrs later:Agitated, RR 25, sats 88% ABG7.46/32/58 ? Vent changes or therapeutic interventions

Case #1 Vent changes:Increased PEEP 10 ABG 7.50/28/60/90% ? Vent changes or therapeutic maneuvers? 4 hrs post op : VS: HR 130s, BP 85/60, RR30, sats 85% Whats 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 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 #3 Difficult Oxygenation 54 yom s/partial gastrectomy for adenocarcinoma PMH: HTNMeds: Cardiazem GERDAxid PSH: RIH repair Lipoma excision SH: ETOH: 1/2 case qd Smoker 1 ppd

CASE #3 POD 0:Admitted to ICU Unremarkable events Extubated POD1 and transferred to floor POD 3:Acute onset of dyspnea, RR25 Diaphoretic, mild cyanosis, tachycardia Transferred to ICU Initial work-up:????

Case #3 Initial workup:EKG - normal CXR - RLL infilrate ABG 7.50/32/50 Intubated Vent SIMV 16/750 ml/100%/PS5 1 hr. later:Sedated, RR 16, SBP 110, HR 110 ABG 7.38/42/56/86% ?? Vent changes ??

Case #3 Vent changes:PEEP 5.0 added, no change PEEP 10, drop in CO ABG 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 O 2 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…..?