1

Thom Petty BS RRTVentilation Solutions Specialist – Eastern U.S

vyaire Medical – Ventilationthomas.petty@vyaire.com

• Do you utilize PEEP while managing your ventilator? • How do you determine just how much PEEP is actually needed to

prevent injury from cyclical de-recruitment/re-recruitment ?

• Do you measure Pplat during routine Patient/Ventilator Assessments?• Does that airway Pplat truly reflect the strain experienced inside

the alveoli?

• How do you determine how hard your patient is working to breathe?

• What effect do your efforts to determine these important factors have on your VLOS? • Especially with your fourth-quartile VLOS patients.

2

SO, WHAT’S SOBAD ABOUT

• The physics of PPV differs radically from the physics of spontaneous ventilation. • Positive intra-thoracic pressures during PPV inhalation

• Flow is distributed heterogeneously throughout the lung• Effectively distributed through compliant regions of the lung

• “Healthy” regions are over-distended• Attenuated in low-compliant regions of the lung

• “Injured” regions are under-distended

• Damage caused by this over & under-distension is termed Ventilator-Induced Lung Injury (VILI)

3

• 2013 – Biehl- Respir Care; 58(6): 927–934

• VILI = injury to the blood-gas barrier in the lung secondary to mechanical ventilation

• Initial stretch of blood-gas barrier: • Leakage of protein into the interstitial space

• Subsequent stretch of blood-gas barrier:• Leakage of protein into alveolar space

4

• DEFINITION: • 2012 – Ronchi - J Pulmon Resp Med; S:12

• Excessive Vt → alveolar stretch • → alveolar-capillary barrier damage

• → rapid ↑ in capillary permeability.

• May be indicated by excessive PPLAT

• May result from a combination of PEEP + Vt

• QUESTION: How can a clinician determine if an elevated airway Pplat accurately indicates alveolar volutrauma?

• DEFINITION: • 2003 – Bilik – J Appl Physiol; 94.2: 770-783.

• Repeated cyclical de-recruitment/re-recruitment of small airways/lung units • Abrasion of the epithelial airspace lining• Worsens surfactant dysfunction• Instigates the release of inflammatory mediators into alveolar

spaces and into the systemic circulation

• QUESTION: How can the clinician determine what PEEP is truly necessary to prevent cyclical de-recruitment/re-recruitment?

5

• DEFINITION: • 2012 – Rachmale - Respir Care; 57(11):1887–1893.

• In patients requiring mechanical ventilation, prolonged high FIO2:• Worsens gas exchange• Decreases ciliary efficacy• Produces hyperoxic bronchitis and atelectasis

• DEFINITION:• 2012 – Ronchi - J Pulmon Resp Med; S:12

• Excessive transpulmonary pressure in the alveoli leading to alveolar epithelial damage• Conduction of air into the interstitial space

• Pneumothorax• Pneumomediastinum• Pneumopericardium• Subcutaneous emphysema

6

• DEFINITION:

• DPRS = PPLAT – PEEP

• 2015 – Amato – NEJM ;372:747-55.

• Retrospective analysis of the ARMA study:• Vt, Pplat and PEEP had no correlation with mortality• Driving Pressure (DPRS) did correlate with ↑ mortality

• Even in patients receiving low-volume lung-protective ventilation

• May be a superior marker of VILI

7

LUNG-PROTECTIVEVENTILATION

• 2013 – Mireles-Cabodavila - Respir Care; 58(2): 348 –366• The Three Goals of Lung Protective Ventilation:

• Provide gas exchange safely• Primum non nocere

• Provide comfort

• Promote liberation from the ventilator

8

Tidal Volume Accurately measured

Respiratory RateAccurately measured

FiO2 Accurately measured

PEEPMeasured but may not accurately

reflect physiology

Plateau PressureMeasured but may not

accurately reflect physiology

9

Plateau PressureMeasured but may not accurately reflect physiology

• DEFINITION:

• PPLAT is the static pressure that exerted by the volume of gas in the lungs at the end of an inhalation.

• Indicator of “lung-fullness”

• ARDSNet recommendations:• Check PPLAT:

• At least q 4h (min 0.5 sec inspiratory pause)• After each change in PEEP or VT (min 0.5 sec inspiratory pause)

10

• 1993 – Slutsky – Chest; 104:1833-59• ACCP Consensus Conference Recommendation• Maintain PPLAT < 35cm H2O

• 2005 – Hager – AJRCCM; 172.10: 1241-1245.

• ↑mortality in ARDS pts with day-1 PPLAT > 26–28 cm H2O

• 2007 – Malhotra – NEJM; 357(11): 1113–1120• Allow PPLAT >30cmH2O in patients with elevated pleural pressures as

transpulmonary pressures may not be elevated

• QUESTION: How can a clinician determine if an elevated Airway Pplat accurately indicates alveolar volutrauma?

11

PEEPMeasured but may not accurately reflect physiology

• DEFINITION:

• PEEP is the static pressure exerted by the volume of gas that is remaining in the lungs at the end of exhalation

• This end-expiratory volume is known as • FRC – Functional Residual Capacity• EELV – End-Expiratory Lung Volume

12

• Optimal PEEP is defined as:• High enough to induce alveolar recruitment while not distending

“healthy” alveoli• Low enough to prevent hemodynamic impairment &

overdistension

• Optimal Lung-Protective PEEP remains difficult to determine.• Potential adverse consequences including circulatory depression

and lung overdistension may outweigh the benefits of higher PEEP’s

• Use of PEEP < 10cmH2O leads to an increase in mortalityAmato M., 8th World Congress, Sydney, Australia

PEEP TABLETable of FiO2 & PEEP combinations to achieve PaO2 or SpO2 in target range

MAXIMAL PEEP WITHOUTOVERDISTENSION

Use of highest PEEP while maintaining Pplat < 30 cmH2O

GAS EXCHANGELowest shunt (highest PaO2), lowest deadspace (lowest PaCO2), best oxygen delivery (CaO2 x C.O.)

COMPLIANCEUse of the highest PEEP that results in the highest respiratory-system compliance

STRESS INDEXObserve the Pressure/Time Curve during constant flow inhalation for signs of tidal recruitment and overdistension

PRESSURE/VOLUME CURVE Set PEEP slightly higher than Lower Inflection Point

IMAGINGComputed tomography, Electrical impedence tomography, Ultrasound

ESOPHAGEAL PRESSUREMONITORING

Estimate the intra-pleural pressure with the measurement of Esophageal Pressure then determine optimal PEEP

13

• QUESTION: How can the clinician determine what PEEP is truly necessary to prevent cyclical de-recruitment/re-recruitment?

AIRWAY & PLEURAL & TRANSPULMONARYPRESSURES, OH MY!

14

AIRWAY PRESSURE (PAW) • Measured at the circuit wye or ventilator outlet• Reflects both lung and pleural pressures

PERI-PULMONARY/PLEURAL PRESSURE (PES) • Pressure imposed upon the lungs by the chest

wall and abdomen• Can be approximated by measuring pressures

within the Esophagus

TRANSPULMONARY PRESSURE (PTP)• The true pressure within the lung

• PTP = PAW – PES

Paw

Pes Ptp

• 2016 – Sahetya - Curr Opin Crit Care; 22(1): 7–13.

• During PPV, airway pressure distends the lung and the chest wall in series.

• Chest wall edema, kyphoscoliosis, and intra-abdominal hypertension are usually associated with ↑ in pleural pressure

• Depending on the pleural pressure, the same measured Airway Pressure can be associated with considerably different PTP• Considerably different implications for injury to the lung.

15

• 2016 – Sahetya - Curr Opin Crit Care; 22(1): 7–13

Abdominal Pressure

Total Prevalence

MICU Prevalence

SICU Prevalence

>12 mmHg 58.8% 54.4% 65%

>15 mmHg 28.9% 29.8% 27.5%

>20 mmHg 8.2% 10.5% 5.0%

• 2004 – Malbrain – Int Care Med; 30:822-829• 97 patients in 13 ICU’s in 8 countries

16

• 2008 – Talmor – NEJM; 359.20 (2008): 2095• Retrospective analysis of data from ARDS patients• Baseline Pes = 17.2 cmH2O (+ 4.4)

• 2010 – Behazin - J Appl Physiol 108: 212–218• Obese patients (BMI 38-80)

• Baseline Pes = 12.5 cmH2O (+ 3.9) cmH2O• Normal patients (BMI <30)

• Baseline Pes = 6.9 cmH2O (+ 3.9)

• 2018 – Murphy – Crit Care Med; 46(6): 958-964• 285 patients in medical and surgical ICU’s

• 30% of both surgical and non-surgical pts diagnosed with intra-abdominal hypertension on admission

• Additional 15% of surgical and non-surgical pts developed intra-abdominal hypertension during admission.

• “Intra-abdominal hypertension is more common than thought”

17

• To know true pressure inside of the lung (Ptp) you must account for the pressures outside of the lung (Pleural Pressures)

• Difficult to directly measure Pleural pressure but numerous studies have demonstrated reasonable correlation between Esophageal Pressures and Pleural Pressures

• 2017 – Kassis – Med Klin Intensivmed Notfmed; 113(Supp 1):513-520• Esophageal manometry simplifies the estimation of pleural

pressures• Despite the extensive use of esophageal manometry in research,

clinical adoption has been less universal.

TRANSPULMONARYPRESSURE-GUIDEDVENTILATION

18

• 2008 – Talmor – NEJM; 359.20 (2008): 2095.• Problem: Optimal PEEP remains difficult to determine.

• Hypothesis: Could Esophageal Pressure measurements enable the clinician to determine a PEEP value that would maintain oxygenation while preventing lung injury due to repeated alveolar collapse and/or overdistention?

• Mechanically-ventilated ARDS patients randomly assigned to groups:• CONTROL GROUP:

• PEEP adjusted as per ARDSNet recommendations• PES-GUIDED GROUP:

• PEEP adjusted to achieve a PTP PEEP of 0 to+10 cmH2O

• 2008 – Talmor – NEJM; 359.20 (2008): 2095.• Problem: Optimal PEEP remains difficult to determine.

• Hypothesis: Could Esophageal Pressure measurements enable the clinician to determine a PEEP value that would maintain oxygenation while preventing lung injury due to repeated alveolar collapse and/or overdistention?

• Mechanically-ventilated ARDS patients randomly assigned to groups:• CONTROL GROUP:

• PEEP adjusted as per ARDSNet recommendations• PES-GUIDED GROUP:

• PEEP adjusted to achieve a PTP PEEP of 0 to+10 cmH2O

19

• 2008 – Talmor – NEJM; 359.20 (2008): 2095.• Primary end point: improvement in oxygenation.• Secondary end point: respiratory-system compliance & pt outcomes.

• The study reached stopping criterion and was terminated after 61 patients had been enrolled.

• The PaO2/FiO2 ratio at 72 hours was 88 mmHg higher in the Pes-group than in the control group

• This effect was persistent through 24, 48 & 72 hr follow-up time.

• Respiratory-system compliance was also significantly improved at 24, 48, and 72 hours in the Pes-guided group

• 2008 – Talmor – NEJM; 359.20 (2008): 2095.

20

WHAT’S IN THE JOURNALS

• Increases in Peak Airway Pressure without a concomitant increase in alveolar distension (↑ Ptp) are unlikely to cause damage• Critical variable is not PIP but Ptp

• In pts with a stiff chest wall from non-pulmonary ARDS that may have elevated pleural pressures, airway Plateau Pressures may exceed 35cmH2O without causing alveolar distension

! Esophageal pressure can be used to estimate transpulmonary pressures

A SAMPLING OF WHAT’S IN THE JOURNALS

21

! Systematic use of Pes has the potential to improve ventilator management in ARF by providing more direct assessment of lung-distending pressure

A SAMPLING OF WHAT’S IN THE JOURNALS

! Using Airway Plateau Pressures to set ventilation may under-ventilate patients with intra-abdominal hypertension and over-distend the lungs of patients with atelectasis.

! Ptp must be used to accurately set mechanical ventilation in the critically ill.

A SAMPLING OF WHAT’S IN THE JOURNALS

22

! Utilizing Pes for PEEP titration results in ↑ elastance and ↓ driving pressures compared to conventional PEEP titration.

A SAMPLING OF WHAT’S IN THE JOURNALS

! Pplat > 25 cmH2O! Cstat < 40 ml/cmH2O! P/F Ratio < 300! PEEP > 10 cmH2O to maintain SaO2 > 90%! PaCO2 > 60 mmHg or pH < 7.2 attributable to respiratory acidosis

23

! 5fr or 7fr balloon-tipped catheter or a specialized 16fr NG/OG catheter with balloon tip

! Inserted into the lower third of the esophagus, above the diaphragm.

! An approximation of proper placement can be made by measuring the distance from the tip of the nose to the bottom of the earlobe and then from the earlobe to the distal tip of the xiphoid process of the sternum.

24

• Baydur Maneuver:• During a patient-initiated breath during an expiratory hold a

properly positioned inflated balloon will show simultaneous negative Paw & Pes deflections

• If balloon is inserted too far into the esophagus Pes will deflect positively during a spontaneous inspiration.

• PES should be similar (+ 10) to PGA (Bladder Pressure)• Measurements should match the patients clinical presentation.

• Cardiac Oscillations:• A properly inserted inflated balloon may show small cardiac

oscillations reflective of cardiac activity.• May need to re-scale Y-axis of waveform to visualize

25

! ↑ pleural pressure skews the airway Pplat upwards

! PAW PLAT = 39 cmH2O! PES = 30 cmH2O! PTP PLAT = 9 cmH2O

! Keep PTP PLAT < 20 cmH2O

• PAW PEEP = 5 cmH2O• PES = 15 cmH2O• PTP PEEP = -10 cmH2O

15

5

-1015

15

26

! Adjust PEEP to maintain a PTP PEEPof 0 - +2.0 – 5.0 cmH2O

! Negative PTP PEEP indicates pressure outside the lung is greater than pressure inside the lung.

! Positive PTP PEEP indicates pressure inside the lung is greater than pressure outside the lung

! Excessive PTP PEEP may cause end-expiratory overdistension

• The difference between PEAK esophageal pressure (PPEAK ES ) and BASELINE esophageal pressure (PPEEP ES)

!!!! PES = PPEAK ES – PPEEP ES

• Good indicator of Work of Breathing• <15 cmH2O may indicate patient is a good candidate for weaning.

• Adult Normal: 10 – 15 cm H2O• Pediatric Normal: 7 – 19 cm H2O

27

• 2017 – Kassis – Med Klin Intensivmed Notfmed; 113(Supp 1):513-520

• Prevention of lung collapse in ARDS

• Limit cyclical and total stress to prevent VILI and overdistension

• Assessment of patient/ventilator synchrony and spontaneous efforts

• Assessment of efficacy of recruitment maneuvers

• 2017 – Kassis – Med Klin Intensivmed Notfmed; 113(Supp 1):513-520

• Intrinsic PEEP measurement• Overcoming PEEPi requires ↑ WOB with every spontaneous breath

• Significant cause for dyspnea and muscle fatigue• Pes is the most accurate method to measure PEEPi

• Can be used in spontaneously breathing patients

• Weaning from the ventilator

28

29

• CXR on current vent settings:• Any heart silhouette?• Any diaphragms?• Any aeration?

• Esophageal Balloon inserted • Initial PTP PEEP = -12.3 cmH2O

• REMEMBER: a negative PTP PEEPindicates the lung is being derecruited from an elevated pleural pressure

! Placed onto:

! PC/AC! RR 16! PIP 36! PEEP 20

! PTP PEEP now -3.7 cmH2O

FIRST THOUGHT - PUMP UP THE PEEP

30

• PAW PLAT

• 41 cmH2O

• PTP PLAT

• 21 cmH2O

WHICH PPLAT IS CORRECT?

• PEEP ↑ to 25 cmH2O

• Ptp PEEP now +2.4 cmH2O• De-recruitment addressed

FURTHER PEEP PUMPAGE

31

• PLOW 0 cmH2O• TLOW 0.8 sec• IMMEDIATE Derecruitment!

• PTP PEEP -15 cmH2O

! Returned to PC/AC with PEEP of 25

! PTP PEEP now +2.4 cmH2O! No derecruitment!

! PAW PEAK of 46 cmH2O! PTP PEAK of 27 cmH2O

! Physicians were hesitant to maintain PEEP of 25

32

! CXR six-day post PEEP adjustment using PES monitoring

! PEEP = 16cmH2O! FiO2 of .40

! Heart border & diaphragms visible

33

• Pre-Instillation• PTP PEEP = +2 cmH2O• No Derecruitment

• Post-Instillation• PTP PEEP = -2 cmH2O• Derecruitment on

PEEP of 4

• PEEP increased to 8 cmH2O

• PTP PEEP increased to +1.2 cmH2O

34

CHANGES FOLLOWING

RESUSCITATIVE FLUID BOLUS

• Following multiple fluid boluses during resuscitation it was noticed that PES increased from 8 cmH2O to 12 cmH2O

• PTP PLAT increased to 27 cmH2O

• PEEP immediately increased to 10 cmH2O

• This kept PTP PEEP from dropping into negative

• No “Post-Code Derecruitment”

Email: thomas.petty@vyaire.com