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Using the Ventilator for More Than Mechanical Ventilation. Joseph E. Previtera, RRT Respiratory Care Department Beth Israel Deaconess Medical Center Boston, MA. The lung in ARDS has three components: Diseased lung that is not recruitable Diseased lung that is recruitable Normal lung.

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Using the Ventilator for More Than Mechanical Ventilation

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Using the Ventilator for More Than Mechanical Ventilation

Joseph E. Previtera, RRT

Respiratory Care Department

Beth Israel Deaconess Medical Center

Boston, MA


  • The lung in ARDS has three components:

  • Diseased lung that is not recruitable

  • Diseased lung that is recruitable

  • Normal lung


  • In severe cases of ARDS, no more that 1/3 of all alveoli remain patent.

  • Large tidal volumes may subject the healthy lung to over-distention and inhibition or inactivation of surfactant

  • Intense shear forces develop at the junctions of the aerated and non-aerated lung units

  • The adherent walls of the collapsed small airways often require sustained high pressures to open, but when opened, lower pressures are required to maintain lumenal patency.


The Problem

  • Atelectasis is bad.

  • Over inflation is bad.

  • Alveolar collapse on exhalation is bad.

  • The ARDS lung is not uniform.

  • High PEEP is scary.

  • Auto-PEEP is evil.

VILI


  • Obtaining the P-V Curve

  • Pre-oxygenate

  • Record vent settings & signs

  • Review alarm settings (Apnea setting)

  • Set resp. rate to 5 bpm

  • Set PEEP to 0

  • Adjust peak flow

  • Change tidal volume (alternate small-large)

  • Set plateau for 1-2 sec. interval

  • Record plateau pressure

  • Return to previous vent settings and wait 1 min.


To

Or not to


1200

Static

P-V Curve Technique

1000

800

volume (mL)

600

400

200

0

0

10

20

30

40

pressure (cm H

O)

pressure

manometer

2

calibrated

syringe

100 % O2

patient

filter


  • The LIP represents the critical opening pressure of a large

  • number of alveoli

  • The UIP reflects the loss of elastic properties of the lung due

  • to overdistention


Lung Vol.

Exhalation

Inspiration

Pres.

PEEP

B

A

Rimensberger et al: The open lung during small tidal volume ventilation: Concepts of recruitment and “optimal” PEEP Crit Care Med; 1999; 27: 1946-1952


Issues with PV Curves

  • Requires sedation and/or paralysis to measure

  • Difficult to identify “inflection points”

  • May require esophageal pressure to separate lung from chest wall effects

    • Mergoni et al, AJRCCM 1997;156:846-854

    • Ranieri et al, AJRCCM 1997;156: 1082-1091

  • Deflation limb may be more useful than inflation limb

    • Holzapfel et al, Crit Care Med 1983; 11: 561-597

  • Pressure-volume curves of individual lung units not known


R. SCOTT HARRIS, DEAN R. HESS, and JOSÉ G. VENEGASAm. J. Respir. Crit. Care Med., Volume 161, Number 2, February 2000, 432-439

“There was significant interobserver variability in Pflex, with a maximum difference of 11 cm H2O for the same patient (SD = 1.9 cm H2O)


Beneficial Effects of the “Open Lung Approach” with Low Distending Pressures in Acute Respiratory Distress Syndrome

Amato et. Al. Am. J. Respir. Crit. Care Med., Volume 152, pp 1835-1846. 1995


The Problem

  • Atelectasis is bad.

  • Over inflation is bad.

  • Alveolar collapse on exhalation is bad.

  • The ARDS lung is not uniform.

  • High PEEP is scary.

  • Auto-PEEP is evil.


  • How much PEEP is needed to recruit the lung?

  • How much PEEP is needed to maintain the lung?


General Approach to Open Lung Technique

  • Recruit the lung by applying a plateau pressure that can inflate the lung to TLC.

  • Provide the recruitment pressure for an adequate period of time.

  • Maintain the lung by not allowing the lung to derecruit on exhalation.

  • Coming down to the maintenance PEEP level achieves higher lung volumes than titrating up to the maintenance PEEP level.


Patient SelectionPulmonary vs. Extra-Pulmonary ARDS:Gattinoni, Am J Respir Crit Care Med 1998;158:3-11

  • Pulmonary ARDS (ARDSP)

    • Largely consolidation

    • Little atelectasis

      • i.e. pneumonia, aspiration, diffuse pulmonary infection, near-drowning, toxic inhalation, lung contusion, etc

  • Extra-pulmonary ARDS (ARDSEX)

    • Predominately atelectasis

      • i.e. sepsis, nonthoracic trauma, pancreatitis, transfusion related injury, etc.


Types of Recruitment Maneuvers

“Conventional”

  • Apneic TLC maneuvers

  • Non-apneic TLC maneuvers

  • Prone positioning

  • Inverse Ratio Ventilation


Patient Monitoring

  • During recruitment

    • SpO2

    • BP: MAP  60 mm Hg or < 20 mm Hg 

    • HR: > 60 & < 140; no arrhythmia's

  • After recruitment

    • VT 

    • Oxygenation 


Apneic Lung Recruitment TechniqueA “Conservative” Approach?

  • Sedation ?

  • Pre-oxygenation.

  • CPAP of 30 cm H2O for 30 - 40 seconds.

  • Monitor Vt and oxygenation for 15 - 30 min.

  • If unresponsive, repeat at CPAP of 35 to 40 cm H2O.


Non- apneic Lung RecruitmentTechnique:An “Aggressive” Approach?

  • PCV of 10 - 20 cm H2O.

  • RR = 10 b/min.; I:E ratio = 1:1.

    • 3 second IT.

  • PEEP 20 - 40 cm H2O.

  • Apply for 45 sec. to 2 min.

  • Monitor Vt and oxygenation for 15 - 30 min.

  • If unresponsive, repeat at higher PEEP.


Before recruitment

After recruitment

Effect of Recruitment: CT Scan


Approaches to Maintain the Recruited Lung Volume

  • Adequate PEEP

  • Prone positioning

  • Sighs


“Open Lung” Management of ARDS: Ventilator Settings

  • Pressure control ventilation

  • Tidal volume  6 mL/kg and Pplat  35 cm H2O

  • PEEP 10 - 20 cm H2O

    • Usually  15 cm H2O but sometimes higher

  • FiO2  0.60 (if possible)

  • Rate 15 - 25/min (avoid auto-PEEP)

  • IT 1.5 - 2 s (avoid auto-PEEP)

  • Permissive hypecapnia

  • Recruitment maneuvers

    • repeat after each circuit disconnect and as needed.

  • Prone position


Management of Maintenance PEEP

  • Reduce FiO2 to  0.60.

  • Maintain PEEP at lowest level that achieves adequate oxygenation.

  • Repeat recruitment maneuver if PEEP reduction compromises oxygenation.

    • Reset PEEP at previous effective level.


Prone Positioning


PRONE POSITION in ARDS

For Every Thing (Turn…Turn…Turn…)


Dorsal

Ventral

Dorsal

Ventral

Mechanism of Prone Positioning


PRONE POSITION in ARDS

  • Proposed Explanations

  • Increased FRC

  • Blood Flow Redistribution

  • Changes in Diaphragmatic Motion

  • Improved Secretion Removal

Magic


Prone Positioning: Procedure

  • Appropriate staff to manage patient and “tubes”.

    • 2 - 3 for Airway, IV’s, chest tubes, etc.

    • 2- 3 for pt.

  • Minimize abdominal pressure.

    • Support hips/chest with pillows or deflate abdominal portion of “air bed”.

  • Maintain pt in Swimming position (one arm extended over head, head turned to that side)

    • Alternate head/arm Q2o hrs..

  • Sedation generally required.


53yo female 1-2 wk flu like syndrome

Went to ER unable to breathe 3/18

Intubated in outside hospital

Gram + cocci blood/sputum - Strep A

Brought to BIDMC 100%, levo, dopa, supine

Immediately returned to proned

7.22 46 56 TCPCV 18/15 * 18 .50 1:1.5

3/29 “Pt tolerated supine position for 3 hours today, O2 sats decreased and pt returned to prone position”. 20/15 * 22 .5 7.37 55 88 Vt 500mls


Pappert, D, et al. Influence of Positioning on

Ventilation-Perfusion Relationships in Severe ARDS

Chest Nov 1994


Prone PositioningChatte. Am J Respir Crit Care Med 1997;155:473:478


Prone Positioning: How Long?

Fridrich et al, Anesth Analg 1996;83:1206-1211


Prone Positioning:Clinical ConsiderationsChatte. Am J Respir Crit Care Med 1997;155:473:478

  • Duration of proning may need extending.

  • Increased attention to skin lesions required.

    • Dependent edema resolves in supine position.

  • 2 - 4+ personnel required to turn pt.

  • Special beds not required:

    • Avoid stiff support; especially under abdomen.

  • Sedation is usual but not mandatory.

  • Optimum mode of ventilation is unclear.


Prone Positioning: RisksChatte. Am J Respir Crit Care Med 1997;155:473:478

2/32 pts were intolerant of position alteration

  • decreased SpO2 of > 5%.

    6/32 pts (19%); 294 prone periods (2%)

  • 2 instances of apical atelectasis.

  • 1 catheter removal.

  • 1 catheter compression.

  • 1 extubation.

  • 1 transient SVT episode.

  • Minor skin injury and edema.


  • The Use of Sighs to Maintain the Open Lung Pelosi, et al. A,J Respir Crit Care Med 1999; 159:872-880.

    • 3/hr. at a Vt which produces a Pplat of 45 cm H2O.

    • May open units with opening pressures > than 35 cm H2O.

    • May resolve absorption atelectasis in poorly ventilated units.


    Effect of Sigh on Lung Recruitment and FunctionPelosi. Am J Respir Crit Care Med 1999;159:872-880.


    High PEEP

    Barotrauma

    Hypotension

    Reduced cardiac output

    Increased pulmonary vascular resistance

    Impaired RV function

    Permissive Hypercapnia

    Pulmonary vasoconstriction

    Myocardial depression

    Cerebral vasodilatation

     risk of hemodialysis

     need for sedation or paralysis

    Complications of Open Lung Ventilation


    Guidelines, Recommendations, & Statements

    accp consensus conference

    Mechanical Ventilation*

    Chairman: Arthur S. Slutsky, M.D., F.C.C.P.

    Chest 1993; 104:1833-59

    • We recommend that when plateau pressures are  35 cmH2O, that the VT can be decreased to as low as 5 ml/kg, or lower.

    • To accomplish the goal of limiting plateau pressure, PaCO2 should be permitted to rise (permissive hypercapnia) unless the presence or risk of raised ICP contraindicates.


    Open Lung Ventilation Summary

    • Treatment of atelectasis, derecruitment and over distension in ARDS require careful planning.

    • Best RM techniques may vary for different patients.

    • Maintenance PEEP is difficult to determine in advance.

    • Low VT seems safer but some data conflicts:

      • Brower, CCM 1999; Brochard, AJRCCM 1998; Stewart, NEJM 1998

      • Amato, AJRCCM 1995; Amato, NEJM 1998; ARDS Network 1999


    Make a note of this Muldoon…The wounds seem to be caused by bird shot…Big Bird Shot!


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