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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 l.jpg

Using the Ventilator for More Than Mechanical Ventilation

Joseph E. Previtera, RRT

Respiratory Care Department

Beth Israel Deaconess Medical Center

Boston, MA


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  • 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.


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The Problem remain patent.

  • 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


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  • Obtaining the P-V Curve remain patent.

  • 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.


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To remain patent.

Or not to


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1200 remain patent.

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


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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


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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


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R. SCOTT HARRIS, DEAN R. HESS, and JOSÉ G. VENEGAS Am. 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)


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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


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The Problem Distending Pressures in Acute Respiratory Distress Syndrome

  • 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.


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General Approach to Open Lung Technique Distending Pressures in Acute Respiratory Distress Syndrome

  • 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.


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Patient Selection Distending Pressures in Acute Respiratory Distress SyndromePulmonary 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.


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Types of Recruitment Maneuvers Distending Pressures in Acute Respiratory Distress Syndrome

“Conventional”

  • Apneic TLC maneuvers

  • Non-apneic TLC maneuvers

  • Prone positioning

  • Inverse Ratio Ventilation


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Patient Monitoring Distending Pressures in Acute Respiratory Distress Syndrome

  • During recruitment

    • SpO2

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

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

  • After recruitment

    • VT 

    • Oxygenation 


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Apneic Lung Recruitment Technique Distending Pressures in Acute Respiratory Distress SyndromeA “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.


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Non- apneic Lung Recruitment Distending Pressures in Acute Respiratory Distress SyndromeTechnique: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.


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Before recruitment Distending Pressures in Acute Respiratory Distress Syndrome

After recruitment

Effect of Recruitment: CT Scan


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Approaches to Maintain the Recruited Lung Volume Distending Pressures in Acute Respiratory Distress Syndrome

  • Adequate PEEP

  • Prone positioning

  • Sighs


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“Open Lung” Management of ARDS: Ventilator Settings Distending Pressures in Acute Respiratory Distress Syndrome

  • 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


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Management of Maintenance PEEP Distending Pressures in Acute Respiratory Distress Syndrome

  • 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.


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Prone Positioning Distending Pressures in Acute Respiratory Distress Syndrome


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PRONE POSITION in ARDS Distending Pressures in Acute Respiratory Distress Syndrome

For Every Thing (Turn…Turn…Turn…)


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Dorsal Distending Pressures in Acute Respiratory Distress Syndrome

Ventral

Dorsal

Ventral

Mechanism of Prone Positioning


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PRONE POSITION in ARDS Distending Pressures in Acute Respiratory Distress Syndrome

  • Proposed Explanations

  • Increased FRC

  • Blood Flow Redistribution

  • Changes in Diaphragmatic Motion

  • Improved Secretion Removal

Magic


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Prone Positioning: Procedure Distending Pressures in Acute Respiratory Distress Syndrome

  • 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.


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53yo female 1-2 wk flu like syndrome Distending Pressures in Acute Respiratory Distress 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


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Pappert, D, et al. Influence of Positioning on Distending Pressures in Acute Respiratory Distress Syndrome

Ventilation-Perfusion Relationships in Severe ARDS

Chest Nov 1994


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Prone Positioning Distending Pressures in Acute Respiratory Distress SyndromeChatte. Am J Respir Crit Care Med 1997;155:473:478


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Prone Positioning: How Long? Distending Pressures in Acute Respiratory Distress Syndrome

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


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Prone Positioning: Distending Pressures in Acute Respiratory Distress SyndromeClinical 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.


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Prone Positioning: Risks Distending Pressures in Acute Respiratory Distress SyndromeChatte. 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 l.jpg
    The Use of Sighs to Maintain the Open Lung Distending Pressures in Acute Respiratory Distress SyndromePelosi, 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 function pelosi am j respir crit care med 1999 159 872 880 l.jpg
    Effect of Sigh on Lung Recruitment and Function Distending Pressures in Acute Respiratory Distress SyndromePelosi. Am J Respir Crit Care Med 1999;159:872-880.


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    High PEEP Distending Pressures in Acute Respiratory Distress Syndrome

    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


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    Guidelines, Recommendations, & Statements Distending Pressures in Acute Respiratory Distress Syndrome

    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.


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    Open Lung Ventilation Summary Distending Pressures in Acute Respiratory Distress Syndrome

    • 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



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