MECHANICAL VENTILATION

1
MECHANICAL VENTILATION
R. Duncan Hite, M.D. Associate Professor of
Internal Medicine Section on Pulmonary and
Critical Care Medicine
2
(No Transcript)
3
OBJECTIVES
Mechanics of Ventilators Weaning (Liberation)
from Mechanical Ventilation Non Invasive
Mechanical Ventilation (NIPPV)
4
Respiratory Failure
Hypoxic Respiratory Failure Hypercarbic
Respiratory Failure
?
5
VENTILATION
Physical Parameters of Ventilation Pressure Vol
ume Flow
6
VENTILATION

• Negative Pressure
• Spontaneous
• Mechanical
• Positive Pressure
• Mechanical
• Invasive
• Non Invasive (CPAP, BiPAP)

7
MECHANICAL VENTILATION Ventilation Modes
Volume-Cycled (Vt fixed, P variable) Assist
Control (AC, CMV) Intermittent Mandatory
Ventilation (IMV, SIMV) Pressure-Cycled (P
fixed, Vt variable) Pressure Support
(PSV) Pressure Control (PCV) Airway Pressure
Release (APRV)
8
MECHANICAL VENTILATION Ventilation Modes
MacIntyre, Chest, 1993, 104, 560.
9
COMPLIANCE
Compliance ?V/?P
Dynamic Vt/PIP-PEEP
Key physiologic variables Lung
Compliance Chest Wall Compliance Airway
Resistance
Static Vt/Pplat-PEEP
10
MECHANICAL VENTILATION Nomenclature
11
MECHANICAL VENTILATION Triggering
12
MECHANICAL VENTILATION Respiratory Rate
Assist Control Set rate sets time
duration for ventilator to give breath if not
triggered by patient. Possible for no breath
to be given without patient triggering
All breaths are preset tidal volume
SIMV Set rate sets time interval during which
assisted breath must be given with or without
patient triggering Preset tidal volume only
provided during assisted breaths. Vt for other
breaths are spontaneous or PSV-assisted.
PSV NO set rate. Preset pressure provided
during all breaths. PCV Able to set rate,
same as AC. Preset pressure provided for all.
13
MECHANICAL VENTILATION SIMV
14
Terminology of PEEP
Extrinsic (i.e. Machine generated)
15
(No Transcript)
16
Terminology of PEEP
Extrinsic (i.e. Machine generated) PEEP
CPAP Intrinsic autoPEEP Obstructive lung
disease - air trapping Mechanical (Inverse
Ratio Ventilation)
17
Prolonged Inspiration/Intrinsic PEEP
18
Terminology of PEEP
Extrinsic (i.e. Machine generated) PEEP
CPAP Intrinsic autoPEEP Obstructive lung
disease - air trapping Mechanical (Inverse
Ratio Ventilation) Physiologic (?)
19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
Amato, etal. Am J Respir Crit Care Med, 1995,
152, 1835.
23
Low Volume Ventilation Strategy ARDS
ARDS Network, NEJM, 2000,342,1301.
24
Low Volume Ventilation Strategy ARDS
ARDS Network, NEJM,2000,342,1301.
25
Permissive Hypercapnea

• Management Issues
• Cardiovascular
• Reduced Myocardial Contractility
• Pulmonary Vasoconstriction
• Systemic Vasoconstriction (increased afterload)
• Central Nervous System
• Anesthetic
• Increased Intracranial Pressure
• Cerebral Vasodilation
• Musculoskeletal
• Reduced Contractility
• Endocrine

Hickling, etal. Crit Care Med, 1994,22,1568.
26
Weaning Guidelines
27
Weaning (Extubation) Parameters

• Parameters
• Strength
• MIP (lt -20 cmH2O)
• VC (gt 10 cc/kg)
• Vt (gt 5 cc/kg)
• Demand
• Ve (lt 10 Lpm)
• RR (gt 30 bpm)
• Combined
• f/Vt (lt 105 bpm/L)

28
Weaning (Extubation) Parameters
Hilberman, etal. J Thor Cardiovasc Surg, 1976,
71, 711.
29
Weaning (Extubation) Parameters
Yang, Tobin. NEJM, 1991, 324, 1445.
30
Modes of Ventilation for Weaning
Volume-Cycled (Vt fixed, P variable) Assist
Control (AC, CMV) Synchronized Intermittent
Mandatory Ventilation (SIMV) Pressure-Cycled
(P fixed, Vt variable) Pressure Support
(PSV) Pressure Control (PCV) Airway Pressure
Release (APRV)
31
Comparison of Weaning Modes
SIMV v. PSV?? PSV - more patient comfort,
requires more observation SIMV - less apnea
alarms!
Esteban,etal. NEJM, 1995, 332, 345.
32
Impact of Daily Screen at NCBH
Ely, etal. N Engl J Med, 1996, 335, 1864.
33
MECHANICAL VENTILATION Spontaneous Breathing
Trials
Modes AutoFlow or Flowby PSV 5
T-Piece Trial Duration 30 - 120 min
Esteban,etal. Am J Resp Crit Care Med, 1999, 159,
512.
34
(No Transcript)
35
Non Invasive Ventilation

• PEEP CPAP
• BiPAP CPAP PSV modes
• ePAP CPAP
• iPAP CPAP PSV

36
Non Invasive Ventilation

• Clinical Indications
• Hypercarbic Respiratory Failure
• COPD Exacerbation
• BiPAP
• OSA / Obesity Hypoventilation
• Neuromuscular Disease
• Hypoxic Respiratory Failure
• Cardiogenic Pulmonary Edema
• CPAP (?BiPAP)
• Other ??

Mehta, Hill. Am J Respir Crit Care Med, 2001,
163, 540.
37
Non Invasive VentilationPatient Selection

• Predictors of Success
• Younger Age
• Lower acuity of illness
• Better Neurologic score
• Cooperative and able to coordinate breathing
  with ventilator
• Less air leaking intact dentition
• Hypercarbia not too severe (PaCO2 gt 45 and
  lt 92 mm Hg)
• Acidemia, but not too severe (pH lt 7.35, gt 7.10)
• Improvements in gas exchange, HR and RR within
  first 2 h

Mehta, Hill. AJRCCM, 2001, 163, 540.
38
Non Invasive VentilationDelivery Issues

• Post Extubation Resp Failure
• Likely Improves Reintubation rate in COPD
  patients
• No change in other etiologies
• May increase mortality (?)
• Staff Requirements
• No increase in nursing time
• Significant increase in RT time in first 8 48
  hours
• Requires MD re-evaluation after first 2 hours
• Results not as favorable when performed outside
  of ICU

Mehta, Hill. AJRCCM, 2001, 163, 540.
39
(No Transcript)