Mechanical Ventilation

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?? ??Mechanical Ventilation

• ???? ??

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????? ???

• ? ?? ??? Respiratory failure
• hypoxemic respiratory failure
• SaO2 lt90 despite FiO2 gt0.6
• hypercarbic respiratory failure
• acute hypercarbic respiratory failure
• PaCO2 gt50mmHg pH lt7.30
• acute and chronic hypercarbic respiratory
  failure
• (blood gas? ????? ??)
• ? ??
• controlled hyperventilation (ICPpt, postop pul
  HT pt)
• work of breathing (CHF pt)
• prevent aspiration (gastric lavage for drug
  overdose pt)
• ??/?? ?? ? respiratory failure ??? ???? ??
  (open lung biopsy in critically ill pt)

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Ventilator setting

• Major
• mode, FiO2, tidal volume, frequency, PEEP
• Minor
• inspiratory flow rate wave shape
• IE ratio
• pause time
• ?? setting??? setting? ?? ??
• V/S, P/E, subjective response, pulse oxymeter ??
  ??
• ABG major setting? ?? ?? 20-30? ? ??? ??

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Mode (??)

• CMV (controlled mandatory ventilation)
• ACMV (assisted/controlled mandatory ventilation)
• SIMV (synchronized intermittent mandatory
  ventilation)
• PSV (pressure support ventilation)
• CPAP (continuous positive airway pressure)

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????(Mode) ??

• Control variables
• Phase variables
• Conditional varibales

?? ??
Tobin. Principles and practice of mechanical
ventilation p49
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Control variable

• ??? ?? ?? (target)
• mode? ??
• VCV (volume control ventilation) ??? tidal
  volume
• PCV (pressure control ventilation) ??? airway
  pressure

Tobin. Principles and practice of mechanical
ventilation p49 ?6? ?????? ????? ??? p31-34
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VCV ??? ???? ??
PCV ??? ???? ??? ????
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Phase variable

• phase(??/??)? ??, ??, ??? ??
• phase variables
• triggering ?? ??
• ventilator triggering
• patient triggering pressure triggering, flow
  triggering
• limit variable ?? ?? ??
• pressure limit ? PVC
• flow limit ? VCV
• cycle variable ?? ?, ?? ??
• time cycle (PCV), volume cycle, flow cycle (PSV)

Tobin. Principles and practice of mechanical
ventilation p49 ?6? ?????? ????? ??? p31-34
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Mode? ?? - Phase variable

• CMV
• ?? ??? ventilator? ?? triggering, cycling ?.
• ACMV
• ??? frequency??? ventilator? triggering?? ??? ??
  ??? ?? ??? triggering?. ???? cycling? ??
  ventilator? ?.
• SIMV
• ventilator? ???? controlled mandatory
  ventilation? ???? ???? ??? ?? ??? ???. ?? time
  window ?? ??? triggering?? assist mandatory
  ventilation, triggering?? ??? controlled
  mandatory ventilation? ???.

?6? ?????? ????? ??? p31-34
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VCV vs. PCV

• ??
• VCV tidal volume ??, pressure ??
• PCV pressure ??, tidal volume ??
• ??? ??? ??? ? ? ??.
• ??, VCV? inspiratory flow waveform? decelerating
  pattern?? ? ??
• ??. Bronchoscopy? ??? VCV
• ACMV, SIMV VCV? PCV ?? ??

Marini JJ editor. Critical care medicine, the
essentials p121 ?6? ?????? ????? ??? p31-34
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Pressure? ??? ????
VCV
Pressure? ?? ??
Volume? ???? ??
PCV
Volume? ?? ??
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PRESS. SUPPORT

• Pressure support ventilation
• ??? INSP. PRESS. LEVEL ? ??? ???? ???
• ?? ?, ?? ?? flow? peak inspiratory flow? 25?
  ??? ?
• ??
• ?? ??/?, ??, ??? ??(synchrony) ??? cycle ??? ??
  COPD, anxiety ? ??.
• Pressure? ????? ?? ? weaning? ??.

Siemens. Servo Ventilator 900C Operating manual
p2.13
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SIMV

• ?. BREATHS/min 15, SIMV BREATHS/min 6
• ?. SIMV period 60/15 4s, SIMV cycle 60/6
  10s
• spontaneous period 10-4 6s

Siemens. Servo Ventilator 900C Operating manual
p2.14
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PEEP
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Positive End-Expiratory Pressure

• Definitoin
• Pressure in the airway is elevated above that of
  the atmosphere at the completion of expiration
• CPAP Airway pressure remains positive during
  insp and expiration.
• Effects of PEEP
• favorable experience with PEEP in ARDS
• Beneficial Effect
• improvement in arterial oxygenation
• improvement of lung compliance
• alleviation of excessive WOB in airway limitaions
• decrease in lung injury from repeated alveolar
  collapse reopening

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Effects of PEEP- Improvement of oxygenation -

• Increase in end-expiratory lung volume
• Distension of patent lung units
• Recruitment of collapsed lung units
• Redistribution of fluid within the lung
• Decrease in shunt
• Increase in end-expiratory lung volume
• Decrease in cardiac output
• ? permitting a decrease in FIO2 and reduction in
  risk of O2 toxicity

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Side effects of mechanical ventilation

• barotrauma
• ventilator-associated lung injury
• permissive hypercapnia
• oxygen toxicity
• ??

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Barotrauma

• ??
• pneumomediastinum, subcutaneous emphysema
• ?? ??? ??? ? ?? ??.
• 20-30?? pneumothorax ??
• pneumothorax
• tension?? ??? ?? 60-90 ? tube? ??
• Barotrauma ? ??? ??? pressure??
• ??. ??? ????? ?? ???? ???
• ???? ??
• End-inspiratory plateau pressure gt 35cmH2O
• Peak inspiratory pressure gt 40cmH2O
• stiff chest wall ??? ? ??? ??.

Marini JJ editor. Critical care medicine, the
essentials p138-9
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Barotauma ?? ??

• End-inspiratory plateau pressure
• peak static airway pressure
• Peak inspiratory pressure
• peak dynamic airway pressure
• duration of ventilation
• necrotizing lung pathology
• nonhomogeneous lung pathology
• excessive airway secretions
• nonhomogeneous, ball-valve
• young age

Marini JJ editor. Critical care medicine, the
essentials p138-9
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Ventilator-induced lung injury

• ?? ??
• ARDS like injury
• ??
• overdistension of alveoli
• collapse and reinflation of alveoli
• ?? diseased alveoli (ARDS?)?? ? ??
• ??
• low tidal, PEEP ? CO2 retention
• ? permissive hypercapnia

Marini JJ editor. Critical care medicine, the
essentials p146-9
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Permissive hypercapnia

• PaCO2 upto 100mmHg
• contraindication
• ICP ??
• ???? ??? ???? ???
• severe pulmonary hypertension
• metabolic acidosis ?? ?
• sedation ??
• ??? muscle relaxant ??? ?

Hess DR. Essentials of Mechanical Ventilation
p63 Marini JJ editor. Critical care medicine, the
essentials p149
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O2 Toxicity - human
Asymptomatic period with no physiologic change

100 O2 ?? 6-12??
Fishmans Pulmonary diseases and disorders 3rd
ed.p2640
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???? ? ?? ??? ???? ?? ??

• 1. ?? Ambu bagging with 100 O2
• 2. ??? ???? ???? ??
• 3. ??? ??? ???? ??, ?? ?? ? ??
• 4. ?? ?? ? ? ??? ??

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Weaning ?? ??

• P/E
• rapid shallow breathing f lt 30/min, VT ?5mL/kg
• irregular breathing
• scalene m. or abdominal m.
• BP gt 80mmHg
• pulse 70120
• ABGs
• FiO2 ?0.4
• pH gt 7.30

Marini. Critical care medicine The essentials
p179-181
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Weaning ?? ??

• Ventilation
• VE ?10-15L/min or VE ?175mL/min
• Strength
• MIP lt -20cmH2O
• VC ? 10mL/kg
• Endurance
• VC gt 2xVT
• f/VT lt100 rapid shallow breath index

Marini. Critical care medicine The essentials
p179-181
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?? weaning ??

• ?? Weaning? ? ? ??? ?? ??? ?? ???? ??? ?? ??.
• ??, ?? ??? ? ?? ????? ??? weaning? ??? ???? ??.

Harrisons principles of internal medicine14th
ed. p1490