Mechanical Ventilation

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  1. Ventilation
    the ability to move air in an out of the lungs
  2. Respiration
    • gas exchange at the cellular level
    • O2 in and CO2 out
  3. Reasons for Ventilatory Support
    • Acute ventilator failure
    • Acute respiratory failure (hypoxemia)
    • Pulmonary mechanics - obstruction, low compliance
  4. Acute Ventilatory Failure
    • most common need for ventilation
    • lungs inability to maintain adequate alveolar ventilation
    • causes acute respiratory acidosis
    • high CO2 (>50mmHg)
    • low pH (<7.3)
  5. acute respiratory failure (hypoxemia)
    • pO2<60mmHg
    • O2 sat <88%
    • shunting occurs - pulmonary capillary perfusion is normal but alveolar ventilation is lacking
  6. pre-intubation
    • call anesthesia and respiratory
    • make sure patient is a full code
    • set up suction
  7. Post-intubation
    • secure ET tube
    • document placement (at lip)
    • auscultate bilaterally
    • end tidal CO2 - measures CO2 in the exhaled breath to ensure that tube is in trachea and not esophagus
    • CXR to confirm placement
  8. tracheostomy
    • surgically created
    • used for a prolonged need of an artificial airway
    • can improve weaning
    • improves patient discomfort and prevents skin breakdown that can occur from ET tube in mouth
  9. Negative pressure ventilator
    • iron lungs
    • we naturally breath based on negative pressure - lungs expand causing negative pressure causing air to be pulled into the lungs
  10. Positive pressure ventilation
    • pushes air into lungs
    • volume cycled
    • pressure cycled
    • time cycled
    • flow cycled
  11. volume cycled positive pressure ventilator
    • delivers a preset volume of air to lungs
    • most common mode
    • pressure in the lungs vary
    • increased risk of barotrauma
  12. pressure cycled positive pressure ventilation
    • delivers a preset gas pressure to lungs
    • vent pushes air until there is a certain pressure in the lungs
    • amount of air varies
  13. time cycled positive pressure ventilation
    • preset inspiration time
    • volume and pressure may vary
  14. flow cycled positive pressure ventilation
    • pressure augmentation during inspiration
    • decreases work of breathing
  15. Tidal Volume
    • amount of air delivered to the lungs in one breath
    • normal TV =5-12mL/kg (500-800mL)
    • complications of high TV - barotrauma (creates high pressure and can rupture alveoli)
    • complications of low TV - hypoventilation (lead to hypercapnia)
    • consider lung compliance - lungs may be too stiff and O2 can't be pushed avoid high volumes in these cases
  16. Fraction of inspired oxygen (FiO2)
    • percentage of oxygen of inspired gas
    • ranges from 0.21-1.0 (21%-100%)
    • usually start with the lowest amount as possible
    • complication: oxygen toxicity - damages endothelia lining and decreases mucous and surfactant protection - common with COPD patients
  17. Rate
    • # of breaths per minute delivered to patient
    • normal: 6-20
    • in some ventilator modes the rate can be controlled by the patient or the vent
  18. positive end expiratory pressure (PEEP)
    • extra pressure at expiration that maintains pressure in the alveoli to keep them open a little
    • it increases the amount of O2 that the capillaries are able to extract from the alveoli - leads to increased O2 in the blood
    • primarily used for refractory hypoxemia to prevent atelectasis
    • up to 30cmH2O
    • complications - barotrauma and decreased CO
    • Auto PEEP - build up of pressure leading to air trapping
  19. peak airway pressure (peak inspiratory pressure)
    • pressure required to deliver volume of air
    • healthy lungs need 20cmH2O
    • goal: <40cmH2O
    • value will be increased with decreased lung compliance, worsening pulmonary status, coughing, need for suctioning
    • value will be decreased with improving status
  20. Assist Control ventilator (continuous mandatory ventilation)
    • pt. gets set # of breaths per minute at a set TV
    • additional inspiratory breaths are assisted at set TV
    • advantage: allows resp muscles to rest
    • disadvantages: high resp rate will cause hyperventilation (resp alkalosis)
  21. Synchronous intermittent mandatory ventilation (SIMV)
    • pt. gets set # of breaths per minute at set TV
    • pt. has to bring in their own TV for any additional breaths that are attempted
    • advantages: decreased risk of hyperventilation, forces exercise of resp muscles, used for weaning
    • disadvantages: potential for fatigue d/t inadequate rest periods
  22. Continuous positive airway pressure (CPAP)
    • no preset resp rate or TV
    • pt. generates their own resp rate and TV
    • used for weaning
    • only provides a source of positive pressure O2
    • often used with pressure support ventilation (PSV)
  23. pressure support ventilation (PSV)
    • adjunct to weaning mode
    • helps to overcome increased airway resistance by applying positive pressure
    • decreases work of breathing
    • triggered by spontaneous breath (pt. own attempt at breathing)
    • 5-15cmH2O
  24. high pressure alarm for vents
    • indicates resistance in the circuit (vent has trouble pushing TV into the lungs)
    • secretions
    • coughing
    • tube kinked or pt biting tube
    • high lung compliance
    • poor synchronization
  25. low pressure alarm on vents
    • indicates a disconnection or leak in the system
    • air is being pushed in but it isn't meeting any resistance
    • check tubing and connections
  26. complications of mechanical vents
    CV - decreased CO (esp if TV is too high b/c too much air in chest cavity leaves little room for the heart to expand), preload and SV

    pulmonary - changes flow of gas, O2 toxicity, risk of VAP, barotrauma

    renal - decreased perfusion

    GI - stress ulcer (very common)

    neurovascular - decreased flow to head, decreased venous return from head (increased ICP)
  27. O2 toxicity
    • >80% FiO2 for >48 hours
    • damages endothelium lining of alveoli, decreases mucous and surfactant production
    • symptoms (nonspecific)- malaise, fatigue, substernal discomfort
    • add PEEP and reduce the FiO2 to decrease risk of O2 toxicity
  28. Ventilator Bundle
    • HOB>30 degrees
    • prevent stress ulcers (H2 blockers/ PPI)
    • DVT prophylaxis
    • sedation vacation - wake up Q24H to assess neuro status
    • oral care Q4H
    • consider weaning trial - assess daily
  29. Artificial airway complications
    insertion trauma - bleeding; damage to mucous membranes

    cuff trauma - compromise arterial capillary blood flow; monitor cuff pressure Qshift (20-25mmHg)

    vocal cord paralysis or damage - hoarseness may be temporary or permanent

    swallowing dysfunction- can cause chronic aspiration

    tracheoesophageal fistula (rare) - can cause gastric secretions to be aspirated into the lungs
  30. ineffective airway clearance
    • suction only when needed
    • hyperoxygenate and hyperventilate
    • suction for 5-10 sec maximum
    • reassess
    • return pt to vent
    • document secretion amount and characteristics
  31. impaired gas exchange
    • alveolar hyperventilation - can be caused by anxiety and pain
    • alveolar hypoventilation - can be caused by decreased level of consciousness
  32. ineffective breathing patterns
    • tachypnea - alteration in acid/base balance
    • bradypnea- hypooxygenation
    • patient ventilator dysynchrony - pt expiration while vent is on inspire

    resp distress - manually bag pt at 100% FiO2 first and then call for help
  33. alteration in cardiac output
    • common in high PEEP patients
    • increased intrathoracic pressure over distends the lungs and prevents cardiac filling
    • CO is usually decreased and hypotension may occur
  34. Weaning
    • assess readiness to wean (RTW)
    • FiO2<50%
    • PEEP<5cmH2O
    • nutrition optimized
    • afebrile
    • no GI bleed; stable Hgb
    • stable hemodynamics
    • mental status
  35. weaning modes
    manual weaning - remove pt from vent and place on t piece. serially increase time of the vent

    ventilator weaning - more common
  36. CPAP weaning
    • pt remains attached to ventilator
    • vent provides O2 air
    • pt does all the work of breathing
    • may have PSV added
  37. Intermittent mechanical vent weaning
    • pt starts off with high # of preset breaths
    • overtime the preset breaths are reduced which forces pt to do more work of breathing
    • builds endurance of resp muscles
    • often used with difficult wean patients
  38. assessing a weaning trial
    • tidal volume - increased
    • resp rate - decreased
    • vital signs w/in normal ranges
    • cardiac rhythm
    • ABGs
    • general appearance
    • rapid shallow breathing index (RSBI) - RR/TV - target score is <100
  39. postextubation care
    • stridor/laryngospasm is #1 immediate complication
    • humidified air with face mask
    • chest PT
    • cough and deep breathing
    • swallowing evaluation
  40. Noninvasive intermittent positive pressure vent (NIPPV)
    • mask covers nose or mouth and nose
    • less risk of infection

    • complications
    • gastric distention - air goes into abd
    • aspiration - keep NPO
    • hypoventilation
    • skin irritation
    • nasal problems
    • conjunctivitis
    • removal/noncompliance
Card Set
Mechanical Ventilation
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