Mechanical Ventilation

the ability to move air in an out of the lungs

• gas exchange at the cellular level
• O2 in and CO2 out

• Acute ventilator failure
• Acute respiratory failure (hypoxemia)
• Pulmonary mechanics - obstruction, low compliance

• most common need for ventilation
• lungs inability to maintain adequate alveolar ventilation
• causes acute respiratory acidosis
• high CO2 (>50mmHg)
• low pH (<7.3)

• pO2<60mmHg
• O2 sat <88%
• shunting occurs - pulmonary capillary perfusion is normal but alveolar ventilation is lacking

• call anesthesia and respiratory
• make sure patient is a full code
• set up suction

• 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

• 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

• iron lungs
• we naturally breath based on negative pressure - lungs expand causing negative pressure causing air to be pulled into the lungs

• pushes air into lungs
• volume cycled
• pressure cycled
• time cycled
• flow cycled

• delivers a preset volume of air to lungs
• most common mode
• pressure in the lungs vary
• increased risk of barotrauma

• delivers a preset gas pressure to lungs
• vent pushes air until there is a certain pressure in the lungs
• amount of air varies

• preset inspiration time
• volume and pressure may vary

• pressure augmentation during inspiration
• decreases work of breathing

• 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 in...so avoid high volumes in these cases

• 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

• # 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

• 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

• 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

• 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)

• 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

• 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)

• 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

• 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

• indicates a disconnection or leak in the system
• air is being pushed in but it isn't meeting any resistance
• check tubing and connections

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)

• >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

• 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

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

• suction only when needed
• hyperoxygenate and hyperventilate
• suction for 5-10 sec maximum
• reassess
• return pt to vent
• document secretion amount and characteristics

• alveolar hyperventilation - can be caused by anxiety and pain
• alveolar hypoventilation - can be caused by decreased level of consciousness

• 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

• common in high PEEP patients
• increased intrathoracic pressure over distends the lungs and prevents cardiac filling
• CO is usually decreased and hypotension may occur

• assess readiness to wean (RTW)
• FiO2<50%
• PEEP<5cmH2O
• nutrition optimized
• afebrile
• no GI bleed; stable Hgb
• stable hemodynamics
• mental status

manual weaning - remove pt from vent and place on t piece. serially increase time of the vent

ventilator weaning - more common

• pt remains attached to ventilator
• vent provides O2 air
• pt does all the work of breathing
• may have PSV added

• 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

• 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

• stridor/laryngospasm is #1 immediate complication
• humidified air with face mask
• chest PT
• cough and deep breathing
• swallowing evaluation

• 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