Mechanical Ventilation Day 5

Front 1

Assignment

Back 1

Egan chapter 46 1041 to 1047

Front 2

Effects of PEEP on lung mechanics, overdistention

Back 2

P/V curve and lung recruitment in ARDS

:Set peep 2 cm h20 above lover Pflex

:Avoid hitting upper Pflex as indicates overdistention

:20 ml change with a high cost of pressure then lower pressure, to keep beaking down

:note that the Pflex points are often difficult to identify

Deadspace increases PaCO2

Shunt decreases PaO2

Front 3

Effects of PEEP on lung mechanics

Back 3

P/V curve and lung recruitment in ARDS

:Lung recruitment (RM) has proved very useful

::Commonly 40 to 50 cm H2O applied over less than 3 minutes

:Recent approach to setting PEEP

::decremental PEEP trial following recruitment maneuver. (RM)

::Best PEEP where highest compliance is noted

::Recruit lung again, then set PEEP at best level

Front 4

non cardiogenic pulmonary edema also called ARDS

Back 4

Cardiogenic pulmonary edema is left heart failure

increasing peep also increases FRC or surface area.

Front 5

Effects of positive pressure ventilation on WOB

Back 5

Decreased work of breathing (WOB)

:1st goal of all mechanical ventilation modes is to reduce WOB

:Continuum from full support (A/C) to little (CPAP)

WHere to do set the peep to give us the greatest change in volume over change in pressure

We can do that by tidal volume / (static pressure - PEEP) = static compliance

Front 6

Effects of PPV

Back 6

increase PTP

Increase intrathoracic pressure

Decrease venous return: preload

Decrease cardiac output: starlings law

Decrease renal perfusion

Increase ADH

:Decrease urine output

Increase ICP

Front 7

Frank starlings law states

Back 7

stroke volume is a function of ventricular end diastolic stretch. and increase in the stretch of the ventricles immediately before contraction (end diastole) results in an increase in stroke volume. Ventricular end diastolic stretch is synonmyous with the concept of preload

Front 8

Harmful effects of PPV on lung tissue

Back 8

Mechanical ventilation leads to biochemical injury and biophysical injury

Bio physical injury is

:Shearing,

over distention,

cyclic stretch, and

increased intra thoracic pressure

:Increase alveolar capillary permeability

:decrease cardiac output

:Decrease organ perfusion

Type 1 cells are the wall of the alveoli(they get damaged and pull apart, increases permeability)

Type 2 cells make surfactant

Type 3 cell are the macrophages that eat things

MSOF multisystem organ failure

Front 9

Clinical goals for mechanical ventilation

Back 9

Support or manipulate gas exchange

:V(A)

:O2 delivery (DO2) = CaO2 X CO X 10

Increase lung volume (increase FRC, or surface area)

:Reverse/prevent atelectasis w/ PEEP

:Increase FRC

:Increase compliance

Decrease WOB

Front 10

Complications of mechanical ventilation

Back 10

Negative pressure ventilation

:Pulmonary complications

::Hypoventilation due to inadequate negative pressure or leaks, or hyperventilation, too negative pressure

:Cardiovascular complications

::Abdominal blood pooling, reducing venous return CO and blood pressure, leading to shock

::With iron lung, patient isolation occurs, as all but head is inside the tank

:Difficult to access lines, do patient care, etc.

Front 11

Complications of mechanical ventilation: PPV

Back 11

Positive pressure ventiliation

:Artificial airway complications

::Intubation trauma to eyes, teeth, soft tissues, tube migrating

::Nasal ETT: epistaxis(nose bleed), sinusitis, necrosis of nares

::Oral ETT: necrosis of lips, patient may bite the tube

::Placement of ETT in esophagus or bronchus

Front 12

Complications of mechanical ventilation: PPV

Back 12

Positive pressure ventilation

:Ajrtificial airway complications

::Cuff leak; hypoventilation, aspiration, pneumonia

::Excessive cuff pressure: tracheal necrosis, cuff rupture (requires reintubation)

::Tracheostomy tube, innominate artery erosion, hemorrhage, tracheal stenosis, and cuff issues

:Immobility

::wounds

::fluid retentions (increases PIP, decreases SPO2, affects blood gases)

::Physiological issues

Front 13

Complications of mechanical ventilation: barotrauma

Back 13

Complications related to pressure

Ventilator associated lung injury (VALI)

:High pressures are associated with barotrauma

::Pneumothorax, pneumomediastinum, pneumopericardium, subcutaneous emphysema

:Pneumothorax has decreased chest movement, hypperesonnant to percussion on affect side

Front 14

Complications of mechanical ventilation: barotrauma

Back 14

Volume related as a result of alveolar overdistention

Ventilator induced lung injury (VILI)

:Increased A/C permeability, pulmonary edema, cell damage (type 1 cells)and necrosis, diffuse alveolar damage

:Interstitial pulmonary edema is always a prescursur to pulmonary edema or ARDS.

A fluid filled alveoli leads to decreased compliance

The alveolus gets additional routes for the interstitial pulmonary edema to flood the alveous due to the cell damage from overdistention, leading to more alveolar capillary membrane diffusion allowing the alveolus to fill with fluid. THis leads to increase fluid or pullmonary edema. PEEP pushes the fluid back and distends the alveoli allowing better gas exchange. But if the fluid stays too long, the tissue becomes fibrotic, decreasing compliance, this can be reversed:Overdistention causes volutrauma and biotrauma

. THis leads to increase fluid or pullmonary edema. PEEP pushes the fluid back and distends the alveoli allowing better gas exchange. But if the fluid stays too long, the tissue becomes fibrotic, decreasing compliance, this can be reversed

:Overdistention causes volutrauma and biotrauma

Front 15

Complications of mechanical ventilation: barotrauma

Back 15

Ventilator induced lung injury (VILI)

:Recruitment, derecruitment of alveoli (atelectrauma)

::led to lung protective (P(plat) less than 30 cm h20) and open lung (recruit then set adequate PEEP) strategies

:Biotrauma releases inflammatory mediators, results in inflammation, imparied DO2 and bacteremia

::Contribute to MSOF multisystem organ failure

Front 16

Complications of mecchanical ventilation: auto PEEP

Back 16

AutoPEEP (occult or intrinsic PEEP)

:Air trapping occurs if E(T) expiratory time is too short for patients condition

expiratory time is the ventilator rate. shorter e time, higher rate, longer e time, lower rate

::Expiratory flow is interrupted by next breath

::greatest risk with increase RAW(like asthma) (obstructive disorder), increased compliance (like emphysema)

:not included in measured and displayed PEEP value so easy to overlook

:Occurs most often when the patient does not have ventilatory needs met

::Increase patient rate because of air hunger, or decrease compliance, they are stiff

Front 17

Causes of auto peep

Back 17

when airway resistance is normal and expiratory time is long enough, Resistance prolongs exhalation to the point at which air trapping beings so auto PEEP. or decrease expiratory time aggravates the problem and worsens the auto peep

Front 18

Complications of mechanical ventilation: auto peep

Back 18

Autopeep (occult or intrinsic PEEP)

:Increases air trapping by not allowing hte lung to completely empty its tidal volume

::Making it difficult for patient to trigger

::Asynchrony

:Increases WOB by decreasing diaphragms effectiveness

:Treatment: decrease autopeep by increasing E(T), decrease V(T) and increase PEEP set until patient can empty lung and trigger effectively

Front 19

Complications of mechanical ventilation: O2 toxicity

Back 19

Oxygen toxicity

:Mimics ARDS: tissue damage with increase A/C permeability

:Risk factors: length of exposure, FiO2 susceptibility

::Associated with FiO2 greater than 50% for 24 to 48 hours

::Risk increases the higher the FiO2

Oxygen toxicity

:oxygen free radicals increase with FiO2

::Impair type 2 cell production of enzyme superoxide dismutase, which detoxifies free radicals, so unequal surface tension.

::Increase A/C permeability: type 1 celll damage

::Decrease surfactant production