ICU - Marino Flashcards
Volume Control, preselect
TV
Volume Control, pressure
peak pressure in proximal airways > peak pressure in alevoli
Volume Control Advantages
- Constant TV which allows for pressure adjustments to offset increased resistance or decreased compliance
Volume Control Disadvantages
- pressure at end of inspiration are higher (?risk of lung injury)
- duration of inspiration is short, inspiratory flow rate can be inadequate which can lead to pt discomfort
Pressure Control, preselect
pressure, do so with decelaerating inspiratory flow that allows high flow at onset of lung inflation
Pressure control, pressures
end inspiratory airway pressure = peak alveolar presure
Pressure Control Advantages
control peak alveolar pressure (30cmH20)
Patient comfort due to high initial flow rates
Pressure Control Disadvantages
decrease in alveolar volume when resistance increases or compliance decreases (concern in ARF)
PRVC
constant tidal volume but limits end inspiratory airway pressure
selecting lowest pressure needed to deliver tidal volume
Assist Control ventilation, mode
can be PC or VC
Assist Control triggers
negative pressure or flow rate
Negative Pressure as Trigger
generate 2-3cmh20 however this is double the pressure during quiet breathing
1/3 of efforts fail to trigger ventilator
Flow Rate as Inspriation Trigger
rates of 1-10L/min required
possible issue is auto-triggers from system leaks
Assist Control Concerns
Respiratory cycle and decreasing exhalation
rapid breathing
Respiratory Cycle, IE ratio should be
1:2
prevent dynamic hyperinflation or intrinsic PEEP
IMV
allow spontaneous breathing between ventilator breathes
can be VC or PC
IMV major indication
rapid breathing with incomplete exhalation
why is spontaneous breathing good?
promotes alveolar emptying and reduces the risk of trapping/intrinsic PEEP
when not to use IMV
respiratory muscle weakness
left heart failure
IMV Disadvantages
increased WOB decrease CO (esp in pts with LVdysfxn)
IMV, increased WOB
due to resistance in ventilator circuit
pressure-support can help overcome
pressure support
allows pt to terminate the lung inflation
PEEP at 5-10
helps prevent collapse of distal airways
PEEP at 20-30
can reopen distal airspaces = alveolar recruitment
what can happen with alveolar recruitment if not significant volume of recruitable lung?
alveolar distention, increases risk of ventilator-induced lung injury
how to measure if there is recruitable lung
lung compliance
pa/fio2 ratio
increased PCO2
resp acidosis
decreased PCO2
resp alkalosis
increased HCO3
metabolic alkalosis
decreased HCO3
metabolic acidosis
Metabolic Acidosis, secondary response
increase minute ventilation (TV x RR) –> decrease in PCO2
how long do secondary respiratory responses take
can being in 30min-2h, can take 12-24 hrs to be complete
Metabolic Acidosis and using PaCO2 to infer secondary disorder
paco2 > 23, resp acidosis
paco2 less than 23, resp alk
Step “1” of Acid/Base: looking at PaCo2 and PH
if both abnormal, comparing directional change
if only one is abnormal, condition is mixed (directional change of paco2 or pH identifies primary disorder)
Primary Resp disorders, how to tell if acute
normal or near-normal HCO3
chronic resp acidosis and HCO3
if lower, incomplete renal response
if higher, secondary metabolic alkalosis
chronic resp alkalosis and HCO3
if higher, incomplete renal response
If lower, secondary metabolic acidosis
AG
NA - Cl + HCO3
AG range
3-11 (7 plus/minus 4)
AG with albumin
AG + 2.5 x (4.5-albumin)
Evevated AG occurs when
accumulation of fixed or nonvolatile acids
Normal AG occurs when
primary loss of bicarb
Delta Ratio
AG-12 / 24 - HCO3
Delta Ratio, how to interpret
1 = HG metabolic acidosis only
less than 1 = second acidosis
more than 1 = metabolic alkalosis
Causes of High Anion Gap Acidosis
Methanol/Metformin, Uremia, DKA/Starvation/Alcohol Ketosis, Paraldehyde, Isonizaid or Iron, Lactic Acidosis, ethylene glycol, rhabdo, salicilaytes
Causes of Normal Gap Acidosis
Hyperalimentation, Acetalozamide, RTA, Diarrhea, Ureterosigmoid fistula, pancreatic fistula
ARDS defintion
acute onset, bilateral infiltrates on xray, pao2/fio2 less than 300mmhg
no evidence of left heart failure
presence of predisposing condition
ARDS: old criteria vs berlin criteria
pao2/fio2 changed
ALI eliminated
no wedge pressure measurement
volutrauma
excess inflation of distal airspaces
ventilator-induced injury
barotrauma
associated with escape of air from lungs
biotrauma
during conventional high volume mechanical ventilation, proinflamm cytokines can appear in lungs and systemic circulation despite no structural differences in lungs
atelectrauma
collapse of small airways at end expiration
