ARDS Flashcards
Define ARDS & explain the epidemiology
ARDS: acute respiratory distress syndrome
- a condition of hypoxia caused by…
- 1. acute
- 2. diffuse
- 3. inflammatory
lung injury
epidemiology
- 25% of those in the ICU on a vent classify as having ARDS
what is the pathophysiology behind ARDS
(compare and contrast to a normal healthy lung)
normal alvoli & capillary relationship
- the alveoli are “dry” with no excessive fluid or mucus buildup
- the interstium and membrane of the cells allow for selective permiability of gases to cross from high to low pressure
- the capillaries are adequately perfused in that blood is flowing their and being properly oxygenated
in ARDS…
- there is an injury to the alveoli (a precipatating event)
- the injury results in an increase in inflammatory markers to flood to the alveoli
- increase in inflammatory response creats a vicious cycle of neutrophil recrtuiment –> cytokine release –> inflammation build-up
- this results in alveolar injury and capillary injury (theyre so close to each other)
all the inflammatory innjury and buildup leads to a decrease in the ability to properly ventilate the blood and a decrease in o2 flow to the body
explain the stages of ARDS
think about the graph & time in days
Exudative Stage followed by Proliferative (fibroproliferative) Stage
first (1-3 days)
- influx of edema and swelling
second (1-end)
- inflammation of the membranes
end exudative stage & begin Proliferative at 1 week mark (7-10 days)
- decrease in edema
- at this point, recovery can be seen
- or at this point fiberosis can occur within the interstitum
what are some signs and symptoms of ARDS?
- the signs and symptoms are very nonspecific
symptoms
- dyspnea
- cough
- chest pain
- wheezing
- delirum
- respiratory stress
signs
- tachypnea
- tachycardia
- rales & crackles diffuse
- cyanosis
- poor VS and O2 sat.
these signs can be indicative and a result of their underlying condition which precipiated the ARDS
what are some lab studies needed for ARDS?
- what MUST be done in order to make a dx.
- what are some labs that can be done to point towards an ARDS dx.?
MUST GET AN ARTERIAL BLOOD GAS – necessary for dx.
- the ABG will determine the state of hypoxia and allow for the calculation of P/F ratio (the arterial pO2 / FIO2)
other labs to help
- CBC (infection)
- BMP (kideny injury)
- LFT (liver injury)
- coags (INR/PTT/PT for bleeding)
- BNP (will show if there is VOLUME OVERLOAD)
- TTE ( heart failure)
BNP and TTE good to help r/o other causes (HF or volume overload) and to make the dx. based on berlin criteria
what imaging can be done for ARDS dx?
what are the results?
Chest X-Ray
- showing bilateral multifocal infiltrates this indicates diffuse respiratory injury throughout BOTH lungs
Chest CT withOUT contrast
- widespread airspace opacities
- groundglass opacities –> milder
- consolidation –> severe
what is the offical diagnositic criteria for ARDS?
Berlin Criteria
- respiratory symptoms started less than 1 week since onset of insult (the precipitating event)
- evidence of bilateral widespread radiographic opacities
- cannot be explained by a volume overload or heart failure (thus the TTE and the BNP help)
- evidence of moderate to severe oxygen impairment levels of PaO2/FIO2 ratio < 300
oxygen impairment
ratio < 300 = mild ARDS
ratio < 200 = moderate ARDS
ratio < 100 = severe ARDS
a note about the P/F ratio and how it is calculated and used in ARDS
P = PaO2 –> pressure of O2 in the artery obtained via a ABG
F = FIO2 –> percent of O2 delivered to the pt.
- normal atm. = 21%
- but with ventiliation help (nonrebreather, NC, etc. this can changed depending on %O2)
in a healthy person = (100)/(.21) = 476
in ARDS person = (75)/(.70) = 107 – severe
what are some causes of ARDS?
** the precipitating factors**
- there are SO MANY
- commonly –> a primary lung injury (pneumonia) but not always
- need to think of extra-pulmonary injuires
examples (majority)
- pneumonia
- sepsis
- aspiration
what are the principles of managing ARDS?
- not specific treatments but the goals of thearpy
- treat the underlying cause (the precipitating factor)
- treat the hypoxia
- mechanical ventilation management
- supplemental ARDS therapy use
** goasl of treatment outline by ARDS Net**
how is goal #1 of ARDS treatment done?
treating the underlying cause
- this will vary depending on what the preciptating factor is
- if its infection –> abx. (like sepsis or bacteremia)
- if tis pancreatitis –> ressect and abx.
- if its drug related –> stop using the drug
etc.
how is goal #2 of ARDS treatment conducted?
- treatment of the hypoxia
the goal is to increase the pts. PaO2 levels via using high levels of FIO2
- ideally –> want a pulse ox. (measuring hgb sat.) @ 90%
- this would put the PaO2 level at 60mmHg (want between 55-80)
mechanisms of how this can be achieved
- high-flow NC
- CPAP or BiPAP
- invasive mechanical ventilation (often this is what pts. with ARDS need)
How is goal #3 of ARDS treatment achieved?
- proper mechainal ventilation
- want low tidal volume ventilation
- low tv are “lung protective” and help to avoid damage via overinflation
- ideally want 6 cc/kg of ideal body weight - want low airway pressure ventilation
- want a low plateau pressure –> the pressure of air the alveoli are getting with each breathe
- ideally want a plateau pressure < 30 cm/H20
what is the trade off with low airway pressure and low tidal volume in vent. managment of ARDS?
what is one thing that can be done to assist in ensuring this trade off is okay? ( high Co2 combated by…)
there is an increase in CO2 levels within the pts. with these lower RR and pressures
- ability to maintain these slightly higher PCO2 levels results in a lower pH than normal within the body
but this level is still acceptable
- goal is to keep pH >7.15
adjust the PEEP to combat the higher CO2 and lower pH level
- keeping the PEEP level higher than normal breath can help to improve oxygenation
- goal is to titrate PEEP to get pplat < 30
- **drive pressure = pplat - PEEP & want drive pressure < 12-15 **
in sum … what are the patterns of mechanical ventilation a pt. needs for ARDS
- lung protective ventilation – small and quick breaths
- want a low tidal volume (low pressure in the airway)
- want a low plateau pressure (to keep the pressure into the alveoli from being too much)
- okay to have higher CO2 levels - oxygenation goals maintained
- adequate level of O2
- adequate PEEP level (to increase oyxgenation and comabt CO2)
