Resp Flashcards
Minimum staffing needs to do a perc Trachy
3
Two medics
One assistant
Cuff pressure in a perc trachy
20-30
Berlin criteria for ARDS
Timing - within one week of clinical insult
Chest imaging - bilateral opacities, NOT explained by effusions or collapse, and in keeping with pulmonary oedema
Origins of oedema - respiratory failure not explained by cardiac failure or fluid overload. Consider an echo
Hypoxia - PF ratio
26.6 to 39.9 mild
13.3 to 26.6 moderate
Less than 13.3 severe
Berlin criteria timing
Within one week of the clinical insult
Berlin criteria chest imaging
Bilateral opacities, not explained by effusions or collapse, and in keeping with pulmonary oedema
Berlin criteria hypoxia
PF ratio
Mild 26.6 to 39.9
Moderate 13.3 to 26.6
Severe less than 13.3
Moderate asthma
PEFR 50-75% predicted
Severe asthma
PEFR 33-50 Resp rate more than 25 Heart rate more than 110 Low or normal pCO2 Cannot complete a sentence
Life threatening asthma
PEFR less than 33% Silent chest Feeble effort Hypotension Arrhythmia Bradycardia Hypoxia less than 92% or pao2 less than 8 Hypercapnia Altered neurological state
Risk factors for fatal asthma
Previous life threatening with acidosis or need for ventilation
Hospital admission in last year
Three or more asthma meds for chronic control
Heavy beta agonist use
Brittle asthma :
Type 1 wide PEFR variability
Type 2 sudden severe attacks despite being well controlled
Adverse psycho social circumstances - non compliance, alcohol abuse, social isolation
CURB 65 score
Confusion Urea more than 7 Resp rate > 30 Systolic < 90 Age> 65
Effusions based on protein
Transudate < 30g/L
Exudate > 30g/L
Lights criteria
An exudate is suggested by
Pleural to serum protein level > 0.5
Pleural to serum LDH level > 0.6
Pleural LDH level that is more than 2/3 upper limit of normal serum LDH level
Pleural fluid features of an empyema
PH less than 7.2
Glucose < 3.3
Bacteria on microscopy
Fluid LDH > 1000
What is compliance
Change in lung volume per unit change in pressure
What is the compliance of the lung and the chest wall
They are the same
200ml/cmH2O
What is the total compliance and how is it calculated
100ml/cmH2O
Calculated at the sum of reciprocals
1/total = 1/chest wall + 1/lung
= 1/200 + 1/200
= 2/200
= 1/ 100
Therefore 100
What is static compliance and how is it measured
Compliance in the absence of gas flow
Do an end inspiratory hold manoeuvre or add insp pause to estimate PLATAEU
Pressure
Eqn:
C= Vt/(Pplat - PEEP)
What decreases static compliance
Lung parenchyma disease ARDS, pneumonia, fibrosis
Chest wall disease: kyphoscoliosis, obesity, burns
Raised IAP
What is dynamic compliance
What is the eqn
Measured during rhythmic breathing
Determined by the PEAK pressure, not the plateau
Cdyn= Vt/Ppeak - PEEP
Which compliance is smaller and why
Dynamic compliance is smaller
Peak (the measurement of dynamic) is higher than plateau (the static measurement)
Peak pressure represents compliance of lung, chest wall and pressure needed to overcome airway resistance
Usually dynamic is 2-3 ml/cmH2O less than static
The difference between dynamic and static is quite small, what would make it increase
Obstructive airway disease, where higher pressures are needed to overcome the overcome the increased resistance
What is the relationship between alveolar minute ventilation a PaCO2
Doubling the MV halves the paCO2
What is the relationship between minute volume and pao2
Increasing the minute volume does little to o2, incredibly small rises, but parallel lines occur on increasing the Fio2. The o2 starts to fall when the MV drops below 5
Relationship between PaCO2 and minute ventilation
Rising CO2 causes the minute volume to increase, linearly, up to a point where the resp drive is blunted.
The curve shifts right, by chronic hypercapnia, and opiate
Relationship between PaO2 and MV
PaO2 has little effect on MV, EXCEPT when it falls below 8, when MV starts to increase. Curve shifts up and right in raised CO2 as it initiate the respiratory drive
What is the oxygenation index
OI = FiO2 x mean airway pressure/PaO2. X 100
It is the pressure needed to maintain a given PF ratio, so that comparison between patients with same PF but different vent requirements are made
High OI is worse
What is the Murray score and it’s components
Determines lung injury in ARDS
LUNG INJURY SCORE
number of involved quadrants on CXR
PF ratio
Level of PEEP
Static compliance (Vt/plat-PEEP)
What is peak pressure
Maximum airway pressure measured in a resp cycle
What is the plateau pressure
Airway pressure measured during inspiratory pause
What is the significant of peak pressure
Pressure applied to large airways, and therefore influenced by airway resistance
Significance of plateau pressure
Pressure applied to alveoli
Criteria for readiness to wean
Improving clinically
Adequate oxygenation > 8kPa (Fio2<0.4, PEEP<10)
Cardiovasular stability (HR<120, minimal to no vasopressors)
Afebrile
No resp acidosis
Hb>70
GCS>12
Cough function to clear secretion
Conditions of a RSBI
Spontaneously breathing
Awake
Minimal Resp Support
2 minutes on a T-piece
Second minute determines the result - RR/Tv
Results as breaths/min/L
Greater than 105 - high risk of extubation failure (95%)
Less than 100 - 80% chance of success
Does RSBI improve outcomes
No
Definition of prolonged MV
Ventilator support for greater than 21 days
UK definition based on invasive vent
International concensus catergories of weaning
Simple, Difficult, Prolonged
Simple: Progress from wean to successful extubation at first go
Difficult: up to 3 SBTs or 7 days from first SBT prior to extubation
Prolonged: failure to extubate after at least 3 SBTs or more than 7 days following first SBT
Maximum MRC score
60
