Respiratory Flashcards
On traditional lung ultrasound, “lung sliding” is more commonly known as what sign?
Glide sign
When it comes to lung ultrasound and a glide sign, the principle of lung sliding is based on 2 key concepts. What are they?
1 the parietal and visceral pleural are in their normal anatomic locations
#2 lung sliding is dynamic and occurs only when the patient breathes
The absence of lung sliding has a specificity of __ to __% for the diagnosis of pneumothorax in people.
88-98%
T/F: The true sensitivity and specificity of absent lung sliding to diagnose pneumothorax in small animal patients remains unknown
true
What are the 5 criteria that define a B line?
1 they are unfading vertical white lines
#2 they originate at the lung surface
#3 they move in synchrony with lung sliding
#4 they extend into the far field
#5 they obscure A lines if present
(#1-3 are obligatory whereas #4-5 are not always present)
Definition/Ultrasound Sign: The rhythmic movement of the visceral pleura in opposition to the parietal in synchrony with the cardiac rhythm
lung pulse (when present it rules out PTX)
Definition/Ultrasound Sign: The site within the thorax where the visceral pleura of the lung recontacts the parietal pleura of the thoracic wall in patients with pneumothorax
Lung point
Definition/Ultrasound Sign: (Rare, not yet reported in vet med) Detected with both edges of trapped pleural air can be scanned and visualized as 2 lung points alternating on the 2 opposite sides of the probe moving in opposite directions
double lung point
What is the ESSENTIAL feature of a double lung point (ultrasound finding)?
the lung points appear to move in opposite directions
Definition/Ultrasound Sign: Movement of A lines in the opposite direction to classic lung sliding during inspiration (only seen on dogs under anesthesia experimentally)
Reverse sliding sign
Definition/Ultrasound Sign:A vertical edge artifact created when air overlies soft tissue structures or less commonly pleural effusion within the thorax. Usually its visualized at the caudal border of the lung near the diaphragm
normal curtain sign
Definition/Ultrasound Sign: Defined as the movement of the vertical air edge artifact (pneumothorax induced) in the OPPOSITE direction of abdominal contents
asynchronous curtain sign
Definition/Ultrasound Sign: Horizontal lines that originate from the pulmonary-pleural line. Air reverberation artifacts
A lines
Definition/Ultrasound Sign: Alveoli filled with edema. Move in synchrony with phases of respiration
B line
What are the sites of Vet BLUE?
Caudodorsal (Cd)
Perihilar (Ph)
Middle (Md)
Cranial (Cr)
DH view
*9 total, left and right + DH
What does VetFAST-ABCDE stand for…
Veterinary focused assessment with sonography for trauma - airway, breathing, circulation, disability, and exposure
VetFAST-ABCDE is an adaptation of human POC emergency ultrasound to assess thoracic and abdominal injury, CV status and what other organ?
optic nerve diameter to assess for changes in ICP
What is the major limitation of VetFAST-ABCDE?
Probe is only used to image intercostal spaced 4-9
In a study by Dicker at al (JVECC 2020) comparing the diagnosis of pulmonary contusions using Vet BLUE, TXR and thoracic CT, did Vet BLUE had a higher or lower sensitivity than TXR for diagnosis of pulmonary contusions?
Higher (90.5% sensitive and 87.5% specific)
What are general limitations of lung ultrasound?
1 can only image lung pathology that reaches lung periphery
Definition/Ultrasound Finding: Vertical hyper echoic beams similar to B lines that origination from air in the SQ
E lines
Global FAST incorporates what two imaging protocols?
TFAST echocardiography and Vet Blue
If a patient is fluid responsive, what will you observe in the CVC between the phases of respiration?
35-50% change in height of CVC
For each Vewt BLUE site, how many ICS spaces should be surveyed?
3 ICS at each site
What is the Vet BLUE B line scoring system?
0 (no B lines)
1 (single B line)
2 (2 B lines)
3 (3 B lines)
greater than 3 (more than 3 B lines)
Infinity (confluent over enter ICS)
*performed by taking the highest number of B lines over a single ICS at each site
What does AIS stand for?
alveolar interstitial syndrome (basically what B lines are, alveolar interstitial edema)
Does lung fibrosis create true or pseudo-B lines?
Pseudo-B lines
(True B lines imply fluid which is not present with fibrosis)
Definition/Ultrasound Finding: Hyperechoic foci within consolidated lung with irregular borders in the far field
shred sign
Definition/Ultrasound Finding: Complete lack of aeration within consolidated lung; hepatized lung
tissue sign
Definition/Ultrasound Finding: Aerated alveoli cuffing soft tissue characterized by hypoechoic or anechoic oval or circle with hyperechoic far border
nodule sign
Definition/Ultrasound Finding: Combination of the shred and tissue signs and represents lung infarction
wedge sign
(can be hard to differentiate between shred and pneumonia)
Definition: Mismatch between the patient’s own inspiratory and expiratory times and the mechanical ventilator delivery times
dyssynchrony
What are the effects of MV dyssynchrony?
Overload respiratory muscles
Increased alveolar dissension w/ risk of lung injury
Compromise sleep quality resulting in increased sedation/delirium
What are the categories of patient ventilatory dyssynchrony?
1 Dyssynchrony of the trigger phase (delayed and ineffective efforts, auto triggering)
#2 Dyssynchrony of the flow phase
#3 Dyssynchrony of the cycling phase (premature cycling off, delayed cycling off)
#4 Reverse triggering
What is the type of dyssynchrony where the patient attempts to start a breath but the ventilator trigger fails?
Ineffective efforts
(the ventilator is unable to detect the patient’s effort so the inspiratory phase of the mechanically delivered breath is not started)
What is the gold standard to assess ineffective triggering during MV?
1 negative deflection in esophageal pressure (Pes)
#2 significant increase in electrical activity of the diaphragm
(neither of these are practical)
What is a practical way of assessing ineffective triggering during MV (compared to gold standard)?
decrease in airway pressure-time waveform along with an increase in airflow during expiration
(the increase in flow is small and is the patient trying to take and breath, but no MV breath follows it)
What type of dyssynchrony results in delay between the start of the neural and mechanical inspiration?
triggering delay
What is the most important cause of ineffective efforts and delayed triggering related to patient disease?
the presence of dynamic hyperinflation that generates intrinsic PEEP (PEEPi)
(Can think of it like breath stacking; the patient’s ventilatory muscles must first counterbalance PEEPi in the alveoli before the ventilator senses any variation in flow or pressure and then triggers the next breath)
The most important cause of ineffective efforts and delayed triggering related to patient disease is the presence of dynamic hyperinflation that generates intrinsic PEEP (PEEPi). How will this appear on a flow waveform?
An abrupt expiratory flow end before a triggered breath
What type of dyssynchrony occurs where the patient makes no attempt at breathing and the ventilator will trigger a breath on its own?
autotriggering
What are causes of auto triggering?
(anything that causes a change in pressure or flow by the ventilatory that is unrelated to patient efforts)
circuit leaks
very sensitive trigger settings that will activate from thoracic pressure changes in the cardiac cycle (more common with cardiac pacing)
In a patient triggered breath, will you see an increase, decrease, or no change in airway pressure prior to the start of the ventilator breath?
decrease in airway pressure (normal)
What type of dyssynchrony results in insufficient flow delivery too low for the patient’s respiratory need?
dyssynchrony of the flow phase
In a patient that has a relative flow starvation, what will you see during the inspiration phase in the airway pressure curve?
airway pressure falls giving the pressure time curve a scooped out look which can be severe enough to decrease peak airway pressure
What type of dyssynchrony occurs when the neural inspiratory time and the ventilator inspiratory time are mismatched?
cycling dyssynchrony
What type of dyssynchrony occurs when the mechanical inspiratory time (Ti) is shorter than the neural Ti leaving the patient air hungry?
short cycling dyssynchrony
When short cycling dyssynchrony is bad enough, what other type of dyssynchrony can occur?
double triggering (aka breath stacking)
What type of dyssynchrony results in a second mechanical breath being triggered before full deflation of the first one?
double triggering (aka breath stacking)
What is the major consequence of double triggering dyssynchrony?
increased total tidal volume
What is the most common dyssynchrony and the incidence worsens with lung injury and high respiratory drive?
double triggering (aka breath stacking)
What is the detrimental effect of an inverse ratio?
increasing mean airway pressure (worsens lung injury)
What type of dyssynchrony results is a longer ventilator inspiratory time than patient neural inspiratory time?
delayed cycling off
With delayed cycling off, this can be recognized by what change in the airway pressure curve?
abrupt spike in airway pressure near the end of mechanical inspiration on the pressure time waveform
Premature or delayed cycling can be minimized by adjusting what in pressure support ventilation?
adjusting the pressure rise time (increase if delayed cycling)
What is the oxygenation goal (PaO2 and SpO2) during MV?
PaO2 55-80 mm Hg
SpO2 88-95%
What is normal respiratory compliance?
100 ml/cm H2O
Definition: the change in lung volume per unit change in pressure in the absence of flow
static compliance
Definition: The change in volume divided by change in pressure, measured during normal breathing, between points of apparent zero flow at the beginning and end of inspiration
dynamic compliance
What are the components of static compliance?
chest wall compliance
lung tissue compliance
What are the components of dynamic compliance?
chest wall compliance
lung tissue compliance
airway resistance
Term used to describe the difference between inspiratory and expiratory compliance
hysteresis