Exam 2 Flashcards
ventilation def
the movement of gas into and out of the lungs
what does adequate spontaneous ventilation require
sufficient Vt, RR, and minute volume to support O2 and CO2 removal, while maintaining acid-base balance
Single best clinical index of ventilation
PaCO2
Hypoventilation, hyperventilation, normal values
Normal 35-45 mmHg
Hypoventilation > 45 mmHg
Hyperventilation < 35 mmHg
anatomic deadspace def (and normal)
vol of gas in conducting airways down to terminal bronchioles
Normal 1mL/ lb IBW (~150mL)
alveolar deadspace (and normal)
alveoli that are ventilated w/o perfusion
Normal 0
what diseases increase alveolar deadspace
deadspace diseases; emphysema and PE
physiologic deadspace def (and normal)
total fxnal DS volume that consists of the alveolar and anatomic DS
VDphys = VDanat + VDalv
Normal phys DS = anat DS
Phys DS > anat DS with DS disease (ex emphysema and PE)
mechanical DS def
volume of rebreathed gas d/t mechanical device (ex ventilator tubing)
alveolar ventilation def (and normal)
vol of gas reaching alveoli that are ventilated AND perfused per min
Normal 4-5Lpm
most common reason for initiating mechanical ventilatory support
acute respiratory failure
what is ventilatory capacity affected by
respiratory drive, lung function, ventilatory workload, and ventilatory muscle strength
ventilatory requirements are determined by
oxygenation status, CO2 production, lung function, circulatory balance, acid base production
causes of ARF
- PNA
- ARDS
- Trauma
- Sepsis
- Post op respiratory failure
- COPD exacerbation
early manifestations of ARF
- Tachycardia
- Tachypnea
- Diaphoresis
- Anxiety
- Respiratory distress
signs of ARF
- Decreased resp drive
- Accessory muscle use
- Intercostal retractions
- Chest wall & diaphragmatic asynchrony
- Decreased chest wall excursion
- Apnea
goals for mechanical ventilatory support
- Provide adequate alveolar ventilation
- Ensure adequate tissue oxygenation
- Restore & maintain acid-basis balance
- Decrease WOB
- Normalize alveolar ventilation & PaCO2
- Correct respiratory & metabolic acidosis
- Reverse hypoxemia
- Relieve respiratory distress
indications for mechanical ventilation
apnea, acute vent failure, impending vent failure, refractory hypoxemia,
what do you do if a peds pt is apneic
check for foreign body aspiration
causes of apnea
cardiac arrest, MI, trauma, shock, OD, spinal cord injuries, neuro disease, general anesthesia, paralytics
acute vent failure def
sudden increase in PaCO2 w a decrease in pH
what pH indicates mech vent needed
pH < 7.25
chronic vent fail def
increase in PaCO2 but pH normal d/t metabolic compensation
impending vent failure def
vent failure likely to occur in immediate future
what does IVF often lead to
elective intubation/ventilation
what do you try before elective intubation
HHF/HFNC for 30-120 mins
wdyd for a COPD pt w IVF and pH > 7.25
BiPAP trial
how to dx refractory hypoxemia
FiO2 increase > 10% & PaO2 increase < 5 mmHg
P/F ratio def
PaO2/FiO2 - measure the effectiveness of O2 transfer across the lung
P/F ratio classifications
- Mild ARDS: P/F 200-300 mmHg (while on PEEP 5)
- Mod ARDS: P/F 100-200 mmHg (while on PEEP 5)
- Severe ARDS: P/F < 100 mmHg (while on PEEP 5)
why do ARDS pts have severe oxygenation problems
increased intrapulmonary right to left shunt
full ventilatory support def
provides 100% of pt’s vent needs
full vent support is available through
VC and PC
types of full vent support
AC/VC, AC/PC, SIMV/VC, SIMV/PC
how does a ventilator (on full support) minimize amt of pt effort
by delivering adequate Vt, RR, and minute volume
can spont breathing pts trigger vent in CMV
YES; if pt goes apneic, vent will deliver set breath
partial vent support def
Requires pt to continue to spont breathe to maintain adequate alveolar ventilation but provides enough support required to maintain good PaCO2
what is partial vent support available through
SIMV
what rate requires pt to breathe on SIMV
RR < 8-10bpm
VC-CMV
all mandatory breaths, pt/time triggered, volume/time cycled
what does the clinician set in VC-CMV
desired Vt, minimum RR, insp peak flow, insp flow waveform, trigger sensitivity
advantages of VC-CMV
i. Constant Vt (even when compliance/Raw changes)
ii. Guaranteed minimum ventilation delivered (d/t set RR and Vt)
iii. Provides full vent support
disadvantages of VC-CMV
i. Unsafe PIPs may occur (d/t reduced compliance or increased Raw)
ii. Unsafe Pplat may occur (d/t inappropriate Vt or reduced compliance)
iii.Improper trigger sensitivity or inadequate flow rates may increase WOB
PC-CMV
all mandatory breaths, pt/time triggered, time cycled
what does the clinician set in PC-CMV
insp pressure, RR, I-time (or insp % time), insp rise time/ramp, trigger sensitivity
advantages of PC-CMV
i. Constant insp pressure
ii. Desired Vt can be achieved by adjusting PIP or I-time
disadvantages of PC-CMV
i. Vt varies d/t changes in pt effort, system compliance, or Raw
ii. Increased PEEP w/o increased PIP = decrease ∆P and Vt
iii. Increased PIP and Pplat may cause barotrauma or VILI
VC-SIMV
Breaths can be mandatory, time/pt triggered, volume/time cycled
PS normally added, insp pressure support pt triggered, pressure limited, flow cycled
what does the clinician set in VC-SIMV
Vt, min RR, peak flow, trigger sensitivity for mandatory breaths
(PS and tube compensation for spont breaths)
advantages of VC-SIMV
- reduced mean airway pressures (may maintain CO & BP)
- Maintenance of ventilatory muscle activity, strength and coordination
- Reduced need for sedation or paralytics
disadvantages of VC-SIMV
- Increased WOB associated with ETT/trach tubes during spont breathing
- Spont breathing with high ventilatory workloads may cause ventilatory muscle fatigue and dysfxn
PC-SIMV
Breaths mandatory/spont, pt/time triggered, pressure limited, time cycled
what does the clinician set in PC-SIMV
pressure control level, min RR, I-time, trigger sensitivity for mandatory breaths
(PS and tube compensation for spont breaths)
advantages of PC-SIMV
- Constant PIP
- Desired Vt can be achieved by adjusting pressure control level (∆P=PIP-PEEP), or I-time
disadvantages of PC-SIMV
- High mean airway pressures may reduce venous return and CO
- Too rapid rise times may cause pressure spike in insp
- Vt varies d/t changes in effort, compliance, resistance
PS-CSV aka
PS-CPAP
PS-CPAP
PS provided with each breath
- Variable Vt, RR, flow, I-time
what does the clinician set in PS-CPAP
trigger sensitivity, pressure support, I-time, and flow termination
CPAP def
continuous positive airway pressure; spont breathing at constant elevated pressure during insp and exp
advantages of PS-CPAP
- May improve pt-ventilatory synchrony and pt comfort
- As PS increases, spont Vt increases and WOB decreases
- May increase lung SA for gas exchange, improve oxygenation, prevent alveolar collapse/atelectasis
- Often used for SBTs
disadvantages of PS-CPAP
- CPAP increases mean airway pressure, mean intrathoracic pressure, and FRC
initial Vt
6-8mL/kg IBW; must be adjusted to maintain Pplat < 28-30 cmH2O
initial RR
12-16bpm
normal min vent
5-10Lpm
IBW equation
Male 50 + 2.3(ht - 60)
Female 45.5 + 2.3 (ht-60)
initial PC
12-15 cmH2O above PEEP
initial PS
12-15 cmH2O above PEEP
what pressure should PIP remain
< 40 cmH2O
RR should remain below
25 bpm
Pplat should remain below
28-30 cmH2O
pressure trigger initial
-0.5 to -1.5
flow trigger initial
1-2 Lpm below baseline
what does PEEP/CPAP do
restores FRC, improves and maintains lung volumes, and improves oxygenation
temp for inspired gas
35 +/- 2C
positive pt-vent interaction
results in adequate oxygenation/ventilation, decreases WOB and promotes pt comfort
poor pt-vent interaction
asynchrony, increase WOB, pt discomfort, poor oxygenation/ventilation
what trigger is more comfortable for pts
flow trigger
trigger work
portion of WOB performed by pt to trigger vent
what can increase trigger work
inappropriate trigger sensitivity, autoPEEP
missed triggering
pt insp effort does not trigger vent
missed triggering causes
autoPEEP
trigger delay
pt tries to initiate breath but vent delays in giving it
double triggering
pt receives 2 consecutive breaths from vent before exp
double triggering is d/t
pts breathing longer than vent I-time
double trigger tx
increase I-time
auto triggering
vent initiates insp w/o corresponding pt effort d/t inappropriate vent trigger sensitivity settings
what causes autotriggering
triggers are too sensitive; cuff leak; system leak; water in system
reverse triggering
time triggered vent breath stimulates diaphragm -> diaphragm contracts -> triggers next vent breath
reverse trigger tx
reduce sedation
PaO2 normal and clin goal
normal 95
clin goal 60-99
SaO2 norm and clin goal
normal 97
clin goal 90-99
Hb norm and clin goal
norm men 15
norm women 12-15
clin goal >8
CaO2 norm and clin goal
norm 19.8
clin goal >16
CO norm and clin goal
norm 5
clin goal varies d/t pt size
SV norm and clin goal
norm 70
clin goal 60-80
HR norm and clin goal
norm 80-100
clin goal 80-100
BP norm and clin goal
norm 120/80
clin goal within norm range
MAP norm
90
LIP
overcoming distending pressure to open alveoli; level at which compliance improves
PEEP & LIP
PEEP set 2 cmH2O above LIP
UIP
lung overdistension begins
30 for 30
PEEP 30 for 30 secs
40 for 40
PEEP 40 for 40 secs
3 chambers of chest tube collection system
collection chamber, water seal chamber, suction chamber
collection chamber
Drainage from chest flows into collection chamber; made of transparent material w calibration markings to allow for observation of drainage fluid
water seal chamber
filled with sterile water 2 cm in depth
how is the water seal chamber a one way valve
allows gas to exit from pleural space via chest tube on exhalation while preventing air from entering pleural cavity on inhalation
what does bubbling mean in the water seal chamber
there is an air leak
does increasing the suction source increase chest tube suction
no, only increases airflow and noise
where should the chest tube be positioned
below the pt’s chest; normally on floor
RSBI
rapid shallow breathing index; > 30bpm with Vt <300mL are associated with need for mech vent
RSBI equation
RSBI = f/Vt (L)
RSBI classification
< 105 = adequate spont breathing, high chance of successful liberation
> 105 = inadequate spont breathing, failure of vent wean
dynamic compliance equation
Cdyn = Vt / (PIP - PEEP)
static compliance equation
Cstat = Vt / (Pplat - PEEP)