Establishing Need for Mech Vent Pilbeam 4 Flashcards
includes Critical values!
What are the PHYSIOLOGICAL objectives of mechanical ventilation
- Support or manipulate pulmonary gas exchange (alveolar ventilation/CO2 levels and alveolar oxygenation (CaO2 x cardiac output)
2 Increase lung volume (prevent/treat atelectasis w/PEEP and restore/maintain FRC) - Reduce work of breathing
- Minimize cardiac impairment
What are the CLINICAL objectives of mechanical ventilation?
Reverse acute respiratory failure
Reverse respiratory distress
Reverse hypoxemia
Prevent/reverse atelectasis and maintain FRC
Reverse respiratory muscle fatigue
Permit sedation, paralysis or both (ie surgery)
Reduce systemic or myocardial oxygen consumption
Minimize associated complications and reduce mortality
Recognizing the patient in distress- what should you assess?
- Level of consciousness and sensorium
- Appearance: evidence of cyanosis, color, diaphoresis?
- Vital signs: RR, HR, BP, temp, SaO2
Sudden onset dyspnea- signs and symptoms
anxious, eyes wide open, (panic) nostril flare, furrowed brow, diaphoretic, flushed or ashen, use of accessory breathing muscles, paradoxical breathing, abnormal breath sounds, tachycardia, arrhythmias, hypotension; patient complants of SOB
What is the definition of acute respiratory failure (ARF)
any condition (rapid onset) where respiratory activity is inadequate to maintain 02 uptake and CO2 clearance
A patient is considered to be in ARF status when their ABG results are what?
(pH, PaCO2, PaO2)
ph < 7.25
PaCO2 > 50
PaO2 < 60
List the 2 types of ARF
Type I hypoxic respiratory failure
Type II hypercapnic respiratory failure
Type I is also called _____ _______ accompanied by hypercapnia
pump failure
Type II is also called lung failure accompanied by hypoxemia or ________ failure.
ventilatory failure
What are the 4 causes of hypoxemic respiratory failure?
1 V/Q mismatch (relative shunt)
2 diffusion defects
3 right to left shunting (severe shunt)
4 alveolar hypoventilation
5 inadequate inspired O2 (high altitude, CO poisoning, aging and related increased dead space)
Yes there are 5 causes but Denise always says “the 4 major”
What is the ventilatory pump?
the respiratory muscles, thoracic cage, and nerves that are controlled by respiratory centers in the brainstem
What 3 types of disorders can lead to ventilatory pump failure?
1 Central nervous system disorders
2 Neuromuscular disorders
3 Disorders that increase the work of breathing
What are early signs and symptoms of hypoxia?
tachycardia and tachypnea
Does severe shunting respond to O2?
NO
Severe hypercapnia eventually leads to CO2 narcosis, _______ _______, coma and death
cerebral depression
Severe hypercapnia eventually leads to _____ _____ , cerebral depression, coma and death
CO2 narcosis (reduction of the hypoxic drive/ respiratory effort)
What is the differential diagnosis for CHRONIC hypercapnic respiratory failure and ACUTE hypercapnic respiratory failure?
The severity of the change in pH.
In ACUTE hypercapnic RF, pH decreases 0.08 for every 10 mmHg increase in PaCO2. In CHRONIC hypercapnic RF, pH decreases 0.03 for every 10 mmHg increase in PaCO2
In chronic hypercapnia, ph decreases _____ for every _____ mmHg increase in PaCO2
0.03 for every 10 mmHg
In acute hypercapnia, ph decreases _____ for every _____ mmHg increase in PaCO2
0.08 for every 10 mmHg
What is congenital central hypoventilation syndrome (CCHS) (aka primary alveolar hypoventilation aka Ondine’s curse)?
Congenital or developed sleep disorder wherein patient’s suffer from respiratory arrest during sleep and involving an inborn failure of autonomic control of breathing due to congenital defect or developed due to severe neurological trauma to the brainstem
Elevation of PaCO2 levels lead to a(n) _________ in cerebral blood flow caused by ___________.
increase - caused by dilation of cerebral blood vessels
List some of the causes of decreased respiratory drive (as found in ARF- hypercapnic, CNS related)
depressant drugs, head trauma, sleep disorders, acid/base abnormalities, inappropriate O2 therapy, hypothydroidism
List some of the causes of increased respiratory drive (as found in ARF- hypercapnic, CNS related)
increased metabolic rate, metabolic acidosis, anxiety associated with dyspnea
What happens when a person’s PaCO2 rises above 70 mmHg?
PaCO2 greater than 70 has a CNS depressant effect reducing respiratory drive and ventilation
T/F Hypoxia normally acts as a respiratory stimulant
true
Normally the work of breathing consumes __ to ___ % of total oxygen consumption
1 to 4%
What are two (physiological) causes of increased work of breathing?
increased deadspace (as in COPD/ emphysema) and increased airway resistance (as in chronic bronchitis or asthma)
Should mechanical ventilation be used to control ICP in patients with brain injury?
clinical evidence says no- brain injury by itself is not an indication for intubation and CMV
What are the normal and the critical values for dead space to tidal volume ratio? (Vd/Vt)?
normal values are 30 to to 40% (0.3 to 0.4)
critical value is a ratio greater than 60^ (0.6)
What are the normal and critical values for PaO2 (indicating the need for O2 therapy or PEEP/CPAP)
Normal tension is 80-100
Values less than 70 (on FIO2 above 60) require intervention
What are the normal and critical values for P(A-a)? [arterial to alveolar difference]
Normal values are 3 to 30
Critical values are >450 on O2
What are the normal and critical values for the ratio of arterial to alveolar PO2 (PaO2/PAO2)
Normal is 75% (or 0.75)
Critical value is less than 15% (0.15)
Whar are the normal and critical values for the PaO2/FIO2 (P/F ratio)
Normal is 475
Critical value is below 200
MIP (maximum inspiratory pressure) and vital capacity (VC) are test results performed to assess what?
respiratory muscle strength of patients (generally performed on those with neuromuscular disorders)
Should mechanical ventilation be used for patient’s with flail chest?
Only when it is associated with imminent respiratory failure
What are the normal and critical values for MIP, mean inspiratory pressure (aka NIF, negative inspiratory force)?
Normal adult range is -100 to -50
Critical value is -20 to 0
What are the normal and critical values for MEP (maximum expiratory pressure)
Normal is 100 cmH20
Critical value is <40
What are the normal and critical values for tidal volume (Vt) in mL/kg
Normal is 5-8 mL/kg
Critical value is less than 5
What are the normal and critical values for VC (vital capacity) in mL/kg
Normal is 65-75
Critical value is <10-15 mL/kg
What are the normal and critical values for respiratory frequency (breaths per minute)
Normal is 12 to 20
Critical value is greater than 35 b/m
What are the normal and critical values for forced expired volume at 1 second (FEV1) in mL/kg
Normal is 50-60
Critical value is less than 10 ml/kg
What are the normal and critical values for peak expiratory flow rate (PEFR) in L/min
Normal is 350 to 600
Critical value is 75 to 100 L/min
Measurement of MIP must begin as closely as possible to the patient’s _______ ________
residual volume (from maximal exhalation)
A MIP of -20 will generate a tidal volume large enough for the patient to _________
produce a good cough
What is the definition of vital capacity?
the volume of air that can be maximally exhaled following a maximum inspiration
What is the formula used to obtain a male patient’s ideal body weight?
Men: 106 + (6 x ht in inches - 60)
What is the formula used to obtain a female patient’s ideal body weight?
Female: 100 + (5 x ht in inches -60)
An elevated PaCO2 would suggest that _______ is increased relative to tidal volume
dead space
How do you calculate arterial oxygen content? (what is the formula)
CaO2= [(Hb x 1.34) x SaO2] + (PaO2 x 0.003)
To treat arterial hypoxemia caused by hyperventilation you should _____.
increase alveolar ventilation
To treat arterial hypoxemia caused by low V/Q ratio, you should _____.
use PEEP or CPAP
The PaO2/PAO2 is expressed in a percentage. What does this number mean? (what is it telling you?)
what percentage of the oxygen available in the alveoli is diffusing into the pulmonary capillaries
According to Pilbeams on room air the normal ranges for P/F ratios should be:
350-450. The lower the number, the more severe the problem.
List the 4 standard criteria for instituting Mechanical Ventilation
1 Apnea or absence of breathing
2 Acute ventilatory failure
3 Impending ventilatory failure
4 Refractory hypoxemic respiratory failure with increased work of breathing or an ineffective breathing pattern
T/F No single value for PaO2, PaCO2 or pH indicates a need for invasive ventilation
TRUE
Non invasive positive pressure ventilation (NIV) is the treatment of choice for acute on chronic respiratory failure unless ________ is also a factor.
cardiovascular instability
What are the indications for using NIV?
at least 2 of the following:
- Resp rate greater than 25 b/m
- Moderate to severe acidosis (pH 7.25 to 7.30; PaCO2 45 to 60
- Moderate to severe dyspnea with use of accessory muscles and paradoxical breathing
What are the absolute contraindications for NIV?
respiratory arrest, cardiac arrest, non-respiratory organ failure (encephalopathy, GI bleeding or surgery, hemodynamic instability (with or w/out unstable cardia angina), upper airway obstruction, inability to protect the airway and/or high risk of aspiration, inability to clear secretions, facial or head trauma/surgery
What are the relative contraindications for NIV
cardiovascular instability; uncooperative patient (impaired mental status, hypersomnolence); copious or viscous secretions, fixed nasopharyngeal abnormalities, extreme obesity
