Establishing The Need For Mechanical Ventilation 2023
Questions and Answers Complete
What are the physiological objectives for mechanical ventilation?
1. Support or manipulate pulmonary gas exchange
Achieve normal alveolar ventilation
Maintain normal oxygenation
2. Increase lung volume
Prevent atelectasis with adequate end inspiratory lung inflation
Restore and/or maintain normal FRC
3. Reduce work of breathing
What are the clinical objectives for mechanical ventilation?
1. Reverse acute respiratory failure (ARF)
2. Reverse respiratory distress
3. Reverse hypoxemia
4. Prevent or reverse atelectasis
5. Reverse respiratory muscle fatigue
6. Allow for sedation, paralysis or both-do this for surgery
7. Reduce systemic or myocardial oxygen consumtion
8. Minimize complications and reduce mortality
What is the overall goal of mechanical ventilation?
Get the patient back to normal physiologic state.
When is mechanical ventilation indicated?
1. When the patient is in respiratory distress
- Evaluate the level of consciousness (LOC)
-Evaluate appearance of skin
Cyanosis of lips or nail beds, pale or diaphoretic
-Evaluate vital signs
2. Acute Respiratory Failure
3. Apnea-no breathing at all
4. ABG-pH < 7.30 AND PaCO2 > 50
5. Severe hypoxemia (PaCO2 < 50) despite increased FIO2
What is the definition of acute respiratory failure?
Ventilation is absent or is insufficient to maintain o2 intake and CO2 clearance.
What is the clinical definition of acute respiratory failure?
pH < 7.30 AND PaCO2 > 50 and/or sever oxygen failure. That is respiratory failure with
a P to F ratio is < 60
What are conditions that frequently lead to respiratory failure?
Central nervous system disorders
Neuromuscular disorders
Increased work of breathing
What are the 2 major types of central nervous system disorders?
Reduced ventilatory drive-breathe less
Increase ventilatory drive- breathe more, generally more the kidneys
What are causes of reduced ventilatory drive?
, Depressant drugs (narcotics, anesthesia agents)
Brain or brainstem lesions (tumor)
Hypothyroidism
Sleep apnea syndrome
What are causes of increased ventilatory drive?
Increased metabolic rate (increases CO2 production)-fever, exercise
Metabolic acidosis-diabetes, renal failure
Anxiety
What are the causes of neuromuscular disorders?
Paralytic disorders-myasthenia gravis, tetanus, Guillain-Barre syndrome, ALS, muscular
dystrophy
Paralytic drugs-curare, nerve gase, succinylcholine (used during intubation-short acting,
pancuronium (pavulon), (long acting), Vecuronium (norculon)(used for OR procedure
short acting
Neuromuscular Transmission Blocking Drugs-aminoglycoside antibiotics, calcium
channel blockers
What are conditions that lead to work of breathing?
Pleural lesions-pleural effusions, hemothorax, emphema, pneumorthorax
Chest wall deformities-flail chest, rib fractures, kyphoscoliosis, obesity
Increased airways resistance (mucus, broncho constriction, airway inflammation.
What are the critical values in an ABG that may indicate a need for mechanical
ventilation?
pH < 7.30 AND PaCO2 >50
PaCO2 < 60 with FIO2 > 60%
P(A-a)O2 > 450 (on 100% O2)
PaO2/FIO2 < 200 (Normal is 380-476)
What are the physiological measurements in respiratory failure?
VC=vital capacity
TV=tidal volume
RR=respiratory rate
MIP=maximum inspiratory pressure
FEV1=forced expiratory volume in one second
PEFR=peak expiratory flow rate
MEP=maximum expiratory pressure
What is the definition of vital capacity?
The amount of air from maximum inspiration to maximum expiration.
What is normal vital capacity?
65-75 ml/kg IBW
What is considered an inadequate vital capacity to maintain normal ventilation and
cough mechanisms?
< 15 ml/kg
What is the definition of ideal body weight?
The optimal weight for one's height, age, sex and body build.
What is the calculation to determine ideal body weight for a male?
Questions and Answers Complete
What are the physiological objectives for mechanical ventilation?
1. Support or manipulate pulmonary gas exchange
Achieve normal alveolar ventilation
Maintain normal oxygenation
2. Increase lung volume
Prevent atelectasis with adequate end inspiratory lung inflation
Restore and/or maintain normal FRC
3. Reduce work of breathing
What are the clinical objectives for mechanical ventilation?
1. Reverse acute respiratory failure (ARF)
2. Reverse respiratory distress
3. Reverse hypoxemia
4. Prevent or reverse atelectasis
5. Reverse respiratory muscle fatigue
6. Allow for sedation, paralysis or both-do this for surgery
7. Reduce systemic or myocardial oxygen consumtion
8. Minimize complications and reduce mortality
What is the overall goal of mechanical ventilation?
Get the patient back to normal physiologic state.
When is mechanical ventilation indicated?
1. When the patient is in respiratory distress
- Evaluate the level of consciousness (LOC)
-Evaluate appearance of skin
Cyanosis of lips or nail beds, pale or diaphoretic
-Evaluate vital signs
2. Acute Respiratory Failure
3. Apnea-no breathing at all
4. ABG-pH < 7.30 AND PaCO2 > 50
5. Severe hypoxemia (PaCO2 < 50) despite increased FIO2
What is the definition of acute respiratory failure?
Ventilation is absent or is insufficient to maintain o2 intake and CO2 clearance.
What is the clinical definition of acute respiratory failure?
pH < 7.30 AND PaCO2 > 50 and/or sever oxygen failure. That is respiratory failure with
a P to F ratio is < 60
What are conditions that frequently lead to respiratory failure?
Central nervous system disorders
Neuromuscular disorders
Increased work of breathing
What are the 2 major types of central nervous system disorders?
Reduced ventilatory drive-breathe less
Increase ventilatory drive- breathe more, generally more the kidneys
What are causes of reduced ventilatory drive?
, Depressant drugs (narcotics, anesthesia agents)
Brain or brainstem lesions (tumor)
Hypothyroidism
Sleep apnea syndrome
What are causes of increased ventilatory drive?
Increased metabolic rate (increases CO2 production)-fever, exercise
Metabolic acidosis-diabetes, renal failure
Anxiety
What are the causes of neuromuscular disorders?
Paralytic disorders-myasthenia gravis, tetanus, Guillain-Barre syndrome, ALS, muscular
dystrophy
Paralytic drugs-curare, nerve gase, succinylcholine (used during intubation-short acting,
pancuronium (pavulon), (long acting), Vecuronium (norculon)(used for OR procedure
short acting
Neuromuscular Transmission Blocking Drugs-aminoglycoside antibiotics, calcium
channel blockers
What are conditions that lead to work of breathing?
Pleural lesions-pleural effusions, hemothorax, emphema, pneumorthorax
Chest wall deformities-flail chest, rib fractures, kyphoscoliosis, obesity
Increased airways resistance (mucus, broncho constriction, airway inflammation.
What are the critical values in an ABG that may indicate a need for mechanical
ventilation?
pH < 7.30 AND PaCO2 >50
PaCO2 < 60 with FIO2 > 60%
P(A-a)O2 > 450 (on 100% O2)
PaO2/FIO2 < 200 (Normal is 380-476)
What are the physiological measurements in respiratory failure?
VC=vital capacity
TV=tidal volume
RR=respiratory rate
MIP=maximum inspiratory pressure
FEV1=forced expiratory volume in one second
PEFR=peak expiratory flow rate
MEP=maximum expiratory pressure
What is the definition of vital capacity?
The amount of air from maximum inspiration to maximum expiration.
What is normal vital capacity?
65-75 ml/kg IBW
What is considered an inadequate vital capacity to maintain normal ventilation and
cough mechanisms?
< 15 ml/kg
What is the definition of ideal body weight?
The optimal weight for one's height, age, sex and body build.
What is the calculation to determine ideal body weight for a male?
