Pediatric and Neonatal Mechanical Ventilation Praveen Khilnani
Page numbers followed by f refer to figure, fc refer to flow chart, and t refer to table
Abscesses, multiple 119f
Accidental extubation, chances of 37
Acid-base disorders 128, 129t
Acidemia 128
Acidosis 53, 129
acute respiratory 129
chronic respiratory 129
metabolic 36, 129
severe lactic 38
Activated clotting time 207
Acute respiratory distress syndrome 1, 26, 35, 36, 101, 117, 127, 200
Adaptive pressure
control 98
ventilation 98
Adaptive support ventilation 98, 99, 107
Adult respiratory care system 65
Air 64
entry 82
high-flow 72f
leak 36, 134, 136f
cold light for 82
persistent 203
syndromes 93
Airway 193
clearance 46
disease, obstructive 117
function, preserves 69
obstruction 25, 52, 62
lower 117
pressure 4, 20
high 105
release frequency 104
release ventilation 98, 102, 102t, 103f, 154, 155f
reflexes, control of 14
resistance 7
size 106
type 106
Albuterol 37
Alkalemia 128
acute respiratory 129
chronic respiratory 129
metabolic 129
arterial gradient 203
derecruitment 27
minute ventilation 2
plateau 133
pressure minus ambient pressure 16
recruitment 27
Ambient pressure minus pleural pressure 16
American Heart Association Guidelines 141
American Thoracic Society Guidelines 183
Analgesia 173, 180, 207
Anasarca 20
Antibiotics 207, 208
Anticoagulation 207, 209
Anxiety 118
Apnea 3, 10, 48, 117, 195, 225, 228
frequent 4
monitor 82
of prematurity 61, 67, 82, 117
rule out other causes of 62
ventilation 231
cardiac 195
intractable 204
refractory 204
Arterial blood 203
adequate 48
gas 118, 122
monitoring 127
Arterial lines 118
Arterial oxygen, partial pressure of 23, 43
Arterial oxygenation 27
Arteries, dilate pulmonary 52
Artificial airway, resistance of 166
Artificial noses 176
Ascites 20
Aspiration, subglottic 186
Assist control ventilation 99
Assist ventilation 78f
mode 105f
Asthma 1, 117
childhood 38
severe 35, 37, 40, 47
identify signs of 144, 163
types of 171
Atelectasis 69
Auto-positive end-expiratory pressure 164f
Barotrauma 11, 36, 52, 72, 233
acute 38
Beer-Lambert law 123
Bilevel airway pressure release ventilation 224
Bilevel nasal continuous positive airway pressure 114
Bilevel positive airway pressure 67, 99, 114, 116
Bleeding 210
Blended gas source 57
Blocked nasal passages 68
flow, pulmonary 29
gas 61, 83
capillary 83
target 82
pressure 77
noninvasive 118
Bloodstream infection
catheter-related 180
central line-associated 180
Botulism 24
Brain 44
injury, traumatic 30, 42
Breath 76
cycle time 228
delivery 19
identify type of 144, 148
sounds 122
analysis 104f
pressure 100fc
circuit, humidifier 64
eliminate work of 3
paradoxical 122
periodic 171
reducing work of 70
work of 18, 61, 79, 163
Bronchi 2
Bronchiolitis 117, 67
severe 203
Bronchodilator 161f
Bronchospasm 11, 123
Bubble nasal continuous positive airway pressure 59f
Bulk convection 89
Caffeine 192
waveform 133
normal 126f
Capnograph, normal 134f
Capnography 125, 127, 131, 132, 139f
basic principle of 131
indications for 126
Capnometers, qualitative 133
Capnometry 131, 133
efficacy of 140
Carbon dioxide 89, 102, 132f
monitoring 123
monitors measure 131
partial pressure of 131
removal 207
systemic arterial 18
Carboxyhemoglobin 124
Cardiac arrest 38
Cardiac extracorporeal membrane oxygenation 203
Cardiac failure
congestive 48
situations, acute reversible refractory 203
Cardiac index 204
Cardiac output 233
Cardiomyopathy 40
Cardiopulmonary arrest 202
Cardiorespiratory arrest 31
Cardiorespiratory interactions 40, 41
Cardiothoracic surgery 201
Cardiovascular dysfunction 24
moderate to severe 24
Catecholamines 134
Central hypoventilation syndrome 4, 117
Central nervous system 189
protection 174, 182
severe 203
Central venous
oxygen saturation 204
pressure 44
blood flow 44, 77
ischemia 44
palsy 117
Cerebrospinal fluid 43
Cervical spine injuries 42
bandages 20
indrawing, degree of 73
physiotherapy 177, 178, 192
syndrome, acute 203
trauma 72
wall movement 82
wiggle factor 111
X-ray 50, 82
Choanal atresia 68, 72
Circulatory arrest 134
Clinical pulmonary infection score 184
Close suction system 179f
Clubbing 122
Coma 38
Complete oxygen analyzer 73f
Compliance curve 99
Compressions, cardiac 140
Congenital heart disease
case of 35
management after repair of 28
Consciousness, reduced level of 72
Continuous end-tidal carbon dioxide monitoring, use of 142
Continuous positive airway pressure 4f, 5, 26, 48, 56, 57, 58, 61, 62, 67, 68t, 75, 99, 114, 115, 191, 195, 219, 220, 227
delivery 57
effects of 57
failure of 62
interfaces 57
system, components of 57, 57t
Conventional mechanical ventilation 50
failure of 233
Cough 35, 44
Craniofacial malformations 117
Croup 25
Cyanosis 82, 122
Dead space
calculation 138
ventilation 3
Deflation, physiology of 16
Deoxyribonuclease 179
Diaphoresis 195
Diaphragm, electrical activity of 217
Differential leukocyte count 184
Distress, early sign of 122
Down syndrome 117
Downe's score 81, 82t
Drager Babylog 8000 plus 220, 225f, 226, 226f
Drugs 24
Duchenne muscular dystrophy 117
Dynamic pressure-volume loop 157, 158f
Dyshemoglobinemias 124
Dysplasia, bronchopulmonary 83, 93, 189, 193
Edema, pulmonary 56
Elective high-frequency oscillatory ventilation 93
Electrical muscle stimulation 141
Electrocardiogram 118
Electroencephalogram 182
Emphysema, pulmonary interstitial 93, 95, 193
Empyema 119f
Encephalopathy, hypoxic ischemic 82
End-expiratory lung volume 111
Endotracheal airway, invasive 114
Endotracheal intubation 31
Endotracheal tube 2, 75, 94, 106, 131, 188, 218
around 163f
large 163
placement, verification of 140
size of 76t
weight of 76t
End-tidal carbon dioxide 12, 122, 142
high 134, 135f
monitors, types of 133
sudden rise of 134, 135f
Engström ventilator 223, 224f
Epiglottitis 25
Epinephrine, nebulized racemic 192
Esophageal surgery 117
Exhaled tidal volume 223
Expiratory time 78, 147f, 226, 230
Expired minute volume 5
Expired tidal volume 5
Extracorporeal cardiopulmonary resuscitation 205
Extracorporeal Life Support Organization Guidelines Regarding Extracorporeal Membrane Oxygenation Centers 211
Extracorporeal Life Support Organization Registry Analysis 211
Extracorporeal life support, development of 199
Extracorporeal membrane oxygenation 94, 198, 199, 201, 204, 205, 206f, 207f, 212, 233
complications of 209
current status of 205t
flows, weaning 207, 209
indications of 201
initiation of 208
management 207
summary 209
program, setting up 211
selection criteria for cardiac support 204
support, methods of 200
technique of 205
Extubation 14
failure, causes of 188, 189t
clinical indicators of 14
test 194
Fat laden superficial fascia 56
Feeding 173, 181
Fetal hemoglobin 124
Fever 44
high-grade 35
Figure-of-eight appearance 169f
and volume starvation 168f
asynchrony 163, 168
breath 19
ventilation 78, 79f
monitoring 226
pattern 230
rate 81, 132
sensitivity 230
sensor 77, 218
starvation 146
volume loop 85, 86f, 160, 164f
waveform 147, 148f
Fluids 52
interstitial 43
Fontan procedure 29
Foreign body aspiration 72
Fraction of inspired oxygen 203
Frank-Starling curve 41
Friction rub 122
Functional residual capacity 17, 42, 56, 148
Gas exchange 3, 10
abnormal 3
determinants of 18
principles of 89
Gas flow 1, 58
mechanism of 22
patterns of 21
Gas warming and humidification, importance of 69
distension 60
surgery 117
Glasgow coma
scale 42
score 4
Glucose 134
Gram's satin 184
Guillain-Barré syndrome 24
H1N1 200, 202, 210, 211
influenza 201
Head box oxygen 191
Heart 40
failure 28
congestive 28, 67
rate 73, 81
Heat and moisture exchanger 174176
Heated humidified high flow nasal cannula system 64
components of 64
intraventricular 77, 95, 233
periventricular 189
pulmonary 87
Hernia, congenital diaphragmatic 203, 210
High-flow nasal cannula 58, 66f, 68f
devices 116
oxygen therapy 64, 74
pressure 70
therapy 64
High-frequency oscillators 89, 91
ventilator 232
High-frequency ventilation 22, 89, 217, 220, 225
adverse effects of 95
indications for 93
types of 90
Home ventilation 45
Humidified high-flow nasal cannula 114, 116
Hyaline membrane disease 10, 48, 80, 117, 199
Hyperalimentation 134
Hypercapnia 45, 51, 104
chronic 24
tolerate 51
permissive 11, 27, 36, 39, 83, 104
Hypercarbia 3, 10, 30, 31, 43
Hyperinflation 28
dynamic 38, 162
persistent 39
Hypertension 195
neonatal persistent pulmonary 2
pregnancy-induced 49
pulmonary 181
reactive pulmonary 203
reversible pulmonary 204
Hypertensive crises, pulmonary 181
Hyperthermia 134
Hypertrophy, adenotonsillar 117
Hyperventilation 29, 43
Hypocapnea 233
Hypocarbia 43
Hypoplasia, pulmonary 93
Hypotension 40, 195, 233
sudden 134
Hypoventilation 3, 11, 45, 114
Hypovolemia 40
Hypoxemia 1, 3, 10, 11, 30, 40, 66, 103, 127
permissive 11
refractory 38, 40
severe 31
Hypoxia 52, 53
life-threatening 72
control procedures 173, 180
nosocomial 36
pulmonary 69
Infectious Diseases Society of America Guidelines 183
Inflation, physiology of 16
Influenza A 200
Initial ventilator settings 9, 22, 103, 109
Injury, pharyngeal 42
Inspiration, beginning of 150
Inspiratory flow 218, 226
Inspiratory limb, bowing of 158f
Inspiratory minute volume 228
Inspiratory tidal volume 228
Inspiratory time 5, 10, 22, 49, 50, 77, 78, 80, 147f, 218, 226, 230
Inspired oxygen
concentration 100
determines oxygenation 154
fraction 38
Intensive care unit 173, 200, 215
Intermittent positive pressure
breathing 114
ventilation 191
Interpret pressure-volume loop 144
Intra-aortic balloon pulsation 204
Intracranial pressure 43, 140
basic premises of 43
high 29
Intubation 75
Invasive monitoring 81, 83, 127
Invasive ventilation 50, 144
initiation of 75
Jet ventilation, high-frequency 90
Laryngomalacia 1
Leak test 195
Lethargy 118
Leukomalacia, periventricular 95, 189
Loose stools 44
Low birth weight 188
Low-cardiac output syndrome 204
Lower inflection point 27, 156
Lower limbs, sudden onset weakness of 44
Lower respiratory tract 183
Low-flow systems 132
Low-functional residual capacity 1
Low-peak expiratory flow 164f
Low-tidal volume strategy 36
Lung 41
capacities 17
compliance 7, 203
worsening 123
contusions, post-traumatic 203
chronic 36
obstructive 135, 137f
parenchymal 26
function monitoring 226
inflation 16
acute 101, 127
ventilator induced 83
mechanics 70
normal 22, 152f
opening pressure 156
overdistension of 39f, 123
volumes 17
Magnesium 37
Mainstream devices 131
Mandatory minute ventilation 98, 109, 227
Masimo pulse oximetry 125
Masimo signal technology 125
Mass median aerodynamic diameter 174
Maxillofacial trauma 72
Maximal medical therapy 202
Mean airway pressure 4, 5, 27, 39, 91, 147, 147f, 219, 226
Mean arterial pressure, high 102
Mechanical ventilation 4, 13, 18, 23, 24, 34fc, 37, 40, 42, 47, 75, 188, 215
applied respiratory physiology of 16
basic of 1
disease specific 35
indications of 3
modified conventional 90
optimal management of 49
principles of 18
strategies 35
support 31, 46
aspiration 35, 48, 51
syndrome 51, 52, 81, 82, 93, 198
stained liquor 51
Mental status
impaired 117
worsening 118
Meter dose inhaler 13, 175
Methemoglobin 124
Midazolam 12, 75, 180
Mini-bronchoalveolar lavage 183
Minimal pressure support 14
Minute ventilation 87
Monro-Kellie hypothesis 43
Murray's score 203
inspiratory 20
relaxation 181
Myelitis, transverse 24
Myocarditis 204
Nasal cannula 66, 67f
low-flow 68t
oxygen 66
sizes 65, 67t
Nasal continuous positive airway pressure 191
devices 57
indications for 60
initiation of 61
problems of 59
Nasal flaring 195
Nasal interface 61
types of 58f
Nasal intermittent mandatory ventilation 60, 191
Nasal intermittent positive pressure 48
ventilation 56, 60, 116, 191
delivery of 60
Nasal obstruction 72
Nasal polyps 72
Nasal septal injury 60
Nasal trauma 59
Nasogastric tube in situ 73
Nasopharyngeal continuous positive airway pressure 70
Nasopharyngeal space, mucosal tissue of 69
Nasopharynx 68, 70
Near drowning 203
Nebulization 13
Neonatal hyaline membrane disease 2
Neonatal intensive care unit 61, 64, 81, 188, 199, 220
Neonatal respiratory distress syndrome 35, 49
Neonatal ventilation 48
conventional 48
settings 81
Neonatal ventilator, basic 218
Nerve conduction velocity 45
Neurally adjusted ventilatory assist 109, 217
Neurological diseases 29
Neurological disorders 24
Neuromuscular disease 29, 35, 44, 117
Neuromuscular disorder 24
chronic 45
progressive 45
Neuromuscular weakness 2, 46, 53
Neuroventilatory control sequence 110fc
New tracheostomy, care of 177
Nissen procedure 181
Nitric oxide 199
inhaled 198
Noise pollution 95
Nonbronchoscopic lower respiratory tract sampling 183
Noninvasive monitoring 81, 82, 123
Noninvasive positive pressure
devices 114
ventilation, nocturnal 46
Noninvasive ventilation 45, 47, 114, 115, 117, 118, 120, 188, 225, 227
acute 118
advantages of 115
applications of 117
discontinue 118
equipment 115
techniques 115
use of 114
Noninvasive ventilator bilevel positive airway pressure 222
Obesity 20
Open chest wound 72
Optiflow system 64
Oral hygiene 186
Oxygen 21
blender 64
chart 71, 72f
inspiratory 226
consumption, reduce 3
delivery, accurate 70
flow meter 66
homeostasis 127
in inspired gas 23
index 203
mixer loss 225
partial pressure of 2, 203
Oxygenated hemoglobin 123
Beer-Lambert law of 123
Oxygenation 2, 10, 43, 91, 93, 102, 111, 131
inadequate 3, 10, 11, 23
Paradoxical fall 134, 136f
Paralysis 173, 180, 181
Partial pressure support 80
Patent ductus arteriosus 56, 189
Peak airway pressure 39, 78
Peak inspiratory flow 230
Peak inspiratory pressure 4, 4f, 10, 23, 48, 49, 61, 80, 82, 101, 147f, 189, 219, 221, 226
Pediatric Academic Societies 191
and neonatal close suction catheters 179f
critical care 122
intensive care unit 3, 31, 64, 119, 122, 207f, 220
respiratory care system 64
Pendelluft effect 90
Pendulum shift 90f
Peripheral venous access 118
Peritoneal cavity 134
Permanent neurological disorders 24
Persistent hypoxia despite supplemental oxygen 118
Persistent pulmonary hypertension 35, 81, 82, 93
of newborn 198, 233
Pharynx 2
Pierre Robin syndrome 117
Pigments 124
Plateau pressure 19, 151
Pneumomediastinum 38
Pneumonia 1, 35, 48, 67, 116, 117, 122
bilateral 119f
health care-associated 183
hospital-acquired 183
inhalation 203
nosocomial 183
severe necrotizing 118f
types 183
ventilator associated 119, 183, 184
Pneumonitis, chemical 52
Pneumothorax 11, 36, 38, 72, 87, 93, 177, 179, 181
Poisonings 204
Poliomyelitis 117
Polymethylpentene oxygenator, low-resistance 200
Pores of Kohn 22
Positive airway pressure
biphasic 98, 103f
constant 225
expiratory 116
inspiratory 116
neonatal continuous 56
Positive end-expiratory pressure 2, 4, 4f, 19, 22, 35, 39, 40, 49, 56, 58, 61, 79, 80, 82, 100, 114, 146, 147f, 170f, 186, 190, 194, 219
effects of 44
use of 40
Positive pressure ventilation 40
high-frequency 90
ventilation, continuous 102
Postcardiac arrest 204
Post-extracorporeal membrane oxygenation care 207
Postextubation 61
respiratory failure 117
areas around nares 72
augmentation 99
control 80, 227
mode 148, 218, 227
ventilation 98, 99, 149f, 224
controlled intermittent mandatory ventilation 103f
expiratory 116
generating device 57
inspiratory 116, 230
level 228
limited time cycled ventilation 48
pulmonary 52, 53
regulated volume control 35, 98, 99, 108, 223
sensitivity 230
support 7, 190, 227, 230
ventilation 77, 79, 80, 105, 152, 167f, 190, 216, 218, 225
targeted ventilation 159, 159f
time scalar 152f, 157f, 168f
ventilators 220, 221
volume curve 84f
volume loop 39f, 84f, 85f, 156, 156f160f, 163f
displays 156
waveform 146, 146f
Pulmonary embolism 119f, 134
Pulse oximetry 82, 118, 122124, 131
conventional 125
Pulsus paradoxus 38
Pump failure 25
Puritan Bennett 840
neonatal ventilator 230
pediatric-adult ventilator 230
universal ventilator 230
ventilator 229, 229f, 230
Pyomyositis 119f
Raised intracranial tension 2, 30
Raised peak airway pressure 144
Rapid eye movement 56
Rapid sequence intubation 31, 33fc
Rapid shallow breathing index 194
curves 226
pulmonary graphics 144, 171
Respiration 1
accessory muscles of 122
Respiratory arrest 3, 38
Respiratory care 177
and pulmonary toilet 173, 174
protocol 12
Respiratory distress 31, 32fc, 48, 57, 67, 86, 119f
progressive 118
severity of 82t
syndrome 48, 49, 61, 82, 84, 92, 117, 199, 233
Respiratory extracorporeal membrane oxygenation 202
indication 202
selection criteria 203
Respiratory failure 3, 23, 31, 32fc, 34fc, 68
acute hypoxic 47
chronic 24
Respiratory frequency 218
Respiratory indices, monitoring of 122
Respiratory monitoring 122, 130
Respiratory muscle 25
failure, primary 25
weakness 166
Respiratory pump failure 25
Respiratory rate 73, 81, 82, 100, 126, 230
spontaneous 100
Respiratory sampling 183
Respiratory support 67
Respiratory system 19, 99
mechanics, basic 19
Respiratory therapists and technicians 233
Restrictive airway disease 117
cardiac 141
cardiopulmonary 126, 140, 204
Retinopathy of prematurity, development of 83
Routine tracheostomy management 177
Routine ventilator management protocol 12
Scalars 145
Scorpion sting 204
Sechrist ventilator 227, 227f
Sedation 173, 180, 207
level assessment 186
Seizures 134
Sensor technology, development of 144
Sensormedics 3100A 232, 232f
Sensormedics oscillator
controls of 234t
settings of 234t
Sepsis 12, 87
Shock 3, 24, 117
cardiogenic 204
Sickle chest 203
Sidestream devices 131
Sidestream systems 132
Siemens servo-I 227, 228f
Sildenafil 199
Silverman score 81
Skin and bowel care 174, 182
Skull fracture 72
SLE 5000 220
ventilator 234
apnea, obstructive 117
hypoventilation 46
Small air embolus 134
Smooth curved waves 136, 138f
Spinal cord
injury, acute 42
transection 24
Spinal muscular dystrophy 118f
Spontaneous breathing trial 14, 193, 194
Staphylococcal infection 119f
Status asthmaticus 47, 203
Steroids 37, 195
postnatal 191
Stress ulcer prophylaxis 186
Structured infection control protocols 180
Sweep gas flow 207
Synchronized intermittent mandatory ventilation 5f, 7, 77, 78f, 80, 99, 100, 148, 153, 154f, 189, 216, 219, 221, 224
Synchrony 8
Systemic venous circulation 40
Tachycardia 40, 195
Tachypnea 122
persistent 118
Target tidal volume 50, 100
Taylor dispersion 89f, 90
Tension pneumothorax 36
Terbutaline, intravenous 37
Test breath 104
Thal's procedure 181
Thoracic structures 16
Thoracostomy tube 36
Thromboelastogram 209
Tidal flow-volume 85
Tidal volume 5, 10, 85, 106, 218, 230
Total leukocyte count 184
Total lung capacity 17
Total respiratory
resistance 17
system 16
Trachea 2
Tracheal damage 95
Tracheal tube
cuff pressure 186
obstructed 134
Tracheobronchial aspiration 183
Tracheobronchomalacia 1
Tracheostomy 47, 106, 177
care 177
pediatric 177
Transairway pressure 151
Transcutaneous oxygen 123
Transport 231
care 231f
Trauma 68
Trigger asynchrony 163, 164
Tromethamine 208
displacement 87
obstruction 87, 123
Upper airway 1
obstruction 117, 191
occlusion, reduces 57
surgery 117
Upper gastrointestinal bleeding 117
Upper inflection point 27, 156
Urinary tract infections, catheter-associated 180
Vasoconstriction, pulmonary 11
Vasodilators, selective pulmonary 199
Vasopressors 52
Vena cava, inferior 205
Ventilation 2, 92, 131, 207
fundamentals of 8
mechanics of 2
classification of modes of 99fc
common modes of 152
continuous mandatory 100, 216
conventional 36, 77, 225
high-frequency oscillatory 90, 91, 93, 96, 98, 110, 111f, 112t, 190, 199, 232
inadequate 3, 10, 23
index 203
intermittent mandatory 7, 61, 190, 216, 219
modes of 6, 108t, 189, 218, 224
neonatal patient-triggered 76
newer modes of 98
parameters determine oscillatory 91
plus option spontaneous breath types 230
postoperative 4, 48
pressure support mode of 160, 160f
prolonged 36
proportional assist 98, 105
limited 9
support 99, 104, 104f, 108
targeted 157, 158, 158f
Ventilator 20, 215, 222
circuit, role of 184
continuous positive airway pressure 58
delivered breath 19
delivered intermittent mechanical breath 7
design 20
principles 19
functional characteristics of 20
graphics 144, 145
classification of 145
management 42, 207, 208
rate 14
synchronizes intermittent mandatory ventilation 7
technical specifications of 216
Ventilatory rate 5
Ventilatory support, strategies of 38
Venturi mask 64
Volume assured pressure support 99, 106, 107f, 108
Volume control ventilation 99, 150f, 157f, 224
Volume guarantee
pressure support 225
ventilation 225
Volume time scalar 162f, 163f
Volume waveform 148, 148f
Volutrauma 11, 36
Vomiting 118
Waveforms 145, 219
methodology 13
protocols 186
strategies 188
techniques of 194
therapy 67
Wheezes 122
Chapter Notes

Save Clear

Basics of Mechanical VentilationChapter 1

Praveen Khilnani
Basic principles of physics and gas flow apply to all age groups; anatomical and physiological differences play a significant role in selecting the type of ventilator as well as the ventilator modes and settings.
Upper airway in children is cephalad, funnel shaped with narrowest area being subglottic (at the level of cricoid ring), as compared to adults where the upper airway is tubular with narrowest part at the vocal cords. Airway resistance increases inversely by 4th power of radius i.e. in an already small airway even one mm of edema or secretions will increase the airway resistance and turbulent flow markedly necessitating treatment of airway edema, suctioning of secretion, measures to control secretions. Low functional residual capacity (FRC: Volume of air in the lungs at end of expiration) reduces the oxygen reserve, and reduces the time that apnea can be allowed in a child.
Respirations are shallow and rapid due to predominant diaphragmatic breathing, and inadequate chest expansion due to inadequate costovertebral bucket handle movement in children. Therefore, a child tends to get tachypnea rather than increasing the depth of respiration in response to hypoxemia. Oxygen consumption/kg body weight is higher; therefore, tolerance to hypoxemia is lower.
Susceptibility to bradycardia in response to hypoxemia is also higher due to high vagal tone. Pores of Kohn and channels of Lambert (bronchoalveolar and intermalleolar collaterals) are inadequately developed, making regional atelectasis more frequent. Closing volumes are lower and airway collapse due to inadequate strength of the cartilage in the airways is common, making a child particularly susceptible to laryngomalacia, and tracheo-bronchomalacia as well as lower airways closure at a higher lung volume.
Therefore, children tend to require smaller tidal volumes, faster respiratory rates, and adequate size endotracheal tubes and adequately suctioned clear airways for proper management of mechanical ventilation. Other important factors for choosing ventilatory settings include the primary pathology i.e. asthma, acute respiratory distress syndrome (ARDS), pneumonia, air leak 2syndrome, raised intracranial tension, neuromuscular weakness, neonatal hyaline membrane disease, or neonatal persistent pulmonary hypertension (PPHN).
During spontaneous breathing, pleural pressure is negative. During inspiration active work is done to generate the gradient between the mouth and pleural space as the driving pressure for inspired gases to enter the alveolus, and this gradient is needed to overcome resistance and to maintain the alveolus open, by overcoming elastic recoil forces.
Therefore, a balance between elastic recoil of the chest wall and the lung determines lung volume at any given time. Expiration is passive. During positive pressure ventilation, pressure gradient generated by the ventilator at the mouth (or endotracheal tube) is higher than the pleural pressure which is also positive, however at the end of inspiration, expiration is again passive though it can be manipulated by application of positive pressure to prevent complete deflation at the end of expiration (PEEP: positive end expiratory pressure).
Two main issues are important physiologically during mechanical ventilation: ventilation and oxygenation.
Ventilation washes out carbon dioxide from alveoli keeping arterial PaCO2 between 35 mm of Hg and 45 mm of Hg. Increasing dead space increases the PaCO2.
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Alveolar MV = Respiratory rate × Effective tidal volume
Effective TV = TV - Dead space
Dead space = Anatomic (nose, pharynx, trachea, bronchi) + Physiologic (alveoli that are ventilated but not perfused)
Adequate minute ventilation is essential to keep PaCO2 within normal limits.
Partial pressure of oxygen in alveolus (PaO2) is the driving pressure for gas exchange across the alveolar-capillary barrier determining oxygenation.
PaO2 = [(Atmospheric pressure - Water vapor) × FiO2] - PaCO2/RQ
RQ = Respiratory quotient
Adequate perfusion to alveoli that are well ventilated improves oxygenation.
Hemoglobin is fully saturated 1/3 of the way through the capillary.3
Hypoxemia can occur due to:
  • Hypoventilation
  • V/Q mismatch (V—ventilation, Q—perfusion)
  • Shunt (Perfusion of an unventilated alveolus, atelectasis, fluid in the alveolus)
  • Diffusion impairments.
Hypercarbia can occur due to:
  • Hypoventilation
  • V/Q mismatch
  • Dead space ventilation.
Gas Exchange
Hypoventilation and V/Q mismatch are the most common causes of abnormal gas exchange in the pediatric intensive care unit (PICU).
Hypoventilation can be corrected by increasing minute ventilation.
V/Q mismatch can be corrected by increasing the amount of lung that is ventilated or by improving perfusion to those areas that are ventilated.
Concept of Time Constant
Time constant is the time required to fill an alveolar space (or empty it). It depends on the resistance and compliance. In the pediatric age group one time constant that fills an alveolar unit to 63% of its capacity is 0.15 seconds. It takes three time constants to achieve greater than 90% capacity of the alveolar unit filled.
Time constant = Resistance (pressure × time/volume) × Compliance (volume/pressure)
This signifies that a certain minimum inspiratory time (Ti) is required to fill the alveoli adequately which is generally two to three time constants; i.e. 0.3–0.45 seconds. This is important when selecting the Ti on the conventional ventilator.
Indications remain essentially clinical and may not be always substantiated by objective parameters such as blood gas analysis.
Common indications include:
  • Respiratory failure:
    • Apnea/respiratory arrest
    • Inadequate ventilation
    • Inadequate oxygenation
    • Chronic respiratory insufficiency with failure to thrive
  • Cardiac insufficiency/shock:
    • Eliminate work of breathing
    • Reduce oxygen consumption4
  • Neurologic dysfunction:
    • Central hypoventilation/frequent apnea
    • Patient comatose, Glasgow Coma Score (GCS) <8
    • Inability to protect airway
  • Postoperative ventilation
  • Airway pressures:
    • Peak inspiratory pressure (PIP)
    • Positive end expiratory pressure (PEEP)
      zoom view
      Fig. 1: Graph showing continuous positive airway pressure (CPAP).
      zoom view
      Fig. 2: Graph showing factors affecting mean airway pressure (and oxygenation). 1. Inspiratory time, 2. Peak inspiratory pressure, 3. Expiratory time, 4. Positive end expiratory pressure, and 5. Pause time.
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      Fig. 3: Synchronized intermittent mandatory ventilation with volume control (SIMV-VC).
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      Fig. 4: Synchronized intermittent mandatory ventilation with pressure control (SIMV-PC).
    • Pressure above peep (PAP or δp)
    • Mean airway pressure (MAP)
    • Continuous positive airway pressure (CPAP)
    • Inspiratory time (Ti)
    • I:E ratio: Ratio of Ti and expiratory time in seconds
  • Frequency (f): Ventilatory rate (breaths/min)
  • Tidal volume (Vt): Amount of gas delivered with each breath
  • Expired tidal volume (Ve): Amount of gas measured by the machine at expiration.
  • Expired Minute volume (MV): Volume of gas in L expired per minute.6
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Fig. 5: Patient-triggered, pressure-limited, flow-cycled ventilation.
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Fig. 6: Time-triggered, pressure-limited, time-cycled ventilation.
Control Modes
In this mode, every breath is fully supported by the ventilator. In classic control modes, patients were unable to breathe except at the controlled set rate. In a conventional controlled mode, weaning is not possible by decreasing rate, the patient may hyperventilate if agitated leading to patient/ventilator asynchrony. Patients on control modes will need sedation and or paralysis with a muscle relaxant in newer control modes, machines may act in assist-control, with a minimum set rate and all triggered breaths above that rate are also fully supported.7
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Fig. 7: Time-triggered, volume-limited, time-cycled ventilation. (CL: compliance lung; Raw: airway resistance; VT: volume tidal)
Intermittent Mandatory Ventilation Modes
In this mode breaths “above” the set rate are not supported. Most modern ventilators have synchronized intermittent mandatory ventilation (SIMV).
Synchronized Intermittent Mandatory Ventilation
Ventilator synchronizes intermittent mandatory ventilation (IMV) “breath” with patient's effort.
Patient takes “own” breaths in between (with or without pressure support) the set SIMV rate. There is a potential for increased work of breathing and patient/ventilator asynchrony, if the ventilator interferes with the patient's effort to breath or if there is insufficient flow for the spontaneous breaths. Ventilators would have an inbuilt latent period of about 25% of the Ti in which to recognize the patient's effort in order to synchronize the mandatory breath in order to reduce asynchrony. SIMV breath can be pressure limited or volume limited.
Support Mode
Pressure Support
Ventilator supplies pressure support (flow) at a preset level but rate is determined by the patient, expiration begins passively when inspiratory flow decreases below a certain level preset in the ventilator (flow cycled). Volume support is also available in Servo 300 ventilators following the principle 8of pressure support (delivery of the set volume over the patient's natural inspiratory time duration keeping the pressure to a minimum.
Pressure support can decrease work of breathing by providing flow during inspiration for patient triggered breaths. It can be given with spontaneous breaths in IMV modes or as stand-alone mode without set rate as well as for weaning to retrain coordination of respiratory muscles in patients on ventilation for longer than few weeks.
Trigger is defined as the variable that initiates the breath from the ventilator. The trigger variable is usually pressure or flow.
Pressure trigger: With pressure triggering, in order to trigger the ventilator and initiate the inspiratory flow, the patient must decrease the pressure in the ventilator circuit to a preset value, which will then open a demand valve.
Flow trigger: With flow triggering, the patient triggers the ventilator when the respiratory muscles generate a certain preset inspiratory flow. It is generally believed that triggering of the ventilator is better with flow than with pressure.
The real clinical significance is unclear in terms of the work of breathing and patient ventilator interaction. Pressure sensors in current ventilators are much improved, reducing any difference between flow and pressure triggering systems. Recent studies in patients with different diseases show that the difference in the work of breathing between flow and pressure triggering is of minimal clinical significance.
Trigger setting: A pressure trigger setting of greater than 0 (cm of water) makes it too sensitive (meaning the triggered breath from the ventilator will be too frequent). A negative setting (negative1 or negative 2) setting is usually acceptable. Too negative setting will increase the work of the patient (to generate a negative pressure) to trigger a ventilator breath.
Ventilators deliver gas to the lungs using positive pressure at a certain rate. The amount of gas delivered can be limited by time, pressure or volume. The duration can be cycled by time, pressure or flow. If volume is set, pressure varies; if pressure is set, volume varies according to the compliance.
Compliance = Δvolume/Δ pressure
Chest must rise, no matter which mode is chosen.
Following are three main expectations from the ventilator:
  1. Ventilator must recognize patient's respiratory efforts (trigger)
  2. Ventilator must be able to meet patient's demands (response)
  3. Ventilator must not interfere with patient's efforts (synchrony)
Whenever a breath is supported by the ventilator, regardless of the mode, the limit of the support is determined by a preset pressure or volume.9
Volume limited: Preset tidal volume
Pressure limited: Preset PIP
Pressure versus Volume Control
Goal is to ventilate and oxygenate adequately. Both pressure and volume control modes can achieve it. Important requirements include adequate movement of the chest, smooth gas flow, and minimal barotrauma or volutrauma.
One must have a setup of high/low pressure alarms in volume cycling and, low expired tidal volume alarm when using pressure cycling.
Pressure-limited Ventilation
Ventilator stops the inspiratory cycle when set PIP is achieved.
Caution: Tidal volume changes suddenly as patient's compliance changes. Ventilator delivers a decelerating flow pattern (lower PIP for same Vt). This can lead to hypoventilation or overexpansion of the lung. If endotracheal tube is obstructed acutely, delivered tidal volume will decrease. This mode is useful if there is a leak around the endotracheal tube.
For improving oxygenation, one needs to control FiO2 and MAP, (I-time, PIP, PEEP) and to influence ventilation, one needs to control PIP and respiratory rate.
Volume-limited Ventilation
Ventilator stops the inspiratory cycle when set tidal volume has been delivered. One can control minute ventilation by changing the tidal volume and rate. For improving oxygenation primarily FiO2, PEEP, I-time can be manipulated. Increasing tidal volume will also increase the PIP, hence affecting the oxygenation by increasing the MAP. It delivers volume in a square wave flow pattern. Square wave (constant) flow pattern results in higher PIP for same tidal volume as compared to pressure modes.
Caution: There is no limit per se on PIP (so ventilator alarm will have to be set for an upper pressure limit to avoid barotrauma). Volume is lost if there is a circuit leak or significant leak around the endotracheal tube, therefore an expired tidal volume needs to be monitored and set. Some ventilators will alarm automatically if the difference between set inspired tidal volume and expired tidal volume is significant (varies between the ventilators).
Initial Ventilator Settings
One should always have the general idea regarding what initial ventilator settings to choose when initiating the ventilation.
Choose the mode: Control every breath (assist control) if planned for heavy sedation and muscle relaxation or use SIMV when patient likely to breath spontaneously.10
General parameters to choose will include:
Rate: Start with a rate that is somewhat normal; i.e. 15 for adolescent/child, 20–30 for infant/small child, 30–40 for a neonate, 40–50 for a premature neonate.
FiO2: 1(100%) and quickly wean down to level <0.5. Depending upon oxygen requirement 0.5 may be a starting point for the FiO2.
PEEP: 3–5 cm of H2O (higher to 6–7 if ARDS, or low compliance disease, lower (2–3 cm) if asthma, or high compliance disease.
Inspiratory time (I-time or I:E ratio): 0.3–0.4 sec for neonates, 0.5–0.6 sec for children, 0.7–0.9 in older children. Normal I:E ratio = 1:2–1:3
Then specifically choose if the modality of delivered breath will be pressure controlled or volume controlled (correct term is pressure limited or volume limited).
Pressure limited: Peak inspiratory pressure is set depending upon lung compliance and pathology
Neonates: Apnea 12–14 cm, hyaline membrane disease 18–22 cm H2O
Children: For normal lung 16–18 cm, for low compliance 18–25 cm H2O, severe ARDS 25–35 cm may be required.
Volume Limited
Tidal volume 8–10 mL/kg with a goal to get 6–8 mL/kg expired tidal volume. Initial tidal volume at 10–12 mL/kg may need to be set if leak is present around endotracheal tube; in such patients, pressure limited ventilation may be preferred. Flow in most ventilators is set at 6–10 L for the washout of the CO2 from the internal ventilator circuit, tubing's, etc. Flow less than 4 L/min is not recommended. Following discussion includes cases and principles of ventilation based on disease specific pathophysiology.
Adjustments after Initiation: Usually based on blood gases and oxygen saturations
For oxygenation: FiO2, PEEP, I Time, PIP (tidal volume) can be adjusted (increase MAP)
For ventilation: Respiratory rate, tidal volume (in volume limited) and PIP (in pressure limited mode) can be adjusted.
Positive end expiratory pressure is used to help prevent alveolar collapse at end inspiration; it can also be used to recruit collapsed lung spaces or to stent open floppy airways.
Gas Exchange-related Problems
  • Inadequate oxygenation (hypoxemia)
  • Inadequate ventilation (hypercarbia)11
Inadequate oxygenation: Important guidelines
  • Do not just increase FiO2
  • Increase tidal volume if volume limited mode, PEEP, Ti.
  • Increase PIP/PEEP/ Ti if pressure limited mode
  • If O2 worse, get chest X-ray to rule out air leak (treat!)/If lung fields show worsening (increase PEEP further)
  • Do not forget other measures to improve oxygenation
    • Normalize cardiac output (if low output) by fluids and/inotropes
    • Maintain normal hemoglobin
    • Maintain normothermia
    • Deepen sedation/consider neuromuscular block
High PaCO2: Common reasons include hypoventilation, dead space ventilation (too high PEEP, decreased cardiac output, pulmonary vasoconstriction), increased CO2 production, hyperthermia, high carbohydrate diet, and shivering. Inadequate tidal volume delivery (hypoventilation) will occur with endotracheal tube block, malposition, kink, circuit leak, and ventilator malfunction.
Measures for normalizing high PaCO2 guidelines:
  • If volume limited: Increase tidal volume (Vt), increase frequency (rate) (f).
  • If asthma: Increase expiratory time, may need to decrease ratio to achieve an I:E ratio >1:3.
  • If pressure limited: Increase PIP, decrease PEEP, increase frequency (rate).
  • Decrease dead space (increase cardiac output, decrease PEEP, vasodilator)
  • Decrease CO2 production: Cool, increase sedation, decrease carbohydrate load.
  • Change endotracheal tube if blocked, kinked, malplaced or out, check proper placement.
  • Fix leaks in the circuit, endotracheal tube cuff, humidifier
Measures to reduce barotrauma and volutrauma: Following concepts are being increasingly followed in most PICUs.
  • Permissive hypercapnia: Higher PaCO2s are acceptable in exchange for limiting peak airway pressures: as long as pH>7.2.
  • Permissive hypoxemia: PaO2 of 55–65; SaO2 88–90% is acceptable in exchange for limiting FiO2 (<60) and PEEP, as long as there is no metabolic acidosis. Adequate oxygen content can be maintained by keeping hematocrit >30%.
Patient Ventilator Dyssynchrony
In coordination between the patient and the ventilator: Patient fights the ventilator! Common causes include, hypoventilation, hypoxemia, tube block/kink/malposition, bronchospasm, pneumothorax, silent aspiration, 12increased oxygen demand/increased CO2 production (in sepsis), and inadequate sedation.
If patient fighting the ventilator and desaturating: Immediate measures
D: displacement, O: obstruction, P: pneumothorax, E: equipment failure.
  • Check tube placement. When in doubt take the endotracheal tube out, start manual ventilation with 100% oxygen.
  • Examine the patient: Is the chest rising? Breath sounds present and equal? Changes in examination? Atelectasis, treat bronchospasm/tube block/malposition/pneumothorax? (Consider needle thoracentesis.)
  • Examine circulation: Shock? Sepsis?
  • Check arterial blood gas and chest X-ray for worsening lung condition, and for confirming pneumothorax.
  • Examine the ventilator, ventilator circuit/humidifier/gas source.
If no other reason for hypoxemia: Increase sedation/muscle relaxation, put back on ventilator.
Sedation and muscle relaxation during ventilation: Most patients can be managed by titration of sedation without muscle relaxation. Midazolam (0.1–0.2 mg/kg/hr) and vecuronium drip (0.1–0.2 mg/kg/hr) is most commonly used. Morphine or fentanyl drip can also be used if painful procedures are anticipated.
Do not use muscle relaxants without adequate sedation.
Routine ventilator management protocol: Following protocol is commonly followed:
  • Wean FiO2 for SpO2 above 93–94. In ARDS, 89–92 may be acceptable.
  • Arterial blood gas (ABG) one hour after intubation, then am pm schedule (12 hourly), and after major ventilator settings change, and 20 minutes after extubation
  • Pulse oximetry on all patients, end tidal carbon dioxide (EtCO2)/graphics monitoring, if available
  • Frequent clinical examination for respiratory rate, breath sounds, retractions, color
  • Chest X-ray every day/alternate day/as needed.
Respiratory care protocol
  • Position changes every 2 hourly → right chest tilt/left chest tilt/supine position and try to maintain 30° head up position.
  • Suction 4 hourly and as needed (in line suction to avoid derecruitment/loss of PEEP/desaturation if available)
  • Physiotherapy 8 hourly: Percussion, vibration, and postural drainage. NO physiotherapy if labile oxygenation such as ARDS, PPHN13
  • Nebulization: In line nebulization is preferred over manual bagging. Metered dose inhalers (MDIs) can also be used
  • Disposable circuit change, if visible soiling
  • Humidification/in line disposable humidifier
Ventilator care protocols, suctioning, physiotherapy, and positioning should all be under proper protocols for patient safety and to prevent adverse events such as unplanned intubation.
Weaning from Mechanical Ventilation
Process of weaning begins at the time of initiation of ventilation (i.e. minimal ventilatory settings to keep blood gases and clinical parameters within acceptable limits although these settings will be very high).
If such procedure is followed then ventilatory settings would be reduced once the primary pathology/condition that led to ventilation is improving.
How do we know if the condition is improving?
  • Improving general condition, fever, etc.
  • Decreasing FiO2 requirement
  • Improving breath sounds
  • Decreasing endotracheal secretions
  • Improving chest X-rays
  • Decreased chest tube drainage, bleeding/air bubbles(as the case may be)
  • Improved fluid and electrolyte status (no overload or dyselectrolytemia)
  • Improving hemodynamic status
  • Improving neurological status, muscle power, airway reflexes/control. Described weaning criteria such as maximal negative inspiratory force, vital capacity measurement are usually impractical. In pediatrics and neonatal age group, weaning criteria are generally clinical.
Weaning Methodology
There are no set protocols supported by any pediatric studies. Protocol followed at author's institution is as follows:
When FiO2 requirement is down to 0.4, improvement in secretions, and chest X rays, improving clinical condition, muscle relaxant drip is stopped and sedation can be slowly weaned. One should change control mode (or PRVC) to SIMV mode with pressure support. Pressure support can be set at 10–15 cm above PEEP so that the spontaneous breaths can be adequately supported. Trigger sensitivity should be 0 to negative one. Then slowly SIMV rate can be weaned, followed by weaning of pressure support while closely monitoring for signs of respiratory distress, restlessness, nasal flaring, accessory muscle use, tachypnea, desaturations, and hemodynamic instability such as tachycardia, hypertension or hypotension.
Following weaning guidelines can be followed:
  • Decrease FiO2 to keep SPO2 >94
  • Decrease the PEEP to 4–5 gradually by decrements of 1–2 cm H2O14
  • Decrease the SIMV rate to 5 (by 3–4 breath/min)
  • Decrease the PIP (to 20 cm H2O, by reducing 2 cm H2O each time/tidal volume, to no less than 5 mL/kg to prevent atelectasis (usually guided by blood gases).
  • Ventilator rate and PIP can be changed alternately. If at any point patient's oxygen requirement increases greater than 0.6, or spontaneous ventilation is fast or distressed with accessory muscle use (increased work of breathing), patient gets lethargic, hypercarbia on blood gas, weaning process should be paused and the support level increased. Patient may not be ready. Goal is to decrease what the ventilator does and see if the patient can make up the difference without desaturations/hypercarbia/significant tachypnea, and respiratory distress. (For example, if patient's SIMV was reduced from 20/min to 15/min and the patient's spontaneous rate is increased from 25 to 50, this patient may need more time on the ventilator).
  • Spontaneous breathing trials (SBT): A trial for 15–20 minutes may be conducted by connecting the patient to collapsible anesthesia bag (C circuit trial), if no distress, desaturation or excessive tachycardia, sweating or hypertension, consider as readiness of extubation. With or without weaning protocols, most pediatric patients can be extubated successfully. SBT and clinical indicators for extubation readiness may be used in difficult situations of extubation failure; however, none of the pediatric specific weaning protocols and guidelines are able to predict successful extubation.
Most patients can be weaned to SIMV of 5 and extubated, some will need pressure support 5–10 above PEEP with CPAP, while others may need CPAP 5 cm H2O before extubation, with or without SBT with T piece.
Clinical indicators of extubation readiness: Extubation can generally be performed when following criteria are met:
  • Control of airway reflexes, minimal secretions
  • Patient upper airway (air leak around tube?)
  • Good breath sounds
  • Minimal oxygen requirement <0.3 with SPO2 >94
  • Minimal rate 5/min
  • Minimal pressure support (5–10 above PEEP)
  • “Awake” patient
  • Remember shock and post resuscitation are important indications for ventilation, in addition to respiratory failure and neuromuscular disease.
  • Clinical monitoring of adequate chest rise and oxygen saturations is very important (regardless of mode volume, pressure or time cycled mode).15
  • If ventilator fails, turn FiO2 to 1 (100%) and take over hand bag tube ventilation: Follow DOPE protocol and correct accordingly.
  • If and when in doubt regarding endotracheal tube status, do not waste time: Remove endotracheal tube and try bag mask ventilation.
  • Low tidal volume is recommended to prevent lung trauma (permissive hypercapnia and permissive hypoxemia).
  • Ventilator care protocols, suctioning, physiotherapy, and positioning should all be under proper protocols for patient safety and to prevent adverse events such as unplanned intubation.
  • With or without weaning protocols, most pediatric patients can be extubated successfully.
  • Spontaneous breathing trial and clinical indicators for extubation readiness may be used in difficult situations of extubation failure; however, none of the pediatric specific weaning protocols and guidelines are able to predict successful extubation.
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