Acute Respiratory Failure and
Basic Ventilator ManagementHeather A. Wallace, MSc., MPAS. PA-C
LT, MSC, USN
Describe anatomy and physiology of the respiratory system
Identify causes of acute respiratory failure
Identify acute respiratory distress syndrome (ARDS)
Describe strategies for the treatment of acute respiratory distress syndrome (ARDS)
List some adjunct rescue modalities for severe refractory hypoxemia
Evaluate an arterial blood gas
Identify initial approach to mechanical ventilation
44 yo F
PMH: HTN, DM2, PCOS
CC: sore throat, fever, cough x 3 days, and SOB x 2 days
Presentation: Peripheral cyanosis, tachypneic
VS: 101.1F, 90/60, HR 125, RR 42, Sat 54%
(+) for Influenza A
44 yo F, + Flu A PCR
You now decide to:
1. Write rx for Tamiflu, antipyretic, and analgesic
2. Order a CBC, Chemistry panel, UA
3. Write her a sick note for 3 days
4. Order a CXR
Controller(CNS)
Wiring (PNS)Bellows
(Thoracic cavity)
Airway Lungs/Alveoli
One way of viewing respiratory physiology is by function and structural components
Intrapulmonary airways3
Lungs/Alveoli
44 yo F
PMH: HTN, DM2, PCOS
CC: sore throat, fever, cough x 3 days, and SOB x 2 days
Presentation: Peripheral cyanosis, tachypneic
VS: 101.1F, 90/60, HR 125, RR 42, O2Sat 54%
(+) for Influenza A
44 yo F, + Flu A PCR
You now decide to:
1. Obtain a CT of her chest
2. Give her a fluid bolus
3. Plan for RSI and mechanical ventilation
4. Start high flow nasal cannula
Diffuse alveolar flooding
Increased right-to-left shunt across the lungs (more alveoli
with V/Q =0)
Decrease in PaO2Resistance to O2 therapy
Hypoxemic respiratory failure
Increased V/Q mismatch (more alveoli with V/Q << 1)
Lungs/Alveoli
44 yo F, + Flu A PCR
You now decide to:
1. Obtain a CT of her chest
2. Give her a fluid bolus
3. Plan for RSI and mechanical ventilation
4. Start high flow nasal cannula
44 yo F, + Flu A PCR (PBW=60kg)
You set her initial vent settings to:
1.AC mode, RR 20, Vt=520cc, FIO2 100%, PEEP 5cm H2O
2. AC mode, RR 12, Vt=360cc, FIO2 100%, PEEP 12cm H2O
3. Pressure Support mode, RR 20, Vt=520cc, FIO2 100%, PEEP 5cm H2O
4. Pressure Support mode, RR 12, Vt=360cc, FIO2 100%, PEEP 12cm H2O
Mechanical ventilator breathsVolume (flow controlled or time cycled)Pressure control (pressure controlled, time cycled)Pressure support (pressure controlled, flow cycled)
Forces during Inspiration and Expiration 3Pressure-Time Curve During Volume Control Ventilation 18,
Characteristic pressure-flow waveforms for spontaneous breathing and ventilated breaths 4,
Modes - combination of breaths to create ventilation strategy
Continuous mandatory ventilation (CMV)
With all volume or all pressure controlled breaths
Assist control ventilationWith all volume or all pressure controlled breaths
Stand-alone pressure support ventilation (PSV)Synchronized intermittent mandatory ventilation (SIMV)
Volume or pressure control basal or back up breaths synchronized to patient effort plus humidified gas for additional spontaneous breathing
Overview of Selected Modes of Ventilation4
SettingsTidal volume (VT) Respiratory rate (RR) Positive end-expiratory pressure (PEEP)Fraction of inspired oxygen (FiO2)Flow rate
Understanding lung protection17
ARDSNet Mechanical Ventilation Protocol 12
44 yo F with ARDS, + Flu A PCR (PBW=60kg)
You set her initial vent settings to:
1.AC mode, RR 20, Vt=520cc, FIO2 100%, PEEP 5cm H2O
2. AC mode, RR 12, Vt=360cc, FIO2 100%, PEEP 12cm H2O
3. Pressure Support mode, RR 20, Vt=520cc, FIO2 100%, PEEP 5cm H2O
4. Pressure Support mode, RR 12, Vt=360cc, FIO2 100%, PEEP 12cm H2O
Uncompensated Acid-Base
DisturbancespH PCO2 (mmHg) HCO3- (mEq/L) Common Cause
None (normal value)
Respiratory acidosis
Respiratory alkalosis
Metabolic acidosis
Metabolic alkalosis
44 yo F, + Flu A PCR
Intubated and mechanical ventilation initiated
CXR demonstrated b/l alveolar infiltrates
IBW 60kg
6 hours later:
VS: 99F, 120/75, HR 105, RR 30, Sat 92%
On AC 18 breaths per min
FIO2 80%, PEEP 12cm H2O
Vt = 360cc
Ppeak = 35, Pplat =32cm H2O
ABG = 7.37 /38 /64 /92%
Timing - Acute. Within 72 hours of a recognized risk factor or within 7 days.
Chest imaging - Bilateral opacities consistent with pulmonary edema are seen of chest radiograph or chest CT scan.
Origin of pulmonary edema - Respiratory failure not fully explained by cardiac failures or volume overload.
Hypoxemia
Mild ARDS: 200 < PaO2/FIO2 </= 300 with PEEP or CPAP >/= 5cmH2O
Moderate ARDS: 100 < PaO2/FIO2 < /= 200 with PEEP or CPAP > /= 5cmH2O
Severe ARDS: PaO2/FIO2 < /= 100 with PEEP 5cmH2O
Risk Factors: Sepsis, SIRS, shock, Trauma, acid aspiration, near-drowning, multiple emergency blood product transfusions, pancreatitis, DIC, burn
44 yo F, + Flu A PCR
Intubated and mechanical ventilation initiated
CXR demonstrated b/l alveolar infiltrates
IBW 60kg
6 hours later:
VS: 99F, 120/75, HR 105, RR 30, Sat 92%
On AC 18 breaths per min
FIO2 80%, PEEP 12cm H2O
Vt = 360cc
Ppeak = 35, Pplat =32cm H2O
ABG = 7.37 /38 /64 /92%
ABGs
Oxygenation
FiO2
PEEP
Ventilation
RR
44 yo F with ARDS, + Flu A PCR
You now decide to:
1. Decrease Vt to 300cc
2. Increase PEEP to 15cm H2O
3. Add Inhaled NO
4. Initiate prone ventilation
44 yo F with ARDS, + Flu A PCR
The best evidence now suggests you:
1. Administer cis-atracurium
2. Institute ECMO
3. Start HFOV (high frequency oscillatory ventilation
4. Prone position the patient
Prone Position Ventilation
Neuromuscular Blockade (NMB)
High Frequency Oscillatory Ventilation (HFOV)
Extracorporeal membrane oxygenation
Inhaled Nitric Oxide (iNO)
44 yo F with ARDS, + Flu A PCR
The best evidence now suggests you:
1. Administer cis-atracurium
2. Institute ECMO
3. Start HFOV (high frequency oscillatory ventilation
4. Prone position the patient
44 yo F with ARDS, + Flu A PCR
Intubated and mechanical ventilation initiated
CXR demonstrated b/l alveolar infiltrates
IBW 60kg
10 hours later:
She is still on the vent. Failing to wean. Has proximal myopathy w/ strength 2-3/5 in most muscle groups.
Failed 40% 5/5 SBT two days in a row after 25 minutes. RR 30
FIO2 40%, PEEP 5 cm H2O
Vt = 200cc
RSBI =115
44 yo F with ARDS, + Flu A PCR
You know decide to:
1. Continue to optimize medical management and attempt SBT daily in advance of liberation
2. Proceed with a tracheostomy and daily face mask trials
3. Proceed with a tracheostomy and PSV/CPAP 5/5 trials
4. Extubate to high flow nasal cannula
Awakening
Breathing
Coordination
Delirium
Early Mobility
Family Engagement
Classification of Acute Respiratory Failure 9
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15. Amato MBP, Meade MO, Slutsky AS, et al. Driving Pressure and Survival in the Acute Respiratory Distress Syndrome. N Engl J Med. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639
16. Villar J, Martín-Rodríguez C, Domínguez-Berrot AM, et al. A Quantile Analysis of Plateau and Driving Pressures: Effects on Mortality in Patients With Acute Respiratory Distress Syndrome Receiving Lung-Protective Ventilation*. Crit Care Med. 2017;45(5):843. doi:10.1097/CCM.0000000000002330
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Thank you
–Johnny Appleseed
“Type a quote here”
I have no financial interests to disclose with regard to this subject or the contents of the presentation.
Decrease in respiratory drive from CNS
Decrease in respiratory rate and tidal volume
Decrease in minute ventilation
Decrease in alveolar ventilation Loss of normal response to elevated PaCO2
PaCO2 increases pH and PaO2 decrease
Controller(CNS)
Decrease in respiratory muscle strength
Decrease in respiratory rate and tidal volume
Decrease in minute ventilation and alveolar ventilation
Loss of spontaneous sigh
Inactivation of surfactantUnstable alveoli
PaCO2 increases
pH and PaO2 decrease
MicroatelectasisDecrease in compliance
Increased [PAO2 -PaO2]
Bellows(Thoracic
cavity)
Airway obstruction
Decreased FEV1
Decrease in maximal voluntary ventilation
Decrease in maximal sustainable ventilation
Decreased ventilatory capacity (20L/min)
HyperinflationFlattened diaphragms
Airway
Increased work of breathing
(VCO2)
Increased VD/VT
Hyperventilation (early phase of
asthma)
Example: VCO2 rises from 200mL/min to 300mL/min
Example: VD/VT increases from 0.3 to 0.6
Example: PaCO2 falls from 40mmHg to 30mmHg
Increased ventilatory demand(VE increases from 7.1 L/min to 25
L/min)
Which of the following interventions has been associated with improved mortality in clinical trials of patients with ARDS?
1.Ventilation with low tidal volumes (6ml/kg of predicted body weight)
2.Ventilation with high PEEP (>10cm H2O)
3.Ventilation with inspiratory-to-expiratory ratio (I:E ratio) greater than 2:1
4.High-frequency oscillatory ventilation (HFOV)
Which of the following patients is most likely to have a mortality benefit from ventilation in the prone position?
1.A 54-year-old female with severe cardiogenic pulmonary edema supported by mechanical ventilation requiring high FIO2
2.A 45-year-old male with multifocal pneumonia and ARDS supported by mechanical ventilation (FIO2 0.7, PEEP 10, PaO2/FIO2 90)
3.A 35-year-old female with ARDS post-aspiration pneumonia supported by mechanical ventilation (FIO2 1.0, PEEP 5, PaO2/FIO2 250)
4.A 76-year-old male with severe influenza and ARDS supported by mechanical ventilation (FIO2 0.8, PEEP 12, PaO2/FIO2 180)
6
12
3
54
9 10
78
1
87
910
65
2
34
Segments of the pulmonary lobes. RLL, Right lower lobe. 1. Named branches of the tracheobronchial tree, viewed from the front 2
Intrapulmonary airways and circulation 3
Control of respiration 4
Controller(CNS) Wiring (PNS)
Bellows(Thoracic
cavity)Airway Lungs/Alveoli
Functional and structural components of respiration
Neural Control of Respiration6
Controller(CNS)
Ventral respiratory group (VRG)- Nucleus ambiguous (CN XI,
X)- Botzinger complex- Pre-Botzinger complex
(pacemaker cells - opioid sensitive)
Dorsal respiratory group (DRG)- Solitary tract
nucleus (CN IX, X)
Pneumotaxic center(medial parabrachial nucleus, Kolliker-fuse nucleus)
Apneustic center (diffuse lower pontine nucleus)
Phrenic motor neuronsC3,C4,C5 “keep the diaphragm alive…”
ANTERIOR POSTERIOR
The Respiratory System and PNS 7
Wiring (PNS)
Bellows(Thoracic
cavity)
Forces during Inspiration and Expiration 3
Airways8
Airway
Intrapulmonary airways3
Lungs/Alveoli