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Younsuck Koh, MD, PhD, FCCM
Dept. of Pulmonary & CCM
Asan Medical Center,
Univ. of Ulsan College of Medicine
Seoul, Korea
Patient-Ventilator Asynchrony:
How to fix it
2 Systems
• Comfort
• Stable hemodynamics
• Less injury
Patient-Ventilator Synchrony
Outcome
Definition of Dyssynchrony
Analysis of Complaints
during MV after cardiac surgery
From Kunming Medical Univ.
Wang Y, et al. J Cardiothoracic Vasc Anesth 2015
Patient-Ventilator Asynchrony during assisted MV
15 of 62 pts (24%) had an asynchrony index > 10% of respiratory
effect
6
7.5
(3-20)*
25.5
(9.5-42.5)
0
5
10
15
20
25
30
< 10% > 10%
TVT
* interquartile
Thille AW, et al. Intensive Care Med 2006;32:1515-22
Outcome – A Significant Impact on the Duration of Mechanical Ventilation
8
Ventilator Asynchrony vs. Outcome
Blanch L, et al. Intensive Care Med 2015;41:633-642
Case 1
78/M with COPD
Home O2 with 1.5 L of Nasal Prongs
Transferred to ER due to respiratory difficulty with mental change
• ABGA:
7.322 - 101.6 - 23.9 –
19.2 - 51.4 - 34.2
• Hospital Course
1st Day: PCV with sedation
2nd Day: decreased VT and increased f with PSV trial using accessory respiratory muscles
During Stable With distress
12
Q1. How to approach?
Causes of Asynchrony
Patient-related causes
• resp. pump related
• complications; embolism..
• agitation
Ventilator-related causes
Time (sec)
Airway Pressure (cm H2O)
Asynchrony in each breath phase
-Triggering - Flow
demand
Time (sec)
Airway Pressure (cm H2O)
- Delayed expiration
- Auto-PEEP
16
Q2. What do you think first?
Auto-PEEP
elastic pressure remaining in alveoli at end-expiration
Physiologic Consequences of Hyperinflation
Respiratory
• increased work of breathing
• resp. pump efficiency
– Portion of diaphragm contacting with the inner surface of the ribcage (no lung in between)
– 55 % of total diaphragm surface at FRC
DH as a cause of Diaphragm Dysfunction: Zone of Apposition for Diaphragm Movement
Normal
COPD
Diaphragm dysfunction by Lung Hyperinflation in
COPD
FRC in normal
FRC in COPD
Mechanical disadvantages of flattened diaphragm:
• Length-tension relationship
• Laplace’s law (P = 2T/radius)
Comparison of work of breathing
(WOB) and pressure-time product
(PIP) between patients with (■)
and without (■) auto-PEEP
Comparison of expiratory airway
resistance (RAWe) and mean airway
resistance (RAWm) between patients
with (■) and without (■) auto-PEEP
JY Chin, et al. Tuberculosis and Respiratory Disease 1996: 43; 201
N = 20
Increased Work of Breathing:
Comparison of P0.1 between patients with (■) and
without (■) auto-PEEP JY Chin, et al. Tuberculosis and Respiratory Disease 1996: 43; 201
20 ARF patients
“Auto-PEEP may be associated with ineffective triggering.”
Hemodynamics
• hypotension
• misinterpretation of volume status
and pressures (CVP, BP)
Physiologic consequences of DPH
Case: COPD on MV: PC 20 cm H2O
BP 90/60 mm Hg
CO 2.6 L/min
PAOP 22 cmH2O
Auto-PEEP 12 cm H2O
Ventilator-off
BP 135/80 mm Hg
CO 4.4 L/min
PAOP 11 cm H2O
Pepe & Marini. 1982
27
Q3. How to detect Auto-PEEP?
Time (sec)
Airway Pressure (cm H2O)
Fig. 1. Flow and esophageal pressure waveforms showing dynamic auto-PEEP. Arrow
indicates the beginning of inspiratory effort. Dotted line shows the beginning of the
inspiratory flow after overcoming the auto-PEEP.
29
Q4. How to solve?
• MV resetting - VT -I:E -External PEEP
• Correct underlying causes - Bronchodilator/steroid - Anxiety control; sedation
Solutions
Ppl
Triggering
sensitivity
Insp flow
10
6
0
-2
cm H2O
Koh Y. Crit Care Clin 2007;23:169-81
Case: 71M, asthma on MV 8th day
with 8 cm H2O of auto-PEEP auto-PEEP
external PEEP, cm H2O
0 2 4 6 8 10
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Pp
ea
k, cm
H2
O
20
22
24
26
PaC
O2
, m
m H
g
60
65
70
75
VE
I, lit
er
Synchrony: Panic Cycle
ANXIETY
INCREASED VENTILATION
HYPERINFLATION
AUTO PEEP HEMODYNAMIC COMPROMISE
MUSCLE WEAKNESS
INCREASED WORK OF BREATHING
DISCOORDINATE BREATHING
Marini JJ. Ventilatory management in severe airflow obstruction. In: Acute
Respiratory Failure in Chronic Obstructive Pulmonary Disease.
Marcel Dekker, 1996:761.
M/85, COPD with RF
MV : PCV 13 cm H2O
FiO2 0.4
PEEP 5 cm H2O
f 14/min
Sedation : Midazolam 2 mg/h iv
+ morphine 4 mg iv
Sedatives
BP
&
PR
100
Under sedation
Case 2
Flow-Time Curve
After awakening
37
Q4. What is the difference?
P.-Time Wave
Flow-Time Wave
2 waves in Pressure 1 wave in Flow Not double triggering
P.-Time Wave
Flow-Time Wave
2 waves in Pressure 2 waves in Flow Double triggering
P.-Time Wave
Flow-Time Wave
Q5. How to correct #2 by #3?
3
#2 P.-Time Wave
Flow-Time Wave
#2 P.-Time Wave
Flow-Time Wave
By increasing pressure delivery in PCV mode
A B
Better Breath-Stacking Index Improvement through Ventilator Setting
Effective measures: Increase in insp. Time PSV
Changques G, et al. Crit Care Med 2013; 41:2177-87
Case 3
Breast ca. with lung metastasis. Sudden respiratory distress: Insp. VT 650 mL Exp. VT 39 mL F: 41 MV 1.4 L
44
Q6 What could be a cause of the distress?
Distress resolved after A-node insertion Cuff p. 25 mmHg
Observe airway: Suction injury
Case 4
Postop due to aortic aneurysm. Sudden respiratory pattern change to Deep & Rapid tidal breath at CPAP
48
Q7 What could be a cause of the change?
Initial With breath change
M/61 Pn. with ARDS Prone
positioning Weaning: Tachypnea
Case 5
51
Q8 What could be a cause of the tachypnea?
Ventilator synchrony is getting better after improved ileus.
M/75, pn with ARDS
On Ad. Weaning trial 16 cmH2O of PSV
Case 6: Respiratory Difficulty with mode change
54
Q9 What could be a cause of the distress?
Critical Illness Polyneuropathy
• Definition: acute generalized dysfunction of nerve axon
Bolton et al. J. Neurol Neurosurg Psychiatry 47: 1223-1231,1984
• A cause of unexplained difficult weaning from ventilator
• Occurred in 70% of MODS patients Witt NJ et al. Chest. 99: 176-184, 1991
Causes of Diaphragm Dysfunction in ICU
– Shock
– Sepsis
– Drugs: NM blockade, antibiotics (aminoglycosides, polymyxins, beta blockers, calcium channel blockades, diuretics, steroids)
– ICU-acquired weakness
– Dynamic hyperinflation
– Prolonged MV
MV D27
Rt diaphragm dysfunction Normal Lt diaphragm
PKP Rt.AVIPKP Lt.AVI
Case 7 F/35, ARDS with IRAB pn., Sudden Respiratory Distress
Colistin inhalation, VT 350-400 ml 120-150 ml
59
Q10. What could be a cause of the distress?
Filter clogging
• Initiation phase: clinical deterioration
• Maintenance phase: heavy sedation
• Weaning phase: weaning delay
Summary: Clinical Impact of Patient-Ventilator Asynchrony
Detection of Patient-Ventilator Asynchrony
• Observe patient synchrony with MV
• Detect accessory resp. m use
• Observe MV monitor: flow-time curve
Summary: how to approach
Disconnect MV with Pt
Airway patency
Ambu bagging: observe pt’s condition
Acute Clinical Deterioration
Suspect pneumothorax, PE…
Auto-PEEP, pain, CIP..
+ -
Careful Paralysis & Sedation