Patient-Ventilator Asynchrony in Non-invasive Ventilation and

Solution

Prof. Dr. Kürşat UzunSelçuk University, Meram Medical Faculty,

Pulmonary Diseases and Critical Care Department

Konya

Non-invasive ventilation

NIV

• Decrease work of breathing• Improve gas exchange• Relieve dyspnea• Reducing the intubation rate– AECOPD from 63% to 21%

• Shorten ICU stay• Decrease nosocomial infection• Decrease mortality – AECOPD from 25% to 9%

Eur Respir J 2008; 31: 874–886

• 40 %• Clinical status

– the selection of appropriate patients

– Acuity of illness– the first 1–2 h of NPPV

• Trained team• Interface

– poor mask tolerance, – skin lesions– leaks

• Acceptance• Compliance• Synchrony

NIV Failure/Success

5

NIV

ProblemPresence of leaks around the mask

Ventilator settingsInterfacesAgitation

Patient-ventilator asynchrony

Discomfort

Worsening the clinical situation

Patient-ventilator asynchrony

Patient’s

neural time

Ventilator

insufflation time

NIV

• Pressure support is the most frequently used ventilatory mode during NIV (80%)– Triggering of ventilator– Pressurization slope and

inspiratory flow– Pressure support level– Cycling

• Patient control– respiratory rate– duration of inspiration

Patient-ventilator asynchrony

• Transdiaphragmatic pressure (Pdi)

• Diaphragmatic electromyography

• Esophageal pressure• Flow-pressure

waveform– Wasted effort– Double triggering– Auto-cycled breaths

• Clinical– Tachypnea– Activation of inspiratory

neck muscles– Ineffective triggering

efforts– Forced expiration

Patient-ventilator asynchronyLeaks

Inspiration Expiration

Pres

sure

Phase 1Delayed triggeringIneffective effortAuto-triggering

Phase 2Decreased rate of inspiratory pressure rise

Phase 3Delayed cycling(prolonged inspiration)

Phase 4PEEP Loss

PEEP

TimeResp Care 2009;54(1): 85-96Am J Respir Crit Care Med 2001;163:1059-63

Cycling

• Inspiratory flow decreases to a predetermined fraction of peak inspiratory flow

(Expiratory trigger)• Increased WOB

– COPD

• Usually 25% of V’peak

InspirationCycling

expiration

Delayed cycling

• The presence of leaks– prolonged mechanical

inspiration – İnspiratory flow does not

reach the cycling-off criterion• Delayed cycling-off

Calderini et al. Intensive Care Med 1999; 25: 662–7

Delayed cycling

Critical Care 2006, 10:236

COPD

Prolonged inspirationSolve

• Reducing – the leaks

• Mask position

– Ventilator insufflation time• Limiting total inspiratory

pressure– Pressure support

level– PEEP level

• Increasing the expiratory trigger– 50 % or more

• Reducing the maximal inspiratory time– 0.8-1.2 second

Intensive Care Med 2004; 30:S65Clin Pulm Med 2007; 14:350-9Intensive Care Med 1999; 25: 662-7

Nava S et al. Breathe 2009;5 (4)

Delayed cyclingSolve

Higher value of ET decreases delayed cycling

Am J Respir Crit Care Med Vol 172. pp 1283–1289, 2005

Critical Care 2006, 10:236

Excessive tightness

• Patient discomfort• NIMV intolerance• High pressurisation rate

increases air leakage despite sufficient mask fitting

Autotriggering

• Expiratory leaks can generate a presure drop below the external PEEP level– Simulating the patient’s

effort• Triggering a ventilator breath

• Short cycle• Flow distortion

– Patient does not generate effort

– Fight the ventilatorNava S et al. Breathe 2009;5 (4)

Auto-triggeringSolve

• Decreasing triggering sensitivity– Careful adjustment of setting– Avoid ineffective triggering

Ineffective inspiratory triggering

• The inspiratory muscle contraction does not trigger the ventilator

• High level of support• When dynamic hyperinflation

(COPD)• PEEPi

• Filter

Nava S et al. Breathe 2009;5 (4)L.achour, Comput Biol Med. 2007 Sep;37(9):1308-20

Ineffective triggering

• Dynamic hyperinflation– Inspiratory threshold load– PEEPi has been shown to

lead ineffective efforts in COPD

• Leaks were shown to – increase the trigger delay

and– the number of ineffective

breaths

• Pressure support level

PS

IE

Respiratory rate and ineffective triggering

• Ineffective effort index– 48/h, night

• High levels of IPAP– VT

• PEEPi

• High RR• There was no difference

according to compliance levelCOPD, OHS, KS

They did not found any associations between a spesific ventilator

n: 48 patients

Double-triggering

• Insufficient level of pressure support

• Increased inspiratory demand

• Ventilator’s pressurization time is too short

Patient–ventilator asynchrony duringnon-invasive ventilation for acute respiratory

failure: a multicenter study Vignaux et al. Intensive Care Med 2009; 35:840--6

COPD 40%, Heart failure 28%, OHS 15%

3 hospital , n:60ICU ventilatorNIVEMGdiPressureFlow

Diaphragmatic EMG (EMGdi)

Synchrony n %

Auto-triggering 8 13

Double triggering 9 15

Ineffective breath 8 13

Premature cycling 7 12

Late cycling 14 23

Asynchrony 23%, Severe asynchrony 43%

Level of pressure supportThe magnitude of leaks

Intubation rateLenght of stay in ICUMortality, no difference

ICU ventilator was used

Interfaces

Mask and asynchrony

• improves gas exchange• Ineffective inspiratory

efforts• less efficient than the mask

in reducing inspiratory muscle effort and

• worsens patient–ventilator synchrony

Ventilator settings

Triggering

• Pressure• Flow

• Flow triggering– Reduce

• İnspiratory effort• Triggering delay (COPD)

Nava S et al. Thorax 1997;52:249-254

Most sensibleLess sensible

Suitable

Pressure support level

• Insufficient support leading to increased respiratory muscle load

• Excessive support– Dynamic hyperinflation– PEEPi– Increase in leaks and

decrease in delivered VT

Pressure support can be titrated on the VTE (8-10 ml/kg) and the patient’s respiratory rate, which should remain below <30/min

Pressurization and inspiratory flowRise time

• Increasing comfort• The incremental

increase in Paw per time unit

• COPD– Short rise time 0.05-0.1 – Steep slope is associated

with less WOB

• Neuromuscular– Slow rise time 0.3-0.4

Mode

Am J Respir Crit Care Med Vol 164. pp 1606–1611, 2001

NAVANeurally adjusted ventilator assisted

• Diaphragm electrical activity (EAdi)– Esophageal electrode (naso-gastric catheter)

• Assistance– Onset– End– Level

• Synchrony between neural and mechanical timing should be guaranteed at any phase of respiration

• Diaphragm unloading • Reduction in the patient’s effort• Ineffective effort • Experimental mode

Sinderby C, et al. Nat Med 1999;5:1433-6

Machine

Trigger delay (Td) Inspiratory trigger

Inspiratory:expiratory cyclingΔTi is the difference (tidiff) between the patient (tipat) and ventilator (tiassist) inspiratory durations

Flow Shape Signal

Digital Auto-Trak

Conclusion

• Appropriate – patient– Interfaces– Ventilator settings

• Monitorisation

Thank you