Effect of Ventilatory Variability on Occurrence of Central Apneas - PowerPoint Presentation

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Effect of Ventilatory Variability on Occurrence of Central ApneasRESPIRATORY CARE • MAY 2013 VOL 58 NO 5

Paul F. Nuccio, MS, RRT, FAARC

Brigham and Women’s Hospital

Boston, MA

BackgroundDefinitions:

PSV = Pressure Support Ventilation

NAVA =

Neurally

Adjusted Ventilatory Assist

Periodic breathing

What is the research question?

Is there a difference in the occurrence of central apnea episodes between patients ventilated with a constant-level PSV vs. NAVA?

Is this research question relevant?

Central apnea may be associated with significant

pathophysiologic

changes, including stroke, brainstem lesion, encephalitis, and congestive heart failure.

BackgroundWhat is known about this subject?

normal ventilation varies from breath to breath

traditional mechanical ventilation may be monotonous

close association between arousal from sleep and ventilatory effort

Background literature

Anesthesiology 2010;112(3):670-681.

NAVA resulted in more complexity of airflow and breathing pattern compared with PPV

Anesthesiology 2009;110(2):342-350.

Variability of pressure support improves lung function

Any concerns about COI?

None. Dr.

Delisle

has disclosed a relationship with Fisher &

Paykel

.

Methods

What is the study design?

Prospective, comparative, crossover study

Inclusion criteria

Invasive mechanical ventilation

Normal consciousness

Absence of sedatives and opiates for

>

24 hours

PSV with FiO2 <0.60 and PEEP of 5cmH2O (SpO2

>

90%)

Exclusion criteria

Presence of a central nervous system disorder

Glasgow Coma Scale score <11

Hemodynamic instability

Renal and/or hepatic insufficiency

Ongoing sepsis

History of esophageal

varices

or

gastroesophageal

bleeding (past 30 days)

History of GI symptoms such as vomiting

Methods

What is the control group?

With a crossover study, every patient serves as his or her own control.

Is the sample size appropriate?

There were a total of 14 patients in the study.

Very difficult to draw conclusions from such a small sample size.

What are the threats to validity of the design?

Small sample size

Compare apples to apples?

Was the statistical analysis appropriate?

Statistical software utilized for analysis

Comparisons made using general linear model for repeated measures

Wilcoxon

test for paired samples

Any ethical concerns?

The ethics committee of the hospital approved the study, and the subjects or their surrogates gave their informed consent.

Potential ethics concerns if one therapy appears to provide more benefit.

Study

Protocol

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Polysomnography

tracings with

neurally

adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) in a representative subject.

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

ResultsWhat are the main results? Study population

See table 1

Breathing pattern

See table 2

Apneas

See table 3

Variability of ventilation

See table 4

Table 1 - Subjects

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Table 2 - VT

, Breathing Frequency,

Apneas

per Hour, and PETCO2 While

Awake

and Asleep.

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Table 3 - Oscillatory

Behavior

of VT, Breathing Frequency, V̇E, and PETCO2 During Sleep Stages 2 and 3–4 During PSV in the 10 Patients With Central

Apneas

.

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Table 4 - VT

, f-flow, and

EAdi

Peak Variability in the 10 Patients With

Central

Apneas

.

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Fig 3 - Variability

during pressure support ventilation (PSV).

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

Fig 4 - Variability

during

neurally

adjusted ventilatory assist (NAVA).

Delisle

, S. et al.

Respir

Care 2013;58:745-753

(c) 2012 by

Daedalus

Enterprises, Inc.

DiscussionWhat do these finding mean?

Interesting & provocative study that lacks clear clinical outcomes benefit

How should these findings impact practice?

Unlikely to have a significant impact on practice

How do these findings relate to previous findings from other studies?

Similar to other studies

DiscussionWhat are the study limitations/concerns?

Single center study

Small sample size

Possible influence of sedation

Single level of both NAVA and PSV

Potential risk of using NG tubes

What additional work is needed in this area?

Study findings of physiological effect of NAVA must be confirmed by further clinical studies.

Editorial… by Kathy S Myers Moss MEd RRT-ACCS University of Missouri

“I commend the authors on their use of a prospective, randomized, controlled trial, the gold standard of experimental research methods. In addition, the research design integrated a crossover method with attention to minimizing residual effects. The statistically significant effect on tidal volume variation is especially noteworthy given the small sample size of 14.’’

“Until well designed studies provide evidence suggesting reduced morbidity, mortality, stay, number of ventilator days, or other desirable clinical outcomes, clinical managers are unlikely to invest in the required software and hardware upgrades necessary to implement NAVA.”

ConclusionsWhat are the authors’ conclusions?NAVA was associated with increased ventilatory variability compared to constant level PSV. With NAVA absence of

overassistance

during sleep coincided with absence of central apneas, suggesting that load capacity and/or

neuromechanical

coupling were improved by NAVA and that this improvement decreased or abolished central apneas.

How do you think this should affect practice?

Since NAVA is exclusively an option for one ventilator, widespread use of this technology will continue to be limited. More widespread adoption of this technology will require physiologic outcomes improvements, outcomes such as decreased number of ventilator days, and fewer complications of mechanical ventilation.

What is the take-home message?

Further clinical investigations are needed to evaluate the impact of NAVA on weaning time and patient outcomes.