Biomedical Engineering Reference
In-Depth Information
CHAPTER 13
MATHEMATICAL MODELLING OF NON-INVASIVE
PRESSURE SUPPORT VENTILATION: INVESTIGATION
OF TIDAL VOLUME INSTABILITY
Sahattaya Rattanamongkonkul
a
, Yongwimon Lenbury
b
John R. Hotchkiss
c
and Philip S. Crooke
d
a
Department of Mathematics, Burapha University, Chonburi, Thailand
b
Department of Mathematics, Mahidol University, Bangkok, Thailand
c
Department of Critical Care Medicine,
University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
d
Department of Mathematics, Vanderbilt University, TN, USA
A mathematical model for non-invasive pressure support ventilation
(NIPSV) is presented. The model consists of two dierential equations
describing the volume in a one-compartment lung. In this study, we used
the model to simulate spontaneously breathing patients with obstructive
lung disease undergoing pressure support ventilation at 22 cmH
2
O, and
PEEP of 5 cmH
2
O. NIPSV can give rise to unintended instability with
potential adverse eect. Tidal volume instability is dened as a situation
when the tidal volume, delivered over 100 consecutive breaths, creates
a coecient of variation higher than 10%, or a skipped breath occurs.
To explore the tidal volume instability, we investigated the variability of
tidal volume (V
T
) delivery during NIPSV under combinations of respi-
ratory resistance, R = 10, 15, 20 and 25 cmH
2
O/L/s, compliance, C =
0:06, 0:08, 0:10 and 0:12 L/cmH
2
O, and frequency, f = 14, 16, 18, 20,
and 22 breaths/min at inspiratory ow cut-o levels of 5% to 80%, and
pressure triggering levels of 1, 3, 5, 10 and 15 cmH
2
O. We discovered that
lower pressure sensitivity, higher lung compliance, higher ow resistance,
and higher breathing frequency increasing the likelihood of instability.
1. Introduction
Non-invasive pressure support ventilation (NIPSV) is an as-
sisted mode of ventilation that is increasingly used in clinical
medicine
20;16;27;28;18;25
. Recently, it has been utilized in the treatment of
respiratory failure as an alternative to endotracheal intubation. NIPSV pro-
vides a safe and eective way to improve alveolar ventilation and oxygena-
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