TY - BOOK
T1 - Collapsibility of the human upper airway: the influence of state, posture and instrumentation
AU - Maddison, Kathleen Jenni
PY - 2015/4
Y1 - 2015/4
N2 - [Truncated] Background. Obstructive sleep apnoea (OSA) is a common condition characterized by
recurrent partial or complete collapse of the upper airway (UA) during sleep.
Individual predisposition to OSA is quantified by measurement of UA collapsibility. The
pharyngeal critical pressure (the pressure at which the UA collapses, Pcrit) is a gold
standard measure of this. Pcrit is determined by manipulating applied pressure to
induce varying degrees of inspiratory flow-limitation. Ideally, inspiratory flowlimitation
is identified using measurement of oesophageal pressure (Pes), which
requires a transducer catheter to traverse the UA. However, it is possible that the
presence of such a catheter could alter the mechanical behaviour and collapsibility of
the UA. Apart from this technical issue, the Pcrit technique is inherently difficult to
perform during sleep as altering applied pressure often results in measurementinduced
arousals. This is not an issue during general anaesthesia, which provides ideal
conditions under which to study UA collapsibility as arousals are suppressed, muscle
activation is minimised and other known modifiers, such as head posture, can be
controlled while still maintaining spontaneous ventilation. Given these advantages,
there is a case for using anaesthesia to characterise an individual’s UA collapsibility.
However, it is important to know how such measures equate to those made during
sleep. To date this relationship has been inferred by relating easily obtained indirect
sleep measures of collapsibility (e.g. apnoea hypopnoea index, AHI) to anaesthesia
Pcrit measures. As yet no study has compared UA collapsibility during anaesthesia and
sleep using the same metric (i.e. Pcrit). Furthermore while the anaesthesia model has
been used to demonstrate the effect of head posture on UA collapsibility, the effect
during sleep has yet to be investigated.
Aims. The aims of the studies described in this thesis were to utilise two distinct states
of human consciousness, namely sleep and general anaesthesia, to examine: (i) the
effect of Pes monitoring on UA collapsibility; (ii) the mechanisms underlying the state
dependent differences in UA collapsibility; and (iii) the effect of head posture on UA
collapsibility.
AB - [Truncated] Background. Obstructive sleep apnoea (OSA) is a common condition characterized by
recurrent partial or complete collapse of the upper airway (UA) during sleep.
Individual predisposition to OSA is quantified by measurement of UA collapsibility. The
pharyngeal critical pressure (the pressure at which the UA collapses, Pcrit) is a gold
standard measure of this. Pcrit is determined by manipulating applied pressure to
induce varying degrees of inspiratory flow-limitation. Ideally, inspiratory flowlimitation
is identified using measurement of oesophageal pressure (Pes), which
requires a transducer catheter to traverse the UA. However, it is possible that the
presence of such a catheter could alter the mechanical behaviour and collapsibility of
the UA. Apart from this technical issue, the Pcrit technique is inherently difficult to
perform during sleep as altering applied pressure often results in measurementinduced
arousals. This is not an issue during general anaesthesia, which provides ideal
conditions under which to study UA collapsibility as arousals are suppressed, muscle
activation is minimised and other known modifiers, such as head posture, can be
controlled while still maintaining spontaneous ventilation. Given these advantages,
there is a case for using anaesthesia to characterise an individual’s UA collapsibility.
However, it is important to know how such measures equate to those made during
sleep. To date this relationship has been inferred by relating easily obtained indirect
sleep measures of collapsibility (e.g. apnoea hypopnoea index, AHI) to anaesthesia
Pcrit measures. As yet no study has compared UA collapsibility during anaesthesia and
sleep using the same metric (i.e. Pcrit). Furthermore while the anaesthesia model has
been used to demonstrate the effect of head posture on UA collapsibility, the effect
during sleep has yet to be investigated.
Aims. The aims of the studies described in this thesis were to utilise two distinct states
of human consciousness, namely sleep and general anaesthesia, to examine: (i) the
effect of Pes monitoring on UA collapsibility; (ii) the mechanisms underlying the state
dependent differences in UA collapsibility; and (iii) the effect of head posture on UA
collapsibility.
KW - Upper airway collapsibility
KW - Pharyngeal airway
KW - Propofol anaesthesia
KW - Sleep
KW - Head/Neck posture
KW - Oesophageal catheter
M3 - Doctoral Thesis
ER -