do we do as we say we do?
TRANSCRIPT
3 Cheng KS, NG JM. Airway loss during
tracheostomy. Canadian Journal of
Anesthesia 2002; 49: 110.
Simple monitoring of cufftracheal pressures
In 1984 Seegoblin and Hasselt exam-
ined tracheal cuff pressure and mucosal
blood flow [1], recommending that cuff
inflation pressure should not exceed
30 cm H2O ⁄ 22 mmHg. Adequacy of
cuff inflation is conventionally deter-
mined by palpation of the external
balloon. Previous studies suggest that
this approach is unreliable; Fernandez
et al. [2] found that accuracy for esti-
mation by this method was 69% for
high pressures and 73% for low pres-
sures. Under-inflation is also deleteri-
ous. Micro-aspiration of secretions can
occur, leading to ventilator associated
pneumonia. When not measured, staff
are more likely to over-inflate cuffs to
prevent these problems [3].
We conducted a two-phase audit
cycle over 6 months, separated by a
clinical intervention. The phases
involved a survey of tracheal cuff pres-
sures on the Intensive Care Unit at
Wrexham Maelor Hospital, Wrexham,
UK. Fifteen consecutive patients were
monitored in each phase; cuff pressures
were recorded on admission (or on
intubation) and 24 h after intubation.
Pressures were measured by the same
investigator using an inflation-deflation
device (Portex, Smiths Medical Inter-
national, Watford, Herts, UK). Pressure
was measured during the inspiratory
phase. One month after completion of
phase one, the following clinical inter-
ventions took place: cuff pressure mea-
surement devices were made available at
each bedside; staff were trained in their
use; and twice daily measurements of
cuff pressure were made, and the mea-
sure incorporated onto daily record
chart. Re-audit (phase two) took place
one month following this intervention.
The data were compared, examining
two main elements: magnitude of dif-
ference between measured cuff pressure
and recommended pressure; and intra-
patient variability in cuff pressure over
24 h. The desirable range chosen for
audit purposes was set at 18–24 mmHg.
Before clinical intervention 12 out of 15
patents had an initial cuff pressure over
the desired range. On average these
pressure were 19 mmHg above the
upper acceptable limit. In phase two,
once again 12 out of 15 patients’
pressures were out of the desirable
range but on average these pressures
were only 8 mmHg above the upper
limit. In phase two the range of cuff
pressures seen was smaller at 22–
38 mmHg (range of 16 mmHg) com-
pared to the range of pressures seen in
phase one: 18–68 mmHg (range of
50 mmHg). Data from both phases
were also compared with regard to
intrapatient cuff pressure variability over
the 24 h studied. During phase one,
pressures differed, on average, by
9 mmHg over 24 h for any individual
patient. This figure fell to 3 mmHg in
phase two.
Numerous articles conclude that reg-
ular cuff pressure monitoring is key in
maintaining pressures within certain
limits [3–5]. This audit supports these
findings. We found reduced variability
in cuff pressure in individual patients
over 24 h, something less emphasised in
the literature. We suggest that regular
cuff pressure monitoring creates a
smoother profile in cuff pressure for
individual patients. Few studies examine
the significance of fluctuations in tra-
cheal cuff pressure with relation to
mucosal blood flow. The avoidance of
wide fluctuation in an individual’s tra-
cheal cuff pressure may prevent an
ischaemia-reperfusion-ischaemia cycle
affecting tracheal mucosa.
D. Huckle
P. Hughes
Wrexham Maelor Hospital
Wrexham, Wales, UK
E-mail: [email protected]
References1 Seeglobin RD, Hasselt GL. Endotra-
cheal cuff pressure and tracheal mucosal
blood flow, endoscopic study of effects
of four large volume cuffs. British
Medical Journal 1984; 288: 965–8.
2 Fernandez R, Blanch L. Endotracheal
cuff pressure assessment: pitfalls of fin-
ger estimation and need for objective
measurement. Critical Care Medicine
1990; 18: 1423–6.
3 Vyas D, Inweregbu K, Pittard A.
Measurement of tracheal cuff pressure
in Critical Care. Anaesthesia 2002; 57:
275–7.
4 Braz JR, Navarro LH, Takata IH,
Nascimento Junior P. Endotracheal cuff
pressure: need for precise measurement.
Sao Paulo Medical Journal 1999; 117:
243–7.
5 Jaber S, El Kamel M. Endotracheal cuff
pressure in intensive care unit: the need
for pressure monitoring. Intensive care
Medicine 2007; 33: 917–8.
Do we do as we say we do?
Questionnaires that involve surveys of
clinical practice are widely used for data
collection in the National Health
Service. In our experience, they are
enthusiastically thrust into our pigeon
holes and e-mail inboxes with alarming
regularity. We were interested in the
reliability of results obtained in this way,
so we e-mailed the authors of five postal
surveys to ask if they had been able to
verify their results. We received three
responses all confirming that they had
not.
Poorly designed studies with ill
defined targets, insufficient sample size
and ambiguous questions resulting in a
low response rate are just some of the
potential pitfalls. In addition to these,
we would like to pose the question ‘do
we actually do what we say we do?’ If
the answer is ‘no’, then even the most
robust survey will fail because the results
are fundamentally flawed. We are not
suggesting that responses are deliber-
ately intended to be dishonest or mis-
leading, rather that they are reflections
of our best intentions that we may or
may not fulfil.
In an attempt to assess the value of
questionnaires, we carried out a simple
two-part study of fresh gas flow rates
used with the circle system during
anaesthesia. The first part involved the
discrete observation of the fresh gas
flow being used by 51 permanent
members of staff in a teaching hospital.
The fresh gas flow was recorded when
the anaesthetist concerned was seated
and writing the notes (approximately
30 min into the case) as we assumed
this indicated the anaesthetist was
Anaesthesia, 2010, 65, pages 207–217 Correspondence......................................................................................................................................................................................................................
� 2010 The Association of Anaesthetists of Great Britain and Ireland 215
satisfied with the settings. This was
repeated for the same 51 anaesthetists at
a later date in order to obtain a mean
figure. The second part of the study
involved a questionnaire sent to the
same 51 anaesthetists asking what fresh
gas flow they would use when anaes-
thetising a patient with the circle
system.
The data for both parts of the study
were completely anonymous and there-
fore comparison between individual
stated and actual fresh gas flow was
not possible, but as we were able to
obtain a 100% response to the ques-
tionnaire this ensured that group com-
parison was valid. Our findings were
plotted on a graph and a median (IQR)
was obtained for both stated and
observed fresh gas flow. We found that
the written results revealed a median
(IQR) fresh gas flow of 1.5 (1-2)
l.min)1. However in the observed
results, the median (IQR) value for
fresh gas flow was 2 (1.5-3) l.min)1.
The graph (Fig. 1) illustrates the dis-
crepancy between the two sets of data
much more clearly.
There is undoubtedly potential for
error in the observed results as we had
to assume maintenance fresh gas flow
had been set. Furthermore, we were
unable to establish whether there were
extenuating circumstances as this would
have revealed that a survey was being
carried out.
Consent for the secret observations of
the first survey could not be obtained
from each individual as this would have
invalidated the survey. The project was
discussed with the clinical service direc-
tor and the lead consultant for audit,
and permission was given for it to be
completed for internal presentation.
Subsequently, after presentation to the
department, retrospective consent was
given for publication for which we are
most grateful.
W. King
J. Kemp
M. Crosse
Portsmouth Hospitals NHS Trust
Portsmouth, UK
Poole Hospital NHS Trust
Poole, UK
Southampton University Hospital
NHS Trust Southampton, UK
E-mail: [email protected]
An unseen obstruction
A 9-year-old child required general
anaesthesia for laparotomy. Surgery
and intra-operative anaesthesia were
uneventful. The child’s trachea was
extubated and oxygen was administered
via a size-3 Intersurgical facemask
(Wokingham, Berkshire, UK). Carbon
dioxide was not observed on capnogra-
phy and the child’s breathing pattern
was clearly obstructed. Airway manoeu-
vres were performed with the addition
of a small amount of positive end-
expiratory pressure to counter any pre-
sumed laryngospasm.
A second anaesthetist arrived at this
point to start the next operating list and,
standing adjacent to the first, noticed
that fogging was occurring: not in the
mask as it should but over the nose and
mouth. This was un-observable from
the first anaesthetist’s position at the
head of the patient. The mask was
removed and the plastic backing of a
SkintactTM ECG electrode (Skintact,
Gloucestershire, UK) was found adher-
ent to the inside of the mask, perfectly
occluding the internal aperture. It was
removed, oxygen successfully delivered
to the patient, with immediate resolu-
tion of the obstructed breathing. The
child remained 99% saturated through-
out and suffered no adverse sequelae.
Anaesthesia related complications are
not uncommon in the paediatric pop-
ulation [1], occurring at a rate of
between 2.4% and 8.6% of anaesthetics,
varying with age [2], with the highest
complication rates in children under the
age of three [3]. Marcus found that
42.5% of in-theatre incidents during
paediatric anaesthesia were due to hu-
man factors, the most common of
which were errors in judgement, fol-
lowed by failure to check equipment
[2]. The disastrous consequences of
equipment failure was highlighted by
the 2001 case from the Broomfield
Hospital in Essex, where a 9-year-old
child for routine minor surgery died as a
result of an intravenous line cap that was
occluding the anaesthetic circuit. This
case, and ten others like it, prompted a
formal police investigation (Operation
Orcadian), a response from the Depart-
ment of Health [4] and guidelines from
the Association of Anaesthetists of Great
Britain and Ireland [5].
Although we had checked our equip-
ment at the beginning of the case in
accordance with the published guide-
lines, the colourless ECG electrode
backing, with residual adhesive, had
been accidentally discarded into the tray
intended for the mask and laryngo-
scope, coming into contact with the
facemask and causing complete obstruc-
tion. Had a second pair of eyes, observ-
ing the events from a different angle,
not been present, the problem may not
have been resolved so quickly. To our
knowledge this is the first time a case
such as this has been reported and it
highlights the need for constant vigi-
lance, not just with equipment, but also
when discarding unwanted items.
B. Stanley
P. Roe
Cambridge University Hospital NHS
Foundation Trust
Cambridge, UK
E-mail: [email protected]
Figure 1 Questionnaire responses ( ) and observed fresh gas flow ( ).
Correspondence Anaesthesia, 2010, 65, pages 207–217......................................................................................................................................................................................................................
216 � 2010 The Association of Anaesthetists of Great Britain and Ireland