Table 2- Characterization of the studies on the use of heat and moisture exchangers as compared with the conventional humidifiers.
STUDY/COUNTRY
Martin et al., 1990/
SETTING
ICU
DATA ANALYSIS
Quantitative
variables
STUDY LIMITATIONS
were
compared using the Student t test.
COMPLICATIONS
Pneumonia was diagnosed on the basis of
Hypothermia in 22% and 12% of
purulent secretion. It did not involve
the patients belonging to the HME
PAV incidence density.
and HH groups, respectively (p <
OTHER
EVIDENCE
BENEFITS
LEVEL
Not reported.
1C
Not reported.
1C
1C
0.01). Six and no cases of tube
occlusion were reported in the
HME
and
HH
groups,
respectively (p < 0.01).
The study was interrupted after
the death of a patient belonging to
the HME group due to total
obstruction of the endotracheal
tube.
Roustan et al., 1992
ICU
Both groups were compared using
Sample size was not calculated.
Nine
the
The randomization procedure was not
endotracheal tube occlusion in the
described.
HME
Student
t,
Mann-
Whitney, Chi-square, and Fisher
and
and
no
events
HH
groups,
exact tests for differences in
respectively.
frequency.
episodes of atectasis in the HH
Regression
was
conducted for the incidence of
nosocomial
Nine
of
and
ten
and HME groups, respectively.
pneumonia,
atelectasis, and tube occlusion.
Dreyfuss et al., 1995
ICU
The Student t test was used for the
The randomization procedure was not
Report of severe occlusion that
The use of HME
continuous variables. The Chi-
described.
required cannula exchange due to
reduces costs and
square test with Yates correction
excluded after randomization. Sample
clotting
staff working time.
was employed for the categorical
size calculation was not reported.
hematemesis) in the HME group.
Various
patients
were
(patients
with
variables. The Mann-Whitney test
Six patients required cannula
was
exchange due to obstruction by
used
to
compare
non-
parametric variables.
Boots et al., 1997
ICU
secretion in the HME group.
The patients’ characteristics were
The randomization procedure was not
compared by paired t test. The
described.
Not reported.
The use of HME
1C
reduces costs.
PAV rate was evaluated using the
log rank test.
Kirton et al., 1997
ICU
Analysis of variance and non-
Non-blinded
study.
ICU specifically
paired Student t test.
admitted trauma patients.
The HME and HH groups did not
The use of HME
differ in terms of endotracheal
reduces costs.
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tube obstruction.
Kollef et al., 1998
ICU
Student t and Wilcoxon tests were
The randomization procedure was not
Tube obstruction was not detected
The use of HME
used (according to normal and
described. No mention of blinded study.
in any of the groups.
reduces
non-normal distribution).
Time elapsed during filter exchange was
Chi-square and exact Fisher tests
not controlled.
were
PAV diagnosis criteria did not include
employed
to
compare
categorical variables.
Results
were
costs
1C
by
50%.
bronchoalveolar lavage.
confirmed
by
multiple logistic regression.
Memish et al., 2001
ICU
The Student t test was employed.
The statistical power was not calculated.
Not reported.
Nursing staff spends
1C
less time discarding
the condensate that
builds up
in
the
circuit. The use of
HME reduces costs.
Lacherade et al., 2005
ICU
The Student t test was employed
Differences between the two populations
Tube occlusion rates were lower
On
for continuous variables. The Chi-
with respect to HIV infection. Phisicians
in the HME group (1 case) as
literature studies, the
square test was used for the
and researchers were not blinded.
compared with the HH group (5
paper mentions that
cases).
the use of HME
categorical variables. Multivariate
logistic
regression
was
also
the
basis
of
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reduces costs.
performed.
Boots et al., 2006
ICU
Sample size was determined using
Pneumonia was diagnosed according to
HME
the difference between two ratios.
CPIS
resistance to airflow than the
(Clinical
Pulmonary
Infection
may
present
higher
The use of HME
reduces costs.
1C
Univariate analysis involved the
manufacturer’s
Score).
use of Student t and Kruskal-
specifications
after use for 24 h.
Wallis tests. The difference in
PAV rate among groups was
evaluated by Kaplan-Meier and
log rank tests.
Lorente et al., 2006
ICU
Quantitative
variables
were
Temperature and moisture were not
compared using the Student t test.
monitored.
Five risk models proportional to
confirmed by tracheal aspirate. After
Cox were constructed for PAV
randomization, patients under mechanical
analysis.
ventilation for less than five days were
excluded.
PAV
Sample
diagnosis
calculation
was
Not reported.
No
benefits
have
been reported for the
use of HME.
was
conducted, but it did not reach a
suficiente number of patients. Wide
confidence interval. Incidence density
was not approached. Immunosuppressed
patients were excluded.
ICU: Intensive Care Unit; PAV: Pneumonia associated with mechanical ventilation; HME: Heat and moisture exchangers; HH: Heated Humidifiers.
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