clinical investigations in critical care
Variations in the Measurement of
Weaning Parameters*
A Survey of Respiratory Therapists
Guy W. Soo Hoo, MD, MPH, FCCP; and Louis Park, MD
Objectives: Respiratory therapists differ in the methods used to obtain weaning parameters. A
questionnaire survey was conducted to better characterize those differences.
Design: A questionnaire survey was conducted among respiratory therapists from nine hospitals
in the Los Angeles area. The four-page, 32-question instrument was self-administered and
anonymous. Responses were tabulated for analysis.
Setting: Respondents from nine hospitals, three hospitals with residency training programs and
six community hospitals without training programs in the Los Angeles area.
Participants: One hundred two respiratory therapists.
Results: There was no universally acknowledged group of weaning parameters, although four
parameters were named by > 90%. There was wide variation in methods used to obtaining
weaning parameters. Almost all (91%) obtained measurements with the patients breathing their
current fraction of inspired oxygen, but there was great variability in the ventilator mode used to
collect these parameters (T-tube, continuous positive airway pressure, pressure support), with an
equally wide range of pressures added to each mode (0 to 10 cm H2O). There was great variation
in the time (< 1 to > 15 min) before recording weaning parameters. Measurement of parameters
was done either with bedside instruments or read from the ventilator display. The maximal
inspiratory pressure had great variation in the duration of airway occlusion (< 1 to 20 s), with the
most frequent time frame being 2 to 4 s. Differences were noted between therapists from the
same hospital as well as between hospitals.
Conclusions: There is great variation among respiratory therapists when obtaining weaning
parameters. This calls for further standardization of the measurement of weaning parameters.
(CHEST 2002; 121:1947–1955)
Key words: mechanical ventilation; respiratory therapists; weaning parameters
Abbreviations: CPAP ⫽ continuous positive airway pressure; Fb/Vt ⫽ frequency/tidal volume ratio; Fio2 ⫽ fraction of
inspired oxygen; MIP ⫽ maximum inspiratory pressure; PS ⫽ pressure support; RR ⫽ respiratory rate; V̇e ⫽ minute
ventilation; Vt ⫽ tidal volume
timing of extubation or discontinuation of
T hemechanical
ventilation remains one of the more
challenging aspects of critical care management. A
*From the Pulmonary and Critical Care Section, West Los
Angeles Veterans Affairs Medical Center, and Department of
Medicine, UCLA School of Medicine, Los Angeles, CA.
Manuscript received April 17, 2001; revision accepted January 4,
2002.
Correspondence to: Guy W. Soo Hoo, MD, MPH, FCCP, West
Los Angeles VAMC, Pulmonary and Critical Care (111Q), 11301
Wilshire Blvd, Los Angeles, CA 90073; e-mail: Guy.Soohoo@
med.va.gov
www.chestjournal.org
variety of strategies have been proposed, beginning
with measurements collectively referred to as “weaning parameters,” followed by trials of spontaneous
breathing, partially supported breathing, or a more
gradual reduction in ventilator support.1 These
weaning parameters usually consist of measurements
of respiratory rate (RR), tidal volume (Vt), vital
capacity, minute ventilation (V̇e), and maximum
inspiratory pressure (MIP). Other parameters include the frequency/tidal volume ratio (Fb/Vt), dead
space ventilation, inspiratory pressure at 0.1 s, work
of breathing, compliance, or an index (eg, thoracic
CHEST / 121 / 6 / JUNE, 2002
1947
compliance, RR, arterial oxygenation, MIP index)
derived from the aforementioned variables.2–9
None of the parameters have perfect positive or
negative predictive capability, but in unison provide
insight about a patient’s status. They may serve as
predictors of the ability to tolerate unassisted ventilation as well as the need for continued ventilator support. It is imperative that these measurements are
reproducible and accurate. Uniformity in techniques
and data acquisition would be obvious requirements.
This is self-evident and has led several investigators to
call for the standardization of weaning parameters.10 –12
Current clinical guidelines primarily list threshold
values.13 Full descriptions of weaning parameters
and techniques are not provided, but are available as
references. These references usually refer to experimental and/or clinical studies with conditions and
equipment that may not be universally available or
applicable. Other sources may provide a reasonably
detailed description of the technique,14,15 but are
lacking in details that may be considered routine
(fraction of inspired oxygen [Fio2], ventilator mode,
duration before measurement).
The extent of variation in measurement of weaning parameters is unknown. Observation at our
institution suggested significant variation, but this
may not be reflective of general practice. Better
characterization would not only provide support for
standardization, but also identify areas in which to
focus educational efforts. This led to the following
questionnaire survey on the weaning practices of
respiratory therapists in the Los Angeles area.
Materials and Methods
A self-administered four-page, 32-item questionnaire was developed and piloted among respiratory therapists at our institution (see Appendix). The items specifically addressed the methods by which weaning parameters were obtained, and were based
on published descriptions of the techniques incorporating input
from the therapists. The questionnaires were anonymous and
required about 10 min to complete. Some questions allowed
multiple responses, and each response was tabulated for analysis.
Nine hospitals in the Los Angeles area participated in the
survey. Three of the hospitals have active residency training
programs in all the major disciplines (medicine, surgery, etc.),
while the other six were community hospitals without training
programs. All of the hospitals have ⬎ 100 inpatient beds, with
two of the teaching hospitals having ⬎ 500 inpatient beds. All of
the hospitals have from 20 to 50 ICU beds, except one of the
training hospitals with ⬎ 50 ICU beds. After obtaining permission for administering the questionnaire from the director of each
respiratory therapy department, the questionnaires were distributed to members at the individual hospitals. When completed,
the questionnaires were either retrieved by one of the investigators or mailed back to our institution.
The responses were tabulated using an Excel spreadsheet
(Microsoft; Redmond, WA). Data were examined both in aggregate pooling all respondents as well as focusing on respondents
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from the same hospital. Statistical analysis with comparison of
proportions was performed using Primer for Biostatistics software (Version 4.0; McGraw-Hill; New York, NY).
Results
Of a total of 166 questionnaires distributed, 102
questionnaires (61%) were completed and returned
for analysis. The majority of respondents (75%)
report ⬎ 5 years of experience, and over half are
certified respiratory therapists. Of the 102 respondents, 46 persons (45%) work in teaching institutions. Ventilator management is primarily directed
by specialty internists (pulmonary/critical care)
[41%], but the therapists also receive directions from
others (general internists, surgeons, specialty surgeons, anesthesiologists, and physicians in training).
Most of the respondents were responsible for 1 to
9 patients receiving ventilation per shift, with two
respondents (2%) responsible for ⬎ 10 patients receiving ventilation. Most of the respondents (69%)
noted no specific time for obtaining weaning parameters, but 32 respondents (31%) responded that
weaning parameters were obtained only during daytime hours (before 3 pm). The majority of respondents (68%) noted that patients were extubated at
any time, with 32% noting that extubation occurred
primarily during daytime hours and never after 8 pm.
About one half of the therapists (49%) responded
that they did not require a specific order for weaning
parameters. When analyzed based on the type of
institution, 30 therapists (65%) from teaching institutions, compared to 22 therapists (39%) at a nonteaching institution, responded that weaning parameters required an order. This difference (p ⫽ 0.016,
z ⫽ 2.414) likely reflects the increased availability of
physicians at a teaching institution. The majority of
respondents (79%) believed that weaning parameters consisted of a predesignated group of variables.
Most of the therapists (95%) required patients to
be arousable before performing weaning parameters,
but approximately one half have obtained these
measurements in unconscious patients (47%). Most
of the therapists (91%) obtained weaning parameters
with the patient breathing supplemental oxygen
(current Fio2 setting), with a minority having the
patient breathe room air.
Table 1 shows the ventilator mode in which
weaning parameters were obtained. Multiple responses were permissible and responses included
combinations of T-tube, continuous positive airway
pressure (CPAP), and pressure support (PS). Only
three respondents exclusively obtained weaning parameters with the patient breathing off the ventilator
and through a T-tube. The remainder utilized some
combination of T-tube or CPAP (97%), with or
Clinical Investigations in Critical Care
Table 1—Ventilator Mode in Obtaining Weaning
Parameters
Ventilator Modes
No. (%)
T-tube
T-tube
T-tube, CPAP
T-tube, CPAP, PS
CPAP
CPAP, no PS
CPAP/PS
CPAP level, cm H2O
0
1–5
6–10
Not specified
PS
PS, CPAP ⫽ 0
CPAP ⬎ 1 cm H2O, PS
PS level, cm H2O
1–5
6–10
Variable
Not specified
25 (25)
3
15
7
99 (97)
67
32
77
16
1
5
32 (31)
23
9
5
19
5
3
without added pressure, and with or without added
PS. Twenty-three respondents (23%) obtained weaning parameters using PS, but without added CPAP
pressure. Nine of the respondents used some combination of CPAP pressure and added support with
PS. Figure 1 provides a breakdown by hospital on
the modes used to measure weaning parameters. In
two hospitals (hospital A and hospital H), weaning
parameters were obtained only in the CPAP mode,
but even in those two hospitals, there were differences among respondents whether measurements
were performed with a CPAP of 0 cm H2O or 5 cm
H2O. In the remaining hospitals, CPAP was the most
common mode. In hospital F, hospital G, and hospital I, all of the respondents reported no additional
pressure in the CPAP mode (0 cm H2O). In the
others that reported measurement with added pressure, the pressure was variable, with the most common response of 3 to 5 cm H2O. This variability was
also noted when PS was used, with the range of
responses spanning 3 to 12 cm H2O.
Table 2 provides further information on the frequency, time to recording, and types of weaning
parameters. Most respondents (68%) reported obtaining weaning parameters one to five times per
week. Two respondents reported that they measured
zero weaning parameters in an average week. With
respect to the time, a small number (6%) reported
values for weaning parameters almost immediately
(⬍ 1 min), while others recorded values after ⬎ 15
min (5%). The most frequent time frame was between 1 min and 5 min (68%).
Table 2 also lists the most commonly reported
weaning parameters. No measurement was named
by all respondents. The most frequently reported
parameters (⬎ 90%) were the MIP, Vt, RR, and V̇e.
The Fb/Vt ratio was specifically reported by ⬍ 20%.
The combination of RR and Vt was reported by 94
of respondents (92%), and the Fb/Vt ratio can be
easily calculated from these two values. This variable
(Fb/Vt) was more often specifically reported by
Figure 1. Breakdown by hospital and representing the percentage of responses from each hospital of
the ventilator mode used to measure weaning parameters.
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CHEST / 121 / 6 / JUNE, 2002
1949
therapists from the teaching hospitals (16 of 46
respondents, 35%) as compared to community hospitals (3 of 56 respondents, 5%; z ⫽ 3.62; p ⬍ 0.01).
No other differences were noted between therapists
based on their hospital of practice in terms of
methods by which they measured or reported weaning parameters (T-tube vs CPAP vs PS).
Table 3 provides more information on RR, Vt, and
V̇e. These parameters can be directly measured
using a bedside spirometer, but can also be recorded
from the ventilator display or bedside monitor.
About 70% reported values using the ventilator
display. About 30% reported making direct measurements of these parameters, except for RR, which was
directly observed by almost 75% of respondents.
This parameter (RR) also had the greatest number of
dual responses, with approximately 40% using both
methods. This dual response was noted in ⬍ 10% for
Vt or V̇e.
Table 4 is devoted to the MIP. In contrast to the
other variables outlined in Table 3, the MIP was
obtained with a manometer by almost 90% of respondents as opposed to using the ventilator software package. Only 25% responded using both the
manometer or ventilator software package. There
was a wide range of occlusion times before reporting
the MIP, with the most frequent time between 2 s
and 10 s (88%). Most respondents (68%) obtained
Table 2—Weaning Parameters
Parameters
No. obtained/wk
0
1–5
6–10
11–15
ⱖ 16
Time to recording values, min
⬍1
1–2
3–5
6–10
11–15
⬎ 15
Variable
Weaning parameters reported
MIP
Vt
RR
V̇e
Vital capacity
Oxygen saturation
Heart rate
BP
Fb/Vt
Compliance
Temperature
Others (maximum expiratory pressure)
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No. (%)
2 (2)
69 (68)
20 (20)
7 (7)
4 (4)
6 (6)
45 (44)
24 (24)
6 (6)
3 (3)
5 (5)
13 (13)
100
100
95
91
89
69
50
22
19
16
8
1
three values, and most reported the highest value
(75%). The occlusion time was not uniform among
therapists in any of the hospitals surveyed. Figure 2
depicts the percent of therapists responding for each
time frame at each of the surveyed hospitals. In
hospital I, almost 90% of the therapists occlude the
airway for 2 to 4 s to obtain a MIP. The most
diversity can be seen in hospital B, where no single
time frame was marked by ⬎ 30% of the respondents.
Discussion
Despite several decades of use, the constellation of
bedside measures collectively referred to as “weaning parameters” have never quite met expectations.
Witness the large number of variables that are
considered weaning parameters and the continued
search for bedside measurements that more accurately predict successful discontinuation of mechanical ventilation.1–9,15 These physiologic markers may
provide insight about a patient’s ability to tolerate
discontinuation of mechanical ventilation, but they
do not address other factors that may prevent successful extubation (secretion control or clearance,
upper-airway obstruction, comorbidities). Their predictive value may worsen, as patients may be very
different from the original reference group (longer
duration of ventilation, age, gender, different measurement methodology, etc.). Trials of spontaneous
breathing have gained enthusiasm, but they can also
be viewed another type of weaning parameter, albeit
more dynamic and more pragmatic,16 but with the
same limitations as noted earlier.
Irrespective of the measurement or the manner in
Table 3—Weaning Practices
Practices
No. (%)
RR
Direct observation
Ventilator display
Both direct observation and ventilator display
Bedside monitor reading
Either direct observation, ventilator display, or
bedside monitor
Vt
Direct measurement with bedside spirometer
Ventilator display
Both direct measurement or ventilator display
Calculated from ventilator readings
(V̇e/frequency)
V̇e
Direct measurement with bedside spirometer
Ventilator display
Both direct or vent display
74 (73)
68 (67)
40 (39)
11 (11)
9 (9)
31 (30)
75 (74)
9 (9)
19 (19)
33 (32)
72 (71)
7 (7)
Clinical Investigations in Critical Care
Table 4 —Weaning Parameters
Parameters
MIP
Direct measurement with manometer
Measurement using ventilator software
Both direct measurement or ventilator software
Duration of airway occlusion during MIP, s
⬍1
2–4
5–10
11–15
16–20
⬎ 21
Variable
MIP measurements, No.
One
Two
Three
Four
Variable
Reported MIP
Average of values obtained
Highest value obtained
Most reproducible
No. (%)
89 (87)
39 (38)
25 (25)
7 (7)
57 (56)
22 (22)
5 (5)
5 (5)
0 (0)
6 (6)
3 (3)
27 (26)
69 (68)
2 (2)
1 (1)
24 (24)
77 (75)
1 (1)
which the information is used, weaning parameters
can only be useful if they accurately reflect the
patient’s condition. Respiratory therapists play a
crucial role, as they are delegated the task of obtaining and reporting weaning parameters. It follows that
accuracy is related to measurement techniques, with
uniform techniques likely to produce the most reliable information. Available guidelines are general
and lack explicit details. This in turn allows some
latitude in these measurements.13,14
The results of this survey confirm the wide diversity in measurement techniques of weaning parameters among respiratory therapists. The differences
involve nearly every facet of measurement, and
occur among therapists from different hospitals, as
well as among therapists in the same hospital.
There is no “consensus” as to which measures
constitute weaning parameters. No parameter was
named by all of the respondents, although four were
noted in ⬎ 90% (MIP, Vt, V̇e, and RR) and are
often considered the core group of weaning parameters. Although the Fb/Vt ratio has gained support
as the single most predictive measurement in weaning,2 it was specifically noted by ⬍ 20%. However,
the ratio is derived from RR and Vt, and therefore,
if not specifically reported, easily calculated. It was
also marked more often by therapists from teaching hospitals, suggesting that the Fb/Vt ratio may
not be embraced as widely in community hospitals as
teaching institutions.
Among the many variations in measurement, two
areas are especially noteworthy. First, there is conwww.chestjournal.org
siderable variation in the ventilator mode used to
record these variables. Most therapists (85%) made
measurements in the CPAP mode, with a minority of
respondents using a T-tube. In addition, there is no
uniformity in the amount of supplemental pressure
present during measurement.
Added pressure during measurement adds another layer of complexity to this issue. Minimal
amounts of pressure are based on the premise that
the pressure eliminates the resistance of the endotracheal tube, providing a more accurate assessment
of a patient’s status.17 It is unclear if this is a valid
assumption. There is no consensus as to the exact
pressure required to compensate for the endotracheal tube, and there may not be an attainable
consensus.18,19 A patient’s work of breathing can be
reduced with small amounts of CPAP or PS.20 It
follows that measurement over the range of pressures (1 to 10 cm H2O) reported in this survey could
also change a patient’s weaning parameters.
The effect of added pressure on one parameter
(Fb/Vt ratio) alters its ability to predict successful
extubation. The original report identified a threshold
value of 105, obtained with patients breathing
through a T-tube.2 Other investigators have examined the ratio with patients receiving partial support
(CPAP or PS) or combinations of both modes with
different levels of pressure or have followed the ratio
over time.21–23 They have either reported a decline
in its predictive capability or a need to adjust the
ratio higher when using added pressure.
The time to record values represents the other
major area of variation in measurement. The responses (⬍ 1 s to 15 min) in Table 2 outline this
variation. A better appreciation of the importance of
time can be gained by reviewing the MIP. Early
investigations utilized 30 to 50 s of airway occlusion
in this measurement.24,25 Marini and colleagues26
demonstrated continued increasing negative pressures that plateau after 20 s. Branson and colleagues27 found maximal pressures required a minimum of 12 s, and recommend 15 s of airway
occlusion. It follows that the MIP should be recorded after 15 to 25 s of airway occlusion.14 In this
survey, only 5% reported airway occlusion for 16 to
20 s. None responded with ⬎ 20 s. The most frequent response of 2 to 4 s is an inadequate occlusion
time, and would likely underestimate this parameter.
Almost 40% report using the ventilator software
package. This might minimize concerns with standardization, but these packages also underestimate
the MIP.28,29 This becomes evident when examining
the MIP measurement of one ventilator. In the
Puritan Bennett 7200a ventilator (Puritan Bennett;
Carlsbad, CA), activation of the maneuver initiates a
10-s time frame for measurement.30 Inspiration
CHEST / 121 / 6 / JUNE, 2002
1951
Figure 2. Breakdown by hospital and representing the percentage of responses from each hospital of
the occlusion time used when measuring the MIP. sec ⫽ second.
closes the proportional solenoid valves of the ventilator and occludes the airway for 3 s. Exhalation ends
the maneuver, and the maximum negative pressure
generated is reported as the MIP. The 3-s period is
much less than the recommended time frame for
airway occlusion, and only one breath is reported.
Other software packages may have different algorithms, but it is not surprising that this package underestimates the MIP.
Based on this survey, the vast majority of patients
undergoing MIP measurements do not have the
airway occluded for the recommended amount of
time. Other areas that may lead to variations in the
MIP include issues with reproducibility, maximal
effort, and test-to-test variation.31,32 If decision making is based on this parameter, numerous management issues can be affected, including the timing of
“weaning trials,” extubation, and tracheostomy.
Although there is much debate on the clinical
utility of weaning parameters, it is self-evident that
they must be obtained in a standardized fashion.
Only then can values be considered reflective of a
patient’s status and confidently incorporated into
clinical decision making. It is acknowledged that the
role of weaning parameters has decreased over
the past decade. However, one third of therapists
in this survey report making measurements more
than six times a week, and only two respondents
reported zero parameters a week. This suggests
that physicians still use these measurements in
patient management.
Based on responses to this survey, it is conceivable
1952
that weaning parameters obtained in the same hospital on the same day by different therapists on the
same patient could be very different because of
differences in measurement technique. Patients with
borderline weaning parameters would be most affected by this lack of standardization, but all patients
risk misclassification. This study was designed to
assess the measurement of weaning parameters by
the respiratory therapists of one community. Although limited in scope, it represents both private
and public hospitals and is likely representative of
the practice in other communities.
These results also raise questions about other practices, specifically trials of spontaneous breathing. Although this was not specifically addressed by the
questionnaire, there is likely a similar degree of variation with respect to the conduct of the trials using
T-tube, CPAP, or CPAP plus PS. The results of this
survey reinforce the need for standardization of all
techniques, as well as continued study of the parameters that may better identify a patient’s ability to
tolerate extubation.
Appendix
Weaning Parameters Survey Questionnaire
1. How many inpatient beds are in your hospital?
ⱕ 100
101 to 499
ⱖ 500
Not sure
Clinical Investigations in Critical Care
2. How many total ICU beds are in your hospital?
ⱕ 10
11 to 24
25 to 49
50 –99
ⱖ 100
3. What types of ICUs are in your hospital?
Medical ICU
Surgical ICU
Pediatric ICU
Coronary care unit
Combined medical-surgical ICU
Step-down unit with ventilators
Step-down unit without ventilators
Specialized ICU (ie, burn), please specify
4. Does your hospital have a chronic ventilator unit (ward
setting) without monitors?
Yes
No
5. What best describes the hospital that is your primary
practice?
Community hospital (example, Cedars-Sinai, Long
Beach Memorial)
County or municipal hospital (example, LAC-USC, Harbor
General)
University teaching hospital (example, UCLA, UCI Medical
Center)
Military or Veterans Affairs hospital
Specialized care hospital (example, Vencor, Barlow)
6. What best describes the physicians who most often manage
ventilator patients in your hospital?
General internist, general surgeon
Specialty internist (ie, critical care, pulmonary)
Specialty surgeon (cardiothoracic surgeon)
Anesthesiologist
Physicians in training (ie, interns, residents, fel lows)
7. Please mark the best description of your status.
Certified respiratory therapist
Registered respiratory therapist
Director of respiratory therapy unit (nonphysician)
Other, please specify
8. How long have you been in respiratory therapy?
⬍ 1 year
1 to 5 years
6 to 19 years
11 to 19 years
ⱖ 20 years
9A. Do “weaning parameters” (or extubation criteria) require a
physicians order?
Yes (if yes, skip to question 10)
No (if no, proceed to question 9B)
9B. If physician’s orders are not required for weaning parameters, are the parameters obtained on a regular basis in
ventilator patients?
Yes, please specify: daily, weekly
No
Other, please specify
10. How many ventilator patients are you responsible for during
an average shift?
1 to 4
5 to 9
ⱖ 10
Other, please specify
11. Is there a specified time in which weaning parameters are
obtained?
Yes, please specify
Only on day shift (7 am to 3 pm)
www.chestjournal.org
12.
13.
14.
15.
16.
17.
18.
19.
20.
Only on morning shift (7 am to 12 noon)
Only during a specified time of the morning (7 am to 10 am)
No, can be obtained at any time
How many times do you obtain weaning parameters per
week?
None
1 to 5
6 to 10
11 to 15
⬎ 16
Do physicians order “weaning parameters” as a general rule,
or do they specify specific parameters to be obtained?
Weaning parameters as a general order
Specify specific parameters to be obtained
Either, depending on the physician
Other, please specify
Which weaning parameters do you routinely report?
Heart rate
Temperature
RR
Vt
BP
V̇e
Negative inspiratory pressure or MIP
Fb/Vt (rapid shallow breathing index)
Oxygen saturation
Vital capacity
Compliance
Other, please specify
Do you obtain weaning parameters in unconscious patients?
Yes
No
What minimum level of consciousness is required before
proceeding with weaning parameters?
Asleep, arousable with light touch
Asleep, arousable with voice
Awake, able to follow commands but unable to
communicate by writing or mouthing words
Awake, able to follow commands and communi cate by
writing or mouthing words
Which mode of ventilation do you use when obtaining
weaning parameters?
T-tube (off ventilator)
CPAP, please specify amount of CPAP
PS, please specify amount of PS
Other, please specify
After changing the vent to obtain weaning parameters, how
long do you wait prior to recording the values?
⬍ 1 min
1 to 2 min
3 to 5 min
6 to 10 min
11 to 15 min
⬎ 15 min
Variable length of time, please specify reason for wait
Are weaning parameters obtained with the patient breathing
room air or with their current Fio2?
Room air
Fio2
Other, please specify
How do you measure RR?
Direct observation
Obtained from the digital readout of the ventilator
Obtained from the patient’s ICU monitor readout
Other, please specify
CHEST / 121 / 6 / JUNE, 2002
1953
21. How do you measure Vt?
Direct measurement using a hand-held spirometer
or ventilation measurement nodule
Obtained from instantaneous digital readout of the ventilator
Calculated by dividing V̇e by frequency
Other, please specify
22. How do you obtain V̇e?
Direct measurement using a bedside spirometer or ventilation measurement module over 1 min
Spontaneous digital readout of the ventilator
Other, please specify
23. Do you routinely obtain negative inspiratory force or MIP?
Yes
No
24. What is the most common method of weaning patients at
your hospital?
Synchronized intermittent mandatory ventilation
PS
CPAP (no PS)
Synchronized intermittent mandatory ventilation plus PS
T-tube
CPAP plus PS
No uniform method, depends on physician
Other, please specify
25. When are patients extubated at your hospital?
Only during the day shift (before 3 pm)
Only during the morning (before 12 noon)
At any time, but never in the evening (after 8 pm)
At any time
Other, please specify
26. How do you measure negative inspiratory force or MIP?
Manually, using a bedside spirometer
Using the bedside software package
Using an esophageal balloon/pulmonary monitor unit (ie,
Bicore CP-100) Other, please specify
27. How long do you occlude the airway for the negative
inspiratory force or MIP?
⬍1 s
2 to 4 s
5 to 10 s
11 to 15 s
16 to 20 s
⬎ 21 s
28. How many times do you repeat the negative inspiratory force
or MIP?
Once
Twice
Three times
Four times
Other, please specify
29. If you obtain multiple negative inspiratory force values, how
do you report the final MIP?
Only obtain one negative inspiratory force value, thus not
applicable
Average the negative inspiratory force values ob tained
Use the highest negative inspiratory force value obtained
Other, please specify
30. What types of ventilators do you most commonly use?
Puritan Bennett 7200
Bear III or II
Siemens 900C
Hamilton Veolar
Other, please specify
31. Do you use continuous ECG monitoring while obtaining the
weaning parameters?
Always (100%)
Most of the time (⬎ 75%)
1954
Infrequently (⬍ 25%)
Almost never (⬍ 5%)
Other, please specify
32. Do you use continuous pulse oximetric monitoring when
obtaining weaning parameters?
Always (100%)
Most of the time (⬎ 75%)
Infrequently (⬍ 25%)
Almost never (⬍ 5%)
Other, please specify
Thank your for your cooperation. We would appreciate any other
comments.
References
1 Manthous CA, Schmidt GA, Hall JB. Liberation from mechanical ventilation. Chest 1998; 114:886 –901
2 Yang KL, Tobin MJ. A prospective study of indexes predicting
the outcome of trials of weaning from mechanical ventilation.
N Engl J Med 1991; 324:1445–1450
3 Morganroth ML, Morganroth JL, Nett LM, et al. Criteria for
weaning from prolonged mechanical ventilation. Arch Intern
Med 1984; 144:1012–1016
4 Sassoon CSH, Te TT, Mahutte CK, et al. Airway occlusion
pressure: an important indicator for successful weaning in
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