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DOI 10.1378/chest.99.3.630
1991;99;630-636Chest
J R Bach and A S Alba
regimen of noninvasive ventilatory support.
Intermittent abdominal pressure ventilator in a
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630 Noninvasive Wnthatory Support (Bach, Alba)
Intermittent Abdominal Pressure Ventilator
in a Regimen of Noninvasive Ventilatory
Support*
John R. Bach, M.D.;t and Augusta S. Mba, M.D4
The purpose of this work is to present 640 patient-years of
experience using the intermittent abdominal pressure yen-
tilator (IAPV) in aregimen of noninvasive ventilatory
support for patients with paralytic/restrictive respiratory
insufficiency. Fifty-two of the 54 patients who used the
IAPV used 24-hour noninvasive ventilatory support. Thirty-
eight of the 52 patients could tolerate less than 15 minutes
of free time off their ventilators except by the successful
use of glossopharyngeal breathing (GPB). No patient,
however, retained an indwelling tracheostomy and none
required or used supplemental oxygen therapy. Forty-eight
of the 54 patients used the IAPV for daytime support for a
mean of 12.9 ± 11.5 years (3 months to 39 years) while using
other forms of noninvasive support overnight. All 48 pa-
tients maintained normal minute ventilation and end-tidal
Pco2 on the IAPV. One patient used the IAPV only for
nocturnal ventilatory support for six months. Five patients
relied on the IAPV as their sole method of ventilatory
support 24 hours a day for a mean of 13.4±11.2 years
(range, 2 to 31 years). Three of these five patients had no
free time and were studied by nocturnal SaO, monitoring
that demonstrated a mean Sa02 of 95 percent or greater
and a minimum Sa02 of 86 percent. The maximum end-
tidal Pco2 was 49 mm Hg during sleep on the JAPY. The
48 patients receiving daytime IAPV support reported few
difficulties. However, two of the five patients using the
IAPV 24 hours aday had development of sacral decubiti.
The IAPV became ineffe#{233}tivefor 12 patients after 12.3 ± 9.5
years of use. These patients then switched to daytime
mouth IPPV. We conclude that the IAPV is a safe and
effective method of long-term daytime ventilatory support
for patients with paralytic/restrictive respiratory insufli-
ciency. Its use is optimized when employed in combination
with other noninvasive methods ofventilatory support, thus
eliminating the need for tracheostomy, and optimizing the
use of GPB. Regular follow-up is important because the
IAPV can become less effective with time.
(Chest 1991; 99:630-36)
GPB =glossopharyngeal breathing; GPmaxSBC glos-
sopharyngeal maximum single breath capacity; IPPV inter-
mittent positive pressure ventilation; IAPV intermittent ab-
dominal pressure ventilator; SaO4oxygen saturation
The prototype intermittent abdominal pressure
ventilator (IAPV), the Bragg-Paul Pulsator, was
first described by C. J. McSweeney’ in 1938. “The
apparatus ...consists of a distensible rubber bag
applied around the patient’s chest in the form of a
belt, this belt being rhythmically filled with, and
emptied of, air. The rate of compression can be
modified to suit the respiratory rate of the patient.”
This was successfully used in treating 34 patients with
acute diphtheritic respiratory muscle paralysis. The
modern IAPV,2 the Exsuffiation belt (Lifecare mc,
Lafayette, CO) or Pneumobelt (Puritan-Bennett Inc,
Boulder, CO), consists of an elastic inflatable bladder
*From the Department of Physical Medicine and Rehabilitation,
University Hospital, The New Jersey Medical School, University
of Medicine and Dentistry of New Jersey, Newark (Dr. Bach); and
the Department ofRehabilitation Medicine, Goldwater Memorial
Hospital, New York University, Roosevelt Island, NY.
tAssistant Professor of Physical Medicine and Rehabilitation.
tAssociate Clinical Professor of Physical Medicine and Rehabilita-
tion.
This work was supported by the Department of Education Crants
and Contracts Service RED: Innovation Grant C008720331.
This work was performed on patients referred to University
Hospital, Newark, NJ, and Goldwater Memorial Hospital, Rouse-
velt Island, NY.
Manuscript received October 25, 1989; revision accepted July 11.
Reprint requests: Dt Bach, University of Medicine and Dentistry
ofNJ, Newark 07103
incorporated within an abdominal corset worn beneath
the patient’s outer clothing. The bladder compresses
the abdomen when cyclically inflated by a positive
pressure ventilator. The abdominal contents then
move the diaphragm upwards causing a forced exsuf-
flation. With bladder deflation, the abdominal contents
and diaphragm fall to the resting position as a result
of gravity and inspiration occurs passively. Since the
passive inspiration that follows is dependent on gravity
to return the diaphragm to its prebladder insuffiation
position, a trunk angle of 3O or more from the
horizontal is necessary for adequate tidal volumes to
occur.2 If the patient has any inspiratory capacity or is
capable ofeffective glossopharyngeal breathing (GPB),
he can add his autonomous tidal volume to the passive
inspiration.
There have been numerous publications on the
long-term use of negative pressure body ventilators
such as the Iron Lung and Chest Shell Ventilator
(Lifecare Inc, Lafayette, CO; Emerson Co, Cam-
bridge, MA). However, there have been only scattered
reports on the use of the IAPV, and then for only a
few patients. There has been one publication con-
cerning its use in a large patient series with tracheos-
tomies.7 We report its use in a regimen of noninvasive
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ventilatory support by 54 patients without tracheos-
CHEST I99 I3IMARCH, 1991 631
tornies.
PATIENTS AND METHODS
The maximum period of time that a patient can remain free of
assisted ventilation by using his own respiratory muscles is his free
lime.8 The point at which he complains ofdyspnea and fatigue and
requests to be placed back on ventilatory support is usually
accompanied by a decrease in SaO, below 90 percent and an
increase in end-tidal Pco, over 45 mm Hg. The free time varies
and depends on many factors, including position.’#{176} It also correlates
positively with vital capacity.8 We reviewed the records of 240
patients with paralytic/restrictive respiratory insufficiency requiring
24-hour ventilatory support without tracheostomies. The free time
and vital capacity (VC) were evaluated at least yearly for each
patient both with and without the use of CPB. The recorded VC
and maximum glossopharyngeal single breath capacity (CPmaxSBC)
were the maximum in four to five attempts made on a 9-L
respirometer (Collins Respirometer, Warren E. Collins Inc, Brain-
tree, MA) or a spirometer (Wright Spirometer, Mark 14, Ferraris
Development and Engineering Co Ltd. London, England). Pulmo-
nary studies, including measurements of respiratory rate, minute
oxygen consumption, minute ventilation, tidal volume, and oxygen
ventilatory equivalent both on the IAPV and, when possible, during
unassisted breathing, were also obtained by using the 9-L spirom-
eter.
Atrial of IAPV use was indicated for any patient with paralytici
restrictive respiratory insufficiency with six or less hours of free
time, who required little or no supplemental oxygen therapy and
who had sufficient oropharyngeal muscle function to articulate,
swallow, and clear oral secretions. Although we have used it for one
patient who had severe oropharyngeal muscle weakness and who
refused tracheostomy, its use was supplemented by assisted expul-
sion of pulmonary secretions with the aid of a mechanical forced
exsufflation device’#{176}” to prevent aspiration of food and secretions.
No patient with an abdominal or pelvic osteotomy or indwelling
catheter underwent a trial with the IAPV.
The 240 patients with severe alveolar hypoventilation (94, polio;
45 Duchenne muscular dystrophy; 31, spinal cord injury; 25, non-
Duchenne myopathy; 45, others) required greater than 12 hours of
ventilatory assistance per day. They all successfully learned to
ventilate themselves during daytime hours by mouth IPPV’’6 They
were either converted from IPPV via tracheostomy or were placed
directly on noninvasive aids” for ventilatory support. When on
mouth IPPV, these patients characteristically alternated taking
ventilator-assisted breaths with unassisted breaths until their res-
piratory insafficiency had progressed to the point that their free
time had become negligible. With no free time, every breath was
ventilator assisted and IAPV use became optimal. All of these
patients who had had indwelling tracheostomies had their trache-
ostomy sites closed, in some cases prior to introduction to the IAPV,
despite need for up to 24 hours of ventilatory aid. No patient used
supplemental oxygen at the time of his introduction to or during
his use ofthe IAPV.
Once having mastered daytime mouth IPPV, 209 ofthese patients
underwent trials of IAPV ventilatory support. All 31 who did not
undergo IAPV trials either wished to continue only mouth IPPV
and/or GPB except for one patient who continues to use the Chest
Shell for daytime aid. Seven were marginally ambulatory and did
not want the encumbrance of an IAPV. Four required aid for less
than two months. One patient anticipated too much difficulty using
an IAPV after her return to Nigeria. Eighteen patients went quickly
from six to eight hours ofdaytime mouth IPPV to 24 hours of mouth
IPPV and never tried the IAPV
Avariety of portable volume and pressure ventilators capable of
delivering up to 2,500-mI volumes or pressures to 60 cm H,O, and
up to 22 breaths per minute, were used to inflate the bladder in
the abdominal corset of the IAPV. The corset was fitted to the
patient with the curved lower border resting slightly above the
pubic arch and the horizontal upper border at the level of the
xiphoid or lower sternum. Optimal corset size and tightness for
ventilation and comfort were found by trial and error. Straps and
buckles, and more recently, Velcro closures, firmly secured the
corset on the abdomen and the ventilator hose connected the
bladder to the positive pressure ventilator. The optimal ventilator
pressure/volume for IAPV function was then determined by increas-
ing the pressure/volume to minimize the patients component to his
total tidal volume while maintaining end-tidal Pco, <45 mm Hg,
and since 1985, normal Sa02 as well (Fig 1). Inadequate lung and
chest wall compliance, the presence of severe back deformity, and
inability to sit at 30#{176}to 75#{176}were factors limiting successful use.
Noninvasive blood gas monitoring was also used in the yearly
evaluations of these patients. End-tidal Pco2 monitoring was per-
formed both while using the IAPV to determine any need to modify
IAPV pressure or rate, as well as with the IAPV turned off to assess
free time. Ventilation was considered adequate when the patient
became asymptomatic for hypoventilation and the end-tidal Pco
remained below 45 mm Hg.
Three ofthe six patients using the IAPV for nocturnal ventilatory
support also underwent continuous home sleep SaO, monitoring.
None of these patients had signfficant free time. Oxygen saturation
monitoring alone’ or when performed in conjunction with end-
tidal Pco, monitoring and/or polysomnography has been demon-
strated to reflect the improvements in nocturnal ventilation for
patients receiving noninvasive ventilatory assistance.’8’’ This
technique alone may be useful in gauging the adequacy of nocturnal
ventilatory assistance for patients not requiring supplemental oxy-
gen therapy.’
Pulmonary tract secretions were managed during respiratory
tract infections by chest therapy, vigorous manual assisted coughing,
and often by use ofa mechanical forced exsufflation device.’#{176}”
RESULTS
Of the 209 patients who were evaluated using the
IAPV, 31 continued to have periods offree time greater
than 2 h and chose to use mouth IPPV’’ for up to 20
hours ofdaily support despite a successful trial on the
IAPV. The lack of continuous need for assisted venti-
lation made mouth IPPV preferable to donning and
using the IAPV.
The remaining 178 patients used ventilatory aid 24
hours a day with less than 1 h of free time. Eleven
patients with no free time had successful trials on the
IAPV but preferred to use mouth IPPV and/or GPB
during the day. Of 11 other such patients using a chest
shell ventilator for daytime support, ten switched to
the IAPV after 2.3 ±1.8 years on the chest shell and
one has continued daytime chest shell use for 34 years.
One hundred twelve of the 178 patients failed to
achieve adequate ventilatory support by the IAPV as
documented by generally less than 200 ml IAPV
augmented tidal volumes, persistent dyspnea, end-
tidal PCO2 elevation (>45 mm Hg), and/or oxyhemo-
globin desaturation. Of these 112 patients, 67 had
severe scoliosis (thoracolumbar curves exceeding 75#{176}),
13 had moderate scoliosis (50 to 75#{176}),nine had mild
scoliosis (<50#{176}),and 23 had no apparent scoliosis. Of
the 32 patients in the latter two categories, at least
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Diagnosist
No. of
Patients
Age,
yri: Sitting % Predicted Supine % Predicted
IAPV
Use, yr
Pulio 24 32±12 389±387 8.3±8.5 393±445 8.4±7.9 20.6±9.8
SC! 16 34±18 362±238 6.8±5.9 374±309 7.7±7.3 4.1±3.2
Myopa 5 40±10 565±474 18.0±12.7 503±338 15.8±9.7 7.1±6.7
DMD 4 26±10 256±279 6.5±7.5 204±231 5.5±7.3 3.3±2.2
Other 5 56±13 362±273 6.3±4.8 334±249 6.3±5.2 8.7±6.7
*Values are mean ±SD.
tSC! =spinal cord injury; myopa, non-Duchenne myopathy; DMD, Duchenne muscular dystrophy; other motor neuron disease, three
patients; myelopathy, polymyositis, Friedreich’s ataxia, and synngomyelia, one each.
Age at onset ofIAPV use.
Table 1-Summary ofVC Values Related to Diagnosis and Ventilatory A1d
632 Nonlnvashm dntIIatory Support (Bach, Nb.)
four were markedly obese and three others had poor
pulmonary compliance and required mouth IPPV
insufflation pressures exceeding 40 cm H20. In addi-
tion to the above factors, the remaining unsuccessful
25 patients had varying degrees oflordosis along with
scaphoid abdomens that prevented sufficient IAPV
girdle capture of abdominal contents for adequate
diaphragrnatic excursion. Trials varying the IAPV
girdle and bladder size were not successful in aug-
menting inspiratory volumes to adequately ventilate
these patients. Thus, the IAPV significantly aug-
mented the ventilation of 11 of 91 patients with
moderate to severe scoliosis for a period oftime. Eight
ofthe 11 patients are dead with hypoventilation having
contributed to at least four of the deaths. A recom-
mended switch to mouth IPPV or tracheostomy IPPV
Table 2-1APV Component to Assisted Ventilation*
IAPV Total
Case Diagnosis Age,
yr VC,
ml VT
ml Bate Pres
cm H,O Volume
ml Assisted
total/IAPV Vi’f
ml Pco,
mm Hg
1 Polio 48 600 280 18 50 380 260 39
2 Myelo 61 570 210 16 40 2500 440 310 33
3 Polio 62 90 80 18 48 2450 360 350 33j
4 Polym 40
41 600
460 330
250 15
16 38
45 330
240
220
120 44
48
5 Polio 56
59 600
560 280
270 13
13 40
40 420
390 240
160
38
46
6 Polio 57 355 280 17 42 360 280 45
7 Polio 54 1430 370 15 42 520 260 44
8 Polio 31 220 130 20 45 320 300 26
9 Polio 49 0 0 21 32 1850 330 330 35
1011 Myopa 41 460 250 18 35 1800 370 180 40
11 Polio 54 250 130 19 42 370 215 41
11 57 260 150 18 45 220 130 48
12 Polio 33 267 78 20 48 354 354 36t
13 DMD 31 510 320 20 48 410 180 35
14 Myopa 53 460 200 17 40 450 450 24
1511 DMD 32
39
40
20
40
20
17
24
48
46
344
230
344
230
41
48
16 Polio 44
46
480
450
250
250
18
19 43
39 400
330 250
190
33
44
17 Myelo 76 510 380 18 40 820 650 46
18 Fried 69 380 290 18 38 406 282 43
19 Myopa 60 1400 530# 15 35 450 300 38
20 SC! 29 630 340 17 40 550 440 40
21 DMD 26 180 80 18 48 340 230 461
22 ALS 50 200 120 10 40 450 380 36
*All patients used the medium-size IAPV except where indicated. The diagnoses include poliomyelitis (polio), myelopathy (myelo), motor
neuron disease (MND), myopathy (myopa), high-level traumatic quadriplegia (SC!), polymyositis (polym), Friedreich’s ataxia (Fried),
Duchenne muscular dystrophy (DMD), and amyotrophic lateral sclerosis (ALS).
tIAPV component to the total assisted VT.
tVentilation routinely augmented by glossopharyngeal breathing throughout daytime hours.
§Discontinued IAPV use in favor ofmouth IPPV following the evaluation.
#{182}Smallsize IAPV.
IlLarge size IAPV.
#With accessory muscles.
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1000
4O’ K
J-K
1.5 1.0 0.5
CHEST I99 I3IMARCH, 1991 633
U-
0
(I,
L1J
-J
-J
-J
200
02.0
TIME (mm)
FIGURE 1. The respiratory rate (RR), minute ventilation (MV), minute oxygen consumption (VO’), tidal
volume (VT), and oxygen ventilatory equivalent (VEO,) both on the IAPV and, when possible, during
unassisted breathing can be derived from the spirogram (Collins 9 liter, Warren E. Collins Inc. Braintree,
MA). Note the increased slope (CD) indicates elevation ofthe respiratory level. The subsequent persistent
elevation of the respiratory level (H!) parallel to (AB) indicate3 increased Vo, and, therefore, work of
breathing, during unassisted breathing. The !APV component (AJ) and the patients component (1K) to the
total VT are determined by drawing a line parallel to AB through C (where the patient is at his resting
expiratory level). Note the patient’s decreasing component to her total Yt after restarting the IAPV (E). On
the IAPV, this patient with a vital capacity of320 ml had an RR of 17, Vo, of 182 ml, MV of6,130 ml, total
VT of360 ml with a 280-ml IAPV component and an 80-ml self-component, and a VEO, of3.4 L ofO, while
maintaining normal end-tidal Pco, and SaO2 indefinitely. On unassisted breathing, the patients RE was
28, MV was 6,720 ml, and Vt was 240 ml. She became dyspneic, hypoxic (SaO, decreased to 88 percent),
hypercapneic (end-tidal Pco, increased by >10 mm Hg), and her free time off the !APV was less than 2
mm.
was refused by all four patients. The IAPV was
effective, however, for 74 of 99 patients with little or
no scoliosis.
Of the 240 patients requiring daytime as well as
overnight ventilatory assistance, 141 had more than
6h of free time. Only one of these patients used the
IAPV. The others depended on mouth IPPV for 6 h or
more of daytime aid. Likewise, only nine of 172
patients with more than 1 h of free time used the
IAPV rather than mouth IPPV. Forty-three of the 68
patients with one hour or less of free time, however,
preferred IAPV use over mouth IPPV for their primary
daytime support. Thirty-four of these patients had 10
rnin or less of free time except by the use of GPB.
Fifty-four patients used the IAPV for long-term aid.
Their diagnoses, VCs, and length oftime on the IAPV
are listed in Table 1. Their most recent mean VCs
were 370 ±339 ml or 8.6 percent ofpredicted normal,
sitting, and 365 ±367 ml or 8.4 percent of predicted
normal, supine. Although the differences between
sitting and supine VCs were not significant for the
group as a whole, four patients had 40 percent or more
reduction in supine VC as compared with sitting, and
correspondingly less free time supine. One other
postpolio patient had a VC of 1500 ml (38 percent)
supine but only 650 ml (17 percent) sitting. She could
ventilate herselfunaided supine but had less than one
hour of free time when sitting. In some cases, symp-
toms of hypoventilation may be misdiagnosed unless
VCs are measured in both positions.8 Sixteen of these
patients, including ten patients with traumatic quad-
riplegia, three with motor neuron disease, and one
each with Duchenne muscular dystrophy, a non-
Duchenne myopathy, and polio, began use during the
last six years.
The 54 patients used the IAPV at a mean rate of
17.3 ± 2.8 per minute and pressure of 42. 1 ±4.6 cm
H20. Fifty patients were optimally ventilated by the
medium size girdle, two by the small, and one by the
large size girdle.
Twenty-two patients for whom IAPV supplemented
volumes were specifically measured are listed in Table
2. The technique for estimating the IAPV component
of the total assisted tidal volume is shown in Figure 1.
The most recent evaluation of IAPV use was listed.
Four patients whose most recent evaluations indicated
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634 Noninvasive Ventilatory Support (Bach, Nb.)
that IAPV use no longer provided adequate ventilation
also have a previous evaluation listed. These 22
patients had their autonomous tidal volumes supple-
mented by a mean of 313 ±107 ml by the IAPV One
patient with no measurable VC attained 1,200 ml of
tidal volume with the IAPV before bladder insufflation
pressures were decreased to prevent hyperventilation.
Coincident with introduction of the IAPV for day-
time aid, nocturnal ventilatory support was achieved
by the use of body ventilators16a1, for 30 patients
(ten, chest shell; eight, pulmowrap; five, rocking bed;
six, IAPV; one, iron lung) and noninvasive intermittent
positive airway pressure ventilation for 17 patients (16,
mouth IPPV; one, nasal IPP.8.115.17 When switch-
ing from nocturnal tracheostomy IPPV to mouth or
nasal IPPV, attention was paid to preventing leak from
the stoma of the plugged tracheostomy tube.
Forty-eight patients have successfully used the IAPV
for daytime support for a mean of 12.9 ±11.5 years
(one week to 39 years). One patient used the IAPV
only for nocturnal ventilatory support for six months.
The former switched to nocturnal nasal IPPV so that
she could lie supine.
Five other patients relied on the IAPV for their sole
ventilatory support 24 hours a day for a mean of
13.4 ±11.2 years (range, two to 31 years). All six
patients who slept on the IAPV slept at angles of 35#{176}
or greater. Four of these six patients had no free time.
Three ofthese patients with no free time were studied
by nocturnal SaO2 and end-tidal Pco2 monitoring that
demonstrated an average SaO2 of 96 percent for two
patients with a low SaO2 of92 percent and 91 percent
and a maximum end-tidal PCO2 of 43 and 49 mm Hg,
respectively. The other patient had an average SaO2 of
95 percent with a low of 86 percent, with Sa02 of less
than 90 percent for 1 percent of the night and a
maximum end-tidal Pco2 of42 mm Hg.
Four patients had their tracheostomies removed and
the sites closed prior to beginning use of the IAPV.
Seventeen patients had their tracheostomies removed
and the sites closed shorfly after beginning use of the
IAPV.
The absence ofan indwelling tracheostomy permit-
ted 22 of these patients to learn and optimally use
GPB. These 22 patients had a mean VC sitting of
291 ±285 ml or 6.5 percent of predicted normal, but
their mean glossopharyngeal maximum single breath
capacity (GPmaxSBC) was 1,798 ±709 ml. Nineteen
of the 22 patients increased their free time off venti-
latory support’ from a mean of 10 ±28 minutes without
GPB to 271 ±324 minutes with it. Only one of these
19 patients had 1 h or more of free time without
resorting to GPB, but 12 patients with less than 2 mm
offree time without GPB had 1 h or more with GPB.
All 22 patients routinely supplemented their IAPV
delivered volumes with GPB. This also improved the
volume and rhythm of the patients’ speech while on
the IAPV
The 54 patients began to use the IAPV at age
36.4 ±15.8 years (range, 13 to 72 years). Twenty-six
patients continue to use it at age 50.7 ±15.4 years.
Twelve patients had to abandon IAPV use that had
become ineffective for them (PC02 >45 mm Hg and
intervening symptoms of hypoventilation) at age
48.2 ±14.5 years in favor of continuous mouth IPPV
after 13.8 ±11.9 years of successful IAPV use. Before
discontinuing IAPV use in favor of daytime mouth
IPPV, IAPV pressures were increased to a maximum
of 60 cm H2O with end-tidal PCO2 monitoring. In no
cases, however, did this significantly increase the
supplemental inspiratory volumes, and some patients
exhibited a decreased assisted volume with increasing
IAPV pressures. For example, one patient had her
tidal volumes supplemented by 380 ml at an IAPV
pressure of 45 cm H20 both on a pressure ventilator
and on a volume ventilator with a delivered volume at
1,500 ml. The supplemented volume decreased to 350
ml on the volume ventilator at pressures greater than
50 cm H20 and volumes greater than 1,900 ml. Greater
than optimal IAPV pressures also frequently caused
patient discomfort. One other patient was weaned
from ventilatory assistance after six months of IAPV
use. One polio patient with oropharyngeal muscle
weakness switched to tracheostomy IPPV during an
episode of pneumonia and three patients (two with
amyotrophic lateral sclerosis, one with muscular dys-
trophy) switched because of severe oropharyngeal
muscle weakness after 29, 18, 6 and 1 years of IAPV
use, respectively.
Eleven patients died while using the IAPV after a
mean of9.3 ±4.4 years (range, 2 to 22 years) use. The
causes of death were lung cancer, myocardial infarc-
lion, sepsis from decubitus, motor vehicle accident,
drug abuse, unknown (two cases), pneumonia (two
cases), seizures while on mouth IPPV, and inadequate
nocturnal ventilatory support on a rocking bed. These
mortality figures in more than 640 patient-years of
IAPV use compare favorably with mortality figures in
comparable patient populations whose treatment in-
cluded tracheostomy for whom three-year survival
has been cited at 60 to 75 percent.’
The 26 patients who continue to use the IAPV
reported few difficulties during daytime use. One
patient switches regularly to mouth IPPV during meals
because of food regurgitation while on the IAPV. The
other patients, however, have no difficulty eating while
on the IAPV and some believe that the rhythmic
abdominal compression aids in digestion by increasing
motility. Clothing catching on the corset buckles,
which was once a problem, has been resolved by the
newly designed IAPV girdles with straps and Velcro
closures. The use of Velcro closures also make tight-
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CHEST I99 I3IMARCH, 1991 635
ening or loosening the belt easier for position changes
and pressure modification. The IAPV substitutes for
the abdominal muscles by helping the patient to belch
and to pass flatus. By glottic closure just prior to an
abdominal compression, the IAPV also assists the
patient in clearing secretions. Two of the five patients
on 24-hour IAPV use, however, had development of
sacral decubiti with fatal complications in one case.
DIsCussIoN
Miller et al noted average IAPV rates of 12 to 14
per minute with routine pressures ofSO to 60 cm H20.
He stated that no patient was safely ventilated at a
rate greater than 16. Alexander et al also noted using
pressures of 50 cm H2O. Our mean rate of 17.3 ±2.8
per minute and pressures of 42. 1 ±4.6 cm H20
correlate better with the recommendations of Hill
that are for rates of 16 to 28 breaths per minute and
pressures less than 45 cm H20. Hill, however, stated
that the IAPV was ineffective for patients with severe
respiratory failure. Fifteen of our patients with VCs
of 100 ml or less, including ten patients with no
measurable VC, were successfully ventilated by the
IAPV for two years or more .The reasons for the
differences in our rates and pressures with those of
the previous authors are unclear; however, prior re-
ports did not indicate the size of the IAPV girdles
used. Although we found the IAPV to be rarely
effective in patients with severe scoliosis, four such
patients were adequately ventilated by it for greater
than four years with scoliosis exceeding 75#{176}.Since its
effectiveness may decrease with time and loss of
pulmonary compliance, its use should he reevaluated
yearly.
Our experience agreed with previous suggestions
in that patients with severe respiratory insufficiency
adjusted well to and were successfully ventilated by
the IAPV while patients with minimal respiratory
failure had greater adjustment difficulties7 and gen-
erally preferred daytime mouth IPPV. Patients without
tracheostomies who had greater than 2 h of free time
generally used mouth IPPV 6 to 16 daytime hours and
preferred its use over the encumbrance of an IAPV.
Patients with 30- to 60-minute periods of free time
used their ventilators 24 hours a day but maintained
normal ventilation without the need to supplement
every breath by mouth IPPV. Patients with less than
30 minutes offree time generally assisted each breath
by mouth IPPV. The less the free time, the greater
the preference for the IAPV over mouth IPPV, and
the greater the need for and use of GPB.
Other than the IAPV, the only body ventilator that
can be used for daytime ventilatory assistance while
sitting is the chest shell. Of our 22 patients who have
used this ventilator for long-term daytime assistance,
11 switched to daytime mouth IPPV and ten switched
to the IAPV, and only one patient continues to use his
chest shell for daytime aid. In all cases, the chest shell
was found to be relatively cumbersome and pressure
leaks were relatively difficult to prevent for patients
active in their wheelchairs. Activities of daily living
were also impeded for patients who needed to lean
forward in their chairs for optimal function. Although
there is extensive medical literature on the use of this
device for nocturnal ventilatory assistance,’6’2” we
are not aware of any literature recommending its use
for daytime aid. Likewise, although nasal IPPV has
been reported to successfully assist nocturnal venti-
lation,8”7’9 in only one report was it used for patients
requiring 24-hour aid.8 Because of the poor cosmesis
and inconvenience that accompanies the need for
continuous attachment of the patient’s nose to venti-
lator tubing, we have found it useful for daytime aid
only for one patient who had insufficient neck excur-
sion to conveniently grab a mouth piece fixed adjacent
to the mouth for mouth IPPV and for whom the IAPV
was not effective.
Miller et al reported that the advantages of IAPV
use included plugging of the tracheostomy tube. The
fear of accidental tracheostomy tube disconnection
during tracheostomy IPPV was eliminated when on
the IAPV and speech was easier and louder. All of his
patients were tracheostomized or dependent on
phrenic nerve stimulation. Although 34 ofour patients
had less than 10 mm of free time, all were effectively
ventilated without resorting to tracheostomy or
phrenic nerve pacemakers. The absence of tracheos-
tomy permitted 19 of these patients to sufficiently
master GPB to significanfly increase their free time
off ventilatory support, thus freeing them of the fear
of ventilator failure or disconnection. Indeed, one
patient with no measurable VC who has been using
an IAPV for daytime aid since 1962 and a chest shell
for overnight aid for 25 years experienced sudden
equipment failure during sleep on two occasions and
awoke GPB before he realized that his ventilator was
no longer functioning. Since the IAPV girdle is placed
under the patient’s outer clothing, it is inconspicuous,
and unlike the use of mouth IPPV, it frees the patient
for mouth stick activities. The IAPV supplements the
patient’s own tidal volumes and it is ideal for concur-
rent GPB. It is for these reasons that, when effective,
the IAPV is the preferred method oflong-term nonin-
vasive mechanical assistance in the sitting position. It
should not, however, be used for 24-hour aid because
of the risk of developing sacral decubiti and the fact
that it does not permit the comfort and physiologic
effects of reclining.
ACKNOWLEDGMENTS: The authors wish to thank Lou Saporito,
R.R.T ,and Ira Holland for their assistance with this work.
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DOI 10.1378/chest.99.3.630
1991;99; 630-636Chest
J R Bach and A S Alba
ventilatory support.
Intermittent abdominal pressure ventilator in a regimen of noninvasive
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