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COPD and Other Diseases in Chronically Ventilated Patients in a Prolonged Respiratory Care Unit
COPD and Other Diseases in Chronically Ventilated Patients in a Prolonged Respiratory Care Unit* A Retrospective 20-Year Survival Study John Votto, DO, FCCP; Janet M. Brancifort, RRT; Paul J. Scalise, MD, FCCP; Christine M. Wollschlager, MD, FCCP; and Richard L. ZuWallack, MD Objectives: To evaluate the long-term prognosis of ventilator-dependent patients. Design: Retrospective study. Setting: A prolonged respiratory care unit (PRCU). The PRCU provides comprehensive medical, nursing, and respiratory care to tracheostomized, ventilator-dependent adult patients who had failed all attempts at weaning. Recause of their medical complexity, these patients could not be discharged to a lower level of care. Patients: Of the 293 patients admitted to the PRCU over a 20-year period beginning January 1, 1977, 145 had respiratory failure from COPD, 22 from spinal cord disease or trauma, 34 from primary CNS disease, 50 from primary neuromuscular disease, and 16 from chest wall disease. Twenty-six patients were not classifiable into the above categories. Measurements: Demographics, diagnoses, and survival data were reviewed. The survival of patients with COPD was compared with the other diagnosis categories using the Cox proportional hazards model. Results: The median survival for the entire group was 9 months; younger age and female gender were both predictive of longer survival (both, p< 0.001). The median survival of those with COPD (5 months) was significantly shorter than that of patients with spinal cord disease (47 months), neuromuscular disease (17 months), and chest wall disease (27 months) (all, p<0.01). These differences in survival were present even with inclusion of gender and age in the model as covariates. The survival of patients with CNS disease was not significantly different from survival of patients with COPD. Conclusion: Chronically ventilated patients with respiratory failure from COPD have a signifi¬ cantly worse prognosis than patients with respiratory failure from other causes. (CHEST 1998; 113:86-90)
Key words: chronically ventilated; COPD; respiratory failure Abbreviations: ALS amyotrophic lateral sclerosis; PRCU=prolonged respiratory care unit =
Tn 1990, an estimated 11,700 individuals in the United States required daily mechanical ventilator support via tracheostomy, with an estimated yearly cost of $3 billion.1 Approximately two thirds of these patients have COPD as a cause for respiratory failure.2 The Prolonged Respiratory Care Unit (PRCU) at the Hospital for Special Care has been treating patients with long-term ventilator dependency since 1977. Causes of respiratory failure include COPD, A
*From the Hospital for Special Care, New Britain, Conn, and the University of Connecticut School of Medicine, Farmington. Manuscript received February 18, 1997; revision accepted June 2. Reprint requests: John J. Votto, DO, FCCP, 2150 Corbin Ave, New Britain, CT 06053
86
spinal cord injury, neuromuscular disease, chest wall disease, and primary CNS disease. Patients admitted to this unit are unweanable and require intensive nursing and respiratory care. Using the Grasp Sys¬ tem to quantify acuity level,3 the mean number of daily patient care hours is approximately 9, which falls between that of medical-surgical ward care (7 to 9 h) and critical care unit (18 h) (personal commu¬ nication; Ruth Brenner, President; Grasp Central Data Center; Boulder, Colo). The
long-term survival of hospitalized, high-acu¬
ity, chronically ventilated patients has received little attention. Since this is a very heterogeneous group with respect to cause of respiratory failure, it pro¬ vides an opportunity to evaluate the relationship
Clinical Investigations
between disease category and prognosis. Therefore,
retrospectively analyzed 20-year of respiratory perience to determine if the failure, in particular COPD, was predictive of dura¬ tion of survival in these patients. our cause
we
MATERIALS
AND
PRCU
ex¬
METHODS
The medical records of patients admitted to the PRCU over the 20-year period beginning January 1, 1977, were reviewed for demographic variables, diagnoses, and survival data. The PRCUto respiratory care provides comprehensive medical, nursing, andfailed all attempts at adult ventilator-dependent patients who had weaning. Varied causes of chronic respiratory failure, such as COPD, chest wall disease, primary neuromuscular disease, spinal cord trauma, and CNS disease are typically followed in the PRCU.
Almost all patients were referred to the unit from an acute-care
General hospital, usually following a lengthy hospitalization.a tracheos¬ admission include the for (1) following: guidelines tomy; (2) failure in all attempts at weaning; (3) mechanical ventilatory support required for >2 months; and (4) medical complexity and/or inadequate social support precluding home
mechanical ventilation. Median survival estimates and survival curves were determined using the Lifetest method.4 Separate survival analyses comparing COPD with each of the diagnosis categories were made using Cox proportional hazards model.5 For each of these analyses, a dummy variable was created for diagnosis category, and age and gender were added to the model in a forward stepwise fashion. A p<0.05 was considered significant.
Results Patients
Records from 293 ventilator-dependent patients aged 16 years and older during this period were available for analysis. Diagnostic categories, which are given in Table 1, included COPD (n=145), quadriplegia from spinal cord disease (n=22), pri¬ mary CNS disease (n=34), neuromuscular disease (n=50), and chest wall disease (n=16). Quadriplegia was posttraumatic in 19 of the 22 cases. Primary CNS diseases included cerebrovascular accidents in 17, anoxic brain disease in eight, traumatic brain injury in eight, and encephalopathy in one. Neuro¬ muscular diseases included amyotrophic lateral scle¬ rosis (ALS) in 28, primary muscular disease in 17,
and other neuropathies in five. Seven patients had both chest wall disease and COPD; these were classified in the chest wall disease category. Twenty-six patients (8.9% of the total group) had not classifiable into the listed principalanddiagnoses had numbers too small to be statistically groups tested as separate groups. This included renal dis¬ ease with congestive heart failure (eight patients), cancer (eight patients), interstitial disease (five pa¬ tients), and miscellaneous conditions (five patients). The age of COPD patients (70±9 years) was not significantly different from patients with chest wall disease (64±16 years), but was significantly greater than that of patients with neuromuscular disease (60±15 years, p<0.05), primary CNS diseases (55±19 years, p<0.01), or quadriplegia (45±16
years,
p<0.0001).
Sixty percent of COPD patients and 62% of chest wall disease patients were female. In contrast, only 23% of patients with spinal cord disease were fe¬ male. Neuromuscular disease and CNS disease, each with 44% female patients, fell between these ex¬ tremes.
Survival Analysis The median survival for the entire group was 9 months (95% confidence interval, 6 to 17 months). Younger age and female gender were both predictive of longer survival (both, p<0.001). The median survivals for each diagnosis category are given in Table 2, and survival curves for a 5-year period are given in Figure 1. Since age and gender were both of survival for the entire group and were predictive not evenly distributed among each category, a pro¬ portional hazards model that included these two variables as covariates was used in this survival
analysis. The median survival of COPD patients, which was 5 months, was significantly shorter than that of patients with spinal cord disease (47 months, Fig 1, neuromuscular disease top left),
Table 2.Survival by Diagnosis
Diagnostic Category
COPD
COPD
Spinal cord disease
CNS disease
Neuromuscular disease Chest wall disease
No.
Age, yr, mean±SD
Male/Female
145 22
70±09 45 ±16 55±19 60 ±15 64 ±16
58/87 17/5 19/15 28/22 6/10
34 50 16
Category*
Survival, mo
Diagnostic Category Table 1.Patient Characteristics
(17 months,
Spinal cord disease
CNS disease
Median
95% CI
Valuef
5 47 5 17 27
3-7 21-153 2-44 13-26 9-110
0.0035 NS 0.0077 0.0029
Neuromuscular disease Chest wall disease *CI=confidence interval; NS=not significant. f After adjustment for gender and age, Cox proportional hazards model, p represents comparison with median survival of patients with COPD. CHEST / 113 / 1 / JANUARY, 1998
87
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Spinal Cord
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>
Diseases
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3
CO
.2
C o
o a o
o
s~
o
a
u
24
36
60
Months in PRCU
Neuromuscular Diseases
12
24
36
48
60
36
48
60
Months in PRCU
wo c
WD G
V*
CO
CO
.2 ".+3
o
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12
24
36
Months in PRCU
48
60
12
24
Months in PRCU
Figure 1. The survival of ventilator-dependent patients: COPD vs other causes of respiratory failure. Lifetable analysis was used to provide survival estimates over a 5-year period beginning with admission to the PRCU. COPD survival is plotted along with spinal cord disease (top left), neuromuscular disease (top right), chest wall disease (bottom left), and CNS disease (bottom right).
88
Clinical
Investigations
Fig 1, top right) and chest wall disease (27 months, Fig 1, bottom left). As indicated by the individual
curves, these survival differences appeared early and remained throughout the period. These differences in survival among the groups were present even with age and gender included in the model as covariates. Survival of patients with primary CNS diseases was virtually identical to COPD patients during most of the first year, but tended to plateau for the remain¬ der of the period while survival of COPD patients decreased steadily (Fig 1, bottom right).
Discussion
hospitalized patients requiring ventilator therapy via tracheostomy, those long-term with COPD as the cause for respiratory failure had the worst long-term prognosis. The median survival for COPD patients was 5 months, compared to 47 months for patients with spinal cord disease, 27 months for with chest In this group of
wall disease, and 17 patients months for patients with neuromuscular disease. Survival for patients with CNS disease was similar to survival for patients with COPD during the first 8 months of hospitalization. Following this initial pe¬ riod, however, CNS survival tended to plateau while COPD survival continued to decline steadily. Al¬ though patients with COPD were older than those with respiratory failure from neurologic causes, the unfavorable prognosis of COPD patients remained even with the inclusion of age in the model. The relatively poor prognosis of COPD patients requiring ventilator support via tracheostomy has been re¬ ported by Robert et al,6 who found that patients with chronic airflow obstruction had a shorter actuarial survival than patients with chronic respiratory failure from other causes. Since adequate documentation from the referring hospital was often lacking from our chart review, the included only the period beginning on the analysis of arrival to the PRCU. Because of this, the day of ventilator period dependency during the shortterm hospitalization, which was often several months in duration, could not be analyzed. Thus, the number of patients in each disease category who died, were successfully weaned, or were discharged home with
noninvasive ventilatory support or mechanical venti¬ lation before transfer to our facility is unknown. The ability to generalize these results to all chron¬ ically ventilated patients is limited since this was a very select group of patients who required highacuity hospital care. In other series,3' 710 a consider¬ able proportion was either weaned off the respirator or sent home with respirator support. For example, the survival of COPD patients receiving mechanical
ventilation via tracheostomy has recently been eval¬ uated in a 5-year retrospective multicenter study in France.3 The 2-year actuarial survival of their pa¬ tients was 70%. In contrast,
only approximately 50%
of our COPD patients were alive at 2 years. How¬ ever, despite similarities with respect to the length of ventilator support before analysis and requirement for tracheostomy, only 16% required a permanent hospitalization in a long-stay unit. This subset, which was not separately analyzed, is probably closer in
severity to our patients. The survival for our patients with spinal cord injury, which was approximately 70% at 1 year (Fig 1,
substantially higher than that de¬ right), awasmulticenter study of 435 ventilatordependent spinal cord-injured patients recently pub¬ lished.11 The overall 1-year survival in this study was 16.8%. This survival difference probably reflects the inclusion of all patients surviving the first 24 h in the multicenter study. Following a steep drop-off during the first year, survival appeared to plateau in a similar fashion to our data.
top
scribed in
The one-year survival of ALS patients has been reportedALSto range from 24% to 85%.12 In our series, patients comprised 58% of the neuro¬ muscular group. The latter group had a median survival of 17 months. Patients with respiratory failure from CNS causes had a very similar survival pattern as those with COPD during the first 8 months of hospitalization. However, following this initial period, the survival curve for CNS patients tended to plateau while for COPD patients it continued to decline steadily. In summary, this 20-year retrospective study rep¬ resents the first survival analysis of high-acuity pa¬ tients requiring long-term ventilator support via tracheostomy. The survival of patients with COPD was significantly shorter than that of patients with respiratory failure due to other causes. This differ¬ ence in survival could not be explained by betweengroup differences in age or gender. References
1 American Association for Respiratory Care and the Gallup Organization. A study of chronic ventilator patients in the Dallas: American Association for Respiratory Care, hospital. 1991 2 Indihar FJ. A 10-year report of patients in a prolonged respiratory care unit. Minn Med 1991; 74:23-27 3 Meyer D. Costing nursing care with the Grasp system: costing out nursing: pricing our product. New York: National League for Nursing, 1985; 55-67 4 SAS users' guide: statistics, version 6, 4th edition: the Lifetest procedure. Cary, NC: SAS Institute, 1990; 1027-69 5 SAS Technical Report P-229: chapter 19: the PHREG pro¬ cedure, Cary, NC: SAS Institute, 1992; 433-80 6 Robert D, Gerard M, Leger P, et al. La ventilation mecanique CHEST / 113 / 1 / JANUARY, 1998
89
domicile definitive par tracheotomie de Finsuffisant respichronique. Rev Fr Mai Respir 1983; 11:923-36 7 Make BJ. Long-term management of ventilator-assisted indi¬ viduals: the Boston University experience. Respir Care 1996; a
ratoire
31:303-10 8 Adams AB, Whitman J, Marcy T. Surveys of long-term ventilatory support in Minnesota: 1986 and 1992. Chest 1993; 103:1463-69 9 Scheinhorn DJ, Artinian BM, Catlin JL. Weaning from
90
prolonged mechanical ventilation: the experience at a re¬ gional weaning center. Chest 1994; 105:534-39 10 Gracey DR, Naessens JM, Viggiano RW, et al. Outcome of patients cared for in a ventilator-dependent unit in a general hospital. Chest 1995; 107:494-99 11 DeVivo MJ, Ivie CS. Life expectancy of ventilator-dependent persons with spinal cord injuries. Chest 1995; 108:226-32 12 Oppenheimer EA. Amyotrophic lateral sclerosis. Eur Respir Rev 10:323-29 1992;
Clinical
Investigations
Key words: chronically ventilated; COPD; respiratory failure Abbreviations: ALS amyotrophic lateral sclerosis; PRCU=prolonged respiratory care unit =
Tn 1990, an estimated 11,700 individuals in the United States required daily mechanical ventilator support via tracheostomy, with an estimated yearly cost of $3 billion.1 Approximately two thirds of these patients have COPD as a cause for respiratory failure.2 The Prolonged Respiratory Care Unit (PRCU) at the Hospital for Special Care has been treating patients with long-term ventilator dependency since 1977. Causes of respiratory failure include COPD, A
*From the Hospital for Special Care, New Britain, Conn, and the University of Connecticut School of Medicine, Farmington. Manuscript received February 18, 1997; revision accepted June 2. Reprint requests: John J. Votto, DO, FCCP, 2150 Corbin Ave, New Britain, CT 06053
86
spinal cord injury, neuromuscular disease, chest wall disease, and primary CNS disease. Patients admitted to this unit are unweanable and require intensive nursing and respiratory care. Using the Grasp Sys¬ tem to quantify acuity level,3 the mean number of daily patient care hours is approximately 9, which falls between that of medical-surgical ward care (7 to 9 h) and critical care unit (18 h) (personal commu¬ nication; Ruth Brenner, President; Grasp Central Data Center; Boulder, Colo). The
long-term survival of hospitalized, high-acu¬
ity, chronically ventilated patients has received little attention. Since this is a very heterogeneous group with respect to cause of respiratory failure, it pro¬ vides an opportunity to evaluate the relationship
Clinical Investigations
between disease category and prognosis. Therefore,
retrospectively analyzed 20-year of respiratory perience to determine if the failure, in particular COPD, was predictive of dura¬ tion of survival in these patients. our cause
we
MATERIALS
AND
PRCU
ex¬
METHODS
The medical records of patients admitted to the PRCU over the 20-year period beginning January 1, 1977, were reviewed for demographic variables, diagnoses, and survival data. The PRCUto respiratory care provides comprehensive medical, nursing, andfailed all attempts at adult ventilator-dependent patients who had weaning. Varied causes of chronic respiratory failure, such as COPD, chest wall disease, primary neuromuscular disease, spinal cord trauma, and CNS disease are typically followed in the PRCU.
Almost all patients were referred to the unit from an acute-care
General hospital, usually following a lengthy hospitalization.a tracheos¬ admission include the for (1) following: guidelines tomy; (2) failure in all attempts at weaning; (3) mechanical ventilatory support required for >2 months; and (4) medical complexity and/or inadequate social support precluding home
mechanical ventilation. Median survival estimates and survival curves were determined using the Lifetest method.4 Separate survival analyses comparing COPD with each of the diagnosis categories were made using Cox proportional hazards model.5 For each of these analyses, a dummy variable was created for diagnosis category, and age and gender were added to the model in a forward stepwise fashion. A p<0.05 was considered significant.
Results Patients
Records from 293 ventilator-dependent patients aged 16 years and older during this period were available for analysis. Diagnostic categories, which are given in Table 1, included COPD (n=145), quadriplegia from spinal cord disease (n=22), pri¬ mary CNS disease (n=34), neuromuscular disease (n=50), and chest wall disease (n=16). Quadriplegia was posttraumatic in 19 of the 22 cases. Primary CNS diseases included cerebrovascular accidents in 17, anoxic brain disease in eight, traumatic brain injury in eight, and encephalopathy in one. Neuro¬ muscular diseases included amyotrophic lateral scle¬ rosis (ALS) in 28, primary muscular disease in 17,
and other neuropathies in five. Seven patients had both chest wall disease and COPD; these were classified in the chest wall disease category. Twenty-six patients (8.9% of the total group) had not classifiable into the listed principalanddiagnoses had numbers too small to be statistically groups tested as separate groups. This included renal dis¬ ease with congestive heart failure (eight patients), cancer (eight patients), interstitial disease (five pa¬ tients), and miscellaneous conditions (five patients). The age of COPD patients (70±9 years) was not significantly different from patients with chest wall disease (64±16 years), but was significantly greater than that of patients with neuromuscular disease (60±15 years, p<0.05), primary CNS diseases (55±19 years, p<0.01), or quadriplegia (45±16
years,
p<0.0001).
Sixty percent of COPD patients and 62% of chest wall disease patients were female. In contrast, only 23% of patients with spinal cord disease were fe¬ male. Neuromuscular disease and CNS disease, each with 44% female patients, fell between these ex¬ tremes.
Survival Analysis The median survival for the entire group was 9 months (95% confidence interval, 6 to 17 months). Younger age and female gender were both predictive of longer survival (both, p<0.001). The median survivals for each diagnosis category are given in Table 2, and survival curves for a 5-year period are given in Figure 1. Since age and gender were both of survival for the entire group and were predictive not evenly distributed among each category, a pro¬ portional hazards model that included these two variables as covariates was used in this survival
analysis. The median survival of COPD patients, which was 5 months, was significantly shorter than that of patients with spinal cord disease (47 months, Fig 1, neuromuscular disease top left),
Table 2.Survival by Diagnosis
Diagnostic Category
COPD
COPD
Spinal cord disease
CNS disease
Neuromuscular disease Chest wall disease
No.
Age, yr, mean±SD
Male/Female
145 22
70±09 45 ±16 55±19 60 ±15 64 ±16
58/87 17/5 19/15 28/22 6/10
34 50 16
Category*
Survival, mo
Diagnostic Category Table 1.Patient Characteristics
(17 months,
Spinal cord disease
CNS disease
Median
95% CI
Valuef
5 47 5 17 27
3-7 21-153 2-44 13-26 9-110
0.0035 NS 0.0077 0.0029
Neuromuscular disease Chest wall disease *CI=confidence interval; NS=not significant. f After adjustment for gender and age, Cox proportional hazards model, p represents comparison with median survival of patients with COPD. CHEST / 113 / 1 / JANUARY, 1998
87
C
Spinal Cord
>
>
Diseases
u
C/5 G
3
CO
.2
C o
o a o
o
s~
o
a
u
24
36
60
Months in PRCU
Neuromuscular Diseases
12
24
36
48
60
36
48
60
Months in PRCU
wo c
WD G
V*
CO
CO
.2 ".+3
o
c
c
o
o a. o
a ©
Ph
12
24
36
Months in PRCU
48
60
12
24
Months in PRCU
Figure 1. The survival of ventilator-dependent patients: COPD vs other causes of respiratory failure. Lifetable analysis was used to provide survival estimates over a 5-year period beginning with admission to the PRCU. COPD survival is plotted along with spinal cord disease (top left), neuromuscular disease (top right), chest wall disease (bottom left), and CNS disease (bottom right).
88
Clinical
Investigations
Fig 1, top right) and chest wall disease (27 months, Fig 1, bottom left). As indicated by the individual
curves, these survival differences appeared early and remained throughout the period. These differences in survival among the groups were present even with age and gender included in the model as covariates. Survival of patients with primary CNS diseases was virtually identical to COPD patients during most of the first year, but tended to plateau for the remain¬ der of the period while survival of COPD patients decreased steadily (Fig 1, bottom right).
Discussion
hospitalized patients requiring ventilator therapy via tracheostomy, those long-term with COPD as the cause for respiratory failure had the worst long-term prognosis. The median survival for COPD patients was 5 months, compared to 47 months for patients with spinal cord disease, 27 months for with chest In this group of
wall disease, and 17 patients months for patients with neuromuscular disease. Survival for patients with CNS disease was similar to survival for patients with COPD during the first 8 months of hospitalization. Following this initial pe¬ riod, however, CNS survival tended to plateau while COPD survival continued to decline steadily. Al¬ though patients with COPD were older than those with respiratory failure from neurologic causes, the unfavorable prognosis of COPD patients remained even with the inclusion of age in the model. The relatively poor prognosis of COPD patients requiring ventilator support via tracheostomy has been re¬ ported by Robert et al,6 who found that patients with chronic airflow obstruction had a shorter actuarial survival than patients with chronic respiratory failure from other causes. Since adequate documentation from the referring hospital was often lacking from our chart review, the included only the period beginning on the analysis of arrival to the PRCU. Because of this, the day of ventilator period dependency during the shortterm hospitalization, which was often several months in duration, could not be analyzed. Thus, the number of patients in each disease category who died, were successfully weaned, or were discharged home with
noninvasive ventilatory support or mechanical venti¬ lation before transfer to our facility is unknown. The ability to generalize these results to all chron¬ ically ventilated patients is limited since this was a very select group of patients who required highacuity hospital care. In other series,3' 710 a consider¬ able proportion was either weaned off the respirator or sent home with respirator support. For example, the survival of COPD patients receiving mechanical
ventilation via tracheostomy has recently been eval¬ uated in a 5-year retrospective multicenter study in France.3 The 2-year actuarial survival of their pa¬ tients was 70%. In contrast,
only approximately 50%
of our COPD patients were alive at 2 years. How¬ ever, despite similarities with respect to the length of ventilator support before analysis and requirement for tracheostomy, only 16% required a permanent hospitalization in a long-stay unit. This subset, which was not separately analyzed, is probably closer in
severity to our patients. The survival for our patients with spinal cord injury, which was approximately 70% at 1 year (Fig 1,
substantially higher than that de¬ right), awasmulticenter study of 435 ventilatordependent spinal cord-injured patients recently pub¬ lished.11 The overall 1-year survival in this study was 16.8%. This survival difference probably reflects the inclusion of all patients surviving the first 24 h in the multicenter study. Following a steep drop-off during the first year, survival appeared to plateau in a similar fashion to our data.
top
scribed in
The one-year survival of ALS patients has been reportedALSto range from 24% to 85%.12 In our series, patients comprised 58% of the neuro¬ muscular group. The latter group had a median survival of 17 months. Patients with respiratory failure from CNS causes had a very similar survival pattern as those with COPD during the first 8 months of hospitalization. However, following this initial period, the survival curve for CNS patients tended to plateau while for COPD patients it continued to decline steadily. In summary, this 20-year retrospective study rep¬ resents the first survival analysis of high-acuity pa¬ tients requiring long-term ventilator support via tracheostomy. The survival of patients with COPD was significantly shorter than that of patients with respiratory failure due to other causes. This differ¬ ence in survival could not be explained by betweengroup differences in age or gender. References
1 American Association for Respiratory Care and the Gallup Organization. A study of chronic ventilator patients in the Dallas: American Association for Respiratory Care, hospital. 1991 2 Indihar FJ. A 10-year report of patients in a prolonged respiratory care unit. Minn Med 1991; 74:23-27 3 Meyer D. Costing nursing care with the Grasp system: costing out nursing: pricing our product. New York: National League for Nursing, 1985; 55-67 4 SAS users' guide: statistics, version 6, 4th edition: the Lifetest procedure. Cary, NC: SAS Institute, 1990; 1027-69 5 SAS Technical Report P-229: chapter 19: the PHREG pro¬ cedure, Cary, NC: SAS Institute, 1992; 433-80 6 Robert D, Gerard M, Leger P, et al. La ventilation mecanique CHEST / 113 / 1 / JANUARY, 1998
89
domicile definitive par tracheotomie de Finsuffisant respichronique. Rev Fr Mai Respir 1983; 11:923-36 7 Make BJ. Long-term management of ventilator-assisted indi¬ viduals: the Boston University experience. Respir Care 1996; a
ratoire
31:303-10 8 Adams AB, Whitman J, Marcy T. Surveys of long-term ventilatory support in Minnesota: 1986 and 1992. Chest 1993; 103:1463-69 9 Scheinhorn DJ, Artinian BM, Catlin JL. Weaning from
90
prolonged mechanical ventilation: the experience at a re¬ gional weaning center. Chest 1994; 105:534-39 10 Gracey DR, Naessens JM, Viggiano RW, et al. Outcome of patients cared for in a ventilator-dependent unit in a general hospital. Chest 1995; 107:494-99 11 DeVivo MJ, Ivie CS. Life expectancy of ventilator-dependent persons with spinal cord injuries. Chest 1995; 108:226-32 12 Oppenheimer EA. Amyotrophic lateral sclerosis. Eur Respir Rev 10:323-29 1992;
Clinical
Investigations