Reduction In Work Of Breathing Research Articles

Low Pressure Heliox-based Rebreather System to Reduce Work of Breathing and Conserve Gas.

Background: To test the ability of a low-pressure, low-flow, Heliox-based rebreathing system to reduce work of breathing and conserve gas while preserving CO2 concentration, temperature, and humidity at physiological levels in a bench study.Methods: We performed a bench study of a novel low-pressure, low-flow, noninvasive Heliox rebreathing system with CO2 scrubber that was connected to an artificial lung simulator with careful monitoring of flow, pressure, work of breathing, oxygen (O2), carbon-dioxide (CO2), temperature, and humidity levels. Multiple runs of breathing were performed while manipulating levels of resistance (5 - 30 cm H2O/L/sec), gas mixtures (room air, 79% Helium 21% O2, and 70% Helium and 30% O2), and leak levels (ultra-low, low, and high).Results: We found significant reductions in work of breathing (up to 64%) while conserving gas with estimates of up to 54-fold reduction in medical gas wastage (P<0.001). Specifically, at resistances of 5, 10, 20, and 30 cm H2O/L/sec we demonstrated 64%, 57%, 36%, and 7% reduction in work of breathing (P<0.0001). Gas wastage was reduced by 10- to 54-fold while the end-tidal CO2 concentration, humidity, and temperature were maintained by the device at physiological levels.Conclusions: In a bench-test, a low-pressure, low-flow, noninvasive Heliox rebreathing system with CO2 scrubber reduced work of breathing and conserved gas while preserving CO2 concentration, temperature, and humidity at physiological levels. Future studies in human subjects need to be performed to determine whether reduction of work of breathing and gas conservation can be achieved.

Perioperative use of high flow nasal cannula

High flow nasal cannula (HFNC) is an innovative oxygen therapy system that has gained increasing popularity in recent decades, particularly in the field of critical care medicine. The device provides a more constant and higher FiO2, generates low levels of PEEP, reduces dead space ventilation, and conditions the inspired gas, which collectively results in a reduction in work of breathing (WOB) and improved patient comfort. While the application of HFNC in critically ill patients is well-established and supported by a large body of evidence, studies of HFNC during the perioperative period are limited. However, the working mechanisms of HFNC align with physiological demands across various anesthetic processes. Consequently, this system could potentially serve as an alternative oxygen delivery system for surgical patients during perioperative care. In this article, we summarize the working principles and the effects provided by HFNC, review its implementation during the perioperative period, and discuss the current evidence regarding its use.

Awake prone position reduces work of breathing in patients with COVID-19 ARDS supported by CPAP

BackgroundThe use of awake prone position concomitant to non-invasive mechanical ventilation in acute respiratory distress syndrome (ARDS) secondary to COVID-19 has shown to improve gas exchange, whereas its effect on the work of breathing remain unclear. The objective of this study was to evaluate the effects of awake prone position during helmet continuous positive airway pressure (CPAP) ventilation on inspiratory effort, gas exchange and comfort of breathing.MethodsForty consecutive patients presenting with ARDS due to COVID-19 were prospectively enrolled. Gas exchange, esophageal pressure swing (ΔPes), dynamic transpulmonary pressure (dTPP), modified pressure time product (mPTP), work of breathing (WOB) and comfort of breathing, were recorded on supine position and after 3 h on prone position.ResultsThe median applied PEEP with helmet CPAP was 10 [8–10] cmH2O. The PaO2/FiO2 was higher in prone compared to supine position (Supine: 166 [136–224] mmHg, Prone: 314 [232–398] mmHg, p < 0.001). Respiratory rate and minute ventilation decreased from supine to prone position from 20 [17–24] to 17 [15–19] b/min (p < 0.001) and from 8.6 [7.3–10.6] to 7.7 [6.6–8.6] L/min (p < 0.001), respectively. Prone position did not reduce ΔPes (Supine: − 7 [− 9 to − 5] cmH2O, Prone: − 6 [− 9 to − 5] cmH2O, p = 0.31) and dTPP (Supine: 17 [14–19] cmH2O, Prone: 16 [14–18] cmH2O, p = 0.34). Conversely, mPTP and WOB decreased from 152 [104–197] to 118 [90–150] cmH2O/min (p < 0.001) and from 146 [120–185] to 114 [95–151] cmH2O L/min (p < 0.001), respectively. Twenty-six (65%) patients experienced a reduction in WOB of more than 10%. The overall sensation of dyspnea was lower in prone position (p = 0.005).ConclusionsAwake prone position with helmet CPAP enables a reduction in the work of breathing and an improvement in oxygenation in COVID-19-associated ARDS.

Effect of the measurement of the work of breathing on the respiratory outcome of preterms

Rationale There are no validated criteria for the choice of the optimal type of noninvasive respiratory support (NRS) and most appropriate settings in preterms. Methods The work of breathing (WOB) during oxygen (O2) alone, nasal continuous positive pressure (nCPAP) and high flow nasal cannula (HFNC) was compared in preterm babies (23–30 weeks’ gestation, “physiological group”) needing any type of noninvasive respiratory support (“baseline” NRS) at 4 weeks of life. Babies were thereafter treated with the NRS associated with the greatest reduction in WOB (“optimal NRS”). The respiratory outcome at 36 weeks” gestation of these babies was compared to a “control” group treated with NRS based on standard noninvasive parameters. Preterm babies were prospectively enrolled in 3 centers and randomized into the “physiological” or “control” group. Results Thirty babies were randomized. WOB with “baseline” NRS was higher than the “optimal” NRS and the consequent NRS chosen by physicians (p = 0.001). WOB was lower during HFNC than during O2 (p = 0.032) but WOB was comparable between nCPAP and HFNC, and between nCPAP and O2. Notably, WOB was near to normal during spontaneous breathing with O2. Respiratory outcome at 36 week’ gestation was comparable between the 2 groups. Conclusion The optimization of NRS by means of the measurement of WOB in preterms requiring any type of NRS at 4 weeks of life was able to decrease the WOB but had no effect on the clinical outcome at 36 weeks’ gestation.

Mechanisms of nasal high flow therapy in newborns.

In newborns, it is unclear how nasal high flow (NHF) generates positive airway pressure. In addition, the reported benefits of NHF such as reduction in work of breathing may be independent of airway pressure. The authors hypothesized that during NHF the area of leak and the flow determine airway pressure and that NHF can reduce the required minute ventilation to maintain gas exchange. In response to NHF, pressure was measured in the upper airways of 9 newborns and ventilation was measured in another group of 17 newborns. In a bench model, airway pressures were measured during NHF with different prong sizes, nare sizes, and flows. The airway pressures during 8 L/min NHF were greater when a larger cannula versus a smaller cannula was used (P < 0.05). NHF reduced minute ventilation in 16 of 17 neonates, with a mean decrease of 24% from a baseline of 0.66 L/min (SD 0.21) (P < 0.001), and was unrelated to changes in airway pressure; arterial oxygen saturation by pulse oximetry () and tissue CO2 were unchanged. In the bench model, the airway pressure remained <2 cmH2O when <50% of the “nare” was occluded by the prongs. As the leak area decreased, because of a smaller nare or a larger cannula, the airway pressure increased exponentially and was dependent on flow. In newborns NHF using room air substantially reduced minute ventilation without affecting gas exchange irrespective of a decrease or an increase of respiratory rate. NHF generates low positive airway pressure that exponentially increases with flow and occlusion of the nares.NEW & NOTEWORTHY In healthy newborns, nasal high flow (NHF) with room air reduced minute ventilation by one-fourth without affecting gas exchange but, in contrast to adults, produced variable response in respiratory rate during sleep. During NHF, pressure in the upper airways did not exceed 2 cmH2O at 8 L/min (3.4 L·min−1·kg−1) and was unaffected by opening of the mouth. NHF can generate higher pressure with larger prongs that decrease the leak around the cannula or by increasing the flow rate.

High‐flow nasal therapy – modelling the mechanism

High‐flow nasal therapy – modelling the mechanism

Nasal high-flow therapy reduces work of breathing compared with oxygen during sleep in COPD and smoking controls: a prospective observational study.

Nasal high-flow (NHF) therapy can support ventilation in patients with chronic obstructive pulmonary disease during sleep by decreasing the work of breathing and improving CO2 levels. On the other hand, oxygen supplementation corrects hypoxemia, but it produces only a minimal reduction in work of breathing and is associated with increased CO2 levels. Therefore, NHF can be a useful method to assist ventilation in patients with increased respiratory mechanical loads.

Modeling the effectiveness of nebulized terbutaline for decompensated chronic obstructive pulmonary disease patients in the emergency department.

Short-acting β2-agonists (SABA) are widely used in the emergency department (ED) to treat patients with decompensated chronic obstructive pulmonary disease (COPD). We sought to model the effectiveness of nebulized SABA (terbutaline) on clinically relevant parameters associated with a reduction in work of breathing or respiratory muscle fatigue in decompensated COPD patients admitted to the ED.Forty consecutive decompensated COPD patients (having received at least one dose of nebulized terbutaline during their stay in the ED) were included in an observational cohort study. The terbutaline dose received at time t was expressed as cumulative dose and as a rate (mg/day). The associations between the terbutaline dose and time-dependent outcome parameters (respiratory rate, heart rate, arterial blood gases, and, as a marker of terbutaline's systemic effect, serum potassium) were analyzed using a nonlinear, mixed-effects model. The effect of various covariates influencing terbutaline's effectiveness (baseline characteristics and concomitant treatments) was assessed on the model.Among the investigated patients, a total of 377 time-dependent observations were available for analysis. Neither the cumulative dose nor the dose rate at time t significantly influenced the arterial blood gas parameters or heart rate. The cumulative dose of terbutaline was associated with a lower serum potassium level (P < 0.001) and, less significantly, a lower respiratory frequency (P = 0.036). In a tertile analysis, the need for post-ED hospitalization was not associated with the cumulative dose or dose rate of terbutaline.Overall, the results of our modeling study strongly suggest that terbutaline dose did not influence time-dependent outcomes other than serum potassium, and thus call into question the systematic administration of inhaled SABA to patients admitted to the ED for decompensated COPD.

Effects Of Exercise-induced Respiratory Muscle Work And Hypoxemia On Quadriceps Fatigue In Men Versus Women

Reducing work of breathing (WOB) or eliminating exercise-induced arterial hypoxemia (EIAH) during intense exercise decreases the severity of quadriceps fatigue in men. Women have a greater WOB at any given ventilation during exercise relative to men, dedicate a greater fraction of whole body V[Combining Dot Above]O2 towards their respiratory muscles, and demonstrate EIAH, suggesting women may be more susceptible to quadriceps muscle fatigue. PURPOSE:To determine the extent to which quadriceps fatigue is attenuated when WOB is reduced or EIAH is prevented during exercise in both sexes. METHODS:Six healthy subjects (V[Combining Dot Above]O2max57±2 ml/kg/min; 3 female) completed maximal incremental cycle exercise and 3 time-to-exhaustion (TTE) tests over 4 days. During the first (control) TTE test, subjects exercised at constant work rate (>85% of max work) while temperature-corrected arterial blood gases, cardiorespiratory variables and WOB were assessed. Subsequent TTE tests were iso-time and iso-work rate, but with EIAH prevented by inspiring hyperoxic gas (24-27% O2) or WOB reduced via a proportional assist ventilator (PAV). Locomotor muscle fatigue was assessed by measuring potentiated quadriceps twitch force in response to supramaximal magnetic stimulation of the femoral nerve before and 3 min after exercise. RESULTS:Men exercised at a higher absolute work rate (273±9 vs. 203±12 W,p>.05) as women. During the control TTE (data pooled), nadir arterial oxyhemoglobin saturation (SaO2) was 95±0.4% and pHa was 7.18±0.03. Hyperoxia prevented EIAH in all subjects (SaO2>98%). PAV reduced WOB to 58±6% of control (range 35-75%). Quadriceps twitch force was reduced after the control exercise trial by 26±3% and was significantly attenuated after exercise on the hyperoxia and PAV trials (19±3 and 19±3%, p>.01, respectively). The subject with the largest increase in SaO2 (+9%) with hyperoxia and the greatest reduction in WOB (35% of control) with PAV had the greatest attenuation of locomotor fatigue. CONCLUSIONS:Preventing EIAH and reducing WOB attenuate post-exercise quadriceps fatigue to a similar extent in both sexes. Subjects with the highest WOB or lowest SaO2 during the control trial demonstrated the greatest attenuation of quadriceps fatigue during the PAV and hyperoxic trials. Funding: NSERC

A proportional assist ventilator to unload respiratory muscles experimentally during exercise in humans.

What is the central question of this study? Can a modern proportional assist ventilator (PAV) function sufficiently well to unload the respiratory muscles during exercise? What is the main finding and its importance? A PAV can be constructed with contemporary hardware and software and be used at all exercise intensities to unload the respiratory muscles by up to 70%. Previously, PAVs have allowed researchers to address many fundamental physiological problems in clinical and healthy populations, but those versions are no longer functional or available. We describe the creation of a PAV that permits researchers to use it as an experimental tool. Manipulation of the normally occurring work of breathing (WOB) during exercise can provide insights into whole-body regulatory mechanisms in clinical patients and healthy subjects. One method to reduce the WOB uses a proportional assist ventilator (PAV). Suitable commercially available units are not capable of being used during heavy exercise. This investigation was undertaken in order to create a PAV and assess the degree to which the WOB could be reduced during exercise. A PAV works by creating a positive mouth pressure (Pm ) during inspiration, which consequently reduces the WOB. Spontaneous breathing patterns can be maintained, and the amplitude of Pm is calculated using the equation of motion and predetermined proportionality constants. We generated positive Pm using a breathing apparatus consisting of rigid tubing, solenoid valves to control the airflow direction and a proportional valve connected to compressed gas. Healthy male and female subjects were able to use the PAV successfully while performing cycling exercise over a range of intensities (50-100% of maximal workload) for different durations (from 30s to 20min) and different protocols (constant versus progressive workload). Inspiratory WOB was reduced up to 90%, while total WOB was reduced by 70%. The greatest reduction in WOB (50-75%) occurred during submaximal exercise, but at maximal ventilations (>180lmin(-1) ) a 50% reduction was still possible. The calculated change in WOB and subsequent reduction in respiratory muscle oxygen consumption resulted in equivalent reductions in whole-body oxygen consumption. With adequate familiarization and practice, our PAV can consistently reduce the WOB across a range of exercise intensities.

In vitro study on work of breathing during non-invasive ventilation using a new variable flow generator

ObjectiveIn an attempt to reduce the work of breathing (WOB) and the risk of respiratory failure, preterm infants are increasingly treated with nasal synchronised biphasic positive airway pressure (BPAP) via...

Effets des agents sédatifs sur la demande métabolique

Literature about the effects of sedative drugs on the metabolic demand of critically ill patients is relatively old and of relatively poor quality. Most are experimental or observational studies. Level of evidence is therefore relatively low corresponding to "expert opinion". The effects of analgesics and hypnotics on tissue metabolic demand associated remain difficult to be adequately quantified. They are essentially related to a decreased neuro-humoral response to stress. This response involves principally the sympathetic system, which could be effectively blocked by most of the anesthetic agents. Other factors could participate to the observed reduction in tissue metabolic demand, as a decrease in spontaneous muscular activity, a reduction in work of breathing and/or a decrease in body temperature. The relative contribution of these different factors will depend on the clinical situation of the patient. Proper effects of anesthetic agents on cellular metabolism are limited as they can only decrease the functional component of this metabolism especially at the level of the heart and to some extent, at the level of the brain. Although the control of the sympathetic activity may be beneficial in critically ill patient, complete sympathetic blockade could be detrimental. Indeed, when oxygen transport to the tissues is acutely reduced, the sympathetic system plays an important role in the redistribution of blood flow according of local metabolic demand. The complete blunting of the neuro-humoral response to stress and therefore of the sympathetic system alters this physiological mechanism and results in a decrease in tissue oxygen extraction capabilities. An imbalance between tissue oxygen demand and delivery could appear with the development of cellular hypoxia. The institution of sedation in a critically ill patient requires careful evaluation of the sedation level using an appropriate scale. In patients in whom a reduction in metabolic demand is specifically requested, but also in patients with limited oxygen transport, the effects of sedative agents on the oxygen consumption-oxygen delivery relationship must also be monitored. The choice of the different agents to be administered will depend on the predefined objectives. As far as intravenous agents are concerned, there is no evidence than one association is more efficient in reducing patient's metabolic demand.

Effects of the components of positive airway pressure on work of breathing during bronchospasm.

Partial assist ventilation reduces work of breathing in patients with bronchospasm; however, it is not clear which components of the ventilatory cycle contribute to this process. Theoretically, expiratory positive airway pressure (EPAP), by reducing expiratory breaking, may be as important as inspiratory positive airway pressure (IPAP) in reducing work of breathing during acute bronchospasm. We compared the effects of 10 cmH2O of IPAP, EPAP, and continuous positive airwaypressure (CPAP) on inspiratory work of breathing and end-expiratory lung volume (EELV) in a canine model of methacholine-induced bronchospasm. Methacholine infusion increased airway resistance and work of breathing. During bronchospasm IPAP and CPAP reduced work of breathing primarily through reductions in transdiaphragmatic pressure per tidal volume (from 69.4 +/- 10.8 cmH2O/l to 45.6 +/- 5.9 cmH2O/l and to 36.9 +/- 4.6 cmH2O/l, respectively; P < 0.05) and in diaphragmatic pressure-time product (from 306 +/- 31 to 268 +/- 25 and to 224 +/- 23, respectively; P < 0.05). Pleural pressure indices of work of breathing were not reduced by IPAP and CPAP. EPAP significantly increased all pleural and transdiaphragmatic work of breathing indices. CPAP and EPAP similarly increased EELV above control by 93 +/- 16 ml and 69 +/- 12 ml, respectively. The increase in EELV by IPAP of 48 +/- 8 ml (P < 0.01) was significantly less than that by CPAP and EPAP. The reduction in work of breathing during bronchospasm is primarily induced by the IPAP component, and that for the same reduction in work of breathing by CPAP, EELV increases more.

Dysanaptic growth of conducting airways after pneumonectomy assessed by CT scan.

In immature dogs after pneumonectomy (PNX), pulmonary viscous resistance is persistently elevated predominantly as a result of a high airway resistance (Raw). We examined the anatomical basis for this observation by using computerized tomography scans obtained from foxhounds 4-10 mo after right PNX. Airways of the left lower lobe were followed from generations z = 0 (trachea) to z = 12. By 4 mo post-PNX, airway length increased significantly relative to sham-operated dogs, but airway cross-sectional area (CSA) did not. By 10 mo post-PNX, average airway CSA was 24% above that in controls. Theoretically, the increased airway length and CSA should reduce lobar Raw by 50%. However, post-PNX airway dilatation did not normalize total CSA, and estimated resistance due to turbulence and convective acceleration increased threefold; i.e., the 50% reduction in lobar Raw would be offset by the loss of four of seven lobes. Thus the expected reduction in work of breathing in the whole animal is only ~30%, consistent with previously measured work of breathing in pneumonectomized dogs. We conclude that airway structure adapts slowly and incompletely, resulting in limited functional compensation.

Use of helium-oxygen mixtures to relieve upper airway obstruction in a pediatric population.

Helium as a component of inspired gas decreases turbulent flow and airway resistance. Helium-oxygen mixtures have been used since the 1930s in the management of patients with upper airway obstruction. The objective of this study was to evaluate the efficacy of helium-oxygen mixtures in relieving upper airway obstruction in a pediatric population. Retrospective chart review of 42 pediatric patients who received helium-oxygen mixtures for upper airway obstruction within a 3-year period. The study protocol included 42 pediatric patients, aged 1 week to 14 years, who were admitted to the Children's Hospital of Philadelphia from June 1997 to December 2000 and who received a total of 44 treatments of helium-oxygen therapy for upper airway obstruction. Response to treatment was determined by reduction in work of breathing noted on the chart. Thirty-two of 44 helium-oxygen treatments resulted in a positive response (73%). There were no significant differences in demographic characteristics between responders and nonresponders, except all of the premature infants were responders and 6 of the 9 patients with syndromes were nonresponders. Helium-oxygen therapy is a useful adjunct therapy for upper airway obstruction. Controlled clinical trials are necessary to better define the appropriate settings for use of helium-oxygen.

Ventilatory and hemodynamic effects of continuous positive airway pressure in left heart failure.

The ventilatory and hemodynamic effects of continuous positive airway pressure (CPAP) delivered via a face mask (at 0, 5, and 10 cm H2O, and after a return to 0 cm H2O) were studied in nine patients with acute left heart failure (pulmonary artery occlusion pressure [PAOP] > or = 18 mm Hg, and cardiac index [CI] < or = 2.8 L/min/m2). CPAP at 10 cm H2O induced an improvement in lung compliance (60 +/- 10 ml/cm H2O to 87 +/- 20 ml/cm H2O, p < 0.05) and in lung and airway resistance (5.7 +/- 1.0 cm H2O/L/s to 3.4 +/- 1.0 cm H2O/L/s, p < 0.05), a reduction in work of breathing (18 +/- 3 J/min to 12 +/- 2 J/min, p < 0.05), and in the pressure-time index of the respiratory muscles (279 +/- 22 cm H2O/s/min to 174 +/- 25 cm H2O/s/min, p < 0.05), without significant changes in breathing pattern. Despite a significant reduction in the negative swings in intrathoracic pressure (15.2 +/- 1.9 cm H2O to 10.8 +/- 1.8 cm H2O, p < 0.001), no significant change was observed in CI or stroke volume during CPAP. However, mean transmural filling pressures decreased significantly with CPAP, suggesting a better cardiac performance. Neither the level of stroke volume nor of PAOP, was predictive of changes in CI or in stroke volume. In patients with respiratory insufficiency caused by congestive heart failure (CHF), CPAP reduces respiratory muscle effort without altering cardiac output. The slight decrease in mean transmural left and right atrial pressures suggests an improvement in cardiac performance.

Comparison of Pressure and Flow Triggering Systems During Continuous Positive Airway Pressure

Compare the inspiratory work of breathing (WOBI) during pressure triggering (PT), and flow triggering (FT) using two microprocessor ventilators. A randomized, crossover comparison of triggering strategies and ventilators used. Surgical intensive care unit. Ten patients recovering from acute respiratory failure (eight men, two women; mean age, 48 +/- 12 years) breathing on continuous positive airway pressure (CPAP) of 5 cm H2O were studied. Patients were randomly assigned to either receive 5 cm H2O CPAP via one of two units (Hamilton Veolar or Puritan Bennett 7200ae) using either PT or FT. Each patient had 30-min trials using the following: (1) Veolar FT; (2) Veolar PT; (3) 7200ae FT; and (4) 7200ae FT. During each trial period, work of breathing (WOB) and pressure time product (PTP) were measured using a respiratory monitor (Bi-core CP-100). All patients were placed in semi-Fowler position and esophageal balloons were inserted and their position confirmed using the occlusion technique. Continuous measurements of peak negative pressure during inspiration, tidal volume (VT), minute ventilation (VE), respiratory frequency (f) were accomplished with a flow transducer at the proximal airway. FT with the 7200ae was superior to PT as measured by both the WOB (0.58 +/- 0.3 vs 0.84 +/- 0.2 J/L, p < 0.01) and PTP (148 +/- 50 vs 206 +/- 41 cm H2O/s/min, p, 0.05). FT with the Veolar was also superior to PT with respect to the WOB (0.53 +/- 0.2 vs 0.93 +/- 0.2 J/L, p < 0.01) and PTP (140 +/- 39 vs 229 +/- 46 cm H2O/s/min, p < 0.05). FT reduces the WOB compared with PT, regardless of the ventilator used. The reduction in WOB during FT is related to improved responsiveness and changes in the posttrigger phase.

Home care of chronic respiratory disease

From 1958 to 1967, 148 patients with severe chronic respiratory insufficiency have been managed in a Home Care Program, which has primarily involved concentrated care in the home by nurses and other paramedical personnel, as well as by hospital residents. Therapeutic measures were directed at reduction in work of breathing, an increase in alveolar ventilation and physical activity, and when necessary, provision of mechanical aids. Of the patients, 55% required rehospitalization, but for only 5.7% of the total days on home care. Of the 148 patients, 47% died after they had been on the program for an average of 361 days. The cost of the program was slight, particularly when compared to that of a hospital bed, and the cost of physician care constituted a very small portion of the total cost.

Home Care of Chronic Respiratory Disease

From 1958 to 1967, 148 patients with severe chronic respiratory insufficiency have been managed in a "Home Care Program," which has primarily involved concentrated care in the home by nurses and other paramedical personnel, as well as by hospital residents. Therapeutic measures were directed at reduction in work of breathing, an increase in alveolar ventilation and physical activity, and when necessary, provision of mechanical aids. Of the patients, 55% required rehospitalization, but for only 5.7% of the total days on home care. Of the 148 patients, 47% died after they had been on the program for an average of 361 days. The cost of the program was slight, particularly when compared to that of a hospital bed, and the cost of physician care constituted a very small portion of the total cost.