Re-engineering ventilatory support to decrease days and improve resource utilization

AmbuBox: A Fast-Deployable Low-Cost Ventilator for COVID-19 Emergent Care

We present a low-cost clinically viable ventilator design, AmbuBox, using a controllable pneumatic enclosure and standard manual resuscitators that are readily available (AmbuBag), which can be rapidly deployed during pandemic and mass-casualty events with a minimal set of components to manufacture and assemble. The AmbuBox is designed to address the existing challenges presented in the existing low-cost ventilator designs by offering an easy-to-install and simple-to-operate apparatus while maintaining a long lifespan with high-precision flow control. As an outcome, a mass-producible prototype of the AmbuBox has been devised, characterized, and validated in a bench test setup using a lung simulator. This prototype will be further investigated through clinical testing. Given the potentially urgent need for inexpensive and rapidly deployable ventilators globally, the overall design, operational principle, and device characterization of the AmbuBox system have been described in detail with open access online. Moreover, the fabrication and assembly methods have been incorporated to enable short-term producibility by a generic local manufacturing facility. In addition, a full list of all components used in the AmbuBox has been included to reflect its low-cost nature.

Ventilator advisory system employing load and tolerance strategy recommends appropriate pressure support ventilation settings: multisite validation study

BACKGROUND

Loads on the respiratory muscles, reflected by noninvasive measurement of the real-time power of breathing (POBn), and tolerance of these loads, reflected by spontaneous breathing frequency (f) and tidal volume (Vt), should be considered when evaluating patients with respiratory failure. Pressure support ventilation (PSV) should be applied so that muscle loads are not too high or too low. We propose a computerized, ventilator advisory system employing a load (POBn) and tolerance (f and Vt) strategy in a fuzzy logic algorithm to provide guidance for setting PSV. To validate these recommendations, we performed a multisite study comparing the advisory system recommendations to experienced physician decisions.

METHODS

Data were obtained from adults who were receiving PSV (n = 87) at three university sites via a combined pressure/flow sensor, which was positioned between the endotracheal tube and the Y-piece of the ventilator breathing circuit and was directed to the advisory system. Recommendations from the advisory system for increasing, maintaining, or decreasing PSV were compared at specific time points to decisions made by physician intensivists at the bedside.

RESULTS

There were no significant differences in the recommendations by the advisory system (n = 210) compared to those of the physician intensivists to increase, maintain, or decrease PSV (p > 0.05). Physician intensivists agreed with 90.5% of all recommendations. The advisory system was very good at predicting intensivist decisions (r(2) = 0.90; p < 0.05) in setting PSV.

CONCLUSIONS

The novel load-and-tolerance strategy of the advisory system provided automatic and valid recommendations for setting PSV to appropriately unload the respiratory muscles that were as good as the clinical judgment of physician intensivists.

Power of breathing determined noninvasively with use of an artificial neural network in patients with respiratory failure

OBJECTIVE

To determine work of breathing per minute or power of breathing noninvasively (POB(N)) by using an artificial neural network (ANN) without the need for an esophageal catheter in patients with respiratory failure.

DESIGN

Prospective study comparing the relationship between POB(N) and invasively measured power of breathing (POB(I)).

SETTING

Intensive care unit of a university hospital.

PATIENTS

Forty-five intubated adults (age, 51 +/- 11 yrs; weight, 71 +/- 18 kg; 28 males and 17 females) receiving pressure support ventilation (PSV).

INTERVENTIONS

Data from an esophageal catheter and airway pressure/flow sensor were used to measure POB(I). A pretrained ANN provided real time calculation of POB(N). POB(I) and POB(N) were measured at various levels of PSV, ranging from 5 to 25 cm H(2)O.

MEASUREMENTS AND MAIN RESULTS

POB(N) was highly correlated with POB(I) (r = 0.91; p < .002), and because POB(N) explained or predicted 83% of the variance in POB(I), it was considered a very good predictor (r(2) = 0.83; p < .002). Bias was negligible (0.00) and precision was clinically acceptable (2.2 J/min).

CONCLUSIONS

POB can be calculated noninvasively with reasonable clinical accuracy for patients receiving ventilatory support by using an ANN. This method obviates the need for inserting an esophageal catheter and thus greatly simplifies measurement of POB. POB(N) may be a clinically useful tool for consideration when setting PSV to unload the respiratory muscles. Before considering its use in clinical practice, POB(N) would need to be incorporated within the context of load tolerance and shown to improve outcomes.

Ventilator Y-Piece Pressure Compared with Intratracheal Airway Pressure in Healthy Intubated Children

OBJECTIVE

Compare airway pressure measurements at the ventilator Y-piece of the breathing circuit (P( Y )) to intratracheal pressure measured at the distal end (P( T )) of the endotracheal tube (ETT) during mechanical ventilation and spontaneous breathing of intubated children.

METHODS

Thirty children (age range 29 days to 5 years) receiving general anesthesia were intubated with an ETT incorporating a lumen embedded in its sidewall that opened at the distal end to measure P( T ). Peak inflation pressure (PIP) was measured at P( Y ) and P( T ) during positive pressure ventilation. Just before extubation, all measurements were repeated and imposed resistive work of breathing (WOBi) was calculated at both sites while breathing spontaneously.

RESULTS

Average PIP was approximately 25% greater at P( Y ) (19.7 +/- 3.4 cm H(2)O) vs. P( T ) (15.0 +/- 2.9 cm H(2)O), p < 0.01. During spontaneous inhalation P( T ) was 59% lower ({bond}8.5 +/- 4.0 cm H(2)O) vs. P( Y ) ({bond}3.5 +/- 2.0 cm H(2)O), p < 0.01. WOBi measured at P( Y ) (0.10 +/- 0.02 Joule/L) was 86% less than WOBi measured at P( T ) (0.70 +/- 0.40 Joule/L), p < 0.01.

CONCLUSIONS

In healthy children P( Y ) significantly overestimates PIP in the trachea during positive pressure ventilation and underestimates the intratracheal airway pressure during spontaneous inhalation. During positive pressure ventilation P( T ) better assesses the pressure generated in the airways and lungs compared to P( Y ) because P( T ) also includes the difference in airway pressure across the ETT tube due to resistance. During spontaneous inhalation, P( T ) reflects the series resistance of the ETT and ventilator circuit, while P( Y ) reflects only the resistance of the ventilator circuit, accounting for the smaller decreases in pressure. Additionally, P( Y ) underestimates the total WOBi load on the respiratory muscles. Thus, P( T ) is a more accurate reflection of pulmonary airway pressures than P( Y ) and suggests that it should be incorporated into ventilator systems to more accurately trigger the ventilator and to reduce work of breathing.

Intratracheal pressure: a more accurate reflection of pulmonary airway pressure in pediatric patients with respiratory failure

OBJECTIVES

Peak inflation pressure (PIP) on many ventilators (P(vent)), measured distal to the exhalation limb or Y-piece of the breathing circuit, is assumed as the pressure applied to the airways and lungs. However, in vitro studies show P(vent) data are spurious. There are no studies evaluating the accuracy of P(vent) data for pediatric patients with acute respiratory failure. We hypothesized that intratracheal airway pressure (P(T)) is more accurate than P(vent) and that by using P(vent), abnormally increased imposed resistive work of breathing (WOBi) may go undetected.

DESIGN

Prospective and descriptive study.

SETTING

A pediatric intensive care unit at a university hospital.

PATIENTS

Twenty-one pediatric patients with respiratory failure requiring mechanical ventilation.

INTERVENTIONS

All patients were intubated with a commercially available endotracheal tube (ETT) with a pressure measuring the lumen opening at the distal end used for measuring P(T). Pressure/flow sensors positioned between the ETT and Y-piece measured tidal volume (V(T)) and flow rate. P(vent) data were recorded as displayed on the ventilator. WOBi was measured by integrating P(T) and V(T) data.

RESULTS

PIP at P(vent) and P(T) were 26 +/- 8 cm H(2)O and 19 +/- 7 cm H(2)O, respectively (p < .05). P(T) measurements averaged 27% less than P(vent). The relationship between P(vent)-P(T) (pressure drop across the breathing circuit and ETT) and flow rate during spontaneous inhalation was highly correlated (r = .80, p < .002), indicating the greater the flow rate, the greater the pressure drop and WOBi. WOBi, ranging from 0.04-1.5 J/L, was measured in 52% of the patients.

CONCLUSIONS

P(vent) significantly overestimates PIP. Moreover, P(vent) data does not allow for recognition of increased WOBi for many patients. Clinicians need to be aware of the limitations of P(vent) data and consider using ETTs that allow measurement of P(T), a more accurate reflection of pulmonary airway pressure.

Flow triggering added to pressure support ventilation improves comfort and reduces work of breathing in mechanically ventilated patients

PURPOSE

The purpose of this study was to measure the effect of flow triggering (FT), added to pressure support ventilation (PSV), during spontaneous breathing in intubated patients.

MATERIALS AND METHODS

A prospective observational study was conducted at a Comprehensive Cancer Center, University Hospital. Fourteen consecutive critically ill, mechanically ventilated patients on PSV with positive end-expiratory pressure were studied. Flow triggering was added to PSV in spontaneously breathing ventilated patients.

RESULTS

Respiratory rate (f), minute ventilation (Vepsilon), patient work of breathing (WOBp), respiratory drive (P0.1), rapid shallow breathing index (f/Vt), tidal volume (Vt) and a visual analog scale of breathing effort and comfort all improved. There was a large decrease in WOBp and P0.1 when flow triggering was added to PSV (P<.001). There was a moderate decrease in f/V1 during the same procedure (P<.01). Twelve patients felt subjectively better with the intervention.

CONCLUSIONS

Flow triggering offers an excellent complement to PSV because it improves patient comfort and reduces the magnitude of the inspiratory effort as well as the delay time between inspiratory muscle contraction and gas flow. It augments gas exchange at no metabolic cost to the patient while reducing the work of breathing.

Work of breathing measurement in the critically ill patient

Weaning patients from mechanical ventilation in the intensive care unit can be difficult. In patients requiring prolonged ventilatory support it has been demonstrated that conventional weaning criteria are frequently incorrect. In this group measurement of respiratory work may be of benefit. Until recently, estimation of the work of breathing in patients receiving mechanical ventilation was logistically difficult. The availability of a computerized bedside monitoring device potentially allows easier estimation of the work of breathing at the bedside. The results of preliminary studies utilizing such monitoring are provocative: they highlight the phenomenon of nosocomial respiratory failure and challenge our clinical ability to determine patient workloads and timing of extubation. The potential benefits of work of breathing measurement, in particular the avoidance of respiratory muscle fatigue, earlier extubation, reduced duration of mechanical ventilation, reduction in ICU and hospital length of stay, and most importantly, a reduction in patient morbidity are yet to be demonstrated and concerns still exist about the monitor's accuracy.

Reengineering respiratory support following extubation: avoidance of critical care unit costs

STUDY OBJECTIVE

We prospectively investigated alternative clinical practice strategies for critically ill trauma patients following extubation to evaluate the cost-effectiveness of these maneuvers. The primary change was elimination of the routine use of postextubation supplemental oxygen, with concurrent utilization of noninvasive positive pressure ventilatory support (NPPV) to manage occurrences of postextubation hypoxemia.

DESIGN

Prospective, consecutive accrual of patients undergoing extubation.

SETTING

Trauma ICU in a university hospital.

INTERVENTIONS AND MEASUREMENTS

All patients received mechanical ventilation using pressure support ventilation (PSV) with continuous positive airway pressure (CPAP) as the primary mode. The patients were extubated to room air following a 20-min preextubation trial of 5 cm H(2)O CPAP at FIO(2) of 0.21, and demonstrating a spontaneous respiratory rate </= 38 breaths/min, pH >/= 7.30, PaCO(2) </= 50 mm Hg, and PaO(2) >/= 50 mm Hg. The subgroup of patients who became hypoxemic (pulse oximetric saturation < 88%) within 24 h of extubation were treated with NPPV for up to 48 h duration. Patients who failed NPPV were reintubated. Four hundred fifty-one (84%) patients were successfully extubated to room air. Seventy-two patients (13%) became hypoxemic within 24 h, and NPPV was administered. Fifty-two patients (72% of those who were hypoxemic) responded to NPPV, while 20 patients failed to respond to therapy, were reintubated, and received mechanical ventilation for a mean of 4 days. Thirteen additional patients (2%) were reintubated for reasons other than hypoxemia. The overall reintubation rate for the group (n = 536) was 6.2%; for the postextubation hypoxemic group who failed NPPV, the reintubation rate was 3.7%. The elimination of routine supplemental oxygen via nasal cannula following extubation resulted in a potential direct cost avoidance of $50,006.88 for 451 patient days. Moreover, the 52 patients who were spared reintubation and mechanical ventilation provided an additional potential cost avoidance of $19,740.24 in unused ventilator days per patient.

CONCLUSION

Eliminating the routine use of supplemental oxygen and employing NPPV as a method to prevent reintubation can facilitate a more aggressive, cost-effective strategy for the management of the trauma ICU patient who has been extubated.

Cost reduction and outcome improvement in the intensive care unit

OBJECTIVE

Decreasing reimbursement provided by third-party payors necessitates reduction of costs for providing critical care services. If academic medical centers are to remain viable, methods must be instituted that allow cost reduction through practice change.

METHODS

We used short cycle improvement methodology to rapidly achieve these goals. Short cycle improvement methodology involves identifying the areas for improvement, defining a mechanism to evaluate outcome, initiating an improvement plan on a small number of patients, and repeating the cycle with new adjustments based on outcome. Baseline data on areas for improvement was prospectively collected, and protocols to initiate change were developed and tested by short improvement cycles. Outcomes were evaluated, protocols were modified, and another cycle was performed. This methodology was continued until the desired goals had been achieved. To adjust outcomes for severity of illness, Acute Physiology and Chronic Health Evaluation II methodology was used. Using this methodology, we focused on three areas for improvement. Standing orders for laboratory studies, electrocardiograms, and chest x-ray films were eliminated. Protocols were developed for the appropriate use of sedation, analgesics, and neuromuscular blocking agents. Finally, a protocol for weaning from mechanical ventilation was developed to allow respiratory therapists to proceed through the weaning process, which was ordered by a physician.

RESULTS

Laboratory tests were reduced by 65% (from 510 to 180 tests per day) with an annual cost savings of $21,593. Chest x-ray reduction of 56% resulted in an annual savings of $3,941. There was a 75% reduction in cost of neuromuscular blocking agents. The use of neuromuscular blocking agents resulted in a 75% reduction in drug costs. Ventilator hours were reduced by 35% from 140 to 90 hours. The average length of overall intensive care unit stay was reduced by 1.5 days (5.0 to 3.5 days). The cost per patient day decreased with an annualized cost savings of 4% per patient day. Unexpected outcomes included a reduction in intensive care unit days from 54 days at baseline to 7 days at the 6-month interval. The infection rates for blood stream infections, urinary tract infections, and nosocomial pneumonia were reduced. Using national nosocomial infection data, these rates represented a reduction from the fiftieth percentile to the twenty-fifth percentile for all measured indicators. Acute Physiology and Chronic Health Evaluation II scores were 19.54 at baseline and increased to 21.2 (p = 0.001) at the 6-month interval. Mortality rates were 16.7% at baseline and were 17.6% (p = 0.89) at the 6-month interval.

CONCLUSION

We concluded that utilization of short cycle improvement methodology provided an ongoing method for reducing costs of critical care services in our patient population with no change in mortality.

A prospective, randomized comparison of an in-line heat moisture exchange filter and heated wire humidifiers: rates of ventilator-associated early-onset (community-acquired) or late-onset (hospital-acquired) pneumonia and incidence of endotracheal tube occlusion

PURPOSE

To compare the performance of an in-line heat moisture exchanging filter (HMEF) (Pall BB-100; Pall Corporation; East Hills, NY) to a conventional heated wire humidifier (H-wH) (Marquest Medical Products Inc., Englewood, Colo) in the mechanical ventilator circuit on the incidence of ventilator-associated pneumonia (VAP) and the rate of endotracheal tube occlusion.

METHODS

This report describes a prospective, randomized trial of 280 consecutive trauma patients in a 20-bed trauma ICU (TICU). All intubated patients not ventilated elsewhere in the medical center prior to their TICU admission were randomized to either an in-line HMEF or a H-wH in the breathing circuit. Ventilator circuits were changed routinely every 7 days, and closed system suction catheters were changed every 3 days. HMEFs were changed every 24 h, or more frequently if necessary. A specific endotracheal tube suction and lavage protocol was not employed. Patients were dropped from the HMEF group if the filter was changed more than three times a day or the patient was placed on a regimen of ultra high-frequency ventilation. The Centers for Disease Control and Prevention (CDC) criteria for diagnosis of pneumonia were used; early-onset, community-acquired pneumonia was defined if CDC criteria were met in < or =3 days, and late-onset, hospital-acquired pneumonia was defined if criteria were met in >3 days. Laboratory and chest radiograph interpretation were blinded.

RESULTS

The patient ages ranged from 15 to 95 years in the HMEF group and 16 to 87 years in the H-wH group (p=not significant), with a mean age of 46 years and 48 years, respectively. The male to female ratio ranged between 78 to 82%/22 to 18%, respectively, and 55% of all admissions were related to blunt trauma, 40% secondary to penetrating trauma, and 5% to major burns. There was no difference in Injury Severity Score (ISS) between the two groups. Moreover, there was no significant difference in mean ISS among those who did not develop pneumonia and those patients who developed either early-onset, community-acquired or late-onset, hospital-acquired pneumonia. The HMEF nosocomial VAP rate was 6% compared to 16% for the H-wH group (p<0.05), and total ventilator circuit costs (per group) were reduced. There were no differences in duration of ventilation (mean+/-SD) if the patient did not develop pneumonia or if the patient developed an early-onset, community-acquired or a late-onset, hospital-acquired pneumonia. Moreover, total TICU days were reduced in the HMEF group. In addition, the incidence of partial endotracheal tube occlusion was not significantly different between the H-wH and the HMEF groups.

CONCLUSIONS

The HMEF used in this study reduced the incidence of late-onset, hospital-acquired VAP, but not early-onset, community-acquired VAP, compared to the conventional H-wH circuit. This was associated with a significant reduction in total ICU stay. Disposable ventilator circuit costs in the HMEF group were reduced compared to the H-wH group in whom circuit changes occurred at 7-day intervals.

CLINICAL IMPLICATIONS

The use of the HMEF is a cost-effective clinical practice associated with fewer late-onset, hospital-acquired VAPs, and should result in improved resource allocation and utilization.