Bicore CP-100 Research Articles

Effort of Breathing in Children Receiving High-Flow Nasal Cannula

High-flow humidified nasal cannula is often used to provide noninvasive respiratory support in children. The effect of high-flow humidified nasal cannula on effort of breathing in children has not been objectively studied, and the mechanism by which respiratory support is provided remains unclear. This study uses an objective measure of effort of breathing (Pressure. Rate Product) to evaluate high-flow humidified nasal cannula in critically ill children. Prospective cohort study. Quaternary care free-standing academic children's hospital. ICU patients younger than 18 years receiving high-flow humidified nasal cannula or whom the medical team planned to extubate to high-flow humidified nasal cannula within 72 hours of enrollment. An esophageal pressure monitoring catheter was placed to measure pleural pressures via a Bicore CP-100 pulmonary mechanics monitor. Change in pleural pressure (ΔPes) and respiratory rate were measured on high-flow humidified nasal cannula at 2, 5, and 8 L/min. ΔPes and respiratory rate were multiplied to generate the Pressure.Rate Product, a well-established objective measure of effort of breathing. Baseline Pes, defined as pleural pressure at end exhalation during tidal breathing, reflected the positive pressure generated on each level of respiratory support. Twenty-five patients had measurements on high-flow humidified nasal cannula. Median age was 6.5 months (interquartile range, 1.3-15.5 mo). Median Pressure,Rate Product was lower on high-flow humidified nasal cannula 8 L/min (median, 329 cm H2O·min; interquartile range, 195-402) compared with high-flow humidified nasal cannula 5 L/min (median, 341; interquartile range, 232-475; p = 0.007) or high-flow humidified nasal cannula 2 L/min (median, 421; interquartile range, 233-621; p < 0.0001) and was lower on high-flow humidified nasal cannula 5 L/min compared with high-flow humidified nasal cannula 2 L/min (p = 0.01). Baseline Pes was higher on high-flow humidified nasal cannula 8 L/min than on high-flow humidified nasal cannula 2 L/min (p = 0.03). Increasing flow rates of high-flow humidified nasal cannula decreased effort of breathing in children, with the most significant impact seen from high-flow humidified nasal cannula 2 to 8 L/min. There are likely multiple mechanisms for this clinical effect, including generation of positive pressure and washout of airway dead space.

Effects of tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury and acute respiratory distress syndrome*

To assess the effects of step-changes in tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS). Prospective, nonconsecutive patients with ALI/ARDS. Adult surgical, trauma, and medical intensive care units at a major inner-city, university-affiliated hospital. Ten patients with ALI/ARDS managed clinically with lung-protective ventilation. Five patients were ventilated at a progressively smaller tidal volume in 1 mL/kg steps between 8 and 5 mL/kg; five other patients were ventilated at a progressively larger tidal volume from 5 to 8 mL/kg. The volume mode was used with a flow rate of 75 L/min. Minute ventilation was maintained constant at each tidal volume setting. Afterward, patients were placed on continuous positive airway pressure for 1-2 mins to measure their spontaneous tidal volume. Work of breathing and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). Work of breathing progressively increased (0.86 +/- 0.32, 1.05 +/- 0.40, 1.22 +/- 0.36, and 1.57 +/- 0.43 J/L) at a tidal volume of 8, 7, 6, and 5 mL/kg, respectively. In nine of ten patients there was a strong negative correlation between work of breathing and the ventilator-to-patient tidal volume difference (R = -.75 to -.998). : The ventilator-delivered tidal volume exerts an independent influence on work of breathing during lung-protective ventilation in patients with ALI/ARDS. Patient work of breathing is inversely related to the difference between the ventilator-delivered tidal volume and patient-generated tidal volume during a brief trial of unassisted breathing.

Additional work of breathing and breathing patterns in spontaneously breathing patients during pressure support ventilation, automatic tube compensation and amplified spontaneous pattern breathing

Additional work of breathing and breathing patterns in spontaneously breathing patients during pressure support ventilation, automatic tube compensation and amplified spontaneous pattern breathing

Effect of inspiratory time on tidal volume delivery in anesthesia and intensive care unit ventilators operating in pressure control mode

Study objective To compare the effect of inspiratory time and lung compliance on tidal volume (V t) delivery in anesthesia and intensive care unit (ICU) ventilators operating in pressure control mode. Setting Respiratory research laboratory of a tertiary care medical center. Design Two anesthesia ventilators with pressure control capability (Narkomed 6000, Dräger Medical, Inc, Telford, Pa, and the Datex-Ohmeda Aestiva 5, Datex-Ohmeda, Inc, Madison, Wis) and one critical care ventilator (Puritan Bennett 7200, Puritan-Bennett, Pleasanton, Calif) were studied under varying inspiratory time and lung compliance conditions using a mechanical lung model. Intervention Each ventilator was set to pressure control mode at a fixed inspiratory/expiratory (I/E) ratio. The respiratory rate (RR) was varied between 6 and 28 breaths per minute. Lung compliance and inspiratory time settings were set to simulate clinical conditions known to affect anesthesia ventilator performance. Measurements Inspiratory flow, V ts, and peak airway pressures were measured using the on-board monitor for each ventilator, and confirmed with the Bicore CP-100 pulmonary mechanics monitor (Bicore Monitoring Systems, Inc, Irvine, Calif). To assess differences in inspiratory flow between ventilators, airway pressures were continuously monitored during inspiration. Main results Increasing RRs caused delivered V ts to decrease for all ventilators. However, decreases in V ts were significantly larger for anesthesia than for ICU ventilators. At a lung compliance of 0.02 L/cm H 2O and set V t of 700 mL, V t delivery for the Puritan Bennett 7200 ventilator remained at 88% of baseline, but decreased to 76% for the Aestiva 5 when RRs were increased from 6 to 28 breaths per minute ( P < .0025). Airway pressure tracings demonstrated a slower increase in inspiratory airway pressure for the Aestiva 5 than for the other ventilators. Conclusion Differences in inspiratory flow delivery between ICU and anesthesia ventilators can cause differences in V t delivery when the pressure control mode is used at high RRs. These differences can significantly impact the perioperative care of critically ill patients requiring ventilatory support.

Improved flow and pressure capabilities of the Datex-Ohmeda SmartVent anesthesia ventilator

Study Objective: To compare the flow and pressure capabilities of the Datex-Ohmeda SmartVent (Ohmeda 7900, Datex-Ohmeda, Madison, WI) to previous Ohmeda (7810 and 7000, Datex-Ohmeda, Madison, WI) anesthesia ventilators. To determine airway pressure and minute ventilation thresholds for intraoperative use of a critical care ventilator. Design: Three anesthesia ventilators and one critical care ventilator (Siemens Servo 900C, Siemens, Solna, Sweden) were studied in a lung model. Retrospective medical record review. Setting: Research Laboratory and Critical Care Unit of a Level I Trauma Center. Patients: 145 mechanically ventilated patients treated for acute respiratory failure who underwent 200 surgical procedures. Interventions: The effect of increasing pressure on mean inspiratory flow was determined by cycling each ventilator through increasing restrictors. Maximum minute ventilation was measured at low compliance (10–30 mL/cm H 2O), positive end-expiratory pressure (PEEP) (0–20 cm H 2O), and increased airway resistance (∼19 and ∼36 cm H 2O/L/sec) in a mechanical lung model. Measurements and Main Results: Flow, volume, and pressure were measured with a pulmonary mechanics monitor (BICORE CP-100, Thermo Respiratory Group, Yorba Linda, CA). Preoperative peak airway pressure and minute ventilation (V̇ E) were extracted from the medical record. Mean inspiratory flow declined with increasing pressure in all anesthesia ventilators. The SmartVent and the 7810 produced greater mean inspiratory flow than did the 7000 ventilator. As compliance progressively decreased, the Siemens, the SmartVent, and the 7810 ventilators maintained V̇ E compared to the 7000 ventilator. The Siemens and the SmartVent maintained V̇ E with PEEP, compared to the 7810 and 7000 ventilators. During increased airway resistance, maximal V̇ E was lower for all ventilators. The SmartVent met the ventilation requirements in 90% of the patients compared to 67% of patients with the 7000 ventilator. Conclusion: The improved pressure and flow capabilities of the SmartVent increase the threshold for using a critical care ventilator intraoperatively to a peak airway pressure >65 cm H 2O and/or V̇ E >18 L/min.

Respiratory flow measurements and anesthetic drugs: some in vitro observations

Study Objective: To illustrate the influence of anesthetic gases on respiratory flow measurements and to correct this influence. Design: In vitro evaluation. Setting: Laboratory. Measurements and Main Results: An in vitro method using a 120-L Tissot water-seal spirometer was used along with a Bicore CP-100, designed for use in intensive care units, and a Datex Ultima, designed for use in the operating room. The flow transducer of one of the instruments being tested was placed in the gas inlet of the Tissot so that simultaneous measurements could be made. Timed flows (2 to 60 L/min) of various gases (O 2 and air) and gas mixtures (halothane-O 2, isoflurane-O 2, N 2O-O 2, and N 2O-O 2-isoflurane) were used and the measurements made by the Tissot and the test instrument compared. The Datex Ultima, which includes software corrections for anesthetics, was able to accurately measure gas flows (2 to 60 L/min) of air, 100% oxygen, and anesthetic gas mixtures to within ±10% of measurements made by the Tissot. The Bicore CP-100, intended for use with mechanically ventilated patients, accurately measured air and 100% oxygen flow rate to within ±8% of the measurements made by the Tissot, but there were large errors (up to 40%) when anesthetics were used. Conclusions: This study illustrates the effects of anesthetic gases on measurements of ventilatory flow and the need to ascertain whether corrections are needed to improve the accuracy of flow transducers.

Effects of dexamethasone on meconium aspiration syndrome in newborn piglets.

We examined the effects of dexamethasone on lung function in a piglet model of meconium aspiration syndrome. We induced lung injury in 10 newborn piglets (age 5 +/- 0.2 d) with 4 mL/kg body weight of 20% sterile human meconium in normal saline given via tracheostomy. Ventilator management was aimed at maintaining comparable values of end tidal carbon dioxide, Hb saturation, and arterial blood gases. Lung function was assessed using a BICORE CP100 neonatal monitor. Five piglets received 0.5 mg/kg of dexamethasone 2 and 8 h after meconium administration, whereas control piglets received normal saline at similar times. Ventilator settings, oxygen requirements, and lung compliance were similar between groups at the start of the study. Two hours after the instillation of meconium, there was marked lung dysfunction in both groups as evidenced by increased oxygen requirements [fraction of inspired oxygen (FiO2) 0.98 +/- 0.01 versus FiO2 0.21 +/- 0, p < 0.0001] and reduced lung compliance (0.35 +/- 0.03 versus 0.8 +/- 0.03 mL x kg(-1) x cm(-1) H2O, p < 0.0001). Administration of dexamethasone resulted in lower oxygen requirements (FiO2 0.27 +/- 0.01 versus FiO2 1.0 +/- 0.0, p < 0.00001), lower oxygenation index (2.17 +/- 0.17 versus 22.64 +/- 3.39, p < 0.0001), ventilatory efficiency index (0.30 +/- 0.01 versus 0.07 +/- 0.01, p < 0.0001), and improved lung compliance (0.68 +/- 0.04 versus 0.34 +/- 0.05 mL x kg(-1) x cm(-1) H2O, p < 0.001) compared with the control group. In summary, a two-dose course of 0.5 mg/kg of dexamethasone improved blood gases and lung function in a piglet model of meconium aspiration syndrome.

Accuracy of volume measurements in mechanically ventilated newborns: a comparative study of commercial devices.

Ventilatory measurements in ventilated newborns are increasingly used to monitor and to optimize mechanical ventilation. The aim of this study was to compare the accuracy of volume measurements by different instruments using standardized laboratory conditions. The accuracy of displayed volume values of different commercial devices (Bicore CP-100, Ventrak 1500, Ventrak 1550, Babylog 8000, PEDS IV and SensorMedics 2600) was investigated using adjustable calibration syringes (volume range 2-60 ml, breathing rates 30/min-60/min) and humidified (>95%), heated (35 degrees C) breathing gas with adjustable FIO2 (0.21-1.0). The pneumotach and also the tubes were placed within an incubator (37 degrees C). The relative volume error of all devices was in conformity with clinically allowed tolerances (Bicore CP-100 6.4+/-0.5% (mean +/- SD), Ventrak 1500 3.6+/-4.2%, Ventrak 1550 6.5+/-2.7%, Babylog 8000 -5.5+/-1.5%, PEDS IV -4.0+/-1.4%, SensorMedics 2600 3.5+/-1.75%) for the measuring range studied (10 ml < V < 60 ml, rate 30-60/min, FIO2 = 0.21). Unacceptable errors were obtained for volumes lower than 10 ml with Bicore CP-100 (-28.5+/-26%) and PEDS IV (-10.3+/-3.4%). Changes in FIO2 had an important influence on volume measurements and only the SensorMedics 2600 and the PEDS IV corrected properly for FIO2 changes. Most of the currently available neonatal spirometry devices allow sufficiently accurate volume measurements in the range of 10-60 ml and at frequencies between 30-60/min provided that an increased FIO2 is taken into account.

Use of the rapid/shallow breathing index as an indicator of patient work of breathing during pressure support ventilation

Background . Measuring patient work of breathing (WOB pt) has been suggested to provide safe, aggressive weaning from mechanical ventilation. We compared WOB pt and pressure-time-product (PTP) to routine weaning parameters [breath rate (f), tidal volume (V T), frequency/tidal volume ratio (f/V T)] at different levels of pressure support ventilation (PSV). Methods . Fifteen patients in the surgical intensive care unit requiring prolonged weaning (more than 3 days) were entered in the study. A balloon-tipped esophageal catheter was placed and position confirmed by inspection of pressure and flow waveforms. Each patient was randomly assigned to breathe with 5, 10, 15, and 20 cm H 2O of PSV. After 30 minutes, 40 breaths were recorded and analyzed. Measurement of WOB pt, PTP, f, V T and f/V T were made using the Bicore CP-100 monitor. Mean values for each parameter were calculated. PTP and WOB pt were plotted against f/V T to determine correlation coefficient. Results . PTP, WOB pt, and f/V T decreased in a stepwise fashion as PSV was increased. The f/V T correlated most closely with WOB pt (r = 0.983) and PTP (r = 0.972). Monitoring f alone also correlated with WOB pt (r = 0.894) and PTP (r = 0.881). All patients were weaned from the ventilator (mean duration, 22 ± 5.9 days). Nine patients required tracheostomy before final liberation from the ventilator. Conclusions . Direct measurement of WOB pt is invasive, expensive, and may be confusing to clinicians. Monitoring f/V T may be useful when changing PSV during weaning.

CAN STEROIDS AMELIORATE MECONIUM ASPIRATION SYNDROME IN PIGLETS? † 1527

The effects of dexamethasone on pulmonary function in Meconium Aspiration Syndrome (MAS) were examined in five day old piglets. Animals were paralyzed, sedated, and ventilated via tracheostomy. Lung injury was induced with 4cc per kilogram bodyweigth of 20% sterile human meconium slurry in normal saline given via tracheostomy. Ventilator management was by a specific protocol designed to keep similar end tidal carbon dioxide levels and oxygen saturation(determined via pulse oximetery), which were correlated with blood gas measurements. Pulmonary function were measured using a Bicore CP100 neonatal monitor. Study animals received 0.5 milligram per kilogram of dexamethasone at two hours and eight hours after meconium adminstration; controls received saline at comparable times. Ventilator settings, oxygen requirements and lung compliances were similar between groups at the start of the study. The table below summarizes the findings at two and twelve hours following meconium administration.

THE EFFECT OF TIDAL VOLUME (Vt) DRIVEN WEANING PROTOCOLS (WP) IN INTUBATED NEONATES WITH ACUTE RESPIRATORY DISTRESS SYNDROME (RDS) 1173

Historically, pressure limited, time cycled ventilation has been the cornerstone of neonatal ventilation. The advent of sensitive flow sensors now allows rapid, continuous measurement of Vt in small neonates. We hypothesized that an algorithm combining Vt measurements with maximal use of noninvasive monitoring would allow safe, uniform weaning of infants with RDS from mechanical ventilation with a minimum of blood draws. The primary premise of the algorithm: using Vt to modify peak inspiratory pressure (PIP) to keep Vt 5-7 ml/kg; modify rate to keep pH 7.27-7.33; modify FiO2 to maintain SaO2 89-94%. Tidal volumes were measured with the Bicore CP-100 Neonatal monitor. This uses a self calibrated transducer to measure air flow. Flow is then integrated to give the infant's tidal volume. CO2 was monitored with transcutaneous CO2 (Novametrix), SaO2 with the Nellcor pulse oximeter. Arterial blood gases were drawn from the umbilical arterial line when available, or peripheral capillary blood gases were followed. Data from 33 infants (mean BW=1326g, GA=29.5 wks, 54% male, 50% Caucasian, initial mean airway pressure (MAP)=8.5 cmH2O, initial FIO2= 0.62) intubated secondary to RDS and managed as per the WP were evaluated. This was compared with data from 33 matched retrospective controls (mean BW=1274 g, GA=29.2 wks, 57% male, 66% Caucasian, initial MAP=8.7 cm H2O, FIO2=0.63). Primary outcome variables included: initial PIP (IPIP) and maximum PIP (MPIP), total blood gases (BG) for initial 72 hours of management and for first 7 days of hospitalization, and duration of mechanical ventilation. No patient managed per the weaning protocol had a pH value of <7.25. There was a significant difference between the two groups in terms of IPIP (WP=21cm H2O vs NO WP= 24 cm H2O, p<0.03), MPIP (WP = 21.8 cm H2O vs NO WP= 25.0 cmH2O, p<0.01). The infants managed with the WP had an average of 13.6 BGs drawn during the first 72 hours vs. 22.5 BGs for the NO WP (p<0.001). For the first week, the WP infants had 19.0 BG vs. 33.5 BG (p < 0.01). In terms of hospital charges for BG in the first week, the WP charges were $1452 vs $2560 for the NO WP. Actual hospital COST (therapist time and supplies per blood gas) resulted in saving $65 per patient for the first week ($85 vs. $150; p<0.01). Although the infants on the WP had a trend for decreased time on ventilation, there was no significant difference. Institution of the Vt driven WP enhanced our ability to wean comparable infants with RDS in a uniform manner with significantly decreased IPIP and MPIP, and decreased BGs at both 72 hours and 7 days. We hypothesize that Vt driven WP may decrease barotrauma, and with their concurrent savings, can safely provide consistent and cost effective weaning of infants with acute RDS.

In vitro assessment of infant pulmonary function equipment

Commercially available automated pulmonary monitors are used increasingly in neonatal intensive care units. However, detailed information regarding the static and dynamic accuracy of these monitors is rarely available. Collaboration between scientists, clinicians, and manufacturers is essential to establish improved technical standards and protocols for testing of equipment and for the development of more reliable neonatal pulmonary monitors. The aim of this study was to develop a protocol for the in vitro assessment of commercial infant pulmonary function equipment which could be applied within the laboratory to provide rapid feedback to the manufacturer. A recently released neonatal pulmonary monitor, the Bicore CP100 (software version 3.3), was selected for the development of this protocol. The deadspace and resistance of the measuring device were determined. The flow and airway pressure measuring systems were evaluated alone and connected to a tracheal tube for both static accuracy and frequency response. The pressure-volume relationship of the esophageal balloon was determined and its static accuracy and frequency response were assessed. The algorithms for on-line calculations were checked and their correct application confirmed by examination of an ASCII data print out. Finally, the pulmonary monitor was tested during intermittent positive pressure ventilation of a neonatal lung model of known compliance and resistance.

Protective effects of inhaled aminophylline on methacholine-induced airway responses in greyhound dogs

Aminopylline can be delivered as a heated aerosol via an air-powered small-volume nebulizer. We tested the hypothesis that inhaled aminophylline could attenuate the effects of inhaled methacholine on the airways. Five greyhound dogs were anesthetized, intubated, and ventilated. An esophageal balloon and flow transducer were placed in the ventilator circuit and connected to a BICORE CP-100 respiratory monitor. We measured mean lung resistance, lung dynamic compliance, and work of breathing. Each dog was pretreated for 30 minutes with three different formulations given randomly on separate days: aerosolized saline and intravenous saline, aerosolized aminophylline and intravenous saline, and aerosolized saline and intravenous aminophylline. The dogs were then exposed to a series of five inhalations of methacholine of increasing concentrations given at 15-minute intervals. The results demonstrated a significant reduction in the work of breathing and lung resistance and significantly increased compliance after treatment with aerosolized aminophylline but not with intravenous aminophylline. These findings support our hypothesis that aerosolized aminophylline has a protective effect against methacholine-induced bronchospasm. The results further suggest the possible use of aerosolized aminophylline for the treatment of obstructive lung disease.

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.

The Bicore pulmonary monitor

The Bicore CP-100 pulmonary monitor offers the advantage of continuous pulmonary monitoring at the bedside. Using an easily placed oesophageal balloon catheter and a flow transducer within the ventilator system, intrathoracic pressures, airway pressures and airway flow can be measured, and from these the Bicore calculates 25 other respiratory variables. The monitor screen displays real time waveforms of airway pressure, airway flow, oesophageal pressure and inspired tidal volume, and with these data it should be possible to determine more accurately when patients can be weaned from mechanical ventilation. It should also be possible to assess objectively the onset of respiratory fatigue and failure so that intervention can take place at an earlier stage. To assess the ease of use and potential benefit, the Bicore was used to calculate the work of breathing while weaning eight patients from mechanical ventilation in a spontaneous breathing mode. The pressure support ranged from 20 cmH2O, 10 cmH2O and 5 cmH2O, to a continuous positive airway pressure of 5 cmH2O, all with a positive end-expiratory pressure of 5 cmH2O, down to a single T-circuit with no positive airway pressure or end-expiratory pressure. The work of breathing while on a Veola Hamilton ventilator was found to be about the same, while receiving pressure support of 20 cmH2O compared to a continuous positive airway pressure of 5; the other forms of respiratory support increased the work of breathing significantly.