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PubMed1992

In-vitro fertilisation and neonatal ventilator use in a tertiary perinatal centre.

OBJECTIVE: To determine the contribution of livebirths resulting from in-vitro fertilisation and related technologies (IVF) to the use of neonatal ventilator beds. DESIGN: A retrospective review of records of all livebirths from our hospital's IVF program and all IVF infants receiving mechanical ventilation in our neonatal intensive care unit for the period 1985-1989. We also reviewed records of labour ward deliveries, neonatal intensive care unit admissions and transfer requests in order to obtain comparative data for livebirths of non-IVF infants whose mothers had been booked to deliver in our hospital. SETTING: A tertiary perinatal centre with a large IVF program and a Level 3 neonatal intensive care unit. RESULTS: IVF livebirths accounted for 5.1% of total ventilator bed days. Compared with non-IVF booked livebirths, IVF babies were more likely to require ventilation (odds ratio, 7.41; P less than 0.0001) and used more ventilator bed days per 100 livebirths (rate ratio, 9.63; P less than 0.0001), largely due to preterm delivery of multiple pregnancies; 42.3% of IVF babies who required ventilation were from triplet births and 38.5% from twin births. Nevertheless, even IVF singletons used more ventilator bed days per 100 livebirths than non-IVF booked livebirths (rate ratio, 2.78; P less than 0.0001). IVF livebirths accounted for 9.9% of the 78% increase in ventilator bed days used in 1989 compared with 1985. CONCLUSIONS: IVF livebirths accounted for only a small percentage of the overall use of neonatal ventilator beds, but consumed relatively more of such resources per livebirth than did non-IVF livebirths. The degree of risk of requiring ventilation is directly related to the number of infants in a multiple pregnancy, but even IVF singletons are at a relatively high risk of requiring ventilation.

Female↗
PubMed2000

The effects of pressure control versus volume control assisted ventilation on patient work of breathing in acute lung injury and acute respiratory distress syndrome.

BACKGROUND: Patient work of breathing (WOB) during assisted ventilation is reduced when inspiratory flow (V(I)) from the ventilator exceeds patient flow demand. Patients in acute respiratory failure often have unstable breathing patterns and their requirements for V(I) may change from breath to breath. Volume control ventilation (VCV) traditionally incorporates a pre-set ventilator V(I) that remains constant even under conditions of changing patient flow demand. In contrast, pressure control ventilation (PCV) incorporates a variable decelerating flow wave form with a high ventilator V(I) as inspiration commences. We compared the effects of flow patterns on assisted WOB during VCV and PCV. METHODS: WOB was measured with a BICORE CP-100 monitor (incorporating a Campbell Diagram) in a prospective, randomized cross-over study of 18 mechanically ventilated adult patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Tidal volume, inspiratory time, and mean ventilator V(I) were constant in each mode. RESULTS: At comparable levels of respiratory drive and minute ventilation, patient WOB was significantly lower with PCV than with VCV (0.59 +/- 0.42 J/L vs 0.70 +/- 0.58 J/L, respectively, p < 0.05). Ventilator peak V(I) was significantly higher with PCV than with VCV (103.2 +/- 22.8 L/min vs 43.8 L/min, respectively, p < 0.01). CONCLUSIONS: In the setting of ALI and ARDS, PCV significantly reduced patient WOB relative to VCV. The decrease in patient WOB was attributed to the higher ventilator peak V(I) of PCV.

Adult↗
PubMed2001

A new system for understanding modes of mechanical ventilation.

Numerous ventilation modes and ventilation options have become available as new mechanical ventilators have reached the market. Ventilator manufacturers have no standardized terminology for ventilator modes and ventilation options, and ventilator operator's manuals do not help the clinician compare the modes of ventilators from different manufacturers. This article proposes a standardized system for classifying ventilation modes, based on general engineering principles and a small set of explicit definitions. Though there may be resistance by ventilator manufacturers to a standardized system of ventilation terminology, clinicians and health care equipment purchasers should adopt such a system in the interest of clear communication--the lack of which prevents clinicians from fully understanding the therapies they administer and could compromise the quality of patient care.

Biomedical Engineering↗
PubMed2003

[Lung protective strategies of ventilation in respiratory distress syndrome of neonates].

OBJECTIVE: The authors compared the protective ventilation strategies with the assistance of pulmonary mechanic measurements (PM) to the conventional ventilation practice in order to investigate the incidence of VALI, explore the best ventilator settings in RDS and the clinical effects of hypercapnia in neonates. METHODS: One hundred and ten newborn infants, diagnosed as respiratory distress syndrome of neonatal and needed ventilator support, were recruited from the intensive care unit from 1994 to 2001. Infants with RDS were divided into non-pulmonary mechanics measurement (NPM) group and pulmonary mechanics measurement (PM) group. The ventilator settings, artery blood gas analysis, ventilator-associated lung injury and other clinical data were analyzed and compared. RESULTS: In the PM group, expiratory tidal volume of (7.70 +/- 1.05) ml/kg, C(20)/C of (1.98 +/- 0.92) and time constant of (0.09 +/- 0.03) sec were measured. Ventilator setting in PM group [PIP of (26.7 +/- 1.7) cmH(2)O, MAP of (11.9 +/- 2.0) cmH(2)O, Ti of (0.45 +/- 0.10) sec] were significantly less than those in NPM group [PIP of (30.5 +/- 3.4) cmH(2)O, MAP of (14.9 +/- 3.4) cmH(2)O, Ti of (0.75 +/- 0.10) sec P < 0.001, respectively]. No differences were noted in demographic data between the two groups regarding to the pH (7.30 +/- 0.04 vs 7.31 +/- 0.10), PaO(2) [(59 +/- 16) vs (57 +/- 17) mmHg], heart rate [(145 +/- 6) vs (144 +/- 8) bpm] and blood pressure [(39.0 +/- 3.6) vs (40.0 +/- 4.6) mmHg], except for PaCO(2) in PM group which was significantly higher than that in NPM group [(48 +/- 6) vs (40 +/- 10) mmHg, P < 0.001]. OI in PM group was significantly less than that in NPM group (14 +/- 8 vs 19 +/- 13, P < 0.05). Incidence of ventilator-associated lung injury in PM group was significantly lower than that in NPM group (13% vs 32%, P < 0.05). No differences were noted in demographic data between the two groups regarding to the length of ventilator support [(4.2 +/- 1.7) vs (3.9 +/- 1.8) day], length of supplemental oxygen requirements [(13 +/- 7) vs (11 +/- 7) day], length of hospitalization [(22 +/- 11) vs (19 +/- 14) day], mortality (8% vs 14%), incidence of PDA (33 vs 36%) and IVH (40% vs 42%). CONCLUSIONS: The assistance use of pulmonary mechanics measurement can guide the ventilator adjustment and decrease the ventilator-associated lung injury in neonatal RDS. The low PIP, low tidal volume, shorter inspiratory time and adequate PEEP strategies in the treatment of RDS showed no significant effects on the oxygenation in neonates. The mild permissive hypercarbia in newborn did not increase the incidence of IVH.

Blood Gas Analysis↗
PubMed2005

Predictors of fatality in neonates requiring mechanical ventilation.

OBJECTIVE: To evaluate initial arterial blood gas, pulmonary pressures, pulmonary mechanics (compliance and resistance), pulmonary volumes, oxygenation indices and serum carotenoid levels as predictors of fatality in mechanically ventilated neonates. DESIGN: Cross Sectional. SETTING: Referral neonatal unit of a teaching hospital. SUBJECTS: 83 mechanically ventilated outborn neonates. METHODS: 83 neonates consecutively put on mechanical ventilator from March to December 2001 were enrolled in the study. The mechanical ventilator used was pressure limited time cycled ventilator with facility for online measurement of volumes and pulmonary mechanics. Arterial blood gas after half an hour of initiation of mechanical ventilation and initial pulmonary pressures, pulmonary compliance, resistance and duration of mechanical ventilation were recorded in a pre structured proforma. Initial serum carotenoid levels were also measured using spectrophotometric method. The neonates were regularly followed up for outcome. Multiple logistic regression analysis was done to find out the predictors of fatality for those variables that were significantly associated with outcome on univariate analysis. RESULTS: On univariate analysis weight ( < 2000 g), gestational age <34 weeks, pH <7.3, duration of mechanical ventilation <72 hours, a/A <0.25, compliance <1 mL/cmH2O, fraction of inspired oxygen (FiO2) >60%, oxygenation index >10, AaDO2 >250 and serum carotenoid levels < 100 microg/dL were significantly associated with fatality in neonates requiring mechanical ventilation. However, on multiple regression analysis only FiO2, gestational age and serum carotenoids < 100 microg/dL were found to be independent predictors of fatality. CONCLUSIONS: Initial FiO2 > 60%, gestational age <34 weeks and initial serum carotenoid levels < 100 microg/dL were independent predictors of fatality in neonatal mechanical ventilation. Even in a setting with high fatality rates, high risk of mortality in mechanically ventilated neonates can be identified.

Carotenoids↗
PubMed2006

Changes of dipalmitoyl phosphatidyl choline after mechanical ventilation in patients with acute cerebral injury.

OBJECTIVE: To detect the levels of dipalmitoyl phosphatidyl choline (DPPC) in the sputum of the patients with acute cerebral injury without primary pulmonary injury after mechanical ventilation treatment. METHODS: DPPC levels in sputum of 35 patients with acute cerebral injury but without pulmonary injury were detected with high performance liquid chromatography at the beginning of ventilation and 16-20 days, 21-40 days, and 41-60 days after ventilation, respectively. RESULTS: There was no significant difference of the DPPC levels between 16-20 days after ventilation (3.36+/-0.49) and at the beginning of ventilation (3.37+/-0.58) (P>0.05). The mean levels of DPPC decreased significantly at 21-40 days (2.87 mg/ml+/-0.26 mg/ml, P<0.05) and 41-60 days (1.93 mg/ml+/-0.21 mg/ml, P<0.01) after ventilation compared with that at the beginning of ventilation. At the same period, the peak inspiratory pressure and the mean pressure of airway increased significantly, whereas the static compliance and the partial pressure of oxygen in artery decreased significantly. Among the 25 patients who received ventilation for more than 20 days, 8 (32%) had slightly-decreased partial pressure of oxygen in artery compared with that at the beginning of ventilation. CONCLUSIONS: Mechanical ventilation can decrease the DPPC levels, decrease the lung compliance and increase the airway pressure, even impair the oxygenation function in patients with acute cerebral injury. Abnormal DPPC is one of the major causes of ventilator-associated lung injury.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

High-frequency intratracheal pulmonary ventilation: improved gas exchange at lower airway pressures.

PURPOSE: Conventional ventilation in the neonatal intensive care unit causes iatrogenic injury to fragile newborn lungs, especially those with preexisting pathology or prematurity. Intratracheal pulmonary ventilation (ITPV), developed by Dr Theodor Kolobow and associates at the National Institutes of Health (NIH), incorporates a continuous flow of humidified gas through a reverse thrust catheter positioned at the distal end of the endotracheal tube. In animal studies ITPV was shown to facilitate gas exchange at low peak pressures by reducing physiological dead space, facilitating exhalation, and enhancing CO2 elimination. The specific aims of this project were (1) to invent a new ITPV-specific ventilator; (2) to optimize gas exchange in a newborn animal model at low airway pressures using higher frequency ITPV; and (3) to demonstrate efficacy and improved ventilation at lower airway pressures in a prematurity model. METHODS: (1) A new ventilator had to be constructed. The first prototype is microprocessor driven, incorporating controls for flow, pressures, and concentrations of gases. The ventilator has the capability to vary Fio2, respiratory rate (0 to 15 Hz), and inspiratory-expiratory I:E ratio. (2) Prototype testing was performed. Newborn lambs (n = 3, 6 to 7 kg) underwent tracheotomy and placement of arterial and venous lines. Lambs were initially supported on conventional mechanical ventilation (CMV). Animals were allowed to achieve steady state with measurements of baseline vital signs, arterial blood gases, and ventilatory settings. ITPV was instituted at a rate of 100 breaths per minute and flow adjusted to achieve lower peak carinal pressures than obtainable on conventional ventilation. In a stepwise fashion, respiratory rate, I:E ratio, and ITPV flows were varied while initially maintaining Paco2 constant, and then allowing improvement. (3) These experiments were repeated in preterm lambs (n = 6, 1.8 to 3.6 kg). RESULTS: At the time of transition from CMV to ITPV (rate, 100, I:E, 1:3), gas exchange was maintained despite a documented drop in average peak carinal pressure for the newborn lambs from 28.3 cm H2O on CMV to 10.3 cm H2O on ITPV (P = .028). The average peak carinal pressure fell even further at higher ITPV rates with adjustments in I:E ratio. For the premature lambs, peak carinal pressures also fell significantly on ITPV (44 to 32 cm H2O, P = .002) with corresponding significant improvement in ventilation (Paco2 from 52.2 to 31.9 mm Hg, P = .029). CONCLUSIONS: (1) Our new ITPV ventilator operates at rates and I:E ratios previously unobtainable. (2) In newborn and premature lambs ITPV functions most effectively at higher rates with higher gas flow rates and with longer exhalation, providing significantly improved gas exchange at significantly lower peak carinal pressures. (3) ITPV may prove beneficial in achieving gas exchange in newborns while avoiding barotrauma. Based on these data, we have initiated human clinical studies of ITPV in newborns with congenital diaphragmatic hernia or prematurity to improve gas exchange and reduce barotrauma in the neonatal intensive care unit.

Animals↗
PubMed2003

High-frequency oscillatory ventilation for acute respiratory distress syndrome in adult patients.

INTRODUCTION: High-frequency oscillatory ventilation (HFOV) using an open-lung strategy has been demonstrated to improve oxygenation in neonatal and pediatric respiratory failure, without increasing barotrauma. Animal studies using small (<4 mm) endotracheal tubes have shown reduced histopathologic evidence of lung injury and inflammatory mediator release, suggesting reduced ventilator-induced lung injury. CLINICAL STUDIES: During the last decade, case reports and observational studies of HFOV in patients failing conventional ventilation strategies have suggested improved oxygenation in adult patients with severe acute respiratory distress syndrome. These reports have also suggested that early (2 days) initiation of HFOV is more likely to result in survival than delayed initiation (>7 days). A recently published randomized, controlled trial in acute respiratory distress syndrome patients (n = 148) comparing HFOV with a pressure-control ventilation strategy (Pao(2)/Fio(2) ratio of 10 cm H(2)O) demonstrated early (<16 hrs) improvement in Pao(2)/Fio(2) (p =.008) in the HFOV group but no significant difference in oxygenation index between the two groups during the initial 72 hrs of treatment. Thirty-day mortality was 37% in the HFOV group and 52% in the conventional ventilation group (p =.102). There was no significant difference between treatment groups in the prevalence of barotrauma, hemodynamic instability, or mucus plugging. This study suggests that HFOV is as effective and safe as the conventional strategy to which it was compared. CLINICAL APPLICATION: For clinical use in adults, a trial of HFOV may be considered when Fio(2) requirements exceed 60% and mean airway pressure is approaching 20 cm H(2)O or higher (or, alternatively, positive end-expiratory pressure of >15 cm H(2)O). It is currently unknown whether initiating HFOV at a lower severity threshold would result in reduced ventilator-associated lung injury or mortality. FUTURE DIRECTIONS: Future studies should compare different algorithms of applying HFOV to determine the optimal techniques for achieving oxygenation and ventilation, while minimizing ventilator-associated lung injury. The potential role of adjunctive therapies used with HFOV (e.g., prone ventilation, inhaled nitric oxide, aerosolized vasodilators, liquid ventilation) will require further research.

Adult↗
PubMed1988

[High frequency ventilation with a conventional respiratory following heart surgery interventions].

This study was designed to compare the effects of Continuous Positive-Pressure Ventilation (CPPV) and, by using the same unmodified conventional ventilator, High-Frequency Positive-Pressure Ventilation (HFPPVkonv). First, CPPV and HFPPVkonv were studied in a lung model with both normal (R = 5 mbar/1/second) and elevated (R = 20 mbar/1/second) resistance. Our results indicate that in HFPPVkonv the large compressible volume of the conventional ventilator did not influence lung model ventilation at normal resistance. The adjusted (300 ml) tidal volume (VT) and the measured volume of actual expiration (270 ml) were about the same (Fig. 1). However, with elevated resistance air trapping occurred. The large compressible volume influenced model ventilation during both CPPV and HFPPVkonv (Fig. 2). As a second step we evaluated the effects of HFPPVkonv on gas exchange, airway pressure, and hemodynamics in 12 patients (aged 43-69) postoperatively after elective cardiac surgery. After a period of stabilization at the intensive care unit every patient was first ventilated with CPPV. The ventilator settings were: VT = 10-12 ml/kg, inspiratory: expiratory ratio (I:E) = 1:2, frequency (F) = 12/min, V = 60 1/min, PEEP = 5 cm, FiO2 = 40%. After 20 min of CPPV baseline measurements were made (series I). Then the initial ventilator settings of CPPV were switched to HFPPVkonv, the conventional ventilator remaining unmodified. The settings were changed as follows: I:E = 1:3, F = 60/min, V = 120 1/min, PEEP = 5 cm, FiO2 = 40%. During 60 min of HFPPVkonv variables were measured first after 20 min (series II) and again after another 40 min (series III). Minute volume had to be doubled after changing from CPPV to HPFFVkonv to achieve eucapnia. As a result of the new ventilatory settings, VT and hold showed a significant decrease (P less than 0.01) (Table 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Barotrauma associated with high-frequency jet ventilation for hypoxic salvage.

Most reports describe reduction in proximal airway pressures with high-frequency jet ventilation. This led us to speculate that high-frequency jet ventilation might reduce barotrauma by providing alveolar ventilation at lower airway pressures. We describe a group of patients in whom a high incidence of barotrauma was observed after institution of high-frequency jet ventilation despite reduction in measured airway pressures. Fifteen hypoxic patients who could not be treated with conventional ventilation and who had no roentgenographic evidence of barotrauma were entered into the study. Airway pressures were measured during conventional ventilation and at 2 and 24 hours after high-frequency jet ventilation. Despite significant reduction in peak inspiratory and mean airway pressures, pneumothorax developed in seven of the 15 patients, an average of 21 hours after initiation of high-frequency jet ventilation. Five patients had bilateral pneumothorax and three developed tension pneumothorax. Despite reductions in proximal airway pressures, barotrauma is a significant potential complication of high-frequency jet ventilation in patients with noncompliant lungs. We currently place bilateral prophylactic thoracostomy tubes in patients with adult respiratory distress syndrome prior to initiation of high-frequency jet ventilation.

Adult↗
PubMed2002

Are tidal volume measurements in neonatal pressure-controlled ventilation accurate?

Bedside pulmonary mechanics monitors (PMM) have become useful in ventilatory management in neonates. These monitors are used more frequently due to recent improvements in data-processing capabilities. PMM devices are often part of the ventilator or are separate units. The accuracy and reliability of these systems have not been carefully evaluated. We compared a single ventilatory parameter, tidal volume (V(t)), as measured by several systems. We looked at two freestanding PMMs: the Ventrak Respiratory Monitoring System (Novametrix, Wallingford, CT) and the Bicore CP-100 Neonatal Pulmonary Monitor (Allied Health Care Products, Riverside, CA), and three ventilators with built-in PMM: the VIP Bird Ventilator (Bird Products Corp., Palm Springs, CA), Siemens Servo 300A (Siemens-Elema AB, Solna, Sweden), and Drager Babylog 8000 (Drager, Inc., Chantilly, VA). A calibrated syringe (Hans Rudolph, Inc., Kansas City, MO) was used to deliver tidal volumes of 4, 10, and 20 mL to each ventilator system coupled with a freestanding PMM. After achieving steady state, six consecutive V(t) readings were taken simultaneously from the freestanding PMM and each ventilator. In a second portion of the bench study, we used pressure-control ventilation and measured exhaled tidal volume (V(te)) while ventilating a Bear Test Lung with the same three ventilators. We adjusted peak inspiratory pressure (PIP) under controlled conditions to achieve the three different targeted tidal volumes on the paired freestanding PMM. Again, six V(te) measurements were recorded for each tidal volume. Means and standard deviations were calculated.The percentage difference in measurement of V(t) delivered by calibrated syringe varied greatly, with the greatest discrepancy seen in the smallest tidal volumes, by up to 28%. In pressure control mode, V(te) as measured by the Siemens was significantly overestimated by 20-95%, with the biggest discrepancy at the smallest V(te), particularly when paired with the Bicore PMM. V(te), as measured by the VIP Bird and Drager paired with the Ventrak PMM, had a tendency to underestimate V(t) by up to 25% at the smallest V(te). However, when paired with the Bicore PMM, these same two ventilators read over target by up to 18%. Under controlled laboratory conditions, we demonstrated that true delivered V(te), as measured by the three ventilators and two freestanding PMM, differed markedly. In general, decreasing dynamic compliance of the tubing was not associated with greater inaccuracy in V(te) measurements.

Calibration↗
PubMed1987

High frequency ventilation in the neonatal period.

There are three forms of high frequency ventilation, high frequency jet ventilation (HFJV, up to 400/min), high frequency oscillation (HFO, up to 40 Hz), and high frequency positive pressure ventilation (HFPPV, rates between 60 and 150/min). The first two forms of ventilation are still experimental and have been used only in critically ill children where respiratory failure has been unresponsive to more conventional therapy. Unfortunately, however, HFJV has already been associated with a high incidence of tracheal lesions. High-frequency positive pressure ventilation, on the other hand, using conventional ventilators, has been used and studied widely. Certain neonatal ventilators function suboptimally at increased rates, resulting in a reduction in tidal exchange with a consequent clinical deterioration. Using appropriate ventilators, arterial oxygen tensions improve and carbon dioxide tensions are reduced at fast rates in non-paralysed infants. Air-trapping, however, may be a problem in infants paralysed and ventilated at fast rates. HFPPV have been associated with a reduced incidence of pneumothoraces, but there is no knowledge of the effect of this form of ventilation on subsequent lung growth.

Follow-Up Studies↗
PubMed1998

Triggering delay time and work of breathing in three paediatric patient-triggered ventilators.

PURPOSE: To compare the effectiveness of three patient-triggered ventilators by evaluating triggering delay time and pressure-volume loops during initiation of inspiration. METHODS: In a two-part study, a model lung was used in part 1 and 20 children, after tracheal intubation, in part 2. Triggering delay time and work of breathing (WOB) during pressure support ventilation using three patient-triggered ventilators: Servo Ventilator 300, VIP Bird, and SLE 2000 Neonatal Ventilator. Triggering delay time was from the beginning of negative deflection in the oesophageal pressure trace, to the onset of inspiration. The WOB was estimated directly by measuring the oesophageal pressure-volume loop. RESULTS: The Servo demonstrated superior triggering delay time and reduced WOB in the model study. The VIP Bird demonstrated shorter triggering delay and reduced WOB in the clinical component of the study. In the model lung, triggering delay time in the Servo 300 [62 +/- 6 msec (mean +/- SD)] was shorter than that in the VIP Bird (76 +/- 7 msec) (P < 0.05), and WOB with the SLE 2000 (202 +/- 37 g.cm) was greater than with other ventilators, (Servo 300, 112 +/- 32 g.cm and VIP Bird 72 +/- 41 g.cm) (P < 0.05). In the clinical study, triggering delay time in the VIP Bird (52 +/- 19 msec) was shorter than in the other ventilators, Servo 300 (66 +/- 14 msec), SLE 2000 (68 +/- 65 msec) (P < 0.05). The Servo 300 (56 +/- 34 g.cm) required higher WOB than the other ventilators: VIP Bird (22 +/- 12 g.cm), SLE 2000 (14 +/- 3 g.cm) (P < 0.05). CONCLUSION: Comparative model lung performance of these ventilators does not correspond with their clinical performance. In our clinical evaluation, the VIP Bird ventilator demonstrated superior performance with shorter triggering delay time, low WOB needed to initiate inspiration, and little air leak.

Air Pressure↗
PubMedDate not supplied

Contemporary anesthesia ventilators incur a significant "oxygen cost".

PURPOSE: Anesthesia ventilators use oxygen or oxygen/air mixtures to drive the bellows during controlled ventilation. As a practitioner may find himself in a situation that the only available oxygen source is a compressed oxygen cylinder, it is important to know the oxygen consumption of anesthesia ventilators during controlled ventilation. METHODS: We tested the Datex-Ohmeda 7900 ventilator mounted on an Excel 210 anesthesia machine under a variety of conditions. For comparison, we also tested the Ohmeda 7800 and the Dräger AV-2 ventilator under control conditions. All experiments were performed using a test lung. RESULTS: The oxygen consumption of the AV-2 and the Datex-Ohmeda ventilators averaged 302 +/- 17 L x hr(-1) and 564 +/- 68 to 599 +/- 56 L x hr(-1), respectively (P < 0.01 AV-2 vs 7800 and 7900). When using an E-type cylinder, this would result in a mean time to alarm of 93 min and 54 to 57 min, respectively. Decreased lung compliance increased the oxygen consumption to 848 +/- 16 L x hr(-1). CONCLUSIONS: Machine-driven mechanical ventilation incurs a significant "oxygen cost." We show that the amount of oxygen consumed by mechanical ventilation with contemporary anesthesia ventilators is influenced by patient-dependent factors and may greatly exceed the amount of oxygen delivered to the patient.

Airway Resistance↗
PubMed2004

Hydrochloric acid-induced lung injury: effects of early partial liquid ventilation on survival rate, gas exchange, and pulmonary neutrophil accumulation.

OBJECTIVE: Partial liquid ventilation can improve respiratory functions in acid-induced lung injury. We studied the effects of the interval between induction of injury and initiation of partial liquid ventilation on survival, gas exchange, and pulmonary neutrophil accumulation. MATERIAL AND METHODS: Anesthetized rats were randomly assigned to one of five groups ( n = 6 per group). Group 1 served as the control group, in the other groups an extended lung injury was induced by intratracheal instillation of hydrochloric acid. Whereas lungs of group 2 were gas-ventilated, group 3 received an early partial liquid ventilation (5 min after acid instillation) and group 4 a delayed partial liquid ventilation (30 min after acid instillation, 5 ml/kg perfluorocarbon). Group 5 received an additional continuous perfluorocarbon application of 5 ml x kg(-1) x h(-1) (30 min after acid instillation). Blood gases were measured with an intravascular blood gas sensor. RESULTS: Acid instillation resulted in a marked decrease in PO(2)-values within 30 min (from 481+/-37 mmHg to 128+/-71 mmHg, FiO(2) 1.0). Survival rate of the study period (12 h) was higher with early partial liquid ventilation. We observed no differences between groups in peak PO(2)-values during treatment. Histopathological examination, however, showed less pulmonary neutrophil accumulation in lungs of the early partial liquid ventilation group when compared to the delayed partial liquid ventilation group. CONCLUSIONS: Our results suggest that early partial liquid ventilation increases survival after extended acid-induced lung injury. While effects on arterial oxygenation appear not to predict acute survival we observed less intrapulmonary neutrophil accumulation with early partial liquid ventilation.

Animals↗
PubMed2005

Meta-analysis of controlled trials of ventilator therapy in acute lung injury and acute respiratory distress syndrome: an alternative perspective.

OBJECTIVE: The role of protective ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) is controversial. Evidence was sought from published randomised trials for a consistent treatment effect of protective ventilation and any covariate modification. DESIGN: Meta-analysis of protective ventilation trials in ALI/ARDS and meta-regression of covariates on treatment effect (log odds ratio), with respect to 28-day mortality. Heterogeneity impact on the meta-analysis was assessed by the H statistic (substantial impact, >1.5) and graphical analysis. Five trials with a total of 1,202 patients were considered. MEASUREMENTS AND RESULTS: Average 28-day mortality was 0.40 in the treatment group (protective ventilation, n=605) vs. 0.46 in the control group (control ventilation, n=597). The treatment effect (odds ratio) was: fixed-effects, 0.71 (95% CI 0.56-0.91, p=0.006; heterogeneity, p=0.06) and random effects: 0.80 (95% CI 0.49-1.31, p=0.37). Heterogeneity impact (H statistic=1.50) was adjudged as modest. The treatment effect was significant and (a) favoured protective ventilation for a tidal volume less than 7.7 ml/kg predicted (treatment group) and a mean plateau pressure of 30 cmH(2)O or higher (control group) but was not influenced by plateau pressure 21-30 cmH(2)O (treatment group) and (b) depended upon plateau pressure difference greater than 5-7 cmH(2)O between protective ventilation and standard ventilation. CONCLUSIONS: Overall treatment effect estimate favoured protective ventilation but did not achieve statistical significance. Protective ventilation depended upon threshold levels of tidal volume, plateau pressure, and plateau pressure difference.

Acute Disease↗
PubMed2005

Bedside waveforms interpretation as a tool to identify patient-ventilator asynchronies.

OBJECTIVE: During assisted modes of ventilatory support the ventilatory output is the final expression of the interaction between the ventilator and the patient's controller of breathing. This interaction may lead to patient-ventilator asynchrony, preventing the ventilator from achieving its goals, and may cause patient harm. Flow, volume, and airway pressure signals are significantly affected by patient-ventilator interaction and may serve as a tool to guide the physician to take the appropriate action to improve the synchrony between patient and ventilator. This review discusses the basic waveforms during assisted mechanical ventilation and how their interpretation may influence the management of ventilated patients. The discussion is limited on waveform eye interpretation of the signals without using any intervention which may interrupt the process of mechanical ventilation. DISCUSSION: Flow, volume, and airway pressure may be used to (a) identify the mode of ventilator assistance, triggering delay, ineffective efforts, and autotriggering, (b) estimate qualitatively patient's respiratory efforts, and (c) recognize delayed and premature opening of exhalation valve. These signals may also serve as a tool for gross estimation of respiratory system mechanics and monitor the effects of disease progression and various therapeutic interventions. CONCLUSIONS: Flow, volume, and airway pressure waveforms are valuable real-time tools in identifying various aspects of patient-ventilator interaction.

Data Display↗
PubMed1998

Nasal patency and biomarkers in nasal lavage--the significance of air exchange rate and type of ventilation in schools.

OBJECTIVES: The aim of the present study was to examine the relationships between the ventilation rate and the type of ventilation system, on the one hand, and objective nasal measures, on the other. METHODS: A standardized investigation, including acoustic rhinometry and nasal lavage, was performed in the school environment. All 279 school personnel working in the main buildings of 12 randomly selected primary schools in the municipality of Uppsala were invited, and 234 (84%) participated. The dimensions of the nasal cavity were measured with acoustic rhinometry. Eosinophil cationic protein (ECP), myeloperoxidase (MPO), lysozyme, and albumin were analyzed in the lavage fluid. The air exchange rate and the room temperature were measured in the classrooms. Relationships between nasal symptoms, nasal patency, and the concentration of biomarkers, on the one hand, and the type of ventilation system, the air exchange rate, and the temperature, on the other, were analyzed by both crude bivariate analysis and multiple regression models, controlling for the type of ventilation, the air exchange rate, room temperature, age, gender, smoking, atopy, and the urban vicinity of the school. RESULTS: A lower degree of nasal patency as measured by acoustic rhinometry and increased levels of ECP and lysozyme in nasal lavage were associated with a lower air exchange rate in the schools. Although mechanically ventilated schools had higher air exchange rates, they were associated with more nasal symptoms, and nasal mucosal swelling and with increased lavage levels of ECP and lysozyme as compared with schools with natural ventilation only. In contrast, 12 subjects working in a school with mechanical displacement ventilation had more patent noses and lower levels of inflammatory markers as compared with the personnel in schools with natural ventilation only. CONCLUSION: Our results indicate that both a low air exchange rate and mechanical ventilation systems based on dilution can be associated with reduced nasal patency and an inflammatory biomarker response of the nasal mucosa among school personnel. The only school with sufficient ventilation according to the current Swedish recommendations had a displacement system and the fewest signs of nasal reactions among the personnel.

Albumins↗