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PubMed1996

Evaluation of gas exchange, pulmonary compliance, and lung injury during total and partial liquid ventilation in the acute respiratory distress syndrome.

OBJECTIVE: To investigate whether pulmonary compliance and gas exchange will be sustained during "total" perfluorocarbon liquid ventilation followed by "partial" perfluorocarbon liquid ventilation when compared with gas ventilation in the setting of the acute respiratory distress syndrome (ARDS). STUDY DESIGN: A prospective, controlled, laboratory study. SETTING: A university research laboratory. SUBJECTS: Ten sheep, weighing 12.7 to 25.0 kg. INTERVENTIONS: Lung injury was induced in ten young sheep, utilizing a right atrial injection of 0.07 mL/kg of oleic acid followed by saline pulmonary lavage. Bijugular venovenous extracorporeal life support access, a pulmonary artery catheter, and a carotid artery catheter were placed. When the alveolar-arterial O2 gradient was >/= 600 torr and PaO2 </= 50 torr (</= 6.7 kPa) with an FIO2 of 1.0, extracorporeal life support was instituted. For the first 30 mins on extracorporeal life support, all animals were ventilated with gas. Animals were then ventilated with equal tidal volumes of 15 mL/kg during gas ventilation (n=5) over the ensuing 2.5 hrs, or with total liquid ventilation for 1 hr, followed by partial liquid ventilation for 1.5 hrs (total/partial liquid ventilation, n=5). MEASUREMENTS AND MAIN RESULTS: An increase in physiologic shunt (gas ventilation = 69 +/- 11%, total/partial liquid ventilation = 71 +/- 3%) and a decrease in static total pulmonary compliance measured at 20 mL/kg inflation volume (gas ventilation = O.48 +/- 0.03 mL/cm H2O/kg, total/partial liquid ventilation = 0.50 +/- 0.17 mL/cm H2O/kg) were observed in both groups with induction of lung injury. Physiologic shunt was significantly reduced during total and partial liquid ventilation when compared with physiologic shunt observed in the gas ventilation animals (gas ventilation = 93 +/- 8%, total liquid ventilation = 45 +/- 11%, p<.001; gas ventilation = 95 +/- 3%, partial liquid ventilation = 61 +/- 12%, p<.001), while static compliance was significantly increased in the total, but not the partial liquid ventilated animals when compared with the gas ventilated group (gas ventilation = 0.43 +/- 0.03 mL/cm H2O/kg, total liquid ventilation = 1.13 +/- 18 mL/cm H2O/kg, p <.001; gas ventilation = 0.41 +/- 0.02 mL/cm H2O/kg, partial liquid ventilation = 0.47 +/- 0.08, p = .151). In addition, the extracorporeal life support flow rate required to maintain adequate oxygenation was significantly lower in the total/partial liquid ventilation group when compared with that of the gas ventilation group (gas ventilation = 89 +/- 7 mL/kg/min, total liquid ventilation = 22 +/- 10 mL/kg/min, p <.001; gas ventilation = 91 +/- 12 mL/kg/min, partial liquid ventilation = 41 +/- 11 mL/kg/min, p < .001). Lung biopsy light microscopy demonstrated a marked reduction in alveolar hemorrhage, lung fluid accumulation, and inflammatory infiltration in the total/partial liquid ventilation animals when compared with the gas ventilation animals. CONCLUSIONS: In a model of severe ARDS, pulmonary gas exchange is improved during total followed by partial liquid ventilation. Pulmonary compliance is improved during total, but not during partial liquid ventilation. Total followed by partial liquid ventilation was associated with a reduction in alveolar hemorrhage, pulmonary edema, and lung inflammatory infiltration.

Animals↗
PubMed1996

Regional tracheal blood flow during conventional and high-frequency jet ventilation in suckling pigs.

OBJECTIVE: To determine whether intubation and ventilation with either conventional mechanical ventilation or high-frequency jet ventilation, using dry or humidified gas, could induce regional tracheal ischemia and serve as a basis for the tracheal necrosis observed clinically during ventilation. DESIGN: Prospective, multiple group, controlled experimental study. SETTING: Medical school research laboratory. SUBJECTS: Twenty, 3- to 5-wk-old suckling pigs. INTERVENTIONS: Anesthetized, closed-chest piglets were intubated and ventilated for 30 mins with conventional mechanical ventilation and then ventilated for 2 additional hrs with either conventional mechanical ventilation or high-frequency jet ventilation. Groups were also ventilated, using both modes of ventilation, with either 37 degrees C humidified gas or 25 degrees C dry gas. MEASUREMENTS AND MAIN RESULTS: Blood flow groups were compared during spontaneous breathing, conventional mechanical ventilation, high-frequency jet ventilation and both ventilation modes, using 37 degrees C humidified or 22 degrees C dry inspired gas. Groups were compared, using an analysis of variance with a Newman-Keul's post-test. Regional tracheal blood flow was measured, using radioactive microspheres. Cardiac output and organ blood flows were also monitored. Tracheal blood flow increased 10.3-fold within 30 mins after intubation, but there were no significant differences in regional or total tracheal blood flow between conventional mechanical ventilation and high-frequency jet ventilation, using 37 degrees C humidified gas. Tracheal blood flow was increased further using high-frequency jet ventilation and 25 degrees C dry gas but not conventional mechanical ventilation with dry gas. Although ventilation reduced cardiac output by approximately 30%, there were no significant differences in organ distribution between modes of ventilation. CONCLUSIONS: Acute tracheal hyperemia occurred with intubation and ventilation with both conventional mechanical ventilation and high-frequency jet ventilation but no differences were observed between ventilation modes. Hyperemia was further increased with cool, dry inspired gas, using high-frequency jet ventilation but not conventional mechanical ventilation. Although acute tracheal ischemia was not produced by high-frequency jet ventilation or conventional mechanical ventilation, factors which alter the balance between arterial supply and metabolic demand or induce inflammation may contribute to the tracheal necrosis reported during sustained ventilation.

Analysis of Variance↗
PubMed1995

Development and application of a simplified liquid ventilator.

OBJECTIVE: Perfluorocarbon liquid ventilation has been shown to have advantages over conventional gas ventilation in premature newborn and lung-injured animals. To simplify the process of liquid ventilation, we adapted an extra-corporeal life-support circuit as a time-cycled, volume-limited liquid ventilator. DESIGN: Laboratory study that involved sequential application of gas and liquid ventilation in normal cats and in lung-injured sheep. SETTING: A research laboratory at a university medical center. SUBJECTS: Eight normal cats weighing 2.7 to 3.8 kg (mean 3.1 +/- 0.5), and four lung-injured young sheep weighing 10.4 to 22.5 kg (mean 15.9 +/- 5.0). INTERVENTIONS: Normal cats were supported with traditional gas ventilation for 1 hr (respiratory rate 20 breaths/min, peak inspiratory pressure 12 cm H2O, positive end-expiratory pressure 4 cm H2O, and FIO2 1.0). The lungs were then filled with perfluorocarbon (30 mL/kg) and tidal volume liquid ventilation was instituted, utilizing a newly developed liquid ventilation device. Liquid ventilatory settings were 4 secs for inspiration time, 8 secs for expiration time, 5 breaths/min for respiratory rate, and 15 to 20 mL/kg for tidal volume. Liquid ventilation utilizing this device was also applied to sheep after induction of severe lung injury by right atrial injection of 0.07 mL/kg of oleic acid, followed by saline pulmonary lavage. Extracorporeal life support was instituted to provide a stable model of lung injury. For the first 30 mins of extracorporeal support, all animals were ventilated with gas. Animals were then ventilated with 15 mL/kg of perfluorocarbon over the ensuing 2.5 hrs. MEASUREMENTS AND MAIN RESULTS: In normal cats, mean PaO2 values after 1 hr of liquid or gas ventilation were 275 +/- 90 (SD) torr (36.7 +/- 10.4 kPa) in the liquid-ventilated animals and 332 +/- 78 torr (44.3 +/- 10.4 kPa) in the gas-ventilated animals (NS). Mean PaCO2 values were 40.5 +/- 5.7 torr (5.39 +/- 0.31 kPa) in the liquid-ventilated animals and 37.6 +/- 2.3 torr (5.01 +/- 0.31 kPa) in the gas-ventilated animals (NS). Mean arterial pH values were 7.35 +/- 0.07 in the liquid-ventilated animals and 7.34 +/- 0.04 in the gas-ventilated animals (NS). No significant changes in heart rate, mean arterial pressure, lung compliance, or right atrial venous oxygen saturation were observed during liquid ventilation when compared with gas ventilation. In the lung-injured sheep, an increase in physiologic shunt from 15 +/- 7% to 66 +/- 9% was observed with induction of lung injury during gas ventilation. Liquid ventilation resulted in a significant reduction in physiologic shunt to 31 +/- 10% (p < .001). In addition, the extracorporeal blood flow rate required to maintain the PaO2 in the 50 to 80 torr (6.7 to 10.7 kPa) range was substantially and significantly (p < .001) lower during liquid ventilation than during gas ventilation (liquid ventilation 15 +/- 5 vs. gas ventilation 87 +/- 15 mL/min/kg). CONCLUSIONS: Liquid ventilation can be performed successfully utilizing this simple adaptation of an extracorporeal life-support circuit. This modification to an existing extracorporeal circuit may allow other centers to apply this new investigational method of ventilation in the laboratory or clinical setting.

Animals↗
PubMed1997

Prolonged partial liquid ventilation using conventional and high-frequency ventilatory techniques: gas exchange and lung pathology in an animal model of respiratory distress syndrome.

OBJECTIVE: To evaluate the effect of prolonged partial liquid ventilation with perflubron (partial liquid ventilation), using conventional and high-frequency ventilatory techniques, on gas exchange, hemodynamics, and lung pathology in an animal model of lung injury. DESIGN: Prospective, randomized, controlled study. SETTING: Animal laboratory of the Infant Pulmonary Research Center, Children's Health Care-St. Paul. SUBJECTS: Thirty-six newborn piglets. INTERVENTIONS: We studied newborn piglets with lung injury induced by saline lavage. Animals were randomized into one of five treatment groups: a) conventional gas ventilation (n = 8); b) partial liquid ventilation with conventional ventilation (n = 7); c) partial liquid ventilation with high-frequency jet ventilation (n = 7); d) partial liquid ventilation with high-frequency oscillation (n = 7); and e) partial liquid ventilation with high-frequency flow interruption (n = 7). After induction of lung injury, all partial liquid ventilation animals received intratracheal perflubron to approximate functional residual capacity. After 30 mins of stabilization, animals randomized to high-frequency ventilation were changed to their respective high-frequency modes. Hemodynamics and blood gases were measured before and after lung injury, after perflubron administration, and then every 4 hrs for 20 hrs. Histopathologic evaluation was carried out using semiquantitative scoring and computer-assisted morphometric analysis on pulmonary tissue from animals surviving at least 16 hrs. MEASUREMENTS AND MAIN RESULTS: All animals developed acidosis and hypoxemia after lung injury. Oxygenation significantly (p < .001) improved after perflubron administration in all partial liquid ventilation groups. After 4 hrs, oxygenation was similar in all ventilator groups. The partial liquid ventilation-jet ventilation group had the highest pH; intergroup differences were seen at 16 and 20 hrs (p < .05). The partial liquid ventilation-oscillation group required higher mean airway pressure; intergroup differences were significant at 4 and 8 hrs (p < .05). Aortic pressures, central venous pressures, and heart rates were not different at any time point. Survival rate was significantly lower in the partial liquid ventilation-flow interruption group (p < .05). All partial liquid ventilation-treated animals had less lung injury compared with gas-ventilated animals by both histologic and morphometric analysis (p < .05). The lower lobes of all partial liquid ventilation-treated animals demonstrated less damage than the upper lobes, although scores reached significance (p < .05) only in the partial liquid ventilation-conventional ventilation animals. CONCLUSIONS: In this animal model, partial liquid ventilation using conventional or high-frequency ventilation provided rapid and sustained improvements in oxygenation without adverse hemodynamic consequences. Animals treated with partial liquid ventilation-flow interruption had a significantly decreased survival rate vs. animals treated with the other studied techniques. Histopathologic and morphometric analysis showed significantly less injury in the lower lobes of lungs from animals treated with partial liquid ventilation. High-frequency ventilation techniques did not further improve pathologic outcome.

Animals↗
PubMed2004

Synchronized mechanical ventilation for respiratory support in newborn infants.

BACKGROUND: During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. Thus, if synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing barotrauma and hence airleak and chronic lung disease. Synchronous ventilation can be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient assisted ventilation. OBJECTIVES: To compare (i) the efficacy of synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation or triggered ventilation (patient triggered ventilation (PTV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation(ii) different types of triggered ventilation SEARCH STRATEGY: Searches from 1985-2004 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants. SELECTION CRITERIA: Randomized or quasi randomized clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (PTV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomized trials comparing different triggered ventilation modes (PTV and SIMV) in neonates. DATA COLLECTION AND ANALYSIS: Data regarding clinical outcomes including mortality, airleaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intracerebral haemorrhage (grades 3 and 4), chronic lung disease (oxygen dependency beyond 28 days) and duration of weaning/ventilation. Three comparisons were made: (i) HFPPV vs CMV; (ii) PTV/SIMV vs CMV; (iii) PTV vs SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale. MAIN RESULTS: Eleven studies were eligible for inclusion. The meta-analysis demonstrate that HFPPV compared to CMV was associated with a reduction in the risk of airleak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). PTV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). PTV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of chronic lung disease. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV, but a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. REVIEWERS' CONCLUSIONS: Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in airleak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimization of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials.

Humans↗
PubMed1997

Variation of inhaled nitric oxide concentration with the use of a continuous flow ventilator.

OBJECTIVE: To investigate the homogeneity of nitric oxide concentrations at different ventilator settings in a delivery system using a continuous flow ventilator. DESIGN: A prospective bench study using a nitric oxide delivery system, mixing a nitrogen/nitric oxide gas mixture in the ventilator circuit with two types of continuous flow ventilators (Babylog 8000, Draeger, Luebeck, Germany; Infant Star, Infrasonics, San Diego, CA). SETTING: A biomedical laboratory. INTERVENTIONS: A nitrogen/nitric oxide gas mixture was injected at three different sites in the ventilator circuit (just before and just behind the humidifier, and 20 cm before the Y-connector). Ventilator flow (12, 15, and 20 L/min) and rates (30 to 110 breaths/min with increments of 10 breaths/min) were changed as well as the compliance of the test lung (0.36, 0.5, and 1.0 mL/cm H2O). Carbon dioxide, instead of nitrogen/nitric oxide, was injected at the same points in the circuit. MEASUREMENTS AND MAIN RESULTS: The mean nitric oxide concentration increased significantly (p < .001) with increasing ventilator rates (although the flow ratio of the ventilator gas and the nitrogen/nitric oxide gas mixture was kept constant) when the nitrogen/nitric oxide injection site was near to the Y-connector of the ventilator circuit with both ventilators. The mean nitric oxide concentration did not change significantly when the nitrogen/nitric oxide gas mixture was mixed to the ventilator gas at the inlet of the humidifier, using the Babylog 8000 ventilator. Analysis of ventilator circuit flow patterns showed fluctuations during the respiratory cycle. The magnitude of the flow changes was different at the three injection sites in the ventilator circuit. Real-time measurements of the CO2 concentration showed fluctuations during the distinct respiratory phases that differed at the separate injection sites. Mean CO2 concentrations showed a similar pattern as compared with the mean nitric oxide concentration data at the same settings. CONCLUSIONS: Mixing a nitrogen/nitric oxide gas mixture 20 cm before the Y-connector results in an increase of the mean nitric oxide concentration with increasing ventilator rates. This phenomenon does not occur with the nitrogen/nitric oxide gas mixture mixed at the inlet of the humidifier, using a ventilator with a throughout constant flow at the inspiratory outlet of the ventilator. The fluctuations of the main ventilator circuit flow result in changing ratios of nitrogen/nitric oxide gas mixture and the ventilator gas flow. We speculate this changing flow ratio produces the increase in mean nitric oxide concentration within the ventilatory circuit. To ensure a constant concentration of nitric oxide by blending a nitrogen/nitric oxide gas mixture in the ventilator circuit of a continuous flow ventilator, the site of injection of the nitrogen/nitric oxide gas mixture should be at the point where ventilator circuit flow fluctuations are minimal.

Carbon Dioxide↗
PubMed2002

Battery duration of portable ventilators: effects of control variable, positive end-expiratory pressure, and inspired oxygen concentration.

INTRODUCTION: Portable ventilators require battery power during transport or when alternating current is unavailable. Manufacturers report battery duration at nominal ventilator settings. METHODS: We studied the effects of control variable (pressure control vs volume control), positive end-expiratory pressure (PEEP), and fraction of inspired oxygen (F(IO)(2)) on the battery duration of 8 portable ventilators: Achieva, HT50, iVent201, LTV1000, TBird Advanced Ventilator System (AVS), Avian, Uni-Vent 750, and Uni-Vent 754. Each ventilator was set to ventilate a test lung at a rate of 10 breaths/min, tidal volume of 750 mL, and inspiratory time of 1.5 s, with volume-controlled ventilation and then pressure-controlled ventilation (PCV), if available. F(IO)(2) was set at 0.21 and then 1.0. PEEP was set at 0, 10, and then 20 cm H(2)O. Test lung compliance and resistance were set at 20 mL/cm H(2)O and 5 cm H(2)O/L/s, respectively. Five trials were performed with each portable ventilator, with each combination of settings. Time to low-battery alarm, battery-empty alarm, and failure to ventilate the test lung were recorded. Portable ventilator performance during the trials was determined by continuous recording of tidal volume. RESULTS: The battery duration of pneumatically driven portable ventilators is longer than that of electrically driven portable ventilators. The battery duration of pneumatically driven portable ventilators is minimally affected by ventilator settings. The battery duration of electrically driven portable ventilators is shortened by use of PCV, increasing PEEP, and increasing F(IO)(2). Compared to zero PEEP, PEEP of 20 cm H(2)O reduced battery duration with HT50 (40%), LTV1000 (37%), TBird AVS (34%), and Achieva (15%). Compared to volume-controlled ventilation, PCV reduced battery duration with the LTV1000 (48%) and TBird AVS (18%). Compared to F(IO)(2) of 1.0, F(IO)(2) of 0.21 reduced battery duration with the Uni-Vent 754 (37%). Compared to F(IO)(2) of 0.21, F(IO)(2) of 1.0 reduced battery duration with the LTV1000 (17%) and TBird AVS (15%). The iVent201 was unable to deliver the set tidal volume with PCV and 20 cm H(2)O PEEP. Low-battery alarms functioned properly on all the ventilators. CONCLUSIONS: Battery duration differs greatly among the portable ventilators tested. Clinicians must be aware that portable ventilator battery duration is affected by control settings, lung impedance characteristics, and portable ventilator characteristics. Battery duration may be shorter than that reported in the operator's manual for each portable ventilator tested.

Electric Power Supplies↗
PubMed2026

Alarms and alarm management with automated versus conventional ventilation in neurocritical care patients.

INTRODUCTION: False or clinically irrelevant alarms are a major driver of ICU alarm fatigue and nursing workload. Ventilator alarms make up a large share, and although automated ventilation modes can reduce manual adjustments, their effect on alarm burden is still unclear. This issue can be particularly relevant in neurocritical care patients, where precise ventilator and alarm management is imperative for patient safety. OBJECTIVES: This explorative post hoc analysis of a randomized clinical trial compared alarm frequency and management between automated ventilation and conventional ventilation in neurocritical care patients. METHODS: Ventilator alarms and manual ventilator changes were captured continuously from the ventilator for up to 24&#xa0;h per patient. The primary endpoint was a composite of workload-relevant alarms; with alarm management interventions at the ventilator as a key secondary outcome. Additional endpoints included redundant alarms, alarm duration and ventilator management. RESULTS: 13 patients received automated ventilation and 24 received conventional ventilation. No difference was observed in workload-relevant alarm frequency between automated and conventional ventilation (3.28 [2.87 to 4.30] vs 3.73 [1.66 to 7.33] alarms per hour; P&#xa0;=&#xa0;0.81), while alarm management interventions at the ventilator were lower with automated ventilation (0.14 [0.10 to 0.15] vs 0.21 [0.17 to 0.31] interventions per hour; P&#xa0;=&#xa0;0.01). Other alarm frequencies, duration of alarms and ventilator management were similar. CONCLUSIONS: In this exploratory post hoc analysis of a randomized clinical trial in neurocritical care patients during the early phase of mechanical ventilation, automated ventilation did not reduce the frequency of total or workload-relevant alarms, nor their duration, but was associated with fewer alarm management interventions compared to conventional ventilation. IMPLICATIONS FOR CLINICAL PRACTICE: Automated ventilation may not reduce alarm frequency in neurocritical care patients, but the observed reduction in alarm-related bedside interventions suggests a potential benefit for nursing workload.

Humans↗
PubMed2006

A randomized trial of automated versus conventional protocol-driven weaning from mechanical ventilation following coronary artery bypass surgery.

OBJECTIVE: The Siemens servo 300 A ventilator has an automode function that allows automated weaning of patients from mechanical ventilation. Spontaneous breathing triggers the ventilator. After two spontaneously triggered breaths, the ventilator automatically changes from mandatory mechanical ventilation to spontaneous ventilation. If spontaneous breathing or triggering does not occur, the Siemens servo 300 A ventilator changes from spontaneous ventilation back to mandatory mechanical ventilation. We compared the effects of automated versus conventional protocol-driven weaning on the time until extubation in patients undergoing coronary artery bypass graft (CABG) surgery. In addition, we studied the effects of the mode of weaning on hemodynamic and physiologic parameters. METHODS: Twenty consecutive male patients without respiratory disease scheduled for CABG at the University Hospital of Regensburg were entered into the study. Patients were randomized to postoperative ventilation with the Siemens 300 A/automode ventilator (group A, n = 10) or with the Siemens 300 ventilator (group B, n = 10). All patients were weaned from ventilation according to a standardized protocol. RESULTS: On average, patients in group A were younger and had lower pulmonary artery pressure (PAP) and higher cardiac output compared to patients in group B. However, patients in group A had longer ischemic and bypass times compared to patients in group B. Postoperative use of analgesia and sedation were similar in both groups. Time from tracheal intubation until extubation was 2 h shorter in patients assigned to automode ventilation compared to patients assigned to conventional ventilation (mean time group A 7.9 h, group B 10.0 h; p = 0.069). Peak airway pressure was reduced by 2 cm H2O at the beginning of spontaneous ventilation in group A compared to group B. After extubation, cardiac index showed a greater increase in patients assigned to group A compared to those in group B. CONCLUSIONS: Automode ventilator weaning trended toward more rapid extubation than did conventional protocol-driven ventilation in conjunction with a standardized weaning protocol. Physiologic and hemodynamic factors were better in patients using automode ventilation compared to patients using conventional ventilation. Automode ventilation was well tolerated and did not induce significant adverse effects.

Adult↗
PubMed1996

Total liquid ventilation with perfluorocarbons increases pulmonary end-expiratory volume and compliance in the setting of lung atelectasis.

OBJECTIVE: To compare compliance and end-expiratory lung volume during reexpansion of normal and surfactant-deficient ex vivo atelectatic lungs with either gas or total liquid ventilation. DESIGN: Controlled, animal study using an ex vivo lung preparation. SETTING: A research laboratory at a university medical center. SUBJECTS: Thirty-six adult cats, weighing 2.5 to 4.0 kg. INTERVENTIONS: Heparin (300 U/kg) was administered, cats were killed, and lungs were excised en bloc. Normal lungs and saline-lavaged, surfactant-deficient lungs were allowed to passively collapse and remain atelectatic for 1 hr. Lungs then were placed in a plethysmograph and ventilated for 2 hrs with standardized volumes of either room air or perfluorocarbon. Static pulmonary compliance and end-expiratory lung volume were measured every 30 mins. MEASUREMENTS AND MAIN RESULTS: Reexpansion of normal atelectatic lungs with total liquid ventilation was associated with an 11-fold increase in end-expiratory lung volume when compared with the increase in end-expiratory lung volume observed with gas ventilation (total liquid ventilation 50 +/- 14 mL, gas ventilation 4 +/- 9 mL, p < .0001). The difference was even more pronounced in the surfactant-deficient lungs with an approximately 19-fold increase in end-expiratory lung volume observed in the total liquid ventilated group, compared with the gas ventilated group (total liquid ventilation 44 +/- 17 mL, gas ventilation 2 +/- 8 mL, p = .0001). Total liquid ventilation was associated with an increase in pulmonary compliance when compared with gas ventilation in both normal and surfactant-deficient lungs (normal: gas ventilation 6 +/- 1 mL/cm H2O, total liquid ventilation 14 +/- 4 mL/cm H2O, p < .0001; surfactant-deficient: gas ventilation 4 +/- 1 mL/cm H2O, total liquid ventilation 9 +/- 3 mL/cm H2O, p < .01). CONCLUSIONS: End-expiratory lung volume and static compliance are increased significantly following attempted reexpansion with total liquid ventilation when compared with gas ventilation in normal and surfactant-deficient, atelectatic lungs. The ability of total liquid ventilation to enhance recruitment of atelectatic lung regions may be an important means by which gas exchange is improved during total liquid ventilation when compared with gas ventilation in the setting of respiratory failure.

Animals↗
PubMed2002

Comparison of five bilevel pressure ventilators in patients with chronic ventilatory failure: a physiologic study.

OBJECTIVE: To compare patient-ventilator interaction and comfort in patients with chronic ventilatory failure (CVF) who are undergoing noninvasive positive-pressure ventilation with five different commercial bilevel pressure home ventilators. Also, we wanted to evaluate the short-term effects of the five ventilators on physiologic variables, namely, breathing patterns and inspiratory muscles. DESIGN: Randomized, controlled physiologic study. SETTING: Pulmonary division of a rehabilitation institution. PATIENTS: Twenty-eight patients with CVF due to COPD (17 patients) and restrictive chest wall diseases (11 patients). MEASUREMENTS: Sensation of comfort, breathing patterns and minute ventilation (E), respiratory muscles and mechanics, and patient-ventilator interaction during both unassisted and assisted ventilation with the five ventilators applied randomly. RESULTS: The five ventilators showed different flow and pressure waveforms. The level of comfort was somehow different among the studied ventilators. When compared to unassisted ventilation, all ventilators induced a significant increase in E (p < 0.01) without any significant difference among ventilators. Use of the five ventilators resulted in significant differences in peak airway opening pressure (Pao,peak) but not in mean airway opening pressure computed over a period of 1 min (PTPao,min), and in a duty cycle. Ineffective efforts (IEs) were similar among the studied ventilators. In comparison with unassisted ventilation, all ventilators induced significant reductions in inspiratory muscle effort (p < 0.001). No significant relationship was found between level of comfort and PTPao,min, Pao,peak, or the number of IEs. CONCLUSIONS: In stable, awake patients with CVF, all of the studied ventilators were well-tolerated, although with a great intersubject variability in comfort, and performed well in terms of improvement in E and inspiratory muscle unloading, thus fulfilling the aims of mechanical ventilation. This effect was obtained with similar levels of PTPao,min, despite the fact that Pao,peak was different among some ventilators. The number of IEs was similar among the studied ventilators.

Aged↗
PubMed2006

[Effects of lateral position and independent lung ventilation on unilateral acute lung injury in dogs].

OBJECTIVE: To investigate the effects of conventional ventilation, lateral position, asynchronous independent lung ventilation and synchronous independent lung ventilation on gas exchange, lung mechanics, hemodynamics, pulmonary perfusion and inflammatory mediators in dogs with a hydrochloric acid induced unilateral acute lung injury (ALI). METHODS: Twenty-eight dogs with hydrochloric acid induced unilateral ALI (the left lung) were ventilated with volume controlled ventilation. The animals were divided into four groups. The first group (group A, n = 7) received conventional ventilation in a supine position. The second group (group B, n = 7) received conventional ventilation in the healthy lung dependent position with the parameters as same as group A. The third group (group C, n = 7) received asynchronous independent lung ventilation. The fourth group (group D, n = 7) received synchronous independent lung ventilation with the parameters as same as group C. All the animals were observed for 4 h under the above described ventilation. Oxygenation, lung mechanics, hemodynamics and lung injury score were measured during the ventilation. The right and left pulmonary arterial blood flows were measured after 4 h ventilation. RESULTS: (1) After 30 min ventilation, PaO2/FiO2 in group A [(180 +/- 25) mm Hg, 1 mm Hg = 0.133 kPa] was significantly lower than those in group B, group C and group D [(277 +/- 23), (296 +/- 31), (299 +/- 22) mm Hg respectively, all P < 0.01]. PaO2/FiO2 in group C [(348 +/- 34) mm Hg] and group D [(343 +/- 29) mm Hg] was significantly increased when compared with that of group B [(314 +/- 33) mm Hg] after 60 min ventilation (P < 0.05), but there was no significant difference between group C and group D. (2) After 120 min ventilation, C(st) in group B [(23 +/- 4) ml/cm H2O] significantly increased when compared with that of group A [(19 +/- 2) ml/cm H2O, P < 0.05]. After 60 min ventilation, C(st)-L in group C and group D increased significantly as compared to the beginning of the ventilation. (3) The left lung pulmonary arterial flow in group B, group C and group D [(31.3 +/- 4.6)%, (27.5 +/- 1.3)% and (27.3 +/- 2.8)%, respectively] significantly decreased when compared with that of group A (38.3 +/- 2.2)% after 4 h ventilation (P < 0.05 and P < 0.01). CONCLUSIONS: Both lateral position and independent lung ventilation can improve gas exchange, while independent lung ventilation is better than lateral position ventilation. The improvement of oxygenation may be related to the effect on the distribution of pulmonary arterial flow.

Acute Lung Injury↗