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  • 1
    Electronic Resource
    Electronic Resource
    An experimental randomized study of six different ventilatory modes in a piglet model with normal lungs (1991)
    Springer
    Intensive care medicine 17 (1991), S. 169-174 
    Details
    ISSN: 1432-1238
    Keywords: Intermittent positive-pressure ventilation ; High-frequency positive-pressure ventilation ; Airway pressures ; N2 wash-out ; Lung clearance index ; Extravascular lung water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A randomized study of 6 ventilatory modes was made in 7 piglets with normal lungs. Using a Servo HFV 970 (prototype system) and a Servo ventilator 900 C the ventilatory modes examined were as follows: SV-20V, i.e. volume-controlled intermittent positive-pressure ventilation (IPPV); SV-20VIosc, i.e. volume-controlled ventilation (IPPV) with superimposed inspiratory oscillations; and SV-20VEf, i.e. volume-controlled ventilation (IPPV) with expiratory flush of fresh gas; HFV-60 denotes low-compressive high-frequency positive-pressure ventilation (HFPPV) and HVF-20 denotes low-compressive volume-controlled intermittent positive-pressure ventilation; and SV-20P denotes pressure-controlled intermittent positive-pressure ventilation. With all modes of ventilation a PEEP of 7.5 cm H2O was used. In the abbreviations used, the number denotes the ventilatory frequency in breaths per minute (bpm). HFV indicates that all gas was delivered via the HFV 970 unit. The ventilatory modes described above were applied randomly for at least 30 min, aiming for a normoventilatory steady state. The HFV-60 and the HFV-20 modes gave lower peak airway pressures, 12–13 cm H2O compared to approximately 17 cm H2O for the other ventilatory modes. Also the mean airway pressures were lower with the HFV modes 8–9 cm H2O compared to 11–14 cm H2O for the other modes. The gas distibution was evaluated by N2 washout and a modified lung clearance index. All modes showed N2 wash-out according to a two-compartment model. The SV-20P mode had the fastest wash-out, but the HFV-60 and HFV-20 ventilatory modes also showed a faster N2 wash-out than the others. Regarding the lung clearance index, the SV-20P, HFV-60 and HFV-20 modes showed better indices than the other modes. No relationship was found between the ventilatory mode and extravascular lung water, and there were no differences in the hemodynamic variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01704722
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  • 2
    Electronic Resource
    Electronic Resource
    Different ventilatory approaches to keep the lung open (1995)
    Springer
    Intensive care medicine 21 (1995), S. 310-318 
    Details
    ISSN: 1432-1238
    Keywords: Intrinsic PEEP ; Respiratory failure ; Pressure-controlled ventilation ; Inverse ratio ventilation ; Functional residual capacity ; Alveolar distension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives To study the ability of different ventilatory approaches to keep the lung open. Design Different ventilatory patterns were applied in surfactant deficient lungs with PEEP set to achieve pre-lavage PaO2. Setting Experimental laboratory of a University Department of Anaesthesiology and Intensive Care. Animals 15 anaesthetised piglets. Interventions One volume-controlled mode (L-IPPV201:1.5) and two pressure-controlled modes at 20 breaths per minute (bpm) and I:E ratios of 2:1 and 1.5:1 (L-PRVC202:1 and L-PRVC201.5:1), and two pressure-controlled modes at 60 bpm and I:E of 1:1 and 1:1.5 (L-PRVC601:1 and L-PRVC601:1.5) were investigated. The pressure-controlled modes were applied using “Pressure-Regulated Volume-Controlled Ventilation” (PRVC). Measurements and results Gas exchange, airway pressures, hemodynamics, FRC and intrathoracic fluid volumes were measured. Gas exchange was the same for all modes. FRC was 30% higher with all post-lavage settings. By reducing inspiratory time MPAW decreased from 25 cmH2O by 3 cmH2O with L-PRVC201.5:1 and L-PRVC601:1.5. End-inspiratory airway pressure was 29 cmH2O with L-PRVC201.5:1 and 40 cmH2O with L-IPPV201:1.5, while the other modes displayed intermediate values. End-inspiratory lung volume was 65 ml/kg with L-IPPV201:1.5, but it was reduced to 50 and 49 ml/kg with L-PRVC601:1 and L-PRVC601:1.5. Compliance was 16 and 18 ml/cmH2O with L-PRVC202:1 and L-PRVC201.5:1, while it was lower with L-IPPV201:1.5, L-PRVC601:1 and L-PRVC601:1.5. Oxygen delivery was maintained at prelavage level with L-PRVC201.5:1 (657 ml/min·m2), the other modes displayed reduced oxygen delivery compared with pre-lavage. Conclusion Neither the rapid frequency modes nor the low frequency volume-controlled mode kept the surfactant deficient lungs open. Pressure-controlled inverse ratio ventilation (20 bpm) kept the lungs open at reduced end-inspiratory airway pressure and hence reduced risk of barotrauma. Reducing I:E ratio in this latter modality from 2:1 to 1.5:1 further improved oxygen delivery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01705409
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  • 3
    Electronic Resource
    Electronic Resource
    Oxygenation remains unaffected by increased inspiration-to-expiration ratio but impairs hemodynamics in surfactant-depleted piglets (1996)
    Springer
    Intensive care medicine 22 (1996), S. 329-335 
    Details
    ISSN: 1432-1238
    Keywords: Pressure-controlled inverse ratio ventilation kwEndinspiratory pressure ; Intrinsic PEEP ; Functional residual capacity ; Hemodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives Prolongation of inspiratory time is used to reduce lung injury in mechanical ventilation. The aim of this study was to isolate the effects of inspiratory time on airway pressure, gas exchange, and hemodynamics, while ventilatory frequency, tidal volume, and mean airway pressure were kept constant. Design Randomized experimental trial. Setting Experimental laboratory of a University Department of Anesthesiology and Intensive Care. Animals Twelve anesthetised piglets. Interventions After lavage the reference setting was pressure-controlled ventilation with a decelerating flow; I∶E was 1∶1, and PEEP was set to 75% of the inflection point pressure level. The I∶E ratios of 1.5∶1, 2.3∶1, and 4∶1 were applied randomly. Under open lung conditions, mean airway pressure was kept constant by reduction of external PEEP. Measurement and results Gas exchange, airway pressures, hemodynamics, functional residual capacity (SF6 tracer), and intrathoracic fluid volumes (double indicator dilution) were measured. Compared to the I∶E of 1∶1, PaCO2 was 8% lower, with I∶E 2.3∶1 and 4∶1 (p≤0.01) while PaO2 remained unchanged. The decrease in inspiratory airway pressure with increased inspiratory time was due to the response of the pressure-regulated volume-controlled mode to an increased I∶E ratio. Stroke index and right ventricular ejection fraction were depressed at higher I∶E ratios (SI by 18% at 2.3∶1, 20% at 4∶1; RVEF by 10% at 2.3∶1, 13% at 4∶1;p≤0.05). Conclusion Under open lung conditions with an increased I∶E ratio, oxygenation remained unaffected while hemodynamics were impaired.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01700455
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  • 4
    Electronic Resource
    Electronic Resource
    Oxygenation remains unaffected by increased inspiration-to-expiration ratio but impairs hemodynamics in surfactant-depleted piglets (1996)
    Springer
    Intensive care medicine 22 (1996), S. 329-335 
    Details
    ISSN: 1432-1238
    Keywords: Key words Pressure-controlled inverse ratio ventilation ; End-inspiratory pressure ; Intrinsic PEEP ; Functional residual capacity ; Hemodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract   Objectives: Prolongation of inspiratory time is used to reduce lung injury in mechanical ventilation. The aim of this study was to isolate the effects of inspiratory time on airway pressure, gas exchange, and hemodynamics, while ventilatory frequency, tidal volume, and mean airway pressure were kept constant. Design: Randomized experimental trial. Setting: Experimental laboratory of a University Department of Anesthesiology and Intensive Care. Animals: Twelve anesthetised piglets. Interventions: After lavage the reference setting was pressure-controlled ventilation with a decelerating flow; I:E was 1:1, and PEEP was set to 75% of the inflection point pressure level. The I:E ratios of 1.5:1, 2.3:1, and 4:1 were applied randomly. Under open lung conditions, mean airway pressure was kept constant by reduction of external PEEP. Measurements and results: Gas exchange, airway pressures, hemodynamics, functional residual capacity (SF6 tracer), and intrathoracic fluid volumes (double indicator dilution) were measured. Compared to the I:E of 1:1, PaCO2 was 8% lower, with I:E 2.3:1 and 4:1 (p≤0.01) while PaO2 remained unchanged. The decrease in inspiratory airway pressure with increased inspiratory time was due to the response of the pressure-regulated volume-controlled mode to an increased I:E ratio. Stroke index and right ventricular ejection fraction were depressed at higher I:E ratios (SI by 18% at 2.3:1, 20% at 4:1; RVEF by 10% at 2.3:1, 13% at 4:1; p≤0.05). Conclusion: Under open lung conditions with an increased I:E ratio, oxygenation remained unaffected while hemodynamics were impaired.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01700455
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  • 5
    Electronic Resource
    Electronic Resource
    An experimental randomized study of five different ventilatory modes in a piglet model of severe respiratory distress (1992)
    Springer
    Intensive care medicine 18 (1992), S. 339-347 
    Details
    ISSN: 1432-1238
    Keywords: Respiratory failure ; Lung lavage ; Pressure-controlled ventilation ; Inverse ratio ventilation ; High frequency ventilation ; Functional residual capacity ; Extravascular lung water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objectives: To characterize different modes of pressure- or volume-controlled mechanical ventilation with respect to their short-term effects on oxygen delivery (DO2). Furthermore to investigate whether such differences are caused by differences in pulmonary gas exchange or by airway-pressure-mediated effects on the central hemodynamics.Design: After inducing severe respiratory distress in piglets by removing surfactant, 5 ventilatory modes were randomly and sequentially applied to each animal.Setting: Experimental laboratory of a university department of Anesthesiology and Intensive Care.Animals: 15 piglets after repeated bronchoalveolar lavage.Interventions: Volume-controlled intermittent positive-pressure ventilation (IPPV) with either 8 or 15 cmH2O PEEP; pressure-controlled inverse ratio ventilation (IRV); pressure-controlled high-frequency positive-pressure ventilation (HFPPV) and pressure-controlled high frequency ventilation with inspiratory pulses superimposed (combined high frequency ventilation, CHFV). The prefix (L) indicates that lavage has been performed.Measurements and results: Measurements of gas exchange, airway pressures, hemodynamics, functional residual capacity (using the SF6 method), intrathoracic fluid volumes (using a double-indicator dilution technique) and metabolism were performed during ventilatory and hemodynamic steady state. The peak inspiratory pressures (PIP) were significantly higher in the volume-controlled low frequency modes (43 cmH2O for L-IPPV-8 and L-IPPV-15) than in the pressure-controlled modes (39 cmH2O for L-IRV, 35 cmH2O for L-HFPPV and 33 cmH2O for L-CHFV, with PIP in the high-frequency modes being significantly lower than in inverse ratio ventilation). The mean airway pressure (MPAW) after lavage was highest with L-IRV (26 cmH2O). In the ventilatory modes with a PEEP〉8 cmH2O PaO2 did not differ significantly and beyond this “opening threshold” MPAW did not further improve PaO2. Central hemodynamics were depressed by increasing airway pressures. This is especially true for L-IRV in which we found the highest MAPW and at the same time the lowest stroke index (74% of IPPV).Conclusions: In this model, as far as oxygenation is concerned, it does not matter in which specific way the airway pressures are produced. As far as oxygen transport is concerned, i.e. aiming at increasing DO2, we conclude that optimizing the circulatory status must take into account the circulatory influence of different modes of positive pressure ventilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01694362
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