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At least 19 recordsLinked to original sources
PubMed2000

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants.

BACKGROUND: Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although intermittent positive pressure ventilation (IPPV) saves lives, lung distortion during its use is associated with lung injury and chronic lung disease (CLD). Conventional IPPV is provided at 30-80 breaths per minute while a newer form of ventilation called high frequency oscillatory ventilation (HFOV) provides 'breaths' at 10-15 seconds. This has been shown to result in less lung injury in experimental studies. OBJECTIVES: The objective of this review is to determine whether the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation in preterm infants who are mechanically ventilated for the respiratory distress syndrome decreases the incidence of chronic lung disease (CLD) without adverse effects. SEARCH STRATEGY: Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal handsearching by the Cochrane Collaboration, mainly in the English language. Expert informant's search in the Japanese language was made by Prof. Y. Ogawa. SELECTION CRITERIA: Randomized controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who are to be given IPPV. Randomization and commencement of treatment should have been as soon as possible after the start of IPPV and usually in the first 12 hours of life. DATA COLLECTION AND ANALYSIS: The methodological quality of each trial was independently reviewed by the various authors. Each author extracted data separately; they were compared and differences were resolved. The standard method of the Cochrane Neonatal Review Group was used to synthesize the data using relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) for benefits, and number needed to harm (NNH) for adverse effects, were calculated. MAIN RESULTS: Meta-analysis of the six eligible studies comparing HFOV with CV revealed that there is no difference in mortality. There are trends toward decreases in CLD in survivors at 28-30 days, 'death or CLD at 28-30 days' and CLD in survivors at 36-37 weeks postmenstrual age or discharge in the HFOV group. However, there are trends towards increases in severe (grades 3 & 4) intraventricular hemorrhage (IVH) and in periventricular leukomalacia (PVL) in the HFOV group. HFOV results in a small increase in any air leak syndrome (ALS), [summary RR 1.20 (1.03, 1.39)]. Only 2 trials have included neurodevelopmental follow up and more survivors in the HFOV group are abnormal [summary RR 1.26 (1.01, 1.58)]. In the subgroup of four trials where a high volume strategy (HVS) was used, HFOV results in more favourable pulmonary outcomes. There are significantly lower rates of CLD in survivors at 28-30 days [summary RR 0.53 (0.36, 0.76)] and of 'death or CLD at 28-30 days' [summary RR 0.56 (0.40, 0.77) with a non-significant trend towards a reduction in oxygen use at 36-37 weeks postmenstrual age or discharge [summary RR 0.74 (0.55, 1.01)]. There were no differences in the rates of IVH or PVL. Of the four trials in the subgroup using surfactant routinely, three also used the HVS. The trends in results were similar with surfactant to those for the HVS subgroup analysis. One trial suggests that HFOV may reduce the cost of in-hospital care. In the subgroup of two trials (HIFI 1989, Rettwitz-Volk 1998) not using a HVS there is no effect of HFOV on the rate of CLD; however, there is an increase in the rate of PVL [summary RR 1.64 (1.02, 2.64). REVIEWER'S CONCLUSIONS: The overall meta-analyses is dominated by the large HIFI study which did not use the HVS recommended on the basis of animal studies, and in which surfactant was not available. Studies which used HVS have shown some benefits in short term measures of CLD without an in

High-Frequency Ventilation↗
PubMed1994

Demand-flow airway pressure release ventilation as a partial ventilatory support mode: comparison with synchronized intermittent mandatory ventilation and pressure support ventilation.

OBJECTIVE: To evaluate airway pressure release ventilation as a partial ventilatory support mode by comparing a demand-flow airway pressure release ventilation system with synchronized intermittent mandatory ventilation and pressure support ventilation. DESIGN: Prospective, nonrandomized, cross-over trial. SETTING: Medical intensive care unit in a university medical center. PATIENTS: Sixteen consecutive patients without chronic obstructive pulmonary disease with mechanical ventilatory support of 25% to 75% of total minute ventilation on synchronized intermittent mandatory ventilation, or 25% to 75% of maximal pressure support level on pressure support ventilation. INTERVENTIONS: Each mode of mechanical ventilation was supplied to patients with comparable levels of partial support for 30 mins. MEASUREMENTS AND MAIN RESULTS: Among three different modes, demand-flow airway pressure release ventilation achieved the lowest peak airway pressure (airway pressure release ventilation 9.1 +/- 2.6 cm H2O; pressure support ventilation 18.4 +/- 4.6 cm H2O; synchronized intermittent mandatory ventilation 34.8 +/- 7.7 cm H2O; p < .001). Hemodynamic status and oxygenation status were similar among these three modes. Five (31%) of the 16 patients felt that demand-flow airway pressure release ventilation was a less comfortable mode than synchronized intermittent mandatory ventilation or pressure support ventilation. This finding had no clear correlation with their duration of airway pressure release, preset machine deflation rate, or inspiratory/expiratory ratio of machine breath. Gross asynchrony of effort and ventilator cycling was noticed in two (13%) patients while they were receiving demand-flow airway pressure release ventilation. CONCLUSIONS: We conclude that for patients who do not have chronic obstructive pulmonary disease, demand-flow airway pressure release ventilation can provide effective partial ventilatory support with lower peak airway pressure when compared with pressure support ventilation and synchronized intermittent mandatory ventilation. However, this airway pressure release ventilation system may be less comfortable than the other two modes, and asynchrony may occur in some patients.

Analysis of Variance↗
PubMed1989

Inspiratory work and response times of a modified pediatric volume ventilator during synchronized intermittent mandatory ventilation and pressure support ventilation.

Volume ventilation by demand flow ventilators significantly increases work of breathing during inspiration. Although various ventilator modifications and different modes of ventilation have been developed, there have been few studies regarding imposed work of breathing in infants and children. This study was designed to evaluate several modifications of a commercially available demand flow ventilator designed to shorten response time (tr) and decrease the imposed work (Wi) involved in opening the demand valve. Minimum withdrawal volume (Vmin), maximum negative pressure (P mneg), and tr were measured. Wi was defined as the product of Vmin and P mneg. Seven Siemens Servo 900C ventilators were tested under 16 different trial conditions with four variables: 1) mode of ventilation (synchronized intermittent mandatory ventilation [SIMV] vs. pressure support ventilation [PSV]); 2) caliber of circuit tubing (adult vs. pediatric); 3) location of airway pressure monitor (distal vs. proximal); and 4) ventilator trigger sensitivity (0 cm H2O--high vs. -2 cm H2O--low). Vmin, Pmneg, and Wi were all decreased (P less than .05) while tr was unaffected by changing ventilator trigger sensitivity from low to high. Wi was decreased by pediatric tubing and proximal airway pressure monitoring only when low trigger sensitivity was used. PSV and proximal airway monitoring shortened tr. The authors conclude that the use of pediatric circuit tubing and proximal airway pressure monitoring with a Siemens Servo 900C ventilator significantly improved ventilator performance.

Adult↗
PubMed2001

Biphasic-flow induced ventilation allows simultaneous ventilation in several animals, using a single multiple output ventilator--a preliminary report.

Biphasic-flow induced ventilation (BiFIV) is a variable time-cycled tracheal gas insufflation mode, using a specific multiluminal endotracheal tube. Some recent studies have reported efficiency of this new ventilatory mode in experimental in vitro and in vivo settings. We hypothesized that this ventilatory mode could be able to deliver simultaneous efficient ventilation for several animals, using a single ventilator prototype. The study was performed in three groups of three domestic pigs with a normal lung compliance. Each pig was initially anaesthetized, intubated with the specific endotracheal tube, and ventilated with a conventional ventilatory device. The animals were then simultaneously ventilated under BiFIV, using a single ventilator prototype, for each group of three animals. Physiological parameters and arterial blood gases were recorded at each study phase. All animals but one survived the experiment. We did not observe any significant differences in arterial gas exchange, under both ventilatory modes. Oxygenation was as efficient for each three animals ventilated under BiFIV, using a single ventilator device, as under conventional ventilation, using three separate ventilators (PaO2 = 112+/-17 mmHg under conventional ventilation versus 115+/-16 mmHg under BiFIV). In conclusion, variable time-cycled tracheal gas insufflation may allow an efficient multiple ventilation on several animals, using a single multiple output ventilatory device, in a normal lung animal model. If validated on subsequent pathological models, it could thus be interesting in laboratory and/or mass casualty situations.

Animals↗
PubMed1995

Nitrogen dioxide production during mechanical ventilation with nitric oxide in adults. Effects of ventilator internal volume, air versus nitrogen dilution, minute ventilation, and inspired oxygen fraction.

BACKGROUND: Inhaled nitric oxide (NO) may be useful in the treatment of adult respiratory distress syndrome and other diseases characterized by pulmonary hypertension and hypoxemia. NO is rapidly converted to nitrogen dioxide (NO2) in oxygen (O2) environments. We hypothesized that in patients whose lungs are mechanically ventilated and in those with a long residence time for NO in the lungs, a clinically important [NO2] may be present. We therefore determined the rate constants for NO conversion in adult mechanical ventilators and in a test lung simulating prolonged intrapulmonary residence of NO. METHODS: NO (800 ppm) was blended with nitrogen (N2), delivered to the high-pressure air inlet of a Puritan-Bennett 7200ae or Siemens Servo 900C ventilator, and used to ventilate a test lung. The ventilator settings were varied: minute ventilation (VE) from 5 to 25 l/min, inspired O2 fraction (FIO2) from 0.24 to 0.87, and [NO] from 10 to 80 ppm. The experiment was then repeated with air instead of N2 as the dilution gas. The effect of pulmonary residence time on NO2 production was examined at test lung volumes of 0.5-4.0 l, VE of 5-25 l/min, FIO2 of 0.24-0.87, and [NO] of 10-80 ppm. The inspiratory gas mixture was sampled 20 cm from the Y-piece and from within the test lung. NO and NO2 were measured by chemiluminescence. The rate constant (k) for the conversion of NO to NO2 was determined from the relation 1/[NO]t-1/[NO]o = k x [O2] x t, where t = residence time. RESULTS: No NO2 was detected during any trial with VE 20 or 25 l/min. With N2 dilution and the Puritan-Bennett 7200ae, NO2 (< or = 1 ppm) was detected only at a VE of 5 l/min with an FIO2 of 0.87 and [NO] > or = 70 ppm. In contrast, [NO2] values were greater with the Servo 900C ventilator than with the Puritan-Bennett 7200ae at similar settings. When NO was diluted with air, clinically important [NO2] values were measured with both ventilators at high [NO] and FIO2. Rate constants were 1.46 x 10(-9) ppm-2.min-1 when NO was mixed with N2, 1.17 x 10(-8) ppm-2.min-1 when NO was blended with air, and 1.44 x 10(-9) ppm-2.min-1 in the test lung. CONCLUSIONS: [NO2] increased with increased FIO2 and [NO], decreased VE, blending with air, and increased lung volumes. Higher [NO2] was produced with the Servo 900C ventilator than the Puritan-Bennett 7200ae because of the greater residence time. With long intrapulmonary residence times for NO, there is a potential for NO2 production within the lungs. The rate constants determined can be used to estimate [NO2] in adult mechanical ventilation systems.

Adult↗
PubMed2002

Patient-ventilator interactions during partial ventilatory support: a preliminary study comparing the effects of adaptive support ventilation with synchronized intermittent mandatory ventilation plus inspiratory pressure support.

OBJECTIVE: To compare the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation plus pressure support (SIMV-PS) on patient-ventilator interactions in patients undergoing partial ventilatory support. DESIGN: Prospective, crossover interventional study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Ten patients, intubated and mechanically ventilated for acute respiratory failure of diverse causes, in the early weaning period, ventilated with SIMV-PS and clinically detectable sternocleidomastoid activity suggesting increased inspiratory load and patient-ventilator dyssynchrony. INTERVENTIONS: Measurement of respiratory mechanics, P0.1, sternocleidomastoid electromyographic activity, arterial blood gases, and systemic hemodynamics in three conditions: 1) after 45 mins with SIMV-PS (SIMV-PS 1); 2) after 45 mins with ASV, set to deliver the same minute-ventilation as during SIMV-PS; 3) 45 mins after return to SIMV-PS (SIMV-PS 2), with settings identical to those of the first SIMV-PS period. MAIN RESULTS: The same minute ventilation was observed during ASV (11.4 +/- 3.1 l/min [mean +/- sd]) as during SIMV-PS 1 (11.6 +/- 3.5 L/min) and SIMV-PS 2 (10.8 +/- 3.4 L/min). No parameter was significantly different between SIMV-PS 1 and 2, hence subsequent results refer to ASV vs. SIMV-PS 1. During ASV, tidal volume increased (538 +/- 91 vs. 671 +/- 100 mL, p <.05) and total respiratory rate decreased (22 +/- 7 vs. 17 +/- 3 breaths/min, p <.05) vs. SIMV-PS. However, spontaneous respiratory rate increased in six patients, decreased in four, and remained unchanged in one. P0.1 decreased during ASV in all patients except three in whom no change was noted (1.8 +/- 0.9 vs. 1.1 +/- 1 cm H2O, p <.05). During ASV, sternocleidomastoid electromyogram activity was markedly reduced (electromyogram index, where SIMV-PS 1 = 100, ASV 34 +/- 41, SIMV-PS 2 89 +/- 36, p <.02) as was palpable muscle activity. No changes were noted in arterial blood gases, pH, or mean systemic pressure during the trial. CONCLUSION: In patients undergoing partial ventilatory support, with clinical and electromyographic signs of increased respiratory muscle loading, ASV provided levels of minute ventilation comparable to those of SIMV-PS. However, with ASV, central respiratory drive and sternocleidomastoid activity were markedly reduced, suggesting decreased inspiratory load and improved patient-ventilator interactions. These preliminary results warrant further testing of ASV for partial ventilatory support.

Aged↗
PubMed1979

Influence of ventilatory frequencies and ventilator volume/pressure quotients on pulmonary ventilation using a tidal volume ventilator.

The influence of ventilatory frequency and the ventilator's "internal state of gas compression" (Cvent) on mechanics of ventilation, pulmonary ventilation, gas distribution, gas exchange and lung perfusion was studied with free airway and experimental regional airway obstruction in 10 piglets (7-12 kg b. w. ), using a tidal volume ventilator. The VDphy/VTexp ratio was greater at f = 30 than at f = 10.3 cycles/min. This could be related to a significant increase in the VDanat/VTexp ratio at f = 30, while VDc/VTexp and VDlav/VTexp were unchanged at both frequencies. With regional ventilation and perfusion within the obstructed pulmonary field were reduced, compared to the values at f = 10.3 cycles/min. With Cvent 20 ml/kPa, the tidal volumes were insufflated in a shorter time and with a higher initial tracheal peak pressure than with Cvent 80 ml/kPa. Following bronchial obstruction, VA, RQ and Pao2 were greater with Cvent 20 than with Cvent 80 ml/kPa. With Cvent 20, the ventilation of the lung bases was reduced, which was compensated for by a large increase in ventilation within the apical areas of the lungs, while gas distribution within the unobstructed areas was more evenly distributed with Cvent 80. Ventilation at Cvent 20 showed no essential advantage over Cvent 80. Only in lungs extremely difficult to ventilate and with ventilatory frequencies over 50 cycles/min could possible indications for Cvent 20 be seen.

Animals↗
PubMed2000

Comparison of intratracheal pulmonary ventilation and hybrid intratracheal pulmonary ventilation with conventional mechanical ventilation in a rabbit model of acute respiratory distress syndrome by saline lavage.

OBJECTIVES: To study changes in PaCO2 and PaO2 during intratracheal pulmonary ventilation (ITPV) and hybrid intratracheal pulmonary ventilation (h-ITPV) compared with conventional mechanical ventilation (CMV) in a rabbit model of respiratory failure, and to define the technique of h-ITPV that combines conventional mechanical ventilation and ITPV. DESIGN: Prospective, interventional study. SUBJECTS: Twelve adult New Zealand White rabbits. INTERVENTIONS: Surfactant deficiency was induced by saline lavage, and rabbits were randomized to either ITPV or h-ITPV. The study consisted of four phases: phase 0, CMV after saline lavage, ventilator rate 30 breaths/min; phase I, ITPV or h-ITPV initiated at the same pressure and rate as in phase 0; phase II, ITPV or 1.0 L/min h-ITPV bias flow, with peak inspiratory pressure (PIP) decreased and ventilator rate increased to achieve the lowest tidal volume while maintaining adequate gas exchange; and phase III, animals returned to CMV. MEASUREMENTS AND MAIN RESULTS: In phase I, no difference in PaCO2 was observed between ITPV, h-ITPV, or CMV. There was a decrease in PaO2 when switching from CMV to ITPV but not to h-ITPV. In phase II, it was possible to decrease PIP (average of 37% for ITPV and 36% for h-ITPV) and tidal volume (average of 64% for ITPV and 53% for h-ITPV) without compromising gas exchange (p < .05). Oxygenation tended to improve from phase 0 to the end of phase II. In phase III, PaCO2 increased (average of 71% for ITPV and 79% for h-ITPV) and pH decreased (p < .05). Normocapnia was achieved using significantly higher PIP and tidal volume, compared with phase 0 (p < .05). CONCLUSIONS: ITPV and h-ITPV can effectively ventilate and oxygenate rabbits with surfactant-deficient lungs at tidal volumes and therefore pressures lower than required with CMV. Maximum benefit appears to occur at high ventilator rates. These findings suggest that both modes of ventilation may represent powerful new tools in the management of patients with acute respiratory failure. (Crit Care Med 2000; 28:774-781)

Acute Disease↗
PubMed2001

Early high-frequency oscillatory ventilation versus synchronized intermittent mandatory ventilation in very low birth weight infants: a pilot study of two ventilation protocols.

OBJECTIVE: To evaluate the feasibility of conducting a prospective, randomized trial comparing early high-frequency oscillatory ventilation (HFOV) to synchronized intermittent mandatory ventilation (SIMV) in very low birth weight (VLBW) premature infants. This pilot study evaluated two ventilator management protocols to determine how well they could be implemented in a multicenter clinical trial. Although this pilot study was not powered to detect differences in outcome, we also collected outcome data. DESIGN: Prospective, multicenter, randomized pilot study. SETTING: Seven tertiary-level intensive care nurseries with previous experience with both HFOV and flow-triggered SIMV. PATIENTS: Fifty infants weighing 501 to 1200 g, less than 4 hours of age, who had received one dose of surfactant and required ventilation with mean airway pressure > or =6 cm H2O and F(I)O2 > or =0.25, and had an anticipated duration of ventilation greater than 24 hours. INTERVENTIONS: Patients were stratified by birth weight and prenatal steroid status, then randomized to either HFOV or SIMV with tidal volume monitoring. Ventilator management for patients in both study arms was strictly governed by protocols that included optimizing lung inflation and blood gases, weaning strategies, and extubation criteria. MEASUREMENTS: Data were collected using the tools planned for the larger collaborative study. Protocol compliance was closely monitored, with successive changes in the protocol made as necessary to improve clarity and increase compliance. The incidence of major neonatal adverse outcomes was recorded. MAIN RESULTS: Data are presented for 24 HFOV and 24 SIMV infants (two infants, twins, were withdrawn from the study at parent's request). Nineteen of the 24 HFOV infants and 20 of the 24 SIMV infants survived to 36 weeks corrected age. Age at final extubation for survivors was 16+/-16 (mean+/-SD) days for HFOV infants and 24+/-24 days for SIMV infants. At 36 weeks corrected age, 14 of the 19 HFOV survivors were extubated and in room air, whereas 5 required supplemental oxygen. In comparison, 6 of the 20 SIMV survivors were extubated and in room air, whereas 14 required supplemental oxygen. Grade III/IV IVH and/or periventricular leukomalacia occurred in 2 HFOV and 2 SIMV patients. Overall compliance with the ventilator protocols was 82% for the SIMV protocol, and 88% for the HFOV protocol. CONCLUSIONS: The preliminary outcome data supports conducting the large randomized trial, which began in July of 1998. The protocols for the ventilator management of VLBW infants, both with HFOV and with SIMV were easily implemented and consistently followed, and are presented here.

Age Factors↗
PubMed1985

Alternative modes of ventilation. Part I. Disadvantages of controlled mechanical ventilation: intermittent mandatory ventilation.

Controlled mechanical ventilation is an accepted therapy for acute respiratory failure but by virtue of the increase in intrathoracic pressure has a large number of disadvantages. It is to overcome these disadvantages that alternative modes of ventilation have been introduced. These aim to reduce the effects of abnormally high airway pressure on the lung whilst recruiting solid alveoli and at the same time maintaining effective blood volume. Intermittent mandatory ventilation is a mode of ventilation first introduced to aid weaning which may reduce the need for sedation, permit better tolerance of high levels of PEEP and maintain urine osmolar output. High frequency ventilation utilising low airway pressures can maintain pulmonary gas exchange whilst reducing the effects of stretch on the lung. Its major role would seem to be in cases of bronchopleural fistula and necrotising pneumonia where a low mean airway pressure is essential. Low frequency positive pressure ventilation with extra corporeal CO2 removal, whilst a very labour intensive technique, has produced a favourable outcome in patients with terminal respiratory failure. Use of PEEP is associated with further deleterious haemodynamic effects which are largely overcome with use of continuous positive airway pressure during spontaneous respiration. PEEP is widely used. Its effect on pulmonary compliance, dead space and oxygen delivery are unpredictable making haemodynamic monitoring mandatory. Inversed ratio ventilation requires further evaluation whereas differential lung ventilation is logical, complicated but very valuable where the time constants for each lung are significantly different.

Adult↗
PubMed1994

[Ventilation in laryngeal laser-surgical interventions using superimposed high frequency jet ventilation (SHFJV)--a further revision of jet ventilation technique for laryngeal interventions].

In laser surgery of the larynx the surgeon and the anaesthesist have to compete for the limited space available. The surgeon requiring good visibility and an undisturbed operating area whereas the anesthetist has to ensure sufficient ventilation of the patient. Further, complications of anaesthesia and laser must be avoided. These requirements are met by using the jet-tube (jet-laryngoscope) with two integrated nozzles applying simultaneously low- and high-frequency jet-ventilation giving the surgeon total access to the area operated on, and at the same time enables safe ventilation of the patient. Of 334 operations with the tubeless ventilation technique 76 cases were laser surgical interventions. In 6 patients stenoses were enlarged. The average duration of the jet-ventilation was 25 +/- 10 minutes. The maximum duration of a laser surgical intervention was 140 minutes. The age distribution of the patients was 18 months to 82 years. In all patients pulmonary gas exchange was satisfactory. We believe that the advantage of the tubeless jet-ventilation is: optimal visibility and surgical freedom for the surgeon, no time limitation, even in very severe stenoses. Since no volatile anaesthetics or any type of endotracheal tube are applied there is no danger of interaction with the laser when using the SHFJV via the jet-laryngoscope. Application of the tubeless jet-ventilation technique is however limited if patients suffer from severe pulmonary obstruction; likewise highly obese patients and patients in whom massive bleeding occurs are not amenable to tubeless jet-ventilation.

Adult↗
PubMed1995

[Ventilator weaning after long-term ventilation--the concept of a regional ventilator weaning center].

Long-term mechanical ventilation implies a significant number of weaning failures. The basis of this unweanability is chronic fatigue of the inspiratory muscles which is due to depletion of energy store (e.g. glycogen). Considering this pathophysiological principle, the decisive therapeutic option during weaning from long-term mechanical ventilation consists of resting the respiratory muscles. The commonly used assisted ventilation modes only partially relieve the respiratory muscles because the work of breathing is done both during the trigger phase and during the inspiratory cycle. The essential characteristic of our weaning concept includes the repeated determination of the spontaneous breathing frequency in awake patients, which is followed by controlled intermittent positive pressure ventilation with a slightly higher respiratory rate. Ideally, this results in total suppression of the activity of the breathing centre, and in subsequent relief and recovery of the respiratory muscles by replenishing the energy stores. The close succession of relief and training periods avoids inactivity-induced atrophy of the respiratory muscles and permits regeneration. Additionally, our weaning concept avoids increases in inspiratory work during the phases of spontaneous breathing. This means that high-resistance small-caliber endotracheal tubes have to be replaced by large tubes. Moreover, transtracheal oxygen insufflation during spontaneous breathing decreases anatomic dead space. This reduces minute ventilation and, therefore, the work of breathing. In patients still exhibiting chronic fatigue of the respiratory muscle pump after successful weaning, intermittent home ventilation is initiated via a breathing mask. Apart from the concept described above, successful weaning from the respirator after long-term ventilation is based upon dedicated patient care and depends on the architectural characteristics of the intensive care unit.

Breathing Exercises↗
PubMed2000

Conventional gas ventilation, liquid-assisted high-frequency oscillatory ventilation, and tidal liquid ventilation in surfactant-treated preterm lambs.

This study was designed to compare the efficacy and potential protective or injurious effects of tidal liquid ventilation (TLV), liquid-assisted high-frequency oscillatory ventilation (LA-HFOV), and high PEEP conventional mechanical ventilation (CMV) in neonatal respiratory distress syndrome. Preterm lambs (124-126 days gestation), prophylactically treated with natural surfactant, were allocated to one of the treatment modalities or to an untreated fetal control group (F), euthanised after tracheal ligation. LA-HFOV animals received an intratracheal loading dose of 5 mL x kg(-1) followed by a continuous intrapulmonary instillation of 12 mL x kg(-1);h(-1) FC-75 perfluorocarbon liquid. The ventilation strategies aimed at keeping clinically appropriate arterial blood gases for a study period of 5 hours. A histological lung injury score was calculated and semiquantitative morphometry was performed on lung tissue fixed by vascular perfusion. The alveolar-arterial pressure difference for O2 was significantly lower throughout the study in TLV compared to CMV lambs; at 1, 2, and 5 hours, oxygenation was better in TLV when compared to LA-HFOV. Total lung injury scores in TLV lambs were significantly lower than in either CMV or LA-HFOV animals, but higher when compared to F. CMV and LA-HFOV induced an excess of collapsed and overdistended alveoli, whereas in TLV alveolar expansion was normally distributed around predominantly normal alveoli. CMV and LA-HFOV, but not TLV, were associated with an excess of dilated airways. Thus, in the ovine neonatal RDS model, TLV compared favourably to either gas ventilation strategy by its more uniform ventilation, reduced lung injury, and improved gas exchange.

Analysis of Variance↗
PubMed1995

Comparison of the effects of pressure support ventilation delivered by three different ventilators during weaning from mechanical ventilation.

OBJECTIVE: To compare the effects of pressure support ventilation (PSV) delivered at the same level by three different ventilators on patients' work of breathing (WOB), breathing pattern and gas exchange. DESIGN: Prospective, self-controlled clinical study. SETTING: Intensive care unit of a tertiary university hospital. PATIENTS: Nine intubated adult patients during weaning from mechanical ventilation. INTERVENTIONS: Patients were randomly connected to one of three ventilators: the Siemens Servo 900 C (SC), the Ohmeda CPU 1 (CPU), and the Engström Erica (EE) during both zero cmH2O PSV and 15 cmH2O PSV. MEASUREMENTS AND RESULTS: During zero PSV, there was no significant difference in terms of WOB, VT, VE, or auto-PEEP among the three ventilators, although there was a trend towards higher levels of WOB with EE. During 15 cmH2O PSV, WOB was significantly less with SC than with EE or CPU (0.47 +/- 0.48 J/l for SC, 1.0 +/- 0.48 for EE and 0.78 +/- 0.51 for CPU1, p = 0.003). WOB was 64% less than at zero PSV with SC but only 38% less with EE. This was associated with a different pressurization shape, as assessed by the interior surface of Paw-VT loops (1.23 +/- 0.09 J/l for SC, 0.9 +/- 0.02 for EE, and 0.79 +/- 0.18 for CPU; p < 0.001). At 15 cmH2O PSV, auto-PEEP was significantly lower with SC than with EE (1.7 +/- 2.1 cmH2O for SC, 4.7 +/- 3.6 for EE, and 2.8 +/- 0.3 for CPU; p = 0.04). External expiratory resistances, in cmH2O/l/s, were significantly higher with EE than with CPU or SC (12.9 +/- 3.2 EE, 7.5 +/- 2.4 CPU, 5.9 +/- 0.5 SC; p < 0.001). CONCLUSION: During PSV, the different working principles of different mechanical ventilators profoundly affect patient's WOB. Among the various factors, velocity of pressurization of PSV may play a role in its efficacy in unloading the respiratory muscles.

Acute Disease↗
PubMed1994

Diaphragmatic movement studied with ultrasound during spontaneous breathing and mechanical ventilation with intermittent positive pressure ventilation (IPPV) and airway pressure release ventilation (APRV) in man.

Earlier knowledge about diaphragmatic movement during mechanical ventilation is based on radiological information. Since real-time bed-side monitoring is now possible the movement of the right hemidiaphragm was studied using ultrasound (US), both during spontaneous and mechanical ventilation. Nine healthy non-medicated volunteers lying supine were exposed to the following ventilation modes in random order: 1. breathing air at ambient pressure, or 2. at 7.6 mmHg of CPAP or 3. mechanical ventilation with airway pressure release ventilation (APRV), or 4. with IPPV, by mask. The movement of the diaphragm was recorded with a US sector transducer, imaging the ventral, dome and dorsal parts. The maximal movement was detected in the dome in four volunteers during spontaneous breathing with both ambient pressure and CPAP, but in the ventral part in seven and six volunteers, respectively, during APRV and IPPV. Diaphragmatic movement can be studied with US and the findings support the earlier study, with the diaphragm shifting towards the non-dependent regions of the lungs during mechanical ventilation. In this respect APRV is similar to IPPV.

Adult↗
PubMed2003

New modes of mechanical ventilation: proportional assist ventilation, neurally adjusted ventilatory assist, and fractal ventilation.

Increased knowledge of the mechanisms that determine respiratory failure has led to the development of new technologies aimed at improving ventilatory treatment. Proportional assist ventilation and neurally adjusted ventilatory assist have been designed with the goal of improving patient-ventilator interaction by matching the ventilator support with the neural output of the respiratory centers. With proportional assist ventilation, the support is continuously readjusted in proportion to the predicted inspiratory effort. Neurally adjusted ventilatory assist is an experimental mode in which the assistance is delivered in proportion to the electrical activity of the diaphragm, assessed by means of an esophageal electrode. Biologically variable (or fractal) ventilation is a new, volume-targeted, controlled ventilation mode aimed at improving oxygenation; it incorporates the breath-to-breath variability that characterizes a natural breathing pattern.

Algorithms↗
PubMed1999

High-frequency oscillatory ventilation, partial liquid ventilation, or conventional mechanical ventilation in newborn piglets with saline lavage-induced acute lung injury. A comparison of gas-exchange efficacy and lung histomorphology.

It has been reported that, in diseased lungs, either partial liquid ventilation (PLV) or high-frequency oscillatory ventilation (HFOV) can improve oxygenation better and with less lung injury than conventional mechanical ventilation (CMV). This study was intended as a preclinical comparison between the effects of HFOV, PLV and CMV on gas exchange, lung mechanics and histology. Fifteen anesthetized newborn piglets, with respiratory insufficiency due to repeated saline lung lavage, were allocated to either a PLV, HFOV or CMV (n = 5 each) strategy, and treated for 4 h. Within 30 min of commencing therapy, PLV, HFOV, and CMV improved arterial PO2 (Pa,O2), alveoloarterial oxygen gradient (P(A-a),O2), oxygenation index (OI), venous admixture (va), and arterial PCO2 (Pa,CO2). After 4 h, oxygenation parameters (Pa,O2, P(A-a),O2, OI and venous admixture) were significantly better in the HFOV group than in the PLV group; the CMV group showed a higher Pa,O2 and lower OI than the PLV group. Gas exchange at the end of the experiment was not different from baseline in the HFOV and CMV groups. Lung histology and morphometry were performed after perfusion-fixation at endotracheal deflation pressure corresponding to mean airway pressure at the end of the experiment. Lung injury score and mean linear intercept were not different between the three treatment groups. We conclude that in this model, gas exchange improved significantly in all three ventilation strategies. Indices of oxygenation improved less during PLV. The saline lavage-induced acute lung injury model used as in this study, is less stable than previously thought. The final lung injury is not influenced by the ventilation strategy. We speculate that the impaired gas exchange during PLV is an expression of diffusion limitation and ventilation-perfusion mismatch in a recovering lung.

Animals↗