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PubMedDate not supplied

A closed rebreathing system for dose maintenance during Partial Liquid Ventilation.

Partial Liquid Ventilation (PLV), a treatment for acute respiratory failure in which the lungs are filled, either partially or to functional residual capacity (FRC), with perfluorochemical (PFC) liquid while the patient is on mechanical gas ventilation, has progressed to clinical trials using the PFC perflubron (PFB). Because gas expired during PLV is laden with PFB vapor, PFB is lost via evaporation, which increases dose consumption and necessitates periodic redosing. A device has been developed to minimize evaporative loss by confining PFC vapor to a gas volume breathed by the patient, which is isolated from the ventilator. This closed rebreathing system works with the ventilator such that after the lung is filled with PFB, the patient is connected to the rebreathing system, with breathing still "driven" by the ventilator. The rebreathing system consists of two gas circuits, or compartments, separated by a flexible bag (in a box) partition. One compartment is in gas communication with the lung, while the second communicates with the ventilator. The O2 level on the patient side is matched to that on the ventilator side by sensing gas concentrations and by feedback control of O2 introduction. Similarly, air is introduced into the patient side under pressure-based feedback control to maintain a constant gas volume. On inspiration, the ventilator delivers the tidal volume (breath) into the box surrounding the bag, which, in turn, is transmitted through the bag to the lung. On expiration, the process is reversed. Unidirectional circulation of gas in the rebreathing circuit is achieved via check valves, and expired CO2 is removed by a barium hydroxide lime cartridge. Airway humidification is maintained by captive water vapor in the system and water vapor from the CO2 absorber. It is recommended that flow, pressure, O2, and CO2 levels be monitored at the patient "Y," i.e., the proximal end of the endotracheal tube. Performance data from both in-vitro experiments and in-vivo PLV experiments in pigs are presented. The authors conclude that with the closed rebreathing system, the dose can be safely maintained with fewer redosing procedures, and an approximately 90% savings in dose is achieved.

Animals↗
PubMed1999

[Use of noninvasive mechanical ventilation to avoid intubation during acute respiratory insufficiency].

OBJECTIVE: To determine the value of noninvasive mechanical ventilation in patients with acute respiratory insufficiency. DESIGN: Descriptive. METHODS: Noninvasive mechanical ventilation was considered in all patients with acute respiratory insufficiency in the intensive care unit of the Rijnstate Hospital, Arnhem, the Netherlands, between 1 June 1998 and 31 January 1999. Indication for mechanical ventilation was: respiratory frequency > or = 28/min, and PaCO2 > 6.0 kPa, pH < 7.35, and/or PaO2 < 8.0 kPa. Patients were intubated immediately in case of systolic blood pressure < 90 mmHg, cardiac or respiratory arrest, coma or a severely diminished consciousness. The other patients received noninvasive mechanical ventilation by nasal or full face mask (pressure support: 10-20 cmH2O; positive end expiratory pressure (PEEP): 0-5 cmH2O). Patients were intubated if the respiratory frequency or the level of consciousness or a blood gas value deteriorated. RESULTS: Of the 97 patients who needed ventilation support, 67 were immediately intubated. Noninvasive mechanical ventilation was administered in the other 30 (31%) patients, 22 men and 8 women with a mean age of 67 years (SD: 15). Causes for acute respiratory failure were: chronic obstructive pulmonary disease (COPD) (n = 12); pneumonia (n = 6); heart failure (n = 4); and other (n = 8). Median characteristics at baseline in the noninvasive mechanical ventilation group: acute physiology and chronic health evaluation (APACHE) II score: 17 (range: 1-25); respiratory frequency: 30/min (28-59); pH: 7.33 (6.99-7.54); PaCO2: 9.3 kPa (3.2-18.7); PaO2: 7.4 kPa (4.2-13.4); SaO2: 85% (63-95). Intubation was avoided in 9/30 (30%) of all patients and in 7/12 (58%) of the patients with COPD. Intubation was needed in 21/30 patients (70%): in 8/30 (27%) immediately because of clinical deterioration within 2 hours and in 13/30 (43%) after a mean period of stabilisation of 6 hours (2-16). CONCLUSION: Noninvasive mechanical ventilation prevented intubation in over half of the selected patients presenting with acute respiratory failure due to an exacerbation of COPD. The method appears to be less successful in acute respiratory failure due to other causes.

Acute Disease↗
PubMed1999

[Noninvasive ventilation].

Non invasive ventilation is defined as mechanical ventilation without the use of endotracheal intubation and has been increasingly established within intensive care units during the last decades. Negative pressure ventilation and non invasive positive pressure ventilation have been successfully applied, first in chronic respiratory failure (CRF) due to various causes and later in acute respiratory failure (ARF). In this review ventilation modes, indications, contraindications and side effects of non invasive ventilation are analysed and the impact of non invasive ventilation on the physiology, pathophysiology and outcome of CRF and ARF, and possible applications in CRF (restrictive chest and pulmonary diseases, neuromuscular diseases and COPD) and ARF are discussed. It is concluded that non invasive ventilation should be included in the routine management of respiratory failure at all intensive care units.

Acute Disease↗
PubMed2000

Effect of early intervention of high-frequency oscillatory ventilation on the outcome in pediatric acute respiratory distress syndrome.

BACKGROUND: Acute respiratory failure in both pediatric and adult patient populations has been extensively studied with recent emphasis on ventilation strategies that can effect mortality outcome. This research in adults has focused on definitive trials of lung protective strategies that have been proposed following preliminary reports of their potential benefits. High frequency oscillatory ventilation has also been described as a lung protective strategy. For many institutions HFOV is today considered a routine therapy as a "rescue" method in acute pediatric respiratory failure. Because HFOV is considered to be a "rescue" therapy, intervention with HFOV is usually in the later stages of acute respiratory failure and consideration of the time to intervention has not been previously examined. OBJECTIVE: To evaluate the effect of time to intervention with high-frequency oscillatory ventilation (HFOV) on the survival of children with severe acute hypoxemic respiratory failure who were managed with lung protective strategies on conventional mechanical ventilation (CMV). METHODS: Twenty-six consecutive patients older 1 month of age with severe hypoxemic respiratory failure and ARDS who at some point in their management were treated with HFOV were evaluated. The mean age was 3.7 years and included three patients treated in the Pediatric Intensive Care Unit (17, 19 and 24 years). Mean weight was 13.8 kg and there were 17 males and 9 females. Nine patients met Extracorporeal Membrane Oxygenation (ECMO) criteria, although only two patients were cannulated. Upon admission to the PICU, patients were initially managed with lung protective strategies using Pressure Controlled Ventilation (PCV) or Pressure Regulated Volume Control (PRVC) modes with limited peak inspiratory pressure, high positive end-expiratory pressure, and permissive hypercapnia. If a Pa-CO2 reached > 75 torr (10.0 kPa) and/or pH < 7.20, tracheal gas insufflation (TGI) was instituted. If FiO2 remained above 0.6 and mean airway pressure (Paw) exceeded 15 cmH2O in order to maintain arterial saturation above 89% or if hypercapnia and/or acidosis on CMV with TGI persisted, the patients were switched to HFOV. An "Optimal Volume Strategy" with HFOV was utilized to recruit alveoli and optimize lung volume. Patients were returned to CMV when their mean airway pressure were between 15 and 20 cmH2O, FiO2 < 0.6, had no evidence of air-leak and/or improved chest X-rays, and did not desaturated during airway suctioning. Patients were offered ECMO if the hypoxemia persisted on HFOV and there were no contraindications to its use. The patients were stratified for analysis by the time to intervention with HFOV. Early intervention was defined as within the first 24 hours of mechanical ventilation (17 patients) and late intervention defined patients beyond 24 hours (9 patients). Demographic data (gender, age, weight, admission PRISM score), time of each mode of ventilation, oxygenation indices and outcomes were recorded for both groups of patients. MAIN RESULTS: The severity of respiratory failure at the time of HFOV intervention was comparable in both early and late groups (PaCO2/FiO2 83 vs. 79 torr, oxygenation index 27 vs. 33, AaDO2 421 torr (56 kPa) vs. 413 torr (55 kPa)). There were no differences in mean age, weight, admission PRISM score length of HFOV, length of CMV after HFOV (CMV post-HFOV) and the total duration of mechanical ventilation between the groups. We found a statistically significant difference in mortality with 58.8% of the early intervention patients surviving while only 12.5% of the late intervention patients survived. The overall survival rate was 42% (11/26 patients). CONCLUSION: Early use of HFOV within the first 24 hours of acute hypoxic respiratory failure in pediatric patients is associated with better survival. Use of this therapy should be considered early in the course of treatment of any pediatric patient meeting this definition. (Tab. 2, Fig. 1, Ref. 28.)

Adolescent↗
PubMedDate not supplied

[Modalities of mechanical ventilation].

Mechanical ventilation improves the symptoms and reduces complications of acute respiratory failure. Recent advances in microprocessor technology have increased the sophistication of mechanical ventilators, thus leading to new ventilation modalities. This article describes the ventilation modalities available, grouping them as conventional, alternative and new modalities. Conventional ventilation includes the most widely used modalities, alternative ventilation includes less frequently used modalities, and new ventilation modalities include recently introduced options that are available on the latest-generation mechanical ventilators.

Critical Care↗
PubMed2001

[Effects of positive end-expiratory pressure, tidal volume and perflubron doses on gas exchange during partial liquid ventilation].

The efficacy of gas exchange during partial liquid ventilation (PLV) may be affected by positive end-expiratory pressure (PEEP), tidal volume (TV) and perflubron (PFOB) dose. The purpose of the present study was to clarify which factors were important for improving gas exchange during PLV. Fourteen rabbits were anesthetized and tracheostomized. Lung was introduced with intravenous oleic acid combined with saline lung lavage. After obtaining control data, PFOB 7.5 ml.kg-1 was instilled into the trachea, and ventilation settings were changed sequentially [1. TV: 10 ml.kg-1 (mTV), 2. mTV with PEEP, 3. TV: 15 ml.kg-1 (hTV), 4. hTV with PEEP]. PEEP level was set to the lower inflection point. The PFOB dose was increased to 15 ml.kg-1 and measurements were repeated under each ventilation setting. PEEP increased PaO2 in all ventilation settings. In hTV ventilation settings, incremental dose of PFOB significantly increased PaO2. The PaO2 values of all hTV ventilation settings were significantly higher than those of corresponding ventilation setting of mTV. Pulmonary compliance was significantly decreased with PEEP in hTV ventilation in addition to 15 ml.kg-1 PFOB. The results suggested that adequate gas tidal volume was the most important factor for improving gas exchange during PLV. However, PEEP or larger dose of PFOB should be avoided because they may decrease pulmonary compliance.

Animals↗
PubMed2002

[Analysis of the reliability of 4 ventilators used in critically ill patients].

OBJECTIVES: Mechanical ventilators are often used in critically-ill patients with acute respiratory insufficiency. We aimed to assess the reliability of four commonly used ventilators. METHODS: This experimental study assessed four Bio-Tek VT-2 ventilators set for different levels of impedance and compliance in comparison with a tester. We gathered data on differences between the ventilators and the tester for volumes supplied and end-expiratory pressures. Statistical significance was determined using a Student-t test (95% confidence interval) and a coefficient of variation was calculated to study variation over time in parameters programmed. Error margins were calculated and applied for each ventilator. RESULTS: For situations in which compliance and impedance are similar to those of patients with chronic obstructive pulmonary disease and acute respiratory distress syndrome, there were differences in tidal volumes measured by the ventilators monitors and those actually supplied at the end of the breathing circuits, although the differences are only slightly greater than the error margins. The coefficients of variation were not significant at any of the compliance and impedance levels studied. CONCLUSIONS: In situations of low compliance and/or high impedance, tidal volumes supplied by ventilators and volumes shown on the monitors are different, although the differences are small and hardly exceed the ventilators acceptable error margins. The coefficient of variation indicated that the parameters set remain highly stable over time.

Critical Illness↗
PubMed2003

[A meta-analysis of clinical studies of low volume ventilation in acute respiratory distress syndrome].

OBJECTIVE: Pool the published data of randomized-controlled trials (RCTs) about the effect of low volume ventilation in acute respiratory distress syndrome (ARDS) and evaluate if low volume ventilation can reduce the mortality of ARDS. METHODS: MEDLINE and CBM discs from 1991 to 2001 were selected for the data sources. The inclusion criteria were: the subjects were patients with ARDS, the study lasted 10 days or more and was RCT, the mortality of ARDS in low volume ventilation group was compared with that in traditional ventilation group. The data of the studies included were processed with a meta-analysis. RESULTS: 1,435 cases in 7 studies were included, 5 of 7 studies did not show significant different mortalities between the two treatment groups and 2 studies indicated the low volume ventilation could improved the survival of ARDS. The mortalities of ARDS in low tidal volume ventilation group and traditional ventilation group were 35.98% (258/717) and 42.62% (306/718) respectively. The combined OR of all studies was 0.754 (95% CI 0.610 - 0.933), P < 0.01. CONCLUSION: Low volume ventilation benefits the survival of ARDS. It is worth application in clinical practice.

Female↗
PubMed1992

Extrusion rate of Shah and Shepard ventilation tubes in children.

Shah and Shepard ventilation tubes are the two most commonly used ventilation tube in current practice. In some centres these two tubes are used interchangeably, in others the Shepard is often used as the first 'grommet' of insertion and the Shah for subsequent insertions. A study was undertaken of extrusion rate of these ventilation tubes in 180 children who had surgery for Serous otitis media in 1987. Extrusion time was found to be very significantly different between these tubes. The Shah ventilation tube remains in situ 3 months longer than the Shepard. A case is made for the use of Shah ventilation tubes as the first "grommet" of insertion. Otorrhoea following insertion of ventilation tube did not affect the extrusion rate of ventilation tubes in this study. Nor has otorrhoea a predilection for any particular ventilation tube.

Child↗
PubMed2002

[Application value of measurement of the regional pulmonary ventilation by electric impedance pneumograph in the clinical diagnosis of pneumoconiosis].

OBJECTIVE: To study the value of clinical application and distribution character of regional pulmonary ventilation of patients with various type of pneumoconiosis. METHODS: 132 patients with various type of pneumoconiosis were observed by electric impedance pneumograph(EIPV) and routine lung function test. The results were compared with the measured value of 100 healthy cases. RESULTS: The regional pulmonary ventilation of the three kinds of pneumoconiosis(founder's pneumoconiosis, silicosis and asbestosis) was increased in both side of upper pulmonary region and decreased in both of lower pulmonary region. The ventilation distribution showed that the right pulmonary ventilation increased predominantly, accounted for 53.03% (70/132) of total lung ventilation. There was significant difference(P < 0.01) compared with the normal healthy men's EIPV, but no difference(P > 0.05) among various type of pneumoconiosis. There was also no difference(P > 0.05) between pneumoconiosis patients with normal ventilation function and various type of ventilation obstacle of pneumoconiosis. One silicosis patient complicated by atelectasis of the left upper lobe, another silicosis patient complicated by lung cancer and their EIPV accorded with their chest X-rays. CONCLUSION: EIPV could not be measured by routine lung function test. It may be the supplement to latter parameter and as a substitute for radio imaging of pulmonary ventilation in pneumoconiosis complicated by other regional pulmonary disorder.

Electric Impedance↗
PubMed2004

Alarm-enhancement systems for ventilators.

Ventilator alarms can be crucial for safeguarding the health and even the lives of patients. Therefore, it's vital that they--like other critical alarms--be readily detected in even the busiest, noisiest hospital departments. One way to make sure that this happens is to use alarm-enhancement systems, which communicate ventilator alarms to locations where they are more likely to be detected by caregivers. There are four basic categories of ventilator alarm enhancements: (1) interfacing ventilators with networked physiologic monitors, (2) incorporating commercially available systems for centralized remote monitoring of ventilator alarms, (3) interfacing ventilators with nurse call systems, and (4) utilizing remote annunciators for ventilator alarms. These options range widely in complexity, cost, and the types of care settings for which they're likely to be suitable. In this article, we describe the ventilator alarm-enhancement systems that are currently on the market. We highlight their pluses and minuses based on information we have gained from product literature, through conversations with suppliers, and, where possible, through discussions with users. We also provide guidance to facilities on how to choose among the various options and products available.

Decision Making, Organizational↗
PubMed2004

Computer control of mechanical ventilation.

Computer control of mechanical ventilators includes the operator-ventilator interface and the ventilator-patient interface. New ventilation modes represent the evolution of engineering control schemes. The various ventilation control strategies behind the modes have an underlying organization, and understanding that organization improves the clinician's appreciation of the capabilities of various ventilation modes and gives an idea of what we can and should expect for the future. The operator-ventilator interface has received little attention in the literature, despite the fact that there is a whole science of human-computer interaction. This report suggests a methodology for the study of ventilator interfaces.

Artificial Intelligence↗
PubMed2004

Portable/transport ventilators.

Portable ventilators are often used with patients who require long-term breathing support. Current-generation models are compact and lightweight and offer some of the same features that once were available only on costly intensive care ventilators. As technological advances continue to prolong life for critically ill patients and make life possible for both children and adults with otherwise fatal conditions, portable ventilators are helping to make these patients more comfortable and more mobile. They ease the transport of patients within the hospital, and they allow some difficult-to-ventilate patients, especially infants, to receive ventilation at home. In this article, we evaluate three portable/transport ventilators from three suppliers, rating them separately for (1) home care and long-term care applications and (2) in-hospital transport applications. Our ratings place special emphasis on ventilator performance, alarm effectiveness, ease of use, and portability. We found that all the units provide at least satisfactory ventilation, but that their other characteristics vary considerably. For home care and long-term care, we rate two units Acceptable--but one of them is suitable for use only if certain steps related to its alarm volume are taken. The third unit is Not Recommended because of significant drawbacks associated with its ease of use, alarms, and portability. For in-hospital transport, we rate one unit Preferred because it has many features beneficial for transporting critically ill patients. A second unit is Acceptable, while the third is Not Recommended, again because of its many drawbacks.

Ambulatory Care↗
PubMed2005

Reducing ventilation frequency during cardiopulmonary resuscitation in a porcine model of cardiac arrest.

INTRODUCTION: American Heart Association/American College of Cardiology guidelines recommend a compression-to-ventilation ratio (C/V ratio) of 15:2 during cardiopulmonary resuscitation (CPR) for out-of-the-hospital cardiac arrest. Recent data have shown that frequent ventilations are unnecessary and may be harmful during CPR, since each positive-pressure ventilation increases intrathoracic pressure and may increase intracranial pressure and decrease venous blood return to the right heart and thereby decrease both the cerebral and coronary perfusion pressures. HYPOTHESIS: We hypothesized that reducing the ventilation rate by increasing the C/V ratio from 15:2 to 15:1 will increase vital-organ perfusion pressures without compromising oxygenation and acid-base balance. METHODS: Direct-current ventricular fibrillation was induced in 8 pigs. After 4 min of untreated ventricular fibrillation without ventilation, all animals received 4 min of standard CPR with a C/V ratio of 15:2. Animals were then randomized to either (A) a C/V ratio of 15:1 and then 15:2, or (B) a C/V ratio of 15:2 and then 15:1, for 3 min each. During CPR, ventilations were delivered with an automatic transport ventilator, with 100% oxygen. Right atrial pressure, intratracheal pressure (a surrogate for intrathoracic pressure), aortic pressure, and intracranial pressure were measured. Coronary perfusion pressure was calculated as diastolic aortic pressure minus right atrial pressure. Cerebral perfusion pressure was calculated as mean aortic pressure minus mean intracranial pressure. Arterial blood gas values were obtained at the end of each intervention. A paired t test was used for statistical analysis, and a p value < 0.05 was considered significant. RESULTS: The mean +/- SEM values over 1 min with either 15:2 or 15:1 C/V ratios were as follows: intratracheal pressure 0.93 +/- 0.3 mm Hg versus 0.3 +/- 0.28 mm Hg, p = 0.006; coronary perfusion pressure 10.1 +/- 4.5 mm Hg versus 19.3 +/- 3.2 mm Hg, p = 0.007; intracranial pressure 25.4 +/- 2.7 mm Hg versus 25.7 +/- 2.7 mm Hg, p = NS; mean arterial pressure 33.1 +/- 3.7 mm Hg versus 40.2 +/- 3.6 mm Hg, p = 0.007; cerebral perfusion pressure 7.7 +/- 6.2 mm Hg versus 14.5 +/- 5.5 mm Hg, p = 0.008. Minute area intratracheal pressure was 55 +/- 17 mm Hg . s versus 22.3 +/- 10 mm Hg . s, p < 0.001. End-tidal CO(2) with 15:2 versus 15:1 was 24 +/- 3.6 mm Hg versus 29 +/- 2.5 mm Hg, respectively, p = 0.001. Arterial blood gas values were not significantly changed with 15:2 versus 15:1 C/V ratios: pH 7.28 +/- 0.03 versus 7.3 +/- 0.03; P(aCO(2)) 37.7 +/- 2.9 mm Hg versus 37.6 +/- 3.5 mm Hg; and P(aO(2)) 274 +/- 36 mm Hg versus 303 +/- 51 mm Hg. CONCLUSIONS: In a porcine model of ventricular fibrillation cardiac arrest, reducing the ventilation frequency during CPR by increasing the C/V ratio from 15:2 to 15:1 resulted in improved vital-organ perfusion pressures, higher end-tidal CO(2) levels, and no change in arterial oxygen content or acid-base balance.

Animals↗
PubMed2006

Course of weaning from prolonged mechanical ventilation after cardiac surgery.

In order to determine the temporal pattern of weaning from mechanical ventilation for patients undergoing prolonged mechanical ventilation after cardiac surgery, we performed a retrospective review of 21 patients' weaning courses at our long-term acute care hospital. Using multiple regression analysis of an estimate of individual patients' percentage of mechanical ventilator support per day (%MVSD), we determined that 14 of 21 patients (67%) showed a statistically significant quadratic or cubic relationship between time and % MVSD. These patients showed little or no improvement in their ventilator dependence until a point in time when, abruptly, they began to make rapid progress (a "wean turning point"), after which they progressed to discontinuation of mechanical ventilation in a relatively short period of time. The other 7 patients appeared to have a similar weaning pattern, although the data were not statistically significant. Most patients in the study group weaned from the ventilator through a specific temporal pattern that is newly described herein. Data analysis suggested that the mechanism for the development of a wean turning point was improvement of pulmonary mechanics rather than improvement in gas exchange or respiratory load. Although these observations need to be confirmed by a prospective trial, they may have implications for weaning cardiac surgery patients from prolonged mechanical ventilation, and possibly for weaning a broader group of patients who require prolonged mechanical ventilation.

Adult↗
PubMed2006

Mechanical ventilation in patients with Guillain-Barré syndrome.

BACKGROUND: Patients with Guillain-Barré syndrome are commonly exposed to prolonged mechanical ventilation. Specific data on ventilatory management of these patients have been limited. OBJECTIVE: To describe the practice of mechanical ventilation in patients with Guillain-Barré syndrome and evaluate risk factors for morbidity and mortality. METHODS: We describe a historical cohort of mechanically ventilated patients with Guillain-Barré syndrome in a tertiary-care center. We extracted database information on demographics, severity of illness, pulmonary function, and ventilatory management for the period 1976 to 1996. Primary outcomes were development of pulmonary complications, duration of ventilatory support, and mortality. RESULTS: Fifty-four patients met the inclusion criteria. After 1990, lower tidal volume (p = 0.031) and higher positive end-expiratory pressure (p = 0.003) were used than during the 1976 to 1990. Outcomes did not change significantly during the studied period. Forty-six patients (85%) survived to hospital discharge, and 39 (72%) were alive at 1-year follow-up. Ventilator-associated pneumonia was the most frequent complication (56%) and was associated with prolonged mechanical ventilation (p < 0.01). Atelectasis developed in 49%, and acute lung injury in 13%. All but 6 patients (89%) received tracheostomy. In 14 patients (30%) tracheostomy was placed > or = 14 days after intubation. When adjusted for atelectasis and severity of illness in a stepwise logistic regression analysis, delayed tracheostomy was associated with the development of ventilator-associated pneumonia (odds ratio 8.2, p = 0.029). CONCLUSIONS: Changes in ventilator practice did not affect outcomes of mechanically ventilated patients with Guillain-Barré syndrome. The majority of patients received tracheostomy, which should be considered early in the course of respiratory failure.

Adult↗
PubMed1990

[The effect of fresh gas flow on the minute volume of anesthesia ventilators with a gas reservoir].

The tidal volume (TV) delivered by conventional anesthesia ventilators is dependent on fresh gas flow rate (FGF). When FGF is reduced, the TV declines; this must be corrected by increasing the ventilator bellows excursion. In addition, the falling bellows produce a negative pressure during the expiratory phase, which may result in positive negative pressure ventilation (PNPV). We have measured the performance of three ventilators: AV 1 (Dräger), VIVOLEC (Hoyer), and ELSA (Engström) that are equipped with a reservoir bag supplied with fresh gas and from which the bellows is filled. METHOD. Two breathing bags with a corrugated tube of 1 m length were connected to a Y-piece to simulate clinical conditions. Starting from 10 l/min, FGF was decreased by 1 l at a time down to 1.0 l/min. Measurements were made at each level of FGF and also at 0.5, 0.3, and 0.2 l/min using a constant inspiration: expiration ratio of 1:2, displacement of the bellows of 700 ml/breath, and a rate of 10/min. Measurements of peak pressure, positive end-expiratory pressure (PEEP), and delivered TV were made at each FGF setting. RESULTS. The course of TV-dependence on FGF is shown in Fig. 1, that of peak inflation pressure and PEEP in Table 1. Reducing FGF had no effect on TV and inflation pressure with ELSA. VIVOLEC lost 17% of the initial TV when FGF was reduced to 0.2 l/min. By closing the relief valve, the loss of TV could be reduced to 4.5%. AV 1 lost about 10% of the initial TV when FGF was reduced to 0.5 l/min. Peak pressure and PEEP were lower with minimal flow. The reservoir bag collapsed when the plateau pressure exceeded 18-20 mbar. CONCLUSIONS. The TV delivered by the ventilators studied was found to reflect closely what had been preset on the bellows displacement scale, within a range of less than or equal to 17%, irrespective of FGF. Hence, the problem of FGF-dependence of TV is largely negated in anesthesia ventilators equipped with a reservoir bag. With ELSA, there was no loss of TV even under minimal flow conditions. VI-VOLEC (with the relief valve closed) and AV 1 had a loss of less than 10% of the initial TV. Adding a reservoir bag to anesthesia ventilators is an effective method of guaranteeing a TV independent of FGF. The three ventilators tested here proved suitable for minimal-flow anesthesia.

Anesthesiology↗
PubMed1989

[Contamination of respirators in long-term ventilation].

The role of artificial ventilation as an exogenous source of nosocomial pneumonia in long-term ventilated patients is well established. Hence, decontamination of respirators after use is inevitable, although this procedure is costly and time-consuming. The purpose of the study was to prove the efficacy of bacterial filters (Ultipor BB 50, Pall Ltd., Dreieich) in preventing microbial contamination of respirators during long-term ventilation. We investigated the impact of the patient tracheal flora on different parts of the ventilation system. A total of 30 patients included 9 patients treated with an aminoglycoside intratracheally and whose ventilators were equipped with breathing system filters, 10 patients treated with the aminoglycoside intratracheally and without filters, and finally 11 patients without antibiotic prophylaxis and without filters. 1495 samples were taken from different parts of the ventilation circuit. The data obtained suggest that there is no significant influence on the contamination rate of the ventilators by application of bacterial filters or intratracheal aminoglycoside. The use of the breathing system filters to protect the ventilator from microbial contamination, therefore, seems to be unnecessary.

Adolescent↗

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