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PubMed1993

Alterations in feline tracheal permeability after mechanical ventilation.

OBJECTIVES: Previous investigations of ventilator-induced airway injury focused on histopathologic changes associated with various ventilators and strategies for their use. We hypothesized that mechanical ventilation is associated with alterations in tracheal epithelial permeability, and designed a study using an animal model to evaluate changes in tracheal epithelial permeability after administering different types of mechanical ventilation to test this hypothesis. DESIGN: Prospective, multiple-group, controlled trial. Five groups of animals were studied and compared. Eight animals were studied without intubation or mechanical ventilation. A total of 28 animals (seven in each group) were studied after conventional mechanical ventilation, high-frequency positive-pressure ventilation, high-frequency jet ventilation, or high-frequency flow interruption at respiratory rates of 20, 150, 400, and 900 breaths/min, respectively. Comparison of data for each group was done using the Kruskall-Wallis analysis of variance. Between-group comparisons were made using standard error of the mean comparisons. For airway pressures and other physiologic data, one-way analysis of variance was performed. Between-group comparisons were made using the Student-Newman-Keuls' test. SETTING: Small animal physiology laboratory. SUBJECTS: Thirty-six adult cats. INTERVENTIONS: Mechanically ventilated animals were treated for 8 hrs and then killed. Inspired oxygen concentration, BP, and mean airway pressures were comparable in mechanically ventilated animals. Spontaneously breathing control animals were killed without endotracheal intubation or exposure to mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: Permeability values in isolated tracheal segments were calculated for 14C-sucrose, 3H-inulin, and fluorescein isothiocyanate-dextran-20. Tracheal epithelial permeability to all studied molecules increased after exposure to mechanical ventilators. These different mechanical ventilators increased epithelial permeability in a progressive manner that paralleled ventilatory frequency. The changes were greatest after ventilation at the highest frequency. These observed changes in tracheal permeability are consistent with previously observed alterations in tracheal histopathology after exposure to mechanical ventilation. CONCLUSIONS: Mechanical ventilation was associated with increases in tracheal permeability to large and small nonionic molecules. These changes occurred with all studied ventilators, used as they are clinically. Permeability changes paralleled ventilatory rate changes.

Animals↗
PubMed2001

Evaluation of the Pneupac Ventipac portable ventilator in critically ill patients.

We assessed adequacy of ventilation in 20 critically ill patients with multiple organ failure using a Pneupac Ventipac portable ventilator and the effects on patients' haemodynamic stability. Baseline data were recorded over 15 min for a range of respiratory, haemodynamic and oxygen transport variables during ventilation with a standard intensive care ventilator (Engström Erica). Patients were then ventilated for 40 min using the portable ventilator. Finally, they were ventilated for a further 40 min using the standard intensive care ventilator. Heart rate, arterial and pulmonary artery pressures were recorded at 5-min intervals throughout the study period. Cardiac index and other haemodynamic data derived from a pulmonary artery catheter were recorded at 20-min intervals. Blood gas analysis was performed and oxygen transport data (oxygen delivery, oxygen consumption and physiological shunt) were calculated at the end of each of the three periods of ventilation. In general, no significant adverse effects of ventilation using the portable ventilator were observed for any of the variables studied. Arterial PO(2) increased significantly during ventilation with the portable ventilator, reflecting the use of a higher inspired oxygen fraction during this part of the study. Oxygen consumption decreased significantly in one patient during ventilation by the portable ventilator although none of the other variables measured in this patient was altered. We conclude that ventilation of critically ill patients using the Pneupac Ventipac portable ventilator was safe, satisfactory and associated with minimal adverse effects on respiratory, haemodynamic and oxygen transport variables.

Aged↗
PubMed1992

Experimental study of high-frequency two-way jet ventilation.

BACKGROUND AND METHODS: A new mode of jet ventilation, high-frequency two-way jet ventilation, was devised and introduced to increase CO2 elimination. High-frequency two-way jet ventilation was achieved by adding reverse jet pulses inside the trachea through an intratracheal reverse jet system to the expiratory phase of common high-frequency jet ventilation. The ventilatory efficiency and features of high-frequency two-way jet ventilation were investigated and compared with those features of high-frequency jet ventilation in ten dogs in the same experimental condition. Random sample selection and randomized crossover trial were used for comparison between high-frequency two-way jet ventilation and high-frequency jet ventilation. Peak inspiratory pressure, end-expiratory pressure, and the arterial blood gas variables (PaO2, PaCO2, and pH) were measured during the study. RESULTS: PaCO2 with high-frequency two-way jet ventilation was about 35% lower than that with high-frequency jet ventilation (from 45 to 29 torr [6.0 to 3.9 kPa], p less than .01). Simultaneously, peak inspiratory pressure and end-expiratory pressure during high-frequency two-way jet ventilation were significantly lower than those same variables measured during high-frequency jet ventilation. End-expiratory pressure of high-frequency two-way jet ventilation was a negative pressure (-2.45 +/- 0.45 cm H2O). The pH of high-frequency two-way jet ventilation was significantly higher than that of high-frequency jet ventilation. CONCLUSIONS: Compared with high-frequency jet ventilation, high-frequency two-way jet ventilation demonstrated a ventilatory feature of increasing CO2 elimination and simultaneously decreasing airway pressure.

Animals↗
PubMed2000

Weaning injured patients with prolonged pulmonary failure from mechanical ventilation in a non-intensive care unit setting.

BACKGROUND: Injured patients with pulmonary failure often require prolonged length of stay in an intensive care unit (ICU), which includes weaning from ventilatory support. In the last decade, noninvasive ventilation modes have been established as safe and effective. One method for accomplishing this mode of ventilation uses a simple bilevel ventilator. Because this ventilator has been successfully used in hospital wards, we postulated that bilevel ventilators could provide sufficient support during weaning from mechanical ventilation of injured patients in a non-ICU setting. METHODS: A retrospective review of trauma patients (August 1996-January 1999) undergoing bilevel positive pressure ventilation as the final phase of weaning was conducted. Before ward transfer with bilevel ventilation, conventionally ventilated ICU patients were changed to bilevel ventilation and were required to tolerate this mode for at least 24 hours. All patients had a tracheostomy as a secure airway. Outcomes analyzed included ICU length of stay, hospital length of stay, duration of mechanical ventilation, weaning success, complications, and survival. RESULTS: Fifty-one patients (39 men, 12 women) with a mean age of 53 received more than 24 hours of bilevel positive pressure ventilation. Mean Injury Severity Score was 29, with blunt mechanisms of injury occurring in 90%. Chest or spinal cord injuries that affected pulmonary mechanics were present in 75% of patients. Ventilator-associated pneumonia was treated in 43% of patients. Mean ICU length of stay and hospital length of stay were 21 and 34 days, respectively. Weaning was successful in 89% of patients, whereas 11% were discharged to skilled nursing facilities still receiving bilevel positive pressure ventilation. Two patients died, neither from a pulmonary nor airway complication. Of the remaining 49 patients, 12 were weaned in the ICU and 37 were transferred to the ward with bilevel ventilatory support. The average length of ward ventilation was 6.5 +/- 5.4 days (n = 37). CONCLUSIONS: Implementation of a program using bilevel ventilation to support the terminal phase of weaning seriously injured patients from mechanical ventilation was successful. After initiating this mode in the ICU, it was satisfactorily continued in standard surgical wards. Because this method enabled the withdrawal of ventilatory support in a non-ICU setting, its major advantage was reducing ICU length of stay.

Adolescent↗
PubMed2003

Effect of helium-oxygen (heliox) gas mixtures on the function of four pediatric ventilators.

OBJECTIVE: To evaluate the effects of helium on the function of four ventilators commonly used in pediatrics: the Bird VIP, Bird VIP Gold, Servo 300, and Servo 900C. DESIGN: Prospective setting. SETTING: Research laboratory at a university hospital. SUBJECTS: Helium was administered as an 80:20 mixture of helium-oxygen through the air inlet of the ventilator. Delivered fraction of inspired oxygen (Fio(2)) was compared with the Fio(2) set on the blender dial. Inspiratory displayed tidal volume was recorded as an indicator of what the ventilator "believed" it had delivered and was compared with the V(T) displayed during ventilation with 100% oxygen (control). Actual delivered V(T) was measured by a Neonatal Bicore connected to the side port of a "bag-in-box" spirometer, making measurements independent of inspired gas properties, and was compared with V(T) delivered during ventilation with 100% oxygen. INTERVENTIONS: Five gas mixtures were evaluated: Fio(2) = 0.2, 0.4, 0.6, 0.8, and 1.0 (balance helium). MEASUREMENTS AND MAIN RESULTS: Delivered Fio(2) was less than set Fio(2) on the Servo 900C and VIP ventilators. V(T) displayed was minimally altered by helium during volume-controlled ventilation but substantially decreased during pressure-controlled ventilation, particularly with the Bird ventilators. During volume-controlled ventilation, V(T) delivered was substantially increased by helium with the Bird and, to a lesser degree, the Servo 900C ventilators. In contrast, V(T) delivered decreased slightly in helium with the Servo 300. The same pattern, but with a decreased magnitude, was observed for V(T) delivered during pressure-controlled ventilation. CONCLUSIONS: The addition of helium has a significant effect on Fio(2) delivery, displayed inspiratory V(T), and actual delivered V(T) during both volume- and pressure-controlled ventilation in four ventilators commonly used in pediatric critical care. These effects are both ventilator specific and ventilation mode specific, mandating vigilance during helium ventilation in clinical practice.

Air Pressure↗
PubMed1980

Cost of operation and reliability of two brands of volume ventilators.

Maintenance records during 12 months for 16 MA-1 ventilators, 7 BEAR-1 ventilators more than one year old, and 6 new BEAR-1 ventilators were compared. The MA-1 ventilators had the best record in every important category except cost for accessory parts and ventilator cost per patient hour with retrofit and preventive maintenance. The MA-1 ventilators needed repair once every 8,329 hours of use, compared with once every 2,500 hours for older BEAR-1 ventilators and once every 4,277 hours for newer BEAR-1 ventilators. Total costs of repairs were $430.84 for 16 MA-1 ventilators, and $3,064.44 for 7 BEAR-1 ventilators out of warranty. Costs of replacement parts were $3,097.01 for the MA-1 ventilators, $986.21 for the older BEAR-1 ventilators, and $845.32 for the newer BEAR-1 ventilators. The total cost per patient hour of use was 11 for the MA-1 ventilators and 13 and 3 respectively for the two BEAR-1 groups. Adding costs for retrofit for the MA-1 ventilators and projected costs for preventive maintenance of the BEAR-1 ventilators tripled the cost per hour of use for all three groups. The frequency of breakdowns for both brands of ventilators underlines the need for preventive maintenance, but substantial cost increases will result from those programs.

Costs and Cost Analysis↗
PubMed2004

[Bacterial colonization and home mechanical ventilation: prevalence and risk factors].

OBJECTIVE: To investigate the prevalence of bacterial contamination of ventilators and colonization of patients, the bacteria implicated, and predisposing factors in noninvasive home ventilation. MATERIAL AND METHODS: Forty patients on a home noninvasive ventilation program (mean [SD] age: 63.1 [12] years; time on ventilation: 30.7 [25] months; daily use: 8.1 [2] hours) were enrolled in this descriptive cross-sectional study. Microbiological samples for semiquantitative cultures were swabbed from the ventilator (mask and tubing) and the nostrils. A questionnaire was completed on the underlying disease, time on the ventilation program, type of ventilator, presence of a humidifier, and attention to ventilator cleanliness and maintenance. We defined "colonization" as the presence of microorganisms in the nostrils without evidence of a host immune response, and "contamination" as the presence of surface microorganisms (on tubing or the nasal mask). RESULTS: Potentially pathogenic bacteria were isolated from 6 ventilators (15%) and the nasal swabs of 10 patients (25%). Staphylococcus aureus was the most frequently isolated one (in 5 ventilators and 6 patients--contamination coinciding with colonization in 3 cases). Other potentially pathogenic bacteria isolated were Proteus species (from the nostrils of 2 patients) and an unidentified gram-negative bacillus from the ventilator. On analysis by underlying disease, 60% of the patients with obesity had been colonized. No other findings of note were obtained for other diseases. Contamination and colonization correlated with attention to cleanliness and maintenance of the ventilator but not with type of ventilator, time on the ventilation program, or use of a humidifier. CONCLUSIONS: Home mechanical ventilators are a potential source of nasal colonization. The most frequently encountered microorganism was S. aureus. The degree of ventilator cleaning and disinfection seems to affect contamination; thus it is necessary to impress on patients the need for adequate maintenance of their ventilators.

Adult↗
PubMed2003

[New modalities of mechanical ventilation].

In the last few years new mechanical ventilation modalities have been developed that aim to improve the characteristics of mechanical ventilation and its adaptation to the patient. Volume-programmed and pressure-controlled ventilation (volume-controlled pressure-adjusted, adaptable pressure ventilation, autoflow ventilation) attempt to combine the advantages of volume and pressure ventilation by controlling volume but with decelerated flow. These types of ventilation can be programmed in controlled, assisted, intermittent mandatory ventilation, or support ventilation mode. Other modalities offer pressure ventilation with continuous flow during the respiratory cycle (BIPAP, DUOPAP, APRV) and allow the patient to breathe spontaneously. Some ventilators have new modalities (adaptable support ventilation) that calculate the best minute ventilation according to the patient's weight and the level of support required. The ventilator provides support according to spontaneous respiratory frequency and tidal volume. Other modalities (proportional assist ventilation) provide support according to the patient's respiratory efforts. These new modalities can improve the adaptation of mechanical ventilation to the patient. None of these modalities are superior to the others. The choice of ventilation mode should be individualized according to each patient's characteristics.

Child↗
PubMed2004

[Prevalence of mechanical ventilation in pediatric intensive care units in Spain].

OBJECTIVE: To study the prevalence and characteristics of mechanical ventilation in children admitted to Spanish pediatric intensive care units (PICU). MATERIAL AND METHODS: A prospective, multicenter, observational study was performed using a written questionnaire sent to the 46 PICUs in Spain. Clinical data and mechanical ventilation settings in patients undergoing mechanical ventilation on 19th February 2002 were collected. RESULTS: Thirty-three PICUs participated in the study (27 had patients undergoing mechanical ventilation on the study day). The prevalence of mechanical ventilation was 86 patients (45.5 %). The mean age of patients undergoing mechanical ventilation was 36 months and the median was 8 months. Sixty percent of the patients were boys. The main indications for mechanical ventilation were acute respiratory failure (46.5 %), chronic respiratory failure (10.4 %), coma (11.6 %) and postoperative status (10.5 %). Endotracheal tubes were used in 73.2 % and a tracheostomy tube was used in 23.2 %. The most frequent mechanical ventilation modalities used were synchronized intermittent mandatory ventilation (SIMV) in 43 % and control or assisted-control ventilation in 36 %. In 30 % of the patients the duration of mechanical ventilation was longer than 1 month. From the initiation of mechanical ventilation to the study day, pneumothorax developed in 8.1 % of the patients, accidental extubation occurred in 10.5 % and ventilator-associated pneumonia developed in 17.4 %. CONCLUSIONS: A high percentage of children admitted to the PICU requires mechanical ventilation. The most frequent indication is respiratory failure. The most frequently used modality in children aged less than 1 month is pressure SIMV. In children older than 1 month volume-cycled or pressure-limited ventilation and volume-cycled SMIV are used in similar proportions. The prevalence of prolonged mechanical ventilation and the incidence of ventilator-associated complications are very high.

Child↗
PubMed2006

Pressure-controlled versus volume-controlled one-lung ventilation for MIDCAB.

One-lung ventilation is limited by hypoventilation and hypoxemia because of increasing airway pressure and intrapulmonary shunt. Previous clinical studies compared pressure-controlled versus volume-controlled ventilation during one-lung ventilation in patients with pre-existing pulmonary disease. We studied 50 patients undergoing thoracotomy and one-lung ventilation because of cardiovascular disease. After two-lung ventilation with volume-controlled ventilation, patients were divided randomly into two groups. In one group, ventilation was switched to pressure-controlled ventilation after starting one-lung ventilation. In the other group, volume-controlled ventilation was continued. Parameters of ventilation, pulmonary function and systemic and pulmonary hemodynamics were recorded. We observed, that peak airway pressure, dead space ventilation and arterial carbon dioxide partial pressure were significantly higher during volume-controlled ventilation. After one-lung ventilation patients with pressure controlled ventilation had lower alveolar-arterial oxygen tension difference and a higher arterial oxygen partial pressure with significant differences for those patients in the intensive care unit. We conclude that pressure-controlled ventilation may be useful to improve gas exchange and alveolar recruitment during one lung ventilation.

Coronary Artery Bypass↗
PubMed1994

Randomized, prospective trial of pressure-limited versus volume-controlled ventilation in severe respiratory failure.

OBJECTIVE: Volume-controlled ventilation is frequently chosen as the initial mode of ventilatory support in patients with hypoxic respiratory failure. Recent data, however, suggest that pressure-limited ventilation, using a rapidly decelerating flow delivery pattern, may produce a more desirable clinical effect through reduced peak airway pressures and increased static compliance, tissue oxygen delivery, and consumption. This study was performed to assess the feasibility and utility of early and sustained use of pressure-limited ventilation in patients with this clinical syndrome. DESIGN: Randomized, prospective trial. SETTING: Medical intensive care unit (ICU) of a university hospital. PATIENTS: The study encompassed all patients (n = 27) receiving care in a medical ICU for acute, severe hypoxic respiratory failure (PaO2/FIO2 ratio of < 150) during a 6-month period. INTERVENTIONS: Ventilatory support via either pressure-limited or volume-controlled ventilation, initiated within 24 hrs of endotracheal intubation. MEASUREMENTS: On-line monitoring of the following ten ventilatory variables at 1-min intervals for 72 hrs or until extubation or death (maximum of 43,200 data points per patient): peak airway pressure, mean airway pressure, end-tidal CO2 concentration, CO2 minute excretion, inspiratory tidal volume, expiratory tidal volume, pause pressure, end-expiratory pressure, static thoracic compliance, and inspiratory resistance. Additionally, PaO2/FIO2 values and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were recorded on a daily basis, as were significant clinical events and changes in ventilator settings. RESULTS: Although the severity of illness at study entry as determined by APACHE II score and PaO2/FIO2 was similar in patients treated with pressure-limited or volume-controlled ventilation, peak airway pressure was consistently lower in patients randomized to pressure-limited ventilation (p = .05 at 12 hrs postintubation). The use of pressure-limited ventilation also was associated with a more rapid increase in static compliance (p = .05) than that found with volume-controlled ventilation. There was a trend toward more rapid normalization of CO2 minute excretion in patients treated with pressure-limited ventilation. Pressure-limited treated patients who survived their illness and were extubated, required fewer days of mechanical ventilation than did patients randomized to volume-controlled treated ventilation (p = .05). No pneumothoraces occurred in any study patients. One volume-controlled patient developed subcutaneous emphysema. Pressure-limited ventilation was well tolerated, and sedation requirements were equivalent in the two groups. CONCLUSIONS: Pressure-limited ventilation can be used safely and is well tolerated as an initial mode of ventilatory support in patients with acute hypoxic respiratory failure. Because the early initiation of pressure-limited ventilation is associated with lower peak airway pressure and more rapid improvement in static thoracic compliance than volume-controlled ventilation, pressure-limited ventilation may have a beneficial role when used as the primary ventilatory modality in patients with this clinical condition.

Adult↗
PubMed2002

How patients feel about prolonged mechanical ventilation 1 year later.

OBJECTIVES: To elicit mechanical ventilation preferences among patients who previously received prolonged (>/=48 hrs) mechanical ventilation, to identify patient characteristics associated with mechanical ventilation preferences, and to assess the association between the intensive care experience and mechanical ventilation preferences. DESIGN: Prospective cohort study conducted between June of 1997 and July of 2000. SETTING: Four intensive care units at a tertiary care institution. PATIENTS: Former critically ill patients (n = 133; mean age +/- sd, 51.8 +/- 17.1 yrs; 49% women) who survived for 12 months after prolonged mechanical ventilation. MEASUREMENTS: Patients' preferences toward their actual mechanical ventilation experiences, by asking patients to reflect on the decision to apply mechanical ventilation made 1 yr earlier. Preferences for hypothetical situations, by asking patients to evaluate mechanical ventilation choices, assuming that their experiences had been different in terms of pain or discomfort, familial financial burden and stress, and health status after mechanical ventilation. RESULTS: Of the 133 patients, 115 (86.5%) would have chosen mechanical ventilation, with younger and healthier patients having higher odds of choosing mechanical ventilation than older and sicker patients, respectively. One fourth of patients who initially would have chosen mechanical ventilation would have refused this therapy had their families' financial burdens been beyond certain thresholds. A similar proportion would have refused mechanical ventilation with greater mechanical ventilation pain or discomfort. CONCLUSION: Although most subjects would have made the same decision to receive mechanical ventilation, younger and healthier subjects were most likely to favor mechanical ventilation. Many patients indicated that factors such as the amount of pain or discomfort from mechanical ventilation and their families' financial burden would cause them to refuse this potentially life-saving intervention.

Adolescent↗
PubMed2006

Transtracheal open ventilation in acute respiratory failure secondary to severe chronic obstructive pulmonary disease exacerbation.

RATIONALE: Patients who fail noninvasive ventilation are generally intubated and are then subjected to complications of invasive mechanical ventilation. With transtracheal open ventilation, ventilator support is delivered through an uncuffed small bore minitracheostomy tube, which eliminates pooling of secretions above the cuff and thus reduces the risk of tracheobronchial microbial colonization. OBJECTIVE: To compare transtracheal open ventilation (treatment group) with conventional invasive ventilation (control group) in patients with exacerbation of chronic obstructive pulmonary disease who initially failed noninvasive ventilation. METHODS: Patients were randomized to receive trans-tracheal open ventilation (n=19) or conventional invasive ventilation (n=20). MEASUREMENTS AND MAIN RESULTS: There was no difference in arterial blood gases after 1 and 30 h between the two groups. Two patients receiving transtracheal open ventilation and 13 undergoing conventional ventilation had complications (p<0.0001). Compared with conventional ventilation, transtracheal open ventilation significantly decreased both the duration of mechanical ventilation (7.6+/-4.7 vs. 18.6+/-10.6 d, p<0.0001) and length of stay in the intensive care unit (10.2+/-4.5 vs. 21.3+/-9.7 d, p<0.0001). CONCLUSIONS: Transtracheal open ventilation was as effective as conventional ventilation in maintaining adequate gas exchange and reducing complications, duration of mechanical ventilation, and intensive care unit length of stay.

Acute Disease↗
PubMed2000

Neonatal assisted ventilation: predictors, frequency, and duration in a mature managed care organization.

OBJECTIVES: Reference data are lacking on the frequency and duration of assisted ventilation in neonates. This information is essential for determining resource needs and planning clinical trials. As mortality becomes uncommon, ventilator utilization is increasingly used as a measure for assessing therapeutic effect and quality of care in intensive care medicine. Valid comparisons require adjustments for differences in a patient's baseline risk for assisted ventilation and prolonged ventilator support. The aims of this study were to determine the frequency and length of ventilation (LOV) in preterm and term infants and to develop models for predicting the need for assisted ventilation and length of ventilator support. METHODS: We performed a retrospective, population-based cohort study of 77 576 inborn live births at 6 Northern California hospitals with level 3 intensive care nurseries in a group-model managed care organization. The gestational age-specific frequency and duration of assisted ventilation among surviving infants was determined. Multivariable regression was performed to determine predictors for assisted ventilation and LOV. RESULTS: Of 77 576 inborn live births in the study, 11 199 required admission to the neonatal intensive care unit and of these, 1928 survivors required ventilator support. The proportion of infants requiring assisted ventilation and the median LOV decreased markedly with increasing gestational age. In addition to gestational age, admission illness severity, 5-minute Apgar scores, presence of anomalies, male sex, and white race were important predictors for the need for assisted ventilation. The ability of the models to predict need for ventilation was high, and significantly better than birth weight alone with an area under the receiver operating characteristic curve of.90 versus.70 for preterm infants, and.88 versus.50 for term infants. For preterm infants, gestational age, admission illness severity, oxygenation index, anomalies, and small-for-gestational age status were significant predictors for LOV, accounting for 60% of the variance in the length of assisted ventilation. For term infants, oxygenation index and anomalies were significant predictors but only accounted for 29% of the variance. CONCLUSIONS: Considerable variation exists in the utilization of ventilator support among infants of closely related gestational age. In addition, a number of medical risk factors influence the need for, and length of, assisted ventilation. These models explain much of the variance in LOV among preterm infants but explain substantially less among term infants.neonatal intensive care, assisted ventilation, Score for Neonatal Acute Physiology, resource consumption, prematurity.

California↗
PubMed2002

Evaluation of ventilators used during transport of ICU patients -- a bench study.

OBJECTIVES: To evaluate portable ventilators. DESIGN AND SETTINGS: Bench study. MATERIALS AND METHODS: Five portable ventilators used for transporting ICU patients [Osiris 1, (ventilator a), Osiris 2, (ventilator b), Oxylog 1000, (ventilator c), Oxylog 2000, (ventilator d), AXR1a, (ventilator e)] and three ICU ventilators which can be used for this purpose [Horus, (ventilator f), T-Bird, (ventilator g), and SV 300, (ventilator h)] were compared using a test lung regarding: 1) their capability to maintain set tidal volumes (V(T)) of 300 ml, 500 ml, and 800 ml under a normal condition A [resistance (R) 5 cmH(2)O/l/s and compliance (C) 100 ml/cmH(2)0] and two abnormal conditions B (R 20-C 30) and C (R 50-C 100); 2) trapped volume (expired V(T)relative to inspired V(T)at 0.7 s, 1 s, and 1.4 s), an estimate of the expiratory resistance of both circuit and valve; and 3) the triggering system assessed from the measurements of Delta t, Delta P for two inspiratory efforts at a PEEP of 0 cmH(2)0 and 5 cmH(2)0 in ventilators b, d, f, g, and h. Flow and airway pressure were measured with an independent physiologic recording system. RESULTS: 1) V(T). For ventilators a-h, the mean+/-SD changes of a set V(T)of 300 ml were -2.6+/-0.2%, -9.7+/-0.2%, 0+/-0%, -6.1+/-0.2%, 1.0+/-0.3%, -2.1+/-1.7%, 0.3+/-0%, and -1.3+/-0.1% ( P<0.001), respectively, during condition B relative to A. Similar results were obtained for a V(T)of 500 ml and 800 ml and during condition C relative to A; 2) Trapped volume. For ventilators a-h, trapped volume averaged 1+/-1%, 20+/-0%, 30+/-0.4%, 20+/-1%, 1+/-0%, 19+/-0%, 15+/-0%, and 14+/-0% at 0.7 s ( P <0.001) and 0.6+/-0%, 5+/-0%, 0.5+/-0%, 0+/-0%%, 0+/-0%, 0.6+/-0%, 0+/-0%, and 0+/-0% at 1.4 s ( P=NS); and 3) the triggering system of Oxylog 2000 was poor whereas it was of good quality for Horus, T-Bird, SV 300, and Osiris 2. CONCLUSIONS: The small portable ventilators presently investigated varied between each other and were less accurate than ICU ventilators.

Analysis of Variance↗
PubMed1997

[Anesthesia ventilators].

OBJECTIVE: To review anaesthesia ventilators in current use in France by categories of ventilators. DATA SOURCES: References were obtained from computerized bibliographic search. (Medline), recent review articles, the library of the service and personal files. DATA SYNTHESIS: Anaesthesia ventilators can be allocated into three groups, depending on whether they readminister expired gases or not or allow both modalities. Contemporary ventilators provide either constant volume ventilation, or constant pressure ventilation, with or without a pressure plateau. Ventilators readministering expired gases after CO2 absorption, or closed circuit ventilators, are either of a double- or a single-circuit design. Double-circuit ventilators, or pneumatical bag or bellows squeezers, or bag-in-bottle or bellows-in-bottle (or box) ventilators, consist of a primary, or driving circuit (bottle or box) and a secondary or patient circuit (including a bag or a bellows or membrane chambers). Bellows-in-bottle ventilators have either standing bellows ascending at expiration, or hanging bellows, descending at expiration. Ascending bellows require a positive pressure of about 2 cmH2O throughout exhalation to allow the bellows to refill. The expired gas volume is a valuable indicator for leak and disconnection. Descending bellows generate a slight negative pressure during exhalation. In case of leak or disconnection they aspirate ambient air and cannot act therefore as an indicator for integrity of the circuit and the patient connection. Closed circuit ventilators with a single-circuit (patient circuit) include a insufflating device consisting either in a bellows or a cylinder with a piston, operated by a electric or pneumatic motor. As the hanging bellows of the double circuit ventilators, they generate a slight negative pressure during exhalation and aspirate ambient air in case of leak or disconnection. Ventilators not designed for the readministration of expired gases, or open circuit ventilators, are generally stand-alone mechanical ventilators modified to allow the administration of inhalational anaesthetic agents.

Anesthesia, Closed-Circuit↗
PubMed2005

The effect of electromagnetic interference from mobile communication on the performance of intensive care ventilators.

UNLABELLED: Electromagnetic interference produced by wireless communication can affect medical devices and hospital policies exist to address this risk. During the transfer of ventilated patients, these policies may be compromised by essential communication between base and receiving hospitals. Local wireless networks (e.g. Bluetooth) may reduce the 'spaghetti syndrome' of wires and cables seen on intensive care units, but also generate electromagnetic interference. The aim of this study was to investigate these effects on displayed and actual ventilator performance. METHODS: Five ventilators were tested: Drager Oxylog 2000, BREAS LTV-1000, Respironics BiPAP VISION, Puritan Bennett 7200 and 840. Electromagnetic interference was generated by three devices: Simoco 8020 radio handset, Nokia 7210 and Nokia 6230 mobile phone, Nokia 6230 communicating via Bluetooth with a Palm Tungsten T Personal Digital Assistant. We followed the American National Standard Recommended Practice for On-Site, Ad Hoc Testing (ANSI C63) for electromagnetic interference. We used a ventilator tester, to simulate healthy adult lungs and measure ventilator performance. The communication device under test was moved in towards each ventilator from a distance of 1 m in six axes. Alarms or error codes on the ventilator were recorded, as was ventilator performance. RESULTS: All ventilators tested, except for the Respironics VISION, showed a display error when subjected to electromagnetic interference from the Nokia phones and Simoco radio. Ventilator performance was only affected by the radio which caused the Puritan Bennett 840 to stop functioning completely. The transfer ventilators' performance were not affected by radio or mobile phone, although the mobile phone did trigger a low-power alarm. Effects on intensive care ventilators included display reset, with the ventilator restoring normal display function within 2 s, and low-power/low-pressure alarms. Bluetooth transmission had no effect on the function of all the ventilators tested. CONCLUSION: In a clinical setting, high-power-output devices such as a two-way radio may cause significant interference in ventilator function. Medium-power-output devices such as mobile phones may cause minor alarm triggers. Low-power-output devices such as Bluetooth appear to cause no interference with ventilator function.

Cell Phone↗
PubMed2004

Summary of human responses to ventilation.

UNLABELLED: It is known that ventilation is necessary to remove indoor-generated pollutants from indoor air or dilute their concentration to acceptable levels. But as the limit values of all pollutants are not known the exact determination of required ventilation rates based on pollutant concentrations is seldom possible. The selection of ventilation rates has to be based also on epidemiological research, laboratory and field experiments and experience. The existing literature indicates that ventilation has a significant impact on several important human outcomes including: (1) communicable respiratory illnesses; (2) sick building syndrome symptoms; (3) task performance and productivity, and (4) perceived air quality (PAQ) among occupants or sensory panels (5) respiratory allergies and asthma. In many studies, prevalence of sick building syndrome symptoms has also been associated with characteristics of HVAC-systems. Often the prevalence of SBS symptoms is higher in air-conditioned buildings than in naturally ventilated buildings. The evidence suggests that better hygiene, commissioning, operation and maintenance of air handling systems may be particularly important for reducing the negative effects of HVAC systems. Ventilation may also have harmful effects on indoor air quality and climate if not properly designed, installed, maintained and operated. Ventilation may bring indoors harmful substances or deteriorate indoor environment. Ventilation interacts also with the building envelope and may deteriorate the structures of the building. Ventilation changes the pressure differences across the structures of building and may cause or prevent infiltration of pollutants from structures or adjacent spaces. Ventilation is also in many cases used to control the thermal environment or humidity in buildings. The paper summarises the current knowledge on positive and negative effects of ventilation on health and other human responses. The focus is on office-type working environment and residential buildings. PRACTICAL IMPLICATIONS: The review shows that ventilation has various positive impacts on health and productivity of building occupants. Ventilation reduces the prevalence of airborne infectious diseases and thus the number of sick leave days. In office environment a ventilation rate up to 20-25 L/s per person seem to decrease the prevalence of SBS-symptoms. Air conditioning systems may increase the prevalence of SBS-symptoms relative to natural ventilation if not clean. In residential buildings the air change rate in cold climates should not be below app. 0.5 ach. Ventilation systems may cause pressure differences over the building envelope and bring harmful pollutants indoors.

Air Conditioning↗