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PubMed1984

High-frequency positive-pressure ventilation with the MA-1 ventilator.

A conventional, low-frequency ventilator was modified to ventilate dogs at high frequencies of 85 to 185 cycle/min while cardiovascular and pulmonary variables were monitored. Although gas transport was adequate, cardiac output was diminished when compared to low-frequency ventilation. The addition of an in-line pneumotachograph markedly increased PaCO2 during high-frequency ventilation. Carbon dioxide transport was primarily dependent upon the magnitude of the tidal volume at all high frequencies tested.

Animals↗
PubMed2002

A new ventilation tube for long-term middle ear ventilation.

OBJECTIVES: The treatment of secretory otitis media often requires repeated tubulation of the tympanic membrane as the standard ventilation tubes are extruded before the disease of the middle ear has remitted. The T-tube and its modification have been developed to remain longer in situ, often requiring surgical removal. The rates of subsequent persisting tympanic membrane perforations and granulations around the tube have been unacceptably high. In the search for a long-term ventilation tube with fewer complications, the Duravent tube (Smith and Nephew) has been developed. The aim of the study was to estimate duration in situ and observe complications in using the Duravent tube compared with standard tubes and T- tubes. STUDY DESIGN: Retrospective study. METHODS: In all, 51 patients have been treated with the Duravent tube over a 2-year period. In all, 72 Duravent tubes have been inserted. All patients were subsequently invited for a follow-up examination at a median time of 28 months (range, 11-43 mo) after the tube insertion and were followed up for 5 years. RESULTS: The duration in situ was optimal with a median duration of 17 months. The Duravent tube was extruded spontaneously in all but four cases in which surgical removal was necessary. The rate of persisting perforations of the tympanic membrane was low (4.2%) compared with 24% after the use of the T-tube. Likewise, the usual complications connected with long-term ventilation tubes were less frequent (14% compared with 35% when using the T-tube). CONCLUSIONS: In the present study, the Duravent tube has proved superior to other known long-term ventilation tubes. The problem of granulations, otorrhoea, and tube occlusion was significantly less than reported in other studies using the T-tube.

Adolescent↗
PubMed2003

Ventilator weaning after staged anteroposterior spine fusion in a ventilator-dependent patient with congenital scoliosis: a case report.

STUDY DESIGN: Ventilator weaning after staged revision anteroposterior spine fusion in a ventilator-dependent child with congenital scoliosis is reported. OBJECTIVE: To describe the improvement of pulmonary performance after deformity correction in a patient with severe deformity and severe restrictive lung disease. SUMMARY OF BACKGROUND DATA: The effect of scoliotic deformity correction on postoperative pulmonary function is debatable. Recent prospective studies suggest that corrective surgery, especially that involving violation of the chest cage, adversely affect pulmonary function in patients with adolescent idiopathic scoliosis. For patients with severe deformity and severely compromised preoperative pulmonary function, the effect of deformity correction has not been well studied. METHODS: A 15-year-old ventilator-dependent girl with progressive congenital thoracic scoliosis of 130 degrees and a forced vital capacity of 18% underwent staged revision anteroposterior spine fusion. Anterior release, multiple vertebral osteotomies, apical vertebrectomy, and multiple internal thoracoplasties were performed. Five weeks later, when she was medically stable, she underwent posterior reconstruction with multiple vertebral osteotomies, apical vertebrectomy, and translation and cantilever corrective techniques using Isola instrumentation. RESULTS: The patient's pulmonary function was stable 6 months after surgery, and her forced vital capacity was 19%. Currently, 1 year after surgery, she has been weaned to night-only ventilation. Her walking ability has improved. Her spine is well balanced with a thoracic scoliosis of 40 degrees, and she is neurologically intact. CONCLUSIONS: Surgical correction of a severe thoracic spinal deformity in the setting of severe restrictive lung disease can be performed successfully with stabilization of pulmonary volumes and improvement in pulmonary performance.

Abnormalities, Multiple↗
PubMed1986

Assisted ventilation and the Servo ventilator in infants. An assessment of three systems used for CPAP/IMV.

A laboratory assessment was made of systems used for Continuous Positive Airway Pressure/Intermittent Mandatory Ventilation (CPAP/IMV) with the Servo 900B and 900C ventilators. Pressure-volume loops recorded during sine wave oscillation using an external CPAP/IMV system were similar to those found during normal respiration. Pressure-volume loops using the systems based on the ventilator's inbuilt trigger mechanism were very different, particularly for the 900B. The results were confirmed by measurements in two infants. The implications of these findings with reference to the weaning of infants from mechanical ventilation are discussed.

Humans↗
PubMed1988

Use of negative pressure ventilation to facilitate the return of spontaneous ventilation.

Negative pressure ventilation was used to facilitate the return of spontaneous ventilation in 10 patients with severe, chronic respiratory disability. All patients had required tracheal intubation and intermittent positive pressure ventilation, and conventional weaning techniques had failed. Details of the method are described. It permits extubation before spontaneous ventilation can be sustained indefinitely and thus assists the return of normal speech, sleep pattern and nutrition. The lack of flexible control of ventilatory variables and absence of access to the trachea for sputum clearance limit its widespread application.

Adolescent↗
PubMed1989

Ventilator disconnexion alarm failures. The role of ventilator and breathing system accessories.

Pressure-sensitive ventilator disconnexion alarms do not always alarm during disconnexion of a discharging compliance ventilator such as Manley Blease, unless accurately adjusted. High flows during disconnexion result in significant pressure generation caused by outflow resistance of catheter mounts, heat and moisture exchangers, capnometer cuvettes, and angled connectors; this may lead to alarm failure because of incorrectly adjusted pressure alarm limits. The exact position of the disconnexion is critical and if the alarm's pressure sensor is placed in either the inspiratory or expiratory limb of the ventilator it makes no difference to its correct function. Nine different heat and moisture exchanges were compared in the same breathing system. Those with 15-mm male connectors generate the highest pressures on disconnexion (1.1 kPa). It is suggested that the low pressure alarm limit is set only marginally below the peak inspiratory pressure, and that it is readjusted for every patient and after every change in ventilation. Most importantly, the alarm should be shown to be functional by a trial disconnexion at the tracheal tube.

Equipment Failure↗
PubMed1995

Prolonged interval jet ventilation. An alternative ventilation technique for patients with problematic cardiopulmonary pathophysiology.

The initial clinical experience of using a technique of prolonged interval jet ventilation is reported. Periodic pulses, of from three to nine breaths, were delivered in rapid sequence from a jet ventilator during one-lung ventilation. The expiration phase was free to atmosphere, without added artificial expiratory assist or resistance, and of from 30 to 50 s duration before delivery of the next pulse of jet ventilation. The aim of the technique was to evaluate during anaesthesia the practicalities of securing a prolonged period during which intrathoracic pressure is low and hence optimal for venous return and deflation of pathological pulmonary regions with long time constants. The system used is flexible enough to allow for conventional positive pressure techniques to be applied if necessary. As the gas delivery was of oxygen of high concentration, episodes of hypoxaemia were minimal in this group of high risk patients and due to technical rather than physiological causes. The delivery of a minute volume adequate to prevent hypercapnia was not always possible and the technique may be contraindicated in those conditions in which a raised carbon dioxide concentration is disadvantageous.

Adult↗
PubMed1989

Efficacy of high frequency ventilation combined with volume controlled ventilation in dependency of extravascular lung water.

In a prospective study continuous positive pressure ventilation (CPPV) was compared with the combination of CPPV and high frequency ventilation (CHFV). Forty-seven patients of a surgical intensive care unit who required mechanical ventilation were randomly assigned to a CHFV group (n = 27) or a control group with CPPV (n = 20). Usual hemodynamic and oxygenation variables, intrathoracic blood volume (ITBV) and extravascular lung water (ETV) were assessed before and 6 h after switching to CHFV (CHFV group) or maintaining CPPV (control group). In both groups mean airway pressure (MPaw) was kept constant. The change of the respiratory index (dRI) was used for evaluation of the effect of the ventilation mode. A negative correlation was found between ETV and dRI (r = -0.67), which led to the conclusion that the height of ETV determines the efficacy of CHFV. In a CHFV subgroup with ETV greater than 15 ml/kg (n = 17), CHFV significantly improved PaO2/FiO2 (18.7 to 26.4 kPa), RI (4.44 to 2.99) and intrapulmonary shunt (33.5 to 27.5%) and slightly, but significantly impaired cardiac index (CI, 4.45 to 3.92 l/min.m2), stroke volume index (40.7 to 36.4 ml/m2) and pulmonary vascular resistance index (PVRI, 310 to 366 dyn.s.cm-5.m2), but oxygen delivery (DO2) remained almost unchanged. The CI decrease came about with an increase of PVRI on account of an increased lung volume under CHFV in this group. CHFV induced no significant effects in the subgroup with ETV less than 15 ml/kg (n = 10). There were no differences in any variable during CPPV between the CHFV subgroups and corresponding subgroups of the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Reduced CO2-elimination during combined high-frequency ventilation compared to conventional pressure-controlled ventilation in surfactant-deficient piglets.

BACKGROUND: Combined high-frequency ventilation (CHFV) combines a conventional low-frequency component with super-imposed high-frequency jet pulses. The intention is to overcome the limited CO2-elimination of high-frequency ventilation, and to decrease airway pressures and enhance hemodynamic performance by reducing the conventional component. The present study was performed to compare the effects of conventional continuous positive-pressure ventilation (CPPV) on gas exchange, airway pressures and cardiac output to those of CHFV at matched minute volume (MV) and mean airway pressure (MPAW). METHODS: Sixteen anaesthetised piglets with lavage-induced surfactant deficiency were ventilated with CPPV, with positive end-expiratory pressure (PEEP) set to obliterate the lower inflection point of the inspiratory pressure-volume loop. This setting was compared to CHFV during which 50% of the total MV was applied as superimposed jet pulses of 20 Hz at otherwise unchanged settings, and to CPPV at a PEEP level which was reduced (CPPVred) until MPAW matched MPAW during CHFV. Gas exchange, airway pressures and hemodynamics were measured after the ventilatory setting had been applied for 20 min. RESULTS: MPAW decreased from (median) 2.7 kPa with CPPV to 2.4 kPa with CHFV (P < or = 0.05). Peak inspiratory pressure was 3.6 kPa with CPPV, 3.2 kPa with CHFV, and 3.2 kPa with CPPVred (P < or = 0.05 for differences to CPPV), respectively. PaCO2 was comparable during CPPV (5.9 kPa), CPPVred and CHFVCO2, while it increased during CHFV (6.8 kPa, (P < or = 0.05)). Cardiac output did not differ significantly between the settings. CONCLUSION: In the porcine lavage model, CO2-elimination is reduced during CHFV compared to CPPV at matched minute volume. At matched mean airway pressure, CHFV fails to reduce peak inspiratory airway pressure and to improve hemodynamic performance compared to CPPV.

Airway Resistance↗
PubMed2004

Human response to personalized ventilation and mixing ventilation.

UNLABELLED: The response of 60 human subjects to a personalized ventilation system (PVS), providing control of positioning of the air terminal device and the airflow rate, was compared with the response to mixing ventilation (MV). Perceived air quality, thermal comfort, intensity of Sick Building Syndrome symptoms and performance of subjects were studied during 3 h 45 min exposures. In case of MV alone the room air temperature was 23 degrees C and 26 degrees C. The PVS supplied outdoor air at 23 degrees C or 20 degrees C or recirculated room air at 23 degrees C when the room temperature was 23 degrees C, and outdoor air at 20 degrees C when the room temperature was 26 degrees C. The PVS providing outdoor air improved perceived air quality and decreased SBS symptoms compared to MV alone and when the room air was re-circulated through the PVS. The percentage dissatisfied with air quality, 3 min after initial occupancy, decreased from 22% with MV to 7% with PVS; and from 49% to 20%, at room temperatures 23 degrees C and 26 degrees C, respectively. Over time, these differences in percentage dissatisfied decreased markedly. Headache and decreased ability to think clearly were reported as least intense when the PVS supplied outdoor air at 20 degrees C, while the most intense symptoms occurred with MV. PVS increased self-estimated performance. PRACTICAL IMPLICATIONS: Personalized ventilation can improve occupants' thermal comfort, perceived air quality and decrease the intensity of SBS symptoms compared to mixing ventilation. Occupants will use the provided individual control of airflow rate and positioning of the air terminal device to obtain preferred microenvironment in rooms where the air temperature is within the range recommended by indoor climate standards. Development of more efficient air terminal devices is recommended.

Adult↗
PubMed1994

Comparison of weaning by patient triggered ventilation or synchronous intermittent mandatory ventilation in preterm infants.

Forty preterm infants were entered into a randomized controlled trial to compare the efficacy and duration of weaning by patient triggered ventilation (PTV) to that of synchronous intermittent mandatory ventilation (SIMV). Infants were randomized during recovery from respiratory distress once ventilator rate had been reduced to 40 breaths per minute; weaning during PTV was by reduction in ventilator pressure only, whereas infants randomized to SIMV were weaned by reduction in rate only. Weaning failed in 12 infants, 6 from each group, the 12 infants were more immature than those in whom weaning succeeded (p < 0.01). Overall, the duration of weaning did not differ significantly between the PTV and SIMV groups.

Gestational Age↗
PubMed1998

[Clinical analysis of patients with nosocomial pneumonia during mechanical ventilation (so-called ventilator-associated pneumonia)].

To clarify the clinical features of nosocomial pneumonia during mechanical ventilation (ventilator-associated pneumonia) and to select the appropriate antibiotic therapy for patients, we performed a clinical analysis of 19 patients (26 episodes) with this condition. The following results were obtained. 1, The average age of the patients was 68 years old (male 16, female 3). 2, VAP occurred three times in 2 cases, twice in 3 cases, and once in 14 cases. 3, The duration of mechanical ventilation was from 7 days to 11 years and 5 months (the average was 2.1 years). 4, The microorganism isolated from the aspiration sputum of the VAP patients was Pseudomonas aeruginosa frequently, but it was difficult to determine whether this microorganism was the causative microorganism. Ten strains of Staphylococcus aureus (MRSA seven strains and MSSA three strains) were newly isolated at the same time as VAP and especially in the cases in which these were thought to be causative microrganisms, all the patients died within a short time. 5, Antibiotics were clinically effective for 53.8% of all the VAP patients and carbapenem antibiotics (for example, IPM/CS) were also used for the effective group. 6, Regarding the risk factors for VAP, factors such as the duration of mechanical ventilation, the existence of chronic obstructive pulmonary disease, a hyponutritional state, prior antibiotics, aspiration of gastric contents, histamine-type-2 receptor antagonist, and multiple organ failure showed significant differences and were suspected to be associated with the appearance of VAP.

Adult↗
PubMed1994

Nasal ventilation in acute exacerbations of chronic obstructive pulmonary disease: effect of ventilator mode on arterial blood gas tensions.

BACKGROUND: There are no controlled trials of the use of different modes of nasal intermittent positive pressure ventilation (NIPPV) in patients with exacerbations of chronic obstructive pulmonary disease (COPD). This study describes the effect on blood gas tensions of four different modes of nasal ventilation. METHODS: Twelve patients with acute exacerbations of COPD were studied (mean (SD) FEV1 0.59 (0.13) l, PaO2 (air) 5.10 (1.12) kPa, PaCO2 9.28 (1.97) kPa, pH 7.32 (0.03)). Each patient underwent four one-hour periods of nasal ventilation in randomised order: (a) inspiratory pressure support 18 cm H2O; (b) pressure support 18 cm H2O+positive end expiratory pressure (PEEP) 6 cm H2O (IPAP+EPAP); (c) continuous positive airway pressure (CPAP) 8 cm H2O; and (d) volume cycled NIPPV. Arterial blood samples were obtained before each period of ventilation and at one hour. RESULTS: Pressure support, CPAP, and volume cycled NIPPV all produced significant improvements in PaO2; there was no difference between these three modes. The change in PaO2 with IPAP+EPAP did not reach statistical significance. None of the modes produced significant changes in mean PaCO2; patients with higher baseline levels tended to show a rise in PaCO2 whereas those with lower baseline levels tended to show a fall. CONCLUSIONS: Although PaO2 improved in all patients there are differences in efficacy between the modes, while the changes in PaCO2 were variable. The addition of EPAP conferred no advantage in terms of blood gas tensions.

Aged↗
PubMed2002

Distinct patterns of apoptosis in the lung during liquid ventilation compared with gas ventilation.

To determine whether liquid ventilation (LV) causes less cell injury and improves lung function compared with conventional gas ventilation (GV), we analyzed pulmonary physiological profiles, lung histology, and cell death in 110- and 120-day preterm lambs, which were randomized to receive either ventilation modality on FI(O(2)) = 1. LV lungs were well expanded with adequate pulmonary function, whereas GV animals exhibited marked atelectasis, poor pulmonary function, and increased mortality. Both ventilatory strategies induced marked lung cell apoptosis, but with distinct patterns of distribution. Although GV induced apoptosis of epithelium primarily in the lining and within the lumina of bronchioles, LV induced significant apoptosis much more homogeneously throughout lung parenchyma including alveoli and interstitial spaces. These studies suggest that although both forms of ventilation cause regional apoptosis, LV more effectively delivers oxygen and recruits the lung more homogeneously than GV.

Animals↗
PubMed1986

Inspiratory-to-expiratory time ratio and alveolar ventilation during high-frequency ventilation in dogs.

It has been suggested that the increase in inspiratory flow rate caused by a decrease in the inspiratory-to-expiratory time ratio (I:E) at a constant tidal volume (VT) could increase the efficiency of ventilation in high-frequency ventilation (HFV). To test this hypothesis, we studied the effect of changing I:E from 1:1 to 1:4 on steady-state alveolar ventilation (VA) at a given VT and frequency (f) and at a constant mean lung volume (VL). In nine anesthetized, paralyzed, supine dogs, HFV was performed at 3, 6, and 9 Hz with a ventilator that delivered constant inspiratory and expiratory flow rates. Mean airway pressure was adjusted so that VL was maintained at a level equivalent to that of resting FRC. At each f and one of the I:E chosen at random, VT was adjusted to obtain a eucapnic steady state [arterial pressure of CO2 (PaCO2) = 37 +/- 3 Torr]. After 10 min of each HFV, PaCO2, arterial pressure of O2 (PaO2), and CO2 production (VCO2) were measured, and I:E was changed before repeating the run with the same f and VT. VA was calculated from the ratio of VCO2 and PaCO2. We found that the change of I:E from 1:1 to 1:4 had no significant effects on PaCO2, PaO2, and VA at any of the frequencies studied. We conclude, therefore, that the mechanism or mechanisms responsible for gas transport during HFV must be insensitive to the changes in inspiratory and expiratory flow rates over the VT-f range covered in our experiments.

Animals↗
PubMed1995

Variability of patient-ventilator interaction with pressure support ventilation in patients with chronic obstructive pulmonary disease.

In 12 patients with chronic obstructive pulmonary disease (COPD) receiving pressure support ventilation (PSV), we studied the variability of respiratory muscle unloading and defined its physiologic determinants using a modified pressure-time product (PTP). Inspiratory PTP/min decreased as PSV was increased (p < 0.001), but there was considerable interindividual variation: coefficients of variations of up to 96%. On multiple linear regression analysis, 73 to 83% of the variability in inspiratory PTP was explained by inspiratory resistance, minute ventilation, and intrinsic positive end-expiratory pressure. Taking an inspiratory PTP/min of < 125 cm H2O.sec/min to represent a desirable level of inspiratory effort during PSV, a respiratory frequency of < or = 30 breaths/min was more accurate than a tidal volume > 0.6 L in predicting this threshold (p < 0.001). At PSV of 20 cm H2O, expiratory effort, quantitated by an expiratory PTP, was clearly evident in five patients before the cessation of inspiratory flow, signifying that the patient was "fighting" the ventilator; of note, these five patients had a frequency of < or = 30 breaths/min. In conclusion, patient-ventilator interactions in patients with COPD are complex, and events in expiration need to be considered in addition to those of inspiration.

Aged↗
PubMed1999

Significant tracheal obstruction causing failure to wean in patients requiring prolonged mechanical ventilation: a forgotten complication of long-term mechanical ventilation.

INTRODUCTION: Modern low-pressure, high-volume cuffed tracheotomy tubes have been shown to decrease tracheal injury. However, injury still occurs in patients requiring prolonged mechanical ventilation and prevents weaning, delays decannulation, prolongs hospitalization, and may totally obstruct the airway. We describe 37 patients, including the first reported case of failure to wean due to tracheal obstruction. METHODS: Over a 3-year period, from September 1994 to August 1997, the hospital records of 37 patients requiring prolonged mechanical ventilation (> 4 weeks) and found to have tracheal obstruction were reviewed retrospectively. They were a subgroup of 756 patients admitted to hospitals during the same period. The average endotracheal/tracheostomy cannulation time was 3 weeks/12 weeks (range 2 to 4 weeks/8 to 14 weeks). Average age was 76 years (range, 34 to 81). Underlying diseases included COPD, postcoronary artery bypass graft surgery, postpneumonectomy, severe pneumonia, acute lung injury, and ischemic heart disease. RESULTS: All 37 patients who initially failed to wean had difficulty in breathing and developed intermittent high peak airway pressures either early or during the weaning process or just on being ventilated. The insertion of a longer tracheal tube bypassed the obstruction, reestablished the airway, decreased peak airway pressures, and allowed the patient to breathe more easily. The obstruction was confirmed on bronchoscopy. Treatment consisted of either placement of a longer tracheal tube (34 of 37 patients) or placement of a tracheal stent. All but two of the patients (5.4%) were able to be weaned within a week. The two patients who still failed to be weaned were subsequently diagnosed as having amyotrophic lateral sclerosis. CONCLUSION: Tracheal obstruction in patients requiring prolonged mechanical ventilation prevented weaning. Reestablishment of the airway with a longer tracheal tube or tracheal stent allowed most of the patients to be weaned.

Adult↗
PubMed2002

[Variability of ventilation parameters of home ventilation equipment].

The performance of pressure- and volume controlled ventilators used for invasive and non-invasive ventilation in the home were tested on a patient lung model. In order to determine the influence of tidal volume preset, breathing rate, resistance, compliance and leakage to the variability of delivered tidal volume and peak airway pressure a factorial plan with adapted analysis of variance was used. The influence of tidal volume preset, compliance and leakage to the delivered tidal volume is significant. The peak airway pressure depends hardly on the influence factors. All tested ventilators meet the legal demands. But in some clinical situations there are considerable deviations of the breathing parameters depending on the brand. In conclusion ventilators of different brands are not interchangeable.

Analysis of Variance↗