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PubMed1995

[Effectiveness of intermittent self-ventilation after ventilator weaning].

The essential cause for long-term mechanical ventilation with unweanability from respirator is chronic failure of the inspiratory muscles. Principally two different causes exist for chronic respiratory failure: Primary pulmonary diseases with overload or load imbalance of primarily uncompromised respiratory muscles, and neuromuscular diseases with a significant decrease in respiratory muscle capacity. Intermittent nocturnal ventilation (INV) leads to recovery by unloading the respiratory pump. In the present retrospective study we examined the value of INV in the "post-weaning-phase" for previously unweanable, long term ventilated patients. In two years (1993 and 1994) 43 patients who had been ventilated for 57.5 +/- 60.3 days in outward intensive care units (ICU) in a predominantly assisted mode we could wean from the respirator within 8.4 +/- 5.5 days by means of consequently applying an individually adapted, volume cycled weaning regime. In all patients, on admission to our ICU and before discharge blood gases, P0.1, Pimax, breathing frequency and tidal volume were measured during spontaneous breathing. After weaning in about 40% of our patients we decided to initiate INV with intermittent positive pressure ventilation (IPPV). The indication for INV after weaning depended on whether a chronic hypercapnic respiratory failure continued to be demonstrable. In this group of patients, INV was the essential stabilizing factor for continuous weaning success, as the respiratory muscles recovered during the ensuing inpatient phase and the daytime PaCO2 normalised. In most of our patients (14 out of 18) INV could be performed non-invasively via breathing masks. Only 4 out of 18 patients continued to be long-term ventilated invasively via tracheostomy. The remaining patients (25 out of 43) showed normoventilation at daytime during the ensuing inpatient phase so they did not need INV. At the time of the patients' referral to our ICU, there was no predictive value regarding the ultimate indication for INV after weaning from respirator.

Adult↗
PubMed2000

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction.

Few studies have been published on gas distribution in the lung during acute and stable airway obstruction in children. Multiple breath nitrogen (N(2)) washout is an established method for assessing ventilation inhomogeneity, while the tidal breathing capnogram may be used as an indicator of ventilation-perfusion (V(')(A)/Q) mismatch. We hypothesized that significant V(')(A)/Q mismatch is not seen in stable airway obstruction unless obstruction is severe, and that stable and induced airway obstruction of similar severity would result in different degrees of V(')(A)/Q mismatch. To test this hypothesis, we performed spirometry measurements of forced expiratory volume in 1 sec (FEV(1)), multiple breath N(2) washout, and tidal breathing capnography in 11 young patients (9-30 years) with cystic fibrosis, 37 asthmatic patients (8-18 years), and 34 healthy subjects (7-20 years). Lung function was measured at rest, after airway obstruction induced by cold dry air hyperventilation or methacholine challenge, and after beta(2)-agonist treatment. V(')(A)/Q mismatch was assessed from the slopes of the phases II and III of the capnogram. We observed a normal capnogram during stable obstruction of moderate severity despite significant ventilation inhomogeneity. In patients with severe stable obstruction and in those with induced airway obstruction significant ventilation inhomogeneity and pathological capnograms were seen. Induced airway obstruction, resulted in a more pathological capnogram than stable obstruction of similar severity. beta(2)-agonist treatment reduced ventilation inhomogeneity, but did not improve the capnogram. Our findings are compatible with the presence of an efficient pulmonary blood flow regulatory mechanism that adequately compensates for chronic ventilation inhomogeneity of moderate severity, but not for severe or sudden airway obstruction.

Adolescent↗
PubMed2000

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

BACKGROUND: This section is under preparation and will be included in the next issue. OBJECTIVES: Experimental studies suggest that high frequency oscillatory ventilation (HFOV) reduces pulmonary injury during mechanical ventilation. The main objective of this review is to test the hypothesis that by use of HFOV as compared to conventional ventilation (CV) it may be possible to rescue preterm infants with very severe lung disease and so at high risk of pulmonary air leak (PAL), without adverse effects. SEARCH STRATEGY: A search was carried out for all randomized controlled trials from MEDLINE using the MeSH and text terms, "high frequency ventilation", "high frequency oscillatory ventilation", " oscillatory ventilation" from the years 1980 to 1997. EMBASE, the Oxford Database of Perinatal Trials and trials identified by the Neonatal Review Group of the Cochrane Collaboration were also reviewed. Information was also sought from experts in the field, cross references from studies and proceedings of recent meetings. SELECTION CRITERIA: Randomized controlled trials of HFOV vs CV as rescue therapy in preterm infants with severe pulmonary dysfunction. DATA COLLECTION AND ANALYSIS: The standard review method of the Neonatal Review Group was used. This includes independent quality assessment and data extraction by the second author. Relative risk (RR), risk difference (RD) and number needed to treat (NNT) were used. MAIN RESULTS: Only one trial was found and this showed a reduction in any new pulmonary air leak (PAL) [RR 0.73 (0.55,0.96), RD -0.174 (-0.321,-0.027)]. The number of infants that need to be treated (NNT) to prevent one infant having any PAL is six (95% CI 3, 37). There is no difference in the rate of PIE or of gross pulmonary air leak, such as pneumomediastinum or pneumothorax. Mortality and the use of IPPV at 30 days was similar in the HFOV and CV groups. The rate of intraventricular hemorrhage (IVH) of any grade is increased in infants treated with HFOV, RR 1.77 (1.06,2.96), RD 0.156 (0.020, 0. 291). Thus for every six infants (95% CI 3, 50) given rescue HFOV, one IVH of any grade is caused. There is a stronger but non-significant trend towards an increase in the more severe grades 3 or 4 IVH. REVIEWER'S CONCLUSIONS: There is insufficient information on the use of rescue HFOV to make recommendations for practice. The small amount of data that exists suggest that harm might outweigh any benefit. Any future use of HFOV as rescue therapy for preterm infants with severe RDS should be within randomized controlled trials and address important outcomes such as longer term pulmonary and neurological function.

High-Frequency Ventilation↗
PubMed2001

Rescue high frequency oscillatory ventilation vs conventional ventilation for infants with severe pulmonary dysfunction born at or near term.

BACKGROUND: Pulmonary disease is a major cause of mortality and morbidity in term and near term infants. Conventional ventilation (CV) has been used for many years but may lead to lung injury, require the subsequent use of more invasive treatment such as extra corporeal membrane oxygenation (ECMO), or result in death. There are some studies indicating that high frequency oscillatory ventilation (HFOV) may be more effective in these infants as compared to CV. OBJECTIVES: The objective of this review is to determine if HFOV, as compared to conventional ventilation, reduces mortality and morbidity in term or near term infants with intractable lung disease without an increase in adverse effects. SEARCH STRATEGY: Standard search methods of the Cochrane Neonatal Review group were used. These included searches of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, and journal hand searching by the Cochrane Collaboration. SELECTION CRITERIA: Randomized or quasi-randomized trials comparing HFOV and CV in term or near term infants with intractable respiratory failure were included in this review. DATA COLLECTION AND ANALYSIS: The standard methods of the Cochrane Neonatal Review Group were used. The investigators separately extracted, assessed and coded all data for each study. Any disagreement was resolved by discussion. Data were synthesized using relative risk (RR) and risk difference (RD). MAIN RESULTS: Only one trial met the inclusion criteria. This rescue trial of 81 infants showed no evidence of a reduction in mortality at 28 days [RR 0.51 (0.05, 5.43)] or in failed therapy on the assigned mode of ventilation requiring cross-over to the other mode [RR 0.73 (0.47, 1.13)]. There were no significant differences in the numbers of patients requiring extracorporeal membrane oxygenation [RR 2.05 (0.85, 4.92)], days on a ventilator, days in oxygen or days in hospital. REVIEWER'S CONCLUSIONS: There are no data from randomized controlled trials supporting the routine use of rescue HFOV in term or near term infants with severe pulmonary dysfunction. The area is complicated by diverse pathology in such infants and by the occurrence of other interventions (surfactant, inhaled nitric oxide, inotropes). Randomized controlled trials are needed to establish the role of rescue HFOV in near term and term infants with pulmonary dysfunction before widespread use of this mode of ventilation in such infants.

High-Frequency Ventilation↗
PubMed2006

Effects of pressure support ventilation plus volume guarantee vs. high-frequency oscillatory ventilation on lung inflammation in preterm infants.

The aim of the present study was to evaluate if high-frequency oscillatory ventilation (HFOV) might reduce lung inflammation in preterm infants with infant respiratory distress syndrome (RDS) in comparison with the early application of another potentially lung-protective ventilation strategy, such as pressure support ventilation plus volume guarantee (PSV + VG). Infants at less than 30 weeks of gestation with RDS were enrolled consecutively in the study if they required mechanical ventilation, and were randomly allocated to receive HFOV or PSV + VG. Bronchial aspirate samples for the measurement of interleukin (IL)-1beta, IL-8, and IL-10 were obtained before surfactant treatment (T1), after 6-18 hr of ventilation (T2), after 24-48 hr of ventilation (T3), and before extubation (T4). Thirteen patients were enrolled in the HFOV group, and 12 in the PSV + VG group. The mean values of IL-1beta, IL-8, and IL-10 at T4 were lower in the HFOV group than in the PSV + VG group. The present study demonstrates that early treatment with HFOV is associated with a reduction of lung inflammation in comparison with PSV + VG in preterm infants with RDS.

Bronchoalveolar Lavage Fluid↗
PubMed1994

Immunohistochemical quantitation of collagen types I, II, IV and V in the ventilated and non-ventilated rabbit middle ear with otitis media with effusion.

Morphometric quantitation of the area fractions of collagen types I, II, IV and V was determined in the normal rabbit middle ear mucosa and in relation to otitis media with effusion (OME) using a three-layered peroxidase-antiperoxidase technique. The effects of substituting normal low-oxygen middle ear gas (non-ventilated) with atmospheric air (ventilated) were studied in both healthy ears and ears with OME. Based upon previous histological examinations in rabbits, only ears with OME for more than 8 weeks were included to ensure the presence of chronic inflammation (COME). Atmospheric air was introduced into the middle ears by insertion of ventilation tubes or by an enlarged myringotomy. Collagen type I was predominant in all groups studied. The area fractions of collagen types I, II and IV were increased significantly in COME, with collagen type II elevated in particular. Ventilation of the normal ears resulted in a significantly increased area fraction of cells, while the area fractions and distributions of the collagen types were unaffected. None of the ventilated ears in COME improved or healed spontaneously. The total fraction of collagen in COME was not changed significantly by the introduction of atmospheric air. However, the individual distribution of the collagen types was altered, with significantly larger area fractions of types II and V found in ventilated ears with COME. Possible explanations for the differences found are discussed, including the role of oxygen-derived free radicals.

Animals↗
PubMed1994

The use of an endotracheal ventilation catheter for jet ventilation during a difficult intubation.

This case report describes the use of an endotracheal ventilation catheter (ETVC) to provide prolonged intraoperative jet ventilation, reintubation and the maintenance of tracheal access following extubation. It emphasizes that excellent oxygenation and ventilation can be achieved but such management can be complicated by a pneumothorax even when the risks are minimized. A 43-yr-old man presented for possible pulmonary sleeve resection. Placement of a double lumen endotracheal tube (DLT) by direct laryngoscopy was unsuccessful due to the inability to visualize the glottis. A 7.5 mm endotracheal tube (ETT) was successfully introduced over a fibreoptic bronchoscope (FOB). An ETVC was passed, permitting manually cycled jet ventilation while general intravenous anaesthesia and muscle relaxation were maintained. The ETT was then withdrawn over the ETVC and jet ventilation continued for approximately 90 min, while attempts at placing a DLT over a now malfunctioning FOB continued. These attempts were eventually abandoned and the patient was returned to the post-anaesthesia care unit (PACU) haemodynamically stable. The trachea was extubated over the ETVC, which remained in situ. A pneumothorax was noted on the postoperative chest x-ray. This case illustrates prolonged intraoperative jet injection via a "jet stylet" with satisfactory ventilation and oxygenation but complicated by a pneumothorax. Also it illustrates a strategy for the management of a "difficult extubation."

Adult↗
PubMed2005

[Decreased inspiratory time during ventilation of an unprotected airway. Effect on stomach inflation and lung ventilation in a bench model].

BACKGROUND: In an unprotected airway during cardiopulmonary resuscitation, two ventilations with an inspiratory time of 2 s after 15 chest compressions are recommended. Therefore, approximately 30% of the resuscitation attempt is spent on ventilation. Since survival rates did not decrease sharply when minute ventilation levels were relatively low, and uninterrupted chest compressions with a constant rate of approximately 100/min have been shown to be lifesaving, it may be beneficial to decrease the time spent on ventilation and instead, increase the time for chest compressions. METHODS: In an established bench model of a simulated, unprotected airway with increased airway resistance, we evaluated if inspiratory time can be decreased from 2 to 1 s at different lower oesophageal sphincter pressure (LOSP) levels during ventilation with a bag-valve-mask device. RESULTS: An inspiratory time of 2 vs. 1 s resulted in significantly lower peak airway pressure, while lung tidal volume was significantly higher at an inspiratory time of 2 s and a LOSP of 5 cm H(2)O (480+/-20 vs. 380+/-30 ml) and 10 cm H(2)O (630+/-50 vs. 440+/-20 ml) and significantly lower at a LOSP of 15 cm H(2)O (470+/-70 vs. 540+/-20 ml). While neither ventilation strategy produced stomach inflation at 20 cm H(2)O LOSP, 1 vs. 2 s inspiratory time produced significantly higher stomach inflation at 15 cm H(2)O LOSP (8+/-11 vs. 0 ml) and significantly lower stomach inflation at a LOSP of 5 cm H(2)O (359+/-31 vs. 375+/-29 ml) and 10 cm H(2)O (28+/-13 vs. 36+/-12 ml) per breath. CONCLUSION: In this model of a simulated, unprotected airway, a reduction of inspiratory time from 2 to 1 s resulted in a significant increase of peak airway pressure, while lung tidal volumes and stomach inflation volumes were statistically different but clinically comparable.

Airway Resistance↗
PubMed1997

Generation of nitrogen dioxide during nitric oxide therapy and mechanical ventilation of children with a Servo 900C ventilator.

OBJECTIVE: To determine the combinations of nitric oxide (NO), oxygen (O2), minute ventilation (MV) and total gas flow (TGF) which generate toxic concentrations of nitrogen dioxide (NO2) during mechanical ventilation with a Servo 900C ventilator. DESIGN: The measurement of NO2 generated with NO (20, 40, 60, 80, 100 ppm) and O2 [fractional inspired oxygen (FIO2) 0.21, 0.4, 0.6, 0.9] during mechanical ventilation with MVs of 2.5, 5.0 and 7.5 l/min and TGFs from 2 to 14 l/min. SETTING: Laboratory of intensive care unit in paediatric tertiary hospital. RESULTS: Toxic concentrations of NO2 (> 5 ppm) were generated in the ventilator circuit when NO was 80 ppm or 100 ppm in FIO2 of 0.6 or 0.9 with MVs of 2.5, 5.0 and 7.5 l/ min; and with 80 ppm NO in FIO2 of 0.6 at all TGFs from 2.0 to 13.6 l/min and MVs of 2.5, 5.0 and 7.5 l/min (TGF/MV 0.3-5.4). NO2 1.5-2.6 ppm was generated with 40 ppm NO in FIO2 of 0.6, TGFs 2.1-13.7 l/ min, and MVs 2.5, 5.0 and 7.5 l/min (TGF/MV 0.3-5.5). NO2 0.9-0.6 ppm was generated with 20 ppm NO in FIO2 of 0.6, TGFs 2.5-13.8 and MVs 2.5, 5.0 and 7.5 (TGF/MV 0.3-5.5). NO2 generation was not affected significantly by the TGF/MV ratio. CONCLUSIONS: The generation of NO2 in the ventilator circuit is directly proportional to concentration of NO and O2 and inversely proportional to the TGF and MV but uninfluenced by the TGF/MV ratio. NO 80 ppm, but neither 20 nor 40 ppm in FIO2 of 0.6, generates toxic NO2 irrespective of TGF, MV or the TGF/MV ratio.

Child↗
PubMed1991

Ultralow-yield cigarettes and type of ventilation: the role of ventilation blocking.

Habitual smokers of perforation-ventilated cigarettes and of channel-ventilated cigarettes (18 male and 18 female subjects each; nicotine yield 0.1-0.3 mg, 0.2 mg, respectively) were compared with respect to different smoke exposure indicators and puffing behavior. The role of ventilation blocking was assessed by comparing normal lip contact with smoking through a cigarette holder. The presmoking concentrations (plasma nicotine, cotinine, respiratory CO) were higher for channel-filter than for perforation-ventilated cigarettes, as were the pre- to postsmoking boosts (nicotine, CO) with normal lip smoking. Holder smoking resulted in lower boosts than lip smoking for the channel filter cigarettes, although the puffing behavior was considerably intensified. The boosts for perforation-ventilated cigarettes remained unchanged and were reached with only moderately intensified puffing behavior. The results indicate the importance of ventilation blocking in everyday lip smoking for channel-filter cigarettes, but not for conventional, perforated cigarettes.

Adult↗
PubMed2006

Advanced lung ventilation system (ALVS) with linear respiratory mechanics assumption for waveform optimization of dual-controlled ventilation.

The present paper describes the functional features of an advanced lung ventilation system (ALVS) properly designed for the optimization of conventional dual-controlled ventilation (DCV), i.e. with pressure-controlled ventilation with ensured tidal or minute volume. Considering the particular clinical conditions of patients treated with controlled ventilation the analysis and synthesis of ALVS control have been performed assuming a linear respiratory mechanics. Moreover, new airways pressure waveforms with more physiological shape can be tested on simulators of respiratory system in order to evaluate their clinical application. This is obtained through the implementation of a compensation procedure making the desired airways pressure waveform independent on patient airways resistance and lung compliance variations along with a complete real-time monitoring of respiratory system parameters leading the ventilator setting. The experimental results obtained with a lung simulator agree with the theoretical ones and show that ALVS performance is useful for the research activity aiming at the improvement of both diagnostic evaluation and therapeutic outcome relative to mechanical ventilation treatments.

Computer Simulation↗
PubMed1988

Tracheal and bronchial injury in high-frequency oscillatory ventilation and high-frequency flow interruption compared with conventional positive-pressure ventilation.

We compared the histopathologic changes in the airways of premature baboons treated with conventional positive-pressure ventilation (PPV) with those seen after high-frequency oscillatory ventilation (HFOV) and high-frequency flow interruption (HFFI). Twenty-six animals were treated with ventilation for 24 hours (five PPV, 10 HFOV, 11 HFFI), and 18 were treated with ventilation for 96 hours (six PPV, six HFOV, six HFFI). A semiquantitative scoring system was used to grade tissue changes in the trachea, carina, and both main-stem bronchi. Alterations were produced by all forms of mechanical ventilation. The degree of injury was similar and relatively mild for the PPV- and HFOV-treated animals at both 24 and 96 hours. Eleven of 17 baboons treated with HFFI ventilation (8/11 at 24 hours; 3/6 at 96 hours) had severe airway damage characterized by diffuse submucosal necrosis, extensive hemorrhage, dense polymorphonuclear leukocyte infiltration, sloughed epithelium, focal basophilia, and intraluminal debris. HFOV resulted in no greater degree of airway damage than did PPV. The use of HFFI, with the particular strategy we employed, resulted in a far greater degree of damage than either PPV (P less than 0.01) or HFOV.

Animals↗
PubMed1999

Lung deflation stimulates fictive ventilation in decerebrated and unidirectionally ventilated toads.

We describe how the degree of lung inflation and hypercapnia influenced fictive ventilation in five toads (Bufo marinus) that were decerebrated and paralysed with roccuronium. Both lungs were unidirectionally ventilated and the degree of lung inflation was determined by controlling the outflow resistance of these catheters, while ventilatory motor output was assessed on the basis of nervous activity in the mandibular branch of the Vth cranial nerve. The pattern of the recorded activity ('fictive ventilation') resembled the ventilatory patterns previously described for conscious toads. Increasing the fraction of CO2 in the gas mixture used for unidirectional ventilation from 0.00 to 0.05 stimulated fictive breathing. Fictive ventilation was also greatly stimulated, at all CO2 levels, by reduced lung volume, while complete inflation of the lungs abated fictive ventilation at all levels of CO2. Stimulation of CO2 sensitive chemoreceptors and pulmonary stretch receptors appear to have interactive effects on the central generation of ventilatory output in toads.

Animals↗
PubMed2003

[Non-invasive ventilation in kyphoscoliosis. A comparison of a volumetric ventilator and a BIPAP support pressure device].

Non-invasive intermittent positive pressure ventilation (NIPPV) at home is the treatment of choice for patients with chronic respiratory insufficiency secondary to severe kyphoscoliosis. Our aim was to compare clinical course, blood gases and lung function after one month of domiciliary NIPPV with two types of ventilator and to assess sleep pattern changes in patients enrolled in a prospective, randomized crossover study. Ten patients with chronic respiratory insufficiency due to kyphoscoliosis were enrolled and randomly assigned to the first device. After one month of use, the patients underwent clinical and functional examinations and polysomnographic studies while using the ventilator. The same protocol was applied with the second device after a ten-day washout period. Baseline polysomnographs showed fragmented sleep with low percentages of deep non-REM sleep and of REM sleep, as well as respiratory patterns characterized by very high frequencies coinciding with significant desaturations. In all cases symptoms and arterial blood gas improvements were significant, with no differences between the two treatment periods. The percentages of time spent with SaO2 below 90% of reference in sleep studies were significantly lower than baseline with both ventilators. All but one patient had better tolerance of the bilevel positive airway pressure (BIPAP) support mode than of the volumetric ventilator. Our study shows that NIPPV is equally effective for patients with kyphoscoliosis whether administered with a volumetric ventilator or a BIPAP device. Subjective response and tolerance seem to be slightly better with BIPAP.

Blood Gas Analysis↗
PubMed1995

[High frequency jet ventilation combined with conventional mechanical ventilation in the treatment of adult respiratory distress syndrome].

Better understanding of the physiopathology of ventilatory mechanisms associated with ARDS and the recent re-evaluation of the iatrogenic potential of mechanical ventilation (MV) brings us closer to the best suited ventilatory mode for these patients. In severely ill ARDS patients, only a small lung volume is ventilated, and remains available for the totality of the gas exchanges (baby lung concept). The goal of MV is to restore and maintain an optimal exchange volume while limiting mechanical agression of the lung tissue. Analysis of the ARDS related pressure-volume relationship (P/V) is helpful in specifying the tolerable limits of the ventilatory pressure regimen. The lower limit (end expiratory pressure) must be kept above the lower inflexion point of the curve, in order to increase the ventilated lung volume and avoid distal airway collapse. Under this limit, gas exchanges are altered by the shunt effect, and shear stress lesions result from the repeated opening and closing of the distal airways. The upper limit (end inspiratory pressure) must be situated below the upper inflexion point of the curve, in order to avoid lesions resulting from surdistension of the alveolocapillary membranes and barotraumatisms. The only way to position MV in such a narrow pressure window, is to greatly reduce the tidal volume (VT). Though CO2 retention would inevitably occur under conventional MV conditions, high frequency ventilation (HFV) seems better adapted to these theoreotical objectives; small VT's are injected under a limited amplitude pressure regimen and a satisfactory CO2 clearance is maintained. This ventilatory mode, existing since more than 15 years, has recently benefited from many technical improvements as well as the concept of oscillating the ventilation around a selected mean pressure in the central region of the P/V curve. In the past, HFV was applied using low pressure regimens, situated below the lower inflexion point of the curve. The resulting failures are, a posteriori, explained by insufficient lung volumes, unable to maintain adequate gas exchanges. Current work is aimed at re-evaluating HFV, using higher mean airway pressure levels. Combined HFV is another advance towards the theoretical goal of restoring and maintaining optimally ventilated lung volumes. Though HFV alone can maintain lung volumes oscillating around a mean value, it cannot re-expand atelectatic areas. The small VT's used are insufficient to overcome these area's elevated opening pressures. Volume recruitment by periodic hyperinflations, or sighs, though generally considered useless in conventional MV, have been shown to be of great benefit in HFV.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed2001

Elective discontinuation of life-sustaining mechanical ventilation on a chronic ventilator unit.

Withdrawal of medical interventions has become common in the hospital for patients with terminal disease. Despite the widespread feeling that medical interventions may be futile in certain patients, many patients, families, and medical staff find withdrawal of care difficult and withdrawal of mechanical ventilation to be the most disturbing secondary to the close proximity of withdrawal and death. Presented is a 6-year retrospective review of elective withdrawal of life-sustaining mechanical ventilation on a chronic ventilator unit (CVU) in an academic nursing home. Of the 98 patients admitted to the 19-bed CVU during this period, only 13 underwent terminal weaning (TW). Statistically, these 13 patients did not differ significantly in age, gender, race, route of nutrition, decisional capacity, or length of stay on the unit compared with the 85 patients who were not terminally weaned (t-test P > .05). Stepwise logistic regression found that patients who were more alert at admission were more likely to have participated in TW (chi2 = 5.22, coefficient for alertness P < .036). The decision to terminate mechanical ventilation was made by patients in eight cases and by family in five cases. The first step in the process leading to TW was a discussion with the patient and family about plan of care, including the patient's desires for attempted resuscitation, rehospitalization, advance directives, and family contacts. Plan of care was reviewed informally in a weekly multidisciplinary round and formally, to address each patient's care plan, in a multidisciplinary family meeting on a regular basis. The second step was to address TW when brought up by the patient, family, or medical staff. A request for TW by a patient or surrogate was referred to the medical staff, who screened the patient for depression or other remediable symptoms. The third step was to refer the patient and family to another formal meeting to discuss the request for TW and, if needed, in the case of multiple family members, to allow questions to be answered and consensus to be formed. Additional meetings were scheduled as needed. The next step occurred once a consensus was reached to proceed with TW; a date and time was set to reconvene the patient, family, and anyone else who wanted to be present at the TW. The TW process began when a peripheral intravenous catheter was placed and the patient was premedicated with low doses of morphine sulfate and a benzodiazepine. After premedication, the patient was removed from the ventilator. The physician, nurse, family, and physician assistant remained at the bedside and additional morphine or benzodiazepine was given, as needed, for symptom management. Death from TW occurred in all patients, at times ranging from 2 minutes to 10.5 hours (average 6.2 hours). A mean total dose of 115 mg morphine and 14 mg diazepam was given for symptom control. There was no correlation between dose of these medications and duration of survival off the ventilator.

Adult↗
PubMed1985

Compression volume during mechanical ventilation: comparison of ventilators and tubing circuits.

Four ventilators (Puritan-Bennett MA-1 and MA-2, Emerson, and Bear I) and four commercially available disposable and nondisposable tubing circuits (Bennett nondisposable, Becton-Dickinson, Inspiron, and Life-line) were tested on a lung analog for differences in inspiratory-circuit compression volume. The compression ratio (Rc), equal to the gas volume compressed per cm H2O peak airway pressure, was calculated for each combination of ventilator and circuit at each of four compliance settings (0.15, 0.10, 0.05, 0.01 L/cm H2O) on the analog. Rc values ranged from 0.3 to 4.5 ml/cm H2O at the highest and lowest compliance settings, respectively, accounting for a reduction in delivered tidal volume of up to 20%. The Emerson ventilator with all tubing systems and the Bennett nondisposable circuit with each ventilator demonstrated slightly smaller compression volumes. Application of an inspiratory pause on the Bear I ventilator did not affect its compression characteristics. The clinical importance of compression volume and data from other ventilation systems are reviewed.

Humans↗
PubMed1986

A system for high-frequency oscillatory ventilation and intermittent mandatory ventilation in neonates.

We combined high-frequency oscillatory ventilation and intermittent mandatory ventilation, using a system composed of an Emerson airway vibrator, a Babybird 1 ventilator, and rate/pressure monitors. The Emerson device, a modified air compressor with rate controller, oscillated a small volume of gas at the airway. This device was coupled to the bird unit through a circuit of our design. Humidified fresh gas and pressure-relief valves were provided by the bird ventilator, and mean airway pressure was adjusted by its expiratory-limb venturi device or by the end-expiratory pressure control. The volume of gas delivered by the oscillator to various sites was measured with a plethysmograph tuned to high frequencies. At frequencies of 20 to 30 Hz, a 27-ml volume from the oscillator decreased to between 7 and 14 ml at the proximal airway, and to between 0.1 and 2.3 ml at the distal tip of the endotracheal tube. The magnitude of this decrease depended on the size of the endotracheal tube, the circuit resistance of the ventilator, oscillation frequency, and the position of the oscillator's expansion-chamber valve. We have used this system for over 3 yr to ventilate sick neonates safely and effectively.

Equipment Design↗