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PubMed1999

[Endotracheal complications after long-term ventilation. Noninvasive ventilation in chronic thoracic diseases as an alternative to tracheostomy].

PATIENTS AND METHODS: In this present retrospective study we examined 62 long-term ventilated patients, whose weaning from respirator failed, for endoscopic airway complications and the frequency of consecutive surgery required. Furthermore noninvasive volume-controlled intermittent ventilation was evaluated as an alternative method to tracheostomy for maintaining mechanical ventilation and weaning of patients with chest wall disorders, neuromuscular and chronic obstructive lung disease. RESULTS: 25 patients with endotracheal tube and 37 with tracheostomy who had been long-term ventilated in different intensive care units for 18 +/- 12 respectively 57 +/- 27 days (19 +/- 12 days via endotracheal tube) could be weaned successfully consequently using a volume-controlled intermittent ventilation via an individually adapted face mask. We found 2 patients of the group with endotracheal intubation (median age 59 +/- 15 years, 11 female, 14 male, median duration of mechanical ventilation via tube 18 +/- 12 days) to have visible injuries of the respiratory tract without consecutive surgery being necessary. All of them were successfully weaned from respirator via noninvasive ventilation (in 2 of them completely spontaneous breathing was re-established, 23 patients needed intermittent ventilation at home). Of the 37 patients with tracheostomy (median age 59 +/- 15 years, 15 female, 22 male, median duration of mechanical ventilation 57 +/- 27 days, tracheostomy on day 19 +/- 12) 19 cases (51%) showed endoscopically visible injuries of the respiratory tract of whom 7 cases (19%) were severe and made consecutive surgery necessary. 29 patients were discharged with noninvasive ventilation at home, 5 needed further invasive ventilation via tracheostomy and 3 patients breathed spontaneously without ventilatory support. The incidence of severe tracheal stenosis following long-term ventilation via tracheostomy was nearly 20% (1 tracheoesophageal fistula) and needed surgical treatment. CONCLUSION: As even duration of ventilation via tracheal tube and mode of ventilation before transfer to our clinic was comparable in both groups noninvasive ventilation is an appropriate alternative to tracheostomy following endotracheal intubation for maintaining ventilatory support, especially for patients with chronic ventilatory insufficiency.

Chronic Disease↗
PubMed1993

A multicenter randomized trial of high frequency oscillatory ventilation as compared with conventional mechanical ventilation in preterm infants with respiratory failure.

A multicenter randomised trial was conducted in nine neonatal centers in Japan to re-evaluate the safety and the efficacy of high frequency oscillatory ventilation using the piston type oscillator (Hummingbird) in the treatment of respiratory failure in preterm infants weighing between 750 and 2000 g at birth. A total of 92 infants were enrolled in the study. Forty-six infants were allocated to high frequency oscillatory ventilation and 46 infants to conventional mechanical ventilation. There were no differences in sex, birth weight, gestation and Apgar score between groups. The study was begun 2.0 +/- 1.6 h (mean +/- S.D.) after birth in the high frequency oscillation group and 1.7 +/- 1.5 h after birth in the conventional mechanical ventilation group. The absence of intraventricular hemorrhage was confirmed by echography in all cases before beginning ventilation. Mortality was similar in high frequency oscillatory ventilation and conventional mechanical ventilation (0 and 2%). The incidence of intraventricular hemorrhage was also similar in the high frequency and conventional mechanical ventilation groups (15 and 13% overall; 4 and 2% in grades III and IV, respectively). Nine percent of the infants in high frequency oscillatory ventilation and 13% in conventional mechanical ventilation developed bronchopulmonary dysplasia, but the difference was not significant. The frequency of air leaks was also equal in both groups. Periventricular leukomalacia was detected in 9% of infants on conventional mechanical ventilation and 2% on high frequency oscillation, but the difference was not significant. Mean airway pressure was significantly higher in the high frequency oscillatory ventilation group and the infants on high frequency oscillation showed a significantly higher arterial to alveolar oxygen tension ratio after 6 h of treatment. These results suggest that high frequency oscillatory ventilation does not increase the risk of severe complications such as air leaks, intraventricular hemorrhage or periventricular leukomalacia when it is used by experienced neonatologists. Indeed high frequency oscillatory ventilation helps provide better oxygenation with higher mean airway pressure without increasing the risk of bronchopulmonary dysplasia and severe complications such as air leaks and intraventricular hemorrhage.

Bronchopulmonary Dysplasia↗
PubMed1997

High-frequency oscillatory ventilation with partial liquid ventilation in a model of acute respiratory failure.

OBJECTIVE: To determine whether there is an improvement in oxygenation when partial liquid ventilation and high-frequency oscillatory ventilation are combined in the treatment of acute lung injury, compared with high-frequency oscillatory ventilation alone. DESIGN: Controlled animal trial. SETTING: Research laboratory in a university setting. SUBJECTS: Ten 3-kg piglets. INTERVENTIONS: Anesthetized piglets underwent high-frequency oscillatory ventilation, with mean airway pressure of 20 cm H2O, before induction of acute lung injury with repeated saline lavage. When PaO2 values were < 100 torr (< 13.3 kPa), five animals were randomized to receive escalating doses (3, 15, and 30 mL/kg) of perflubron at 60-min intervals. The other five animals remained on high-frequency oscillatory ventilation only. Sham dosing was performed at 60-min intervals in these animals. Arterial blood gases were obtained in both groups at baseline, after injury, and after perflubron and sham doses. MEASUREMENTS AND MAIN RESULTS: Statistically significant improvements in oxygenation were demonstrated in animals that received 3 mL/kg of perflubron with high-frequency oscillatory ventilation compared with animals receiving high-frequency oscillatory ventilation alone (253 +/- 161 vs. 90 +/- 30 torr [33.65 +/- 21.46 vs. 12.0 +/- 4.0 kPa], p < .05). Improvements in oxygenation with additional administration of perflubron were not greater than the improvements seen in the high-frequency oscillatory ventilation-only group. PaCO2 and pH were similar in both groups at all times. No hemodynamic compromise occurred in either group of animals. CONCLUSIONS: The combination of low-dose perflubron with high-frequency oscillatory ventilation leads to more rapid improvement in arterial oxygenation than high-frequency oscillatory ventilation alone, in a piglet model of acute lung injury. Although the group receiving high-frequency oscillatory ventilation alone eventually achieved PaO2 values that were equivalent to the group receiving high-frequency ventilation and perflubron, the combination of perflubron with high-frequency oscillatory ventilation may permit effective oxygenation and ventilation at lower mean airway pressures by facilitating alveolar expansion and decreasing intrapulmonary shunt.

Analysis of Variance↗
PubMed1994

Prospective, randomized comparison of high-frequency oscillatory ventilation and conventional mechanical ventilation in pediatric respiratory failure.

OBJECTIVE: To compare the effectiveness of high-frequency oscillatory ventilation with conventional mechanical ventilation in pediatric patients with respiratory failure. SETTING: Five tertiary care pediatric intensive care units. DESIGN: A prospective, randomized, clinical study with crossover. PATIENTS: Seventy patients with either diffuse alveolar disease and/or airleak syndrome were randomized to receive high-frequency oscillatory ventilation or conventional mechanical ventilation. INTERVENTIONS: Patients randomized to receive high-frequency oscillatory ventilation were managed, using a strategy that consisted of aggressive increases in mean airway pressure to attain the "ideal" lung volume and to achieve an arterial oxygen saturation of > or = 90%, with an FIO2 of < or = 0.6. Patients who were randomized to receive conventional mechanical ventilation were treated with a strategy that utilized increases in end-expiratory pressure and inspiratory time to increase mean airway pressure and to limit increases in peak inspiratory pressure. Target blood gas values were the same for both groups. Crossover to the alternate ventilator was required if the patient met defined criteria for treatment failure. MEASUREMENTS AND MAIN RESULTS: Physiologic data and ventilatory parameters were collected prospectively at predetermined intervals after randomization. Airleak Scores were derived daily, based on the chest radiograph and the patient's clinical condition. In the high-frequency oscillatory ventilation group, the PaO2/PAO2 ratio increased significantly and the oxygenation index (mean airway pressure x FIO2 x 100/PaO2) decreased significantly over time. There were no differences between the groups in duration of mechanical ventilation, frequency of airleak, Airleak Scores, or 30-day survival rates. Significantly fewer patients treated with high-frequency oscillatory ventilation required supplemental oxygenation at 30 days compared with patients managed with conventional ventilation. When ventilatory subgroups were compared, the patients managed with high-frequency oscillation only had significantly better ranked outcomes than patients managed with conventional ventilation only. CONCLUSIONS: Our results indicate that high-frequency oscillatory ventilation, utilizing an aggressive volume recruitment strategy, results in significant improvement in oxygenation compared with a conventional ventilatory strategy designed to limit increases in peak airway pressures. Furthermore, despite the use of higher mean airway pressures, the optimal lung volume strategy used in this study was associated with a lower frequency of barotrauma, as indicated by requirement for supplemental oxygen at 30 days, and improved outcome compared with conventional mechanical ventilation.

Child↗
PubMed2002

High-frequency oscillatory ventilation versus conventional mechanical ventilation for very-low-birth-weight infants.

BACKGROUND: The efficacy and safety of early high-frequency oscillatory ventilation as compared with conventional synchronized intermittent mandatory ventilation for the treatment of infants with very low birth weight have not been established. METHODS: We conducted a randomized, multicenter clinical trial to determine whether infants treated with early high-frequency oscillatory ventilation were more likely than infants treated with synchronized intermittent mandatory ventilation to be alive without requiring supplemental oxygen at 36 weeks of postmenstrual age. Eligible infants weighed 601 to 1200 g at birth, were less than four hours of age, had received one dose of surfactant, and required ventilation with a mean airway pressure of at least 6 cm of water and a fraction of inspired oxygen of at least 0.25. Infants were stratified according to birth weight and exposure to prenatal corticosteroids and then randomly assigned to high-frequency oscillatory ventilation or synchronized intermittent mandatory ventilation. Ventilation was managed according to protocols designed to optimize lung inflation and blood gas values. RESULTS: Five hundred infants were enrolled in the study. Infants randomly assigned to high-frequency oscillatory ventilation were successfully extubated earlier than infants assigned to synchronized intermittent mandatory ventilation (P<0.001). Of infants assigned to high-frequency oscillatory ventilation, 56 percent were alive without a need for supplemental oxygen at 36 weeks of postmenstrual age, as compared with 47 percent of those receiving synchronized intermittent mandatory ventilation (P=0.046). There was no difference between the groups in the risk of intracranial hemorrhage, cystic periventricular leukomalacia, or other complications. CONCLUSIONS: There was a small but significant benefit of high-frequency oscillatory ventilation in terms of the pulmonary outcome for very-low-birth-weight infants without an increase in the occurrence of other complications of premature birth.

Age Factors↗
PubMed2002

Early surfactant administration with brief ventilation vs selective surfactant and continued mechanical ventilation for preterm infants with or at risk for RDS.

BACKGROUND: Both early and prophylactic surfactant replacement therapy compared with later selective surfactant administration reduces mortality and pulmonary complications in ventilated infants with respiratory distress syndrome (RDS). Continuous distending pressure (CDP) has also been shown to improve clinical outcomes in preterm infants with RDS. OBJECTIVES: To compare two treatment strategies in preterm infants with, or at risk for, RDS: early surfactant administration with brief mechanical ventilation (less than 1 hour) followed by extubation, vs later, selective surfactant administration, continued mechanical ventilation and extubation from low respiratory support. Two populations of infants receiving early surfactant were considered: spontaneously breathing infants with signs of RDS (surfactant administration during evolution of RDS prior to requiring intubation for respiratory failure) and infants at high risk for RDS (prophylactic surfactant administration within 15 minutes after birth). SEARCH STRATEGY: Searches were made of the Oxford Database of Perinatal trials, MEDLINE (1966-December 2001), CINAHL (1982-December 2001), EMBASE (1980-December 2001), Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002), Pediatric Research (1990-2001), abstracts, expert informants and hand searching. No language restrictions were applied. SELECTION CRITERIA: Randomized or quasi-randomized controlled clinical trials comparing early surfactant administration with planned brief mechanical ventilation (less than one hour) followed by extubation, vs selective surfactant administration, continued mechanical ventilation and extubation from low respiratory support. DATA COLLECTION AND ANALYSIS: Data were sought regarding effects on incidence of mechanical ventilation (ventilation continued or initiated beyond one hour after surfactant administration), incidence of bronchopulmonary dysplasia (BPD, need for oxygen at 28 days of age), incidence of chronic lung disease (CLD, need for oxygen at 36 weeks' post-conceptional age), mortality (neonatal mortality < 28 days and mortality prior to hospital discharge), duration of mechanical ventilation, duration of hospitalization, time in oxygen, duration of respiratory support (including CPAP and nasal cannula), number of patients receiving surfactant, number of surfactant doses administered per patient, incidence of air leak syndromes (pulmonary interstitial emphysema, pneumothorax), incidence of pulmonary hemorrhage, and other complications of prematurity. Data analyses were performed in accordance with the standards of the Cochrane Neonatal Review Group. MAIN RESULTS: Only one randomized controlled clinical trial met selection criteria and was included in this review (Verder 1994). In this study of infants with signs of RDS, intubation and early surfactant therapy followed by extubation to nasal CPAP (NCPAP) compared with later, selective surfactant administration was associated with a lower incidence of mechanical ventilation (ventilation continuing for one hour or more after surfactant administration in the early surfactant group or initiated for respiratory insufficiency or apnea in either group [RR 0.51, 95% CI 0.32, 0.76]). A larger proportion of infants in the early surfactant group received surfactant than in the selective surfactant group [RR 1.74, 95% CI 1.30, 2.33]. The number of surfactant doses per patient was significantly greater among patients randomized to the early surfactant group [MD 0.51, 95% CI 0.32, 0.70]. Trends towards a decreased incidence of mortality, and a higher rate of patent ductus arteriosus requiring treatment were seen in the early surfactant group. There was no evidence of effect on median time in oxygen, duration of mechanical ventilation, or incidence of BPD (oxygen at 28 days). REVIEWER'S CONCLUSIONS: Early surfactant replacement therapy with extubation to NCPAP compared with later, selective surfactant replacement and continued mechanical ventilation with extubation from low ventilator support is associated with a reduced need for mechanical ventilation and increased utilization of exogenous surfactant therapy. These conclusions are based on findings from one small randomized clinical trial. Additional randomized trials are needed and are underway.

Combined Modality Therapy↗
PubMed1997

[Ventilation during cardiopulmonary resuscitation (CPR). A literature study and analysis of ventilation strategies].

In a recently published German multicenter study, 25% of the patients with witnessed cardiac arrest outside the hospital were resuscitated successfully and discharged from the hospital. Approximately 100,000 people suffer a fatal cardiac arrest in Germany annually, which is approximately tenfold the number of deaths from motor vehicle accidents. Cardiopulmonary resuscitation (CPR) performed by bystanders is an important part of the chain of survival to minimize the time interval without artificial circulation and ventilation in a cardiac arrest victim. This is especially important in areas with long response times of the emergency medical service (EMS). Early examples of ventilation have been described throughout history. References to mouth-to-mouth ventilation (MTMV) are found in the Bible, in a description of the resuscitation of a coal miner in 1744, and in an experiment in 1796 demonstrating that exhaled gas was safe for breathing. In 1954, Elam and colleagues described artificial respiration with the exhaled gas of a rescuer using a mouth-to-mask ventilation method. The modern CPR era started with the combination of MTMV and chest compressions 35 years ago. However, the value of MTMV is currently under discussion because of a widespread fear of transmission of infectious diseases. Healthcare professionals have stated in several studies that they may withhold MTMV when confronted with a cardiac arrest in a stranger. Although an infection with Mycobacterium tuberculosis is more likely than one with HIV via MTMV, the fear of the public is understandable. An expert committee of the American Heart Association stated that MTMV may be omitted in the initial phase of cardiac arrest, and considered recommending chest compressions only if the EMS will arrive rapidly. In paralyzed volunteers, however, ventilation induced by chest compressions was not able to provide sufficient gas exchange, especially when the airway was not protected. Laboratory investigations studying ventilation during CPR showed controversial results; in one animal model of cardiac arrest with muscle paralysis, chest compressions were not sufficient for adequate gas exchange, but active compression-decompression CPR achieved reasonable ventilation. Animal models that prevented gasping during cardiac arrest required ventilation during CPR, whereas gasping animals seemed to be satisfactorily ventilated with chest compressions alone. The question whether spontaneous gasping after cardiac arrest in humans may be sufficient for oxygenation and carbon dioxide elimination is debatable and remains unanswered at this time. When cardiac arrest is monitored, frequent coughing by the patient may maintain artificial ventilation and circulation for 30 s. The strategy to compress the thorax first and then maintain the airway and perform ventilation may only have an advantage for the first 30 s of CPR. Therefore, MTMV remains the therapy of choice to ventilate the victim of cardiac arrest. If a rescuer chooses to not perform MTMV, at least chest compressions should be administered. During ventilation with an unprotected airway, tidal volumes of 0.5 l instead 0.8-1.2 l may have an advantage. This strategy would decrease the inspiratory flow rate and, therefore, peak airway inflation pressure, which is associated with stomach inflation. Animal models indicate that lower esophageal sphincter pressure may decrease rapidly to 5 cm H2O during cardiac arrest, which may further increase the importance of a low peak airway pressure during ventilation with an unprotected airway. Gastric inflation may cause, besides regurgitation, aspiration, and pneumonia, an increased intragastric pressure, which may push up the diaphragm, decrease lung compliance, and induce a vicious circle of hypoventilation and stomach inflation.(ABSTRACT TRUNCATED)

Cardiopulmonary Resuscitation↗
PubMed2004

Ventilator strategies for posttraumatic acute respiratory distress syndrome: airway pressure release ventilation and the role of spontaneous breathing in critically ill patients.

PURPOSE OF REVIEW: Patients who experience severe trauma are at increased risk for the development of acute lung injury and acute respiratory distress syndrome. The management strategies used to treat respiratory failure in this patient population should be comprehensive. Current trends in the management of acute lung injury and acute respiratory distress syndrome consist of maintaining acceptable gas exchange while limiting ventilator-associated lung injury. RECENT FINDINGS: Currently, two distinct forms of ventilator-associated lung injury are recognized to produce alveolar stress failure and have been termed low-volume lung injury (intratidal alveolar recruitment and derecruitment) and high-volume lung injury (alveolar stretch and overdistension). Pathologically, alveolar stress failure from low- and high-volume ventilation can produce lung injury in animal models and is termed ventilator-induced lung injury. The management goal in acute lung injury and acute respiratory distress syndrome challenges clinicians to achieve the optimal balance that both limits the forms of alveolar stress failure and maintains effective gas exchange. The integration of new ventilator modes that include the augmentation of spontaneous breathing during mechanical ventilation may be beneficial and may improve the ability to attain these goals. SUMMARY: Airway pressure release ventilation is a mode of mechanical ventilation that maintains lung volume to limit intra tidal recruitment /derecruitment and improves gas exchange while limiting over distension. Clinical and experimental data demonstrate improvements in arterial oxygenation, ventilation-perfusion matching (less shunt and dead space ventilation), cardiac output, oxygen delivery, and lower airway pressures during airway pressure release ventilation. Mechanical ventilation with airway pressure release ventilation permits spontaneous breathing throughout the entire respiratory cycle, improves patient comfort, reduces the use of sedation, and may reduce ventilator days.

Continuous Positive Airway Pressure↗
PubMed2004

Assist-control mechanical ventilation attenuates ventilator-induced diaphragmatic dysfunction.

Controlled mechanical ventilation induced a profound diaphragm muscle dysfunction and atrophy. The effects of diaphragmatic contractions with assisted mechanical ventilation on diaphragmatic isometric, isotonic contractile properties, or the expression of muscle atrophy factor-box (MAF-box), the gene responsible for muscle atrophy, are unknown. We hypothesize that assisted mechanical ventilation will preserve diaphragmatic force and prevent overexpression of MAF-box. Studying sedated rabbits randomized equally into control animals, those with 3 days of assisted ventilation, and those with controlled ventilation, we assessed in vitro diaphragmatic isometric and isotonic contractile function. The concentrations of contractile proteins, myosin heavy chain isoform, and MAF-box mRNA were measured. Tetanic force decreased by 14% with assisted ventilation and 48% with controlled ventilation. Maximum shortening velocity tended to increase with controlled compared with assisted ventilation and control. Peak power output decreased 20% with assisted ventilation and 41% with controlled ventilation. Contractile proteins were unchanged with either modes of ventilation; myosin heavy chain 2X mRNA tended to increase and that of 2A to decrease with controlled ventilation. MAF-box gene was overexpressed with controlled ventilation. We conclude that preserving diaphragmatic contractions during mechanical ventilation attenuates the force loss induced by complete inactivity and maintains MAF-box gene expression in control.

Actins↗
PubMed1997

Impact of Room Ventilation Rates on Mouse Cage Ventilation and Microenvironment.

To assess the impact of room ventilation on animal cage microenvironment, intracage ventilation rate, temperature, humidity, and concentrations of carbon dioxide and ammonia were monitored in nonpressurized, bonnet-topped mouse cages. Cages on the top, middle, and bottom rows of a mouse rack were monitored at room ventilation rates of 0, 5, 10, and 20 air changes/h (ACH). Ventilation inside the animal cage increased somewhat from 12.8 to 18.9 ACH as room ventilation rate in- creased from 0 to 20 ACH, but the differences were not statistically significant, and most of the increase occurred in cages in the top row nearest to the fresh air supply. Cages containing mice had ventilation rate between 10 and 15 ACH even when room ventilation was reduced to 0 ACH; this ventilation is a result of the thermal heat load of the mice. After 6 days of soiled bedding, intracage ammonia concentration was c 3 ppm at all room ventilation rates and was not affected by increasing room ventilation. Temperature inside cages did not change with increasing ventilation. Humidity inside cages significantly decreased with increasing ventilation, from 55% relative humidity at 5 ACH to 36% relative humidity at 20 ACH. Carbon dioxide concentration decreased from 2,500 ppm to 1,900 ppm when ventilation rate increased from 5 ACH to 10 ACH, but no further significant decrease was observed at 20 ACH. In conclusion, increasing the room ventilation rate higher than 5 ACH did not result in significant improvements in the cage microenvironment.

Journal Article↗
PubMed2001

Patient-ventilator interactions in new modes of patient-triggered ventilation.

Recently, synchronized modes of conventional mechanical ventilation became available for neonatal ventilatory support, but there has been little information regarding details of patient-ventilator interactions during pressure support, volume support, or any other volume-targeted modes of synchronized ventilation in newborn infants. Our objective was to obtain comparative data on patient-ventilator interactions and stability of delivered tidal volume (V(T)) for the different modes of synchronized mechanical ventilation in stable ventilated newborn infants. We examined the effects of pressure support ventilation (PSV) and volume guarantee (VG) modes of a prototype Dräger Babylog ventilator on peak and mean airway pressures (PIP and Paw), inspiratory time (t(in)), and V(T) in 23 ventilated newborn infants. Twelve infants were studied while on assist/control (AC) and 11 on synchronized intermittent mandatory ventilation (SIMV). Mean birth weight was 1,650 +/- 1,180 g, gestational age 31 +/- 6 weeks, and age at time of study was 19 +/- 26 days. Data for 400-600 breaths from each infant were downloaded directly from the ventilator pressure and volume-monitoring module, and analyzed using ANOVA for repeated measures. Mean values and breath-to-breath variability were compared for 20-min periods of AC or SIMV followed by PSV, PSV+VG, and back to baseline AC or SIMV. PSV and PSV+VG led to shorter t(in) and thus to lower Paw, compared to AC. Mean PIP was similar across all AC modes but more variable during VG, reflecting the servocontrol of PIP. V(T) did not differ between AC modes, but was significantly less variable with VG added. PSV and PSV+VG led to lower and less variable PIP and Paw, compared to SIMV, because t(in) was shorter and every breath was supported in PSV and PSV+VG. V(T) was similar in SIMV, PSV, and PSV+VG, but less variable with PSV+VG. Arterial blood gas tensions were similar across all ventilation modes. We conclude that the ventilator prototype functioned as intended. Breath-to-breath tidal volume variability was significantly reduced in VG modes, although not completely eliminated.

Blood Gas Analysis↗
PubMed1998

Pressure- versus volume-cycled ventilation in liquid-ventilated neonatal piglet lungs.

BACKGROUND/PURPOSE: If the goal of partial liquid ventilation (PLV) with perfluorocarbons in the management of respiratory failure is to improve dynamic lung compliance (Cdyn) and pulmonary vascular resistance (PVR) while sustaining O2 delivery, the optimal ventilatory management is unclear. The authors asked if volume-cycled or pressure-limited ventilation had different effects on PVR, cardiac index (CI), and Cdyn in uninjured and injured neonatal piglet lungs. METHODS: Anesthetized piglets (6 to 8 kg) were ventilated after tracheostomy. Cdyn was measured by in-line Fleisch pneumotach/PC data acquisition terminal. Thermodilution instrumentation allowed determination of both CI and PVR. Volume-control or pressure-limited ventilation was established in uninjured or injured (surfactant deficiency induced by saline lavage at 18 mL/kg) animals. After a stable 30-minute baseline, animals were assigned randomly to one of four groups: group I (n = 9), uninjured animals plus volume-cycled ventilation (intermittent mandatory ventilation [IMV], 10 bpm; tidal volume [TV], 15 mL/kg, positive end-expiratory pressure [PEEP], 5 cm H2O; FIO2, 1.0; and PLV for 150 minutes); group II (n = 9), uninjured animals plus pressure-limited ventilation (IMV, 10 bpm; peak inspiratory pressure (PIP), 25 cm H2O, PEEP, 5 cm H2O, FIO2, 1.0; and PLV for 150 minutes); group III (n = 7), injured animals plus volume-cycled ventilation (IMV, 10 bpm; TV, 15 mL/kg; PEEP, 5 cm H2O; FIO2, 1.0 for 30 minutes, followed by saline injury for group IV (n = 7), injured animals plus pressure-limited ventilation (IMV, 10 bpm; PIP, 25 cm H2O; PEEP, 5 cm H2O; FIO2, 1.0 for 30 minutes, followed by saline injury, and PLV rescue). Comparison within and between groups was accomplished by repeated measures analysis of variance (ANOVA) with Tukey correction. RESULTS: There was no significant difference between volume-cycled or pressure-limited ventilation in healthy lungs; however, in the setting of lung injury, dynamic compliance was 1.44 +/- 0.15 after 180 minutes in the volume-cycled group and 0.91 +/- 0.10 in the pressure-limited group after the same interval (mL/cm H2O x kg +/- SEM). Similarly, PVR was 100 +/- 6 in the volume-cycled group and 145 +/- 12 in the pressure-limited group after 180 minutes of lung injury (mm Hg/L/kg x min +/- SEM). Cardiac index declined significantly in all groups independent of ventilatory mode. CONCLUSIONS: These results suggest that in the setting of lung injury, Cdyn and PVR improved significantly when volume-cycled, compared with pressure-limited ventilation was used. Although no difference existed between ventilatory modes in healthy lungs, pressure-limited ventilation, when combined with PLV in injured lungs, had adverse effects on lung compliance and pulmonary vascular resistance. Volume-cycled ventilation may optimize the ability of perfluorocarbon to recruit collapsed or atelectatic lung regions.

Analysis of Variance↗
PubMed2003

Effect on respiratory function of pressure support ventilation versus synchronised intermittent mandatory ventilation in preterm infants.

Our objective was to compare the effects of pressure support ventilation and synchronized intermittent mandatory ventilation on respiratory function in preterm babies. Twenty preterm infants (mean gestational age, 29 weeks; mean weight at study, 1,354 g) were evaluated. Patients received two repeated cycles of synchronized intermittent mandatory ventilation, alternated with pressure support ventilation, for a total of four alternated phases, each phase lasting 4 hr. Spontaneous respiratory rate, tidal volume, minute volume, and mean airway pressure were recorded hourly. The tidal volume released by the ventilator was limited to 6 ml/kg. During the two pressure support ventilation phases, a statistically significant reduction of respiratory rate and a significant increase of tidal and minute volume were noted, as compared to the two synchronized intermittent mandatory ventilation periods. Mean airway pressure significantly increased only after the first shift from synchronized intermittent mandatory ventilation to pressure support ventilation. The changes of minute volume and respiratory rate observed during pressure support ventilation did not persist after the return to synchronized intermittent mandatory ventilation. In conclusion, pressure support ventilation, as compared to synchronized intermittent mandatory ventilation, seemed to improve respiratory function in preterm infants.

Birth Weight↗
PubMed1996

Prospective, randomized study of ventilator-associated pneumonia in patients with one versus three ventilator circuit changes per week.

OBJECTIVE: To assess the effect on the rate of ventilator-associated pneumonia (VAP) of decreasing the frequency of ventilator circuit changes from three times to once per week. DESIGN: Prospective, randomized trial. SETTING: Medical intensive care unit (MICU), a 12-bed, critical-care internal medicine unit, and neurosciences intensive care unit (NICU), a 21-bed, predominantly adult neurosurgical unit, of an urban university hospital. PATIENTS: All 447 patients requiring mechanical ventilation during October 1992 through June 1993. INTERVENTION: Patients were allocated randomly on the basis of permanent medical record numbers: those with odd numbers had circuits changed three times per week, those with even numbers once per week. Intensive-care-unit surveillance was conducted in accordance with definitions and methods of the National Nosocomial Infections Surveillance System. RESULTS: In the MICU, the one-change-per-week group had a VAP rate of 7.3 per 1,000 ventilator days, versus 5.9 for the three-per-week group (P = .6). In the NICU, the one-change-per-week group had a rate of 12.2 per 1,000 ventilator days, versus 12.6 for the three-per-week group (P = .9). Considering patients in both units ventilated for no more than 7 days, the one-change-per-week group had a VAP rate of 5.9 per 1,000 ventilator days, versus 9.0 per 1,000 for the three-changes-per-week group (odds ratio [OR], 0.65; 95% confidence interval [CI95], 0.25 to 1.69). Including patients in the two units maintained on mechanical ventilation for more than 7 days, the one-change-per-week group had a VAP rate of 13.2 per 1,000 ventilator days, versus 9.6 per 1,000 for the three-changes-per-week group (OR, 1.37; CI95, 0.71 to 2.65). CONCLUSIONS: Decreasing the frequency of ventilator circuit changes from three times to once per week had no adverse effect on the overall rate of VAP. Less frequent ventilator circuit changes may decrease the incidence of VAP among patients ventilated for no more than 1 week. However, the incidence of VAP may be higher among patients with once weekly circuit changes ventilated for more than 1 week.

Adult↗
PubMed2001

Effects of decreasing the frequency of ventilator circuit changes to every 7 days on the rate of ventilator-associated pneumonia in a Beijing hospital.

INTRODUCTION: We investigated whether decreasing ventilator circuit changes from every 2 days to every 7 days would impact ventilator-associated pneumonia rates at our institution. METHODS: All mechanically ventilated patients at Peking Union Medical College Hospital were studied over a 21 month period. From March 1998 to February 1999, ventilator circuits were changed every 2 days, and from June through December 1999, ventilator circuits were changed every 7 days. Nosocomial pneumonia was identified using the criteria of the Centers for Disease Control. RESULTS: In the 2-day-change group, there were 2,277 ventilator-patient days and 38 patients developed pneumonia, resulting in a pneumonia rate of 16.7 cases per 1,000 ventilator days. The 7-day-change group accumulated 972 ventilator days and 8 patients contracted pneumonia, resulting in a pneumonia rate of 8.2 cases per 1,000 ventilator days. The pneumonia rate was significantly lower in the 7-day-change group (p = 0.007). To standardize for seasonal variability, we compared results from the same seasonal time frames (June to December 1998 for the 2-day-change group, and June to December 1999 for the 7-day-change group), and obtained similar findings: during those periods, pneumonia rates were 24.2 cases per 1,000 ventilator days for the 2-day-change group and 8.9 cases per 1,000 ventilator days for the 7-day-change group (p = 0.001). CONCLUSIONS: A circuit change interval of 7 days had a lower risk of ventilator-associated pneumonia than a 2-day change interval. Therefore, ventilator circuits can be safely changed every 7 days in our setting.

Cross Infection↗
PubMed1994

Differences in end-tidal carbon dioxide and breathing patterns in ventilator-dependent patients using pressure support ventilation.

BACKGROUND: Although several investigators have assessed the effects of pressure support ventilation on tidal volume and breathing patterns, none have investigated the combination of breathing patterns and end-tidal carbon dioxide in ventilator-dependent patients. OBJECTIVES: To determine the differences in end-tidal carbon dioxide and breathing patterns at varying pressure support ventilation levels in ventilator-dependent patients. METHODS: Breathing patterns were measured with a plethysmograph and a ventilator. End-tidal carbon dioxide was measured by connecting the capnography sampler to the exhalation port of intubated patients. All equipment was connected to a five-channel recorder for data collection. The respiratory rate, tidal volume, minute ventilation, end-tidal carbon dioxide concentration, and chest and abdominal movement were recorded at 10-minute intervals at four pressure support ventilation levels (0, 10, 15, and 20 cm H2O). RESULTS: As pressure support ventilation increased, the respiratory rate, end-tidal carbon dioxide concentration, and asynchronous movement of chest and abdomen decreased. Tidal volume increased with higher pressure support ventilation levels. CONCLUSIONS: Pressure support ventilation prevents asynchronous chest and abdominal movement and lowers the level of end-tidal carbon dioxide. Pressure support ventilation offers clinicians a way to lower the elevated carbon dioxide level that often occurs in critically ill patients. Increasing tidal volume and reducing the work of breathing by using pressure support ventilation may reduce diaphragm fatigue in ventilator-dependent patients.

Abdominal Muscles↗
PubMed2005

Ventilator settings as a risk factor for acute respiratory distress syndrome in mechanically ventilated patients.

OBJECTIVE: A single-center retrospective study initial recently identified ventilator settings as a major risk factor for the development of acute respiratory distress syndrome (ARDS) in mechanically ventilated patients who do not have ARDS from the outset. We tested this hypothesis in a larger sample of patients prospectively enrolled in a multicenter study on mechanical ventilation. DESIGN AND SETTING: From a large international mechanical ventilation study database we identified patients who required mechanical ventilation for 48 h or more but did not have ARDS at the onset of mechanical ventilation. We extracted information on demographics, initial severity of illness, ventilator settings and major underlying ARDS risk factors. Primary outcome was development of ARDS after the onset of mechanical ventilation. MEASUREMENTS AND RESULTS: Of 3,261 mechanically ventilated patients who did not have ARDS at the outset 205 (6.2%) developed ARDS 48 h or more after the onset of mechanical ventilation. Multivariate logistic regression analysis adjusted for baseline patient characteristics (age, gender, Simplified Acute Physiology Score, hypoxemia) and underlying ARDS risk factors (sepsis, trauma, pneumonia) found the development of ARDS to be associated with the initial ventilator settings: high tidal volume (odds ratio 2.6 for tidal volume>700 ml), high peak airway pressure (odds ratio 1.6 for peak airway pressure>30 cmH2O), and high positive end-expiratory pressure (odds ratio 1.7 for end-expiratory pressure>5 cmH2O). CONCLUSIONS: The association with the potentially injurious initial ventilator settings, in particular large tidal volumes, suggests that ARDS in mechanically ventilated patients is in part a preventable complication. This hypothesis needs to be tested in a prospective study.

Female↗
PubMed1997

Computer-controlled minute ventilation in preterm infants undergoing mechanical ventilation.

INTRODUCTION: Computer-controlled minute ventilation (CCMV) continuously adjusts the ventilator rate to changes in spontaneous respiratory drive and pulmonary mechanics to maintain a preset total minute ventilation. HYPOTHESIS: We hypothesized that CCMV would maintain ventilation and oxygenation with fewer mechanical breaths than conventional intermittent mandatory ventilation in very low birth weight infants. METHODS: Very low birth weight infants in clinically stable condition who were undergoing mechanical ventilation were enrolled. The number of mechanical breaths, total and mechanical expiratory minute ventilation, mean airway pressure, oxygen hemoglobin saturation by pulse oximetry, and transcutaneous partial carbon dioxide and partial oxygen tensions were obtained during intermittent mandatory ventilation and CCMV (45 to 60 minutes) and compared by paired t test. RESULTS: Fifteen infants were studied. Birth weight (median, range) was 700 gm (550 to 1205 gm), gestational age 26 weeks (23 to 34 weeks), age 21 days (3 to 50 days). When switched from intermittent mandatory ventilation to CCMV, the number of mechanical breaths was reduced (15 +/- 2.8 to 8.6 +/- 2.9 breaths per minute, p < 0.001), leading to lower airway pressure (3.97 +/- 1.00 to 3.45 +/- 1.00 cm H2O, p < 0.001) and lower expiratory minute ventilation generated by the mechanical ventilator (116 +/- 31 to 65 +/- 28 ml/min per kilogram, p < 0.001), while total expiratory minute ventilation remained unchanged. Mean transcutaneous partial carbon dioxide and oxygen tensions, oxygen hemoglobin saturation, and the time spent within different oxygen hemoglobin saturation ranges did not differ between both ventilatory modes. CONCLUSION: CCMV maintained adequate ventilation and oxygenation with lower mechanical ventilatory support than IMV. CCMV may reduce barotrauma and chronic lung disease during long-term use.

Down-Regulation↗