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PubMed2005

Effect of ventilation strategy and surfactant on inflammation in experimental pneumonia.

This study explored, the inflammatory response during experimental pneumonia in surfactant-depleted animals as a function of ventilation strategies and surfactant treatment. Following intratracheal instillation of Group B streptococci (GBS), surfactant-depleted piglets were treated with conventional (positive-end expiratory pressure (PEEP) of 5 cmH2O, tidal volume 7 mL x kg(-1)) or open lung ventilation. During the latter, collapsed alveoli were recruited by applying high peak inspiratory pressures for a short period of time, combined with high levels of PEEP and the smallest possible pressure amplitude. Subgroups in both ventilation arms also received exogenous surfactant. Conventionally ventilated healthy animals receiving GBS and surfactant-depleted animals receiving saline served as controls. In contrast with both control groups, surfactant-depleted animals challenged with GBS and conventional ventilation showed high levels of interleukin (IL)-8, tumour necrosis factor (TNF)-alpha and myeloperoxidase in bronchoalveolar lavage fluid after 5 h of ventilation. Open lung ventilation attenuated this inflammatory response, but exogenous surfactant did not. Systemic dissemination of the inflammatory response was minimal, as indicated by low serum levels of IL-8 and TNF-alpha. In conclusion, the current study indicates that the ventilation strategy, but not exogenous surfactant, is an important modulator of the inflammation during Group B streptococci pneumonia in mechanically ventilated surfactant-depleted animals.

Animals↗

PubMed2005

Erythropoietin response in critically ill mechanically ventilated patients: a prospective observational study.

INTRODUCTION: Anemia is a common problem in critically ill patients. The etiology of anemia of critical illness is often determined to be multifactorial in the clinical setting, but the pathophysiology remains to be elucidated. Erythropoietin (EPO) is an endogenous glycoprotein hormone that serves as the primary stimulus for erythropoiesis. Recent evidence has demonstrated a blunted EPO response as a factor contributing to anemia of critical illness in specific subsets of patients. Critically ill patients requiring mechanical ventilation who exhibit anemia have not been the subject of previous studies. Our goal was to evaluate the erythropoietic response to anemia in the critically ill mechanically ventilated patient. METHODS: A prospective observational study was undertaken in the medical intensive care unit of a tertiary care, military hospital. Twenty patients admitted to the medical intensive care unit requiring mechanical ventilation for at least 72 hours were enrolled as study patients. EPO levels and complete blood count were measured 72 hours after admission and initiation of mechanical ventilation. Admission clinical and demographic data were recorded, and patients were followed for the duration of mechanical ventilation. Twenty patients diagnosed with iron deficiency anemia in the outpatient setting were enrolled as a control population. Control patients had baseline complete blood count and iron panel recorded by primary care physicians. EPO levels were measured at the time of enrollment in conjunction with complete blood count. RESULTS: The mean EPO level for the control population was 60.9 mU/ml. The mean EPO level in the mechanically ventilated patient group was 28.7 mU/ml, which was significantly less than in the control group (P = 0.035). The mean hemoglobin value was not significantly different between groups (10.6 g/dl in mechanically ventilated patients versus 10.2 g/dl in control patients; P > 0.05). CONCLUSION: Mechanically ventilated patients demonstrate a blunted EPO response to anemia. Further study of therapies directed at treating anemia of critical illness and evaluating its potential impact on mechanical ventilation outcomes and mortality is warranted.

Aged↗

PubMed1999

A new prototype of an electronic jet-ventilator and its humidification system.

BACKGROUND: Adequate humidification in long-term jet ventilation is a critical aspect in terms of clinical safety. AIM: To assess a prototype of an electronic jet-ventilator and its humidification system. METHODS: Forty patients with respiratory insufficiency were randomly allocated to one of four groups. The criterion for inclusion in this study was respiratory insufficiency exhibiting a Murray score above 2. The four groups of patients were ventilated with three different respirators and four different humidification systems. Patients in groups A and B received superimposed high-frequency jet ventilation (SHFJV) by an electronic jet-ventilator either with (group A) or without (group B) an additional humidification system. Patients in group C received high-frequency percussive ventilation (HFPV) by a pneumatic high-frequency respirator, using a hot water humidifier for warming and moistening the inspiration gas. Patients in group D received conventional mechanical ventilation using a standard intensive care unit respirator with a standard humidification system. SHFJV and HFPV were used for a period of 100 h (4days). RESULTS: A significantly low inspiration gas temperature was noted in patients in group B, initially (27.2 +/- 2.5 degrees C) and after 2 days (28.0 +/- 1.6 degrees C) (P < 0.05). The percentage of relative humidity of the inspiration gas in patients in group B was also initially significantly low (69.8 +/- 4.1%; P < 0.05) but rose to an average of 98 +/- 2.8% after 2 h. The average percentage across all four groups amounted to 98 +/- 0.4% after 2 h. Inflammation of the tracheal mucosa was found in patients in group B and the mucosal injury score (MIS) was significantly higher than in all the other groups. Patients in groups A, C and D showed no severe evidence of airway damage, exhibiting adequate values of relative humidity and temperature of the inspired gas. CONCLUSION: The problems of humidification associated with jet ventilation can be fully prevented by using this new jet-ventilator. These data were sustained by nondeteriorating MIS values at the end of the 4-day study period in groups A, C and D.

Journal Article↗

PubMed2005

Pneumothorax and mortality in the mechanically ventilated SARS patients: a prospective clinical study.

INTRODUCTION: Pneumothorax often complicates the management of mechanically ventilated severe acute respiratory syndrome (SARS) patients in the isolation intensive care unit (ICU). We sought to determine whether pneumothoraces are induced by high ventilatory pressure or volume and if they are associated with mortality in mechanically ventilated SARS patients. METHODS: We conducted a prospective, clinical study. Forty-one mechanically ventilated SARS patients were included in our study. All SARS patients were sedated and received mechanical ventilation in the isolation ICU. RESULTS: The mechanically ventilated SARS patients were divided into two groups either with or without pneumothorax. Their demographic data, clinical characteristics, ventilatory variables such as positive end-expiratory pressure, peak inspiratory pressure, mean airway pressure, tidal volume, tidal volume per kilogram, respiratory rate and minute ventilation and the accumulated mortality rate at 30 days after mechanical ventilation were analyzed. There were no statistically significant differences in the pressures and volumes between the two groups, and the mortality was also similar between the groups. However, patients developing pneumothorax during mechanical ventilation frequently expressed higher respiratory rates on admission, and a lower PaO2/FiO2 ratio and higher PaCO2 level during hospitalization compared with those without pneumothorax. CONCLUSION: In our study, the SARS patients who suffered pneumothorax presented as more tachypnic on admission, and more pronounced hypoxemic and hypercapnic during hospitalization. These variables signaled a deterioration in respiratory function and could be indicators of developing pneumothorax during mechanical ventilation in the SARS patients. Meanwhile, meticulous respiratory therapy and monitoring were mandatory in these patients.

Aged↗

PubMed2006

Mechanical ventilation interacts with endotoxemia to induce extrapulmonary organ dysfunction.

INTRODUCTION: Multiple organ dysfunction syndrome (MODS) is a common complication of sepsis in mechanically ventilated patients with acute respiratory distress syndrome, but the links between mechanical ventilation and MODS are unclear. Our goal was to determine whether a minimally injurious mechanical ventilation strategy synergizes with low-dose endotoxemia to induce the activation of pro-inflammatory pathways in the lungs and in the systemic circulation, resulting in distal organ dysfunction and/or injury. METHODS: We administered intraperitoneal Escherichia coli lipopolysaccharide (LPS; 1 microg/g) to C57BL/6 mice, and 14 hours later subjected the mice to 6 hours of mechanical ventilation with tidal volumes of 10 ml/kg (LPS + MV). Comparison groups received ventilation but no LPS (MV), LPS but no ventilation (LPS), or neither LPS nor ventilation (phosphate-buffered saline; PBS). RESULTS: Myeloperoxidase activity and the concentrations of the chemokines macrophage inflammatory protein-2 (MIP-2) and KC were significantly increased in the lungs of mice in the LPS + MV group, in comparison with mice in the PBS group. Interestingly, permeability changes across the alveolar epithelium and histological changes suggestive of lung injury were minimal in mice in the LPS + MV group. However, despite the minimal lung injury, the combination of mechanical ventilation and LPS resulted in chemical and histological evidence of liver and kidney injury, and this was associated with increases in the plasma concentrations of KC, MIP-2, IL-6, and TNF-alpha. CONCLUSION: Non-injurious mechanical ventilation strategies interact with endotoxemia in mice to enhance pro-inflammatory mechanisms in the lungs and promote extra-pulmonary end-organ injury, even in the absence of demonstrable acute lung injury.

Animals↗

PubMed2000

Dynamics of breathing during partial liquid ventilation in spontaneously breathing rabbits supported by elastic and resistive unloading.

Partial liquid ventilation (PLV) has been shown to improve gas exchange in paralyzed animals and in humans with lung disease. This study tests the hypothesis that PLV combined with respiratory mechanical unloading results in stable ventilation and gas exchange in spontaneously breathing animals. Ten adult anesthetized, intubated, and spontaneously breathing rabbits received ventilatory support by respiratory mechanical unloading (Fi(O2) 1.0). Minute ventilation, respiratory rate, esophageal pressure, heart rate, and arterial blood pressure were recorded continuously during gas ventilation for 1 h. Next, 30 mL/kg of perfluorocarbon was instilled into the endotracheal tube. Thereafter, data were recorded again for 1 h (PLV). Arterial blood gases were obtained at the end of each period. Variability of recorded data was assessed by calculating coefficients of variation using data obtained each minute. Compared with gas ventilation, minute ventilation was larger during PLV (275 +/- 93 versus 368 +/- 89 mL/kg/min.; p < 0.01). This was because of a higher respiratory rate during PLV (58 +/- 23 versus 74 +/- 18 breaths/min; p < 0.05), while tidal volume was similar. Compared with gas ventilation, Pa(O2) was lower during PLV (61.31 +/- 5.32 versus 47.35 +/- 8.38 kPa; p < 0.05). Pa(CO2), peak esophageal pressure deflections, heart rate, mean arterial blood pressure, and coefficients of variation for minute ventilation, tidal volume, respiratory rate, and peak esophageal pressure were not significantly different between modes. Compliance was decreased and resistance and work of breathing were increased during PLV. We conclude that stable ventilation and gas exchange may be achieved during PLV combined with mechanical unloading in spontaneously breathing animals without lung disease.

Animals↗

PubMed2004

Mechanical ventilation effect on surfactant content, function, and lung compliance in the newborn rat.

Studies of ventilator-associated lung injury in adult experimental animal models have documented that high tidal volume (TV) results in lung injury characterized by impaired compliance and dysfunctional surfactant. Yet, there is evidence that, in neonates, ventilation with a higher than physiologic TV leads to improved lung compliance. The purpose of our study was to evaluate how lung compliance and surfactant was altered by high TV ventilation in the neonate. We utilized a new model (mechanically air-ventilated newborn rats, 4-8 d old), and used 40 or 10 mL/kg TV strategies. Age-matched nonventilated animals served as controls. In all animals, dynamic compliance progressively increased after initiation of mechanical ventilation and was significantly greater than basal values after 60 min (p < 0.01). Lung lavage total surfactant with both TV strategies (p < 0.05) and the large aggregate fraction (only in TV = 40 mL/kg; p < 0.01) were significantly increased by 60 min of mechanical ventilation, compared with control animals. Ventilation with 40 mL/kg TV for 60 min adversely affected the lung surfactant surface-tension lowering properties (p < 0.01). After 180 min of ventilation with 40 mL/kg TV, the lung total surfactant content and dynamic compliance values were no longer distinct from the nonventilated animals' values. We conclude that, in the newborn rat, mechanical ventilation with a higher than physiologic TV increases alveolar surfactant content and, over time, alters its biophysical properties, thus promoting an initial but transient improvement in lung compliance.

Animals↗

PubMed2003

An evaluation of the Laryngeal Tube during general anesthesia using mechanical ventilation.

UNLABELLED: The Laryngeal Tube is a new supraglottic ventilatory device for airway management. It has been developed to secure a patent airway during either spontaneous or mechanical ventilation. In this study, we sought to determine the effectiveness of the Laryngeal Tube for primary airway management during routine surgery with mechanical ventilation. One-hundred-seventy-five subjects classified as ASA physical status I and II, scheduled for elective surgery, were included in the study. After the induction of general anesthesia and insertion of a Size 4 Laryngeal Tube, measurements of oxygen saturation, end-tidal CO(2) and isoflurane concentration, and breath-by-breath spirometry data were obtained every 5 min throughout surgery. The lungs were ventilated with volume-controlled mechanical ventilation. The number of attempts taken to insert the Laryngeal Tube and the insertion time were recorded. In 96.6% of patients, it was possible to maintain oxygenation, ventilation, and respiratory mechanics by using mechanical ventilation throughout the surgical procedure. The results of this study suggest that the Laryngeal Tube is an effective and safe airway device for airway management in mechanically ventilated patients during elective surgery. IMPLICATIONS: In 96.6% of patients intubated with the Laryngeal Tube, it was possible to maintain oxygenation, ventilation, and respiratory mechanics during mechanical ventilation.

Adolescent↗

PubMed1995

Questioning paradigms: caste-specific ventilation in harvester ants, Messor pergandei and M. julianus (Hymenoptera: Formicidae)

Do developmental constraints in ant colonies limit gas exchange strategies to those displayed by female alates (presumptive queens)? In the xeric harvester ant genus Messor, we found that M. pergandei and M. julianus female alates ventilated highly discontinuously, as predicted, but M. julianus workers ventilated less discontinuously and M. pergandei workers (which occur in more xeric habitats) ventilated continuously. We present the salient characteristics of the discontinuous ventilation cycles of the species and the manner in which they are modulated by CO2 emission rates at a single temperature (24 °C). We demonstrate that, in M. julianus workers, open-spiracle phase CO2 emission rate only slightly exceeds overall CO2 emission rate, making discontinuous ventilation marginal, a state extrapolated in M. pergandei to continuous ventilation. However, workers are plainly capable of far greater rates of CO2 emission than when inactive at 24 °C, so the lack of discontinuous ventilation in M. pergandei under normoxic conditions is not likely to be imposed by physiological constraints and may, in fact, be a response to its xeric environment. We hypothesize  aside from phylogenetic effects  that discontinuous ventilation occurs primarily in insects that may experience hypoxic and hypercapnic conditions, such as ant queens during claustral colony foundation and perhaps workers within the nest environment; that discontinuous ventilation is not necessarily essential to reduce respiratory water loss; and that it will not necessarily occur in castes or species routinely exposed to xeric but normoxic conditions.

Journal Article↗

PubMed1997

Ontogeny of central chemoreception during fictive gill and lung ventilation in an in vitro brainstem preparation of Rana catesbeiana

An isolated brainstem preparation of the bullfrog tadpole, Rana catesbeiana, displays coordinated rhythmic bursting activities in cranial nerves V, VII and X in vitro. In decerebrate, spontaneously breathing tadpoles, we have previously shown that these bursts correspond to fluctuations in buccal and lung pressures and to bursts of activity in the buccal levator muscle H3a. This demonstrates that the rhythmic bursting activities recorded in vitro represent fictive gill and lung ventilation. To investigate the ontogeny of central respiratory chemoreception during the transition from gill to lung ventilation, we superfused the isolated brainstems of four larval stage groups with oxygenated artificial cerebrospinal fluid at various levels of PCO2. We measured shifts in the pattern of fictive respiratory output and the response to central hypercapnic stimulation throughout development. At normal PCO2 (2.3 kPa), stage 39 tadpoles displayed rhythmic neural bursts associated with gill ventilation, while stages 1014 and 1519 tadpoles produced oscillating bursting activity associated with both gill and lung respiration, and tadpoles at stages 2025 displayed neural activity predominantly associated with lung ventilation. In stage 39 tadpoles, variations in PCO2 of the superfusate (0.56.0 kPa) caused almost no change in fictive gill or lung ventilation. By contrast, stage 1014 tadpoles showed a significant hypercapnic response (P<0.05) in the amplitude and frequency of fictive gill ventilation, which was accompanied by a significant increase (P<0.05) in the burst amplitude and respiratory output of cranial nerve X over that occurring at all other stages. The amplitude and frequency of fictive gill ventilation in stages 1519 increased significantly (P<0.05) in response to pH reduction, but became insensitive to hypercapnia at stages 2025. The frequency of fictive lung ventilation was unresponsive to hypercapnia in stage 1014, increased significantly by stage 1519 (P<0.05) and became maximal (P<0.05) in stages 2025. Overall, we describe the ontological development of central respiratory chemoreceptors driving respiratory output in the larval amphibian, demonstrating transfer in central chemoreceptive influence from gill to lung regulation during metamorphic stages. In addition, we provide novel evidence for the stimulatory influence of central chemoreceptors on fictive gill ventilation in response to CO2.

Journal Article↗

PubMed1992

Physiologic evaluation of pressure support ventilation by nasal mask in patients with stable COPD.

We evaluated the physiologic effects of pressure support ventilation by nasal route (NPSV) in eight patients with severe stable COPD and chronic hypercapnia who were randomly submitted to 2-h sessions of NPSV both with a portable ventilator (Respironics BIPAP device) and with a standard ventilator (Bird 6400ST device) at an inspiratory airway pressure of 22 cm H2O. Two sessions with each ventilator were performed using an FIO2 of 0.21 in each patient on two consecutive days. One patient did not tolerate either form of ventilation. Comparison of spontaneous with BIPAP ventilation showed a significant improvement in pH, PaCO2, and PaO2. Ventilatory pattern assessed by a respiratory inductive plethysmograph showed a significant increase in minute ventilation (VE), VT, and Ttot. Integrated surface diaphragmatic EMG activity measured only during BIPAP device ventilation decreased from that measured during spontaneous breathing. Similar changes in blood gases and ventilatory pattern were observed during ventilation by the Bird 6400ST except for VT/Ti ratio, which significantly increased. Comparison of baseline with measurements performed 12 h after the whole cycle of treatment showed a significant increase in pH and VE and a decrease in PaCO2. We conclude that short-term NPSV may be useful in improving respiratory pattern and blood gases in stable COPD patients with chronic hypercapnia.

Humans↗

PubMed1994

Asthma requiring mechanical ventilation. A low morbidity approach.

STUDY OBJECTIVE: There is considerable uncertainty about the clinical features, respiratory physiology, and optimal management of patients with asthma requiring mechanical ventilation. Furthermore, the ventilatory and pharmacologic management of asthma requiring mechanical ventilation remain controversial. We hypothesized (1) that there are clinically identifiable and pathophysiologically different subgroups presenting with asthma requiring ventilation; (2) that lower dose steroid therapy (< 400 mg/d intravenous hydrocortisone) is adequate; (3) that permissive hypercapnia is safe; (4) that prolonged paralysis is generally unnecessary; and (5) that clinical outcome would be favorable in patients treated with this approach. DESIGN: Review of medical records and intensive care charts and statistical analysis of findings. SETTING: ICU of tertiary institution. PATIENTS: Thirty-five consecutive cases of life-threatening asthma requiring mechanic ventilation. RESULTS: Three clinical subgroups of ventilation-requiring asthmatics could be identified. Those presenting with steady deterioration (10), those with unstable asthma followed by a sudden "dip" (16), and those with a sudden unexpected dip (9). Patients in the first group had a significantly lower PaCO2 (p < 0.01) at presentation, but required ventilation for longer periods. Those in the second group had a significantly higher PaCO2 (p < 0.01) and required ventilation for a shorter period. Those in the third group had an intermediate PaCO2 level before intubation and the shortest period (p < 0.01) of mechanical ventilation. Five patients experienced their sudden dip after ingesting aspirin. Ten cases received "high" dose hydrocortisone therapy (mean: 980 mg/24 h), and 25 received lower dose hydrocortisone (mean: 341 mg/24 h). No differences in illness severity at presentation or outcome could be detected between these two groups. Mean duration of ventilatory support was 36 h and mean duration of the ICU stay 52.1 h. Muscle relaxation was used in 12 patients for a mean period of 11.1 h. One patient was brain dead on arrival. All others survived. CONCLUSIONS: Life threatening asthma is an endpoint for several different clinical patterns of disease. No major clinical advantage could be found in our group of patients when high-dose steroids were used. Long-term use of muscle relaxants and prolonged mechanic ventilation are rarely needed in the management of patients with life-threatening asthma and excellent results can be achieved with a relatively simple management strategy.

Adult↗

PubMed1994

Portable chest radiographs identify mechanical ventilator-associated hyperinflation.

OBJECTIVE: Portable chest radiographs (CRs) are obtained routinely in mechanically ventilated patients, but little is known about relationships between CR findings and ventilator parameters. It is unclear whether radiographically apparent hyperinflation correlates with tidal volume (VT), body weight (BW), VT/kg, or levels of peak airway pressure (PAP), positive end-expiratory pressure (PEEP), or pressure support (PS). DESIGN: Prospective comparison of CR and ventilator parameters in 62 mechanically ventilated patients in surgical and medical intensive care units of a university hospital. PATIENT SELECTION: All mechanically ventilated adults with portable CR on four separate dates. METHODS: Chest radiographs were classified by subjective assessments as hyperinflated (H+) or nonhyperinflated (H-), independent of knowledge of patients or their mechanical ventilation. Chest radiographs were reclassified independently as H+, H-, or indeterminate by a radiologist using objective criteria. Ventilator parameters recorded at the time of the CR were obtained and compared. RESULTS: Patients with CRs classified subjectively as H+ compared with patients with CRs classified as H- had a larger VT/kg (12.0 +/- 0.4 ml/kg [mean +/- SEM] vs 10.2 +/- 0.4; p = 0.004), lower BW (70.8 +/- 2.9 kg vs 81.5 +/- 3.8; p = 0.03), higher PEEP (6.5 +/- 0.5 cm H2O vs 5.0 +/- 0.4; p = 0.01), and higher PAP (38.2 +/- 2.1 cm H2O vs. 33.4 +/- 1.8; p = 0.06). Using objective CR classifications, patients with H+ CRs had a VT/kg of 12.6 +/- 0.4, larger than in the indeterminate (11.1 +/- 0.8) and H- (9.9 +/- 0.3) groups (p < 0.001). The BW differed among objectively classified groups (66.5 +/- 2.7 H+, 68.9 +/- 5.1 indeterminate, and 85.2 +/- 3.7 H-; p < 0.001), but other ventilator parameters did not correlate univariately with the degree of inflation on CR. Multivariate analysis showed that higher VT was predictive of H+ after adjusting for BW in subjective (p = 0.076) and objective (p = 0.017) classifications. PEEP (p = 0.004) and older age (p = 0.021) were also associated with H+ in multivariate analysis. Four of 25 (16 percent) patients with objectively H+ CRs developed barotrauma, while no patient with H- CR had this complication (p = 0.037). CONCLUSIONS: In mechanically ventilated patients, hyperinflation seen on portable CR is associated with higher VT, VT/kg, and lower BW, and may help predict subsequent barotrauma.

Adolescent↗

PubMed1994

The clinical management of dying patients receiving mechanical ventilation. A survey of physician practice.

OBJECTIVE: Despite mechanical ventilation's widespread use, there is scant literature to guide the management of patients receiving mechanical ventilatory assistance who are foregoing life-sustaining treatment. This survey was conducted to characterize physician treatment of such patients. DESIGN: Surveys were mailed to 513 randomly selected critical care physicians and returned by 308 (60 percent); 273 respondents were involved in ventilator management; all others were excluded. PARTICIPANTS: Forty percent of respondents were internists, 28 percent were surgeons, 16 percent were pediatricians, and 11 percent were anesthesiologists; 85 percent of physicians were board eligible/certified in a critical care subspecialty. RESULTS: Fifteen percent of respondents almost never withdrew ventilators from dying patients foregoing life-sustaining treatment; 37 percent did so less than half the time. Twenty-six percent of physicians believed there was a moral difference between withholding and withdrawing ventilators. Of physicians who withdrew ventilators, 33 percent preferred terminal weaning, 13 percent preferred extubation, and the remainder used both methods. Reasons for preferring extubation included the directness of the action (72 percent), family perceptions (34 percent), and patient comfort (34 percent). Reasons for preferring terminal weaning included patient comfort (65 percent), family perceptions (63 percent), and the belief that terminal weaning was less active (49 percent). Morphine and benzodiazepines were used frequently by 74 percent (morphine) and 53 percent (benzodiazepines) of physicians when withdrawing ventilators; 6 percent used paralytics at least occasionally. CONCLUSIONS: There is significant variation in the care of dying patients receiving mechanical ventilatory assistance, with 15 percent of respondents almost never withdrawing ventilators from such patients. Two very different methods of ventilator withdrawal each have advocates, yet rationales of patient comfort and family perceptions are matters of individual experience, absent published studies. The occasional use of paralytics during ventilator withdrawal raises concern about current practice.

Analysis of Variance↗

PubMed2003

[Noninvasive ventilation in pediatrics].

OBJECTIVE: To introduce the notion of noninvasive mechanical ventilation as an alternative for invasive ventilation in children, describing advantages and disadvantages, indications, and the process of equipment installation. SOURCE OF DATA: Literature review through PubMed/Medline, using as source articles focusing on noninvasive ventilation in pediatric populations, as well as consensus statements and metanalyses concerning noninvasive ventilation in adults. SUMMARY OF THE FINDINGS: The main indication for noninvasive ventilation is respiratory failure due to hypercapnia. It is contra-indicated in the presence of hemodynamic instability. The advantages of noninvasive ventilation include: the equipment is easy to install; it is not invasive and involves less discomfort; there is a lower incidence of complications associated with the endotracheal tube; lower cost. The disadvantages are: gastric distention; transient hypoxemia; facial skin necrosis. The equipment required for noninvasive ventilation includes an interface (mask) and a respirator. The removal of noninvasive ventilation equipment is relatively simple, but chronic patients may require assistance in the home. CONCLUSIONS: Noninvasive ventilation is a less costly, efficient and simple to perform alternative in cases of respiratory failure without hemodynamic instability.

Child↗

PubMed2003

Effect of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity.

OBJECTIVE: To evaluate effects of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity. ANIMALS: 8 clinically normal adult Walker Hound dogs. PROCEDURE: Each dog was anesthetized and subjected to one-lung ventilation during a period when it had an open thoracic cavity. A Swan-Ganz catheter was used to measure hemodynamic variables and obtain mixed-venous blood samples. A catheter was inserted in the dorsal pedal artery to measure arterial pressure and obtain arterial blood samples. Oxygen delivery index was calculated and used to assess effects of one-lung ventilation on cardiopulmonary function. Effects on hemodynamic and pulmonary variables were analyzed. RESULTS: One-lung ventilation caused significant decreases in PaO2, arterial oxygen saturation (SaO2), mixed-venous oxygen saturation, and arterial oxygen content (CaO2). One-lung ventilation caused significant increases in PaCO2, physiologic dead space, and alveolar-arterial oxygen difference. Changes in SaO2, CaO2, and PaCO2, although significantly different, were not considered to be of clinical importance. One-lung ventilation induced a significant increase in pulmonary arterial wedge pressure, mean pulmonary artery pressure, and shunt fraction. One-lung ventilation did not have a significant effect on cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, and oxygen delivery index. CONCLUSIONS AND CLINICAL RELEVANCE: One-lung ventilation affected gas exchange and hemodynamic function, although oxygen delivery in clinically normal dogs was not affected during a period with an open thoracic cavity. One-lung ventilation can be used safely in healthy dogs with an open thoracic cavity during surgery.

Anesthesia, Inhalation↗

PubMed1995

Continuous aspiration of subglottic secretions in preventing ventilator-associated pneumonia.

OBJECTIVE: To determine whether continuous subglottic aspiration prevents nosocomial pneumonia in mechanically ventilated patients. DESIGN: A randomized, controlled, blinded study. SETTING: Medical-surgical intensive care unit. PATIENTS: 190 patients who were admitted to the intensive care unit during a 33-month period and whose condition suggested the need for prolonged intubation (> 3 days). INTERVENTION: 76 patients were randomly allocated to receive continuous aspiration of subglottic secretions, and 77 control patients were allocated to receive usual care. MEASUREMENTS: The numbers of cases of ventilator-associated pneumonia, ventilated days, days in intensive care unit, and deaths were recorded. The amount of subglottic secretions aspirated daily and surveillance cultures in the subglottic secretions were also obtained periodically. Etiologic diagnosis was based on the quantitative culture of secretions obtained by protected specimen brush or bronchoalveolar lavage. RESULTS: The incidence rate of ventilator-associated pneumonia was 19.9 episodes/1000 ventilator days in the patients receiving continuous aspiration of subglottic secretions and 39.6 episodes/1000 ventilator days in the control patients (relative risk, 1.98; 95% CI, 1.03 to 3.82). This difference was due to a significant (P < 0.03) reduction in the number of gram-positive cocci and Haemophilus influenzae organisms in the patients receiving continuous aspiration. However, no differences were observed in the number of Pseudomonas aeruginosa or Enterobacteriaceae organisms. Episodes of ventilator-associated pneumonia occurred later in patients receiving continuous aspiration (12.0 +/- 7.1 days) than in the control patients (5.9 +/- 2.1 days) (P = 0.003). The same microorganisms isolated from protected specimen brush or bronchoalveolar lavage cultures in patients with ventilator-associated pneumonia were previously isolated from cultures of subglottic secretions in 85% of cases. No significant differences in outcome were found. CONCLUSIONS: The incidence of nosocomial pneumonia in mechanically ventilated patients can be significantly reduced by using a simple method that decreases the chronic microaspirations through the cuff of endotracheal tubes.

Aged↗

PubMed1994

A re-evaluation of the ventilator score as an indicator of prognosis in the adult respiratory distress syndrome.

OBJECTIVE: To determine whether the ventilator score of Smith and Gordon (1986) can accurately predict outcome in patients with severe Adult Respiratory Distress Syndrome (ARDS). DESIGN: Retrospective study of data from case records and flow sheets. SETTING: University Hospital Intensive Care Unit. SUBJECTS: Fifty-five patients with severe Adult Respiratory Distress Syndrome. MEASUREMENTS AND MAIN RESULTS: The ventilator score of Smith and Gordon (1986), based on a compound score of the patient's age, alveolar to arterial oxygen tension difference and mean peak airway pressure, was calculated daily for for each patient. In contrast to the original report, a high ventilator score ( greater than 80) had a predictive value for death of only 59%, and a specificity of only 29%. The use of a higher ventilator score ( greater than 100) resulted in a predictive value of only 70% with a specificity of 75%. The use of inverse ratio ventilation was associated with a significant improvement in survival in those patients with ventilator scores greater than 100. This finding has not been reported previously. CONCLUSIONS: The ventilator score does not provide a satisfactory predictor of outcome in ARDS and cannot be used as a prognostic tool. It may have some use as an indicator of the severity of respiratory failure. A ventilator score greater than 100 may be an indication for the institution of inverse ratio ventilation.

Adolescent↗