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PubMed1994

Lung parenchyma and type II cell morphometrics: effect of surfactant treatment on preterm ventilated lamb lungs.

The effect of exogenous surfactant treatment on lung and type II cell structure of ventilated lambs of 137-138 days gestational age was studied. Thirty-four lambs were delivered and randomized to control or 100 mg/kg of natural sheep surfactant treatment groups. Lungs from one group of lambs not treated with surfactant were fixed before ventilation, and the other animals were ventilated to maintain normal blood gas values for 3, 24, or 48 h. Morphometric assessment of the inflation-fixed lung parenchyma of ventilated lungs was compared with the architectural appearance of alveoli and alveolar ducts in the unventilated lungs. Mechanical ventilation resulted in distension of alveolar ducts accompanied by the shallowing and loss of well-defined alveoli and areas of atelectasis at 3 h. These abnormalities increased in severity after 24 and 48 h of ventilation. Surfactant treatment before ventilation significantly reduced the extent and degree of dilatation and concomitant atelectasis. The fraction of normal parenchyma was 38 +/- 7% in untreated lambs vs. 64 +/- 6% in treated lambs after 24 h of ventilation. After 48 h of ventilation, significant differences between control (39 +/- 6%) and surfactant-treated (55 +/- 6%) lambs were still evident. Alveolar type II cells contained approximately 15% lamellar bodies by volume. Neither surfactant treatment nor time of ventilation altered the volume density of lamellar bodies or other organelles, except for a decrease in glycogen from 8% in nonventilated lungs to 2.5% in lungs ventilated for 24 h. These findings indicate that a surfactant treatment at birth results in the maintenance of more normal parenchyma with less atelectasis during prolonged ventilation of the immature lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Tidal ventilation at low airway pressures can augment lung injury.

Intermittent positive pressure ventilation with large tidal volumes and high peak airway pressures can result in pulmonary barotrauma. In the present study, we examined the hypothesis that ventilation at very low lung volumes can also worsen lung injury by repeated opening and closing of airway and alveolar duct units as ventilation occurs from below to above the infection point (Pinf) as determined from the inspiratory pressure-volume curve. We ventilated isolated, nonperfused, lavaged rat lungs with physiologic tidal volumes (5 to 6 ml/kg) at different end-expiratory pressures (above and below Pinf) and studied the effect on compliance and lung injury. In the groups ventilated with positive end-expiratory pressure (PEEP) below Pinf compliance fell dramatically after ventilation. It did not change in either the control group or the group ventilated with PEEP above Pinf. Lung injury assessed morphologically was significantly greater in the groups ventilated with a PEEP below Pinf, and in these groups the site of injury was dependent on the level of PEEP. The group ventilated without PEEP had significantly greater respiratory and membranous injury to bronchioles, while the group ventilated with PEEP of 4 cm H2O had significantly greater alveolar duct injury. In conclusion, ventilation at lung volumes below those found at Pinf caused a significant decrease in lung compliance and progression of lung injury. Therefore, in addition to high airway pressures, end-expiratory lung volume is an important determinant of the degree and site of lung injury during positive-pressure ventilation.

Animals↗
PubMed2002

Variable tidal volume ventilation improves lung mechanics and gas exchange in a rodent model of acute lung injury.

Random variations in breath rate and tidal volume during mechanical ventilation in the setting of acute lung injury have been shown to improve arterial oxygen tension. To test whether this improvement occurs over a specific range of variability, we examined several ventilation protocols in guinea pigs with endotoxin-induced lung injury. In Group I (n = 10), after 30 min of conventional volume-cycled ventilation, animals were ventilated with variable ventilation for 30-min intervals, during which time tidal volume was randomly varied by 10, 20, 40, and 60% of the mean, while simultaneously adjusting the frequency to maintain constant minute ventilation. In a second group of animals (Group II, n = 4), conventional volume-cycled ventilation was administered for 3 h. Variable ventilation significantly improved lung function over conventional volume-cycled ventilation. In Group I, lung elastance decreased, and blood oxygenation increased significantly during periods of 40 and 60% variable ventilation (p < 0.05) compared with conventional ventilation. These data indicate that variable ventilation is effective in improving lung function and gas exchange during acute lung injury.

Animals↗
PubMed1986

Jet ventilation at 100 breaths per minute in adult respiratory failure.

To compare the ventilation and oxygenation capabilities of jet ventilation at 100 breaths per minute with those of conventional mechanical ventilation (CMV) in adults with respiratory failure, we performed a 2- to 3-h cross-over trial of jet ventilation in 65 stable patients requiring mechanical ventilation. Jet ventilation was delivered with an inspiratory time of 0.2 s through a 1.62-mm injector cannula attached to the proximal endotracheal tube. Drive pressure was adjusted to approximate the arterial PaCO2 on CMV. Measurements of arterial blood gases, peak and mean airway pressures (Paw), blood pressure (BP), and heart rate (HR) were recorded during baseline CMV, after every 30-min period during jet ventilation, and again 30 min after returning the patient to CMV. For analysis, patients were divided into 4 clinical and radiographic patterns: diffuse parenchymal disease (n = 22), focal parenchymal disease (n = 18), obstructive airway disease (n = 6), and nonpulmonary disease (n = 19). Jet ventilation "failures" were characterized by significantly higher minute ventilation requirements, higher levels of PaCO2, higher airway pressures, and smaller PaO2/FIO2 ratios on CMV as compared to the 58 ventilatory "successes." In the ventilatory "successes," peak Paw was significantly lower, but mean Paw, PaCO2, PaO2, FIO2, BP, and HR were not significantly different with jet ventilation as compared to CMV. Moreover, in this ventilatory success group, patients with an increase in the PaO2/FIO2 during jet ventilation were not significantly different from patients with a decrease in PO2/FIO2 in terms of clinical characteristics, ventilation requirements, or gas exchange capabilities on CMV.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Mechanical versus manual ventilation via a face mask during the induction of anesthesia: a prospective, randomized, crossover study.

UNLABELLED: One approach to make ventilation safer in an unprotected airway has been to limit tidal volumes; another one might be to limit peak airway pressure, although it is unknown whether adequate tidal volumes can be delivered. Accordingly, the purpose of this study was to evaluate the quality of automatic pressure-controlled ventilation versus manual circle system face-mask ventilation regarding ventilatory variables in an unprotected airway. We studied 41 adults (ASA status I-II) in a prospective, randomized, crossover design with both devices during the induction of anesthesia. Respiratory variables were measured with a pulmonary monitor (CP-100). Pressure-controlled mask ventilation versus circle system ventilation resulted in lower (mean +/- SD) peak airway pressures (10.6 +/- 1.5 cm H(2)O versus 14.4 +/- 2.4 cm H(2)O; P < 0.001), delta airway pressures (8.5 +/- 1.5 cm H(2)O versus 11.9 +/- 2.3 cm H(2)O; P < 0.001), expiratory tidal volume (650 +/- 100 mL versus 680 +/- 100 mL; P = 0.001), minute ventilation (10.4 +/- 1.8 L/min versus 11.6 +/- 1.8 L/min; P < 0.001), and peak inspiratory flow rates (0.81 +/- 0.06 L/s versus 1.06 +/- 0.26 L/s; P < 0.001) but higher inspiratory time fraction (48% +/- 0.8% versus 33% +/- 7.7%; P < 0.001) and end-tidal carbon dioxide (34 +/- 3 mm Hg versus 33 +/- 4 mm Hg; not significant). We conclude that in this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during mask ventilation. IMPLICATIONS: In this model of apneic patients with an unprotected airway, pressure-controlled ventilation resulted in reduced inspiratory peak flow rates and lower peak airway pressures when compared with circle system ventilation, thus providing an additional patient safety effect during face-mask ventilation.

Adolescent↗
PubMed1986

Ventilation and partitioning of oxygen uptake in the frog Rana pipiens: effects of hypoxia and activity.

Pulmonary and cutaneous oxygen uptake (MO2) and lung ventilation were measured in frogs floating in water with access to air in respirometers, with and without ventilation of the skin provided by stirring. The frogs were exposed to hypoxia in both water and air, and were variably active. In inactive frogs floating in unstirred respirometers at 25 degrees C, 23% of total MO2 is through the skin. Activity of the animal increases total MO2. and also ventilates the skin, so that cutaneous MO2 increases with increasing total MO2. When the respirometer is stirred, cutaneous MO2 increases to 35% of total MO2 in resting animals. Activity no longer affects cutaneous MO2. Lung ventilation volume is directly proportional to lung ventilation rate in normoxia. Ventilation rate, and therefore ventilation volume, is proportional to pulmonary MO2. Ventilation rate approximately doubles in hypoxia (PO2 = 52 mmHg). The pattern of ventilation also changes in hypoxia, from a very irregular pattern in normoxia to one showing regular, large oscillations of lung volume over several ventilation movements. Increased lung ventilation, enhancing pulmonary MO2, is the primary adjustment to increased O2 demand. Partitioning of MO2 shifts towards the lung during both activity and hypoxia. In both cases, however, ventilation of the skin can supplement total MO2 by increasing absolute levels of cutaneous MO2.

Animals↗
PubMed1995

Dynamics of carbon dioxide elimination following ventilator resetting.

BACKGROUND: Carbon dioxide elimination (VCO2) at steady state corresponds to the metabolic rate. A change in tidal ventilation will lead to a transient response in VCO2 if other determinants of VCO2 are constant. This principle may be applied in the critical care unit to reset ventilators. OBJECTIVE: To define and characterize the transient response of VCO2 to a well-defined change in ventilation. METHODS: Forty-four patients in stable condition receiving volume-controlled mechanical ventilation had trend recordings of ventilator pressures, flow, volumes, VCO2, and end-tidal CO2 (ETCO2) for 20 min. At time t0, the minute ventilation was either increased (n = 22) or decreased (n = 22) by 10% after which these parameters were monitored over 30 min. Blood gas values were measured 5 and 20 min after the change in ventilation and the dead space fractions were computed using the single breath-CO2 test. DATA ANALYSIS: The first ten breaths (till t1) after a change in ventilation were excluded. The time constant (tau) of the relative change in VCO2 (delta VCO2) was calculated by fitting exponential regressions to delta VCO2 for periods up to 20 min after t1. RESULTS: The delta VCO2 at t1 was proportional to the relative change in tidal volume (delta VT). The proportionality decreased gradually during 20 min. The proportionality of the relative change in ETCO2 (delta ETCO2) or PaCO2 (delta PaCO2) with delta VT was minimal at t1 and increased during the 20 min. tau increased progressively when calculated over longer periods (p < 0.001). tau was similar in the groups with increased and decreased ventilation up to 5 min, after which it was longer in the group with decreased ventilation (p < 0.05). The delta PaCO2 after 20 min correlated best with delta VCO2 at t1 (r = -0.8) and with delta ETCO2 at the end of 20 min (r = 0.8). CONCLUSIONS: Noninvasively monitored VCO2 provides an instantaneous indication of the change in alveolar ventilation in well-sedated, mechanically ventilated patients in stable condition without significant cardiopulmonary disease.

Adult↗
PubMed1996

Predicting the duration of mechanical ventilation. The importance of disease and patient characteristics.

STUDY OBJECTIVE: To analyze the determinants of an individual patient's duration of mechanical ventilation and assess interhospital variations for average durations of ventilation. DESIGN: Prospective, multicenter, inception, cohort study. SETTING: Forty-two ICUs at 40 US hospitals. PATIENTS: A total of 5,915 patients undergoing mechanical ventilation on ICU day 1 selected from the acute physiology and chronic health evaluation (APACHE) III database of 17,440 admissions. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Utilizing APACHE III data collected on the 5,915 patients, multivariate regression analysis was performed on selected patients and disease characteristics to determine which variables were significantly associated with the duration of mechanical ventilation. An equation predicting duration of ventilation was then developed using the significant predictor variables and its accuracy was evaluated. Variables significantly associated with duration of ventilation included primary reason for ICU admission, day 1 acute physiology score (APS) of APACHE III, age, prior patient location and hospital length of stay, activity limits due to respiratory disease, serum albumin, respiratory rate, and PaO2/FIo2 measurements. Using an equation derived from these variables, predicted durations of ventilation were then calculated and compared with actual observed durations for each of the 42 ICUs. Average duration of ventilation for the 42 ICUs ranged from 2.6 to 7.9 days, but 60% of this variation was accounted for by differences in patient characteristics. CONCLUSIONS: For patients admitted to the ICU and ventilated on day 1, total duration of ventilation is primarily determined by admitting diagnosis and degree of physiologic derangement as measured by APS. An equation developed using multivariate regression techniques can accurately predict average duration of ventilation for groups of ICU patients, and we believe this equation will be useful for comparing ventilator practices between ICUs, controlling for patient differences in clinical trials of new therapies or weaning techniques, and as a quality improvement mechanism.

APACHE↗
PubMed2004

Congenital myotonic dystrophy: assisted ventilation duration and outcome.

OBJECTIVE: To clarify the relationship between initial assisted ventilation duration and outcome for patients with congenital myotonic dystrophy (CDM). METHODS: A retrospective chart review was conducted of cases of CDM that presented to the Children's Hospital of Eastern Ontario (Ottawa, Ontario, Canada) between 1980 and 2000. Inclusion criteria were conclusive testing for CDM and clinical presentation in the first 30 days of life. Duration of assisted ventilation, morbidity, mortality, and developmental outcome were measured. RESULTS: A total of 23 children met the inclusion criteria. One child died at 5 days of age, and 2 others had withdrawal of ventilation. The remaining 20 children were divided into 2 groups on the basis of whether they needed > or <30 days of ventilation. In the first year of life, 25% mortality was noted in the children with prolonged ventilation, whereas no child in the short ventilation duration group died. After 1 year of age, 1 child in each group died with follow-up of 2 to 16 years. The children with prolonged ventilation needed more hospitalizations. Delays were noted in development in both groups of children at ages 1, 3, and 6 years; however, there was an improvement in motor and language scores over time in all children. Children who required ventilation for <30 days had better motor, language, and activities of daily living scores at all ages. CONCLUSIONS: Children with CDM with prolonged ventilation experienced 25% mortality in the first year. The use of a specific time period of ventilation to decide on withdrawal of therapy must be reconsidered given these findings. Prolonged ventilation was followed by greater morbidity and developmental delay than children with shorter ventilation duration.

Activities of Daily Living↗
PubMed1999

Abstracts from the first symposium on the topic: liquid ventilation - 13th of march 1999, berlin

Basic research: Perfluorocarbons and the Pulmonary Surfactant System - Perfluorocarbons in the Treatment of Pneumonia - Inertance of the Respiratory System during Partial Liquid Ventilation - Alveolar Dead Space and Partial Liquid Ventilation - Partial Liquid Ventilation and Prevention of Cerebral Damage - New therapies of old problems: Efficacy of Partial Liquid Ventilation (PLV) Compared to Mechanical Ventilation with High Levels of PEEP in Experimental Acute Lung Injury - Application of Nitric Oxide during Partial Liquid Ventilation in Acute Respiratory Failure with Pulmonary Hypertension in Piglets - Preparation for clinical application: Partial Liquid Ventilation and Filling Condition with Perfluorocarbon - The Influence of Different Positive End-expiratory Pressure Levels on Partial Liquid Ventilation in Acute Lung Injury in Piglets - Partial Liquid Ventilation and Filling Condition with Perfluorocarbon - Spontaneous Respiratory Effort during Partial Liquid Ventilation (PLV) - Combination of Kinetic Therapy and Partial Liquid Ventilation in the Therapy of Acute Respiratory Failure in Piglets - Level of clinical studies: Do We Need Liquid Ventilation (LV) in Neonatology?

Journal Article↗
PubMed2003

Changes in respiratory and circulatory functions during sequential invasive-noninvasive mechanical ventilation.

OBJECTIVE: To investigate the changes in respiratory and circulatory functions in chronic obstructive pulmonary disease (COPD) patients during sequential invasive-noninvasive mechanical ventilation therapy, and evaluate the effects of this new technique. METHODS: Twelve COPD patients with type II respiratory failure due to severe pulmonary infection were ventilated through an endotracheal tube. When the pulmonary infection control window (PIC-Window) occurred, the patients were extubated and were ventilated with a facial mask using pressure support ventilation combined with positive end-expiratory pressure. The parameters of hemodynamics, oxygen dynamics, and esophageal pressure were measured at the PIC-Window during invasive mechanical ventilation, one hour after oxygen therapy via a naso-tube, and three hours after non-invasive mechanical ventilation. RESULTS: The variation in esophageal pressure was 20.0 +/- 6 cmH(2)O during naso-tube oxygen therapy, and this variation was higher than that during non-invasive mechanical ventilation (10 +/- 6 cmH(2)O, P < 0.01). The changes in respiratory and circulatory parameters were not significantly different between invasive mechanical ventilation and noninvasive mechanical ventilation (P > 0.05). CONCLUSIONS: The respiratory and circulatory functions of COPD patients remained stable during sequential invasive-noninvasive mechanical ventilation therapy using PIC-Window as a switch point for early extubation. The COPD patients can tolerated the transition from invasive mechanical ventilation to noninvasive mechanical ventilation.

Aged↗
PubMed2005

Prone versus supine position in mechanically ventilated children: a pilot study.

BACKGROUND: It is known that mechanically ventilated patients in the prone position have improved oxygenation compared with those supine. We did a prospective, randomized, controlled trial to evaluate the effect of prone position during mechanical ventilation, on survival in critically ill children. MATERIAL/METHODS: Forty-two children needing mechanical ventilation for various illnesses were randomized to receive initial ventilation for four hours prone or supine by drawing lots. Initial severity of illness and blood gases in all children were noted. In a crossover design, after the initial four hours the children were turned over and ventilated in the alternate posture for an hour. Oxygenation parameters and mean airway pressures were noted at one hour, four hours, and five hours. Mortality, duration of ventilation, and the above parameters were compared in the two groups. RESULTS: Initial PRISM scores were similar in the two groups. Mortality in the prone group was less than in the supine group. The odds ratio of mortality was 0.20 (95% CI 0.05-0.75). Duration of ventilation was similar in the two groups. The oxygenation index was significantly lower in the prone group at one, four, and five hours after onset of ventilation. CONCLUSIONS: Prone position in the first few hours of ventilation significantly improves gas exchange and oxygenation, reduces the mean airway pressures required to ventilate children, and may cause significant improvement in survival. Our study protocol allowed ventilator settings to be changed as needed during ventilation.

Child, Preschool↗
PubMed2006

The effects of apparatus dead space on P(aCO2) in patients receiving lung-protective ventilation.

BACKGROUND: Lung-protective ventilation using tidal volume (V(T)) of 4-6 mL/kg (predicted body weight) reduces mortality (compared with traditional V(T)) in patients with acute respiratory distress syndrome and acute lung injury. Standardized use of lower V(T) can result in respiratory acidosis and has raised new concerns about the appropriate configuration of the ventilator circuit, especially in regard to the dead space (V(D)) of the apparatus. We hypothesized that, with a patient receiving lung-protective ventilation, the removal of all apparatus dead space from the circuit would reduce P(aCO2) and allow a reduction in minute ventilation. METHODS: All the studied patients met the American-European consensus-conference criteria for acute respiratory distress syndrome/acute lung injury, were receiving a lung-protective ventilation strategy, were > 18 years of age, and were hemodynamically stable. We prospectively tested 3 different ventilator-circuit configurations, in random sequence, for 15 min each: (1) standard hygroscopic heat-and-moisture exchanger (HME) with 15-cm flexible tubing, (2) 15-cm flexible tubing only, (3) no HME or flexible tubing. V(T), respiratory rate, positive end-expiratory pressure, and fraction of inspired oxygen were maintained constant throughout the study, and exhaled CO2 was measured continuously. Physiologic dead space (V(D)/V(T)) was calculated using the Enghoff modification of the Bohr equation. RESULTS: Seven patients were studied. Removal of the HME from the circuit significantly decreased V(D)/V(T) (by approximately 6%) and P(aCO2) (by approximately 5 mm Hg). Removal of both the HME and flexible tubing from the circuit reduced V(D)/V(T) by an additional 5%, and P(aCO2) by an additional 6 mm Hg. With both circuit-configuration changes, minute ventilation fell from a mean of 11.51 L/min to 10.35 L/min, and pH increased from 7.30 to 7.38. Carbon-dioxide production did not change significantly. CONCLUSION: In patients receiving lower-V(T) ventilation, removing all the apparatus V(D) from the ventilator circuit reduces P(aCO2) and increases pH, at a lower minute ventilation. This information will help guide ventilator-circuit configuration for patients receiving lung-protective ventilation.

Adult↗
PubMed1994

Effect of ventilation on acid-base balance and oxygenation in low blood-flow states.

OBJECTIVES: To investigate how minute ventilation affects the partial pressure of end-tidal CO2 and arterial and mixed venous pH, PCO2, PO2, and the concentration of bicarbonate during low blood-flow states. We tested the null hypothesis that acid-base conditions during low rates of blood flow are not significantly different when minute ventilation is doubled or halved. DESIGN: Prospective, experimental, animal study. SETTING: University hospital laboratory. SUBJECTS: Domestic swine. INTERVENTIONS: We studied ten anesthetized and mechanically ventilated swine (weight, 43 to 102 kg) in a new model of controlled systemic and pulmonary blood flow in which each animal was maintained on ventricular assist devices. After electrical induction of ventricular fibrillation, ventricular assist device blood flow was decreased in steps. At each decrease, control minute ventilation, two times the control minute ventilation (hyperventilation), and one-half the control minute ventilation (hypoventilation) were administered; each ventilatory change was maintained for 6 mins. MEASUREMENTS AND MAIN RESULTS: Aortic, pulmonary arterial and central venous pressures, ventricular assist device blood flow, and end-tidal CO2 were recorded continuously. Acid-base conditions were studied at three different mean blood flow rates: 49%, 30%, and 12% of baseline prearrest cardiac index. Arterial pH and PaO2 and mixed venous pH varied directly (p < .003) with minute ventilation, while PaCO2 and mixed venous PCO2, and end-tidal CO2 varied inversely (p < .0001) with minute ventilation. Mixed venous PO2 was not significantly related to minute ventilation (p = .6). PaCO2 and arterial bicarbonate; mixed venous pH, mixed venous PO2, and mixed venous bicarbonate, and end-tidal CO2 varied directly (p < .001) with blood flow, while mixed venous PCO2 varied inversely with blood flow (p < .05). Arterial pH was not significantly related to blood flow (p = .3). When minute ventilation changed from hyperventilation to hypoventilation at a mean blood flow rate of 49%, mean arterial pH decreased 0.22 +/- 0.06 (p < .05), mean PaCO2 increased 28 +/- 6 torr (3.7 +/- 0.8 kPa) (p < .05), and mean PaO2 decreased 99 +/- 77 torr (13.2 +/- 10 kPa); mean mixed venous pH decreased 0.11 +/- 0.02, mean mixed venous PCO2 increased 16 +/- 2.2 torr (2.1 +/- 0.3 kPa) (p < .05), and mean mixed venous PO2 did not change; mean end-tidal CO2 increased 18 +/- 2 torr (2.4 +/- 0.3 kPa) (p < .05). The effect of changes in minute ventilation on blood gases and end-tidal CO2 was similar for mean blood flow rates of 30% and 12% of baseline cardiac index. CONCLUSIONS: During low rates of blood flow similar to those rates found in shock and cardiopulmonary resuscitation, alterations in minute ventilation significantly influenced end-tidal CO2 and both arterial and mixed venous pH and PCO2. These findings may have clinical importance in improving the treatment of shock and cardiac arrest.

Acid-Base Equilibrium↗
PubMed1995

[Outcome and cost of mechanical ventilation in patients with inoperable solid tumors and hematologic malignancies].

The application of mechanical ventilation can be life-saving in patients with acute respiratory failure, but is frequently ineffective in terminally ill patients. To analyze the outcome and cost of mechanical ventilation for patients with malignancies, we retrospectively reviewed 115 patients with inoperable solid tumors or hematologic malignancies who received mechanical ventilation. Eighty eight of these 115 patients (77%) died while on mechanical ventilation; 18 patients (16%) were weaned from mechanical ventilation but still died during their hospitalization. Six patients (5%) were discharged but survived less than 3 months and only three patients (3%) survived for more than 3 months after discharge. The total time of mechanical ventilation was 772 person-days, which represented 5.5% (772/13974) of the total mechanical ventilator use in our hospital in 1993. The total hospital cost from initiation of mechanical ventilation to discharge or death of these 115 patients was NT $11,238,022 (US $432,200) and daily hospital cost per person during mechanical ventilation was approximately NT $10,845 (US $420). The "daily cost of discharge survival" (defined as total hospitalization cost from the initiation of mechanical ventilation to discharge or death divided by total discharge person-days) for patients with inoperable solid tumors was NT $73,421 (US $2,820)/per person-day. We concluded that mechanical ventilation should not be routinely used in patients with inoperable solid tumors and hematologic malignancies. Physicians should explain the poor outcome to these patients and their families in advance and inquire about their willingness to forego mechanical ventilation.

Aged↗
PubMed2005

Patient-ventilator interaction: an overview.

During assisted mechanical ventilation, the total pressure applied to respiratory system is the sum of ventilator and muscle pressure. As a result, the respiratory system is under the influence of two pumps, the ventilator pump (ie, Paw), which is controlled by the physician's brain and the capabilities of the ventilator, and the patient's own respiratory muscle pump (Pmus), which is controlled by the patient's brain. The patient-ventilator interaction is mainly an expression of the function of these two brains, which should be in harmony to promote patient-ventilator synchrony. The achievement of this harmony depends exclusively on the physician, who should be aware that during assisted mechanical ventilation the respiratory system is not a passive structure but reacts to pressure delivered by the ventilator via various feedback systems and, depending on several factors both to the ventilator and patient, may modify the function of the ventilator. Finally, the physician should know that the ventilator imposes significant constraints to the respiratory system, the magnitude of which depends heavily on the triggering variable, the variable that controls the gas delivery and the cycling off criterion.

Humans↗
PubMed2003

The sy-fi study: a randomized prospective trial of synchronized intermittent mandatory ventilation versus a high-frequency flow interrupter in infants less than 1000 g.

OBJECTIVE: Mechanical ventilation has significantly decreased mortality for preterm infants with respiratory distress syndrome. However, the barotrauma associated with mechanical ventilation is responsible for the development of bronchopulmonary dysplasia (BPD) in 20% to 90% of these infants, depending on gestational age. Recent studies suggest that high-frequency ventilation is associated with better gas exchange and less barotrauma. The purpose of this study is to determine if high-frequency ventilation, using the flow interrupter, reduces the incidence of BPD in the ELBW infant. STUDY DESIGN: Parental consent was obtained prior to mechanical ventilation. Infants less than 1000 g without significant congenital anomalies were eligible for study entry. Infants were randomized, prior to the onset of mechanical ventilation, to receive either synchronized intermittent mandatory ventilation (SIMV) or high-frequency flow interruption. Both ventilator methods were obtained using the Infant Star Ventilator (Mallinckrodt, St. Louis, MO). Data were collected prospectively on all study entrants and analyzed using SigmaStat Software. RESULTS: Forty-six infants, from two centers, were enrolled in this study. There was no significant difference in the ventilator days or BPD, defined as oxygen requirement at 36 weeks postmenstrual age, between the high-frequency ventilation and SIMV groups.

Bronchopulmonary Dysplasia↗
PubMed2001

Patient-ventilator asynchrony.

The basic mechanism of patient-ventilator asynchrony is the mismatching between neural inspiratory and mechanical inspiratory time. Alterations in respiratory drive, timing, respiratory muscle pressure, and respiratory system mechanics influence the interaction between the patient and the ventilator. None of the currently available partial ventilatory support modes are exempt from problems with patient-ventilator asynchrony. Ventilator triggering design in the trigger phase and the set variables in the post-trigger phase contribute to patient-ventilator interaction. The set inspiratory flow rate in the post-trigger phase for assist-control volume cycled ventilation affects patient-ventilator asynchrony. Likewise, the initial pressure rise time, the pressure support level, and the flow-threshold for cycling off inspiration for pressure support ventilation are important factors affecting patient-ventilator asynchrony. Current investigations have advanced our understanding in this area; however, its prevalence and the extent to which patient-ventilator asynchrony affect the duration of mechanical ventilation remain unclear.

Humans↗