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PubMed1998

Evaluation of a ventilation strategy to prevent barotrauma in patients at high risk for acute respiratory distress syndrome. Pressure- and Volume-Limited Ventilation Strategy Group.

BACKGROUND: A strategy of mechanical ventilation that limits airway pressure and tidal volume while permitting hypercapnia has been recommended for patients with the acute respiratory distress syndrome. The goal is to reduce lung injury due to overdistention. However, the efficacy of this approach has not been established. METHODS: Within 24 hours of intubation, patients at high risk for the acute respiratory distress syndrome were randomly assigned to either pressure- and volume-limited ventilation (limited-ventilation group), with the peak inspiratory pressure maintained at 30 cm of water or less and the tidal volume at 8 ml per kilogram of body weight or less, or to conventional ventilation (control group), with the peak inspiratory pressure allowed to rise as high as 50 cm of water and the tidal volume at 10 to 15 ml per kilogram. All other ventilatory variables were similar in the two groups. RESULTS: A total of 120 patients with similar clinical features underwent randomization (60 in each group). The patients in the limited-ventilation and control groups were exposed to different mean (+/-SD) tidal volumes (7.2+/-0.8 vs. 10.8+/-1.0 ml per kilogram, respectively; P<0.001) and peak inspiratory pressures (23.6+/-5.8 vs. 34.0+/-11.0 cm of water, P<0.001). Mortality was 50 percent in the limited-ventilation group and 47 percent in the control group (relative risk, 1.07; 95 percent confidence interval, 0.72 to 1.57; P=0.72). In the limited-ventilation group, permissive hypercapnia (arterial carbon dioxide tension, >50 mm Hg) was more common (52 percent vs. 28 percent, P=0.009), more marked (54.4+/-18.8 vs. 45.7+/-9.8 mm Hg, P=0.002), and more prolonged (146+/-265 vs. 25+/-22 hours, P=0.017) than in the control group. The incidence of barotrauma, the highest multiple-organ-dysfunction score, and the number of episodes of organ failure were similar in the two groups; however, the numbers of patients who required paralytic agents (23 vs. 13, P=0.05) and dialysis for renal failure (13 vs. 5, P= 0.04) were greater in the limited-ventilation group than in the control group. CONCLUSIONS: In patients at high risk for the acute respiratory distress syndrome, a strategy of mechanical ventilation that limits peak inspiratory pressure and tidal volume does not appear to reduce mortality and may increase morbidity.

Barotrauma↗
PubMed2000

Hemodynamic effects of synchronized high-frequency jet ventilation compared with low-frequency intermittent positive-pressure ventilation after myocardial revascularization.

BACKGROUND: The purpose of this prospective study was to examine the effect on cardiac performance of selective increases in airway pressure at specific points of the cardiac cycle using synchronized high-frequency jet ventilation (sync-HFJV) delivered concomitantly with each single heart beat compared with controlled mechanical ventilation in 20 hemodynamically stable, deeply sedated patients immediately after coronary artery bypass graft. METHODS: Five 30-min sequential ventilation periods were used interspersing controlled mechanical ventilation with sync-HFJV twice to control for time and sequencing effects. Sync-HFJV was applied using a driving pressure, which generated a tidal volume resulting in gas exchanges close to those obtained on controlled mechanical ventilation and associated with the maximal mixed venous oxygen saturation. Hemodynamic variables including cardiac output, mixed venous oxygen saturation and vascular pressures were recorded at the end of each ventilation period. RESULTS: The authors found that in 20 patients, hemodynamic changes induced by controlled mechanical ventilation and by sync-HFJV were similar. Cardiac index did not change (mean +/- SD for controlled mechanical ventilation: 2.6 +/- 0.7 l x min(-1) x m(-2); for sync-HFJV: 2.7 +/- 0.7 l x min(-1) x m(-2); P value not significant). This observation persisted after stratification according to baseline left-ventricular contractility, as estimated by ejection fraction. CONCLUSIONS: The authors conclude that after coronary artery bypass graft, if gas-exchange values are maintained within normal range, sync-HFJV does not result in more favorable hemodynamic support than controlled mechanical ventilation. These findings contrast with the beneficial effects of sync-HFJV, resulting in marked hypocapnia, on cardiac performance observed in patients with terminal left-ventricular failure.

Adult↗
PubMed2006

Pressure-controlled ventilation is superior to volume-controlled ventilation with a laryngeal mask airway in children.

BACKGROUND: This prospective, randomized, crossover study had two purposes: first, to determine whether pressure-controlled ventilation (PCV) is safer than volume-controlled ventilation (VCV) by preventing gastric insufflation in children ventilated through an laryngeal mask airway (LMA); second, to assess whether the measurement of LMA leak pressure (P(leak)) is useful for preventing leakage during positive pressure ventilation (PPV). METHODS: Forty-one, 2 to 15-year-old children underwent general anesthesia with an LMA. The expiratory valve was set at 30 cmH(2)O and P(leak) was measured using constant gas flow. Children were randomly ventilated using PCV or VCV for 5 min in order to reach a P(ET)CO(2) not exceeding 45 mm Hg, and then they were ventilated with the alternative mode. If the target P(ET)CO(2) could not be obtained in one mode, we switched to the other. If both modes failed, children were intubated. Tidal volumes, P(ET)CO(2) and airway pressures were noted and compared between modes. Gastric insufflation was checked by epigastric auscultation. RESULTS: PCV provided more efficient ventilation than VCV, as targeted P(ET)CO(2) was obtained without gastric insufflation using PCV in all cases except one, whereas VCV failed in three cases. No gastric insufflation occurred when ventilating below peak. CONCLUSIONS: These findings suggest that in the age group studied, PCV is more efficient than VCV for controlled ventilation with a laryngeal mask. Gastric insufflation did not occur with this mode.

Adolescent↗
PubMed2004

Ventilation efficiencies and thermal comfort results of a desk-edge-mounted task ventilation system.

UNLABELLED: In chamber experiments, we investigated the ventilation effectiveness and thermal comfort of a task ventilation system with an air supply nozzle located underneath the front edge of a desk and directing air towards a heated mannequin or a human volunteer seated at the desk. The task ventilation system provided outside air, while another ventilation system provided additional space cooling but no outside air. Test variables included the vertical angle of air supply (-15 degrees to 45 degrees from horizontal), and the supply flow rate of (3.5-6.5 l/s). Using the tracer gas step-up and step-down procedures, the measured air change effectiveness (i.e., exhaust air age divided by age of air in the breathing zone) in experiments with the mannequin ranged from 1.4 to 2.7 (median, 1.8), whereas with human subjects the air change effectiveness ranged from 1.3 to 2.3 (median, 1.6). The majority of the air change effectiveness values with the human subjects were less than values with the mannequin using comparable tests. Similarly, the tests run with supply air temperature equal to the room air temperature had lower air change effectiveness values than comparable tests with the supply air temperature lower ( approximately 5 degrees C) than the room air temperature. The air change effectiveness values are higher than typically reported for commercially-available task ventilation or displacement ventilation systems. Based on surveys completed by the subjects, operation of the task ventilation system did not cause thermal discomfort. PRACTICAL IMPLICATIONS: With a desk-edge-mounted task ventilation system it is possible to obtain an increase in the effective ventilation rate of 50%. This could lead to reduced energy use. Also, this improvement can be gained while maintaining thermal comfort for occupants. Thus occupants can be thermally comfortable and save energy at the same time.

Air Movements↗
PubMed2004

How safe is intermittent positive pressure ventilation in preterm babies ventilated from delivery to newborn intensive care unit?

OBJECTIVES: To examine whether clinically determined ventilator settings will produce acceptable arterial blood gas values on arrival, in preterm infants ventilated from delivery to the newborn intensive care unit (NICU). Further, to examine the usefulness of tidal volume and minute ventilation measurements at this time. DESIGN: A prospective observational cohort study in a tertiary level 3 NICU. PATIENTS: Twenty six preterm infants requiring intubation and mechanical ventilation at the point of delivery to the NICU. SETTING: Infants who required mechanical ventilation were monitored with a blinded Ventrak 1550 dynamic lung function monitor from the point of delivery to the NICU. A Dräger Babylog 2000 transport ventilator was set up to achieve adequate chest wall movement, and FIO(2) was adjusted to achieve preductal SaO(2) of 90-98%. Dynamic lung function monitoring data were recorded and related to the arterial blood gas taken on arrival. RESULTS: Mean gestation was 28 weeks (range 23-34) and mean birth weight was 1180 g (range 480-4200). A quarter (26% (95% confidence interval (CI) 12% to 48%)) were hypocarbic, with 20% (95% CI 7% to 39%) below 25 mm Hg, and 38% (95% CI 20% to 60%) had hyperoxia. Some (20% (95% CI 7% to 39%)) were both hypocarbic and hyperoxic. Total minute ventilation per kilogram correlated significantly with the inverse of PaCO(2) (p < 0.001). CONCLUSIONS: Clinically determining appropriate mechanical ventilation settings from the point of delivery to the NICU is difficult, and inadvertent overventilation may be common. Severe hyperoxia can occur in spite of adjustment of the FIO(2) concentration to achieve an SaO(2) range of 90-98%. Limiting minute ventilation during resuscitation may prevent hypocarbia.

Birth Weight↗
PubMed1997

Secondary failure of nasal intermittent positive pressure ventilation using the Monnal D: effects of changing ventilator.

BACKGROUND: Some patients started on nasal intermittent positive pressure ventilation (NIPPV) with the Monnal D ventilator deteriorate after a period. The effects of changing them to the Nippy ventilator were investigated. METHODS: The records of such patients were examined retrospectively. Comparisons were made between blood gas tensions and overnight oximetry records before NIPPV, 12 weeks after the initiation of NIPPV with the Monnal D, at the time of deterioration, and 12 weeks after initiation of treatment with the Nippy ventilator. RESULTS: Ten patients (seven women) were identified. Prior to starting NIPPV their mean (SD) age was 59.6 (8.39) years and their mean arterial oxygen and carbon dioxide tensions (PaO2 and PaCO2) while breathing air were 6.1 (1.79) and 9.6 (3.28) kPa, respectively. All were started on NIPPV with the Monnal D with improvements in symptoms, PaO2, PaCO2, and overnight oximetry after 12 weeks of treatment. After a mean interval of 118 (69.0) weeks all measures of ventilation had deteriorated and the patients were converted to the Nippy ventilator. Twelve weeks after initiation of treatment with the Nippy ventilator symptoms and overnight oximetry were improved again and the mean PaO2 and PaCO2 were 8.9 (1.27) and 6.9 (0.45) kPa, respectively. After a total mean period of 59 (26.9) weeks on the Nippy all but one of the patients have maintained this improvement. CONCLUSIONS: Support with NIPPV using the Monnal D ventilator may fail after an interval and changing to the Nippy ventilator can reverse this deterioration, probably because of its superior responsiveness to leaks and patient effort. The regular follow up of patients on long term NIPPV is necessary if secondary treatment failure is to be identified and effectively treated.

Aged↗
PubMed1997

Patient-ventilator interaction and inspiratory effort during pressure support ventilation in patients with different pathologies.

The aim of this study was to evaluate whether pressure support ventilation (PSV) requires different diaphragmatic efforts and patient-ventilator matching, according to the underlying disease. Four groups of patients requiring PSV were studied: Group A, recovering from an episode of acute respiratory failure due to adult respiratory distress syndrome (ARDS); Group B, with postsurgical complications; and two subsets of chronic obstructive pulmonary disease (COPD) patients, with "normal" static compliance of the respiratory system (Cst,rs) (Group C) or elevated Cst,rs (Group D). Ventilatory pattern, transdiaphragmatic pressure (Pdi), the pressure-time product of the diaphragm (PTPdi), static (PEEPi,stat) and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn), Cst,rs and resistance of the total respiratory system (Rrs) were recorded. The matching between patient and ventilator was analysed, recording the number of "ineffective efforts" (inspiratory efforts not efficient enough to trigger a new ventilator cycle, despite a positive deflection in Pdi). A satisfactory blood gas equilibrium arterial oxygen saturation (Sa,O2 > 93%, with a pH > 7.32) was obtained in the various groups with different levels of PSV. Minute ventilation was found to be significantly higher in Groups A and B, due to the longer expiratory time (tE) in the COPD groups. Group A (2 out of 7), Group B (3 out of 7), Group C (3 out of 5) patients showed sporadic "ineffective efforts". All Group D patients manifested continuous mismatching with the ventilator, so that the pressure-time product of the diaphragm per minute (PTPdi/min), reflecting the metabolic work of the diaphragm, was not different in the four groups. Tidal volume and the spontaneous inspiratory efforts were similar in the four groups, but the number of breaths delivered by the ventilator was significantly higher in Groups A and B. The application of different levels of pressure support ventilation in patients with acute respiratory failure due to different pathologies, led them to breathe with comparable pressure time product of the diaphragm. The majority of the patients showed mismatching with the ventilator, although this effect was more pronounced in the groups with chronic obstructive pulmonary disease.

Acute Disease↗
PubMed1991

Randomised trial of patient triggered ventilation versus high frequency positive pressure ventilation in acute respiratory distress.

Synchronous respiration during mechanical ventilation of preterm neonates with acute respiratory distress is extremely beneficial as it improves oxygenation and is associated with a very low incidence of pneumothorax. We have assessed which form of ventilation: patient triggered ventilation (PTV) or high frequency positive pressure ventilation (HFPPV) is most successful in provoking this beneficial respiratory interaction, synchrony. Preterm infants of less than 4 hours of age and gestational age greater than or equal to 27 weeks were entered into a randomised controlled trial. Thirteen patients received PTV, median gestational age 30 weeks (range 27-36) and 36 HFPPV, median gestational age, 29 weeks (range 27-40). HFPPV was delivered by Sechrist ventilators at rates between 61 and 120 breaths/minute. Patient triggered ventilation was delivered by an SLE ventilator and an airway pressure trigger was used. Inflation times during PTV were between 0.2 and 0.45 seconds. HFPPV provoked synchrony which persisted until extubation in 25 patients, but PTV provoked persistent synchrony only in four patients (p less than 0.05). No infant developed a pneumothorax. Eleven of 36 patients became asynchronous on HFPPV and 5 of 13 on PTV. In addition, four patients on PTV developed recurrent apnoea with deteriorating blood gases. Thus, 11 of 36 patients on HFPPV and 9 of 13 on PTV required transfer to conventional ventilation (p less than 0.05). Transfer occurred at a median of 30 hours (range 6-84) on HFPPV and 1 hour (range 1-25) on PTV, p less than 0.01. Infants who required transfer from the randomised mode of ventilation required a longer period of intubation (median 174 hours, range 30-2928) compared to 38 hours (range 1.5-456) for successful cases, regardless of randomisation (p less than 0.01). This study demonstrates PTV is significantly less successful in promoting synchrony than HFPPV. We therefore conclude HFPPV is a more useful form of respiratory support than PTV for preterm infants with acute respiratory distress.

High-Frequency Ventilation↗
PubMed2007

Setting positive end-expiratory pressure during jet ventilation to replicate the mean airway pressure of oscillatory ventilation.

BACKGROUND: High-frequency ventilation can be delivered with either oscillatory ventilation (HFOV) or jet ventilation (HFJV). Traditional clinician biases may limit the range of function of these important ventilation modes. We hypothesized that (1) the jet ventilator can be an accurate monitor of mean airway pressure (P (aw)) during HFOV, and (2) a mathematical relationship can be used to determine the positive end-expiratory pressure (PEEP) setting required for HFJV to reproduce the P (aw) of HFOV. METHODS: In phase 1 of our experiment, we used a differential pressure pneumotachometer and a jet adapter in-line between an oscillator circuit and a pediatric lung model to measure P (aw), PEEP, and peak inspiratory pressure (PIP). Thirty-six HFOV setting combinations were studied, in random order. We analyzed the correlation between the pneumotachometer and HFJV measurements. In phase 2 we used the jet as the monitoring device during each of the same 36 combinations of HFOV settings, and recorded P (aw), PIP, and DeltaP. Then, for each combination of settings, the jet ventilator was placed in-line with a conventional ventilator and was set at the same rate and PIP as was monitored during HFOV. To determine the appropriate PEEP setting, we calculated the P (aw) contributed by the PIP, respiratory rate, and inspiratory time set for HFJV, and subtracted this from the goal P (aw). This value was the PEEP predicted for HFJV to match the HFOV P (aw). RESULTS: The correlation coefficient between the pneumotachometer and HFJV measurements was r = 0.99 (mean difference 0.62 +/- 0.30 cm H(2)O, p < 0.001). The predicted and actual PEEP required were highly correlated (r = 0.99, p < 0.001). The mean difference in these values is not statistically significantly different from zero (mean difference 0.25 +/- 1.02 cm H(2)O, p > 0.15). CONCLUSIONS: HFJV is an accurate monitor during HFOV. These measurements can be used to calculate the predicted PEEP necessary to match P (aw) on the 2 ventilators. Replicating the P (aw) with adequate PEEP on HFJV may help simplify transitioning between ventilators when clinically indicated.

Airway Resistance↗
PubMed2005

Episodes of hypoxemia during synchronized intermittent mandatory ventilation in ventilator-dependent very low birth weight infants.

Distinct patterns of asynchrony, and episodes of hypoxemia, may occur in a spontaneously breathing preterm infant during conventional intermittent mandatory ventilation (IMV) on traditional time-cycled, pressure-limited ventilators. Synchronized IMV (SIMV) and assist/control ventilation are frequent modes of patient-triggered ventilation used with infant ventilators. The objective of this study was to use computerized pulse oximetry to quantify the occurrence of episodes of hypoxemia (oxygen desaturation) during SIMV vs. IMV, in preterm infants < or = 1,250 g who required mechanical ventilation at > or = 14 days of age. We performed a randomized, crossover study with each infant being randomized to IMV or SIMV (Infant Star ventilator) for initial testing for a 1-hr period. Patients were subsequently tested on the alternate modality after a stabilization period of 10 min at the same ventilator and fractional inspired oxygen concentration (FiO2) settings. Pulse oximetry data were obtained with a Nellcor N-200 monitor, a microcomputer, and a software program (SatMaster). An investigator blinded to the randomized assignment evaluated all measurements. Eighteen very low birth weight (VLBW) infants with a birth weight of 777 +/- 39 g (mean +/- SEM) and gestational age 25.1 +/- 0.3 weeks were studied. The average pulse oximeter oxygen saturation (SaO2) was higher on SIMV than IMV (P < 0.01). During SIMV, these infants had significantly fewer episodes of hypoxemia (duration of episodes of oxygen desaturation as a percentage of scorable recording time) to 86-90% SaO2 (P < 0.01), 81-85% SaO2 (P < 0.01), and 76-80% SaO2 (P < 0.05) when compared to IMV. There was also a significant decrease in percentage of time of desaturation to SaO2 < 90% (P = 0.002), < 85% SaO2 (P = 0.003), and < 80% SaO2 (P = 0.02) during SIMV vs. IMV. Our preliminary findings indicate that the use of SIMV in a population of VLBW ventilator-dependent infants (> or = 14 days of age) results in better oxygenation and decreased episodes of hypoxemia as compared to IMV.

Cross-Over Studies↗
PubMed2006

Hospitalized mechanically ventilated patients are at higher risk of enteral underfeeding than non-ventilated patients.

BACKGROUND & AIMS: Enteral nutrition (EN) is the preferred method of nutrition support in hospitalized patients but only 50-90% of the required calories are actually delivered. In order to identify where our nutrition support team (NST) should focus its activity, we prospectively evaluated the level of coverage of energy and protein needs during the first 5 days of EN in intensive care unit (ICU) and non-ICU patients and the relationship of energy and protein coverage with serum albumin, transthryretin, insulin-like growth factor-1 (IGF-1) and C-reactive protein (CRP). METHODS: Subjects (n=183) who required nutrition support and received EN were prospectively recruited. Calorie prescription was 20 and 25, 25 and 30 kcal/kg BW for women and men 60 years and <60 years, respectively. Protein needs were estimated as 1.2g protein/kg BW. Logistic regression analysis was used to estimate odds ratios (OR) for energy and protein delivery 66.6% and <66.6% and albumin, transthryretin, IGF-1 (low vs. normal) and CRP (high vs. normal) in ventilated vs. non-ventilated patients. RESULTS: Significantly more mechanically ventilated than non-ventilated patients received <66.6% of energy (71% vs. 48%) and protein (96% vs. 65%). The ventilated patients were more likely to be energy (OR 2.1, CI 1.1-4.0) and protein (OR 15.7, CI 4.9-50.8) underfed than non-ventilated patients. There was a significant association on day 5 between low protein delivery and low albumin (OR 2.9, CI 1.3-6.5), low transthyretin (OR 3.0, CI 1.4-6.5), low IGF-1 (OR 2.8, CI 1.2-6.7) and high CRP (OR 3.5, CI 1.6-7.8). CONCLUSIONS: The energy and protein needs of hospitalized patients are not met during the first 5 days of EN. Ventilated patients are more likely to be energy and protein underfed than non-ventilated patients and to have low plasma protein level. These findings support our decision to intensify EN monitoring by our NST in ventilated patients to optimize their nutritional coverage.

Aged↗
PubMed2005

Effects of manual hyperinflation and suctioning in respiratory mechanics in mechanically ventilated patients with ventilator-associated pneumonia.

Ventilator-associated pneumonia results from bacterial colonisation of the aerodigestive tract or aspiration of contaminated secretions into the lower airways. As a consequence of infection of the lung parenchyma and alveolitis, accumulation of inflammatory exudates and infiltration of airway mucosa can lead to unfavourable respiratory mechanics in ventilator-associated pneumonia. Tracheal suction is often employed by nursing staff in the management of mechanically ventilated patients with ventilator-associated pneumonia but this technique has the potential to increase respiratory resistance. Manual hyperinflation is used by physiotherapists to improve lung volume and mobilise secretions and has been shown to increase lung compliance. The effect of manual hyperinflation on airway resistance has not been studied. This study aims to demonstrate an additional mechanical benefit to the respiratory system when manual hyperinflation and suction techniques are combined, by comparing the application of manual hyperinflation and suction with suction alone on static lung compliance (C(L)) and inspiratory resistance (R(AW)) in mechanically ventilated patients with ventilator-associated pneumonia. Fifteen adult patients with ventilator-associated pneumonia were recruited and acted as their own controls. Manual hyperinflation followed by suction (manual hyperinflation plus suction) and suction alone were applied consecutively, in random order, on two occasions, four hours apart. Respiratory variables, C(L) and R(AW), were measured five times and the averaged value documented. Data were recorded before, immediately after, and 30 minutes after each intervention protocol. C(L) increased by 22% and R(AW) decreased by 21%, up to 30 minutes after manual hyperinflation plus suction, but not after suction alone. This study suggests that manual hyperinflation in conjunction with suction induces beneficial changes in respiratory mechanics in mechanically ventilated patients with ventilator-associated pneumonia.

Adult↗
PubMed2001

Ventilator-induced lung injury and recommendations for mechanical ventilation of patients with ARDS.

Mechanical ventilation is life sustaining and is the standard therapy for acute respiratory failure. The 16th century anatomist Vesalius is often credited for the earliest account of positive-pressure ventilation. In his work De humani corporis fabrica (On the Fabric of the Human Body), he described how an animal could be resuscitated by blowing into a reed inserted into a hole in its trachea. Although positive pressure ventilation using bellows was first used for drowning victims in the 1700s, there were soon concerns that such therapy could in fact be harmful to the lungs. In 1827, Leroy d'Etoille condemned bellows ventilation after discovering that it could lead to emphysema and tension pneumothoraces. Subsequently, positive pressure ventilation would be virtually abandoned for over 100 years. Despite this early concern about the potential for harm from mechanical ventilation, it is only in the last one to two decades that research into so-called ventilator-induced lung injury (VILI) has blossomed. Indeed, although initial studies have focused on which ventilatory parameters are associated with the most (or least) harm, there has been an explosion of research in the last 5 years attempting to delineate the basic cellular mechanisms by which mechanical ventilation injures the lung. Recently, there has been exciting evidence to suggest that lung injury induced by mechanical ventilation may have important systemic consequences, including multi-organ dysfunction. Lastly and most importantly, there is accumulating data from clinical trials in humans that ventilatory strategies designed to avoid VILI can in fact save lives.

Journal Article↗
PubMed2002

Increasing inspiratory time exacerbates ventilator-induced lung injury during high-pressure/high-volume mechanical ventilation.

INTRODUCTION: Ventilator-induced lung injury may be caused by overdistension of alveoli during high-pressure ventilation. In this study, we examined the effects of increasing inspiratory time on ventilator-induced lung injury. METHODS: Sprague-Dawley rats were divided into four different groups with ten animals per group. Each group was then ventilated for 30 mins with one of four ventilator strategies. All groups were ventilated with an Fio2 of 1.0 and a positive end-expiratory pressure of 0 cm H2O. Group LoP was the negative control group and was ventilated with low pressures (peak inspiratory pressure = 12 cm H2O, rate = 30, and inspiratory time = 0.5 secs). Groups iT = 0.5, iT = 1.0, and iT = 1.5 were the experimental groups and were ventilated with high pressures (peak inspiratory pressure = 45 cm H2O, rate = 10, and inspiratory times = 0.5 secs, iT = 1.0 sec, and iT = 1.5 secs, respectively). Outcome measures included lung compliance, Pao /Fio ratio, wet/dry lung weight, and dry lung/body weight. RESULTS: Final static lung compliance (p =.0002) and Pao2/Fio2 (p =.001) decreased as inspiratory time increased. Wet/dry lung weights (p <.0001) and dry lung/body weights (p <.0001) increased as inspiratory time increased. Light microscopy revealed evidence of intra-alveolar edema and hemorrhage in the iT = 1.0 and iT = 1.5 animals but not the LoP and iT = 0.5 animals. CONCLUSION: Increasing inspiratory time during high-pressure/high-volume mechanical ventilation is associated with an increase in variables of lung injury.

Animals↗
PubMed2005

Non-invasive Mechanical Ventilation Enhances Patient Autonomy in Decision-Making Regarding Chronic Ventilation.

OBJECTIVE: Patients with respiratory failure due to progressive muscle weakness often require chronic ventilatory support, but many do not make decisions regarding ventilation prior to a crisis. We studied the use of non-invasive ventilation as a tool to enable communication and facilitate decision-making regarding chronic ventilation. METHODS: Patients with profound muscle weakness and acute respiratory failure, were supported or weaned by non-invasive positive or negative pressure ventilation. The patients were then interviewed and their informed autonomous decisions were used to plan their future management. RESULTS: Non-invasive ventilation could be used safely to support patients with acute respiratory failure until decisions regarding chronic ventilation are made and as an alternative means of ventilation for those who refuse tracheostomy. CONCLUSIONS: Non-invasive ventilation may be used in patients with profound muscle weakness, as a means of enhancing patient autonomy by improving communication and maintaining ventilation until decisions about ongoing care are made.

Journal Article↗
PubMed1995

[Long-term mechanical ventilation in Japan, with special reference to home mechanical ventilation].

Some patients in respiratory care units are difficult to wean from mechanical ventilation, and may be candidates for home mechanical ventilation (HMV). HMV may improve these patients' quality of life and decrease medical expenses. Since 1987, six nationwide questionnaire surveys were done to study the status of long-term mechanical ventilation (defined as mechanical ventilation for at least 90 days) and HMV in Japan. In 1994, an additional questionnaire regarding opinions about HMV was sent to physicians, patients undergoing HMV, their families, and people in companies that deal with home ventilators. From 1987 to 1994, the number of patients who had been mechanically ventilated for at least 90 days increased from 368 to 956. According to the 1994 survey, 565 of those patients were not candidates for HMV, 235 of them were candidates for HMV but could not be shifted (reasons are given below), and 156 were shifted to HMV. The reasons that some patients who were considered to be candidates for HMV could not be shifted included a lack of caregivers at home (58.1%), the cost of a ventilator (44.5%), lack of proper health insurance (39.8%), problems with ventilator maintenance and delays in obtaining repairs (37.7%), and inadequacies in the system for providing medical care in the home (33.1%). Despite the problems entailed in shifting to HMV, many patients undergoing HMV (77.8%) and members of their families (83.3%) expressed a desire to continue this therapy. Many physicians (94.0%) said they believed that HMV improves the quality of life of patients with chronic respiratory failure. Some companies intend to begin renting ventilators for HMV. The use and development of HMV in Japan would be promoted if the national health insurance covered the costs of this therapy.

Chronic Disease↗