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PubMed2002

Partial liquid ventilation versus conventional mechanical ventilation with high PEEP and moderate tidal volume in acute respiratory failure in piglets.

This prospective randomized pilot study aimed to test the hypotheses that partial liquid ventilation combined with a high positive end-expiratory pressure (PEEP) and a moderate tidal volume results in improved gas exchange and lung mechanics without negative hemodynamic influences compared with conventional mechanical ventilation in acute lung injury in piglets. Acute lung injury was induced in 12 piglets weighing 9.0 +/- 2.4 kg by repeated i.v. injections of oleic acid and repeated lung lavages. Thereafter, the animals were randomly assigned either to partial liquid ventilation (n = 6) or conventional mechanical ventilation (n = 6) at a fractional concentration of inspired O(2) of 1.0, a PEEP of 1.2 kPa, a tidal volume < 10 mL/kg body weight (bw), a respiratory rate of 24 breaths/min, and an inspiratory/expiratory ratio of 1:2. Perfluorocarbon liquid 30 mL/kg bw was instilled into the endotracheal tube over 10 min followed by 5 mL/kg bw/h. Continuous monitoring included ECG, mean right atrial, pulmonary artery, pulmonary capillary, and arterial pressures, arterial blood gas, and partial pressure of end-tidal CO(2) measurements. When compared with control animals, partial liquid ventilation resulted in significantly better oxygenation with improved cardiac output and oxygen delivery. Dead space ventilation appeared to be lower during partial liquid ventilation compared with conventional mechanical ventilation. No significant differences were observed in airway pressures, pulmonary compliance, and airway resistance between both groups. The results of this pilot study suggest that partial liquid ventilation combined with high PEEP and moderate tidal volume improves oxygenation, dead space ventilation, cardiac output, and oxygen delivery compared with conventional mechanical ventilation in acute lung injury in piglets but has no significant influence on lung mechanics.

Acute Disease↗
PubMedDate not supplied

Controlled prospective randomized comparison of high-frequency jet ventilation and conventional ventilation in neonates with respiratory failure and persistent pulmonary hypertension.

OBJECTIVE: The objective of this study was to evaluate the efficacy and safety of high-frequency jet ventilation in near-term and term neonates with persistent pulmonary hypertension. STUDY DESIGN: Subjects for this prospective, randomized, controlled comparison study were recruited from neonates treated in a level-three neonatal intensive care unit that accepts referrals for extracorporeal membrane oxygenation. RESULTS: In patients treated with high-frequency jet ventilation (n = 11) acute improvement in oxygenation (p = 0.008), ventilation (p < 0.001), and oxygen indices (p < or = 0.01) was demonstrated while stable peak and mean airway pressures were maintained. Control group patients receiving high-frequency positive pressure ventilation with a conventional ventilator required increasingly higher peak inspiratory pressures (p = 0.005) to maintain oxygenation, ventilation, and oxygen indices. There were no significant differences in survival without use of extracorporeal membrane oxygenation, nor were there differences in duration of oxygen therapy, ventilation, and hospitalization; need for extracorporeal membrane oxygenation; or incidence of chronic lung disease. CONCLUSIONS: High-frequency jet ventilation acutely improves oxygenation and ventilation without significantly increasing morbidity. Therefore high-frequency jet ventilation may be a useful adjunct for stabilization of the conditions of neonates with severe persistent pulmonary hypertension. Conclusions about the efficacy of high-frequency jet ventilation in improving survival without the need for extracorporeal membrane oxygenation await multicentered, collaborative investigations with large cohorts of patients.

Analysis of Variance↗
PubMed1996

Intratracheal pulmonary ventilation provides effective ventilation in a near-drowning model.

Overdistension of the lungs from high inspiratory pressure is increasingly recognized as a major contributor to lung injury and worsening respiratory failure in the child who requires prolonged mechanical ventilation. Many modes of ventilation (such as high-frequency ventilation) have been introduced in an attempt to decrease this lung injury. Recently, a new mode of tracheal ventilation, intratracheal pulmonary ventilation (ITPV), has been described. By using a catheter positioned at the carina with continuous gas flow, it is possible to achieve effective ventilation at very low pressures. The purpose of this study was to evaluate the usefulness of ITPV in a near-drowning model. Ten domestic Yorkshire swine underwent arterial, venous, and pulmonary arterial catheter as well as tracheotomy placement. All animals received 13 mL/kg of fresh water intratracheally to induce a pulmonary injury. Six pigs were ventilated for 4 hours using ITPV; the other four pigs received conventional mechanical ventilation (CMV). Circulatory and ventilatory pressures, hemodynamic variables, arterial blood gases, and end-tidal CO2 were measured before lung injury and every 30 minutes thereafter. Both proximal and distal peak and mean airway pressures were measured. The animals were ventilated as needed to maintain the arterial blood gases in the normal range. The authors found the expected changes in pulmonary compliance, oxygen requirement, and airway pressure after inducement of lung injury. The six animals treated with ITPV had significantly lower airway pressures than those of controls. Peak inspiratory pressures with ITPV were 8.2 +/- 1.9 cm H2O versus 17.8 +/- 3.7 with CMV (P < .001). Distal mean airway pressures using ITPV were 2.3 +/- 0.1 cm H2O versus 9.0 +/- 3.2 with CMV (P < .01). With respect to hemodynamic variables, there were no differences between experimental and control animals. In conclusion, ITPV can afford effective ventilation in a near-drowning model of lung injury at airway pressures significantly lower than those required with CMV. ITPV could be a very valuable addition to the currently available methods of mechanical ventilation.

Animals↗
PubMed2005

Intrahospital transport of critically ill ventilated patients: a risk factor for ventilator-associated pneumonia--a matched cohort study.

OBJECTIVE: To evaluate the impact of intrahospital transport of critically ill ventilated patients on the acquisition of ventilator-associated pneumonia. DESIGN: An exposed/unexposed matched cohort study. SETTING: An 18-bed adult medical-surgical intensive care unit in a 1,100-bed regional and teaching hospital in France. PATIENTS: From January 1, 2001, to December 31, 2002, 118 of 228 ventilated patients transported out of the intensive care unit (exposed patients) were matched with 118 unexposed patients selected among 295 ventilated patients who did not undergo intrahospital transport. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The matching process was conducted according to six criteria: duration of mechanical ventilation, duration of antibiotherapy, indication for ventilatory support, age, probability of death, and surgical procedures or not during intensive care unit stay. The rates of ventilator-associated pneumonia (as defined by usual clinical and biological criteria plus positive culture of bronchoscopy directed catheter) acquisition between exposed and unexposed patients were compared by univariate analysis and then by multivariate analysis (conditional logistic regression and Cox's proportional-hazards model) to account for potential confounding factors. The ventilator-associated pneumonia rate was 26% in exposed patients compared with 10% in the matched unexposed patients. Using conditional logistic regression, two factors were independently associated with ventilator-associated pneumonia: intrahospital transport (odds ratio, 3.1; 95% confidence interval, 1.4-6.7) and the need for reintubation. Using Cox's model, three independent risk factors were identified: the need for reintubation, enteral nutrition, and intrahospital transport (odds ratio, 2.9; 95% confidence interval, 1.4-5.7). The intensive care unit mortality rate was similar (p > .1) in exposed (35%) and unexposed patients (26%). CONCLUSIONS: Intrahospital transport appears to be a significant risk factor for ventilator-associated pneumonia. However, the respective roles of intrahospital transport and of the cause that leads clinicians to transport patients (mainly for radiographic examinations) are difficult to dissociate even after multiple statistical adjustments. When intrahospital transport is needed, very cautious measures must be taken before and during intrahospital transport to prevent ventilator-associated pneumonia. In addition, in the few days after intrahospital transport, intensive search for ventilator-associated pneumonia is justified.

Cohort Studies↗
PubMed2000

Performance of transport ventilator with patient-triggered ventilation.

OBJECTIVES: Transport ventilators with inspiratory triggering functions and pressure support-control modes have recently become commercially available. We evaluated these ventilators in comparison with a standard ICU ventilator. STUDY DESIGN: Laboratory study with a mechanical lung model. METHODS: We compared the performance of four transport ventilators (model 740, Mallinckrodt, Pleasanton, CA; TBird, Bird Products Corp, Palm Springs, CA; LTV1000, Pulmonetic Systems, Colton, CA; Esprit, Respironics, Vista, CA) with a standard ICU ventilator (model 7200ae; Mallinckrodt) using a test lung that simulated spontaneous breathing (compliance, 46.8 mL/cm H(2)O; resistance, 5 cm H(2)O/L/s). The settings of ventilators were positive end-expiratory pressure (PEEP) of 0 or 5 cm H(2)O, and pressure support (PS) of 0 or 10 cm H(2)O. The settings of the test lung were inspiratory time of 1 s, respiratory rate of 10/min, peak inspiratory flow of 40, 60, and 80 L/min. To evaluate inspiratory function at each setting, we measured the inspiratory delay time (DT), inspiratory trigger pressure (P-I), and the time for airway pressure to rise from the baseline pressure to 90% of the end-inspiratory pressure (T(90%)); for expiratory function, supraplateau expiratory pressure (P-E) and the time constant (taue) for pressure decrease during exhalation were evaluated. Oxygen requirement was assessed as the time required to empty a 3.5-L oxygen tank. RESULTS: For inspiratory triggering, four transport ventilators had DT < 100 ms, which is considered clinically satisfactory, in all the settings except for PS 0 cm H(2)O, PEEP 0 cm H(2)O, and inspiratory flow of 80 L/min with LTV1000. P-I increased only in LTV1000 when PEEP was increased from 0 to 5 cm H(2)O. taue for the transport ventilators was > 50% shorter than for the ICU ventilator except for PS 0 cm H(2)O and PEEP 5 cm H(2)O with TBird. Oxygen requirement was lowest for the Esprit, followed by the 740, LTV1000, and TBird. CONCLUSION: The newer Food and Drug Administration-approved transport ventilators have performance indexes comparable to the ventilator currently used in ICUs and can probably be recommended for clinical use.

Equipment Design↗
PubMedDate not supplied

[Association between ventilation index and time on mechanical ventilation in infants with acute viral bronchiolitis].

OBJECTIVE: To evaluate the association between time on mechanical ventilation and anthropometric, clinical and pulmonary function variables, measured early, in infants on invasive mechanical ventilation with acute respiratory failure due to viral bronchiolitis, and the temporal progression of variables with significant correlations. METHODS: Twenty-nine infants admitted to the pediatric intensive care unit of UNICAMP university hospital were studied. Acute viral bronchiolitis was defined according to clinical and radiological criteria. Children with chronic diseases and those that were hemodynamically unstable were excluded. All measurements were taken after 24 to 72 hours' mechanical ventilation, using volumetric capnography and blood gas analysis. Mechanical ventilation time was divided into: < or = 7 days and > 7 days. Association between time on mechanical ventilation and the variables analyzed was determined by Spearman's Correlation Coefficient (r(s)). RESULTS: Time on mechanical ventilation showed a significant positive correlation with PaCO(2) (rs = 0.45, p = 0.01) and ventilation index (rs = 0.51, p = 0.005), and a negative correlation with pH (rs = -0.40, p = 0.03). Ventilation indices of 37, measured between day one and day five, was associated with a progressively increased risk of more than 7 days on mechanical ventilation (OR = 4.2 on the first day to 15.71 on the fourth day). CONCLUSIONS: Ventilation index, PaCO(2) and pH, measured early, were associated with prolonged mechanical ventilation, reflecting the severity of ventilatory disturbance and the need for support.

Acute Disease↗
PubMedDate not supplied

[Comparison of patient-ventilator synchronization during pressure support ventilation versus amplified spontaneous pattern in postoperative patients].

INTRODUCTION: Patient-ventilator desynchronization can develop during weaning from proportional-assist ventilation. Poor adaptation between ventilator assistance and the patient's ventilatory demand is termed asynchrony. OBJECTIVES: Comparative analysis of types and incidence of asynchrony in patients receiving pressure support (PS) ventilation or amplified spontaneous pattern (ASP) ventilation, to determine whether the presence of asynchrony is related to a patient's level of dyspnea or anxiety. PATIENTS AND METHODS: Eighteen patients were studied prospectively after undergoing coronary revascularization. Baseline anxiety was assessed before surgery. A pleural catheter was inserted during surgery. After surgery patients were randomly assigned to ventilation with PS mode or ASP. Flow curves, flow volume, airway pressure and pleural pressure were recorded by a BioCore CP100 monitor once the patient's work of breathing held steady between 0.3 and 0.5 J/l. The curves were recorded for 10 m on a computer for later analysis. After each recording dyspnea and anxiety were assessed. Fifty consecutive cycles per patient were analyzed, signalling in each case the start of inspiration and expiration. RESULTS: Nine hundred ventilatory cycles were analyzed to identify five types of patient-ventilator asynchrony: 1) self-cycled (SC: inspiratory assistance from the ventilator without demand by patient); 2) no effort detected (NED: patient inspiratory effort but no flow response from the ventilator); 3) interrupted support (IS: interruption of ventilatory support during patient inspiration); 4) prolonged mechanical inspiration (PMI: maintenance of ventilatory support during patient expiration), and 5) double-breath, single cycle (DBSC: sequence of inspiration-expiration-inspiration of the patient within a single assisted inspiration). Asynchronic cycles were found in all PS-ventilated patients (84 of 450; 18.7%): 9.1% SC, 4% NED, 2.2% IS, 1.5% PMI and 1.8% DBSC. Asynchronic cycles were seen in only two ASP patients (16 of 450; 3.5%); both cases were NED asynchrony. Levels of anxiety and dyspnea were slightly higher with the PS mode than with ASP but the differences were not significant (p = 0.05). CONCLUSIONS: The incidence of asynchrony during assisted ventilation is very high with the PS mode and is substantially less with ASP. Asynchrony is difficult to detect clinically and is revealed only by advanced cycle-to-cycle monitoring.

Aged↗
PubMed2005

The effect of changing from pressure support ventilation to volume control ventilation on renal function.

OBJECTIVE: Mechanical ventilation increases intrathoracic pressure and decreases cardiac output, and the associated hormonal changes may affect the free water, sodium and creatinine clearance. We sought to establish if there was any difference in creatinine clearance, urine volume and fractional excretion of sodium (FE(Na)) between pressure support ventilation (PSV) and volume controlled (VC) ventilation. METHODS: The study took place in a 10 bedded metropolitan intensive care unit that admitted both medical and surgical patients. The study was a within subjects, non-randomised, controlled procedures design. Patients were included if they were ventilated on volume control ventilation (VC) with a constant positive end expiratory pressure (PEEP) and suitable for pressure support ventilation (PS), a mean arterial pressure of > 65 mmHg, a normal serum creatinine, well-hydrated and catheterised. Exclusion criteria were administration of a loop diuretic or renal dopamine in the six hours preceding the onset of the study, clinical adrenal dysfunction or clinically unstable requiring a change in intravenous fluid therapy. Eight patients completed four hours of VC ventilation and had renal functions monitored and then changed to PS ventilation for a one hour washout period. Four hours of PS were maintained and renal function monitored over a second four hour period. Patients remained on PS and then after a one hour washout on VC the final four hour monitored period on VC was completed. Urine and serum samples were collected for urine volume, fractional excretion of sodium and creatinine clearance during each four hour cycle on VC and PS ventilation. RESULTS: Friedman's test statistical analysis revealed no significant difference in creatinine clearance (p = 0.54), fractional excretion of sodium (p = 0.58) or urine volume (p = 0.42). CONCLUSIONS: VC ventilation had no adverse effects on renal indices in comparison to spontaneous PS ventilation.

Journal Article↗
PubMedDate not supplied

Spontaneous minute ventilation predicts readiness for extubation in mechanically ventilated preterm infants.

OBJECTIVE: We designed an observational study to test the hypothesis that a comparison of two methods of minute ventilation, spontaneously generated with mechanically generated, would be a useful predictor of readiness for extubation in preterm infants, weighing <2000 gm, who require mechanical ventilation for >24 hours. STUDY DESIGN: This observational study of 35 infants weighing < or = 2000 gm evaluated the comparison of spontaneously generated minute ventilation with mechanically generated minute ventilation to successfully predict readiness for extubation. After reaching entry criteria, infants were extubated if their spontaneously generated minute ventilation (while receiving endotracheal CPAP) was > or = 50% of the mechanically generated minute ventilation during assist/control ventilation. RESULTS: Of the 35 infants who had a successful trial and were extubated, 30 (86%) remained extubated for at least 24 hours. Of the five infants who failed extubation, four developed apnea and one developed stridor. Thus, a spontaneous minute ventilation of > or = 50% of mechanically generated minute ventilation predicted readiness for extubation in 86% of the patients in this observation. CONCLUSION: A spontaneously generated minute ventilation that is > or = 50% of the mechanically generated minute ventilation is an objective predictor of the readiness for extubation in low birth weight infants who have been weaned to modest ventilatory support.

Birth Weight↗
PubMedDate not supplied

A prospective, randomized comparison of the Volume Diffusive Respirator vs conventional ventilation for ventilation of burned children. 2001 ABA paper.

UNLABELLED: The Volume Diffusive Respirator (VDR) is a high-frequency time cycled pressure ventilator that can ventilate, oxygenate, and promote secretion removal. The VDR provides ventilation at lower airway pressures than those required for conventional ventilation in the pressure control mode (PCV). A prospective, randomized, institutional review board-approved study was conducted comparing the VDR to PCV in burned children with respiratory failure from all causes. METHODS: Pediatric burn patients requiring ventilation were stratified by presence of inhalation injury and ventilated by VDR or PCV to achieve predefined arterial blood gases. RESULTS: Sixty-four patients were prospectively assigned ventilator type; 32 to VDR, 32 to PCV. Data are reported as mean + SEM. Patient age was 7.4 + 0.7 years, TBSA was 56 + 3%, and number of patients with inhalation injuries was 55 (86%). Maximum peak inspiratory pressure with the VDR was significantly less than with PCV (30.9 + 0.8 cm H2O vs 39.5 + 1.8 cm H2O,P < 0.05) and the best PaO2 /FIO2 ratio was significantly higher with the VDR compared with PCV (563 + 15 vs 507 + 13, P < 0.05). No patient in the VDR group had evidence of barotrauma compared with two in the PCV group. Five patients in the PCV group died compared with two in the VDR group. CONCLUSION: Patients ventilated with the VDR required significantly lower peak inspiratory pressure and achieved a significantly higher PaO2 /FIO2 ratio compared with PCV. This demonstrates the VDR is a safe and effective method of ventilation for pediatric burn patients and it offers advantages when compared with conventional ventilation.

Adolescent↗
PubMed1989

Cardiopulmonary effects of high frequency positive-pressure ventilation versus jet ventilation in respiratory failure.

Conventional ventilators are frequently used at high rates in the intensive care nursery to achieve adequate oxygenation and ventilation with reduced peak inspiratory pressure. The efficacy and limitations of high frequency positive-pressure ventilation (HFPPV) using a conventional ventilator were studied by comparing the cardiopulmonary effects of HFPPV with those of high frequency jet ventilation (HFJV) in an animal model of respiratory failure. Sixteen saline-lavaged rabbits were ventilated with either HFPPV or HFJV for 2 h using rates of 200 breaths/min, inspiratory to expiratory ratio of 1:2, and FIO2 of 1.0. As controls an additional eight lavaged rabbits were ventilated at conventional rates (40 to 60 breaths/min). Proximal peak inspiratory pressure as indicated on the ventilator manometer or drive pressure was adjusted to maintain acceptable blood gases. Cardiac output (CO) was measured by thermodilution. Although there was a significant decrease in cardiac function over time, there were no significant differences between the groups in CO or stroke volume. Satisfactory oxygenation and ventilation were maintained in all groups. Static respiratory system compliance and mean airway pressure were similar among the groups. Histologic examination of the lungs revealed no differences between the three ventilator groups. The results of this study indicate that both HFPPV and HFJV are effective in short-term maintenance of normal blood gases in respiratory failure without any discernable differences in their effects on cardiovascular function. At very high rates, however, increases in VT are not possible with HFPPV, which limits its usefulness and flexibility in respiratory failure.

Animals↗
PubMed2000

Randomized controlled trial of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation following initial exogenous surfactant therapy.

We set out to evaluate the impact of volume-targeted synchronized ventilation and conventional intermittent mandatory ventilation (IMV) on the early physiologic response to surfactant replacement therapy in neonates with respiratory distress syndrome (RDS). We hypothesized that volume-targeted, patient-triggered synchronized ventilation would stabilize minute ventilation at a lower respiratory rate than that seen during volume-targeted IMV, and that synchronization would improve oxygenation and decrease variation in measured tidal volume (V(t)). This was a prospective, randomized study of 30 hospitalized neonates with RDS. Infants were randomly assigned to volume-targeted ventilation using IMV (n = 10), synchronized IMV (SIMV; n = 10), or assist/control ventilation (A/C; n = 10) after meeting eligibility requirements and before initial surfactant treatment. Following measurements of arterial blood gases and cardiovascular and respiratory parameters, infants received surfactant. Infants were studied for 6 hr following surfactant treatment. Infants assigned to each mode of ventilation had similar birth weight, gestational age, and Apgar scores at birth, and similar oxygenation indices at randomization. Three patients were eliminated from final data analysis because of exclusionary conditions unknown at randomization. Oxygenation improved significantly following surfactant therapy in all groups by 1 hr after surfactant treatment (P < 0.05). No further improvements occurred with time. Total respiratory rate was lowest (P < 0.05) and variation in tidal volume (V(t)) was least in the A/C group (P < 0. 05). Minute ventilation (V(')(E)), delivered airway pressures, respiratory system mechanics, and hemodynamic parameters were similar in all groups. We conclude that volume-targeted A/C ventilation resulted in more consistent tidal volumes at lower total respiratory rates than IMV or SIMV. Oxygenation and lung mechanics were not altered by synchronization, possibly due to the volume-targeting strategy. Of the modes studied, A/C, a fully-synchronized mode, may be the most efficient method of mechanical ventilator support in neonates receiving surfactant for treatment of RDS.

Blood Gas Analysis↗
PubMed2005

Patient-ventilator interaction during noninvasive positive pressure ventilation.

The interaction between the patient and the ventilator is complex,especially in a "semi-open" system as for noninvasive ventilation(NIV). Air leaks around the mask are likely to occur, and they affect patient-ventilator synchrony. Several variables may be responsible for the mismatch between the start of the neural output and that of ventilatory aid during NIV. The most common mode of ventilation is pressure support ventilation (PSV), which may result in a number of inspiratory efforts not being followed by ventilator aid. New modes of ventilation, such as proportional assist ventilation, maybe useful in improving patient tolerance to ventilation without affecting clinical outcome. The ventilatory settings are important during PSV to determine the synchrony. The inspiratory trigger function may be influenced by the amount of leaks, whereas a better synchrony may be achieved if the termination of the inspiratory phase is time cycled instead of flow cycled. A high pressurization rate results in poor compliance. Care should be paid in the choice of the interfaces because leaks in the system are associated with a substantial breath-to-breath inspiratory variation independent from the patient effort. Last, NIV should be delivered with turbine- or piston-based ventilators that are able to compensate for air leaks. With respect to the problem of sedation, we point out the importance of optimizing the environmental conditions, avoiding excessive light and noise, assuring patient comfort, and providing reassurance. When sedation is needed, we suggest the use of low doses of analgesics and neuroleptic agents in selected cases.

Humans↗
PubMed1988

Clinical efficacy of high frequency jet ventilation during extracorporeal shock wave lithotripsy of renal and ureteral calculi: a comparison with conventional mechanical ventilation.

The use of high frequency jet ventilation compared to conventional mechanical ventilation during general anesthesia for extracorporeal shock wave lithotripsy of renal or ureteral calculi can reduce stone movement. This decrease in stone movement theoretically lessens the total shock and energy requirements for stone fragmentation and perirenal tissue damage. To assess these theoretical advantages of high frequency jet ventilation, we studied patients undergoing extracorporeal shock wave lithotripsy to determine differences in stone movement during high frequency jet and conventional mechanical ventilation (30 patients), and in total shock requirements (1,174 patients). Mean stone movement in the 30 patients was 34.3 +/- 4.3 mm. during conventional mechanical ventilation compared to 4.1 +/- 1.9 mm. during high frequency jet ventilation (p less than 0.001). Mean total shocks were 1,542 +/- 212 (452 patients) during conventional mechanical ventilation compared to 1,217 +/- 165 (722 patients) during high frequency jet ventilation (p less than 0.001). Only 1 patient in the study had clinically significant perirenal tissue damage. We conclude that high frequency jet ventilation when compared to conventional mechanical ventilation results in clinically and economically beneficial decreases in total shocks for extracorporeal shock wave lithotripsy fragmentation of renal or ureteral calculi.

Anesthesia, General↗
PubMed2001

Prevention of ventilator-induced lung injury with partial liquid ventilation.

BACKGROUND/PURPOSE: Pulmonary injury from mechanical ventilation has been attributed to application of excess alveolar pressure (barotrauma) or volume (volutrauma). The authors questioned whether partial liquid ventilation (gas ventilation of the perfluorocarbon filled lung, PLV) would reduce ventilator-induced lung injury. METHODS: A tracheostomy tube and carotid artery catheter were placed in anesthetized Sprague-Dawley rats (500 +/- 50 g). Bovine serum albumin (BSA) labeled with Iodine (I) 125 was administered intraarterially. Ventilation with tidal volume (TV) of 5 mL/kg was initiated. The rats were then selected randomly to a 30-minute experimental period of one of the following ventilation protocols: continued atraumatic gas ventilation (GV, TV, 5 mL/kg; n = 10); atraumatic gas ventilation combined with intratracheal administration of 10 mL/kg perfluorocarbon (GV-PLV, TV, 5 mL/kg, n = 10); barotrauma (BT, peak inspiratory pressure [PIP], 45 cm H(2)O; n = 10); barotrauma with PLV (BT-PLV, PIP, 45 cm H(2)O; n = 8); volutrauma (VT, TV, 30 mL/kg; n = 8); or volutrauma with PLV (VT-PLV, TV, 30 mL/kg; n = 10). Animals were killed and the amount of radiolabeled BSA in both lungs was measured and normalized to the counts in 1 mL of blood from that animal (injury index). Data were analyzed by analysis of variance (ANOVA) with post-hoc t test comparison between groups. RESULTS: There was a significant difference in the (125)I-BSA injury index when all groups were compared (P <.001 by ANOVA). Post-hoc analysis showed a significant decrease in the injury index when comparing BT versus BT-PLV (P =.024) and VT versus VT-PLV (P =.014). CONCLUSION: (125)I-BSA leak produced during high-pressure or high-volume mechanical ventilation is reduced by partial liquid ventilation.

Analysis of Variance↗
PubMed2001

Volume ventilation of infants with congenital heart disease: a comparison of Dräger, NAD 6000 and Siemens, Servo 900C ventilators.

UNLABELLED: We compared the ventilation and pulmonary mechanics produced by a new anesthesia ventilator (NAD 6000) using a circle system with that produced by a critical care ventilator (Servo 900C) using a nonrebreathing circuit in infants with congenital heart disease. Twenty patients, aged 1 day to 7 mo, weighing 2.1 to 4.6 kg, were studied. The NAD 6000 had improved alveolar ventilation: PaCO(2) 43 +/- 8 vs 47 +/- 5 mm Hg (P = 0.005), end-tidal CO(2) 34 +/- 7 vs 37 +/- 5 mm Hg (P = 0.042); larger inspired tidal volumes 12.9 +/- 2.8 vs 11.3 +/- 2.2 mL/kg (P < 0.001), but with higher mean airway pressures 9.7 +/- 1.6 vs 8.6 +/- 1.3 cm H(2)O (P < 0.001). These differences in ventilation and airway pressures were not clinically significant. Although there were differences in observed ventilatory variables, both machines provided adequate ventilation when set in the volume control mode. IMPLICATIONS: We compared two ventilators for use in infants. Twenty infants undergoing surgery for congenital heart defects were randomized to receive ventilation first with one ventilator, then with the other. Although there were differences in observed ventilatory variables, both machines provided adequate ventilation when set in the volume control mode.

Anesthesia, Inhalation↗
PubMed1997

Use of intratracheal pulmonary ventilation versus conventional ventilation in meconium aspiration syndrome in a newborn pig model.

OBJECTIVE: To determine whether intratracheal pulmonary ventilation (ITPV) allows for effective oxygenation and ventilation at lower mean airway pressures and peak inspiratory pressures than conventional ventilation in a piglet model of meconium aspiration syndrome. DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at Children's National Medical Center, Washington, DC. SUBJECTS: Twenty newborn piglets, 2 to 7 days of age, weighing 1.8 to 2.8 kg. INTERVENTION: Animals were anesthetized, paralyzed, intubated, and ventilated. Femoral arterial and venous catheters were inserted; 5 mL/kg of 20% meconium in normal saline was instilled into the endotracheal tube. Animals were randomized to either ITPV or conventional ventilation, and settings were adjusted to maintain ideal blood gases, i.e., pH 7.35 to 7.45, PCO2 40 to 45 torr (5.3 to 6 kPa), PO2 80 to 100 torr (10.7 to 13.3 kPa), and SaO2 > or = 90%. Ventilatory settings were adjusted as needed to a maximum of: FIO2 1.0, peak inspiratory pressure 40 cm H2O, positive end-expiratory pressure 5 cm H2O, and respiratory rate 80 breaths/min. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases were taken every 30 mins for 4 hrs and ventilatory settings were adjusted to maintain optimal blood gases. Heart rate, mean arterial blood pressure, and arterial saturation were monitored continuously. The animals in the ITPV group had significantly lower peak inspiratory pressure at 1, 2, 3, and 4 hrs after meconium instillation (p < .018) and significantly lower mean airway pressure at 2, 3, and 4 hrs after meconium instillation (p < .03). The mean peak inspiratory pressure in the ITPV animals ranged from 17 +/- 2.7 cm H2O at baseline to 16.6 +/- 5.7 cm H2O at 4 hrs compared with 16.5 +/- 2.7 cm H2O at baseline to 31.8 +/- 9.1 cm H2O at 4 hrs in the conventionally ventilated animals (p < .04). The mean airway pressure ranged from 6.3 +/- 1.1 mm Hg at baseline to 6.8 +/- 2.5 mm Hg at 4 hrs in the ITPV group compared with 5.5 +/- 1.2 mm Hg at baseline to 10.7 +/- 3.4 mm Hg at 4 hrs in the conventional ventilation group (p < .03). The lungs of the ITPV animals were less hemorrhagic and had less pathologic evidence of injury than the lungs of the conventionally ventilated animals. CONCLUSIONS: These results indicate that ITPV can be used to effectively ventilate and oxygenate piglets with meconium aspiration syndrome at lower mean airway pressures and peak inspiratory pressures than conventional ventilation. This lower pressure causes less injury to the lungs of the animals.

Animals↗
PubMed2001

The role of dead space ventilation in predicting outcome of successful weaning from mechanical ventilation.

BACKGROUND: The exact mechanism by which tracheostomy results in clinical improvement in respiratory function and liberation from mechanical ventilation remains unknown. Physiologic dead space, which includes both normal and abnormal components of non-gas exchange tidal volume, is a clinical measure of the efficiency of ventilation. Theoretically, tracheostomy should reduce dead space ventilation and improve pulmonary mechanics, thereby facilitating weaning from mechanical ventilation. METHODS: This study compares arterial blood gases (ABG), pulmonary mechanics, including minute ventilation (VE) and dead space ventilation (Vd/Vt) within 24 hours before and after tracheostomy in 45 patients admitted to a surgical intensive care unit. RESULTS: There was no difference noted in patients' ABG or VE. Pre- and posttracheostomy change in Vd/Vt was negligible (50.7 and 10 vs. 51.9 and 11; p = NS). On subgroup analysis, those patients that were weaned from mechanical ventilation with 72 hours of tracheostomy (T3) were compared with those patients weaned from mechanical ventilation 5 days or more after tracheostomy (T+5). Again, no difference was found in pulmonary mechanics or Vd/Vt pre- and posttracheostomy. CONCLUSION: There is minimal improvement in pulmonary mechanics after tracheostomy. The change in physiologic dead space posttracheostomy does not predict the outcome of weaning from mechanical ventilation. Tracheostomy does allow better pulmonary toilet, and easier initiation and removal of mechanical ventilation and control of the upper airway.

Adolescent↗