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PubMed2006

Attenuation of lung reperfusion injury by modified ventilation and reperfusion techniques.

BACKGROUND: High ventilation and perfusion pressures after lung transplantation may have deleterious effects. We hypothesized that using combined protective approaches for ventilation and perfusion would be optimal for reducing injury and improving function after ischemia-reperfusion. METHODS: Using an isolated, blood-perfused, rabbit lung model, lungs underwent 120 minutes of reperfusion either immediately (Sham) or after 18 hours of cold ischemia (IR). Groups Sham-P and IR-P underwent protective ventilation and reperfusion, and Groups Sham-C and IR-C underwent conventional ventilation and reperfusion. Protective ventilation involved gradually increasing the flow rate during 5 minutes to 1.8 liters/min, and conventional ventilation entailed immediate initiation of flow at 1.8 liters/min. Protective reperfusion involved gradually increasing perfusion during 5 minutes to 60 ml/min, and conventional reperfusion entailed immediate perfusion at 60 ml/min. Two other groups underwent either protective ventilation with conventional perfusion or vice versa. Airway pressure, pulmonary artery pressure, and arterial blood gases were measured throughout reperfusion. Wet/dry weight, highest oxygenation index, and bronchoalveolar lavage (BAL) protein were also measured. RESULTS: Protective ventilation and perfusion after ischemia (IR-P) resulted in significant improvements in lung function as measured by increased Po(2) and decreased Pco(2), airway pressure, and highest oxygenation index compared with conventional reperfusion (IR-C). Injury was significantly reduced in IR-P lungs as measured by reduced edema (wet/dry weight) and vascular leakage (BAL protein). In most cases, IR-P lungs performed better, with less injury than protective ventilation or perfusion alone. CONCLUSIONS: This protective approach of ventilation and perfusion after ischemia may improve lung function after transplantation, a simple method that could easily be applied clinically.

Administration, Inhalation↗
PubMed2004

A noninvasive partial carbon dioxide rebreathing technique for measurement of pulmonary capillary blood flow is also a useful oxygenation monitor during one-lung ventilation.

STUDY OBJECTIVES: To test the hypothesis that effective pulmonary capillary blood flow can be a useful indicator for estimating appropriate oxygenation and ventilation during one-lung ventilation in lung surgery. DESIGN: Prospective data analysis. SETTING: A 770-bed general teaching hospital. PATIENTS: 15 ASA physical status II and III patients undergoing elective lung surgery. INTERVENTIONS: Patients received general and thoracic epidural anesthesia and underwent lung operation with one-lung ventilation. MEASUREMENTS: We measured effective pulmonary capillary blood flow by a partial CO2 rebreathing method and oxygenation parameters during two-lung ventilation before surgery, during one-lung ventilation, and during two-lung ventilation after lung surgery. MAIN RESULTS: The effective pulmonary capillary blood flow index significantly decreased by 31.6%, which was associated with a significant decrease in arterial oxygen tension (PaO2). The pulmonary shunt fraction increased to 46.3% during one-lung ventilation. During two-lung ventilation, after chest closure, effective pulmonary capillary blood flow index divided by heart rate (i.e., effective pulmonary blood stroke flow index) was still significantly lower than that seen during two-lung ventilation before thoracotomy. There were significant correlations between effective pulmonary capillary blood flow, pulmonary blood stroke flow index, and PaO2. CONCLUSIONS: Effective pulmonary capillary blood flow index and effective pulmonary blood stroke flow index are useful indicators for determining appropriate oxygenation therapy during one-lung ventilation.

Aged↗
PubMed2005

Extremely low birthweight neonates with protracted ventilation: mortality and 18-month neurodevelopmental outcomes.

OBJECTIVE: To compare duration of ventilation to mortality and adverse neurodevelopmental outcomes among extremely low birth weight (ELBW; 501-1000 g) infants. STUDY DESIGN: Retrospective analysis of prospectively collected data from 5364 infants with a birthweight of 501 to 1000 g born at National Institute of Child Health and Human Development (NICHD) Neonatal Research Network centers from 1995 to 1998. The main outcome measures were: survival, duration of mechanical ventilation, and neurodevelopmental outcome. RESULTS: Overall survival was 71%. The median duration of ventilation for survivors was 23 days; 75% were free of mechanical ventilation by 39 days, and 7% were ventilated for > or = 60 days. Of those ventilated for > or = 60 days, 24% survived without impairment. Of those ventilated for > or = 90 days, only 7% survived without impairment. Of those ventilated > or = 120 days, all survivors were impaired. CONCLUSIONS: The prognosis for ELBW with protracted ventilation remains grim. The cohort who remain intubated have diminished survival and high rates of impairment. Parents of these infants should be informed of changes in prognosis as the time of ventilation increases.

Blindness↗
PubMed2006

Comparison of chronic illness among children receiving mechanical ventilation in a cohort of children's hospitals in 1991 and 2001.

OBJECTIVE: To compare the prevalence of chronic illness and characteristics of children who underwent mechanical ventilation in a cohort of patients at large children's hospitals between 1991 and 2001. STUDY DESIGN: This was a retrospective, cross-sectional study using the National Association of Children's Hospitals and Related Institutions (NACHRI) case mix database to identify children who underwent mechanical ventilation and compare the prevalence of chronic illness and incidence of mechanical ventilation. RESULTS: The proportion of children who underwent mechanical ventilation who had at least 1 chronic condition increased from 72% in 1991 to 75% in 2001. The incidence of mechanical ventilation in hospitalized children almost doubled during this decade, from 77 per 1000 hospitalizations in 1991 to 124 per 1000 in 2001. The rate of mechanical ventilation increased with increasing numbers of chronic conditions. The mortality of children who underwent mechanical ventilation decreased from 14% in 1991 to 11% in 2001. CONCLUSIONS: The increase in mechanical ventilation in hospitalized children is due to both an increased incidence of chronic illness and higher use within diagnostic categories. Unlike utilization of some services, the use of mechanical ventilation in hospitalized children may be a marker of increased severity of illness and need, because it is plausible that mechanical ventilation use is not primarily supply-sensitive.

Chronic Disease↗
PubMed1998

Oxyhemoglobin desaturation and aberrant carbon dioxide homeostasis during electrically stimulated exercise in a ventilator-dependent tetraplegic patient.

This single-subject case examined oxyhemoglobin saturation and alveolar end-tidal carbon dioxide levels in a ventilator-dependent tetraplegic patient undergoing electrical stimulation cycle ergometry. When exercising with a closed tracheostomy cuff under resting ventilator settings (resting intermittent mandatory ventilation; frequency = 6breaths/min, tidal volume = 83.3mL, minute ventilation =5L/min), his oxyhemoglobin saturation decreased from 100% to 92%, while alveolar endtidal carbon dioxide increased linearly to 47mmHg. These undesirable changes were corrected under adjusted intermittent mandatory ventilation conditions (frequency = 12breaths/min, tidal volume = 83.3mL, minute ventilation = 10L/min), during which oxyhemoglobin saturation remained above 98% and the alveolar end-tidal carbon dioxide trend resembled that of ventilator-independent tetraplegic individuals undergoing the same exercise. Because the subject's heart rate was higher under adjusted ventilation conditions, these responses may have been caused by augmented venous return resulting from greater abdominothoracic pumping at the higher breathing frequency. These findings support the need to modify ventilator settings in ventilator-dependent tetraplegic persons while undergoing exercise to maintain oxyhemoglobin saturation and carbon dioxide homeostasis.

Adult↗
PubMed1984

Decrease in airway pressure during high-frequency jet ventilation in infants with respiratory distress syndrome.

Using a crossover study design, we compared a system of high-frequency jet ventilation with appropriate humidification to pressure-limited conventional ventilation in 12 preterm infants with a birth weight of 1.9 +/- 0.6 kg and gestational age of 32 +/- 2 weeks who had severe respiratory distress syndrome. After a control period of conventional ventilation, high-frequency jet ventilation was administered for 1 to 3 hours at a constant rate (250/min) and inspiratory to expiratory time (1:3 or 1:4) in the same fraction of inspired oxygen as during conventional ventilation. Average peak inspiratory pressure decreased from 29 +/- 3 cm H2O during conventional ventilation to 20 +/- 4 cm H2O during high-frequency jet ventilation (P less than 0.001), whereas positive end expiratory pressure was unchanged, resulting in a reduction in mean airway pressure from 14 +/- 3 to 10 +/- 2 cm H2O (P less than 0.001). There was a simultaneous decrease in PaCO2 (39 +/- 4 to 34 +/- 4 mm Hg, P less than 0.01), but PaO2 did not change. These data indicate that short-term high-frequency jet ventilation maintains gas exchange in infants with respiratory distress syndrome despite a lower PIP and Paw, and results in smaller airway pressure swings than during conventional ventilation. Thus, high-frequency jet ventilation may offer hope for reducing barotrauma in this population.

Blood Gas Analysis↗
PubMed1998

Liquid ventilation improves pulmonary function and cardiac output in a neonatal swine model of cardiopulmonary bypass.

OBJECTIVE: Neonatal and infant cardiopulmonary bypass results in multiorgan system dysfunction. Organ protective strategies have traditionally been directed at the myocardium and brain while neglecting the sometimes severe injury to the lungs. We hypothesized that liquid ventilation would improve pulmonary function and cardiac output in neonates after cardiopulmonary bypass. METHODS: Twenty neonatal swine were randomized to receive cardiopulmonary bypass with or without liquid ventilation. In the liquid-ventilated group, a single dose of perflubron was administered before bypass. The control group was conventionally ventilated. Each animal was placed on nonpulsatile, hypothermic bypass. Low-flow cardiopulmonary bypass was performed for 60 minutes. The flow rate was returned to 125 ml/kg per minute, and after warming to 37 degrees C, the animals were removed from bypass. Hemodynamic and ventilatory data were obtained after bypass to assess the effects of liquid ventilation. RESULTS: Without liquid ventilation, cardiopulmonary bypass resulted in a significant decrease in cardiac output, oxygen delivery, and static pulmonary compliance compared with prebypass values. Input pulmonary resistance and characteristic impedance increased in these control animals. At 30, 60, and 90 minutes after bypass, the animals receiving liquid ventilation showed significantly increased cardiac output and static compliance and significantly decreased input pulmonary resistance and characteristic impedance compared with control animals not receiving liquid ventilation. CONCLUSIONS: Liquid ventilation improved pulmonary function after neonatal cardiopulmonary bypass while increasing cardiac output. The morbidity associated with cardiopulmonary bypass may be significantly reduced if the adverse pulmonary sequelae of bypass can be diminished. Liquid ventilation may become an important technique to protect the lungs from the deleterious effects of cardiopulmonary bypass.

Animals↗
PubMed1987

Survival of corneal grafts from donors supported by mechanical ventilation.

Eighty-five patients undergoing penetrating keratoplasty with tissue from donors supported by mechanical ventilation (Ventilator group) were compared to a surgeon- and diagnosis-matched group (Control group). Age at surgery, duration of follow-up, and sex of recipient patients were similar in the two groups. The mean donor age in the Ventilator group (26.4 years) was significantly less than in the Control group (45.8 years, P less than 0.0001). Mean time on the ventilator was 99.4 hours (range, 4 hours to 21 days). Overall graft survival rates in the Ventilator and Control groups were similar (P greater than or equal to 0.72). Time on the ventilator did not affect graft survival. Cultures of corneoscleral donor rims were positive more often in the Ventilator group than in Controls (39.7 versus 23.1%), but the difference was not significant (P = 0.09). Prolonged ventilator time was not associated with a higher rate of positive corneoscleral rim cultures, nor did positive cultures affect graft survival. The most common cause of graft failure in both groups was allograft rejection. In no case could postoperative bacterial infection be attributed to contamination of the donor material. One case of primary donor failure occurred in the Ventilator group, but the incidence (1.2%) is similar to that of previously reported studies. The data indicate that corneal tissue from ventilator-supported donors should be considered for use in penetrating keratoplasty.

Adolescent↗
PubMed1985

Influence of mask design on bag-mask ventilation.

Adequate positive pressure ventilation in the field or emergency department continues to represent a major challenge. A new face mask design that recently has been introduced consists of a low-pressure "balloon" through which a Guedel airway is attached and extended proximally through the mask to allow the attachment of a ventilation bag. The mask is designed to seal the nares and mouth when pressed against the face. Ventilation is achieved through the airway which extends through the mask to just above the epiglottis. We designed a study to evaluate ventilating volumes and mask leak with this mask design, and to compare these parameters with those achieved with standard masks. Thirty volunteers with varied experience in bag-mask ventilation were chosen to ventilate a specially adapted ventilation manikin connected to a test lung that was capable of simulating varied compliances. Spirometers measured volumes delivered to the ventilating bag and lung, and mask leak could be calculated from these readings. A constant rate of 12 ventilations per minute was maintained by each volunteer for two minutes. Volunteers ventilated the test lung using three masks in random sequence: the SealEasy mask (Respironics Inc, Monroeville, PA), a Laerdal mask (old type), and a transparent Robertshaw mask with inflatable black rim. The average tidal volume delivered by the SealEasy mask was consistently higher than either of the other two. Significantly (P less than .05) higher volumes were delivered with the SealEasy mask when compared to the Laerdal, and significantly lower mask leaks were seen when the SealEasy was compared to both.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed2001

Mechanical ventilation care in severe childhood neurological disorders.

Forty-five patients underwent long-term life-sustaining mechanical ventilation care in the Child Neurology Ward, National Center Hospital for Mental, Nervous and Muscular Disorders from 1990 to 2000. Twenty patients had chronic respiratory insufficiency due to neuromuscular disorders, nine of whom underwent home mechanical ventilation care. Nineteen of the 45 patients had chronic respiratory insufficiency due to progressive central nervous system disorders, three of whom underwent home mechanical ventilation care. Six patients with chronic respiratory insufficiency due to the sequelae of transient events were on ventilation, two of whom underwent home mechanical ventilation care. In some patients, especially ones with neuromuscular disorders, mechanical ventilation care is very useful for improving their daily activity and quality of life. In other patients, however, mechanical ventilation care is merely a means of prolonging life without visible improvement of their quality of life. As medical resources are limited, home mechanical ventilation care is a recommended method for patients who need life-sustaining mechanical ventilation care. Considering an individual or social consensus, the indication of long-term life-sustaining mechanical ventilation care for chronic respiratory insufficiency due to severe childhood neurological disorders should be further discussed.

Adolescent↗
PubMed1997

Halothane administration during liquid ventilation.

The objective of this study was to test the hypothesis that perfluorochemical (PFC) liquid ventilation (LV) can be used as a vehicle to deliver halothane and induce and maintain analgesia. Seven hamsters were paralysed and stabilized with mechanical gas ventilation, ventilated in alternating cycles with gas and either neat oxygenated PFC liquid or oxygenated PFC liquid mixed with liquid halothane (PFC:hal) 1:50% (volume/vapour); arterial pressure and blood gases were monitored throughout the protocol. After each cycle, the animal was stimulated with a foot clamp for 2 s. Mean arterial pressure (MAP:mmHg) response to this stimulation (percent change from the resting MAP) was used as an index of analgesia. Mean arterial pressure was significantly lower during ventilation with PFC:hal (73 +/- 7 SE) as compared with MAP during neat PFC (113 +/- 5 SE) or gas ventilation (107 +/- SE). Mean arterial pressure response (% change in MAP from baseline) to foot-clamp stimulation was significantly lower with PFC:hal ventilation (+ 12 +/- 5% SE) as compared with neat PFC (+ 28 +/- 8% SE) and gas ventilation (+ 29 +/- 9% SE). There was no statistically significant difference in resting MAP or MAP response to foot-clamp stimulation between cycles of ventilation with neat PFC alone or gas ventilation; arterial blood gases were not significantly different between modes of ventilation or levels of analgesia. The data indicate that halothane can be administered during LV while supporting gas exchange, and demonstrate the feasibility of inducing analgesia while using PFC LV techniques.

Analysis of Variance↗
PubMed2001

Preoperative prediction of prolonged mechanical ventilation following coronary artery bypass grafting.

OBJECTIVE: Few studies have attempted to evaluate who would require prolonged mechanical ventilation following heart surgery. The objectives of this study were to identify predictors of prolonged ventilation in a large group of coronary artery bypass grafting (CABG) patients from a single institution. METHODS: One thousand, eight hundred and twenty-nine consecutive patients undergoing CABG were reviewed retrospectively and evaluated for preoperative predictors of prolonged ventilation which included: age, gender, ejection fraction (EF), renal function, diabetes, angina status, New York Heart Association Class, number of diseased vessels, urgency of the procedure, re-operation, chronic lung disease (COPD) and intraoperative variables such as IABP, inotropes, stroke and myocardial infarction. Prolonged ventilation was defined as > or = 24 h. Stepwise logistic regression analysis was performed. RESULTS: Patients were on average 65.4+/-10.6 years of age, 30% were diabetic, 80% had triple vessel disease and 93% were of functional class III/IV. The mean ejection fraction was 60+/-16 percent. Overall peri-operative mortality was 2.7%. There were 157 patients that required prolonged ventilation with a peri-operative mortality of 18.5% (P < 0.001). Preoperative independent predictors of prolonged ventilation were found to be: unstable angina (OR 5.6), EF < 50 (OR 2.3), COPD (OR 2.0), preop. renal failure (OR 1.9), female gender (OR 1.8) and age > 70 (OR 1.7). Based on these predictors, a model was created to estimate of the risk of prolonged ventilation in individual patients following CABG with results ranging from < or = 3% in patients without any risk factors to > or = 32% in patients with five or more independent risk factors. Certain intraoperative variables were strong predictors of prolonged ventilation and included: stroke (OR 12.3), re-operation for bleeding (OR 6.9) and perioperative MI (OR 5.8). CONCLUSION: We were able to create a stable model where several preoperative and intra-operative variables were shown to be predictive of prolonged ventilation after CABG surgery. The ability to identify patients at increased risk for prolonged ventilation may allow the development of pre-emptive strategies and more effective resource allocation.

Age Factors↗
PubMed1997

Lung mechanical behavior during one-lung ventilation.

OBJECTIVE: Switching from two-lung to one-lung ventilation would be expected to have large effects on lung mechanical properties, and these effects may depend on tidal volume and respiratory frequency. These changes in lung mechanics with one-lung ventilation may be similar to pulmonary edema. Deteriorating lung mechanics during pulmonary edema have been attributed to a loss of ventilated lung units. Therefore, changes in lung mechanics caused by one-lung ventilation were measured and compared with those previously seen during pulmonary edema. DESIGN: Prospective study. SETTING: Research laboratory. INTERVENTIONS: After induction of anesthesia, beagle dogs' tracheas were intubated with an endotracheal tube with a bronchial blocker (Univent System Corp, Tokyo, Japan) to apply one-lung ventilation. The proper position of the bronchial blocker during one-lung ventilation was confirmed with a fiberoptic bronchoscope. MEASUREMENTS AND MAIN RESULTS: Lung elastance (EL) and resistance (RL) were calculated from measurements of airway pressure, esophageal pressure, and airway flow in five anesthetized, paralyzed dogs during sinusoidal forcing at a constant mean airway pressure of 10 cmH2O in a wide range of breathing frequencies (0.2 to 1.0 Hz in intervals of 0.2) and tidal volumes (50, 100, 200, and to 300 mL). Measurements were made before and after the left mainstem bronchus was occluded with the bronchial blocker. During ventilation of both lungs, EL and RL depended relatively little on frequency, and both EL and RL were independent of tidal volume. During one-lung ventilation, EL doubled and, at most frequencies, RL increased; frequency dependences were not increased, and no dependence on tidal volume was observed. CONCLUSIONS: The lack of tidal volume dependence in EL and lack of large-frequency dependence in RL during one-lung ventilation are inconsistent with changes induced by severe pulmonary edema. Although decreases in ventilatable lung volume may contribute to increases in lung elastance, other characteristics of mechanical behavior during one-lung ventilation differ from those of pulmonary edema; therefore, other additional mechanisms must be involved in determining lung mechanical properties during severe pulmonary edema.

Airway Resistance↗
PubMed2003

Ten-year trends in neonatal assisted ventilation of very low-birthweight infants.

OBJECTIVES: To examine ventilatory support for the VLBW infant over the past 10 years in a single academic NICU and determine factors that predicted length of ventilation, death, and CLD. STUDY DESIGN: A retrospective cohort review of neonatal blood gases, ventilatory support, and clinical outcomes. RESULTS: From 1992 through October 2002, 6254 infants were admitted, of whom 2388 required intubation for mechanical ventilation. Of these, 837 were <1500 g at birth (VLBW) infants and 453 were less than 1000 g (ELBW). Total duration of ventilation decreased in all weight groups. Noninvasive ventilatory support increased from 20 to 55% of total ventilation from 1997 to 2002. During this same period, CLD decreased from 20 to 11% in ventilated VLBW infants. Duration of total ventilation was best predicted by birth weight, with each 100 g increment decreasing the duration of ventilation by 71 hours. Lower birth weight, male sex, and a longer total duration of ventilatory support were significant factors in predicting the occurrence of CLD. Death alone was best predicted by lower birth weight and maximum oxygen index (OI). Transported infants had significantly increased maximal OIs, durations of ventilation, and incidence of death. A total of 48% of infants with a single OI >10 either died or survived with CLD. CONCLUSIONS: Birth weight is the best predictor of duration of ventilation, and CLD is best predicted by birth weight, duration of ventilation and male sex. The increasing use of noninvasive strategies has not been associated with an observable increase in respiratory morbidity. VLBW infants with a single OI>10 may benefit from inclusion in future interventional rescue studies.

Birth Weight↗
PubMed1998

The cuffed oropharyngeal airway for spontaneous ventilation anaesthesia. Clinical appraisal in 100 patients.

The cuffed oropharyngeal airway is a modified Guedel airway with a distal inflatable cuff and a proximal connector for attachment to an anaesthesia circuit. The purpose of this study was to evaluate this device for spontaneous ventilation anaesthesia in 100 adult patients. Anaesthesia was induced with fentanyl and propofol and maintained with nitrous oxide and isoflurane in oxygen. The device was inserted when anaesthetic depth was judged to be adequate. Adverse airway events and interventions (i.e., manoeuvres performed in order to provide a clear airway) were analysed from video recordings and detailed notes. The position of the device was assessed fibreoptically during spontaneous ventilation. The device provided a clear airway in 98% of patients during manually assisted ventilation, in 100% during spontaneous ventilation and in 100% during emergence. However, 91% of patients required at least one airway intervention at some time. Jaw life was required for 33% of the time during manually assisted ventilation and 21% of the time during spontaneous ventilation. Most interventions occurred during the first 3 min of either manually assisted or spontaneous ventilation. The incidence of adverse airway events during manually assisted ventilation was 8%, during spontaneous ventilation was 5% and during emergence was 5%. Oxygen saturation briefly fell to between 87 and 89% on six occasions. On fibreoptic assessment, the vocal cords were visible in 29% of patients on fibreoptic assessment and the epiglottis was visible in 90%. Mild sore throat occurred in 4% of patient. We conclude that the cuffed oropharyngeal airway is suitable for spontaneous ventilation anaesthesia and has a low complication rate but that most patients require one or more interventions to provide a clear airway.

Adolescent↗
PubMed2000

Tracheal pressure ventilator control.

Tracheal pressure ventilator control (TPVC) is a ventilator mode that relies on tracheal pressure at the carinal end of the endotracheal tube for triggering the ventilator ;;on,'' controlling pressure, and cycling the ventilator ;;off.'' TPVC automatically nullifies imposed resistive work of the breathing apparatus (endotracheal tube plus ventilator) by providing automatic and variable levels of pressure assist. TPVC improves ventilator responsiveness for a spontaneously breathing patient by providing significantly higher peak inspiratory flow rates much closer to that demanded by a patient. TPVC also provides higher assist pressures and flow rates earlier in the breath and thus better-match ventilator-supplied flow to patient-demanded flow than an equivalent level of pressure support ventilation. Matching patient demand for flow to ventilator supply of flow, early in the breath, promotes patient-ventilator synchrony and minimizes work of breathing. We recommend moving the pressure-triggering and control site to the carinal end of the endotracheal tube to provide TPVC.

Journal Article↗
PubMed2002

Survival and neurologic outcome after cardiopulmonary resuscitation with four different chest compression-ventilation ratios.

STUDY OBJECTIVE: The optimal ratio of chest compressions to ventilations during cardiopulmonary resuscitation (CPR) is unknown. We determine 24-hour survival and neurologic outcome, comparing 4 different chest compression-ventilation CPR ratios in a porcine model of prolonged cardiac arrest and bystander CPR. METHODS: Forty swine were instrumented and subjected to 3 minutes of ventricular fibrillation followed by 12 minutes of CPR by using 1 of 4 models of chest compression-ventilation ratios as follows: (1) standard CPR with a ratio of 15:2; (2) CC-CPR, chest compressions only with no ventilations for 12 minutes; (3) 50:5-CPR, CPR with a ratio of 50:5 compressions to ventilations, as advocated by authorities in Great Britain; and (4) 100:2-CPR, 4 minutes of chest compressions only followed by CPR with a ratio of 100:2 compressions to ventilations. CPR was followed by standard advanced cardiac life support, 1 hour of critical care, and 24 hours of observation, followed by a neurologic evaluation. RESULTS: There were no statistically significant differences in 24-hour survival among the 4 groups (standard CPR, 7/10; CC-CPR, 7/10; 50:5-CPR, 8/10; 100:2-CPR, 9/10). There were significant differences in 24-hour neurologic function, as evaluated by using the swine cerebral performance category scale. The animals receiving 100:2-CPR had significantly better neurologic function at 24 hours than the standard CPR group with a 15:2 ratio (1.5 versus 2.5; P =.007). The 100:2-CPR group also had better neurologic function than the CC-CPR group, which received chest compressions with no ventilations (1.5 versus 2.3; P =.027). Coronary perfusion pressures, aortic pressures, and myocardial and kidney blood flows were not significantly different among the groups. Coronary perfusion pressure as an integrated area under the curve was significantly better in the CC-CPR group than in the standard CPR group (P =.04). Minute ventilation and PaO (2) were significantly lower in the CC-CPR group. CONCLUSION: In this experimental model of bystander CPR, the group receiving compressions only for 4 minutes followed by a compression-ventilation ratio of 100:2 achieved better neurologic outcome than the group receiving standard CPR and CC-CPR. Consideration of alternative chest compression-ventilation ratios might be appropriate.

Animals↗
PubMed2006

The effect of bi-level positive airway pressure mechanical ventilation on gas exchange during general anaesthesia.

BACKGROUND: Atelectasis may occur and ventilation-perfusion mismatch may increase during general anaesthesia with neuromuscular paralysis and mechanical ventilation, though preservation of some intermittent muscle contraction might mitigate this process. There is still no ideal manoeuvre to minimize such mismatch or atelectasis. Bi-level positive airway pressure (BiPAP) ventilation adjusts to extra breaths and improves gas exchange during recovery of diaphragm function after neuromuscular paralysis. We hypothesize that BiPAP ventilation may limit the development of pulmonary shunt and may improve ventilation-perfusion mismatch when compared with standard IPPV, with or without PEEP when neuromuscular paralysis has been used during surgery. METHODS: Twenty ventilated patients either on BiPAP or IPPV with or without PEEP were studied randomly using the multiple inert gas elimination technique (MIGET) at 60 and 120 min after rocuronium at induction and after 60 min. Non-invasive cardiac output (NICO) monitoring and plasma concentrations of rocuronium were measured. We compared the data of MIGET, gas exchange, haemodynamic variables and pulmonary mechanics measurements between the different ventilatory modes. RESULTS: Intrapulmonary shunt (blood flow to V(A)/Q < 0.005) did not increase at 60 min of anaesthesia in any of the different ventilation modes compared with the shunt value before anaesthesia. Log standard deviation of perfusion increased in IPPV, with and without PEEP groups, compared with the baseline (P< 0.05) but did not increase in the BiPAP group. BiPAP ventilation generated a higher level of Pa(O2)than IPPV with or without PEEP (P<0.05). CONCLUSION: BiPAP ventilation was beneficial in decreasing ventilation-perfusion mismatch and improving oxygenation when compared with conventional IPPV (with or without PEEP).

Aged↗