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PubMed1991

[Evaluation of Elevent, a ventilator manufactured in Czechoslovakia for controlled ventilation during inhalation anesthesia in dogs].

Controlled breathing during halothane inhalation anesthesia was tested experimentally in fifty clinically healthy test dogs. In the first group the breathing regime was evaluated when a new Czechoslovak electronic ventilator Elvent was used in the course of 120-minute anaesthesia in 10 dogs. In the second group controlled ventilation was used in 40 dogs in the course of 180-minute anaesthesia with an administration of pipecurium as muscle relaxant. In the course of these experiments a total of 28 parameters was investigated to evaluate the effects of the given breathing regimes on the dog organism. An evaluation of the dynamics of changes in the target parameters indicated that the following model of ventilation programme with these parameters was the best: breathing rate 15-20 breaths per min., per-minute breathing capacity 1.5-3.5 l per min., breathing capacity from 0.15 to 0.25 l, inspiration length 0.8 to 1.2 s and twofold expiration length.

Anesthesia, Inhalation↗
PubMed1990

Pulmonary ventilation and perfusion abnormalities and ventilation perfusion imbalance in children with pulmonary atresia or extreme tetralogy of Fallot.

Xenon-133 lung ventilation and perfusion scans were done preoperatively after cardiac catheterization and cineangiocardiography in 19 children; 6 had pulmonary atresia with an intact ventricular septum and hypoplastic right ventricle, 4 pulmonary atresia with associated complex univentricular heart, and 9 extreme Tetralogy of Fallot. The four patients with discrepancies in the sizes of the left and right pulmonary arteries on angiography had marked asymmetry of pulmonary perfusion and ventilation-perfusion imbalance on scintigraphy. Similar degrees of asymmetry and imbalance were present in 6 of the 15 children with equal-size pulmonary vessels. Asymmetry of pulmonary perfusion and ventilation-perfusion imbalance were associated with a poor prognosis.

Child↗
PubMed1989

[A comparison between high-frequency jet ventilation (HFJV) and conventional positive end-expiratory pressure ventilation (CPPV)--an experimental study on dogs with acute lung damage].

In a controlled study on 24 dogs with severe damage to the lungs HFJV was compared to CPPV on the basis of selected cardiorespiratory parameters. The pulmonary damage was produced by injection of oleic acid (OA) into the right atrium under conventional mechanical ventilation (IPPV). After the damage, the dogs were randomly allotted into one of two groups. Twelve dogs (group I) were ventilated for 5 hours with a PEEP of 10 cm H2O (1 kPA), 12 animals (group II) for 5 hours with HFJV. The oleic-acid-induced damage results in the known hypoxaemia with an increase in the intrapulmonary shunt. After changing to CPPV, the PaO2, which fell from 27.2 +/- 3 kPa to 10.8 +/- 2.9 kPa, rises to 20.3 +/- 7.7 kPa, but shows no further significant alteration until the end of the experiment. In contrast to the clearly improved oxygenation, essential cardiocirculatory parameters (CI, SVI, RVSWI, LVSWI, TCO2) are partially reduced by more than 50% of the initial values. PAP, PCWP, HR, TPR and PVR increase significantly, MAP remaining nearly unchanged. After changeover to HFJV, there is first a further fall of PaO2 from 11.1. +/- 3.0 kPa to 9.1 +/- 1.4 kPa following OA, then, however, until the end of the experiment, a continuous elevation to 15.6 +/- 2.4 kPa with a mean airway pressure that is by 75% lower. The haemodynamic parameters show no significant changes as compared to the initial values, overall, however, they lie significantly below or above those of group I. The results from our investigations allow to draw the conclusion that, despite haemodynamic advantages, HFJV in consequence of deterioration of the arterial oxygenation currently is no alternative superior to CPPV in ventilating the severely damaged lung.

Animals↗
PubMed1989

Effect of PEEP on regional ventilation and perfusion in the mechanically ventilated preterm lamb.

Improvement of gas exchange through closer matching of regional ventilation (V) and lung perfusion (Q) with the application of positive end-expiratory pressure (PEEP) was evaluated in vivo in six mechanically ventilated preterm lambs (107-126 days/145 days gestation). Changes in V and Q were determined from in vivo scintigraphic measurements in four lung regions with inhaled radioactive 81mKr, and infused 81mKr/dextrose and/or [99mTc]MAA as PEEP was applied at 2, 4, and 6 cm H2O in each animal. Dynamic compliance varied between 0.02 and 0.40 ml/cm H2O, which was consistent with surfactant deficiency. As PEEP was increased, the regional distribution of Q shifted from the rostral to the caudal lung regions (p less than 0.02 to less than 0.05), while that of V remained unchanged. Regional V/Q matching improved together with a trend towards improvement of arterial blood gases as PEEP was increased from 2 to 4 cm H2O. Pulmonary scintigraphy offers a noninvasive methodology for the quantitative assessment of regional V and Q matching in preterm lambs and may be clinically applicable to ventilated neonates.

Animals↗
PubMed1994

Volume-controlled ventilation and pressure-controlled inverse ratio ventilation: a comparison of their effects in ARDS patients.

Volume-controlled ventilation with positive end-expiratory pressure (PEEP) (CPPV) is the conventional ventilatory approach in adult respiratory distress syndrome (ARDS) patients, but some reports suggest that pressure-controlled ventilation with an inverse inspiratory to expiratory ratio (PCIRV) may improve gas exchange in these patients. We analysed the acute effects on gas exchange, lung mechanics and haemodynamics induced by CPPV and PCIRV in ARDS patients. CPPV and PCIRV were applied randomly in ARDS patients. During CPPV, external PEEP was titrated according to the initial inflection point in the static pressure-volume (P-V) curve of the respiratory system, or it was 10 cmH2O when there was no inflection. During PCIRV, external PEEP was not applied, and inspiratory to expiratory (I/E) ratio was inversed until total PEEP was equal to the inflection point in the P-V curve, or it was 10 cmH2O. Respiratory rate, fractional inspiratory oxygen (FIO2), and tidal volume (VT) were kept constant in both modes. Eight ARDS patients were studied prospectively and admitted to a general Intensive Care Unit (ICU) of a University Hospital. Haemodynamic measurements, airflow (V), airway pressure (Paw) and VT were obtained using standard methods. We did not observe any significant change between CPPV and PCIRV with respect to: arterial oxygen tension (PaO2) 117 +/- 12 vs 107 +/- 15 mmHg (16 +/- 2 vs 14 +/- 2 kPa), arterial carbon dioxide tension (PaCO2) 40 +/- 2 vs 39 +/- 2 mmHg (6 +/- 0.3 vs 5 +/- 0.3 kPa), intrapulmonary shunt function (QS/QT) 36 +/- 3 vs 38 +/- 4%, cardiac output (CO) 7.1 +/- 0.7 vs 7 +/- 0.8 l.min-1, and total PEEP 9.7 +/- 0.6 vs 9 +/- 0.3 cmH2O. Oxygen transport and total respiratory system compliance remained unchanged in both modes. Mean Paw was slightly lower during CPPV (17 +/- 1 cmH2O) than during PCIRV (19 +/- 1 cmH2O). PCIRV does not appear to have clinical advantages over CPPV in terms of gas exchange, haemodynamics, or static lung mechanics when using the same total PEEP and minute ventilation.

Adult↗
PubMed1984

Combined high-frequency oscillatory ventilation and intermittent mandatory ventilation in critically ill neonates.

Combined high-frequency oscillatory ventilation (HFOV) and intermittent mandatory ventilation (IMV) was used in 12 neonates with inadequate gas exchange with conventional IMV. Diagnoses included diaphragmatic hernia with hypoplastic lungs, pneumonia, persistent fetal circulation, and severe respiratory distress syndrome. In most patients there was severe air leak. Within 10 hours of beginning HFOV-IMV the mean arterial PCO2 fell from 60 +/- 5 (means +/- SEM) to 38 +/- 2 mm Hg (P less than 0.01) and the mean IMV rate was reduced from 96 +/- 8 to 17 +/- 4 breaths per minute (P less than 0.001). The mean arterial-alveolar oxygen tension ratio rose from 0.05 +/- 0.01 to 0.09 +/- 0.01 (P less than 0.005). Mean airway pressure in the trachea was reduced from 16 +/- 2 to 10 +/- 3 cm H2O (P less than 0.05). Four patients died, three of whom had diaphragmatic hernias with hypoplastic lungs. Five of the eight survivors had mild bronchopulmonary dysplasia requiring supplemental oxygen. These studies demonstrate that in some neonates with respiratory failure who fail to respond to conventional IMV, combined HFOV-IMV can be successful.

Bronchopulmonary Dysplasia↗
PubMed1995

Respiratory mechanics by least squares fitting in mechanically ventilated patients: applications during paralysis and during pressure support ventilation.

OBJECTIVE: To evaluate a least squares fitting technique for the purpose of measuring total respiratory compliance (Crs) and resistance (Rrs) in patients submitted to partial ventilatory support, without the need for esophageal pressure measurement. DESIGN: Prospective, randomized study. SETTING: A general ICU of a University Hospital. PATIENTS: 11 patients in acute respiratory failure, intubated and assisted by pressure support ventilation (PSV). INTERVENTIONS: Patients were ventilated at 4 different levels of pressure support. At the end of the study, they were paralyzed for diagnostic reasons and submitted to volume controlled ventilation (CMV). MEASUREMENTS AND RESULTS: A least squares fitting (LSF) method was applied to measure Crs and Rrs at different levels of pressure support as well as in CMV. Crs and Rrs calculated by the LSF method were compared to reference values which were obtained in PSV by measurement of esophageal pressure, and in CMV by the application of the constant flow, end-inspiratory occlusion method. Inspiratory activity was measured by P0.1. In CMV, Crs and Rrs measured by the LSF method are close to quasistatic compliance (-1.5 +/- 1.5 ml/cmH2O) and to the mean value of minimum and maximum end-inspiratory resistance (+0.9 +/- 2.5 cmH2O/(l/s)). Applied during PSV, the LSF method leads to gross underestimation of Rrs (-10.4 +/- 2.3 cmH2O/(l/s)) and overestimation of Crs (+35.2 +/- 33 ml/cmH2O) whenever the set pressure support level is low and the activity of the respiratory muscles is high (P0.1 was 4.6 +/- 3.1 cmH2O). However, satisfactory estimations of Crs and Rrs by the LSF method were obtained at increased pressure support levels, resulting in a mean error of -0.4 +/- 6 ml/cmH2O and -2.8 +/- 1.5 cmH2O/(l/s), respectively. This condition was coincident with a P0.1 of 1.6 +/- 0.7 cmH2O. CONCLUSION: The LSF method allows non-invasive evaluation of respiratory mechanics during PSV, provided that a near-relaxation condition is obtained by means of an adequately increased pressure support level. The measurement of P0.1 may be helpful for titrating the pressure support in order to obtain the condition of near-relaxation.

Acute Disease↗
PubMed1980

Hemodynamics and renal function during low frequency positive pressure ventilation with extracorporeal CO2 removal. A comparison with continuous positive pressure ventilation.

Six lambs were anesthetized and connected venovenous mode to a Membrane Lung for Extracorporeal CO2 removal. The animals underwent several hours periods of continuous positive pressure ventilation (CPPV), at 5 cmH2O positive end expiratory pressure (PEEP), alternated with several hours periods of low frequency positive pressure ventilation (5 cmH2O PEEP, 2 b.p.m.) with extracorporeal CO2 removal (LFPPV-ECCO2R). During LFPPV-ECCO2R compared with CPPV, cardiac output increased by 26%, pulmonary vascular resistances and systemic vascular resistances decreased by 28% and 22% respectively. The renal function improved significantly during LFPPV-ECCO2R compared with CPPV, i.e. urinary flow, creatinine clearance and osmolar clearance increased by 50%, 37% and 52% respectively. In these experiments LFPPV-ECCO2R, a form of completely artificial ventilation, seems to prevent hemodynamic and renal complications of CPPV.

Animals↗
PubMed1991

Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure ventilation (PEEP) on cardiorespiratory function in acute respiratory failure.

Combined effects of inversed ratio ventilation (IRV) with positive end-expiratory pressure (PEEP) on cardiorespiratory function were examined in 24 patients with acute respiratory failure. Patients were divided into two groups: the IRV group (n = 12) who showed no significant increase in Pa(O)(2) with a 6 cmH(2)O of PEEP and PEEP group (n = 12) who were ventilated mechanically with PEEP only at maximum level of 10 cmH(2)O. In IRV group step-wise prolongation of the I : E ratio from 1 : 1.9 to 2.6 : 1 or 4 : 1 was applied as a Pa(O)(2) was improved and in PEEP group also level of PEEP was increased from 0, 5 to 10 cmH(2)O after one hour period irrespective of Pa(O)(2). Inversed ratio ventilation and PEEP increased significantly Pa(O)(2)/F i(O)(2), the increase being observed 6 hrs (I : E = 2 : 1) and 2 hrs (10 cmH(2)O) after starting IRV or PEEP. Further improvement of oxygenation was not observed in IRV even if I : E ratio was prolonged up to 2.6 : 1 or 4 : 1. These results suggested that combinations of IRV with PEEP were effective and an I : E ratio of 2 : 1 may be optimal, and IRV is advantageous compared to PEEP, but will take more long time to improve oxygenation than PEEP.

Journal Article↗
PubMed2006

Quality of lay person CPR performance with compression: ventilation ratios 15:2, 30:2 or continuous chest compressions without ventilations on manikins.

The new CPR guidelines emphasise chest compression depth and have increased the compression:ventilation ratio to cause less time intervals without chest compressions. How this change may influence the quality of chest compressions is not documented. Sixty-eight volunteers among travellers at Oslo international airport and a senior citizen centre performed 5 min of CPR on a manikin with compression:ventilation ratios 15:2, 30:2 or continuous chest compressions. Median age was 37.5 years (range 15-87), 59% were men, and 71% reported CPR training median 8 years (3-15) previously. Three of 22, 4 of 23 and 3 of 23 subjects in the 15:2, 30:2 and continuous compressions groups respectively stopped before 5 min had passed. Mean compression depth was 41 +/- 11, 45 +/- 8 and 30 +/- 8 mm, respectively. Depth was reduced as a function of time in the continuous compression group. Number of compressions per minute was 40 +/- 9, 43 +/- 14 and 73 +/- 24 and percent no flow time 49 +/- 13%, 38 +/- 20% and 1 +/- 2%, respectively. In conclusion, continuous chest compressions without ventilations gave significantly more chest compressions per minute, but with decreased compression quality. No flow time for 30:2 was significantly less than for 15:2.

Adolescent↗
PubMed1986

Pleural effusion causing unmatched ventilation defects in ventilation and perfusion scanning.

In a survey of patients who had chest radiographs and ventilation and perfusion radionuclide scans, 20 patients had pleural thickening or effusion. Defects of ventilation unmatched with defects of perfusion occurred in 13 of the 20. This usually occurred if the fluid was freely mobile and was a result of the procedure adopted for imaging. Upon injection in the supine position, labelled albumin microspheres were trapped in the areas perfused at that time. Since, in this position, the effusion moved posteriorly, the bases of the lungs were better perfused than the dependent areas. On imaging in the erect position when the effusion was subpulmonary, the microspheres remained in the base but the ventilation was reduced, resulting in a mismatch in the basal regions. This appearance could be misinterpreted.

Humans↗
PubMed1984

[Emergency translaryngeal ventilation with a Tuohy needle. Use in case of an inability to intubate and ventilate a curarized patient].

Intermittent translaryngeal insufflations of oxygen at high pressure by a needle could be a life-saving procedure, especially in a patient whose trachea the anesthesiologist was unable to intubate or ventilate. This study was designed to evaluate the quality of translaryngeal ventilation performed with a 16-gauge Tuohy needle and an oxygen pressure of 3 bar (300 kPa) in comparison with an usual plastic cannula of the same calibre. The studies carried out in the laboratory have shown a distinct advantage over the conventional cannula. Whereas an O2 jet delivered by a straight cannula impinged on the posterior wall of the larynx and trachea, the curved tip of the Tuohy needle deflected the axis of the O2 flow emerging from it, which then lay parallel to the longitudinal axis of the trachea. Consequently, gas flow through a simulated trachea was increased (2610 ml X s-1 vs 1240 ml X s-1), the inflation pressure being higher and the tidal volume larger. Moreover, the likelihood of injury to the posterior wall of the airway was reduced; the Tuohy needle held with a clamp close to the skin was more stable in position. Blood gases and clinical data obtained in 10 anesthetized and curarized patients without airway obstruction made it clear that translaryngeal insufflations with a 16-gauge Tuohy needle provided adequate ventilation (PaO2 values between 174 and 851 mmHg, PaCO2 between 38 and 64 mmHg). It was concluded that this technique was an efficient alternative in case of an inability to intubate a patient in apnea.

Blood Gas Analysis↗
PubMed1999

Production of nitrogen dioxide during nitric oxide therapy using the Servo Ventilator 300 during volume-controlled ventilation.

BACKGROUND: Inhaled nitric oxide may be useful in the treatment of pulmonary hypertension and hypoxaemia. Nitric oxide is rapidly oxidized to nitrogen dioxide, which is toxic and may adversely affect the airways of the patient. The aim of the present investigation was to examine factors that may affect the concentration of nitrogen dioxide, using the Servo Ventilator 300 nitric oxide delivery system, where nitric oxide is flow-proportionally mixed with the main ventilatory flow in the proximal part of the inspiratory limb. METHODS: In this experimental study nitric oxide and nitrogen dioxide levels were measured at the inspiratory site of a Y-piece with a chemiluminescence analyzer and electrochemical fuel cells. The effects of different concentrations of nitric oxide and oxygen, minute volume, different tube lengths, a soda lime absorber, and a humidifier placed in the inspiratory limb were evaluated. RESULTS: The concentration of nitrogen dioxide was dependent on the concentrations and residence time of nitric oxide with oxygen and the minute volume ventilation used. A soda lime absorber reduced concentrations of nitrogen dioxide at the expense of almost corresponding reductions in inhaled concentrations of nitric oxide. A humidifier increased the concentration of nitrogen dioxide, to an extent depending on the water volume and temperature used. CONCLUSION: Concentrations of nitric oxide and oxygen, minute volume ventilation, and residence time in the inspiratory part of the ventilatory circuit were factors that affected the generation of nitrogen dioxide. A soda lime absorber in this system is not recommended.

Administration, Inhalation↗
PubMed1983

High frequency jet ventilation v. manual jet ventilation during bronchoscopy in patients with tracheo-bronchial stenosis.

Six patients with airway stenosis were submitted to bronchoscopy under general anaesthesia. Each was ventilated with a gas mixture of 50% oxygen and nitrogen using successively manual jet insufflation (JV) using the Sanders technique at 20 b.p.m., and high frequency jet ventilation (HFJV) at rates of 150, 300 and 500 b.p.m. The effects on alveolar ventilation were assessed by blood-gas analysis and the transcutaneous monitoring of carbon dioxide tension. It is concluded that HFJV achieves satisfactory operating conditions, and provides adequate gas exchanges up to a rate of 300 b.p.m. At the faster rate some degree of hypoxaemia and hypercarbia were noted. The correlation between PaCO2 and transcutaneous carbon dioxide tension was satisfactory.

Anesthesia, General↗
PubMed1981

Interactions among ventilation, the circulation, and the uptake and distribution of halothane--use of a hybrid computer multiple model: II. Spontaneous vs. controlled ventilation, and the effects of CO2.

The authors have described a basic hybrid computer multiple model of the circulation, ventilation, and uptake and distribution of halothane in a companion paper. A multiple model consists of two or more submodels, each of which is complete in itself and could operate independently. In a multiple model, however, each submodel interacts with the others. The present paper describes the addition of a CO2-control loop (submodel), through which the partial pressure of CO2 modulates ventilation, as well a myocardial "contractility," arterial pressure, cardiac output, and regional vascular resistances. The concentration of halothane modifies these CO2-induced modulations. The CO2- and halothane-induced changes in ventilation and circulation in turn modify the uptake and distribution of halothane. Thus, a complex set of interrelationships among the submodels and compartments exists.

Anesthesia, Inhalation↗
PubMed1991

Myocardial perfusion as assessed by thallium-201 scintigraphy during the discontinuation of mechanical ventilation in ventilator-dependent patients.

Patients who cannot be separated from mechanical ventilation (MV) after an episode of acute respiratory failure often have coexisting coronary artery disease. The authors hypothesized that increased left ventricular (LV) wall stress during periods of spontaneous ventilation (SV) could alter myocardial perfusion in these patients. Using thallium-201 (201TI) myocardial scintigraphy, the authors studied the occurrence of myocardial perfusion abnormalities during periods of SV in 15 MV-dependent patients (nine women, six men; aged 71 +/- 7 yr, mean +/- SD). Fourteen of these patients were studied once with 201TI myocardial scintigraphy during intermittent mechanical ventilation (IMV) and again on another day, after at least 10 min of SV through a T-piece. One patient was studied during SV only. Thirteen of 14 of the patients (93%) studied during MV had abnormal patterns of initial myocardial 201TI uptake, but only 1 patient demonstrated redistribution of 201TI on delayed images. The remainder of the abnormalities observed during MV were fixed defects. SV produced significant alterations of myocardial 201TI distribution or transient LV dilation, or both, in 7 of the 15 patients (47%). Four patients demonstrated new regional decreases of LV myocardial thallium concentration with redistribution of the isotope on delayed images. The patient studied only during SV also had myocardial 201TI defects with redistribution. Five patients (3 also having areas of 201TI redistribution) had transient LV dilation during SV.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2002

Conventional mechanical ventilation is associated with bronchoalveolar lavage-induced activation of polymorphonuclear leukocytes: a possible mechanism to explain the systemic consequences of ventilator-induced lung injury in patients with ARDS.

BACKGROUND: Protective ventilatory strategies have resulted in a decreased mortality rate in acute respiratory distress syndrome, but the underlying mechanisms remain unclear. The authors hypothesized that (1) mechanical ventilation modulates activation of polymorphonuclear leukocytes (PMNs), (2) the consequent release of proteinases is correlated with a systemic inflammatory response and with multiple organ dysfunction, and (3) these deleterious effects can be minimized by a protective ventilatory strategy. METHODS: Human PMNs were incubated with bronchoalveolar lavage fluid obtained from patients at entry or 36 h after randomization to ventilation with either a conventional (control) or a lung-protective strategy. PMN oxidant production and surface expression of adhesion molecules and granule markers, including CD18, CD63, and L-selectin, were measured by flow cytometry. Extracellular elastase activity was quantified using a fluorescent substrate. RESULTS: Bronchoalveolar lavage obtained from both groups of patients at entry showed similar effects on PMN oxidant production and expression of surface markers. At 36 h, exposure of PMNs to bronchoalveolar lavage fluid from the control group resulted in increased PMN activation as manifested by a significant increase in oxidant production, CD18, and CD63 surface expression, and shedding of L-selectin. By contrast, these variables were unchanged at 36 h in the lung-protective group. There was a significant correlation between the changes of the variables and changes in interleukin-6 level and the number of failing organs. CONCLUSIONS: Polymorphonuclear leukocytes can be activated by mechanical ventilation, and the consequent release of elastase was correlated with the degree of systemic inflammatory response and multiple organ failure. This result may possibly explain the decreased mortality in acute respiratory distress syndrome patients treated with a lung-protective strategy.

Analysis of Variance↗