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Biomedical subjects

Rudolf Hering

Publications and source records attributed to Rudolf Hering.

11 recordsLinked to original sources
PubMed2006

The effects of mechanical ventilation on the gut and abdomen.

PURPOSE OF REVIEW: Mechanical ventilation generates an increase in airway pressure and, therefore, in intrathoracic pressure, which may decrease systemic and intraabdominal organ perfusion. Critically ill patients rarely die of hypoxia and/or hypercarbia but commonly develop a systemic inflammatory response that culminates in multiple-organ dysfunction syndrome and death. In the pathogeneses of this syndrome the gastrointestinal tract and liver have received considerable attention. RECENT FINDINGS: Mechanical ventilation with high positive end-expiratory pressure has been found to decrease splanchnic perfusion. Hepatic arterial buffer response is preserved and an increased hepatic arterial blood flow will compensate the decrease in portal blood flow. Despite an increased cardiac output with an acute moderate increase in arterial PCO2 during protective ventilation it cannot be expected that splanchnic and gut perfusion is improved. In the absence of a significant rise in intraabdominal pressure without impairment in cardiovascular function, splanchnic and gastrointestinal function remained unchanged during short periods of prone positioning. Spontaneous breathing during ventilator support improves systemic blood flow and gastrointestinal and splanchnic perfusion. SUMMARY: In critically ill patients mechanical ventilation should be adjusted to avoid conditions known to be associated with decreased gastrointestinal and splanchnic perfusion.

Abdomen↗
PubMed2006

Encouraging early clinical experience with deliberately delayed temporary fetoscopic tracheal occlusion for the prenatal treatment of life-threatening right and left congenital diaphragmatic hernias.

OBJECTIVE: In order to assess the effect of deliberately delayed percutaneous fetoscopic tracheal occlusion on survival of fetuses with life-threatening congenital diaphragmatic hernia. METHODS: Eight fetuses with life-threatening congenital diaphragmatic hernia underwent fetoscopic tracheal balloon occlusion between 29 + 0 and 32 + 4 weeks of gestation. Delayed occlusion was chosen in order to minimize potentially negative pulmonary effects from premature delivery as a result of fetal surgery. In addition, we wanted to become able to provide all available postnatal intensive care treatment means in these patients. RESULTS: Six of the 8 fetuses survived to discharge from hospital. CONCLUSION: Delayed fetoscopic tracheal balloon occlusion may be rewarded with lung growth sufficient to allow survival of fetuses with life-threatening congenital diaphragmatic hernia.

Balloon Occlusion↗
PubMed2005

Assisted breathing is better in acute respiratory failure.

PURPOSE OF REVIEW: Mechanical ventilation is usually provided in acute lung injury to ensure alveolar ventilation and reduce the patients' work of breathing without further damaging the lungs by the treatment itself. Although partial ventilatory support modalities were initially developed for weaning from mechanical ventilation, they are increasingly used as primary modes of ventilation, even in patients in the acute phase of pulmonary dysfunction. The aim of this paper is to review the role of spontaneous breathing ventilatory modalities with respect to their physiologic or clinical evidence. RECENT FINDINGS: By allowing patients with acute lung injury to breathe spontaneously, one can expect improvement in gas exchange and in systemic blood flow, on the basis of both experimental and clinical trials. In addition, by increasing end-expiratory lung volume, as will occur when airway pressure release ventilation is used, recruitment of collapsed or consolidated lung is likely to occur, especially in juxtadiaphragmatic lung regions. Until recently, traditional approaches to mechanical ventilatory support of patients with acute lung injury have called for adaptation of the patient to the mechanical ventilator using heavy sedation and administration of neuromuscular blocking agents. Recent investigations have questioned the utility of sedation, muscle paralysis, and mechanical control of ventilation. Further, evidence exists that lowering sedation levels will decrease the duration of mechanical ventilatory support, the length of stay in the intensive care unit, and the overall costs of hospitalization. SUMMARY: On the basis of currently available data, the authors suggest the use of techniques of mechanical ventilatory support that maintain, rather than suppress, spontaneous ventilatory effort, especially in patients with severe pulmonary dysfunction.

Analgesia↗
PubMed2005

Proportional assist versus pressure support ventilation in patients with acute respiratory failure: cardiorespiratory responses to artificially increased ventilatory demand.

OBJECTIVE: To test the hypothesis that in response to increased ventilatory demand, dynamic inspiratory pressure assistance better compensates for increased workload compared with static pressure support ventilation (PSV). DESIGN: Randomized clinical crossover study. SETTING: General intensive care u nits of a university hospital. PATIENTS: Twelve patients with acute respiratory failure. INTERVENTIONS: Patients received PSV, proportional assist ventilation (PAV), and PAV+ automatic tube compensation (ATC) in random order while maintaining mean inspiratory airway pressure constant. During each setting, ventilatory demand was increased by adding deadspace without ventilator readjustment. MEASUREMENTS AND MAIN RESULTS: Cardiorespiratory, ventilatory, and work of breathing variables were assessed by routine monitoring plus pneumotachography; airway, esophageal, and abdominal pressure measurements; and nitrogen washout. After deadspace addition, tidal volume and end-expiratory lung volume increased similarly in all ventilatory modalities. Ventilator work, peak inspiratory flow, and maximum airway pressure increased significantly during PAV+ATC when compared with PSV after deadspace addition. However, increase in ventilator work did not result in a smaller increase in patients' work of breathing with elevated ventilatory demand during PAV+ATC (PSV 807 +/- 204 mJ/L, PAV 802 +/- 193 mJ/L, and PAV+ATC 715 +/- 202 mJ/L, p = .11). Increase in patients' work of breathing was mainly caused by a significantly higher resistive workload during PAV and PAV+ATC. CONCLUSION: In patients with acute respiratory failure, dynamic inspiratory pressure assistance modalities are not superior to PSV with respect to cardiorespiratory function and inspiratory muscles unloading after increasing ventilatory demand. The latter might be explained by higher peak flows resulting in nonlinearly increased resistive workload that was incompletely compensated by PAV+ATC.

Acute Disease↗
PubMed2005

Effects of spontaneous breathing during airway pressure release ventilation on respiratory work and muscle blood flow in experimental lung injury.

STUDY OBJECTIVES: To evaluate the effects of spontaneous breathing at ambient airway pressure (Paw) and during airway pressure release ventilation (APRV) on respiratory work and respiratory muscle blood flow (RMBF) in experimental lung injury. DESIGN: Prospective experimental study. SETTING: Research laboratory of a university hospital. SUBJECTS: Twelve hemodynamically stable, analgosedated, and tracheotomized domestic pigs. MEASUREMENTS: Respiratory work was estimated by the inspiratory pressure time product (PTPinsp) of esophageal pressure, and RMBF was measured with colored microspheres. Lung injury was induced with IV boli of oleic acid. The first set of measurements was performed before induction of lung injury while pigs were breathing spontaneously at ambient Paw, the second after induction of lung injury while breathing spontaneously at ambient Paw, and the third with lung injury and spontaneous breathing with APRV. RESULTS: After induction of lung injury PTPinsp increased from 138 +/- 14 to 214 +/- 32 cm H2O s/min when pigs breathed spontaneously at ambient Paw (p < 0.05) and returned to 128 +/- 27 cm H2O s/min during APRV. While systemic hemodynamics and blood flow to the psoatic and intercostal muscles did not change, diaphragmatic blood flow increased from 0.34 +/- 0.05 before to 0.54 +/- 0.08 mL/g/min after induction of lung injury and spontaneous breathing at ambient Paw (p < 0.05) and returned to 0.32 +/- 0.05 mL/g/min during APRV (p < 0.05 vs spontaneous breathing at ambient Paw [lung injury]). CONCLUSION: Respiratory work and RMBF are increased in acute lung injury when subjects breathe spontaneously at ambient Paw. Supporting spontaneous breathing with APRV decreases respiratory work and RMBF to physiologic values.

Animals↗
PubMed2003

Measurement of functional residual capacity by nitrogen washout during partial ventilatory support.

OBJECTIVE: Evaluation of an open circuit multiple breath nitrogen washout (MBNW) technique for measurement of functional residual capacity (FRC) during partial ventilatory support using corrections for gas viscosity, sampling delay time, and re-inspired nitrogen. DESIGN: Measurements in a lung model with known reference volume simulating spontaneous breathing and duplicate measurements in patients breathing spontaneously with partial ventilatory support. SETTING. Experimental laboratory and intensive care units of a university hospital. PATIENTS: Eighteen patients with acute respiratory failure. INTERVENTIONS: Change of FiO(2) from baseline to 1.0. MEASUREMENTS AND MAIN RESULTS: FRC was measured by MBNW during spontaneous breathing with continuous positive airway pressure, pressure support ventilation, proportional assist ventilation, automatic tube compensation, and airway pressure release ventilation. In the lung model, repeated measurements at three volumes were done with all partial ventilatory support modalities, and baseline FiO(2 )was varied with one mode and FRC. The mean of differences between MBNW (FRC(MBNW)) and reference was 28 ml (1.6%), and the 2.SD-interval was 84 ml (4.9%) for all modes. Measurements up to a baseline FiO(2) of 0.8 showed differences of 5 ml (-0.3%) and the 2.SD-interval of 38 ml (2.2%) between reference and FRC(MBNW). In 18 patients, 66 duplicate measurements revealed a mean difference of 30 ml (0.9%) with a coefficient of repeatability of 358 ml (13%) independent of ventilatory mode and chronological order. CONCLUSION: This study suggests that, using corrections for gas viscosity, sampling delay time, and re-inspired nitrogen, FRC can be determined with good repeatability in patients and good accuracy in a lung model during partial ventilatory support.

Adult↗
PubMed2003

Effects of spontaneous breathing during airway pressure release ventilation on intestinal blood flow in experimental lung injury.

BACKGROUND: In critical illness, the gut is susceptible to hypoperfusion and hypoxia. Positive-pressure ventilation can affect systemic hemodynamics and regional blood flow distribution, with potentially deleterious effects on the intestinal circulation. The authors hypothesized that spontaneous breathing (SB) with airway pressure release ventilation (APRV) provides better systemic and intestinal blood flow than APRV without SB. METHODS: Twelve pigs with oleic acid-induced lung injury received APRV with and without SB. When SB was abolished, either the tidal volume or the ventilator rate was increased to maintain pH and arterial carbon dioxide tension constant as compared to APRV with SB. Systemic hemodynamics were determined by double indicator dilution. Blood flow to the intestinal mucosa-submucosa and muscularis-serosa was measured using colored microspheres. RESULTS: Systemic blood flow increased during APRV with SB. During APRV with SB, mucosal-submucosal blood flow (ml. g-1. min-1) was 0.39 +/- 0.21 in the stomach, 0.76 +/- 0.35 in the duodenum, 0.71 +/- 0.35 in the jejunum, 0.71 +/- 0.59 in the ileum, and 0.63 +/- 0.21 in the colon. During APRV without SB and high tidal volumes, it decreased to 0.19 +/- 0.03 in the stomach, 0.42 +/- 0.21 in the duodenum, 0.37 +/- 0.10 in the jejunum, 0.3 +/- 0.14 in the ileum, and 0.41 +/- 0.14 in the colon (P < 0.001, respectively). During APRV without SB and low tidal volumes, the respective mucosal-submucosal blood flows decreased to 0.24 +/- 0.10 (P < 0.01), 0.54 +/- 0.21 (P < 0.05), 0.48 +/- 0.17 (P < 0.01), 0.43 +/- 0.21 (P < 0.01), and 0.50 +/- 0.17 (P < 0.001) as compared to APRV with SB. Muscularis-serosal perfusion decreased during full ventilatory support with high tidal volumes in comparison with APRV with SB. CONCLUSION: Maintaining SB during APRV was associated with better systemic and intestinal blood flows. Improvements were more pronounced in the mucosal-submucosal layer.

Animals↗
PubMed2002

Effects of spontaneous breathing during airway pressure release ventilation on renal perfusion and function in patients with acute lung injury.

OBJECTIVE: Controlled mechanical ventilation can impair systemic and renal blood flow and function, which may be aggravated by respiratory acidosis. We hypothesized that partial ventilatory support using airway pressure release ventilation (APRV) with spontaneous breathing provides better cardiopulmonary and renal function than full ventilatory support using APRV without spontaneous breathing. DESIGN: Prospective randomized study. SETTING: Intensive care unit of a university hospital. PATIENTS: Twelve patients with acute lung injury (ALI). INTERVENTIONS: Airway pressure release ventilation with and without spontaneous breathing, maintaining either the same minute ventilation (V(E)) or the same airway pressure (Paw) limits. MEASUREMENTS: Systemic hemodynamics were estimated by double-indicator dilution, effective renal blood flow (ERBF) by para-aminohippurate, and glomerular filtration rate (GFR) by inulin clearance. RESULTS: Compared to APRV with spontaneous breathing, cardiac index (CI) was decreased when the upper Paw limit was increased to provide the same V(E) (4.26+/-1.21 l min(-1) m(-2)vs 3.72+/-0.99 l min(-1) m(-2); p<0.05) while CI was increased when Paw limits were held constant (4.91+/-1.41 l min(-1) m(-2); p<0.05). Effective renal blood flow and GFR were higher during APRV with spontaneous breathing (858+/-388 ml min(-1) m(-2) and 94+/-47 ml min(-1) m(-2)) than during APRV without spontaneous breathing and the same V(E) (714+/-236 ml min(-1) m(-2)and 82+/-35 ml min(-1) m(-2)) or the same Paw (675+/-287 ml min(-1) m(-2) and 80+/-41 ml min(-1) m(-2); p<0.05). Urine volume did not change. CONCLUSIONS: Spontaneous breathing during APRV was associated with better renal perfusion and function than APRV without spontaneous breathing applying either the same V(E) or the same Paw limits. Maintaining spontaneous breathing during ventilatory support may, therefore, be advantageous in preventing deterioration of renal function in patients with ALI.

Acute Disease↗
PubMed2002

Controlled versus assisted mechanical ventilation.

On the basis of currently available data, it can be suggested that maintained spontaneous breathing during mechanical ventilation should not be suppressed even in patients with severe pulmonary dysfunction if no contraindications, such as increased intracranial pressure, are present. Improvements in pulmonary gas exchange, systemic blood flow, and oxygen supply to tissues, which have been observed when spontaneous breathing was allowed during ventilatory support, are reflected in the clinical improvement in the patient's condition, as indicated by significantly fewer days with ventilation, earlier extubation, and shorter stays in the intensive care unit. The positive effects of spontaneous breathing have been documented only for some of the available partial ventilatory support modalities. If ventilatory modalities are limited to those whose positive effects have been documented, then partial ventilatory support can be used as a primary modality even in patients with severe pulmonary dysfunction. Whereas controlled mechanical ventilation followed by weaning with partial ventilatory support modalities has been the earlier standard in ventilation therapy, this approach should be reconsidered in view of the available data.

Humans↗
PubMed2001

Prone positioning, systemic hemodynamics, hepatic indocyanine green kinetics, and gastric intramucosal energy balance in patients with acute lung injury.

OBJECTIVE: To investigate the effects of prone positioning on systemic hemodynamics, intra-abdominal pressure (IAP), plasma disappearance rate of indocyanine green (PDR(ICG)), and gastric intramucosal to arterial PCO2 difference (Pi-aCO2). DESIGN AND SETTING: Prospective randomized study in the intensive care unit of a university hospital. PATIENTS: 12 mechanically ventilated, hemodynamically stable patients with acute lung injury. INTERVENTION: Positioning supine and prone for 3 h in random order. MEASUREMENTS: Systemic hemodynamics were determined by transpulmonary double-indicator dilution technique using an integrating fiberoptic monitoring system. The same monitoring system was used to measure PDR(ICG). IAP was measured in the urinary bladder and gastric intramucosal PCO2 was evaluated by automated recirculation gas tonometry. RESULTS: IAP increased from 10 +/-3 in the supine to 13+/-4 mmHg in the prone position. Cardiac index increased from 3.8+/-0.9 (supine) to 4.2+/-0.6 l/m(2) per minute (prone), mean arterial pressure from 75+/-10 (supine) to 81+/-11 mmHg (prone), PaO2/FIO2 from 194+/-66 (supine) to 269+/-68 mmHg (prone), and oxygen delivery from 558+/-122 (supine) to 620+/-74 ml/m(2) per minute (prone). No other parameters, including PDR(ICG) and Pi-aCO2, differed between the two positions. CONCLUSIONS: Prone positioning in mechanically ventilated patients with acute lung injury, despite a small increase in IAP, does not negatively affect the hepatic capacity to eliminate ICG and gastric intramucosal energy balance when systemic blood flow and oxygenation are improved.

APACHE↗