Right ventricular myocardial function in ARF patients

Objective To examine the hemodynamic effects of external positive end-expiratory pressure (PEEP) on right ventricular (RV) function in acute respiratory failure (ARF) patients.Design Prospective, with retrospective analysis on the basis of RV volume response to PEEP.Setting General intensive care unit in a university teaching hospital.Patients 20 mechanically ventilated ARF patients (mean lung injury score=2.6±0.45 SD).Intervention Incremental levels of PEEP (0–5–10–15 cmH₂O) were applied and RV hemodynamics were studied by means of a Swan-Ganz catheter with a fast-response thermistor for right ventricular ejection fraction (RVEF) measurement. According to their response to PEEP 15, two groups of patients were defined: group A (9 patients) with unchanged or increased RV end-diastolic volume index (RVED-VI) and group B (11 patients) with decreased RVEDVI.Measurements and results At zero PEEP (ZEEP) the hemodynamic parameters of the two groups did not differ. In group A, cardiac index (CI) and stroke volume index (SI) decreased at all PEEP levels (5, 10, and 15 cmH₂O), while RVEF started to decrease only at a PEEP of 10 cmH₂O (–10.8%), and RVES(systolic)VI increased only at PEEP 15 cmH₂O (+21.5%). RVED-VI was not affected by PEEP. In group B, CI and SI decreased at all PEEP levels (5, 10, and 15 cmH₂O). Similarly, RVEDVI started to decrease at PEEP 5 cmH₂O, while RVESVI decreased only at PEEP 15 cmH₂O (–21.4%). RVEF was not affected by PEEP in this group. In each patient the slope of the relationship between RVEDVI and right ventricular stroke work index (RVSWI), expressing RV myocardial performance, was studied. This relationship was significant (no change in RV contractility) in 8 of 11 patients in group B and in only 2 patients in group A. In 4 patients in group A, PEEP shifted the RVSWI/RVEDVI ratio rightward in the plot, indicating a decrease in RV myocardial performance in these patients.Conclusions PEEP affects RV function in ARF patients. The decrease in cardiac output is more often associated with a preload decrease and no change in RV contractility. On the other hand, the finding of increased RV volumes with PEEP may be associated with a reduction in RV myocardial performance. Thus, these results suggest that assessment of RV function by PEEP and preload recruitable stroke work may disclose otherwise unpredictable alterations in RV function.Partially supported by Consiglio Nazionale delle Ricerche grant, Italy     

Right ventricular function in COPD patients during weaning from mechanical ventilation

We studied the right ventricular function during a successful weaning period in 7 COPD patients without LV disease who had been mechanically ventilated for several days after an acute exacerbation of their disease. A Swan-Ganz ejection fraction thermodilution catheter performed measurements of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume index (RVEDVI) before and fifteen minutes after disconnection from the ventilator at the maintenance FiO₂. Although pulmonary artery pressure (PAP) rose from 25±4 to 28.5±4.5 mmHg after disconnection from the ventilator, RVEF (0.36±0.56 to 0.35±0.12) and RVEDVI (117±51 to 126±52 ml/m²) remained similar in both conditions. We concluded that right ventricular systolic function assessed with modified pulmonary artery catheter was maintained during the weaning phase in such weanable patients. This method could easily detect any fall of RVEF or diastolic RV enlargement able to impair the weaning in some patients.     

Prostacyclin and right ventricular function in patients with pulmonary hypertension associated with ARDS

Eight patients who developed pulmonary artery hypertension during the adult respiratory distress syndrome (ARDS) were treated with an infusion of prostacyclin (PGI₂, 12.5–35.0 ng·kg^–1·min^–1) for 45 min. We examined whether reducing the right ventricular (RV) outflow pressures by PGI₂ infusion would increase the right ventricular ejection fraction (RVEF) measured by thermodilution. PGI₂ reduced the pulmonary artery pressure (PAP) from 35.6 to 29.1 mmHg (p<0.01). The cardiac index (CI) increased from 4.2 to 5.81·min^–1·m^–2 (p<0.01) partly due to an increased stroke volume. The decreased PAP together with the increased CI resulted in a fall of the calculated pulmonary vascular resistance index (PVRI, from 5.1 to 2.5 mmHg·min·m²·1^–1,p<0.01). In the patients with subnormal baseline RVEF the increased stroke volume was associated with an increased RVEF (from 47.6% to 51.8%,p<0.05) suggesting improved RV function. This result was underscored by a significant relationship between the changes in PVRI and RVEF (r=0.789, % RVEF=–2.11·PVRI-1.45). Despite an increased venous admixture from 27.8% to 36.9% (p<0.05) the arterial PO₂ remained constant resulting in an increased oxygen delivery from 657 to 894 ml·min^–1·m^–2 (p<0.01). We conclude that short term infusions of PGI₂ increased CI concomitant to improved RV function parameters when baseline RVEF was depressed. Since improved oxygen availability should be a major goal in the management of patients with ARDS PGI₂ may be useful to lower pulmonary artery pressure in ARDS.Supported by the Deutsche Forschungsgemeinschaft (grant Fa 139/2-2)     

Effects of inhaled nitric oxide on right ventricular function in severe acute respiratory distress syndrome

Objective To compare the effects of inhaled nitric oxide (NO) and an infusion of prostacyclin (PGI₂) on right ventricular function in patients with severe acute respiratory distress syndrome (ARDS).Design Randomized prospective short-term study.Setting: Post-surgical ICU in an university hospital.Patients 10 patients with severe ARDS referred to our hospital for intensive care.Interventions In random sequence the patients inhaled NO at a concentration of 18 parts per million (ppm) followed by 36 ppm, and received an intravenous infusion of PGI₂ (4 ng·kg^–1·min^–1).Measurement and results Inhalation of 18 ppm NO reduced the means (±SE) pulmonary artery pressure (PAP) from 33±2 to 28±1 mmHg (p=0.008), increased right ventricular ejection fraction (RVEF), as assessed by thermodilution technique, from 28±2 to 32±2% (p=0.005), decreased right ventricular end-diastolic volume index from 114±6 to 103±8 ml·m^–2 (p=0.005) and right ventricular end-systolic volume index from 82±4 to 70±5 ml·m^–2 (p=0.009). Mean arterial pressure (MAP) and cardiac index (CI) did not change significantly. The effects of 36 ppm NO were not different from the effects of 18 ppm NO. Infusion of PGI₂ reduced PAP from 34±2 to 30±2 mmHg (p=0.02), increased RVEF from 29±2 to 32±2% (p=0.02). Right ventricular end-diastolic and end-systolic volume indices did not change significantly. MAP decreased from 80±4 to 70±5 mmHg (p=0.03), and CI increased from 4.0±0.5 to 4.5±0.5 l·min^–1·m^–2 (p=0.02).Conclusions Using a new approach to selective pulmonary vasodilation by inhalation of NO, we demonstrate in this groups of ARDS patients that an increase in RVEF is not necessarily associated with a rise in CI. The increase in CI during PGI₂ infusion is probably related to the systemic effect of this substance.Supported by DFG Fa 139/1-2/2-2     

Effects of positive end-expiratory pressure on right ventricular function in COPD patients during acute ventilatory failure

Objective To examine the effects of external positive end-expiratory pressure (PEEP) on right ventricular function in chronic obstructive pulmonary disease (COPD) patients with intrinsic PEEP (PEEPi).Design Prospective study.Setting General intensive care unit in a university teaching hospital.Patients Seven mechanically ventilated flow-limited COPD patients (PEEPi=9.7±1.3 cmH₂O, mean±SD) with acute respiratory failure.Intervention Hemodynamic and respiratory mechanic data were collected at four different levels of PEEP (0-5-10-15 cmH₂O).Measurements and results Hemodynamic parameters were obtained by a Swan-Ganz catheter with a fast response thermistor. Cardiac index (CI) and end-expiratory lung volume (EELV) reductions started simultaneously when the applied PEEP was approximately 90% of PEEPi measured on 0 cmH₂O (ZEEP). Changes in transmural intrathoracic pressure (PEEPi,cw) started only at a PEEP value much higher (120%) than PEEPi. The reduction in CI was related to a decrease in the right enddiastolic ventricular volume index (RVEDVI) (r=0.61;p<0.001). No correlation between CI and transmural right atrial pressure was observed. The RVEDVI was inversely correlated with PEEP-induced changes in EELV (r=–55;p<0.001), but no with PEEPi,cw (r=–0.08; NS). The relationship between RVEDVI and right ventricular stroke work index, considered an index of contractility, was significant in three patients, i.e., PEEP did not change contractility. In the other patients, an increase in contractility seemed to occur.Conclusions In COPD patients an external PEEP exceeding 90% of PEEPi causes lung hyperinflation and reduces the CI due to a preload effect. The reduction in RVEDVI seems related to changes in EELV, rather than to changes in transmural pressures, suggesting a lung/heart volume interaction in the cardiac fossa. Thus, in COPD patients, application of an external PEEP level lower than PEEPi may affect right ventricular function.This study was supported in part by a grant from the Consiglio Nazionale delle Ricerche, Italy     

Effects of norepinephrine on right ventricular function in septic shock patients

Objective To study the effects of norepinephrine on right ventricular function in patients with hyperdynamic septic shock.Design Prospective, open study.Setting A 15 bed ICU in a university hospital.Patients 9 patients with hyperdynamic septic shock (SBP<90 mmHg, Cl4l·min^–1·m^–2, SVRI850 dynes·s·cm^–5m^–2 and oliguria).Interventions Plasma volume expansion was used to correct a suspected volume deficit and then, norepinephrine infusion was started and titrated to restore systemic blood pressure to the normal range (mean infusion rate: 1.1±0.2 mcg·kg^–1·min^–1). Norepinephrine was the only vasoactive agent used in these patients.Measurements and results A modified Swan-Ganz catheter mounted with a fast response thermistor was inserted in each patient, allowing repeated measurements of RVEDVI and RVEF. At time of inclusion to the study, all but one patient had elevated MPAP (23±4 mmHg) and RVEF50%, and all patients had RVEDVI90 ml·m^–2. During norepinephrine infusion, MAP increased from 51±9 to 89±10 mmHg (p<0.0001), PVRI increased from 204±35 to 286±63 dynes·s·cm^–5·m^–2 (p<0.05), and despite this increase in right ventricular afterload, no detrimental effect in RVEF (36±11 to 36±10%) or in RVEDVI (116±30 to 127±40 ml·m^–2) was observed. A Frank-Starling relationship for the right ventricle was constructed by plotting an index of ventricular performance (RVSWI) against an index of ventricular preload (RVEDVI). A significant upward shift to the right of the relationship was observed during norepinephrine infusion.Conclusion It was concluded that norepinephrine exerted a favourable effect on right ventricular function.Work done at Sainte Marguerite Hospital, Marseille, France     

High-dose intravenous magnesium sulfate in the management of life-threatening status asthmaticus

In severe status asthmaticus basic medical treatment often fails to improve the patient's condition. Mechanical ventilation in this situation is associated with a high incidence of serious complications. After the bronchodilating effect of moderate-dose magnesium sulfate in asthmatic patients had been demonstrated in previous studies we treated five mechanically ventilated patients with refractory status asthmaticus successfully with high dosages of MgSO₄ IV (10–20 g within 1 h depending on the bronchodilating effect). MgSO₄ resulted in a significant decrease of peak airway pressure (43.0±6.8 to 32.0±8.0 cmH₂O) and inspiratory flow resistance (22.7±7.0 to 11.9±6.0 cmH₂O·l^–1·s^–1) within 1 h. The resulting serum magnesium levels after one hour were up to threefold of the normal serum levels. Although a main-tainance dose of 0.4 g/h had been administered continuously during the following 24 h serum magnesium decreased towards normal values within this time. The only relevant side-effect was a mild to moderate arterial hypotension in two of the five patients during the high dose administration period of MgSO₄ which responded readily to dopamine treatment.     

Right ventricular ejection fraction measurement in moderate acute respiratory failure (ARF). Effects of PEEP

Eight patients mechanically ventilated for acute respiratory failure were submitted to increasing levels of PEEP, from 0 to 15 cm H₂O. Right ventricular ejection fraction (RVEF) and end-diastolic volume index (RVEDVI) were measured using the fast response thermistor Swan-Ganz catheter. PEEP induced a linear decrease of cardiac index, while the pulmonary artery pressure increased. In three patients (group A) with a RVEDVI larger than 120 ml at ZEEP, RVEF decreased and RVEDVI increased with PEEP. In the other five patients (RVEDVI>120 ml, group B), RVEF was unchanged and RVEDVI decreased at PEEP 15 cm H₂O. This study suggest that RV changes induced by PEEP are probably a function of the initial RVEF and RVEDVI.     

Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated patients with chronic obstructive pulmonary disease

Objective To evaluate the impact of helium-oxygen (He/O₂) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support.Design and setting Prospective crossover interventional study in the medical ICU of a university hospital.Patients and participants Ten patients.Interventions Sequential inhalation (30 min each) of three gas mixtures: (a) air/O₂, (b) He/O₂ (c) air/O₂, at constant FIO₂ and level of pressure support.Measurements and results Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO₂ were 14±3 cmH₂O and 0.33±0.07 respectively. Compared to Air/O₂, He/O₂ reduced the number of ineffective breaths (4±5 vs. 9±5 breaths/min), intrinsic PEEP (3.1±2 vs. 4.8±2 cmH₂O), the magnitude of negative esophageal pressure swings (6.7±2 vs. 9.1±4.9 cmH₂O), pressure-time product (42±37 vs. 67±65 cmH₂O s^–1 min^–1), and total WOB (11±3 vs. 18±10 J/min). Elastic (6±1 vs. 10±6 J/min) and resistive (5±1 vs. 9±4 J/min) components of the WOB were decreased by He/O₂.Conclusions In intubated COPD patients ventilated with pressure support He/O₂ reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O₂ could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weaning.Funding was provided by the Swiss National Scientific Research Fund (grant #32-63501.00)     

Splanchnic oxygen transport after cardiac surgery: evidence for inadequate tissue perfusion after stabilization of hemodynamics

Objective To evaluate the adequacy of visceral oxygen transport and gastric pH_i after open heart surgery in patients with stable hemodynamics.Design Nonrandomized control trial.Setting A general intensive care unit in a tertiary care center.Patients Sixteen postoperative cardiac surgery patients were studied after stabilization of systemic hemodynamics.Interventions The effect of dobutamine infusion (6 g kg^–1 min^–1) on systemic and regional oxygen transport was studied in ten patients, with six patients serving as controls. Systemic oxygen consumption was measured by indirect calorimetry and splanchnic and femoral blood flow, by continuous infusion of indocyanine green using regional catheters and gastric mucosal pH_i by gastric tonometer.Measurements and results Gastric mucosal acidosis was observed in half of the patients. Dobutamine increased cardiac output (3.2±0.6 vs 4.4±0.7l· min^–1·m^–2;P<0.05), splanchnic blood flow (0.68±0.28 vs 0.91±0.281· min^–1·m^–2;p<0.05) and femoral blood flow (0.25±0.08 vs 0.32±0.11l·min^–1·m^–2;p<0.05). Changes in splanchnic oxygen delivery and consumption were parallel in the two study groups. In response to dobutamine, gastric pH_i did not change (7.30±0.08 vs 7.31±0.06; NS), while in the control group, gastric pH_i tended to decrease (7.32±0.04 vs 7.28±0.06; NS). Systemic oxygen consumption increased in response to dobutamine (141±11 vs 149±11 ml· min^–1·m^–2;P<0.05) but did not change in the control group.Conclusions We conclude that a mismatch between splanchnic oxygen delivery and demand may be present despite stabilization of systemic hemodynamics after cardiac surgery. This is suggested by the parallel changes in splanchnic oxygen delivery and consumption. Dobutamine is likely to improve splanchnic tissue perfusion at this phase.This study was supported in part by the senior researcher's grant no. 1945/3015/92 to Dr. Takala from the Academy of Finland     

Angiocardiographic Pressure Volume Loops in the Analysis of Right Ventricular Function after Repair of Tetralogy of Fallot

Objective: The objective of the study was to estimate the capacity of pressure volume (PV) loop analysis to assess right ventricular (RV) function after Fallot (TOF) repair.Patients: Fifty six patients were examined after TOF repair. PV loops were constructed from RV angiocardiography and simultaneous pressure measurement. Patients were divided in three groups according to RV size and pressure (Group I: normal RV size and pressure; group II: enlarged RV, near normal pressure; group III: normal RV size, elevated pressure).Main outcome measures: Systolic stroke work corrected for body surface area (W/BSA) and for RV enddiastolic volume (W/EDV), peak RV filling (PFR) and emptying rates (PER) corrected for RV stroke volume, cycle efficiency (CE), RV ejection fraction (RVEF).Results: W/BSA was significantly higher in group II than in group I (0.19 ± 0.05 vs. 0.11 ± 0.04 J/m², p < 0.001) and was similar between groups II and III (0.19 ± 0.05 vs. 0.17 ± 0.05 J/m² ; NS). W/EDV was similar in groups I and II (12.4 ± 5.4 vs. 12.4 ± 2.9 mmHg; NS). CE was smallest in group II. The difference was significant between groups II and III (0.62 ± 0.08 vs. 0.73 ± 0.09; p < 0.05). RVEF was negatively correlated to RV end systolic volume (RVESV) in the patients of groups I and II (r = −0.32, p < 0.05). A similar correlation was found between PFR and RVESV (r = −0.28, p < 0.05).Conclusions: Analysis of a single PV loop allows quantification of RV load after TOF repair. W/BSA is increased to the same extent under volume and pressure load. The lack of decrease in W/EDV in patients with enlarged RV indicates that RV is capable to perform adequate work in a wide range. RVESV is a useful measure for estimating RV function after TOF repair depicting parameters of systolic and diastolic RV function.     

Monitoring of right ventricular function using a conventional slow response thermistor catheter

Objective To investigate whether determination of right ventricular end-diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF) can be performed with reasonable accuracy and reproducibility using a conventional slow response thermistor pulmonary artery catheter (CPAC) applying an adaptive algorithm.Design To study RVEDV and RVEF simultaneously with pulmonary artery catheters equipped with slow and fast response thermistors (FRPAC) under a broad range of cardiac output.Setting Laboratory of Institute of Experimental Surgery, Technical University.Animals 11 anaesthetised piglets.Interventions Hypovolemia (V–) was induced by withdrawal of blood up to 50 ml/kg, hypervolemia (V+) was produced by retransfusing blood and adding up to 30 ml/kg hydroxyethyl starch. In 5 animals in phases V–and V+ beta-adrenergic stimulation was achieved with dobutamine. Finally pulmonary artery hypertension was induced by infusion of small air bubbles.Measurements and results Cardiac output (CO), RVEDV and RVEF were determined simultaneously with FRPAC and CPAC placed in the same pulmonary artery branch. Measurements were repeated 8 times sequentially in steady state normovolemia. A total of 130 measurements could be analysed. The coefficient of variation was 6.7±4.2 for CO_(FRPAC) and 4.6±1.7% for CO_(CPAC); for RVEF it was 9.7±6.2% (FRPAC) and 9.9±3.9% (CPAC); for RVEDV it was 11.6±4.8% (FRPAC) and 8.54±3.2 (CPAC). Mean difference (bias) was 0.06±0.39 l/min for CO measured with both methods, 19±35 ml for RVEDV and –3.3±6.5% for RVEF. CO_(CPAC) displayed a strong correlation to CO_(FRPAC) (R=0.97,p=0.001) as well as RVEF (R for RVEF_(CPAC) versus RVEF_(FRPAC)=0.90,p=0.001). R for RVEDV_(CPAC) versus RVEDV_(FRPAC) was 0.67,p=0.001. We conclude that this animal study demonstrates good agreement between RVEF and RVEDV obtained with catheters equipped with a fast response thermistor or with a conventional slow response thermistor allowing accurate monitoring of right ventricular function with a conventional pulmonary artery catheter.Supported in part by grants from BMFT (grant number 0706908)     

Continuous positive pressure breathing without and with inspiratory pressure support in acute respiratory failure when mean airway pressure is constant

Objective: Mean airway pressure (Paw_m) may be a major factor for PaO₂, functional residual capacity, and cardiac output in acute respiratory failure (ARF). To clarify effects of inspiratory pressure support (IPS) as a ventilatory mode in ARF, we studied patients in ARF either using IPS or continuous positive pressure breathing (CPAP) at the same level of Paw_m, measuring respiratory and circulatory parameters.,Methods: After consent, 10 patients in ARF of moderate severity (PaO₂:FiO₂ 205±108 at positive end expiratory pressure (PEEP) 8.7±3.1cmH₂O; mean ±SD) were investigated. Measurements were on day 7.4±8.4 after onset of ARF. IPS was 13.5±3.9cmH₂O above PEEP. To result in constant Paw_m, PEEP was reduced for IPS (Paw_m IPS 11.1±3.6vs. Paw_m CPAP 9.9±3.3cmH₂O,ns; PEEP IPS 8.7±3.1vs. PEEP CPAP 10.6±4.3cmH₂O,p=0.04). Inspired concentration of oxygen (FiO₂) and the ventilator (Siemens 900C) were not changed for the individual patient.Results: For IPS, tidal volume (VT) increased by +31% and respiratory frequency (RF) decreased by –19% (VT IPS 608±179vs. VT CPAP 465±141ml,p=0.01; RF IPS 21.6±7.6vs. RF CPAP 26.7±8.3 breaths per minute,p=0.02). Also, PaCO₂ showed a tendency to be lower for IPS, not reaching significance (PaCO₂ IPS 44.3±5vs. PaCO₂ CPAP 47.4±4.9mmHg,p=0.1). All other parameters were unchanged (expiratory minute volume, PaO₂, pH, intravascular pressures, cardiac index, stroke volume index (n=6), systemic and pulmonary vascular resistances, venous admixture, deadspace (n=3) oxygen consumption and oxygen delivery).We conclude: When Paw_m remained constant, IPS added to CPAP improved VT and RF without improving oxygenation or deteriorating circulation in patients with ARF of moderate severity. IPS mainly supports the ability to breathe spontaneously in ARF.Presented in part at Zentraleuropäischer Anaesthesie-Kongress, Munich, 14–19 September 1987     

Right ventricular function in COPD patients during weaning from mechanical ventilation

We studied the right ventricular function during a successful weaning period in 7 COPD patients without LV disease who had been mechanically ventilated for several days after an acute exacerbation of their disease. A Swan-Ganz ejection fraction thermodilution catheter performed measurements of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume index (RVEDVI) before and fifteen minutes after disconnection from the ventilator at the maintenance FiO₂. Although pulmonary artery pressure (PAP) rose from 25±4 to 28.5±4.5 mmHg after disconnection from the ventilator, RVEF (0.36±0.56 to 0.35±0.12) and RVEDVI (117±51 to 126±52 ml/m²) remained similar in both conditions. We concluded that right ventricular systolic function assessed with modified pulmonary artery catheter was maintained during the weaning phase in such weanable patients. This method could easily detect any fall of RVEF or diastolic RV enlargement able to impair the weaning in some patients.     

Incidence and prognostic value of right ventricular failure in acute respiratory distress syndrome

Objective  To analyse the incidence and the impact on outcome of right ventricular failure (RVF) in patients with acute respiratory distress syndrome (ARDS). Patients and methods  A total of 145 ARDS patients included in the previously published French Pulmonary Artery Catheter (PAC) study were randomly assigned to receive a PAC. All patients were ventilated according to a strategy aimed at limiting plateau pressure. The RVF was defined by the concomitant presence of: (1) a mean pulmonary artery pressure (MPAP) > 25 mmHg, (2) a central venous pressure (CVP) higher than pulmonary artery occlusion pressure (PAOP) and (3) a stroke volume index < 30 mL m⁻². Results  Right ventricular failure was present in 9.6% of patients. Mortality was 68% at day-90 with no difference between patients with RVF (RVF+) and without RVF (71 vs. 67%, respectively). SAPS II, PaO₂/FiO₂ and PaCO₂ were similar in both groups. Tidal volume and I/E ratio were significantly higher in RVF+ (9.7 ± 2.8 vs. 8.6 ± 1.8 ml m⁻² and 0.7 ± 0.5 vs. 0.5 ± 0.2). Plateau pressure tended to be higher in RVF+ (28 ± 6 vs. 25 ± 6 cmH₂O, NS). In multivariate analysis, PaO₂/FiO₂, mean arterial pressure, arterial pH, SvO₂, MPAP and presence of CVP > PAOP, but not RVF, were independently associated with day-90 mortality. Conclusion  In this group of patients investigated early in the course of ARDS and ventilated according to a strategy aimed at limiting plateau pressure, the presence of RVF was about 10%. Unlike MPAP and the presence of CVP > PAOP, RVF at this early stage did not appear as an independent factor of mortality. This article is discussed in the editorial available at: doi:.     

Comparative effects of helium-oxygen and external positive end-expiratory pressure on respiratory mechanics,gas exchange,and ventilation-perfusion relationships in mechanically ventilated patients with chronic obstructive pulmonary disease

Objective To compare the effects of He/O₂ and external PEEP (PEEPe) on intrinsic PEEP (PEEPi), respiratory mechanics, gas exchange, and ventilation/perfusion (_A/) in mechanically ventilated COPD patients.Design and setting Prospective, interventional study in the intensive care unit of a university hospital.Interventions Ten intubated, sedated, paralyzed, mechanically ventilated COPD patients studied in the following conditions: (a) baseline settings made by clinician in charge, air/O₂, ZEEP; (b) He/O₂, ZEEP; (c) air/O₂, ZEEP; (d) air/O₂, PEEPe 80% of PEEPi. Measurements at each condition included _A/ by the multiple inert gas elimination technique (MIGET).Results PEEPi and trapped gas volume were comparably reduced by He/O₂ (4.2±4 vs. 7.7±4 cmH₂O and 98±82 vs. 217±124 ml, respectively) and PEEPe (4.4±1.3 vs. 7.8±3.6 cmH₂O and 120±107 vs. 216±115 ml, respectively). He/O₂ reduced inspiratory and expiratory respiratory system resistance (15.5±4.4 vs. 20.7±6.9 and 19±9 vs. 28.8±15 cmH₂O l^–1s^–1, respectively) and plateau pressure (13±4 vs. 17±6 cmH₂O). PEEPe increased airway pressures, including total PEEP, and elastance. PaO₂/FIO₂ was slightly reduced by He/O₂ (225±83 vs. 245±82) without significant _A/ change.Conclusions He/O₂ and PEEPe comparably reduced PEEPi and trapped gas volume. However, He/O₂ decreased airway resistance and intrathoracic pressures, at a small cost in arterial oxygenation. He/O₂ could offer an attractive option in COPD patients with PEEPi/dynamic hyperinflation.     

连续右心容量监测指导感染性休克的液体复苏

目的 比较以右房压(right atria pressure,RAP)和右室舒张末期容积指数(risht ventricular end-diastolic volume index,RVEDVI)指导老年感染性休克患者液体复苏的效果.方法前瞻性、随机、对照临床研究.入选2007年1月至2008年10月入住浙江医院重症加强治疗病房,低血压发生时间<6 h的老年感染性休克患者30例,应用改良的容量性肺动脉导管连续同步监测容量和压力的变化,指导液体复苏.随机分为对照组和实验组,对照组的治疗目标为RAP 8～12 mmHg,实验组的治疗目标为右室射血分数(right ventricular ejection fraction,RVEF)校正的RVEDVI达到100～200 mL/m~2.记录液体复苏治疗前后两组患者RAP、肺动脉嵌顿压(pulmonary artery occlusion pressure,PAOP)、RVEF、RVEDVI等参数;记录治疗前后两组患者急性牛理和慢性健康评分(acute physiology and chronic health e-valuation Ⅱ,APACHE Ⅱ)和混合静脉血氧饱和度(mixed venous oxygen saturation,SvO_2)的变化;记录治疗前两组患者动脉血乳酸浓度及治疗后6 h乳酸清除率;并将液体复苏治疗后6 h RVEDVI差值与乳酸清除率作相关分析.结果 对照组液体复苏15例达标12例,达标率为80%,实验组液体复苏15例达标13例,达标率为86.7%,两组差异无统计学意义(P>0.05).液体复苏达标患者中,实验组与对照组相比,RVEDVI、RVEDVl差值、RVEF(%)、RAP和6 h乳酸清除率(%)明显增高[(119.92±15.65)mL/m~2,(38.54±6.63)mL/m~2,(36.08±3.40),(14.46±1.13)mmHg,(58.31±13.36)vs.(99.92±11.71)mL/m~2,(21.00±11.01)mL/m~2,(32.42±2.47),(13.08±1.08)mmHg,(43.99±16.26);P<0.05],但PAOP、APACHE Ⅱ和SvO~2差异无统计学意义(P>0.05).液体复苏治疗6 h后两组患者RVEDVI差值与乳酸清除率显著相关(P<0.01).结论以RVEDVI指导老年感染性休克患者液体复苏与传统的以RAP为指导的液体复苏相比,复苏过程更安全,对乳酸清除率的改善更为满意,可能更好地改善全身组织灌注与氧合.     

Prognostic value of cardiovascular magnetic resonance derived right ventricular function in patients with interstitial lung disease

Background

Cardiovascular magnetic resonance (CMR) provides non-invasive and more accurate assessment of right ventricular (RV) function in comparison to echocardiography. Recent study demonstrated that assessment of RV function by echocardiography was an independent predictor for mortality in patients with interstitial lung disease (ILD). The purpose of this study was to determine the prognostic significance of CMR derived RV ejection fraction (RVEF) in ILD patients.

Methods

We enrolled 76 patients with ILD and 24 controls in the current study. By using 1.5 T CMR scanner equipped with 32 channel cardiac coils, we performed steady-state free precession cine CMR to assess the RVEF. RV systolic dysfunction (RVSD) was defined as RVEF ≤45.0% calculated by long axis slices. Pulmonary hypertension (PH) was defined as mean pulmonary artery pressure (mPAP) of more than 25 mmHg at rest in the setting of pulmonary capillary wedge pressure ≤15 mmHg.

Results

The median RVEF was 59.2% in controls (n = 24), 53.8% in ILD patients without PH (n = 42) and 43.1% in ILD patients with PH (n = 13) (p < 0.001 by one-way ANOVA). During a mean follow-up of 386 days, 18 patients with RVSD had 11 severe events (3 deaths, 3 right heart failure, 3 exacerbation of dyspnea requiring oxygen, 2 pneumonia requiring hospitalization). In contrast, only 2 exacerbation of dyspnea requiring oxygen were observed in 58 patients without RVSD. Multivariate Cox regression analysis showed that RVEF independently predicted future events, after adjusting for age, sex and RVFAC by echocardiography (hazard ratio: 0.889, 95% confidence interval: 0.809 – 0.976, p = 0.014).

Conclusions

The current study demonstrated that RVSD in ILD patients can be clearly detected by cine CMR. Importantly, low prevalence of PH (17%) indicated that population included many mild ILD patients. CMR derived RVEF might be useful for the risk stratification and clinical management of ILD patients.     

Acute hemodynamic changes during lung recruitment in lavage and endotoxin-induced ALI

Objective To assess acute cardiorespiratory effects of recruitment manoeuvres in experimental acute lung injury.Design Experimental study in animal models of acute lung injury.Setting Experimental laboratory at a University Medical Centre.Animals Ten pigs with bronchoalveolar lavage and eight pigs with endotoxin-induced ALI.Interventions Two kinds of recruitment manoeuvres during 1 min; a) vital capacity manoeuvres (ViCM) consisting in a sustained inflation at 30 cmH₂O and 40 cmH₂O; b) manoeuvres obtained during ongoing pressure-controlled ventilation (PCRM) with peak airway pressure 30 cmH₂O, positive end-expiratory pressure (PEEP) 15 and peak airway pressure 40, PEEP 20. Recruitment manoeuvres were repeated after volume expansion (dextran 8 ml/kg). Oxygenation, mean arterial, and pulmonary artery pressures, aortic, mesenteric, and renal blood flow were monitored.Measurements and results Lower pressure recruitment manoeuvres (ViCM30 and PCRM30/15) did not significantly improve oxygenation. With ViCM and PCRM at peak airway pressure 40 cmH₂O, PaO₂ increased to similar levels in both lavage and endotoxin groups. Aortic blood flow was reduced from baseline during PCRM40/20 and ViCM40 by 57±3% and 61±6% in the lavage group and by 57±8% and 82±7% (P<0.05 vs PCRM40/20) in endotoxin group. The decrease in blood pressure was less pronounced. Prior volume expansion attenuated circulatory impairment. After cessation of recruitment hemodynamic parameters were restored within 3 min.Conclusion Effective recruitment resulted in systemic hypotension, pulmonary hypertension, and decrease in aortic blood flow especially in endotoxinemic animals. Circulatory depression may be attenuated using recruitment manoeuvres during ongoing pressure-controlled ventilation and by prior volume expansion.