V. M. Ranieri

Right ventricular myocardial function in ARF patients. PEEP as a challenge for the right heart.

ObjectiveTo examine the hemodynamic effects of external positive end-expiratory pressure (PEEP) on right ventricular (RV) function in acute respiratory failure (ARF) patients.DesignProspective, with retrospective analysis on the basis of RV volume response to PEEP.SettingGeneral intensive care unit in a university teaching hospital.Patients20 mechanically ventilated ARF patients (mean lung injury score=2.6±0.45 SD).InterventionIncremental 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 resultsAt 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.ConclusionsPEEP 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.

Inspiratory effort and measurement of dynamic intrinsic PEEP in COPD patients: effects of ventilator triggering systems.

ObjectiveTo investigate effects of ventilator triggering systems (pressure and flow triggering: PT and FT) on measurement of dynamic intrinsic PEEP (PEEPidyn) and patient-ventilator interaction in patients with chronic obstructive pulmonary disease during weaning from mechanical ventilation.DesignProspective study.SettingMedical/surgical intensive care unit of an academic hospital.Patients and participants6 COPD patients with acute respiratory failure ready to wean.MeasurementsWe measured flow, airway opening, esophageal and gastric pressures. Minute ventilation, breathing pattern and pressure time product (PTP) of the respiratory muscles and of the diaphragm were obtained during spontaneous ventilation through a mechanical ventilator (Puritan-Bennett 7200ae). Two triggering systems, namely PT and FT, were evaluated.ResultsThe inspiratory muscles effort necessary to overcome the triggering system overestimated PEEPidyn measurement of an amount equal to 49±2 and 58±3% during respectively pressure and flow triggering. FT increased tidal volume and minute ventilation and decrease PTP/b and PTP/min of the respiratory muscles and diaphragm.ConclusionsTo correctly measure PEEPidyn, the inspiratory effort produced to overcome PEEPi and to trigger the ventilator must be discriminated. Application of flow triggering requires less effort to initiate inspiration and provide a positive end-expiratory pressure level that is able to unload the respiratory muscles by reducing PEEPi. With flow triggering higher minute ventilation are obtained in COPD patients during the weaning phase.

REEXPANSION PULMONARY EDEMA WITH ACUTE HYPOVOLEMIA

Sir: Unilateral reexpansion pulmonary edema (RPE) is a rare, but potentially lifethreatening, condition that has mainly been reported following the evacuation of a pneumothorax or pleural effusion in spontaneously breathing patients [1±3]. We describe a case of postoperative unilateral pulmonary edema, unusually associated with acute hypovolemia, that occurred following evacuation of an organized hemothorax with rapid reexpansion of a chronically collapsed lung, which was successfully treated by independent lung ventilation (ILV). A 21-year-old man underwent surgical evacuation of a left hemothorax on day 7 after thoracic trauma. The intraoperative course was stable. General anesthesia was maintained for approximately 1 h. Shortly after extubation, the patient developed marked dyspnea with arterial oxygen tension (PaO2) 70 mmHg, acute hypovolemia [systolic blood pressure (BP) < 90 mmHg, central venous pressure (CVP) 0 mmHg]. PaO2 improved to 90 mm Hg after 100% O2 was administered via bag and face-mask ventilation. A chest X-ray revealed a massive left opacity (Fig. 1). Surgical reexploration was immediately decided on. Under general anesthesia the patient was reintubated with a left-sided double-lumen tube. As soon the patient was put into a right lateral decubitus position, > 2000 ml of pulmonary fluid escaped from the lumen of the left tube. The surgical revision was negative for new bleeding and/or thoracic drain obstruction. The patients oxygenation and hemodynamic status improved as soon as the lungs were ventilated separately and fluid loss was compensated for. The patient was transferred to the intensive care department and underwent ILV. ILV was stopped after 24 h, by which time the asymmetry between the lungs was resolved. To our knowledge, this is the first case that (a) occurred postoperatively in association with acute hypovolemia and (b) was successfully treated by ILV. In the literature, no case of systemic hypotension is described. In our patient, CVP was 0 mmHg and the systolic BP < 90 mm Hg. The absence of bleeding or other sources of fluid loss, the loss of > 2000 ml of edematous fluid from the patients left lung after reintubation, and the unilateral nature of the pulmonary edema all pointed to a diagnosis of RPE. Furthermore, all three main factors related to the etiology of RPE [1±3], were present; chronic collapse, a large volume of fluid and clots evacuated from the hemothorax, and rapid reexpansion of the atelectatic lung. In the literature, most RPE cases have been treated by a high fractional inspired oxygen via face mask [1, 2] or by standard mechanical ventilation [3]. The rationale for using ILV is that asymmetrical lung damage results in differences in compliance and airway resistance between the two lungs [4, 5]. Hence, during conventional lung ventilation via a single-lumen tube, the tidal volume is mostly diverted toward the less diseased, more compliant lung that may be overventilated and at high risk of barotrauma, whereas the less compliant lung will be underventilated. Diversion of pulmonary blood flow toward the more diseased lung with increased shunt has also been demonstrated [5]. Under such conditions, ILV is thought to ensure ventilation of the diseased lung, to match the ventilatory volume to the perfusion of each lung, and to avoid hyperinflation of the healthy lung [5]. For this purpose, we used ILV in this patient and stopped it after 24 h, when compliance was equal in the two lungs. In conclusion, we believe that clinicians should be aware of the possibility that RPE may occur perioperatively and may be associated with hypovolemia. Accordingly, it should be taken into account in the differential diagnosis of a patient with unilateral lung disease, who shows dyspnea and hypotension after surgery. In this case, ILV via a double-lumen endotracheal tube resulted in successful treatment of the patient.

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

ObjectiveTo 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).DesignProspective study.SettingGeneral intensive care unit in a university teaching hospital.PatientsSeven mechanically ventilated flow-limited COPD patients (PEEPi=9.7±1.3 cmH2O, mean±SD) with acute respiratory failure.InterventionHemodynamic and respiratory mechanic data were collected at four different levels of PEEP (0-5-10-15 cmH2O).Measurements and resultsHemodynamic 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.ConclusionsIn 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.

Liver inflammation and acute respiratory distress syndrome in a patient receiving hepatitis B vaccine: a possible relationship?

Abstract We describe a patient in whom clinical evidence of liver and lung dysfunction developed after he received the second dose of recombinant hepatitis B vaccine, despite no serologic evidence of viral hepatitis. However, liver biopsy specimens demonstrated both surface antigens and core antigens, possibly indicating silent hepatitis B virus infection. A search for an infective etiology for the patient’s subsequent clinical deterioration in lung function did not yield pathogens; postmortem examination revealed evidence of immune complex-mediated organ injury in the liver, lungs, and kidneys.

Respiratory mechanics II

To determine whether i.v.NAC has beneficial effects in patients with mild-to-moderate ALI in terms of ventilatory support(VS),FIO2 requirement-,evolution of the lung injury score(LIS),development of severe lung injury(ARDS)and mortality rate,we prospectively enrolled 61 adult patients with ALI to receive either NAC 40 mg/kg/day or Placebo(PL)during 3 days.Respiratory dysfunction was assessed daily considering the need of VS,the F102 necessary to achieve a Pa02 of 70 to 80 mmHg and the evolution of 3 components of the LIS (chest X-ray,Pa02-FIO2 ratio and respiratory system compliance).Data were collected at baseline (day 0),on the first 3 days after admission to the ICU and on discharge.NAC and PL groups(32 vs 29 patients)were comparable at entry in terms of SAPS and values of the LIS.At day 0, 69% of the patients were ventilated in the NAC group versus 76% in the PL group;at day 3, 83% of the NAC treated patients did not require any further VS, versus 52% in the PL group(p=0.01).Pa02/FIO2 improved significantly(p=0.05)from day 0 to day 3 only in the NAC group.The LIS showed a signifi cant improvement(p=0.003)in the NAC treated group within the first 10 days of treatment;no change was observed in the PL group.3 patients in each group progressed to ARDS.The one-month mortality rate was 22% for the NAC and 35% for the PL group In conclusion,early treatment with NAC seems to affect favourably pulmonary gas exchange and decrease the need for prolonged VS in patients with mild-to-moderate ALI.

Respiratory mechanics I

The ARDS is a clinical entity which from a mechanical point of view is characterized not only by a low respiratory compliance but also by a high respiratory resistance (R). In five ARDS patients we analyzed the changes in total R of the respiratory system (Rmax) and airway plus endotracheal tube R (Rmin) induced by changing the airflow (V) rate at constant tidal volume (VT) and total PEEP (PEEP plus autoPEEP). Patients were ventilated in volume controlled mode (VC) and VC with inverse ratio (VCIRV), both with constant insufflation flow. Signals of V, and airway pressure (Paw) were digitized (sampling frequency 200Hz) and acquired by an IBM 55SX computer in order to perform the following calculations: Rmax, Rmin, DR (Rmax-Rmin), static compliance (C). VT was obtained by digital integration of V. Rmin was corrected for the closing time of the inspiratory valve. Statistical analysis was performed with a two-way ANOVA. Results: V PEEPt Ti/Tt VT L/e cmH20 8 reL VC .76±.06 9.5±.4 34+.5 590±42 VCIRV .30+.02 8.4+.5 73+2 610±47 P= <.001 .15 <.001 .5

Hemodynamic effects of PEEP

PP was introduced because of bilateral alveolar consolidation, severe hypoxemia despite adequate level of PEEP (12±2). PP and SP were alternatively used by 4 hours periods with constant ventilatory settings. All patients were hemodynamically monitored (Swan-Ganz catheter). Patients were mean aged 59±19 with a SAPS at 12±3 and under mechanical ventilation since 3,5±4,3 days for pneumonias. 2 evolving as ARDS (Murray score of 3,5 each). All patients improved during the first period: PaO2/FiO2=92±37 before PP (min.=56, max.=128), PaO21FiO2-153±77 at the end of PP (min.=82, max.=230). When the 4 patients were placed back on SP, there was a fall of Pa02/FiO2 resolutive when they returned to PP (208±65 to 77+±21, extreme variations 120 to 61 and 275 to 95). This PP dependency lasted 5,2±0,9 days including 67±14 h under PP before stabilisation of PaO2/FiO2 values whatever the posture was. No severe complication (haemodynamics, extubation) occurred during the procedure. The 2 patients with ARDS died.