The effect of positive pressure airway support on mortality and the need for intubation in cardiogenic pulmonary edema: a systematic review

OBJECTIVE: To critically appraise and summarize the trials examining the addition of continuous positive airway pressure (CPAP) or noninvasive positive pressure ventilation (NPPV) to standard therapy on hospital mortality, need for endotracheal intubation, and predischarge left ventricular function in patients admitted to the hospital with cardiogenic pulmonary edema with gas exchange abnormalities. DATA SOURCES: We searched MEDLINE (1983 to June 1997) and bibliographies of all selected articles and review articles. We also reviewed the abstracts from the proceedings of relevant meetings from 1985 to 1997. STUDY SELECTION: (1) Population: patients presenting to hospital with cardiogenic pulmonary edema; (2) intervention: one of the following three: (a) the use of CPAP and standard medical therapy vs standard medical therapy alone; (b) the use of NPPV and standard medical therapy vs standard medical therapy alone; and (c) the use of NPPV and standard therapy vs CPAP and standard therapy; (3) outcome: hospital survival, need for endotracheal intubation, or predischarge left ventricular dysfunction; and (4) study design: randomized controlled trial (RCT); if there were fewer than two RCTs, other study designs were included. DATA EXTRACTION: Two authors independently extracted data and evaluated the methodologic quality of the studies. DATA SYNTHESIS: CPAP was associated with a decrease in need for intubation (risk difference, -26%, 95% confidence intervals, -13 to -38%) and a trend to a decrease in hospital mortality (risk difference, -6.6%; +3 to -16%) compared with standard therapy alone. There was insufficient evidence to comment on the effectiveness of NPPV either compared with standard therapy or CPAP and standard therapy. Evidence was also lacking on the potential for either intervention to cause harm. CONCLUSIONS: A modest amount of favorable experimental evidence exists to support the use of CPAP in patients with cardiogenic pulmonary edema. CPAP appears to decrease intubation rates and data suggest a trend toward a decrease in mortality, although the potential for harm has not been excluded. The role of NPPV in this setting requires further study before it can be widely recommended.     

Assessment of cardiac filling pressure during continuous positive pressure ventilation

Before and after 10 dogs were near-drowned with fresh water, cardiac filling pressures were measured during spontaneous respiration, controlled mechanical ventilation with ambient expiratory airway pressure, continuous positive-pressure ventilation (CPPV) with 20 ml H2O PEEP, and CPPV alone. Pulmonary arterial occlusion and left ventricular end diastolic pressures were measured and compared. Intrapleural pressure was subtracted from values for each of these pressures to calculate respective transmural filling pressures. Mechanical ventilation and CPPV each decreased thoracic venous return, but only CPPV increased pulmonary arteriolar resistance. The increase of both airway pressure and pulmonary arteriolar resistance, in turn, increased both right atrial and pulmonary arterial occlusion pressures, but decreased left ventricular filling. Thus, measurement of pulmonary arterial occlusion pressure alone did not allow accurate assessment of cardiac filling pressure. The authors found that measurement of intrapleural pressure was necessary to obtain an accurate reflection of left ventricular filling pressure during CPPV. Momentary interruption of CPPV to measure any pressure was of no value in assessing vascular filling and caused pulmonary edema in several animals. Therefore, the authors recommend that vascular pressures be measured and evaluated without interruption of positive airway pressure.     

The use of noninvasive positive pressure ventilation in the emergency department: results of a randomized clinical trial

OBJECTIVE: To determine whether the use of noninvasive positive pressure ventilation (NPPV) in the emergency department (ED) will reduce the need for tracheal intubation and mechanical ventilation. DESIGN: Randomized, controlled, prospective clinical trial. SETTING: ED of Barnes-Jewish Hospital, a university-affiliated teaching hospital. PATIENTS: Twenty-seven patients meeting a predetermined definition of acute respiratory distress requiring hospital admission. INTERVENTIONS: Conventional medical therapy for the various etiologies of acute respiratory distress and the application of NPPV. MEASUREMENTS AND RESULTS: The primary outcome measure was the need for tracheal intubation and mechanical ventilation. Secondary outcomes also assessed included hospital mortality, hospital length of stay, acquired organ system derangements, and the utilization of respiratory care personnel. Sixteen patients (59.3%) were randomly assigned to receive conventional medical therapy plus NPPV, and 11 patients (40.7%) were randomly assigned to receive conventional medical therapy without NPPV. The two groups were similar at the time of randomization in the ED with regard to demographic characteristics, hospital admission diagnoses, and severity of illness. Tracheal intubation and mechanical ventilation was required in seven patients (43.8%) receiving conventional medical therapy plus NPPV and in five patients (45.5%) receiving conventional medical therapy alone (relative risk=0.96; 95% confidence interval=0.41 to 2.26; p=0.930). There was a trend towards a greater hospital mortality rate among patients in the NPPV group (25%) compared to patients in the conventional medical therapy group (0.0%) (p=0.123). Among patients who subsequently required mechanical ventilation, those in the NPPV group had a longer time interval from ED arrival to the start of mechanical ventilation compared to patients in the conventional medical therapy group (26.0+/-27.0 h vs 4.8+/-6.9 h; p=0.055). CONCLUSIONS: We conclude that the application of NPPV in the ED may delay tracheal intubation and the initiation of mechanical ventilation in some patients with acute respiratory distress. We also demonstrated that the application of NPPV was associated with an increased hospital mortality rate. Based on these preliminary observations, larger clinical investigations are required to determine if adverse patient outcomes can be attributed to the early application of NPPV in the ED. Additionally, improved patient selection criteria for the optimal administration of NPPV in the ED need to be developed.     

High-frequency jet ventilation during the treatment of acute fulminant pulmonary edema

High-frequency jet ventilation (HFJV) was used during the treatment of fulminant pulmonary edema in a 45-year-old man so that toxic levels of oxygen could be avoided when conventional methods of ventilation in combination with high levels of PEEP (20 cm H2O) were unsuccessful in raising PaO2. On each of four occasions, HFJV resulted in improved arterial oxygenation when compared with conventional modes.     

PEEP and low tidal volume ventilation reduce lung water in porcine pulmonary edema

Gonococci producing a distinct opacity protein (OpaA in strain MS11) adhere to and are efficiently internalized by cultured epithelial cells such as the Chang conjunctiva cell line. Both adherence and uptake require interactions between OpaA and heparan sulfate proteoglycans on the mammalian cell surface. Chinese hamster ovary (CHO) cells also support adherence of gonococci through interactions of OpaA with cell surface heparan sulfate proteoglycans. However, despite this similarity in the requirements for adherence, CHO cells are not capable of internalizing gonococci. In this report, we characterized this apparent deficiency and identified a factor in fetal calf serum (FCS) which is capable of mediating uptake of gonococci by CHO cells. In the absence of FCS, OpaA+ gonococci adhered to but were not internalized by CHO cells, whereas in the presence of up to 15% FCS, the bacteria were efficiently internalized by the cells. Preincubation of bacteria, but not cells, with FCS also stimulated internalization, suggesting that a factor present in FCS was binding to the surface of gonococci and subsequently stimulating entry. Using a combination of chromatographic purification procedures, we identified the adhesive glycoprotein vitronectin as the serum factor which mediates the internalization of gonococci by CHO cells. Vitronectin-depleted serum did not support gonococcal entry, and this deficiency was restored by the addition of purified vitronectin. Further experiments using a set of gonococcal recombinants, each expressing a single member of the family of Opa outer membrane proteins, demonstrated that vitronectin bound to the surface of OpaA-producing gonococci only and that the vitronectin-mediated uptake by the CHO cells was limited to this bacterial phenotype. To our knowledge, our data are the first example that vitronectin can serve as a molecule that drives bacterial entry into epithelial cells.     

Isotope study of the effects of a nitrate derivative on pulmonary blood volume. Application in the treatment of cardiogenic pulmonary edema

Isotopic study of pulmonary and ventricular blood volumes after the ingestion of 5 mg of isosorbide dinitrate showed that cardio-pulmonary blood volume decreased by 380 ml without any change in total circulating blood volume. The demonstration of this effective "internal venesection" explains the fall in capillary pressure seen after the administration of nitrate derivatives. It justifies their use in the treatment of acute pulmonary oedema or refractory cardiac failure and explains the results observed.     

Comparison of oxygen cost of breathing with pressure-support ventilation and biphasic intermittent positive airway pressure ventilation

OBJECTIVE: To assess the oxygen cost of breathing with either pressure-support ventilation (PSV) or biphasic intermittent positive airway pressure ventilation (BIPAP). DESIGN: Prospective, randomized, crossover study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Twenty clinically stable and spontaneously breathing patients after long-term mechanical ventilation. INTERVENTIONS: Patients were randomized to start on either PSV or BIPAP, and measurements were performed after an adaptation period of 30 mins. Immediately after, the ventilatory mode was changed and after another 30-min adaptation period, the same measurements were performed. MEASUREMENTS AND MAIN RESULTS: Indirect calorimetry was performed during each ventilatory mode for a period of 30 mins. Oxygen consumption, energy expenditure, CO2 production, and respiratory quotient did not differ significantly between the two ventilatory modes, regardless of the patients' randomization. There were no statistically significant differences with regard to respiratory rate, minute volume, and blood gas analysis. All patients tolerated both ventilatory modes without any signs of discomfort. CONCLUSIONS: Pressure support ventilation and BIPAP are both used for weaning patients gradually from the ventilator. BIPAP may be advantageous in patients not breathing sufficiently with PSV, since no patient effort is necessary with use of this ventilatory mode.     

Secondary pulmonary hypertension in a patient with severe chronic restrictive pulmonary insufficiency--normalized during treatment with non-invasive intranasal ventilation and oxygen

The present case report describes a young woman with severe restrictive lung failure, who developed pulmonary hypertension. She was treated successfully with nocturnal noninvasive nasal ventilation and oxygen, which removed symptoms and signs of cardiac incompensation. The improvement has persisted for five years.     

Effect of artificial ventilation on pulmonary capillary pressure in acute respiratory insufficiency

To determine the influence of intermittent positive pressure breathing (IPPB), the level of pulmonary capillary wedge pressure (PCWP) was compared during IPPB and after a short period off the respirator in 68 occasions on 42 patients with an acute respiratory failure (ARF) of various etiologies. During IPPB, the average PCWP was in the normal range in patients with toxic or neurologic comas and in cases of increased pulmonary capillary permeability edema (IPCPE), PCWP slightly increased within chronic obstructive pulmonary disease (COPD) complicated with ARF and in hemodynamic acute pulmonary edema (HAPE). During the weaning stage, PCWP decreased in the groups of coma, COPD, and IPCPE, but increased in HAPE. The weaning test demonstrates that IPPB influenced PCWP in all patients. Therefore, PCWP cannot be assumed to represent the left ventricle filling pressure. The weaning test allows differentiation of IPCPE from HAPE. In the event of over-infusion or hypovolemia, PCWP measured under IPPB can lead to misinterpretation if not followed up by a second measurement off the respirator.     

A tube in the pharynx for emergency ventilation

BACKGROUND: If the endotracheal placement of a nasal advanced tube fails, ventilation via this tube could bridge the time until a fibreoptic bronchoscope is available. This study investigates the efficiency of ventilation via a tube resting with its tip in the pharynx near the glottis. METHODS: In 20 patients respiratory data during ventilation via a pharyngeally placed tube were recorded by means of pulse oximetry, capnometry and side-stream spirometry. Results were compared with those measured previously in the same patients during conventional facemask ventilation. RESULTS: Oxygen saturation and end-tidal carbon dioxide concentration remained unchanged using ventilation via facemask (SO2 98.5 +/- 0.9%, FECO2 4.5 +/- 0.7 vol%) or pharyngeal tube (SO2 98.6 +/- 0.7%, FECO2 4.8 +/- 0.4 vol%). No significant differences were found between the two groups with regard to peak airway pressure, tidal volume leakage, compliance and resistance of the respiratory system. CONCLUSIONS: Our results suggest an effective ventilation and oxygenation via a tube placed with its tip in the pharynx. This technique may be helpful during difficult and prolonged nasal intubation.     

Non-invasive modalities of positive pressure ventilation improve the outcome of acute exacerbations in COLD patients

OBJECTIVE: 1) To compare the clinical usefulness of both non-invasive pressure support ventilation (NPSV) and non-invasive intermittent positive pressure ventilation in assist-control (A/C) mode (NIPPV) in chronic obstructive lung disease (COLD) patients with acute hypercapnic respiratory failure: 2) to compare retrospectively the usefulness of non-invasive mechanical ventilation (NMV) with standard medical therapy alone. DESIGN: Prospective randomized retrospective study. SETTING: 2 Respiratory intermediate intensive units. PATIENTS: 29 COLD patients (age: 62 +/- 8 years) with chronic respiratory failure were hospitalized in a department for rehabilitation during acute relapses of their disease. They were transferred to our intermediate intensive care unit (IICU) and submitted randomly to either NPSV (16 patients) or NIPPV (13 patients). MEASUREMENTS AND RESULTS: Blood gas analysis, dynamic flows, clinical variables, success rate, time of ventilation, side effects and subjective score of compliance to therapy. Therapy was considered successful when endotracheal intubation was avoided and patients were returned to their condition prior to exacerbation. No statistically significant difference was found between NPSV and NIPPV in success rate (NPSV 87.5%; NIPPV 77%) or in time of ventilation (NPSV: 69 +/- 49; NIPPV: 57 +/- 49 h). A better compliance to non-invasive mechanical ventilation (NMV) was found in NPSV patients than in NIPPV patients; side effects were observed less frequently in the NPSV group. Comparison of the success rate of NMV was retrospectively performed with 35 control COLD patients with chronic respiratory insufficiency who had undergone an acute relapse of their disease in the 2 years preceding the institution of the IICU and had been treated with oxygen and medical therapy alone. Patients submitted to NMV showed a greater success rate than control (82 versus 54%) after a period of ventilation ranging from 4-216 h. CONCLUSION: Non-invasive mechanical ventilation performed either by NPSV or NIPPV may improve the outcome of acute exacerbations of COLD, as compared to medical therapy alone. NPSV seems to be more acceptable to patients in comparison with NIPPV.     

Massive pulmonary edema in a habitual crack cocaine smoker not chemically positive for cocaine at the time of surgery

OBJECTIVE: Epicardial pacing wires retained in patients who undergo cardiac surgery are thought to be a relative contraindication to MR imaging. However, to our knowledge no published evidence supports this belief. Because other metallic materials retained after cardiac surgery might represent a hazard to patients who undergo MR imaging, we sought to determine the safety of such imaging. SUBJECTS AND METHODS: We examined 200 patients who underwent MR imaging at 1 or 1.5 T after cardiac surgery. Eighty-one were examined with ECG monitoring. The presence of temporary epicardial pacing wires, prosthetic valves, and other metal materials was confirmed by chest radiography. RESULTS: Of the 200 patients reviewed, all had postoperative metallic material visible on chest radiographs. Temporary epicardial pacing wire, cut short at the skin, was seen in 51 patients. Of the 81 patients examined with ECG monitoring, we found that MR imaging produced no changes from baseline ECG rhythms. None of the 200 patients reported symptoms suggesting arrhythmia or other cardiac dysfunction during MR imaging. CONCLUSION: MR imaging can be performed safely in patients who have undergone cardiac surgery and have retained metallic material, including valve replacements and temporary epicardial pacing wires cut short at the skin. MR imaging of patients with pacemakers was not evaluated, and we recommend that pacemakers remain a contraindication to MR imaging.     

Volume-controlled versus biphasic positive airway pressure ventilation in leukopenic patients with severe respiratory failure

OBJECTIVE: To study comparatively the effects of volume-controlled vs. biphasic positive airway pressure mechanical ventilation on respiratory mechanics and oxygenation in leukopenic patients with severe respiratory failure. DESIGN: Prospective, comparative study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Leukopenic (<1000 leukocytes/microliter) patients (n=20) after cytoreductive chemotherapy requiring mechanical ventilation for severe respiratory failure (Murray score of > 2.5). INTERVENTION: Patients were assigned in a consecutive, alternating manner to receive either volume-controlled or biphasic positive airway pressure mechanical ventilation, starting within 12 to 24 hrs after endotracheal intubation. MEASUREMENTS AND MAIN RESULTS: Tidal volume, inspiratory flow, peak inspiratory and positive end-expiratory pressures, FIO2, and arterial blood gas analyses were recorded hourly for a study period of 48 hrs. Biphasic positive airway pressure ventilation was associated with a significant reduction in peak inspiratory pressure (mean differences at 24, 36, and 48 hrs: 4.4, 3.4, and 4.2 cm H2O; p = .024, .019, and .013, respectively) and positive end-expiratory pressures (mean differences at 24, 36, and 48 hrs: 1.6, 1.4, and 1.5 cm H20; p = .023, .024, and .023, respectively) at significantly lower FIO2 (mean differences at 12, 24, 36, and 48 hrs; p = .007, .015, .016, and .011, respectively). PaO2/FIO2 ratios and CO2 removal were similar under ventilatory conditions. CONCLUSIONS: Biphasic positive airway pressure ventilation offers the advantage of significantly reduced peak inspiratory and positive end-expiratory pressures at a lower FIO2 and with at least similar oxygenation and CO2 removal as achieved by volume-controlled mechanical ventilation. Our results are in line with previous reports on nonleukopenic patients and suggest that the positive effects of pressure-limited mechanical ventilation are independent of circulating white blood cells. Further studies are mandatory to demonstrate clinical benefit in this critically ill patient population.     

Comparison of noninvasive positive pressure ventilation with standard medical therapy in hypercapnic acute respiratory failure

STUDY OBJECTIVE: To compare the efficacy of standard medical therapy (ST) and noninvasive mechanical ventilation additional to standard medical therapy in hypercapnic acute respiratory failure (HARF). DESIGN: Single center, prospective, randomized, controlled study. SETTING: Pulmonary medicine directed critical care unit in a university hospital. PATIENTS: Between March 1993 and November 1996, 30 HARF patients were randomized to receive ST or noninvasive positive pressure ventilation (NPPV) in addition to ST. INTERVENTIONS: NPPV was given with an air-cushioned face via a mechanical ventilator (Puritan Bennett 7200) with initial setting of 5 cm H2O continuous positive airway pressure and 15 cm H2O pressure support. RESULTS: At the time of randomization, patients in the ST group had (mean+/-SD) PaO2 of 54+/-13 mm Hg, PaCO2 of 67+/-11 mm Hg, pH of 7.28+/-0.02, and respiratory rate of 35.0+/-5.8 breaths/min. Patients in the NPPV group had PaO2 of 55+/-14, PaCO2 of 69+/-15, pH of 7.27+/-0.07, and respiratory rate of 34.0+/-8.1 breaths/min. With ST, there was significant improvement of only respiratory rate (p < 0.05). However, with NPPV, PaO2 (p < 0.001), PaCO2 (p < 0.001), pH (p < 0.001), and respiratory rate (p < 0.001) improved significantly compared with baseline. Six hours after randomization, pH (p < 0.01) and respiratory rate (p < 0.01) in NPPV patients were significantly better than with ST. Hospital stay for NPPV vs ST patients was, respectively, 11.7+/-3.5 and 14.6+/-4.7 days (p < 0.05). One patient in the NPPV group required invasive mechanical ventilation. The conditions of six patients in the ST group deteriorated and they were switched to NPPV; this was successful in four patients, two failures were invasively ventilated. CONCLUSION: This study suggests that early application of NPPV in HARF patients facilitates improvement, decreases need for invasive mechanical ventilation, and decreases the duration of hospitalization.     

Pressure-controlled mechanical ventilation: a simplified titration method of the extrinsic positive expiratory pressure

For the inverse problem of equivalent dipole localization, a new residual function was proposed which is based on spatio-temporal correlation of background electroencephalogram (EEG). This residual has the advantage that it allows the calculation of a confidence region for estimated dipole parameters. This method was applied to two sets of visual evoked potential (VEP) data. The localization was compared by using the volume of the confidence region. The outcome of the equivalent dipole localization was compared for three different residual functions: 1) least square; 2) based on spatial correlations in the background EEG; and 3) the proposed new function which is based on spatial and temporal correlations in the background EEG. It was found that the proposed residual function leads us to the highest accuracy and the fastest convergence in the equivalent dipole localization and that even for two-dipole localization, the present method yields more accurate solutions with less iterations than the conventional methods.