Use of non-invasive positive pressure ventilation for cardiogenic pulmonary edema in emergency care units

The work reported by L'Her et al. in this issue of La Presse Médicale demonstrates the feasibility of applying simple intensive care techniques in situations frequently encountered in emergency care units. These authors used a face mask for continuous positive pressure ventilation in patients over 70 years of age admitted for respiratory distress related to cardiogenic pulmonary edema. In these elderly patients, the authors noted an improvement in blood gases, respiratory rate and heart rate and did not observe any secondary effect. Acute respiratory failure was cured in 90% of the cases without referral to the intensive care unit. The mechanism of action of continuous positive airway pressure, or spontaneous ventilation with positive expiratory pressure, is different from simple oxygen therapy. Two mechanisms are intimately related. The main effect is ventilatory assistance resulting from a "re-aeration" of the pulmonary parenchyma which increases compliance and reduces work required to overcome elastic retraction forces. Likewise the increased pulmonary volume reduces pulmonary resistance. Positive airway pressure also has an effect on left ventricular function. Indeed, after-load is reduced by the reduction in the large negative intrathoracic pressure swing. Lower energy expenditure required for respiration also greatly reduces total oxygen consumption and improved blood gases favor oxygen supply to the myocardium. The contraindications of continuous positive airway pressure are related to abnormal control of the upper airways and major hemodynamic disorders. Prudence is also required in case of shock due to the risk of major respiratory muscle fatigue. The question could also be raised as to the risk in elderly patients where cardiogenic pulmonary edema is often associated with a certain degree of chronic bronchitis. It is now known that these patients have an intrinsic positive expiratory pressure which considerably increases respiratory work. Symptomatic treatment in this type of disorder is mechanical and continuous positive airway pressure diminishes this work. Cardiogenic pulmonary edema in the elderly is thus an excellent indication for spontaneous ventilation with positive expiratory pressure. Improvement in these simple techniques, their widespread use and a better understanding of their limitations remain important challenges for the future.     

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.     

Small airway closure and positive end-expiratory pressure in mechanically ventilated patients with chronic obstructive pulmonary disease

The effects of positive end-expiratory pressure (PEEP) on alveolar recruitment and closing volume were studied in ten supine, sedated, and paralyzed patients with chronic obstructive respiratory disease and acute respiratory failure. We applied PEEP (0, 5, 10, and 15 cm H2O) and constructed inflation static volume-pressure (V-P) curves. In all patients, the static V-P curves obtained at different PEEP levels were superimposed on each other, indicating that with PEEP there was no recruitment of previously atelectatic lung units. However, the static V-P curves exhibited an inflection point, which should reflect the critical pressure (Po) required to reopen all closed airways, whilst the corresponding lung volume (Vo) reflects the opening volume. On average, Vo was 0.71 L above the relaxation volume of the respiratory system (Vr). All patients, however, exhibited dynamic hyperinflation, i.e., with zero PEEP (ZEEP) the end-expiratory lung volume (EELV) was 0.54 L above Vr. Nevertheless, in seven patients the EELV on ZEEP was below Vo, resulting in cyclic reopening and closure of small airways with each breathing cycle, with concomitant mechanical stresses on the peripheral airways that may lead to low-volume barotrauma. Such barotrauma may be prevented by increasing with PEEP the EELV to Vo.     

Cerebral hemodynamic changes in sleep apnea syndrome and effect of continuous positive airway pressure treatment

BACKGROUND AND OBJECTIVE: A clear association among snoring, sleep apnea, and increased risk of stroke has been shown by previous studies. However, the possible role played by sleep apnea in the pathogenesis of cerebrovascular disease is subject to debate. To evaluate the influence of hemodynamic changes caused by obstructive sleep apnea syndrome (OSAS), we investigated cerebrovascular reactivity to hypercapnia in patients with OSAS. METHODS: The study was performed at baseline and after 1 night and 1 month of nasal continuous positive airway pressure (n-CPAP) therapy, with patients in the waking state (8:00 to 8:30 AM and 5:30 to 6:00 PM) with transcranial Doppler ultrasonography. Cerebrovascular reactivity was calculated with the breath-holding index (BHI). RESULTS: In the baseline condition, compared with normal subjects, patients with OSAS showed significantly lower BHI values in both the morning (0.57 versus 1.40, p < 0.0001) and the afternoon (1.0 versus 1.51, p < 0.0001). Cerebrovascular reactivity was significantly higher in the afternoon than it was in the morning in both patients (p < 0.0001) and controls (p < 0.05). In patients, the BHI returned to normal values, comparable with those of control subjects, after both 1 night and 1 month of n-CPAP therapy. CONCLUSIONS: These findings suggest an association between OSAS and diminished cerebral vasodilator reserve. This condition may be related to the increased susceptibility to cerebral ischemia in patients with OSAS, particularly evident in the early morning.     

Nasal-continuous positive airway pressure in the treatment of near-drowning in freshwater

In patients who have experienced near-drowning, hypoxemia is the major clinical consequence. We report two cases of patients who have experienced near-drowning in freshwater who were successfully treated with nasal-continuous positive airway pressure (N-CPAP) plus oxygen therapy. Both patients presented a radiographic appearance of bilateral pulmonary edema. We suggest the use of N-CPAP as an easier and less costly alternative to tracheal intubation for treating near-drowning in patients who are breathing spontaneously and who have not experienced loss of consciousness.     

Pioneer in orotracheal intubation: Eugen Tschudy. The first emergency intubation for airway obstruction?

Presented is a case in which there was significant accumulation of In-111 Octreotide in brain infarcts. It is likely that the accumulation was nonspecific and due to breakdown of the blood-brain barrier.     

The effects of expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs

It is not known whether positive end-expiratory pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome or also affects the resolution of their lung injury. We examined the effects of expiratory positive airway pressure (EPAP), a form of PEEP, on 13 pairs of spontaneously breathing mongrel dogs with permanent tracheostomies that were subjected to acute lung injury from oleic acid. One member of each pair was treated with 10 cm H2O EPAP by means of a special valve attached to its tracheostomy tube; the other member breathed through the tracheostomy tube alone. The EPAP was applied 3 h after an intravenous injection of 0.06 ml/kg oleic acid and continued for a total of 21 h. Functional residual capacity (FRC) was increased to preinjury values in the EPAP-treated dogs at 3, 12, and 24 h compared with that in the untreated dogs. The PaO2 was higher and the venous admixture (Qva/QT) was lower in the EPAP-treated dogs compared with that in the untreated dogs at 3 and at 12 h. However, over the 7 days after removal of EPAP no significant differences were noted between the 2 groups in FRC, PaO2, Qva/QT, inert gas elimination profiles, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histologic features. We conclude that EPAP improves gas exchange during its administration but has no demonstrable effect on the resolution of lung injury induced by oleic acid in dogs.     

The use of the BiPAP biphasic positive airway pressure system in acute spinal cord injury

Transurethral electrovaporization of the prostate (TVP) is a new minimally invasive procedure for treatment of enlargement of prostate. Between April 1996 and September 1997, TVP was carried out in 109 cases with symptoms of lower urinary tract obstruction. A Stortz spike electrode and a Stortz vapor cutting electrode were used for vaporization electrodes. Efficacy parameters evaluated included International Prostate Symptom Score, peak uroflow and postvoid residual volume. By September 1997, 32 cases (spike electrode) and 33 cases (vapor cutting electrode) could be followed up and evaluated. They have shown both subjective and objective voiding improvement. The improvements in subjective symptom scores and objective voiding parameters were not significantly different between the two electrode groups. Early complications included urinary retention, intraoperative burn, stress incontinence, blood transfusion and postoperative hemorrhage. Late complications included urethral stricture, bladder neck contracture and bladder stone. TVP was found to have several advantages, particularly minimal bleeding and the low incidence of postoperative morbidity. The technique is simple and symptoms improve at an early stage following surgery. This study demonstrates that TVP is a safe and effective modality for treatment of BPH. However, long-term studies with larger numbers of patients are needed.     

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.     

The effect of pregnancy on survival in women infected with HIV: a systematic review of the literature and meta-analysis

OBJECTIVE: To investigate the effect of pregnancy on disease progression and survival in women infected with HIV by a systematic review of the literature and meta-analysis. METHODS: Appropriate publications were identified using electronic and hand searching of relevant journals from 1983 to 1996. Studies were included in the review if they were cohort studies, either prospective or retrospective, or case-control studies which investigated disease progression of pregnant women infected with HIV and included a control group of non-pregnant women infected with HIV for comparison. Methodological quality was assessed for each study. Data were extracted for predetermined outcome measures. Sensitivity analyses were performed to explore the association between pregnancy and disease progression for the following study characteristics: clinical setting (developed or developing countries), methodological quality (high or poor) and whether studies had controlled for potential confounding. RESULTS: Seven studies, all prospective cohorts, were eligible to be included in the review. The summary odds ratio for the risk of an adverse maternal outcome related to HIV infection and pregnancy were as follows: death 1.8 (85% CI 0.99-3.3); HIV disease progression 1.41 (95% CI 0.85-2.33); progression to an AIDS-defining illness 1.63 (95% CI 1.00-2.67) and fall of CD4 cell count to below 200 x 10(6)/L 0.73 (95% CI 0.17-3.06). Sensitivity analyses showed that HIV progression in pregnancy was significantly more common in a developing country setting (odds ratio 3.71, 95% CI 1.82-7.75) than in developed countries (odds ratio 0.55, 95% 0.27-1.11) and also significantly more common in high quality studies when compared to low quality ones, odds ratios 3.71 (95% CI 1.82-7.57) and 0.55 (95% CI 0.27-1.11), respectively. However, there appears to be less progression of HIV disease and progression to AIDS when studies attempted to control for confounding by matching or restriction techniques, although this was not statistically significant in either case. CONCLUSIONS: The findings of this review have implications for women infected with HIV who are pregnant or are considering a pregnancy. There does appear to be an association between adverse maternal outcomes and pregnancy in women infected with HIV, although this association is not strong. The relation may be due to the result of bias including residual confounding. Further large scale observational studies with long term follow up are required before this issue can be fully resolved.     

Effect of noninvasive positive pressure ventilation on mortality in patients admitted with acute respiratory failure: a meta-analysis

Changes in angiogenesis and expression of extracellular matrix-degrading enzymes have been substantiated during progression of solid tumours, whereas information on haematological tumours remains circumstantial. In this study, 57 biopsies of mycosis fungoides (MF), a haematological tumour of T-cell lineage, were investigated immunohistochemically for the extent of angiogenesis, and by in situ hybridisation for the expression of matrix metalloproteinases 2 (MMP-2, collagenase A) and 9 (MMP-9, collagenase B). The biopsies we grouped according to the stage of progression: patch-->plaque-->nodular (most advanced). The extent of angiogenesis, as microvessel area, of MF lesions as a whole was significantly higher than that of normal uninjured skin, used as a control. When the stages of MF progression were compared, the values of MF patch stage overlapped that of control skin, while values were significantly higher in the plaque stage and even higher in the nodular stage. In these stages, microvessels were widely scattered in the tumour tissue, in close association with tumour cells, and they frequently displayed arborisation and microaneurysmatic dilation. In contrast, in the patch stage microvessels were irregularly distributed around the tumour aggregates, and arborisation or dilated structures were only rarely seen. The expression of MMP-2 and MMP-9 mRNAs underwent significant upregulation in relation to advancing stage. Indeed, the upstaging was significantly associated with higher proportions of lesions positive for each mRNA or for both, and with lesions with the greatest intensity of expression for each mRNA. Besides tumour cells, the MMP-2 mRNA was expressed by microvascular endothelial cells of intratumour and peri-tumour vessels, and by fibroblasts which were especially abundant in the stroma adjacent to the tumour nodules. The MMP-9 mRNA was found to be present in a subset of tissue macrophages which were more frequently located in close vicinity to the tumour nodules. In contrast, in control skin, a weak positivity for the MMP-2 mRNA in very few microvascular endothelial cells and no signal for the MMP-9 mRNA were observed. These in situ data suggest that angiogenesis and degradation of the extracellular matrix occur simultaneously during MF progression. They imply that interaction between tumour cells and their microvasculature are all the more likely to occur during progression, occasionally with the contribution of tumour-associated stromal cells.     

Differential effects of nasal continuous positive airway pressure on reversible or fixed upper and lower airway obstruction

Our study was to assess whether there were differential effects of nasal continuous positive airway pressure (nCPAP) on different kinds of obstruction in either upper or lower airways in patients with chronic obstructive pulmonary disease (COPD). nCPAP (6 cmH2O for ten minutes) was applied to 7 patients with reversible extrathoracic upper airway obstruction (RUAO) and 3 patients with fixed extrathoracic upper airway obstruction (FUAO). Eighteen stable asthmatics, receiving methacholine challenge to induce a more than 20% reduction in FEV1, were randomly investigated for the effect of nCPAP or sham pressure on reversible lower airway obstruction. Nine stable COPD patients were enrolled to study the effect on irreversible lower airway obstruction. Maximal expiratory and inspiratory flow volume curves and dyspnoea scores were obtained before and after immediate withdrawal of nCPAP. In the RUAO group, nCPAP significantly improved stridor and dyspnoea scores, decreased the ratio of FEF50/FIF50 from 2.05 +/- 0.25 to 1.42 +/- 0.16, and increased peak inspiratory flow (PIF) as well as forced inspiratory vital capacity by 26 +/- 8% and 9 +/- 4%, respectively. In expiratory phase, there was no significant change in pulmonary functions. In asthmatics, nCPAP significantly reversed methacholine-induced bronchoconstriction increasing forced vital capacity by 10 +/- 3%, FEV1 by 15 +/- 4% and PIF by 32 +/- 11%. nCPAP significantly increased the response to bronchodilators. The improvement in airflow rate persisted for at least 5 min after nCPAP withdrawal and was highly correlated with the response to bronchodilators. There was no significant effect of nCPAP on airflow rate in COPD patients. Subjective dyspnoea score changes paralleled the pulmonary function improvement. We conclude that there are differential effects of nCPAP on airflow rates in patients with different nature of airway obstruction. Patients with airway obstruction caused by structural changes may not benefit from the use of nCPAP in improving airflow rates.     

Effects of computer-based clinical decision support systems on physician performance and patient outcomes: a systematic review

CONTEXT: Many computer software developers and vendors claim that their systems can directly improve clinical decisions. As for other health care interventions, such claims should be based on careful trials that assess their effects on clinical performance and, preferably, patient outcomes. OBJECTIVE: To systematically review controlled clinical trials assessing the effects of computer-based clinical decision support systems (CDSSs) on physician performance and patient outcomes. DATA SOURCES: We updated earlier reviews covering 1974 to 1992 by searching the MEDLINE, EMBASE, INSPEC, SCISEARCH, and the Cochrane Library bibliographic databases from 1992 to March 1998. Reference lists and conference proceedings were reviewed and evaluators of CDSSs were contacted. STUDY SELECTION: Studies were included if they involved the use of a CDSS in a clinical setting by a health care practitioner and assessed the effects of the system prospectively with a concurrent control. DATA EXTRACTION: The validity of each relevant study (scored from 0-10) was evaluated in duplicate. Data on setting, subjects, computer systems, and outcomes were abstracted and a power analysis was done on studies with negative findings. DATA SYNTHESIS: A total of 68 controlled trials met our criteria, 40 of which were published since 1992. Quality scores ranged from 2 to 10, with more recent trials rating higher (mean, 7.7) than earlier studies (mean, 6.4) (P<.001). Effects on physician performance were assessed in 65 studies and 43 found a benefit (66%). These included 9 of 15 studies on drug dosing systems, 1 of 5 studies on diagnostic aids, 14 of 19 preventive care systems, and 19 of 26 studies evaluating CDSSs for other medical care. Six of 14 studies assessing patient outcomes found a benefit. Of the remaining 8 studies, only 3 had a power of greater than 80% to detect a clinically important effect. CONCLUSIONS: Published studies of CDSSs are increasing rapidly, and their quality is improving. The CDSSs can enhance clinical performance for drug dosing, preventive care, and other aspects of medical care, but not convincingly for diagnosis. The effects of CDSSs on patient outcomes have been insufficiently studied.