Non-invasive mechanical ventilation: any role in ICU?
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Biomedical subjects
Publications and source records attributed to S Nava.
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OBJECTIVE: To assess hematologic and biochemical blood variables in growth-restricted fetuses and relate them to biophysical measurements. METHODS: Blood was sampled from 22 growth-restricted fetuses. All had normal karyotypes and no congenital infections. Venous pH, partial pressure of oxygen, hematocrit, glucose, uric acid, urea, creatinine, total protein, total and direct bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, lactic dehydrogenase, amylase, pseudocholinesterase, creatinine kinase, triglycerides, and cholesterol were measured and compared with our reference range. RESULTS: Ultrasound measurements of abdominal circumference correlated with fetal pH (r = 0.64), partial pressure of oxygen (r = 0.52), glucose (r = 0.67), total bilirubin (r = -0.54), lactic dehydrogenase (r = -0.48), and triglyceride levels (r = -0.65). Compared with fetuses with present end-diastolic velocities in the umbilical artery, the eight with absent end-diastolic velocities had lower pH (median z score -4.31), partial pressure of oxygen (median z score = -2.39), glucose (median z score = -2.01), and cholesterol (median z score = -2.34), and higher gamma-glutamyltransferase (median z score = 2.43), lactic dehydrogenase (median z score = 3.75), urea (median z score = 1.33), creatinine (median z score = 1.23), and triglyceride levels (median z score = 1.71). Only triglycerides correlated with abdominal circumference, independent of Doppler results. CONCLUSION: Growth-restricted fetuses with absent end-diastolic velocities in the umbilical artery had more marked acidemia, hypoxemia, hypoglycemia, and abnormal liver function than those with end-diastolic velocities. Triglyceride levels were inversely related to fetal size independent of Doppler results. High triglyceride levels might reset fetal homeostatic mechanisms, leading to disturbances of lipid metabolism in later life.
OBJECTIVES: To analyse the evolution and outcome in utero and after birth of infants with a fetal diagnosis of congenital heart disease. DESIGN: Inclusion criteria were the fetal diagnosis of congenital heart disease, confirmed postnatally or postmortem, and a complete follow up in utero and after birth. SETTING: 20 centres operating prenatal echocardiographic screening. PATIENTS: 847 cases were included in the study. Gestational age at diagnosis ranged from 15-39 weeks; in 370 cases (43.7%) the diagnosis was made before 24 weeks' gestation. RESULTS: 245/847 cases (28.9%) were terminated during pregnancy, 227 following early diagnosis; 128/245 cases (52. 2%) had associated anomalies and 117/245 (47.8%) had serious congenital heart disease. Of the remaining 602 cases that continued the pregnancy, 72 (11.9%) died in utero, 259 (43%) died postnatally (83 after surgery or invasive procedures), and 271 infants (45%) survived and presently range in age from 18 months to 13 years old. The mortality rate was higher in cases with associated extracardiac or chromosomal anomalies (68% and 74% of cases continuing pregnancy, respectively), and in cases with heart failure and complex cardiac defects. CONCLUSIONS: The data confirm a relevant fetal and postnatal loss in cases with complex congenital heart disease, and major clinical use of prenatal diagnosis in the management of ductus dependent anomalies. Negative prognostic factors for the outcome were associated anomalies and heart failure.
BACKGROUND: Idiopathic pulmonary fibrosis is an inflammatory disease which leads to chronic ventilatory insufficiency and is characterised by a reduction in pulmonary static and dynamic volumes. It has been suggested that lung elastance may also be abnormally increased, particularly in end stage disease, but this has not been systematically tested. The aim of this study was to assess the respiratory mechanics during mechanical ventilation in patients affected by end stage disease. METHODS: Respiratory mechanics were monitored in seven patients with idiopathic pulmonary fibrosis being ventilated for acute respiratory failure (PaO2/FiO2 5.8 (0.3); pH 7. 28 (0.02); PaCO2 8.44 (0.82) kPa; tidal volume 3.4 (0.2) ml/kg; respiratory rate 35.1 (8.8) breaths/min) using an oesophageal balloon and airway occlusion during constant flow inflation. The total respiratory system mechanics (rs) was partitioned into lung (L) and chest wall (w) mechanics to measure static intrinsic positive end expiratory pressure (PEEPi), static (Est) and dynamic (Edyn) elastances, total respiratory resistance (Rrs), interrupter respiratory resistance (Rint,rs), and additional respiratory resistance (DeltaRrs). RESULTS: PEEPi was negligible in all patients. Edyn,rs and Est,rs were markedly increased (60.9 (7.3) and 51.9 (8. 0) cm H2O/l, respectively), and this was due to abnormal lung elastance (dynamic 53.9 (8.0) cm H2O/l, static 46.1 (8.1) cm H2O/l) while chest wall elastance was only slightly increased. Rrs and Rint, rs were also increased above the normal range (16.7 (4.5) and 13.7 (3.5) cm H2O/l/s, respectively). RL and Rint,L contributed 88% and 89%, on average, to the total. Edyn,rs, Est,rs, Rrs and Rint,rs were significantly correlated with the degree of hypercapnia (r = 0.64 (p<0.01), r = 0.54 (p<0.05), r = 0.84 (p<0.001), and r = 0.72 (p<0. 001), respectively). CONCLUSIONS: The elastances and resistances of the respiratory system are significantly altered in ventilated patients with end stage idiopathic pulmonary fibrosis. These features are almost totally due to abnormalities in lung mechanics. These profound alterations in elastic and resistive mechanical properties at this stage of the disease may be responsible for the onset of hypercapnia.
BACKGROUND: In patients with acute exacerbations of chronic obstructive pulmonary disease, mechanical ventilation is often needed. The rate of weaning failure is high in these patients, and prolonged mechanical ventilation increases intubation-associated complications. OBJECTIVE: To determine whether noninvasive ventilation improves the outcome of weaning from invasive mechanical ventilation. DESIGN: Multicenter, randomized trial. SETTING: Three respiratory intensive care units. PATIENTS: Intubated patients with chronic obstructive pulmonary disease and acute hypercapnic respiratory failure. INTERVENTION: A T-piece weaning trial was attempted 48 hours after intubation. If this failed, two methods of weaning were compared: 1) extubation and application of noninvasive pressure support ventilation by face mask and 2) invasive pressure support ventilation by an endotracheal tube. MEASUREMENTS: Arterial blood gases, duration of mechanical ventilation, time in the intensive care unit, occurrence of nosocomial pneumonia, and survival at 60 days. RESULTS: At admission, all patients had severe hypercapnic respiratory failure (mean pH, 7.18+/-0.06; mean PaCO2, 94.2+/-24.2 mm Hg), sensory impairment, and similar clinical characteristics. At 60 days, 22 of 25 patients (88%) who were ventilated noninvasively were successfully weaned compared with 17 of 25 patients (68%) who were ventilated invasively. The mean duration of mechanical ventilation was 16.6+/-11.8 days for the invasive ventilation group and 10.2+/-6.8 days for the noninvasive ventilation group (P = 0.021). Among patients who received noninvasive ventilation, the probability of survival and weaning during ventilation was higher (P = 0.002) and time in the intensive care unit was shorter (15.1+/-5.4 days compared with 24.0+/-13.7 days for patients who received invasive ventilation; P = 0.005). Survival rates at 60 days differed (92% for patients who received noninvasive ventilation and 72% for patients who received invasive ventilation; P = 0.009). None of the patients weaned noninvasively developed nosocomial pneumonia, whereas 7 patients weaned invasively did. CONCLUSIONS: Noninvasive pressure support ventilation during weaning reduces weaning time, shortens the time in the intensive care unit, decreases the incidence of nosocomial pneumonia, and improves 60-day survival rates.
OBJECTIVE: The study's aim was to analyze the type of cardiac involvement in fetuses or infants with twin-twin transfusion syndrome. STUDY DESIGN: Seventeen pairs of monochorionic diamniotic twin fetuses with twin-twin transfusion syndrome underwent serial Doppler echocardiographic studies. Repeated decompressive amniocenteses were performed in all pregnancies. RESULTS: No specific cardiac involvement was seen in donor twins in utero or after birth. All recipient twin fetuses showed variable degrees of biventricular hypertrophy and dilation with tricuspid regurgitation. These features were also evident in 45% of the recipient twin neonates. The fluid unbalance resolved with serial amniocenteses in 9 cases and in a further 2 after the death of the donor twin; in all 11 of these recipient twin fetuses there was some degree of improvement of the cardiac involvement, which became normal in all surviving recipient twin infants within 40 days to 6 months after birth. CONCLUSION: Features of cardiac hypertrophy with signs of a prehydropic or hydropic state develop during fetal life in recipient twins in twin-twin transfusion syndrome; this impairment is reversible with the resolution of the fluid imbalance or after delivery.
OBJECTIVE: Pulmonary rehabilitation has been shown to be of benefit to clinically stable patients with chronic obstructive pulmonary disease (COPD). This study examined the effect of pulmonary rehabilitation on some physiologic variables in COPD patients recovering from an episode of acute respiratory failure. DESIGN: A prospective, randomized study. SETTING: A respiratory intensive care unit (RICU). PATIENTS: Eighty COPD patients recovering from an episode of acute respiratory failure were randomized in a 3:1 fashion to receive stepwise pulmonary rehabilitation (group A, n=60 patients) or standard medical therapy (group B, n=20 patients). MAIN OUTCOME MEASURES: Improvements in exercise tolerance, sense of breathlessness, respiratory muscle function, and pulmonary function test values were measured, respectively, by exercise capacity (6-minute walking distance [6MWD]), dyspnea score (Visual Analog Scale [VAS]), maximal inspiratory pressure (MIP), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). INTERVENTIONS: Group A received pulmonary rehabilitation that consisted of passive mobilization (step I), early deambulation (step II), respiratory and lower skeletal muscle training (step III), and if the patients were able, complete lower extremity training on a treadmill (step IV). Group B received standard medical therapy plus a basic deambulation program. RESULTS: Sixty-one of 80 patients were mechanically ventilated at admission to the unit and most of them were bedridden. Twelve of the 60 group A patients and 4 of the 20 group B patients died during their RICU stay, and 9 patients required invasive mechanical ventilation at home after their discharge. The total length of RICU stay was 38+/-14 days for patients in group A versus 33.2+/-11 days for those in group B. Most patients from both groups regained the ability to walk, either unaided or aided. At discharge, 6 MWD results were significantly improved (p < .001) in Group A only. MIP improved in Group A only (p < .05), while VAS scores improved in both groups, but the improvement was more marked in group A (p < .001) than in group B (p < .05). CONCLUSIONS: COPD patients who were admitted to a RICU in critical condition after an episode of acute respiratory failure and who, in most cases, required mechanical ventilation benefited from comprehensive early pulmonary rehabilitation, compared with patients who received standard medical therapy and progressive ambulation.
Patients with IgA deficiency often demonstrate circulating antibodies against IgA, which have been suggested to be associated with transfusion reactions. Sera from three patients with common variable immunodeficiency (CVID) and one with a selective IgA deficiency with anti-IgA antibodies receiving subcutaneous gammaglobulin replacement therapy were analysed for serum levels of IgG, IgA and anti-IgA before and during a treatment period of 4-7 years. Treatment with gammaglobulin preparations containing significant amounts of IgA (< 5 mg/ml) resulted in a decrease or disappearance of the anti-IgA antibodies. Analysis of serum fractions, however, revealed anti-IgA activity in the complex-containing fractions. In vitro experiments gave similar results with a shift of anti-IgA activity from the monomeric to the complex-containing fractions (that could not be detected in whole serum). When the patients were subsequently switched to treatment with a preparation containing less IgA (< 80 microg/ml) or made an interruption in the treatment schedule, the anti-IgA antibodies reappeared. Importantly, however, one of the patients lost his anti-IgA activity during a 3-month period on the preparation containing the higher IgA levels, and these antibodies did not reappear after switching to the low IgA-containing preparation. After 5 years on this preparation, anti-IgA can still not be detected, suggesting induction of unresponsiveness.
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The respiratory system consists of two main parts, the lung and the ventilatory pump. The latter consists of the bony structure of the thorax, the central respiratory controllers, the inspiratory and expiratory muscles, and the nerves innervating these muscles. Respiratory muscle fatigue occurs when respiratory muscle endurance is exceeded. Muscle fatigue is defined as a condition in which there is a reduction in the capacity for developing force and/or velocity of a muscle, resulting from muscle activity, and which is reversible by rest. The respiratory muscles are somewhat difficult to assess and the techniques employed are still relatively primitive. The most important methods of respiratory muscles function assessment are: 1) the vital capacity manoeuvre, which depends on maximum inspiratory and expiratory effort by the muscles and may be a useful indicator of respiratory muscle function; 2) radiological screening has been proposed for the detection of diaphragm paralysis. This may be helpful if the paralysis is unilateral, but bilateral paralysis is difficult to detect; and 3) respiratory muscles strength may be assessed with either voluntary or nonvoluntary manoeuvres. The function of the inspiratory muscles is assessed with 3 voluntary dependent manoeuvres. They are the so called Müller manoeuvre (or maximal inspiratory pressure), the sniff test and the combined test. All these three manoeuvres generate a pressure that is a reflection of complex interactions between several muscle groups since the efforts produce different mechanisms of activity of inspiratory and expiratory muscles. Two techniques are presently employed to assess diaphragm function, not being dependent on the patient's motivation: electrical phrenic nerve stimulation and cervical magnetic stimulation. Since it is less painful, magnetic cervical stimulation overcomes some of the difficulties encountered during electrical stimulation. With these two techniques recordings of diaphragmatic force are possible, and at the same time useful information about the conduction time of both phrenic nerves can be obtained.
Patients treated with BMT are extremely susceptible to infection with blood-borne viruses that can cause liver disease of variable clinical severity, from minimal biochemical changes to fulminant hepatic failure. Facing a patient with liver disfunction after BMT, one must bear in mind that more than one cause of liver disease, of viral and/or non-viral origin, may coexist. Moreover, besides the most important hepatotropic viruses, other agents, like herpesviruses (including CMV, adenoviruses, Epstein-Barr virus) may also be implicated, sometimes causing a life-threatening fulminant hepatitis, due to their cytopatic effect. Liver disease history and viral markers before transplant, together with the accurate assessment of the timing and type of clinical and biochemical deterioration are useful tools for a differential diagnosis. Liver biopsy, if taken in the early posttransplant period, is often difficult to interpret, while in case of liver disease occurring during immunosuppression tapering, histologic examination may discriminate between an exacerbation of viral hepatitis and an acute onset of chronic liver GVHD. While it seems that hepatitis G virus does not cause liver disease, the presence of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection is a matter of concern for its consequences both early after BMT and for long-term survivors. Despite screening for blood and marrow donors for HBV and, more recently, for HCV markers, the rate of post-transplant infection (4% and 4-15% respectively, confirmed in prospective studies) with those viruses indicates that viral hepatitis still remains an important clinical problem in this setting, although the prognosis of chronic HCV and HBV infection appears more benign than expected, especially in children.
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OBJECTIVE: Weaning from mechanical ventilation is often possible in the most of patients, even if sometimes it is very difficult. For example, 25-53% of COPD patients cannot be weaned. The different modalities used do not justify this. The aim of the study was the evaluation of a further weaning trial in tracheotomized patients who underwent mechanical ventilation for at least 15 days in several ICU and in whom several attempts of weaning failed. DESIGN: A retrospective study (January 1993-February 1995). SETTING: Intermediate Intensive Respiratory Care Unit of Centro Medico Di Montescano. PATIENTS: Thirty-nine patients (29 male; 26 COPD, 3 post-surgery respiratory failure, 5 restrictive diseases, 4 with cardiovascular failure and 1 neurological disease) who had been tracheotomized and undergoing mechanical ventilation from at least 15 days. An initial evaluation in which respiratory mechanics and echocardiography were performed was made and then they underwent further weaning trials based on progressive decrease of the level of pressure support and periodic disconnection from MV and on medical therapy and strong physiokinesitherapy. RESULTS: Twenty-six out of 39 patients (66%) could reach definitive weaning (COPD 65%, post-surgery respiratory failure 66%, restrictive 60%, cardiovascular failure 100%, neurological disease 0%) after 17 days of average time of ventilation (range from 4 to 90). Among the important factors in determining a difficult or impossible weaning there are: a) previous wrong ventilation settings 8/26; b) cardiovascular problems 7/26; c) alterations in respiratory mechanics 2/26; d) previous excessive sedation 2/26; e) uncorrect timing of disconnection 2/26; f) poor physiokinesitherapy 2/26; g) unknown causes 3/26. Also the ICU from which the patients has been transferred plays an important role. CONCLUSIONS: The conclusion is drawn weaning from mechanical ventilation can be reached also in a part of those patients who are thought not weanable with a further, prolonged and expensive weaning trial.
OBJECTIVE: Because individuals with Down syndrome appear to be protected from the development of atherosclerosis, we aimed to assess whether blood lipid and lipoprotein concentrations are different from controls in fetuses with trisomy 21. STUDY DESIGN: Eighteen fetuses with trisomy 21 and seven with trisomy 18 undergoing blood sampling at 18 to 36 weeks' gestation were matched by gestational age and size with an equal number of controls. Cholesterol and triglycerides were assayed in all fetuses and compared with the reference range constructed from 157 normal fetuses. High-density lipoproteins and apoproteins A and B were assayed in eight fetuses with trisomy 21, four with trisomy 18, and an equivalent number of controls. RESULTS: When compared with the reference range, fetuses with trisomy 21 had significantly increased cholesterol levels (median Z score 2.31, 95% confidence interval 1.57 to 3.08, p = 0.0001). Cholesterol and apoprotein A concentrations were also significantly higher than in fetuses with normal karyotypes matched by gestational age and size at sampling, whereas other lipids and lipoproteins were similar. There were no differences between fetuses with trisomy 18 and their matched controls. A value of fetal cholesterol > or = 85 mg/dl had a sensitivity of 72% and specificity of 95% in detecting fetuses with trisomy 21. CONCLUSIONS: Fetuses with trisomy 21 have abnormalities of lipid metabolism that are specific and may be genetically determined. The finding of high cholesterol levels in fetuses undergoing blood sampling for indications other than karyotyping should prompt investigation of fetal chromosomes because of the increased risk of trisomy 21. The mechanism through which high levels of cholesterol during prenatal life are not leading to increased risk of atherosclerosis remains to be elucidated.
The effects of different nitrogen and carbon sources on cell growth, pH, and exopolysaccharide (EPS) and poly-(beta)-hydroxybutyrate (PHB) production by two strains of Rhizobium meliloti (M5N1 and Su47) are reported. Differences in the behavior of glucose- and fructose-grown cells were shown, in particular with the M5N1 strain. Growth in a glucose-containing medium was accompanied by acidification of the culture medium, which leads to cell death. On fructose, acidification was detected only in the medium with a mineral nitrogen supply. A lag phase in EPS production was observed with cells grown with glucose, probably related to an initial extracellular conversion of the carbohydrate into an acid. No lag phase was observed in EPS production from fructose or in PHB synthesis whatever the carbon source. A decrease in PHB content was noticed for both strains under conditions where acidification of media occurred. The extent of production, emphasized by the use of a coproduction index, indicates that the M5N1 strain is a more promising organism than is the Su47 strain for polymer production. Such a strain, put in rich medium (containing yeast extract) supplemented with fructose, accumulated PHB up to 85% of dry cell weight and excreted about 1.5 g of EPS per liter in the medium. Regulation of the coproduction of EPS and PHB by these cells is suggested.
BACKGROUND: The effect of the type of trigger system on inspiratory effort has been studied in intubated patients, but no data are available in non-invasive mechanical ventilation where the "trigger variable" may be even more important since assisted modes of ventilation are often employed from the beginning of mechanical ventilation. METHODS: The effect of flow triggering (1 and 5 1/min) and pressure triggering (-1 cm H2O) on inspiratory effort during pressure support ventilation (PSV) and assisted controlled mode (A/C) delivered non-invasively with a full face mask were compared in patients with chronic obstructive pulmonary disease (COPD) recovering from an acute exacerbation. The patients were studied during randomised 15 minute runs at zero positive end expiratory pressure (ZEEP). The oesophageal pressure time product (PTPoes), dynamic intrinsic PEEP (PEEPi,dyn), fall in maximal airway pressure (delta Paw) during inspiration, and ventilatory variables were measured. RESULTS: Minute ventilation, respiratory pattern, dynamic lung compliance and resistances, and changes in end expiratory lung volume (delta EELV) were the same with the two triggering systems. The total PTPoes and its pre-triggering phase (PTP due to PEEPi and PTP due to valve opening) were significantly higher during both PSV and A/C with pressure triggering than with flow triggering at both levels of sensitivity. delta Paw was larger during pressure triggering, and PEEPi,dyn was significantly reduced during flow triggering in the A/C mode only. CONCLUSIONS: In patients with COPD flow triggering reduces the inspiratory effort during both PSV and A/C modes compared with pressure triggering. These findings are likely to be due to a reduction in PEEPi,dyn and in the time of valve opening with a flow trigger.
The aim of this study was to evaluate whether pressure support ventilation (PSV) requires different diaphragmatic efforts and patient-ventilator matching, according to the underlying disease. Four groups of patients requiring PSV were studied: Group A, recovering from an episode of acute respiratory failure due to adult respiratory distress syndrome (ARDS); Group B, with postsurgical complications; and two subsets of chronic obstructive pulmonary disease (COPD) patients, with "normal" static compliance of the respiratory system (Cst,rs) (Group C) or elevated Cst,rs (Group D). Ventilatory pattern, transdiaphragmatic pressure (Pdi), the pressure-time product of the diaphragm (PTPdi), static (PEEPi,stat) and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn), Cst,rs and resistance of the total respiratory system (Rrs) were recorded. The matching between patient and ventilator was analysed, recording the number of "ineffective efforts" (inspiratory efforts not efficient enough to trigger a new ventilator cycle, despite a positive deflection in Pdi). A satisfactory blood gas equilibrium arterial oxygen saturation (Sa,O2 > 93%, with a pH > 7.32) was obtained in the various groups with different levels of PSV. Minute ventilation was found to be significantly higher in Groups A and B, due to the longer expiratory time (tE) in the COPD groups. Group A (2 out of 7), Group B (3 out of 7), Group C (3 out of 5) patients showed sporadic "ineffective efforts". All Group D patients manifested continuous mismatching with the ventilator, so that the pressure-time product of the diaphragm per minute (PTPdi/min), reflecting the metabolic work of the diaphragm, was not different in the four groups. Tidal volume and the spontaneous inspiratory efforts were similar in the four groups, but the number of breaths delivered by the ventilator was significantly higher in Groups A and B. The application of different levels of pressure support ventilation in patients with acute respiratory failure due to different pathologies, led them to breathe with comparable pressure time product of the diaphragm. The majority of the patients showed mismatching with the ventilator, although this effect was more pronounced in the groups with chronic obstructive pulmonary disease.