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Biomedical subjects

J Roca

Publications and source records attributed to J Roca.

At least 91 records · Page 5Linked to original sources
PubMed2000

Noninvasive assessment of respiratory resistance in severe chronic respiratory patients with nasal CPAP.

Noninvasive measurement of respiratory resistance during nasal ventilatory support could be useful to assess the mechanical status of the patient and to optimize the ventilator settings. The aim was to investigate whether the forced oscillation technique (FOT) applied through a nasal mask allows reliable noninvasive estimation of respiratory resistance (Rrs) in patients with severe chronic respiratory disease. FOT Rrs (5 Hz) and lung resistance (R(L)) measured simultaneously from spontaneous breathing signals by an oesophageal balloon were compared in eight patients with chronic obstructive pulmonary disease and in six patients with a restrictive ventilatory defect due to chest wall disease. Measurements were performed in sitting and supine postures during application of nasal continuous positive airway pressure (CPAP): 4, 8 and 12 cmH2O in obstructive patients and 4 cmH2O in restrictive patients. In the restrictive patients Rrs and R(L) (in cmH2O x s x L(-1)) were virtually coincident: mean+/-SD, 12.6+/-6.1 and 11.6+/-6.6 (r=0.96) in sitting and 9.7+/-3.1 and 10.2+/-3.3 (r=0.92) in supine posture, respectively. In the obstructive patients (CPAP = 4 cmH2O), Rrs slightly underestimated R(L): mean+/-SD, 11.5+/-5.9 and 14.4+/-16.8 (r=0.92) in sitting and 15.0+/-9.8 and 21.1+/-12.6 (r=0.96) in supine posture, respectively. Similar results were found at CPAP = 8 and 12 cmH2O. The results obtained in patients with resistance values in the range typically found in nasal ventilatory support suggest that forced oscillation technique could be valuable to noninvasively estimate a patient's respiratory mechanical resistance.

Aged↗
PubMed2000

Evaluation of a method for assessing respiratory mechanics during noninvasive ventilation.

Noninvasive assessment of respiratory resistance (Rrs) and elastance (Ers), which is not easy with conventional methods, could be useful in the optimization of pressure support ventilation. The aim of this study was to evaluate a simple noninvasive method (Delta-inst) of measuring Rrs during nasal pressure support ventilation. Rrs and Ers (Delta-inst) were computed from inspiratory mask pressure, flow and volume recorded during pressure support ventilation. The Delta-inst method was compared with the forced oscillation technique (FOT) in seven patients with chronic obstructive pulmonary disease (COPD) and in eight healthy subjects without and with added resistance (3.1 cmH2O x s x L(-1)). Rrs measured by Delta-inst (5.2+/-1.7, 7.2+/-0.5 and 6.9+/-1.2 cmH2O x s x L(-1)) and by FOT (5.0+/-0.7, 7.6+/-0.9 and 8.1+/-2.7 cmH2O x s x L(-1)) in healthy subjects without and with added resistance and COPD, respectively, were not significantly different (p>0.05). Rrs measured by both techniques showed a significant coefficient of linear correlation (r=0.70 s) (p<0.01). In the COPD patients, the variability of Delta-inst Rrs (30%) was greater than that of FOT Rrs (21%). The agreement between Ers obtained by Delta-inst and by FOT was less than that found for Rrs. Delta-inst is a noninvasive and simple method for reliably assessing resistance. Therefore, it is useful for monitoring airway obstruction and is potentially helpful in adapting the settings for pressure support ventilation in accordance with patient mechanics.

Adult↗
PubMed2000

Pulmonary gas exchange response to oxygen breathing in acute lung injury.

The mechanisms and time course of the pulmonary gas exchange response to 100% O(2) breathing in acute respiratory failure needing mechanical ventilation were studied in eight patients with acute lung injury (ALI) (48 +/- 18 yr [mean +/- SD]) and in four patients (66 +/- 2 yr) with chronic obstructive pulmonary disease (COPD). We postulated that, in patients with ALI while breathing 100% O(2), the primary mechanism of hypoxemia, i.e., increased intrapulmonary shunt, would further worsen (increase) as a result of reabsorption atelectasis. Respiratory and inert gases, and systemic and pulmonary hemodynamics were measured at maintenance fraction of inspired oxygen (FI(O(2))-m), at 30 and 60 min while breathing 100% O(2), and then at 30 min of resuming FI(O(2))-m. During 100% O(2) breathing, in patients with ALI, Pa(O(2)) (by 207 and 204 mm Hg; p < 0.01 each), Pa(CO(2)) (by 4 mm Hg each) (p < 0.05 each), and intrapulmonary shunt (from 16 +/- 10% to 22 +/- 11% and 23 +/- 11%) (p < 0.05 each) increased respectively. By contrast, in patients with COPD, Pa(O(2)) (by 387 and 393 mm Hg; p < 0.001 each), Pa(CO(2)) (by 4 and 5 mm Hg) and the dispersion of pulmonary blood flow (log SDQ) (from 1.33 +/- 0.10 to 1.60 +/- 0.20 and 1.80 +/- 0.30 [p < 0.05]) increased, respectively. In patients with ALI, the breathing of 100% O(2) deteriorates intrapulmonary shunt owing to collapse of unstable alveolar units with very low ventilation-perfusion (V A/Q) ratios, as opposed to patients with COPD, in whom only the dispersion of the blood flow distribution is disturbed, suggesting release of hypoxic pulmonary vasoconstriction.

Aged↗
PubMed1999

Age-related changes in the hamster epididymis.

Reproductive ability is decreased in aged animals and in men. Little is known about the changes taking place in the epididymis, and the possible influence on the loss of sperm quality. We studied the age-related alterations in the epididymis and in epididymal spermatozoa of hamsters. Adult (6-month-old), middle-aged (18-month-old), and aged (24-month-old) hamsters were used. Serum samples were obtained to determine testosterone levels. Testes and epididymides were removed and studied by light and electron microscopy. Epididymal sperm was also obtained and the motility, position of cytoplasmic droplet, and concentration were evaluated. Measurements of the height of the epithelium, length of stereocilia, external tubular diameter, and thickness of the muscular wall were performed. The proliferative activity was also studied. An ANOVA analysis was used to compare quantitative differences between epididymal zones and age groups. Aged hamsters presented involutive changes in the epididymis. A decrease in tubular diameter was found in cauda; principal cell ultrastructure showed changes including the appearance of damaged mitochondria, bundles of filaments, and the accumulation of lipofuscin. Some clear cells showed an unusual morphology by the presence of large electrondense vacuoles. A reduction in sperm quality was also observed, including a decrease in sperm motility and concentration, and alterations in the migration of sperm cytoplasmic droplet. Testosterone levels and cellular proliferative activity did not change. Aging causes a morphological alteration of hamster epididymis (mainly in the cauda), and a decrease in sperm quality.

Aging↗
PubMed1999

One-stage decompression and posterolateral and interbody fusion for severe spondylolisthesis. An analysis of 14 patients.

STUDY DESIGN: A retrospective study of 14 patients with high-grade L5-S1 spondylolisthesis surgically treated with one-stage decompression and posterolateral and interbody fusion (technique of Bohlman and Cook). OBJECTIVE: To determine the efficacy of this technique in managing severe lumbosacral spondylolisthesis. SUMMARY OF BACKGROUND DATA: Controversy exists over the most appropriate method for managing high-grade spondylolisthesis. Circumferential in situ fusion from a single-stage posterior approach was described in 1982, but to the current authors' knowledge, there are not many reports on clinical results in the literature. The current authors studied 14 patients (mean age, 21 years) with severe L5-S1 spondylolisthesis. The percentage of slipping averaged 77%; slip angle averaged 36 degrees. The average follow-up period was 30 months. All patients had severe back or radicular symptoms. Two patients had foot drop, and four had minor neurologic dysfunction. Four patients had extremely tight hamstrings. METHODS: Pre- and postoperative radiographic films and computed tomography scans were reviewed. Magnetic resonance imaging was carried out in 11 patients before surgery and at follow-up examination. Patients were evaluated for fusion rate, clinical outcome, and complications. RESULTS: All six patients with motor deficit of the nerve roots showed complete strength recovery at follow-up examination. None of the patients had tightness of hamstrings. Twelve patients demonstrated incorporation of the graft with solid fusion, one patient had a fracture of the fibular graft, and one had graft resorption. All patients but one rated the surgical result as excellent. One patient was not satisfied with the cosmetic result. Transient paresthesias in the leg of the donor graft were documented in two patients. CONCLUSIONS: Posterior decompression of the spinal canal combined with anterior and posterior arthrodesis performed at one stage through a posterior approach is a safe and effective technique for managing severe spondylolisthesis.

Adolescent↗
PubMed1999

[The polymerase chain reaction as a marker of cytomegalovirus infection in heart transplant recipients].

BACKGROUND: To evaluate the usefulness of PCR in peripheral blood leukocytes for the diagnosis of CMV infection and for prognosis of CMV disease in patients with heart transplantation. PATIENTS AND METHODS: A total of 54 heart transplant recipients included in a protocolized virological follow-up with blood samples (total samples: 594). Mean time of follow-up: 14.8 months (range 1-34 months). We compared a qualitative nested PCR with tube culture (CC), shell vial culture (SV) and pp65 quantitative antigenemia test (AGC). RESULTS: PCR was the most sensitive test (89.9%) followed by AGC (68.1%), SV (42.6%) and CC (33.4%). Specificity: 80 samples were positive only by PCR, 77 of which form patients with virologically documented CMV active infection, so they were considered as true positives. Three samples were from 2 patients in which the unique positive marker was PCR. If we considered these results as false positive, the calculated specificity was 99.0%. PCR was the first positive marker in 44 out of 45 patients with active CMV infection. In 9 of these patients no other viral marker was positive in the first positive sample, except for PCR. A total of 16 episodes of CMV disease were observed along the study, and a positive PCR result was detected in 15 of them. The remaining patient did not show amplification with the set of primers used in this study, but it gave a positive PCR by amplifying with a different primer pair. Positive predictive value of PCR for CMV disease was low (33.3%). Thus, a positive PCR result did not allow to distinguish between asymptomatic infection and CMV disease. CONCLUSIONS: In heart transplantation recipients CMV-PCR is a highly sensitive, specific and early marker of CMV infection but its positive predictive value for CMV disease seems unsatisfactory.

Biomarkers↗
PubMed1999

Hepatopulmonary syndrome associated with cardiorespiratory disease.

BACKGROUND/AIMS: Hepatopulmonary syndrome is defined as a clinical triad including chronic liver disease, abnormal pulmonary gas exchange resulting ultimately in profound arterial hypoxaemia, and evidence of intrapulmonary vascular dilatations. We report five patients with liver cirrhosis diagnosed with hepatopulmonary syndrome who had associated chronic obstructive or restrictive respiratory diseases. METHODS: Clinical, radiographic and constrast-enhanced echocardiographic findings, and systemic and pulmonary haemodynamic and gas exchange, including ventilation-perfusion distributions, measurements were assessed in all five patients. RESULTS: Echocardiography was consistent with the presence of intrapulmonary vasodilation without intracardiac abnormalities, and high resolution computed tomographic scan features were compatible with clinical (3 cases) or histopathological diagnoses (2 cases) of associated respiratory disorders. The most common prominent functional findings were moderate to severe arterial hypoxaemia, caused by moderately to severely increased intrapulmonary shunting and/or mild to moderate low ventilation-perfusion areas, and hypocarbia along with an increased cardiac output and a low pulmonary artery pressure and vascular resistance. CONCLUSIONS: These functional characteristics, classically reported in the setting of clinically stable, uncomplicated hepatopulmonary syndrome, conform to a distinctively unique, chronic gas exchange pattern. Equally important, these pulmonary haemodynamic-gas exchange hallmarks are not influenced by the co-existence of chronic cardiorespiratory disease states. These data may have clinical relevance for elective indication of hepatic transplantation in patients with life-threatening hepatopulmonary syndrome.

Adult↗
PubMed1999

[Functional mitral regurgitation. Physiopathology and impact of medical therapy and surgical techniques for left ventricle reduction].

Functional mitral regurgitation is frequently observed in the setting of left ventricular dyfunction. This finding is a marker of poor outcome in patients with either ischemic or dilated cardiomyopathy. The mechanism accounting for this phenomenon is an altered balance of tethering versus coapting forces acting on the mitral valves in the failing heart. Tethering forces represent an anomalous tension on the mitral valves due to displacement of mitral valve attachments secondary to increased left ventricular chamber sphericity associated with systolic ventricular dysfunction. On the other hand, coapting forces are weak and unable to counteract the abnormal tension acting on the mitral valve, which restricts closure and leads to regurgitation. Vasodilators and inotropic drugs are effective in the management of functional mitral regurgitation. Although partial left ventriculectomy or Batista's procedure is still investigational, this new technique seems to provide an optimal control of functional mitral regurgitation and improve functional capacity and survival of some patients with heart failure.

Cardiac Surgical Procedures↗
PubMed1999

Isosorbide-5-mononitrate in the treatment of pulmonary hypertension associated with portal hypertension.

Pulmonary hypertension is uncommonly associated with portal hypertension. The current approach for the management of pulmonary hypertension involves the use of vasodilators in patients who show vascular responsiveness during an acute challenge. Since the association of portal hypertension with pulmonary hypertension is very seldomly presented, its optimal therapy has not been defined. Moreover, calcium-channel blockers, which are usually used in pulmonary hypertension treatment, may exert a deleterious effect on portal hypertension. Therefore, the search for drugs that may be active under both conditions has important clinical implications. This report presents the case of a patient with portal hypertension-associated pulmonary artery hypertension that was effectively treated with isosorbide-5-mononitrate (Is-5-Mn). The patient had severe portal hypertension (hepatic venous pressure gradient=14.5 mmHg) and pulmonary hypertension (mean pulmonary artery pressure (PAP)=50 mmHg). Acute administration of prostacyclin and nitric oxide elicited a significant reduction in both PAP and pulmonary vascular resistance (PVR), an effect that was also achieved with Is-5-Mn. The patient was treated with 40 mg Is-5-Mn twice daily and a haemodynamic study performed 6 months later showed that the reduction in both PAP and PVR persisted.

Female↗
PubMed1999

Effects of inhaled furosemide on platelet-activating factor challenge in mild asthma.

Furosemide (Fur) may have an anti-inflammatory effect on airways in patients with asthma although its intrinsic mechanism remains elusive. Platelet-activating factor (PAF) is a potent proinflammatory mediator that induces systemic and respiratory effects in normal control subjects and asthmatics. The aim of this study was to assess whether pretreatment with nebulized Fur (40 mg) was able to modulate PAF-induced systemic and respiratory effects in asthma. Eleven patients were studied (mean+/-sem 22+/-0.8 yrs) with mild asthma (forced expiratory volume in one second, 95+/-4%) in a randomized, double-blind, placebo-controlled, cross-over fashion, one week apart. PAF challenge (18 microg) was carried out 15 min after administration of Fur or placebo. Peripheral blood neutrophils, respiratory system resistance, and arterial blood gases were measured at baseline, and 5, 15 and 45 min after PAF; urinary cysteinyl leukotriene E4 (uLTE4) was also measured, at baseline and 120 min after PAF challenge. Although Fur did not alter PAF-induced systemic and respiratory effects, it did partially inhibit (63%; p<0.04) the increments of uLTE4 levels shown after PAF inhalation. It is concluded that furosemide is not effective in protecting against platelet-activating factor challenge in patients with asthma despite its potential inhibition of leukotriene synthesis. These findings reinforce the view that the pulmonary effects of platelet-activating factor are mediated through different pathways.

Administration, Inhalation↗
PubMed1999

Gas exchange response to a PAF receptor antagonist, SR 27417A, in acute asthma: a pilot study.

The pathogenic role of platelet-activating factor (PAF) in asthma has been questioned due to the limited or negative efficacy of PAF antagonists; however, in acute asthma (AA), where the endogenous release of PAF may be enhanced, the effects of PAF antagonist receptors have not been investigated. It was postulated that inhaled PAF provokes gas exchange defects in mild asthma likely to be related to airway vascular leakage. The response to a potent, selective PAF receptor antagonist, SR 27471A, on pulmonary gas exchange was studied, more specifically ventilation-perfusion (VA'/Q') distributions, in patients with AA within 48 h of hospitalization. A randomized, double-blind, placebo-controlled, parallel group (n=6, each) design was used. After baseline measurements, either placebo or SR 27417A (20 mg, orally) was administered and measurements were repeated 3 h later. Conventional anti-asthma medication was not interrupted. Despite a near-complete inhibition of the in vitro, platelet aggregation tests by 40 nM PAF (mean+/-SEM from 72+/-9 to 6+/-2%) and 80 nM PAF (from 81+/-7 to 6+/-3% both p<0.01) by SR 27471A indicating a good bioactivity of the compound, no significant changes in baseline forced expiratory volume in one second, (40+/-6%), respiratory system resistance (6.2+/-0.7 cmH2O x L(-1) x s), alveolar-arterial pressure difference for oxygen (5.2+/-0.4 kPa), arterial oxygen tension (9.0+/-0.5 kPa) or VA'/Q' distributions, as expressed by the dispersion of pulmonary blood flow (LogSD Q, 1.07+/-0.09; normal values <0.60), were observed. It is concluded that SR 27417A has limited value when added to the conventional treatment of acute asthma. These findings minimize the potential pathogenic role of endogenous platelet-activating factor as a relevant mediator of airway inflammation during acute asthma.

Acute Disease↗