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Biomedical subjects

J Roca

Publications and source records attributed to J Roca.

At least 289 records · Page 16Linked to original sources
PubMed1987

Gas exchange and pulmonary vascular reactivity in patients with liver cirrhosis.

To investigate the mechanisms underlying abnormal gas exchange in liver cirrhosis, 15 patients were studied while breathing room air, 11% O2, and 100% O2 in random sequence. Under basal conditions, patients showed mild reductions from normal in systemic and pulmonary vascular resistance, normal PaO2 (mean, 92.5 +/- 2.5 mm Hg), mild hypocapnia (mean, 34 +/- 0.7 mm Hg), and a slightly right-shifted oxyhemoglobin dissociation curve (P50, 27.2 +/- 0.4 mm Hg; 2,3-DPG, 13.1 +/- 0.6 mumol/g). Using the multiple insert gas elimination technique, we found mild to moderate ventilation-perfusion (VA/Q) inequality with a mean of 5% (range, 0 to 20%) of cardiac output (QT) perfusing low VA/Q ratio (less than 0.1) areas but no shunt. Breathing 11% O2, there were significant increases in QT, pulmonary artery pressure, and vascular resistance, whereas no changes occurred in VA/Q distribution, and there was no evidence for alveolar-endcapillary diffusion limitation for O2. In contrast, after 100% O2 shunt developed and VA/Q relationships worsened without significant hemodynamic changes. Furthermore, patients with cutaneous spider nevi (n = 8) showed more hepatocellular dysfunction (lower prothrombin values), lower systemic and pulmonary vascular resistance, less hypoxic pulmonary vasoconstriction (HPV), lower PaO2, and more VA/Q mismatch than did those without spiders. Our results confirm, therefore, that HPV is not fully abolished, as previously described, in hepatic cirrhosis. However, those patients with more advanced hepatic disease exhibit inadequate pulmonary vascular tone, which increases VA/Q inequality and lowers PaO2.

Adult↗
PubMed1986

Oxyhemoglobin affinity in patients with chronic obstructive pulmonary disease and acute respiratory failure: role of mechanical ventilation.

Oxyhemoglobin affinity was assessed in 20 subjects with chronic obstructive pulmonary disease, all of whom experienced acute respiratory failure. PaCO2, pH, and 2,3-diphosphoglycerate (2,3-DPG) were measured 24 and 48 h after admission, and then during weaning (for the ten patients on mechanical ventilation) or on discharge (for the ten nonventilated patients). At 24 h, nonventilated patients had a lower pH (p less than .001) and 2,3-DPG concentration (p less than .05) and a higher PaCO2 (p less than .01) than ventilated patients; 48 h later only PaCO2 was higher (p less than .01) in the former, and there were no differences between the two groups in the final set of measurements. There was a persistent left shift in the oxyhemoglobin dissociation curve (P50 at pH 7.4) in both groups throughout the study period. In contrast, the in vivo P50 was significantly lower in ventilated patients only at 24 h (22.7 +/- 2.2 vs. 25.8 +/- 1.5 torr, respectively, p less than .005). Our results suggest that changes of in vivo P50 in ventilated patients are probably related to the Bohr effect induced by mechanical ventilation. The latter swiftly corrects severe respiratory acidosis, causing an intra-erythrocytic alkalotic pH and raising the levels of 2,3-DPG.

2,3-Diphosphoglycerate↗
PubMed1986

Effect of nifedipine on arterial hypoxaemia occurring after methacholine challenge in asthma.

To investigate whether the effects of nifedipine on methacholine induced broncho-constriction could impair pulmonary gas exchange in bronchial asthma a randomised, double blind, crossover study in 13 symptom free asthmatic subjects was designed. Each patient underwent a methacholine bronchial challenge test on two separate days one week apart, after having either oral nifedipine (20 mg thrice daily) or placebo for three days. Arterial blood gases were measured before and after methacholine challenge in nine subjects. Prechallenge values of forced expiratory volume in one second (FEV1) and arterial oxygen tension (Pao2) were similar after nifedipine and after placebo. After challenge, the cumulative doses of methacholine required to produce a 20% fall in FEV1 (PD20 FEV1) were significantly larger after nifedipine (280 (SD 347)) cumulative breath units (CBU) than after placebo (120 (183) CBU; p less than 0.01). After challenge the fall in Pao2 values (17.1 (1.6) mm Hg; (2.28 (0.21) kPa)) was significantly greater than after placebo (11.7 (2.4) mm Hg; (1.56 (0.32) kPa) p less than 0.03). Our data show that although oral nifedipine significantly reduces airway reactivity in patients with mild bronchial asthma, it also adversely affects pulmonary gas exchange, resulting in a lowered postchallenge Pao2, probably because of worsening ventilation-perfusion relationships.

Adult↗
PubMed1986

[Determination of the distribution of ventilation-perfusion ratios: technic of elimination of multiple inert gases].

The multiple inert gas elimination technique (MIGT) facilitates the estimation of the distributions of ventilation-perfusion (VA/Q) ratios in the experimental and clinical setting. The most relevant technical aspects and equipment and operational requirements needed to measure a mixture of inert gases in both the gas phase and the blood phase using gas chromatography are overviewed with detail. Results obtained in 3 dogs and 4 syringe-homogeneous lung models were entirely consistent with data formerly reported in the literature. Particular attention is paid to the linearity of the gas chromatograph detectors, reproducibility of inert gases sampling, and analysis of brands of heparin to detect acetone content. The errors of measurement (coefficients of variation) in blood were: 1.4 for sulfur hexafluoride; 1.8% for ethane; 2% for cyclopropane and halothane, each; 2.4% for diethyl ether; and, 3.6% for acetone. Important practical points are also emphasized in order to draw attention to potential problems and issues that should be concentrated upon to minimize the error in the measurements. It is concluded that the setting up of the MIGT is well established and validated.

Animals↗
PubMed1986

Correlation of bronchoalveolar lavage and clinical and functional findings in asbestosis.

Respiratory clinical, radiographic, and functional findings were assessed and correlated with bronchoalveolar lavage (BAL) cellular changes in 52 asbestos workers (27 with and 25 without asbestosis) and in 15 control subjects without asbestos exposure. Subjects with asbestosis had a moderate neutrophilic alveolitis (7.8 +/- 5%) compared with the other groups (p less than 0.001) that was correlated with the presence of crackles (p = 0.03) and PaO2 (p less than 0.05) and AaPO2 at rest (p less than 0.05) values. Asbestos bodies (AB) in BAL were quantitated in 34 of the 52 asbestos workers (21 with and 13 without asbestosis) and in the control group. They were present in 83% of asbestos workers but they were absent in the latter. No significant differences were observed in the number of AB between those asbestos workers with and without lung disease. We conclude that crackles on auscultation and PaO2 and AaPO2 values may well be good indicators of the staging of neutrophilic alveolitis in asbestosis. In contrast, the amount of AB in BAL is not a reliable marker of asbestos lung fibrosis.

Adult↗
PubMed1985

On the diversity of sperm histones in the vertebrates: IV. Cytochemical and amino acid analysis in Anura.

The variability of sperm histones in frogs has been studied by cytochemical and amino acid analyses. Cytochemically, Rana sperm proteins fall into Bloch's ('69, '76) type 4 somatic-like histone category, while Xenopus and Bufo have type 3 intermediate sperm histones. Extractability in 5% trichloroacetic acid (TCA) at different temperatures splits this type 3 category into two groups: type 3B intermediate sperm histones of Bufo are extractable at 85-90 degrees C, while Xenopus intermediate type 3A sperm histones require temperatures of 95-100 degrees C for extraction. Amino acid analysis confirms that Rana sperm histones are of the nucleosomal type, with a testis-specific, very lysine-rich H1 histone. The sperm protein in Bufo is richer in arginine than the proteins in Xenopus. Both of these genera contain lysine and histidine as well as arginine in their sperm proteins. These results confirm earlier electrophoretic data (Kasinsky et al., '78) and indicate that sperm histones in the order Anura can vary markedly between different genera.

Amino Acids↗
PubMed1985

Ventilatory control in diabetes mellitus.

The ventilatory control system was evaluated in a group of 40 diabetic patients (20 with autonomic neuropathy (AN), and 20 without autonomic neuropathy) and 20 controls. The ventilatory increase in response to transient hypoxia was less in diabetics without AN than in controls, but even weaker in diabetics with AN. This pattern was repeated in the ventilatory response to hypercapnia. There was no correlation between the presence of abnormal respiratory responses and the duration of diabetes.

Adult↗
PubMed1983

Mechanical ventilation in severe exacerbation of asthma. Study of 26 cases with six deaths.

A prospective study was carried out in 26 patients intubated and mechanically ventilated for severe exacerbation of asthma. The age of onset of asthma and the duration of disease showed wide variations, but most of the patients were women in their fifties with chronic asthma. However, 23% had the more benign intermittent course. Most patients had a prodromal period of several days with progressive deterioration. Eight patients developed sudden attacks, in three of them aspirin-intolerance was responsible, in two patients emotional disturbances could play some role as triggering factors, and in three other patients no obvious reason was found. Identification of factors responsible for the sudden attacks may be relevant to the management of these severe cases. The majority of patients were intubated immediately on arrival or during the first hours after admission. Deaths were related to complications produced by hypoxia, or hospitalization in an intensive care unit. Probably many of these patients would not have died if an appropriate steroid treatment had been given some days before.

Adolescent↗