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Biomedical subjects

J Sanchis

Publications and source records attributed to J Sanchis.

At least 127 records · Page 7Linked to original sources
PubMed1988

Induction of partial alterations in atrioventricular conduction in dogs by percutaneous emission of high-frequency currents.

Ten anesthetized dogs were studied in an attempt to provoke partial alterations in atrioventricular (AV) conduction by high-frequency current (HFC) transcatheter ablation. A discharge power (10 to 15 W) was used for less than 5 seconds after reaching complete AV block (CAVB). The catheter was placed within an area having an A/V ratio = 1 with His bundle deflection. If following discharge, no appreciable lengthening an AH, AV nodal block cycle length (Wenckebach point, WP), and/or functional nodal refractory period (FRPAVN) was observed, the procedure was repeated. Four dogs (group I) were killed immediately, and the other six (group II) after 2 to 4 weeks. The AH interval, WP, and FRPAVN were found to prolong significantly following HFC, without variations in HV interval. In group II, two dogs progressed to CAVB, whereas the other four maintained 1:1 AV conduction with AH, WP, and FRPAVN greater than before the power discharge. In conclusion, HFC is an efficient technique to induce partial alterations in AV conduction, since the discharge can be adjusted and the ablation can be localized to specific regions.

Animals↗
PubMed1988

Observations on variability of atrioventricular nodal conduction in man and the dual-pathway response.

A study was made of nodal conduction times of atrial stimuli with fixed coupling intervals, in 23 patients divided into two groups according to their atrial stimulus test response: Group I (continuous AV node function curve; 17 cases) and Group II (dual AV node pathway; six cases). The stimulation protocol involved the delivery of 75 stimuli with a fixed coupling interval 20 ms greater than the effective refractory period (ERP) of the AV node (Group I) or fast pathway (Group II). The atrial coupling intervals (A1A2) and node conduction times (A2H2) were measured. An evaluation was made of the dispersion of intervals with range (R) and of the distribution of A2H2 times (X2 test). In both Groups, R (A2H2) was greater than R(A1A2) (P less than 0.05); R(A2H2) in Group II was greater than R(A2H2) in Group I (P less than 0.001). In Group I the distribution of A2H2 was non-normal in four cases and bimodal in five; in Group II the distribution was non-normal and bimodal in all cases. It is concluded that: (1) the AV node generates a dispersion in its conduction times in the vicinity of its ERP, although the nodal conduction curve is continuous; and (2) the so-called dual pathway may constitute an exaggeration of AV node response inhomogeneity.

Adolescent↗
PubMed1988

Effect of body posture on respiratory impedance.

The effects of posture on the mechanics of the respiratory system are not well known, particularly in terms of total respiratory resistance. We have measured respiratory impedance (Zrs) by the forced random noise excitation technique in the sitting and the supine position in 24 healthy subjects. Spirometry and lung volumes (He-dilution technique) were also measured in both postures. The equivalent resistance (Rrs), compliance (Crs), and inertance (Irs) were also calculated by fitting each measured Zrs to a linear series model. When subjects changed from sitting to the supine position, the real part of Zrs increased over the whole frequency band. The associated equivalent resistance, Rrs, increased by 28.2%. The reactance decreased for frequencies lower than 18 Hz and increased for higher frequencies. Consequently, Crs decreased by 38.7% and Irs increased by 15.6%. All of these parameter differences were significant (P less than 0.001). A covariance analysis showed that a significant amount of the postural change in Rrs and Crs can be explained by the reduction of functional residual capacity (FRC). This indicates that the observed differences on Zrs can in part be explained be a shift of the operating point of the respiratory system induced by the decrease in the FRC.

Adult↗
PubMed1984

Performance of a low flow O2 Venturi mask: diluting effects of the breathing pattern.

To examine the performance of a new Venturi Mask (VM), PaO2 and PaCO2 were measured in 10 healthy volunteers before and while, breathing from a 0.24 O2 VM at 21/min of O2 flow for 20 min. FEO2, FECO2, VT, f, inspiratory (TI) and expiratory time (TE) and flow were also recorded during air breathing. Mean PaO2 increment observed during VM breathing was 1.8 kPa (SD 0.7). The FO2 measured at the face-piece of the VM while not in use was 0.247. The predicted increment of PaO2 corresponding to a FIO2 of 0.24 was calculated by the alveolar air equation and found to be 2.9 kPa (SD 0.2), indicating a diluting effect on the O2 concentration close to 40%, with an actual FIO2 of 0.228. The correlation coefficient (r) between dilution and a formula which includes initial acceleration of inspiration (VI 0.25), VT and the ratio TI/TT, was 0.94. Because the low O2 flow 0.24 VM model is markedly influenced by the patient's breathing, we conclude that it does not satisfactorily provide a stable and predictable concentration of supplementary oxygen. Theoretical considerations allow these results to be extended to other VM using low O2 flows for different O2 concentrations.

Adult↗
PubMed1978

Distension of the operation site after posterior fossa surgery.

In 130 posterior fossa operations 6 cases of progressive distension of the operation site have been recorded and documented. The possible causes of this complication and the surgical management are discussed. Isotope studies after injection of Ytterbium 169DTPA into the underlying cyst have shown abnormal patterns in CSF circulation and absorption. All the cases have resolved after ventriculo-peritoneal shunts.

Adult↗
PubMed1977

Immediate visual deterioration after attempts at radical excision of pituitary adenomas.

Thirty cases of pituitary tumour have been operated on in the last five years by a transfrontal approach, using microsurgical technique. Three cases of postoperative blindness are described, with an analysis of possible contributory factors and causative mechanisms, prognosis, and measures to lessen the risk of this complication. The possibility of an impairment in the chiasma blood supply is discussed. Although the use of the microscope makes the removal of the so-called capsule an easier surgical task, it is recommended that this structure should be left undisturbed.

Adenoma↗
PubMed1976

Aerosol penetrance: a sensitive index of peripheral airways obstruction.

Early injury of the small airways has been demonstrated in asymptomatic smokers. Ventilatory tests including the maximum midexpiratory flow rate and closing volume have been useful in clinical detection of small airways disease in symptomatic subjects. In the present study, airway "obstruction" was assessed aerodynamically by gamma camera measurements of chest radioactivity following the inhalation of 131I-labeled aerosol (aerodynamic mass median diameter 3 mum). Studies were performed in normal subjects, asymptomatic smokers, and patients with chronic obstructive lung disease. An aerosol penetrance index (AeP) was devised from determinations which involved 1) an analysis of central (inner zone) and peripheral (outer zone) deposition of aerosol in the lung and 2) a ratio of initial counts to 24-h counts in the periphery (outer zone) of the lung. AeP values were 41.5 +/- 11.5 for the normal group, 20.9 +/- 7.6 for the smoker group, and 10.6 +/- 5.2 for the subjects with chronic obstructive airway disease. AeP was significantly reduced in the smokers indicating that the AeP is a sensitive index of early peripheral airways obstruction.

Aerosols↗