Biomedical subjects

B Fabry

Publications and source records attributed to B Fabry.

24 records · Page 2Linked to original sources

PubMed1996

[Added work of breathing, respiratory pattern and determination of ventilator weaning readiness in inspiratory pressure support and and automatic tube compensation].

We measured the ventilatory pattern and additional work of breathing (WOBadd) at three different levels of inspiratory pressure support [IPS 5, 10, 15 mbar above positive end-expiratory pressure (PEEP)] and in a new ventilatory mode, automatic tube compensation (ATC), in nine operative patients without lung injury nine patients ventilated for several following acute respiratory insufficiency (ARI). In ATC, endotracheal tube resistance is compensated automatically by means of closed-loop control of the calculated tracheal pressure. Pressure support in this mode, i.e. airway pressure above PEEP, is equal to the actual flow-dependent pressure drop across the endotracheal tube (ETT). Airway pressure rises at the beginning of inspiration and falls towards the end. As the tube resistance of ETT seriously hinders expiration and can cause desynchronization between ventilator and patient, airway pressure is reduced below PEEP during expiration in the same way as it is increased during inspiration. The result is a near-constant tracheal pressure at PEEP both during inspiration and during expiration. This mode could be best termed as "electronic extubation". The most striking difference between the postoperative patients and the ARI patients was their minute ventilation (17.8 +/- 1.85 l/min in ARI patients vs 7.3 +/- 3.1 l/min in the postoperative patients). In the postoperative patients augmentation of IPS from 5 to 15 mbar induced a steady increase in tidal volume (VT) and a consecutive decrease in respiratory rate (rr) compared with ATC (VTATC,postop = 463 +/- 78 ml; rrATC,postop = 16 +/- 4 min-1; VTIPS5.postop = 505 +/- 79 ml; rrIPS5,postop = 15 +/- 4 min-1; VTIPS10,postop = 562 +/- 86 ml; rrIPS15,postop = 14 +/- 4 min-1; VTIPS15.postop = 660 +/- 151 ml; rrTPS15,postop = 12 +/- 4 min-1), whereas the augmentation of IPS of 5 and 10 mbar in the ARI patients could not compensate for the increase in rr and the decrease in VT, after switching from ATC to IPS (VTATC,ARI 724 +/- 308 ml, rrATC,ARI = 24 +/- 6 min-1; VTIPS5,ARI = 649 +/- 315 ml; rrIPS5,ARI = 27 +/- 8 min-1; VTIPS10,ARI = 653 +/- 353 ml; rrIPS10,ARI = 25 +/- 8 min-1: Even IPS 15 was not able to reestablish VT at the values observed during ATC (VTIPS15,ARI = 680 +/- 312 ml). During ATC WOBadd was small in both postoperative and ARI patients (WOBadd,ATC,postop = 93 +/- 36 mJ/l, WOBadd,ATC,ARI = 116 +/- 72 mJ/l). In the postoperative patients, an inspiratory pressure support of 5 mbar was not sufficient to compensate WOBadd compared with ATC. However, IPS 10 and 15 mbar were able to compensate for WOBadd (WOBadd,ATC5.postop WOBadd,IPS5,postop = 189 +/- 77 mJ/l; WOBadd,IPS10,postop = 55 +/- 30 mJ/l; WOBadd,IPS15,postop = 21 +/- 11 mJ/l). In the ARI patients an IPS 5, 10 or 15 mbar was not sufficient to compensate for WOBadd (WOBadd,IPS 5,ARI = 1126 +/- 262 mJ/l; WOBadd,IPS 10,ARI 863 +/- 253 mJ/l; WOBadd,IPS15,ARI 763 +/- 298 mJ/l). Under ATC, WOBadd was only 15% of WOBadd under IPS of 15 mbar. All but two patients were successfully extubated after the investigation. These two patients were not extubated because they were dependent on an FIO2 > 0.5. Our results strongly indicate that ventilatory dependence in ARI patients may be caused by the ETT rather than by mechanical dysfunction of the lung. ATC is a very helpful mode to use in distinguishing between ventilatory failure caused by ETT and real ventilatory dependence.

Adult↗

PubMed1995

Time constant/volume relationship of passive expiration in mechanically ventilated ARDS patients.

Since the adult respiratory distress syndrome (ARDS) lung is known to be inhomogeneous, one could expect an uneven distribution of expiratory time constant during uninterrupted mechanical ventilation. We investigated the time constant/volume relationship of passive expiration, and their modification by external resistive elements. In 12 paralysed intubated ARDS patients, we determined the expiratory time constant (tau E) as a function of the expired volume (VE) during uninterrupted mechanical ventilation. Mean expiratory time was 2.9 +/- 0.3 s (+/- SD). VE was divided into five equal volume slices (portions) and a mean tau E calculated from the expiratory tidal volume/flow curve for each slice. The mean values of tau E for each volume slice did not differ significantly throughout expiration, averaging 690 +/- 218 ms (mean +/- SD of five slices and 12 patients). We show that the flow-dependent resistance of the endotracheal tube (RETT) is mainly responsible for the observed time constant homogeneity. We conclude that in ARDS patients during uninterrupted mechanical ventilation the time constants of passive expiration are markedly modified by the flow-dependent resistance of the endotracheal tube (RETT), and also by the external resistance of tubing and ventilator (REX). RETT and REX render tau E about three times larger than the time constant of the patient's respiratory system alone.

Adult↗

PubMed1995

An analysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support.

It is common practice to convert patients with acute respiratory insufficiency (ARI) from controlled mechanical ventilation to some form of assisted spontaneous breathing as early as possible. A widely used mode of assisted spontaneous breathing is patient-triggered inspiratory pressure support (IPS). We investigated 11 patients with ARI during weaning from mechanical ventilation using IPS and found that in 9 of these patients, desynchronization between patient and ventilator occurred, ie, that the ventilator did not detect and support all the patients' breathing efforts. Five of these 9 patients displayed severe desynchronization lasting at least 5 min and with less than half of all breathing efforts being supported by the ventilator. We present the analysis of gas flow, volume, esophageal pressure, airway pressure, and tracheal pressure of 1 patient with ARI displaying desynchronization under IPS. Our results imply that desynchronization can occur due to the following: (1) inspiratory response delays caused by the inspiratory triggering mechanisms and the demand flow characteristics of the ventilator; (2) a mismatch between the patient's completion of the inspiration effort and the ventilator's criterion for terminating pressure support; and (3) restriction of expiration due to resistance from patient's airways, endotracheal tube, and expiratory valve. From our analysis, we have made proposals for reducing desynchronization in clinical practice.

Aged↗

PubMed1993

Continuous calculation of intratracheal pressure in tracheally intubated patients.

BACKGROUND: Intratracheal pressure (Ptrach) should be the basis for analysis of lung mechanics. If measured at all, Ptrach is usually assessed by introducing a catheter into the trachea via the lumen of the endotracheal tube (ETT). The authors propose a computer-assisted method for calculating Ptrach on a point-by-point basis by subtracting the flow-dependent pressure drop delta PETT(V) across the ETT from the airway pressure (P(aw)), continuously measured at the proximal end of the ETT. METHODS: The authors measured the pressure-flow relationship of adult endotracheal tubes with different diameters (ID, 7-9 mm) at different lengths and of tracheostomy tubes (ID, 8-10 mm) in the laboratory. The coefficients of an approximation equation were fitted to the measured pressure-flow curves separately for inspiration and expiration. In 15 tracheally intubated patients under volume-controlled ventilation and spontaneous breathing, the calculated Ptrach was compared with the measured Ptrach. RESULTS: The authors present the coefficients of the "nonlinear approximation": delta PETT = K1.VK2, with delta PETT being the pressure drop across the ETT and K1 and K2 being the coefficients relating V to delta PETT. An important result was an inspiration/expiration asymmetry: the pressure drop caused by the inspiratory flow exceeds that of the expiratory flow. A complete description of the pressure-flow relationship of an ETT, therefore, requires a set of four coefficients: K1I, K2I, K1E, and K2E. The reason for this asymmetry is the abrupt sectional change between ETT and trachea and the asymmetric shape of the swivel connector. Comparison of calculated and measured Ptrach in patients gives a correspondence within +/- 1 cmH2O (mean limits of agreement). The mean root-mean-square (rms) deviation is 0.55 cmH2O. CONCLUSIONS: Ptrach can be monitored by combining our ETT coefficients and the flow and airway pressure continuously measured at the proximal end of the ETT.

Adult↗

PubMed1992

A scale to measure restrictiveness of living environments for troubled children and youths.

Despite concerns about the restrictiveness of care and treatment procedures and settings for special populations, the concept of restrictiveness has seldom been defined or measured. This study describes the development of the Restrictiveness of Living Environments Scale (ROLES) for measuring the restrictiveness of residential settings for children and youths, including their own homes. Based on a literature review, the authors defined restrictiveness in terms of limits placed on freedom of movement or choice by the physical facility, by rules or requirements, and by conditions of entry and departure. The definition, along with a list of 27 residential settings for children, was sent to 389 child care professionals, who were asked to rate the restrictiveness of the settings on a 10-point scale, using a rating method designed to yield an interval scale. Ratings from 159 respondents, rounded to the nearest .5, were used to determine the relative position of the settings on the scale.

Activities of Daily Living↗

PubMed1990

[Right hemiplegia and spatial neglect with apraxia and agraphia without aphasia in a right-handed patient].

A 65 year-old right-handed woman was admitted after the sudden onset of a right dense hemiplegia. C.T. showed a large left infarction in the middle cerebral artery territory. There was a slight anosognosia and neglect of the right space without confusion. She had aprosodia but no aphasia. On the other hand, there was a severe apraxia and all the components of Gerstmann's syndrome were present. This suggests an unusual sattering of hemispheric functional dominances.

Aged↗