Evaluation of the expert system for respiratory therapy of newborns on archival data.

The aim of this study was to evaluate the artificial ventilation expert system for neonates (AVES-N) using archival data. The recommendations of the system were compared to the decisions made by the expert-physician in the same clinical situation (patient condition, respirator settings). In our retrospective study we used data of 320 newborns which were ventilated in the Neonatal Intensive Care Unit of the Vanderbilt University Hospital in Nashville (USA). Best agreement between the recommendations of the system and the decisions of the experts was found for positive end expiratory pressure (PEEP), inspired oxygen fraction (FiO2) and peak inspiratory pressure (PIP)--about 70%. Worse agreement was found for time related parameters: respiratory frequency (f) - 54%, time of inspiration (ti) - 46%, time of next blood gas analysis - 15%. The expert system advised lower FiO2 PEEP and f. The differences were smaller in a group of patients who survived than in a group of patients who died. The overall agreement of the AVES-N advice and real therapeutic actions leads to the clinical evaluation of the expert system. The differences can be attributed to a) different therapeutic strategies at 2 NICU's, b) missing data regarding complications in the data base which were not taken into account by the expert system.

Inhibition of phrenic nerve activity during positive-pressure ventilation at high and low frequencies.

A study was made to determine whether the ventilatory pattern, in terms of ventilatory frequency, insufflation period and end-expiratory pressure, influences the arterial blood gas level at which central inspiratory activity is inhibited, and whether further expansion of the lung changes this activity. This was accomplished by measuring arterial pH and blood gases, and intratracheal, intrapleural and transpulmonary pressures, at the setting of positive-pressure ventilation causing inhibition of phrenic nerve activity in chloralose-anaesthetized cats. Spontaneous breathing movements were prevented by muscle relaxation. Ventilatory frequencies of 15-120 breaths per minute (b.p.m.) were studied at at least two different insufflation times. A volume-controlled ventilator with a large compressible volume was used in the frequency range 15-45 b.p.m. and a constant flow respirator with a low-compressible volume in the range 45-120 b.p.m. A much lower PCO2 was needed for phrenic nerve activity to be inhibited at a ventilatory frequency of 15 b.p.m. than at higher frequencies. At ventilatory frequencies between 30 and 120 b.p.m. inhibition could be achieved at a higher PCO2, within the normal range. The inhibition of phrenic nerve activity tended to be less stable when PEEP was added during ventilation with a long insufflation period, but PEEP did not influence the arterial blood gas level at which inhibition occurred. In the lower frequency range of 15-30 b.p.m., inspiratory activity was observed with bursts at the same rate as the insufflations given by the ventilator. The intratracheal peak pressures at ventilation causing inhibition of phrenic nerve activity decreased with increasing ventilatory frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar deadspace during high frequency positive pressure ventilation. Influence of ventilatory pattern.

Pulmonary gas exchange was studied in association with high frequency ventilation and its relation to the duration of insufflation and end-expiratory pressure investigated. Alveolar deadspace, alveolar ventilation and the alveolar-arterial oxygen difference were obtained in cats receiving a constant minute ventilation. Alveolar deadspace increased with ventilatory frequency when a long insufflation time was used. A positive end-expiratory pressure (PEEP) decreased the alveolar deadspace in high frequency ventilation. Thus, with the low compressible volume ventilator, more efficient high frequency ventilation can be achieved with a short period of insufflation plus low PEEP.

Functional residual capacity and ventilatory pressures during positive-pressure ventilation at high frequencies.

The functional residual capacity (FRC) was measured in cats by the nitrogen washout technique during positive-pressure ventilation. Frequencies of 60 and 100 b.p.m. were used with insufflation periods of 20% and 35% of the ventilatory cycle, without and with a positive end-expiratory pressure. The higher frequency combined with the shorter insufflation period gave FRC close to that obtained during spontaneous breathing. The lower frequency and the longer insufflation period always gave greater FRC values. A further increase in FRC of about 23-27% was obtained after application of a positive end-expiratory pressure of 0.5 kPa. Adequate ventilation was achieved with small intratracheal and intrapleural pressures at all settings used.

[Naloxone as a drug for improving anesthesia results in children]. / Nalokson jako lek usprawniajacy anestezje u dzieci.

In anaesthesiology of today, due to the increased use of strong analgetics, it is necessary to have an effective antagonist for mini- mizing the danger of respiratory depression in postoperative period. Naloxone, ( Narcan , R-Endo Laboratories Inc., Subsidiary of E. J. du Pont de Nemours and Co., (Inc.), USA), a new narcotic antagonist was investigated in this study. It has been applied to 58 patients in cases of respiratory depression at the end of anaesthesia in which fentanyl was given, (these cases constituted 14% of all anaesthesias). Fentanyl was given intravenously in fractional doses, (fig 1), during NLA, and other general anaesthesias, for operation and diagnostic examination ( exeption of cardiosurgery), in children and adolescents from two month-to nineteen years of age, (tab. 1.). Naloxone was given intravenously, in fractional doses from 1 microgram to 5 micrograms/kg body weight. As a criterium of an antidepressive effect of Naloxone--in addition to clinical evaluation, blood gases analyses and continuous capnographic recording has been accepted. In all 58 cases diminition of respiratory depression was observed 2-3 min. after injected each dose of Naloxone. Respiratory rate increased from 15 to 22/min. concentration of CO2 in expired gases decreased from 5-6% to 4,5%, (fig. 2 and 3), and regain of consciousness, and return of intensive reaction to endotracheal tube stimulation was observed. Naloxone produced neither changes in the cardiovascular system, nor side effects. Based on these results Naloxone has been suggested as an effective narcotic antagonist. It increase of the possibility of applying strong analgetics in children--allowing to keep a steady level of anaesthesia with easy elimination respiratory depression in the desired period of time.

Comparative studies of artificial respiration sets for babies and infants.

In experiments on appropriately modified manikins the action and effectiveness of artificial respiration sets for infants Penlon (British production) and Ambu (Danish production) were compared. The tidal volume, pressure and characteristics of respiratory phases, rebreathing, oxygen concentration, safety systems and their effect on ventilation were assessed. It was found that better ventilation parameters for the needs of resuscitation of newborns and babies can be obtained using the Ambu set, particularly when compliance is lower and bronchial resistance is higher. The Ambu set is simple, easy and safe to use.

Anaphylactic shock following althesin. A case report.

The authors present a case of anaphylactic shock in a 9-year-old girl with heamorrhagic rash developing during anaesthesia. Shock was controlled with steroids, antihistamine drugs and dextran. The authors find it important to consider the possibility of the development of intravascular clotting in anaphylactic shock and the necessity of seeking a history of any allergy in patients before althesin anaesthesia.