[Results of functional analysis on an obstructive model of the lung using an Ergojet CVT high-frequency jet respirator. Comparison with the normal pattern]. / Resultados del análisis funcional sobre modelo obstructivo de pulmón del respirador con jet a alta frecuencia Ergojet CVT. Comparación con el patrón normal.

This paper expands a previous study on functional analysis of high frequency jet (HFJV) "Ergojet CVT" ventilation module inserted in Ergotronic 3 (Temel SA) respirator. The analysis was made on a pulmonary monoalveolar model with a compliance of 50 ml/cmH2 = and a resistance of 20 cmH2O/l/se simulating an obstructive pattern. Results were also compared with those obtained in a previous study on normal lung. HFJV was applied using a jet with or without additional gas input (VE) at respiratory rates of 90, 120, 150, 180, 210, 240, 270, and 300 per minute varying in each frequency the releasing pressure of the jet (PG 1, 2, and 3 kg/cm2) and the inspiratory time (Ti 30 to 50%) giving rise to a total of 96 different situations. In each of these conditions we measured the air way pressure (Paw) and the alveolar pressure (PA) and we calculated the tidal volume (VT) and the trapped volume (VAT). These measurements were correlated with those monitored by the respirator and those obtained in the normal lung. Results show that the VT is composed almost exclusively by the jet volume (VTjet), being only of consideration the VE with a Ti of about 33% and a PG of 2 to 3 kg/cm2. When the normal pattern was compared with the obstructive one, a small reduction in VT (average of 15%) and a marked increase in peak Paw (average of 75%) were observed. The use of a Ti of 50% has no clinical interest due to the large VAT that it produces.(ABSTRACT TRUNCATED AT 250 WORDS)

[Functional analysis of the high frequency jet respirator on a normal lung model. Ergojet CVT]. / Análisis functional en un modelo de pulmón normal del ventilador con jet a alta frecuencia. Ergojet CVT.

In this paper the results of the functional analysis of the Ergojet CVT, which is the high-frequency jet ventilation (HFJV) module of the Ergotronic 3 ventilator (Temel S.A.) are described. For a better understanding a detailed description of the module has been included. The functional analysis was performed on a standard lung model of normal compliance and resistance (C: 50 ml/cmH2O and R: 8 cmH2O.1-1.seg-1). High frequency jet ventilation was applied using the jet with and without additional gas entrainment, at frequencies of 90, 120, 150, 180, 210, 240, 270 and 300 rpm; for each frequency changes were made on the driving pressure (Pdriv: 1-2-3 kg.cm-2) and the inspiratory time (Ti: 33-50%). The combination of these parameters produced 96 different ventilatory circumstances. In each of them, airway and alveolar pressures (Paw and PA) were measured. Tidal and alveolar gas-trapped volumes (VT and Vtrap) were calculated from the previous PA measurements. These values were compared with those displayed by the ventilator. Following the results of the functional analysis of the Ergojet CVT, the VT delivered by the jet is the primary determinant of the VT, being little de increment due to the entrainment of gas. In the normal lung model, an adequate VT is obtained until frequencies of 240 rpm, using a Pdriv of 3 kg.cm-2. Vtrap, as in conventional ventilation, depend on VT and Te. The Pdriv and Ti, can be adequatelly combined in order to obtain a minimal Vtrap. Peak Paw depends on VT and Paw min on Vtrap.(ABSTRACT TRUNCATED AT 250 WORDS)

[Application of high frequency jet ventilation during microsurgery of the larynx under suspending laryngoscopy]. / Aplicación de la ventilación con jet a alta frecuencia durante la microcirugía de laringe bajo laringoscopia en suspensión.

OBJECTIVES: This study describes the results obtained with high frequency jet ventilation (HFJV) in 19 patients who underwent laryngeal microsurgery under suspending laryngoscopy. MATERIAL AND METHODS: After premedication and anesthetic induction with propofol (Diprivan R, ICI-Farma), we performed an endotracheal intubation (28F tube) under succinyl-choline facilitation. Conventional ventilation was started at a rate of 14-16 cpm with a minute volume of 8-10 l, and a FiO2 of 0.4 (air-oxygen). The endotracheal tube was replaced by an insufflation catheter of 2 mm internal diameter and HFJV was initiated at a rate of 100 cpm, inspiratory time equal to the 33% of the total cycle, generator pressure of 2.5-3.6 kg/cm2, and similar FiO2. We used an Ergojet CVT (Temel SA) respirator that allowed continuous monitoring of the injector released volume during each cycle (Vjet) as well as the air way pressure. Anesthesia was maintained with continuous propofol perfusion. RESULTS: During HFJV there were no significant hemodynamic alterations and surgeons considered that the condition of the surgical field was excellent. Air way pressure was maintained at low levels in all cases, although brief hypertensive episodes occurred during laryngeal manipulation. Oxygenation was satisfactory in all except one patient with chronic obstructive pulmonary disease. Conventional ventilation and HFJV did not induce significant differences in alveolar ventilation nor in PaCO2. However, during HFJV oxygenation and ventilatory levels suffered a high degree of interindividual variability. This phenomenon could be due to the existence of variable degrees of gas reflux during insufflation. CONCLUSIONS: We conclude that HFJV is a very useful technique for anesthesia in laryngeal microsurgery. However, an appropriate monitoring of ventilatory dynamics and a detailed knowledge of the influences of patient's characteristics on HFJV are required.

[Conditioning factors in intrapulmonary gas trapping during controlled mechanic ventilation in anesthesia]. / Factores condicionantes de atrapamiento intrapulmonar de gas durante la ventilación mecánica controlada en anestesia.

OBJECTIVES: To establish a relation between intrapulmonary gas trapping (Vat) generated by controlled ventilation during anesthesia and the factors that are likely to condition such trapping: flow volume (VT), expiratory time (te), compliance (C), resistance (R) and a time constant in either the anesthetized patient (tau) or under conditions of forced expiration in respiratory function testing (TC 25/50). PATIENTS AND METHODS: Thirty patients undergoing surgery with general anesthesia were ventilated following 3 different patterns with te of 2.66, 2 and 1.33 sec, respectively. We measured Vat, C, R and tau for each pattern. Correlation coefficients were figured and line regressions were drawn for Vat and the conditioning factors. We also figured the correlation between mean Vat and calculated Vat based on TC 25/50. RESULTS: Intrapulmonary gas trapping occurred in 93% of patients and increased significantly as te decreased. Correlations between Vat and the factors were as follows: r=0.76 for tau, r=0.62 for C, r=0.62 for R, r= 0.13 for VT and r2 = -0.92 for te/tau. The correlation coefficient of tau and TC 25/50 was 0.92. CONCLUSIONS: The results obtained indicate that Vat depends above all on the ratio of te to tau and that trapping can be prevented by applying a te that is greater than 3 tau.