Triggering delay time and work of breathing in three paediatric patient-triggered ventilators.

PURPOSE: To compare the effectiveness of three patient-triggered ventilators by evaluating triggering delay time and pressure-volume loops during initiation of inspiration. METHODS: In a two-part study, a model lung was used in part 1 and 20 children, after tracheal intubation, in part 2. Triggering delay time and work of breathing (WOB) during pressure support ventilation using three patient-triggered ventilators: Servo Ventilator 300, VIP Bird, and SLE 2000 Neonatal Ventilator. Triggering delay time was from the beginning of negative deflection in the oesophageal pressure trace, to the onset of inspiration. The WOB was estimated directly by measuring the oesophageal pressure-volume loop. RESULTS: The Servo demonstrated superior triggering delay time and reduced WOB in the model study. The VIP Bird demonstrated shorter triggering delay and reduced WOB in the clinical component of the study. In the model lung, triggering delay time in the Servo 300 [62 +/- 6 msec (mean +/- SD)] was shorter than that in the VIP Bird (76 +/- 7 msec) (P < 0.05), and WOB with the SLE 2000 (202 +/- 37 g.cm) was greater than with other ventilators, (Servo 300, 112 +/- 32 g.cm and VIP Bird 72 +/- 41 g.cm) (P < 0.05). In the clinical study, triggering delay time in the VIP Bird (52 +/- 19 msec) was shorter than in the other ventilators, Servo 300 (66 +/- 14 msec), SLE 2000 (68 +/- 65 msec) (P < 0.05). The Servo 300 (56 +/- 34 g.cm) required higher WOB than the other ventilators: VIP Bird (22 +/- 12 g.cm), SLE 2000 (14 +/- 3 g.cm) (P < 0.05). CONCLUSION: Comparative model lung performance of these ventilators does not correspond with their clinical performance. In our clinical evaluation, the VIP Bird ventilator demonstrated superior performance with shorter triggering delay time, low WOB needed to initiate inspiration, and little air leak.

[Severity and prognosis of congenital diaphragmatic hernia from the viewpoint of perioperative respiratory function].

We studied severity and prognosis of congenital diaphragmatic hernia (CDH) by using preductal arterial blood gas analysis (BGA) and pulmonary function tests (PFTs) in 29 newborn infants. CDH was diagnosed within 24 hours of life, and surgical repair was performed through an abdominal approach after a period of stabilization. The infants were classified into the following three groups based on the highest preoperative alveolar-arterial oxygen tension difference (A - aDO2) and the lowest arterial carbon dioxide pressure (PaCO2) values; Group A (n = 15) : A - aDO2 < 500 mmHg, PaCO2 < 40 mmHg, Group B (n = 7) : A - aDO2 > or = 500 mmHg, PaCO2 < 40 mmHg, Group C (n = 7) : A - aDO2 > or = 500 mmHg, PaCO2 > or = 40 mmHg. Furthermore, the patients were classified into the following three groups based on the preoperative respiratory system compliance (Crs) and forced vital capacity (FVC) values; Group D (n = 8) : Crs < 0.5 ml.cmH2O-1.kg-1, FVC < 10 ml.kg-1, Group E (n = 4) : Crs < 0.5 ml.cmH2O-1.kg-1, FVC > or = 10 ml.kg-1, Group F (n = 17) : Crs > or = 0.5 ml.cmH2O-1.kg-1, FVC > or = 10 ml.kg-1. The mortality in the Group C was significantly higher than in the Group A and B, and the preoperative Crs and FVC values in the Group C were significantly lower than the other groups. The mortality in the Group D and E were significantly higher than the Group F. In conclusion, it is suggested that the preoperative Crs value less than 0.5 ml.cmH2O-1.kg-1 indicates severe pulmonary hypoplasia and is critical for survival.

Eosinophilic gastroenteritis with ileus and ascites.

We report a case of eosinophilic gastroenteritis, which has features of the predominant subserosal type presented as an ileus and ascites. A 48-year-old Japanese woman was admitted to our hospital because of epigastralgia, lower abdominal pain and vomiting. She had a past history of allergic disorders. The computed tomographic scan revealed ascites, and marked wall thickening and dilatation of the intestine. This patient showed eosinophilic ascites without marked peripheral eosinophilia. Histologic examination demonstrated eosinophilic infiltrates did not predominate in the gastrointestinal tract. Conservative treatment of intravenous infusion of antibiotics and Ringer's solution was effective in this case.

Comparison of the Jackson-Rees circuit, the pediatric circle, and the MERA F breathing system for pediatric anesthesia.

The purpose of this study was to compare the Jackson-Rees circuit with the pediatric circle and MERA F breathing system (MERA F system) for pediatric anesthesia from the viewpoint of work of breathing (WOB). Twenty-three children (2-10 yr old) were studied during spontaneous breathing under endotracheal anesthesia with 4 L/min nitrous oxide, 2 L/min oxygen, and 1% end-tidal concentration of sevoflurane. WOB, inspiratory and expiratory airway resistance, dynamic compliance (CDYN), pressure time product (PTP), and arterial blood gasses were measured in the three circuits. The inspiratory WOB was estimated directly by measuring the esophageal pressure-volume loop using the Campbell technique. In a laboratory study, we measured the compliances of the Jackson-Rees circuit, the pediatric circle, the MERA F system, and the adult circuit. WOB differed among the three circuits (MERA F system > pediatric circle > Jackson-Rees circuit). Inspiratory and expiratory resistances, and arterial carbon dioxide tension in the Jackson-Rees circuit were significantly lower than those of both the pediatric circle and MERA F system. The CDYN and PTP in the MERA F system were significantly higher than those in both the Jackson-Rees circuit and the pediatric circle. The MERA F system had significantly higher compliance than the Jackson-Rees circuit and pediatric circle. It is concluded that the Jackson-Rees circuit is most efficient, the pediatric circle is intermediate, and the MERA F system is the least efficient from the viewpoint of WOB during spontaneous breathing for pediatric anesthesia.

Regulation of the aortic valve opening. In vivo dynamic measurement of aortic valve orifice area.

Aortic valve orifice area was dynamically measured in anesthetized dogs with a new measuring system involving electromagnetic induction. This system permits us real-time measurement of the valve orifice area in beating hearts in situ. The aortic valve was already open before aortic pressure started to increase without detectable antegrade aortic flow. Maximum opening area was achieved while flow was still accelerating at a mean of 20 to 35 msec before peak blood flow. Maximum opening area was affected by not only aortic blood flow but also aortic pressure, which produced aortic root expansion. The aortic valve orifice area's decreasing curve (corresponding to valve closure) was composed of two phases: the initial decrease and late decrease. The initial decrease in aortic valve orifice area was slower (4.1 cm2/sec) than the late decrease (28.5 cm2/sec). Aortic valve orifice area was reduced from maximum to 40% of maximum (in a triangular open position) during the initial slow closing. These measurements showed that (1) initial slow closure of the aortic valve is evoked by leaflet tension which is produced by the aortic root expansion (the leaflet tension tended to make the shape of the aortic orifice triangular) and (2) late rapid closure is induced by backflow of blood into the sinus of Valsalva. Thus, cusp expansion owing to intraaortic pressure plays an important role in the opening and closing of the aortic valve and aortic blood flow.

Double-exponential curve fitting of isometric relaxation: a new measure for myocardial lusitropism.

New indexes for evaluation of isometric myocardial relaxation were proposed. In fully isometric and physiologically sequenced twitches, the time course of isometric force decline fitted well with Gompertz's double-exponential curve (r > or = 0.9995). We conformed the original equation to suit myocardial mechanics, i.e., F(t) = gamma 0 - gamma.exp [-alpha.exp (-beta t)] (t = 1, 2, ..., n), where F(t) denotes force as a function of time t. The gamma 0 and gamma relate to upper asymptote and force amplitude, respectively. Phase-plane analysis of F(t) revealed that alpha [3.56 +/- 0.67 (SD)] related to the phasic delay of relaxation onset but did not affect the F(t) vs. dF(t)/dt relation. The beta (0.127 +/- 0.021) and gamma were linearly related to negative dF(t)/dtmax; however, the terminal slope of the phase-plane diagram was governed by beta alone. The tau beta (0.081 +/- 0.017 s), a reciprocal of beta multiplied by sampling time, was practically independent of preload, total load, and muscle shortening. In isometric twitches, tau beta was substantially decreased by global ischemia, isoproterenol, and CaCl2 but increased by reperfusion. The alpha was independent of inotropic interventions but fell significantly during ischemia and was increased by reperfusion.

[Complications of pediatric spinal anesthesia].

We evaluated retrospectively the complications of pediatric spinal anesthesia in our center based on the histories of 50 spinal anesthesia cases (5-15 years of age, 0.56%) over the last 15 years. Five cases (10%) showed transient hypotension. In the prospective study of those under 5 years of age (35 children), there were no hypotensive cases, and the only critical complication was high spinal anesthesia; this case was complicated by giant hepatoblastoma. There was no obvious neurological damage in any of the patients who underwent spinal anesthesia. Because of low incidence of complications, pediatric spinal anesthesia is a useful method especially for patients with respiratory insufficiency. It is advisable to watch carefully for changes in blood pressure in senior infants, and to avoid spinal anesthesia in patients with giant abdominal tumors.

Role of the septal leaflet in tricuspid valve closure. Consideration for treatment of complete atrioventricular canal.

A septal leaflet of the tricuspid valve is thought to work differently from other anterior and posterior leaflets. We studied its role in valve closure in dogs by means of a dynamic area meter. During the control state, the tricuspid valve orifice area increased twice in diastole coincidentally with either atrial systole or rapid ventricular filling. We observed several findings after the septal leaflet resection: (1) two peak area patterns of the tricuspid valve orifice in diastole, (2) no elevation of right atrial pressure on ventricular systole (there was no V wave), (3) no tricuspid valve regurgitation on right ventriculography. These findings suggest that a complete valve closure occurred without the septal leaflet in regular sinus rhythm. An elevation of the right ventricular pressure produced by pulmonary artery stenosis without septal leaflet, however, easily caused tricuspid valve regurgitation in contrast to the same pressure of the right ventricle with the normal tricuspid valve. The right ventricular pacing caused severe valve regurgitation without the septal leaflet. Results indicate that in the repair of the complete atrioventricular canal defect and other tricuspid valve lesions, the septal leaflet of the tricuspid valve rarely requires attention. An atrioventricular block should be avoided, however, because electrical cardiac pacing on the right ventricle causes severe valve regurgitation without the septal leaflet.

[Utility of intra-bladder pressure monitoring during closure of abdominal wall defects in newborn infants].

Recently, it was demonstrated that intra-bladder pressure (IBP) measured through a transurethral catheter accurately reflects intra-abdominal pressure (IAP). We monitored IBP during closure of abdominal wall defects in three newborn infants with gastroschisis. We were able to avoid complications due to increased IAP by keeping IBP below 20 mmHg. IBP correlated well with inferior vena cava pressure (r = 0.93) which reflects IAP. We advocate the use of IBP monitoring as a simple and reliable means of indirectly determining IAP during operations for closure of abdominal wall defects in newborn infants with omphalocele or gastroschisis.

An in vivo area meter for real-time measurement of cross-sectional area in the cardiovascular system.

A direct real-time recording of the cross-sectional area of the heart valve is useful for the fluid dynamic study of the cardiovascular system. Electronic circuitry is described that is capable of driving the transmitter coil assembly placed outside the animal and detecting an area-related signal induced in the one-turn coil in vivo. When a piece of fine pliable metal thread encircles the area of interest (e.g. the mitral/aortic valve orifice) so as to form a single loop, the electrical potential between the ends of the loop is linearly related to the size of the area irrespective of its shape. The principle of measurement, construction of transmitter coil assembly, and simple but accurate direct calibration are also described.

Real-time and simultaneous measurement of tricuspid orifice and tricuspid anulus areas in anesthetized dogs.

Tricuspid valve orifice and tricuspid valve anulus areas were measured simultaneously in the anesthetized dog with a newly developed area-measuring system based on electromagnetic induction. This system permitted real-time monitoring of the area enclosed by the edges of valve leaflets and by the juncture of the valve leaflet and the cardiac wall in situ, without artificial constraint to the valve motion. Right atrial and right ventricular pressures were measured with two catheter-tipped micromanometers. During control state, tricuspid valve orifice area (TOA) increased up to its peak [1.38 +/- 0.26 cm2 (mean +/- SD)] coincidently with either atrial systole or rapid ventricular filling. Atrial contraction evoked distinct presystolic tricuspid anulus narrowing with concomitant slow TOA reduction. This slow TOA reduction began 30.0 +/- 16.1 msec before systolic atrioventricular pressure crossover, and the following rapid TOA decrease was completed 38.7 +/- 12.2 msec after systolic atrioventricular pressure crossover. TOA began to increase 48.4 +/- 30.4 msec before diastolic atrioventricular pressure crossover at the end portion of the isovolumic relaxation phase, opposing residual transvalvular pressure gradient (3.33 +/- 1.79 mm Hg). The slow presystolic TOA decrease was considered to be a reflection of the presystolic anulus narrowing caused by atrial systole. An isolated atrial contraction induced by administering 1 mg acetylcholine chloride into the atrioventricular node artery or by vagus nerve stimulation could produce complete valve closure. Even in an isolated atrial contraction, the inflection point that marks the boundary between slow "atriogenic" closure presumably due to anulus narrowing and rapid closure presumably due to hemodynamic force was easily identified.

[Experimental study on the optimal size of the tricuspid valve annular area on annuloplasty].

The optimal size of tricuspid valve annular area (TVAA) by annuloplasty for tricuspid regurgitation remains controversial. Recently, we developed a new measuring system which permits to do real-time measurement of tricuspid valve annular area in anesthetized dogs. Using this system, we studied the optimal size of TVAA by annuloplasty. After the right atrial incision, a metal thread which functions as a sense loop of the electromagnetic fields was stitched along the tricuspid valve annulus (visible juncture of the valve leaflets and the cardiac wall). The drive coil assembly was placed perpendicular to the extension of the long axis of the heart and was directed toward the tricuspid valve region. During control conditions, the maximum TVAA appeared at the onset of ventricular systole. The minimum TVAA appeared during the early ventricular diastolic phase which included the ventricular isovolumic relaxation phase. The maximum TVAA varied in five dogs between 2.2 cm2 and 3.1 cm2, the minimum TVAA also varied between 1.8 cm2 and 2.5 cm2: During regular sinus rhythm, a decrease of TVAA during one cardiac cycle ranged between 11.9% and 22.4% of the maximum size. When TVAA was not decreased by annuloplasty to the minimum area which was observed during cardiac cycle in the control state, the cardiac output and the right atrial pressure remained unchanged, because the ventricular filling was not obstructed. On the other hand, when TVAA was decreased smaller than this minimum area, the cardiac output decreased and the right atrial pressure rose.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro analysis of performance of porcine xenografts with inward bending of stent posts: real-time measurement of valve orifice area using an area meter.

The influence of inward bending of the stent posts on bioprosthetic valve function was assessed in a hydromechanical simulation of the left heart. A Carpentier-Edwards mitral xenograft (31 mm) and an aortic xenograft (27 mm) were used. Valve function was evaluated before and after the stent posts were bent inward 15 degrees by suture constriction of the tops of the three posts. To evaluate the effects of the stent-post deformity on valve performance, the mean transvalvular pressure drop during steady flow, the bioprosthetic valve orifice area, and the maximum valve opening and closing speeds during pulsatile flow were measured using an area meter. Steady-flow data showed identical transvalvular pressure drops, and no significant difference in valve performance was detected in the pulsatile-flow study under the two experimental conditions (i.e., normal valve and deformed valve). We conclude that a 15-degree inward bending of the stent posts does not appreciably affect valve function in vitro.

Real-time measurement of tricuspid valve annular area for annuloplasty. Experimental study.

We used real-time measurement of the tricuspid valve annular area in anesthetized dogs to study the optimal size of the annular area for annuloplasty. During control conditions, the maximum tricuspid annular area appeared at the onset of ventricular systole. The minimum tricuspid annular area appeared between the ventricular isovolumic relaxation phase and the early ventricular filling phase. The maximum annular area varied in seven dogs between 2.18 and 3.10 cm2, and the minimum annular area ranged between 1.68 and 2.45 cm2. In regular sinus rhythm (heart rates 97 to 120 beats/min), the maximal decreases in tricuspid annular area during one cardiac cycle ranged from 14.3% to 23.6% of the maximum size. When the tricuspid annular area after the annuloplasty was kept larger than the minimum area that was observed during the cardiac cycle in the control study, cardiac output and right atrial pressure remained unchanged, as a result of unobstructed ventricular filling. On the other hand, when the annular area was reduced to smaller than the minimum area seen in the control study, a decrease in cardiac output and an elevation of right atrial pressure ensued. These findings suggest that the tricuspid annular area can be safely decreased by annuloplasty to the minimum area seen in the control study without causing a reduction of cardiac output or an elevation of right atrial pressure.