Continuous positive airway pressure during fiberoptic bronchoscopy in hypoxemic patients. A randomized double-blind study using a new device.

Fiberoptic bronchoscopy (FOB) may worsen oxygenation and clinical status in severely hypoxemic patients. We conducted a prospective, randomized double-blind trial to compare the delivery of continuous positive airway pressure (CPAP) as a tool for maintaining oxygenation during FOB, to the delivery of oxygen only. Thirty consecutive patients who needed FOB for diagnostic purposes were enrolled. Their arterial oxygen pressure (Pa(O(2))) to inspired oxygen fraction (FI(O(2))) ratio was below 300 mm Hg. CPAP was generated by a simple new device open to the atmosphere. During FOB and the 30 min thereafter, pulse oximetry values (Sp(O(2))) were significantly higher in the CPAP than the Oxygen group (95.7 +/- 1.9% versus 92.6 +/- 3.1, p = 0.02). The lowest Sp(O(2)) values were observed in the Oxygen group (93.5 +/- 2.4% versus 88.6 +/- 3.4, p = 0.002). Arterial blood gases 15 min after FOB showed that Pa(O(2)) had increased in the CPAP group and decreased in the Oxygen group (DeltaPa(O(2)) = +10.5% +/- 16.9 versus -15% +/- 16.6, p = 0.01). Five patients in the Oxygen group, but none in the CPAP group, developed respiratory failure in the 6 h after FOB and required ventilatory assistance (p = 0.03). We conclude that in hypoxemic patients, the use of a new CPAP device during FOB allowed minimal alterations in gas exchange and prevented subsequent respiratory failure.

Efficacy of continuous insufflation of oxygen combined with active cardiac compression-decompression during out-of-hospital cardiorespiratory arrest.

BACKGROUND: During experimental cardiac arrest, continuous insufflation of air or oxygen (CIO) through microcannulas inserted into the inner wall of a modified intubation tube and generating a permanent positive intrathoracic pressure, combined with external cardiac massage, has previously been shown to be as effective as intermittent positive pressure ventilation (IPPV). METHODS: After basic cardiorespiratory resuscitation, the adult patients who experienced nontraumatic, out-of-hospital cardiac arrest with asystole, were randomized to two groups: an IPPV group tracheally intubated with a standard tube and ventilated with standard IPPV and a CIO group for whom a modified tube was inserted, and in which CIO at a flow rate of 15 l/min replaced IPPV (the tube was left open to atmosphere). Both groups underwent active cardiac compression-decompression with a device. Resuscitation was continued for a maximum of 30 min. Blood gas analysis was performed as soon as stable spontaneous cardiac activity was restored, and a second blood gas analysis was performed at admission to the hospital. RESULTS: The two groups of patients (47 in the IPPV and 48 in the CIO group) were comparable. The percentages of patients who underwent successful resuscitation (stable cardiac activity; 21.3 in the IPPV group and 27.1% in the CIO group) and the time necessary for successful resuscitation (11.8 +/- 1.8 and 12.8 +/- 1.9 min) were also comparable. The blood gas analysis performed after resuscitation (8 patients in the IPPV and 10 in the CIO group) did not show significant differences. The arterial blood gases performed after admission to the hospital and ventilation using a transport ventilator (seven patients in the IPPV group and six in the CIO group) showed that the partial pressure of arterial carbon dioxide (PaCO2) was significantly lower in the CIO group (35.7 +/- 2.1 compared with 72.7 +/- 7.4 mmHg), whereas the pH and the partial pressure of arterial oxygen (PaO2) were significantly higher (all P < 0.05). CONCLUSIONS: Continuous insufflation of air or oxygen alone through a multichannel open tube was as effective as IPPV during out-of-hospital cardiac arrest. A significantly greater elimination of carbon dioxide and a better level of oxygenation in the group previously treated with CIO probably reflected better lung mechanics.

[Effect of biflow-induced ventilation (BIFIV) on cerebral cortical blood flow in anesthesized rabbits with intracranial hypertension]. / Effet de la ventilation biphasique (BIFIV) sur le débit sanguin cérébral cortical du lapin anesthésié soumis à une hypertension intracrânienne.

This study compared the effect of biflow-induced ventilation (BIFIV) and conventional mechanical ventilation (CMV) on cerebral cortical blood flow (CBF) of six anaesthetized rabbits with an intracranial pressure (ICP) at 45 mmHg. BIFIV did not improve CBF during increased ICP when compared to CMV.

Efficacy of cardiopulmonary resuscitation using intratracheal insufflation.

The effects of constant-flow insufflation (CFI) of air in the trachea at the distal end of a modified endotracheal tube as the sole mode of ventilation during cardiopulmonary resuscitation (CPR) were studied in pigs. The ventilatory effect of CFI (15 +/- 2 L/min) generating a positive pressure of about 10 cm H2O with concomitant chest compression was studied first. In nine sedated, paralyzed animals disconnected from the ventilator, CFI alone did not significantly alter the decrease in PaO2 and the rise in PaCO2 observed during apnea. By contrast, the combination of precordial compression and CFI (CFI-CPR) maintained arterial blood gases over a 4-min period at the level obtained during mechanical ventilation. In the second part of the study, ventricular fibrillation was induced and CFI-CPR was compared with standard CPR using conventional mechanical ventilation during two successive 4-min periods, in random order. Ventilatory parameters were identical in the two situations, whereas hemodynamic parameters were similar or better with CFI-CPR than with standard CPR. Significant differences were observed between standard CPR and CFI-CPR for systolic aortic pressure (72 +/- 22 versus 82 +/- 27 mm Hg, respectively; p < 0.02) and for systolic (322 +/- 216 versus 431 +/- 237 ml/s; p < 0.01) and mean (116 +/- 106 versus 143 +/- 108 ml/s; p < 0.01) common carotid blood flows. The ease of use of CFI together with its beneficial hemodynamic effects suggests that CFI deserves to be investigated further as a mode of ventilation during CPR.

Benefits of the low pressure multichannel endotracheal ventilation.

Mechanical ventilation using a modified endotracheal tube, allowing bypass and washout of the endotracheal dead space (McETV), was compared with conventional controlled mechanical ventilation (CMV) in healthy and in surfactant-depleted rabbits. In healthy animals, shifting from CMV to McETV led to an increase in PaO2 (89 +/- 16 versus 104 +/- 13 mm Hg; p < 0.05) and a decrease in PaCO2 (41.5 +/- 3 versus 30 +/- 3 mm Hg; p < 0.05). As a result of reducing the peak inspiratory pressure (PIP) from 21 +/- 2 to 12 +/- 2 cm H2O (p < 0.05), it was possible in McETV mode to maintain comparable ventilation to that achieved by CMV. In surfactant-depleted animals, compared with CMV, McETV produced a rise in PaO2 without change in thoracic volume (from 100 +/- 40 to 150 +/- 60 mm Hg, p < 0.05) and a fall in PaCO2 (from 46 +/- 5 to 37 +/- 4 mm Hg, p < 0.05). After 4 h of ventilation, the surfactant-depleted animals from the CMV group developed thoracic overdistension quicker (at hour 1, p < 0.05) and, consequently, more animals died from pneumothorax compared with the McETV group (five versus two). We concluded that McETV ensured adequate gas exchanges with lower insufflation pressures and could diminish positive pressure ventilation-induced injury.

Comparison of ablation efficacy of excimer, pulsed-dye, and holmium-YAG lasers relevant to shock waves.

Ablation efficacy of pulsed lasers on human arterial tissue and associated shock waves have been investigated by means of excimer laser at 308 nm, pulsed-dye laser at 480 nm, and holmium-YAG laser at 2.1 microns. A multifiber catheter was used for lasing at 420 mjoules/pulse with holmium-YAG, 18.9 mjoules/pulse with excimer, and 100 mjoules/pulse with pulsed-dye laser. Ablation efficiency (ablated volume/energy) was greatest with pulsed-dye laser in blood and excimer laser in saline solution. There was selectivity for atheroma with pulsed-dye laser (ablation efficiency in atheroma versus normal tissue, 58 versus 27 x 10(-2) mm3/joule in blood; p less than 0.005) and holmium-YAG laser (12.6 versus 5.6 x 10(-2) mm3/joule in blood; p less than 0.001). Ablation efficiency of pulsed-dye laser was enhanced by blood (0.58 in blood versus 0.17 mm3/joules in saline for atheroma; p less than 0.005). Shock waves were correlated with ablation efficiency (r = 0.63 and 0.74 for pulsed-dye laser and holmium-YAG laser, respectively). There was neither selectivity for atheroma nor influence of blood medium with excimer laser. Only holmium-YAG laser could ablate tissue at a distance from the target in the blood medium. Histologic findings showed that all lasers could create smooth-edged craters with minimal coagulation necrosis. In conclusion, laser irradiation with holmium-YAG and pulsed-dye lasers could selectively ablate atheromatous tissue with minimal thermal injury, whereas excimer laser could not. Ablation efficiency was correlated with shock waves. Efficiency of pulsed-dye laser was enhanced by blood.

Characteristics of shock waves induced by pulsed lasers and their effects on arterial tissue: comparison of excimer, pulse dye, and holmium YAG lasers.

Shock waves were investigated using an excimer laser at 308 nm with 18.9 mjoules/pulse, a pulsed dye laser at 480 nm with 100 mjoules/pulse, and a holmium YAG (yttrium-aluminum-garnet) laser at 2.1 microns with 420 mjoules/pulse. At a distance from the target tissue, excimer lasing resulted in no shock waves in saline, while the other lasers produced smaller shock waves than those recorded when the laser was in contact with tissue (0.22 versus 2.0 mm Hg with the pulsed dye laser, 0 versus 0.23 mm Hg with the excimer laser, and 0.44 versus 6.9 mm Hg with the holmium YAG laser; p less than 0.001, respectively). In blood, excimer laser irradiation at a distance from the tissue produced shock waves as great as those produced when the laser was in contact with the tissue (0.19 versus 0.24 mm Hg with the excimer laser, 1.8 versus 3.0 mm Hg with the pulsed dye laser, and 3.1 versus 5.9 mm Hg with the holmium YAG laser; p less than 0.001 with the pulsed dye and holmium YAG lasers, respectively). When lasing was done at 60 mjoules/mm2, the pulsed dye and excimer lasers produced similar shock waves when the lasers were in contact with tissue; however, the holmium YAG laser did not produce shock waves. Thus pulsed lasers can produce shock waves of different characteristics according to the laser source.

Pressure support ventilation using a new tracheal gas injection tube.

In order to explore new types of jet ventilation, we tested a tracheal gas injection tube (TGIT) which included six thin capillaries and provided high pressure injection. The driving pressure was chosen to yield a plateau of inspiratory tracheal pressure of 10 cm H2O. An original controller was built to monitor spirometry and trigger injection in order to deliver both pressure controlled ventilation (PCVTGIT) and a new mode of inspiratory pressure support jet ventilation (IPSTGIT). The PVCTGIT mode maintained the same end-tidal carbon dioxide concentration as conventional ventilation with the same tidal and minute ventilation. We studied 10 patients after abdominal surgery. During spontaneous breathing, the patients were allowed to breathe through the tube, successively with and without IPSTGIT. IPSTGIT, compared with spontaneous breathing increased minute ventilation (from 5.7 (SD 1.6) to 7.1 (1.7) litre min-1) (P less than 0.001). It reduced the total work of breathing (from 0.625 (0.223) to 0.263 (0.151) J litre-1, respectively) (P less than 0.01) and the occlusion pressure (from 2.62 (1.28) to 1.36 (0.74) cm H2O, respectively) (P less than 0.01). It is concluded that this TGIT used with a specific system for sensing and triggering ventilation allows inspiratory pressure support during low frequency jet ventilation.

[Results of pulsed laser angioplasty of peripheral arteries guided by spectroscopy]. / Résultats de l'angioplastie par laser pulsé guidé par spectroscopie des artères périphériques.

Seventy-six patients with complete occlusion of the iliac, femoropopliteal or distal arteries underwent laser angioplasty after failure of attempted mechanical recanalization by conventional angioplasty. The energy source was a dye pulsed laser emitting at 480 nm, 2 microseconds, 35 to 50 mJ/pulse and 5 Hz. The laser was coupled with an optical fiber of 200 microns diameter covered by a metallic spring. In order to center the laser in the arterial lumen, the fibre optic was introduced with a balloon catheter or a modified Van Andel catheter with a tapered and curved distal end with controlled torsion to direct the laser towards the lesion to be treated. The therapeutic laser was connected to a diagnostic Helium-Cadmium laser emitting at 325 nm, 50 ms and 5 mW, for the induction of tissue fluorescence analysed by a multichannel detector, itself connected to a computer programmed to differentiate atheromatous from normal tissues. The therapeutic laser was only activated when atheromatous tissue was in contact with the distal tip of the fiber optic. After vaporizing a narrow pilot channel conventional balloon angioplasty was performed. The immediate success rate was 83%; it was higher in iliac than in femoral arteries. This was less dependent on the length of occlusion than on the presence of calcification which was a common cause of failure. The complications were immediate reocclusion, perforation due to the sharp tip of the fibre and dissections without major clinical consequences. After 18 months, 64% of the arteries remained patent.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of pulsed-dye laser ablation of arterial tissues with blood medium: effects of laser-induced shock waves.

The influence of blood medium on tissue ablation by a pulsed dye laser and its selectivity for atheroma were investigated. The role of shock waves on tissue ablation was also evaluated. Normal and atherosclerotic human aortas were irradiated by a 480 nm pulsed dye laser activated at 5 Hz. The laser was coupled with a single 0.2 mm fiber (Uni-guide) (40 mjoules/pulse) or a multifiber catheter (14 x 150 microns) (100 mjoules/pulse). Shock waves were measured using a fluid-filled catheter connected to a strain gauge manometer. With the Uni-guide, pulse-dye lasing resulted in greater ablation of atheroma in blood (11.6 x 10(-3) mm3/joule, p less than 0.001 versus atheroma measured in saline and normal tissue in blood) followed by normal tissue in blood (2.5 x 10(-3)mm3/joule), atheroma in saline (1.71 x 10(-3)mm3/joule, p less than 0.05 versus normal tissue in saline), and normal tissue in saline (0.54 x 10(-3) mm3/joule). With the multifiber catheter, laser ablation was the greatest in atheroma in blood (0.55 +/- 0.26 mm3/joule p less than 0.001 versus atheroma in saline and normal tissue in blood), followed by normal tissue in blood (0.27 +/- 0.12 mm3/joule), atheroma in saline (0.14 +/- 0.15 mm3/joule, p less than 0.001 versus normal tissue in saline), and normal tissue in saline (0 mm3/joule). The ablation efficiency of the multifiber catheter was greater than that of the Uni-guide (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous coronary mid-infra-red laser angioplasty.

A pilot study was performed to determine the safety and efficacy of coronary pulsed mid-infra-red laser angioplasty. The laser was coupled with a novel 2.0 mm multifiber catheter consisting of 37 optical fibers of 150 microns each arranged concentrically around a 0.018-inch central lumen and a soft leading tapered distal tip to maintain coaxial alignment and position plaque in front of fibers. The laser was operated at 500 millijoules/pulse, 3.5 Hz, and 250 microseconds/pulse. Twenty-three patients with stenosis or occlusion of the left anterior descending or right coronary artery were selected for laser treatment. In three patients the catheter could not be positioned against the obstruction. In the 20 remaining patients laser angioplasty increased the diameter of the lumen from 0.3 +/- 0.3 mm to 1.4 +/- 0.3 mm and reduced the stenosis from 91 +/- 8% to 57 +/- 10%. In three patients "stand-alone" laser treatment was sufficient. In 17 patients balloon dilatation further reduced the stenosis to 20 +/- 18%. In two patients who had previously undergone unsuccessful balloon angioplasty with high inflation pressure, laser angioplasty allowed subsequent successful dilatation with low inflation pressure. There were no deaths, perforations, dissections, or arrhythmias. One patient had abrupt reclosure 24 hours after the procedure. Spasm occurred in four patients, and six patients had chest sensations during laser emission. Thus mid-infra-red pulsed coronary laser angioplasty is safe and effective for recanalization of stenosed and totally occluded arteries. The efficacy may be sufficient for "stand-alone" laser treatment. The technique may improve the efficacy of balloon angioplasty in cases of unsuccessful primary dilatation.

Constant-flow insufflation prevents arterial oxygen desaturation during endotracheal suctioning.

In mechanically ventilated patients, disconnection from the ventilator and endotracheal suctioning can induce major arterial oxygen desaturation resulting from apnea, changes in inspired oxygen fraction, and decrease in lung volume. The aim of this study was to test the efficacy of a simple method of delivering oxygen and maintaining lung volume during this process. Our study was conducted in two parts. In the first part, constant-flow insufflation of oxygen (CFI) was used in seven patients ventilated for acute respiratory failure (PaO2/FlO2 = 347 +/- 33 mm Hg) as a means of maintaining arterial oxygenation during apnea and disconnection from the ventilator. CFI was administered via a modified endotracheal tube in which small capillaries allowed delivery of a high-velocity jet flow near the tracheal end of the tube during disconnection from the ventilator. In comparison to apnea alone, CFI prevented a fall in arterial oxygen tension (16 +/- 7 mm Hg during CFI versus 117 +/- 27 during apnea, after 90 s of disconnection in the two situations, p less than 0.001), whereas it did not reduce the development of hypercapnia. The efficacy of CFI resulted both from the injection of oxygen into the trachea and from the maintenance of positive alveolar pressure induced by air entrainment (mean 10.4 +/- 1.1 cm H2O), preventing a fall in lung volume usually occurring after disconnection (+338 +/- 88 ml during CFI versus -344 +/- 64 ml during apnea, p less than 0.01). In the second part of the study CFI was used to prevent arterial oxygen desaturation induced by endotracheal suctioning.(ABSTRACT TRUNCATED AT 250 WORDS)

Results and follow-up after percutaneous pulsed laser-assisted balloon angioplasty guided by spectroscopy.

BACKGROUND: Few data are available on the long-term outcome of patients who undergo laser-assisted balloon angioplasty for recanalization of occluded peripheral arteries. Because the cost of laser angioplasty is high, the value of the method should be carefully analyzed before it can be considered a routine method for recanalization. The purpose of this study was to evaluate the early and late results of laser-assisted balloon angioplasty in patients who could not be recanalized by conventional techniques. METHODS AND RESULTS: Laser angioplasty was performed in 66 patients with total occlusion of the iliofemoral artery in whom mechanical techniques failed to recanalize the obstructed vessel. The system consisted of a pulsed dye laser operated at 480 nm, 2 microseconds/pulse, 5 Hz, 50 mJ/pulse coupled into a 0.021-in. laser catheter. The treatment laser was connected with a diagnostic laser to induce tissue fluorescence for spectroscopic analysis via the same fiber. The treatment laser was emitted only when atheromatous tissue was recognized. After a pilot hole was created by laser emission, dilatation was performed to enlarge the channel. The mean length of occlusion was 8.8 +/- 6.1 cm. The primary success rate was 82%. It did not depend on the length of occlusion but was greater in non-calcified than in calcified lesions (88% versus 71%, p less than 0.03). Complications included seven early reocclusions that could be recanalized and eight perforations without clinical sequelae. At a mean 18-month follow-up, 64% of the laser-treated arteries remained patent. The rate of patency was related neither to the length of the occlusion nor to calcifications but was lower in patients who had early reocclusion (p less than 0.02). CONCLUSIONS: Pulsed dye laser-assisted balloon angioplasty is effective for recanalization of totally occluded arteries that cannot be treated by conventional means. The efficacy is limited by calcifications. The long-term patency rate is acceptable given the severity of the lesions.

Effect of air entrainment on airway pressure during endotracheal gas injection.

Turbulent jets in endotracheal tubes induce air entrainment and airway pressure changes. We attempted to understand the physical explanation for these effects, which open up to a wide range of applications in intubated patients. An in vitro study was performed on standard size endotracheal tubes with diameters of 8, 7, and 3 mm and several capillaries molded into the wall (less than 1 mm diam) allowing gas injection at approximately 1-2 cm from the tracheal end of the endotracheal tube. This produced a jet velocity-dependent gain in tracheal pressure (Ptr) during inspiration. Data have been interpreted with a theory, based on the classic momentum theorem, which indicates that the mechanisms involved resemble those of axisymmetrical confined jets: air entrainment by turbulent friction with a longitudinal increase in lateral pressure. The difference with axisymmetrical systems lies in the nonconservation of the total thrust in our system because, secondary to wall friction and to the nonaxial incidence of the jets, only a fraction of the jet momentum flux is transformed into pressure. This suggests faster mixing in the present lateral jet system, as shown by 1) the independence of Ptr on tracheal geometry and 2) the very rapid increase in lateral pressure. The present study supports the idea that pressure changes in the airways, which are potentially beneficial in intubated patients, can be satisfactorily generated by turbulent jets.

Percutaneous pulsed laser-assisted balloon angioplasty guided by spectroscopy.

Percutaneous laser angioplasty was performed in 19 patients with total superficial femoral calcified and noncalcified (4 to 25 cm length) occlusions; a pulsed dye laser of 480 nm was used with a pulse duration of 2 musec/pulse. The treatment laser was guided by a 325 nm diagnostic laser that induced fluorescence. The laser system operated through a single 200 or 500 microns optical fiber. Computerized spectral analysis of the tissue fluorescence located at the distal of the fiber tip allowed the treatment laser to be emitted on the atheroma and not on the arterial wall. Uniform success in primary laser recanalization was demonstrated, which allowed for subsequent balloon dilatation in all but one patient. One mechanical fiber perforation, two mechanical fiber dissections, one guidewire perforation, and one guidewire dissection occurred, but no complications resulting from the treatment or diagnostic laser were observed. The safety of the procedure appears to be enhanced by the spectroscopic guidance system, which allows recognition of plaque. The pulsed dye treatment laser was well tolerated and effective even in heavily calcified arteries.

[Percutaneous angioplasty using spectroscopy-guided pulsed laser]. / Angioplastie percutanée par laser pulsé guidé par spectroscopie.

Percutaneous laser angioplasty was performed in 19 patients with calcified and non-calcified occlusions (4-25 cm long) of the superficial femoral artery, using a pulsed dye laser at 480 nm and a pulse duration of 2 microseconds per pulse. The treatment laser was guided by a 325 nm diagnostic laser that induced tissue fluorescence. The laser system operated through a single 200 microns optical fiber. Computer spectral analysis of the tissue fluorescence located at the distal end of the fiber tip directed emission of the treatment laser only at the atheroma without affecting the arterial wall. A successful primary laser recanalization was obtained in all cases and was followed by balloon dilation in all but one patient. One mechanical perforation and 2 mechanical arterial dissections by the fiber, and 1 perforation and 1 dissection by the guide wire occurred, but no complications due to the treatment or diagnostic laser were observed. The safety of the procedure seemed to be enhanced by the spectroscopic guidance system which enabled plaque recognition. The pulsed dye treatment laser was well tolerated and effective even in heavily calcified arteries.

[Myocardial protection by coronary autotransfusion during angioplasty]. / Protection myocardique par autotransfusion coronaire au cours de l'angioplastie.

Coronary autologous blood perfusion may protect the myocardium against ischemia during arterial occlusion due to balloon inflation. During balloon inflation, arterial blood was perfused via the balloon catheter in 19 patients with single proximal severe left anterior descending artery stenosis and normal left ventricular function. Blood was perfused using a contrast medium injector at a flow rate of 40 ml/min. The balloon was maintained inflated for 60 seconds at 6 atmospheres. Two inflations were performed with perfusion and 2 without. Myocardial ischemia was assessed by ST elevations on both the peripheral and intracoronary ECGs, changes in left ventricular systolic and end diastolic pressures and peak positive and negative dP/dt. A positive response was obtained in 11 patients. In 5 patients, the myocardial ischemia induced by dilatation was not alleviated by the perfusion and in 3 patients ischemia was increased by perfusion. In conclusion, ischemia is inconsistently reduced by autologous blood perfusion and its adverse effect in some patients could limit its use.