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The usual treatment of snoring in the absence of sleep apnea has been uvulopalatopharyngoplasty (UPPP). Patients are often reluctant to undergo this painful procedure, which must be performed under general anaesthesia. A new procedure, introduced 5 years ago by the author, called LAUP (laser-assisted uvulopalatoplasty), can be used to treat the pharyngeal airway obstruction that produces snoring during sleep. LAUP is performed with CO2 laser under local anaesthesia. LAUP produces a progressive enlargement of the oropharyngeal airspace that reduces or eliminates airway collapse during sleep, and it allows surgery for the relief of snoring to be performed in the office under local anaesthesia. LAUP has many advantages over the traditional UPPP. It is simple, reliable, hemostatic, and less painful. It is also less expensive, as it can be performed on an outpatient basis. This makes the LAUP more accessible to patients. Our experience with LAUP in 741 patients treated from December 1988 to December 1993 (121 women and 620 men) is described. Good results were obtained in 95% of patients, and there were no complications. This new technique can be easily performed by other otolaryngologists after suitable training. LAUP provides a simple alternative for many patients who do not wish to undergo a traditional UPPP. The method and its results are discussed.
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PMID:Outpatient treatment of snoring with CO2 laser: laser-assisted UPPP. 789 66

The traditional practice of using high inflation pressures to maintain normal tidal volumes and arterial blood gases has been encouraged by the perception of uniformly distributed damage in acute lung injury. Although the frontal chest radiograph often suggests uniformity, recent work highlights the heterogeneous pathoanatomy and lung mechanics that actually characterize the adult (acute) respiratory distress syndrome. This heterogeneity is important to consider when applying mechanical ventilation, because impressive experimental evidence strongly indicates the potential for traditional selections for volume and pressure to impede lung healing or extend damage to previously unaffected areas. Because lung regions differ markedly with regard to distensibility and fragility, the acutely injured lung should be viewed as small rather than stiff. Aerated lung units appear to have nearly normal gas-to-tissue ratios and well-preserved mechanical and gas-exchanging properties. Mechanical ventilation may expose endothelial and epithelial barriers to excessive stress, allowing proteinaceous alveolar edema to form without actual membrane rupture. Such damage has been linked experimentally to an excessive transalveolar inflation pressure, to a tidal volume inappropriate to the size of the aeratable lung mass, or to damaging shear forces that develop when insufficient end-expiratory alveolar pressure is maintained to prevent tidal opening and reclosure of susceptible alveoli. Pathologic, physiologic, and theoretical arguments favor a strategy that attempts to avoid tidal alveolar collapse and to keep transalveolar pressure (not PaCO2) within normal physiologic limits. CO2 retention may be an unavoidable consequence of such a lung-protection strategy. Although the traditional paradigm for ventilation appears in need of revision, it must be recognized that few prospective, controlled trials of alternative ventilation modes have been undertaken to prove their superiority.
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PMID:New options for the ventilatory management of acute lung injury. 808 70

Correct inflation of the cuff of any breathing tube is important; overinflation can damage the mucosa of the tracheobronchial tree and underinflation will cause a leak. Three different techniques to determine cuff seal/leak during inflation of the bronchial cuff of left double-lumen endobronchial tubes (DLT) were each evaluated in 10 patients. DLT size was chosen from a formula based on the patient's height and sex. In the first technique, designated the positive pressure technique of bronchial cuff inflation (PPT), the bronchial side of the DLT is pressurized during connection of the tracheal side to a beaker of water. Air bubbles will appear in the beaker in the absence of bronchial seal. The second technique, designated the CO2 analysis technique of bronchial cuff inflation (CAT), is based on analysis of CO2 content of gas sampled from the tracheal side of the DLT during ventilation of its bronchial side. When the bronchus is sealed, the normal CO2 waveform changes to a flat line. In the third technique, designated the negative pressure technique of bronchial cuff inflation (NPT), suction is applied to the tracheal side of the DLT. The absence of bronchial seal will result in collapse of the reservoir bag within a breathing system connected to the bronchial side of the tube. The bronchial sealing volumes were 1.1 +/- 0.9 mL, 0.9 +/- 0.7 mL, and 0.3 +/- 0.4 mL (mean +/- SD) when measured with the PPT, CAT, and NPT, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of three techniques to inflate the bronchial cuff of left polyvinylchloride double-lumen tubes. 821 39

A computer model of gas uptake from an area of nonventilated lung, such as a pulmonary lobe with an occluded bronchus or an alveolus with an occluded airway, is presented. Previous analyses have assumed that when an inert gas is present, equilibration of O2 and CO2 with mixed venous blood is sufficiently rapid to be treated as instantaneous. This is valid for insoluble gases such as N2 or He when the fractional concentration of inspired O2 (FIO2) is < or = 0.6 but is invalid for a relatively soluble gas such as N2O. When a mixture of O2 and an inert gas is breathed, the time for an area of unventilated lung to collapse depends on the solubility of the inert gas and FIO2. When the solubility is low (N2 or He), collapse takes longer than when 100% O2 is breathed, and the lower the FIO2 the longer the time to collapse. When the gas is more soluble (N2O) and FIO2 is > 0.3, collapse is more rapid than when 100% O2 is breathed.
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PMID:Gas uptake from an unventilated area of lung: computer model of absorption atelectasis. 848 48

Our purpose is to develop a survival strategy for man trapped in a confined space. We used immature pigs to assess the applicability of findings in rats for a larger mammal. The pig consumed oxygen in a sealed chamber until hypoxic collapse. We measured blood pressure, oxygen consumption, inspired O2 and CO2, minute ventilation, ECG and body temperatures, in three groups: no accumulation of CO2; CO2 level maintained at 5%, and maximal accumulation of CO2. Hypoxic oxygen consumption and ventilation were affected by the presence of CO2. Despite the pig's body mass being two orders of magnitude greater than that of the rat, its terminal PIO2 (35.9 torr) did not differ from that of the rat (35.3 torr). Accumulation of CO 2 had no significant effect on the terminal PIO2.
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PMID:Effect of accumulation of CO2 on the survival of immature pigs in a confined atmosphere. A: Gas exchange. 856 75

As part of a study for developing survival strategy for humans in a confined space, we used immature pigs to assess the applicability of findings in rats and to evaluate the effect of body size. The cannulated unanesthetized animal was placed in a sealed chamber and depleted the oxygen until hypoxic collapse. Three groups were: no accumulation of CO2, CO2 maintained at 5%, and maximal accumulation of CO2. In hypoxia arterial and venous oxygen tension were higher in the pigs exposed to CO2 than in the no CO2 pigs. Oxygen extraction increased and oxygen transport decreased in hypoxia in the presence of CO2. Similarity in the P50 of the oxygen dissociation curve may explain the similar terminal PIO2 in the pig and the rat. There was a positive correlation between terminal PIO2 and terminal venous pH.
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PMID:Effect of accumulation of CO2 on the survival of immature pigs in a confined atmosphere. B: Blood gas exchange. 856 76

Subtotal carbon dioxide (CO2) laser arytenoidectomy for endoscopic treatment of bilateral immobility of the vocal folds in adduction is a variant of total arytenoidectomy. The principal modification involves preservation of a thin posterior shell providing good postoperative fixation of the arytenoid region. The risk of aspiration is thus averted and collapse of arytenoid mucosa into the larynx during inspiration is prevented. The risk of synechia with the posterior commissure is avoided. The CO2 laser is operated at a working distance of 400 mm with a continuous 7-W beam in superpulse mode. Operation time is thus reduced to approximately half an hour and the risk of postoperative edema is reduced. Tracheotomy is not necessary. Forty-one patients, including 16 men and 25 women, were treated by this technique between 1985 and 1994. Their mean age was 55 +/- 17 years, ranging from 11 to 83 years. Follow-up ranged from 1 month to 111 months (9 years 3 months), with a mean of 56 +/- 29 months (4 years 8 months). The mean peak forced expiratory flow-peak inspiratory flow ratio (normal = 1), which permits a measurement of respiratory quality, is improved from 3.7 +/- 1.4 preoperatively to 1.6 +/- 0.5 postoperatively (p<.001). Postoperative voice measurements show a mean vocal intensity of 61 +/- 3 dB hearing level, a mean maximum phonation time of 8 +/- 4 seconds, and a mean phonation quotient of 397 +/- 150 mL/s. As for vocal quality, 38% of the patients now have a near-normal voice according to our high-resolution frequency analysis, and all of the patients retained satisfactory voice quality.
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PMID:Subtotal carbon dioxide laser arytenoidectomy by endoscopic approach for treatment of bilateral cord immobility in adduction. 863 94

We have compared cardiorespiratory variables in anaesthetized piglets whose lungs were ventilated with oxygen in nitrous oxide (N2O group) or nitrogen (N group) after right ventricular carbon dioxide boluses (0.5 or 1 ml kg-1; n = 12) or slow graded injections (n = 6). Boluses affected all variables studied significantly (P < 0.05) except mean systolic arterial pressure. Significant changes in PE'CO2 (P = 0.012) and PaO2 (P = 0.048) values were observed in the N2O group. Changes in PaCO2 were related to volumes of injected carbon dioxide (P = 0.044). Boluses of 1.0 ml kg-1 induced severe circulatory collapse in two piglets in the N2O group. Slow embolization altered respiratory variables significantly (P < 0.001)). PaO2 decreased significantly in the N2O group (P < 0.0001). Mean pulmonary arterial pressure increased significantly over time (P = 0.001) and lasted longer in the N2O group (P < 0.05). Volumes and time required to induce a 50% increase in mean pulmonary arterial pressure differed significantly between groups (P < 0.05). We conclude that nitrous oxide worsened the effects of rapid and slow carbon dioxide emboli on cardiopulmonary variables. Rapid carbon dioxide embolism altered respiratory and haemodynamic variables, while slow carbon dioxide embolism changed only respiratory variables.
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PMID:Effects of carbon dioxide embolism with nitrous oxide in the inspired gas in piglets. 901 42

Computed tomography (CT) has played an important role in improving our knowledge of the pathophysiology of the adult respiratory distress syndrome (ARDS), and in determining the morphological and functional relationships of different manoeuvres commonly used in the therapeutic management of this syndrome (changes in body position, application of positive end-expiratory pressure (PEEP) and mechanical ventilation). During the early phase of the disease, the ARDS lung is characterized by a homogenous alteration of the vascular permeability. Thus, oedema accumulates evenly in all lung regions with a nongravitational distribution (homogenous lung). The increased lung weight, due to increased oedema, causes a collapse of the lung regions along the vertical axis, through the transmission of hydrostatic forces (compression atelectasis). Thus, the lesions appear mainly in the dependent lung regions (dishomogeneous lung). During inspiration, at plateau pressure, the pulmonary units reopen and, if the PEEP applied is adequate, they stay open during the following expiration. Adequate PEEP is equal to or higher than the hydrostatic forces compressing that unit. Prone position is another manoeuvre which allows previously collapsed lung regions to reopen and, conversely, compresses previously aerated regions, reversing the distribution of gravitational forces. During late ARDS, there is less compression atelectasis and the lung undergoes structural changes, due to the reduced amount of oedema. This is usually associated with CO2 retention and the development of emphysema-like lesions. In conclusion, computed tomography is not only a research tool, but a useful technique which allows a better understanding of the progressive change in strategy needed to ventilate the adult respiratory distress syndrome lung at different stages of the disease.
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PMID:Computed tomography in adult respiratory distress syndrome: what has it taught us? 879 69

This report is the first to correlate data concerning intraoperative somatosensory evoked potentials (SSEPs) and local spinal cord blood flow (ISCBF) in patients with syringomyelia. In a consecutive study, bilateral median nerve SSEPs were recorded intraoperatively in 13 patients undergoing a syrinx shunt to the posterior fossa cisterns (syringocisternostomy). ISCBF was measured in five of these patients using laser doppler flowmetry (LDF) calibrated in arbitrary units (AU). SSEP recordings obtained 30 min after syrinx decompression demonstrated a slight but consistent reduction of N20 latencies (mean change: 0.53 ms right, p < 0.003; 0.58 ms left, p < 0.001) concurrent with a similar but less consistent increase of N20 amplitudes (0.16 mV right, p = 0.256; 0.29 mV left, p = 0.03). Prior to shunting, LDF recordings from the spinal cord overlying syrinxes revealed very low ISCBF values in five of five patients (mean LDF, 13.2 AU +/- 15.3 SD). Immediately after shunting, there was a dramatic rise of ISCBF (mean LDF, 241.2 AU +/- 106.3 SD) associated with visualized hyperemia of the spinal cord and pial vessels. The ISCBF fell to intermediate levels after 2 min (157.2 AU +/- 33.0 SD) and remained at these levels during the interval of recording (5 min). Hyperventilation testing in two patients prior to shunting revealed no change in ISCBF consistent with a loss of CO2 vascular reactivity and a paradoxical increase of ISCBF in one patient 5 min after shunting. Each patient in this study experienced neurological improvement in the immediate postoperative period associated with collapse or disappearance of the syrinx on magnetic resonance imaging scans. Because syrinx shunting results in an acute decompression of the distended spinal cord, it is possible that the rapid improvement of SSEPs reflects a relief of mechanical factors such as stretching and compression of nervous tissue. However, the LDF findings in this study suggest that distended spinal cord cavities are also capable of producing regional ischemia. A significant reduction of ISCBF is a possible contributing cause of neurological injury and SSEP abnormalities. Intraoperative improvement of SSEPs and ISCBF were found to correlate well with neurological recovery following syringocisternostomy. Our results indicate that SSEP monitoring can provide useful information during surgical procedures for syringomyelia and that further experience with LDF monitoring may provide insights into the pathophysiology of this condition.
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PMID:Intraoperative improvement of somatosensory evoked potentials and local spinal cord blood flow in patients with syringomyelia. 880 32


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