Chest
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Pressure support ventilation (PSV) is a pressure assist form of mechanical ventilatory support that augments the patient's spontaneous inspiratory efforts with a clinician selected level of positive airway pressure. To understand the effects of PSV on respiratory function, experiments were performed on 15 stable patients requiring synchronized intermittent mandatory ventilation (SIMV), as well as on a mechanical model simulating these patients' ventilatory systems. In the clinical study, gas exchange, airway pressures, blood pressure and heart rate were measured while SIMV was replaced by enough PSV to approximate the baseline SIMV tidal volume (VT). ⋯ It was found that PSV was a reasonable form of mechanical ventilatory support in patients with spontaneous ventilatory drives. It improves patient comfort, reduces the patient's ventilatory work, and provides a more balanced pressure and volume change form of muscle work to the patient. The clinical significance of these properties during the weaning process remain to be determined.
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Comparative Study
Hypercapnia in the obstructive sleep apnea syndrome. A reevaluation of the "Pickwickian syndrome".
The mechanisms of hypercapnia in eight patients with the "Pickwickian" syndrome and obstructive sleep apnea (OSAS) were evaluated pretherapy and posttherapy (tracheostomy in seven patients and chronic nocturnal use of nasal CPAP in one). Four patients (correctors) became eucapnic within two weeks of therapy. ⋯ The results indicated two separate mechanisms exist for chronic hypercapnia in OSAS: a critical balance between the ventilation during the time spent awake and hypoventilation due to apneas, a mechanism removed by treatment for obstructive apnea; and sustained hypoventilation independent of the apnea phenomenon and therefore not correctible. The subset of patients with the second mechanism appears to represent the true "Pickwickian" syndrome and can be identified before therapy by measuring a low level of ventilation in the sustained awake state.
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A new 2.7 mm flexible fiberoptic bronchoscope with a directable tip was used to evaluate potential airway problems in 73 pediatric patients. Forty-eight laryngoscopies and 47 bronchoscopies were performed over an 18-month period. ⋯ There were four complications and no deaths. This instrument enabled patients to be examined who were previously considered too small or who previously required rigid bronchoscopy under general anesthesia.
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Bronchoscopic phototherapy is available now for 2 distinct categories of tracheobronchial cancer: roentgenographically occult superficial squamous cell carcinoma and advanced malignancy causing significant airway obstruction. Laboratory and clinical experience show that the photodynamic effect of hematoporphyrin derivative phototherapy (HpD-PT) may be useful for treating superficial cancers that penetrate less than 5 mm into bronchial mucosa. The larger, obstructing cancers are better managed by high-power laser sources, such as the YAG laser, which are effective by hyperthermal photocoagulation, thermal necrosis, and tissue vaporization.
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International data demonstrate convincingly that lung cancer death rates follow and parallel cigarette smoking prevalence rates in both men and women. Effective control of lung cancer and the many other diseases associated with smoking can be achieved only by continued reductions in smoking prevalence in developed countries and the arrestment of smoking in developing countries. ⋯ By 1990, trial results will be available to allow systematic application of smoking control strategies (demonstrations) using physicians and dentists, mass media, school programs, self-help materials, and the community as a laboratory. For a number of reasons, such approaches are strongly recommended over efforts to reduce cigarette tar and nicotine levels as the primary focus of lung cancer control.