Healthy lungs tolerate repetitive collapse and reopening during short periods of mechanical ventilation

The possible occurrence of lung damage if alveolar units are allowed to collapse and reopen breath by breath during mechanical ventilation with normal tidal volumes was investigated. Anaesthetised, paralysed, open chest rabbits were subjected to either intrathoracic negative (NEEP; n=6) or positive (PEEP; n=6) end-expiratory pressure during volume controlled mechanical ventilation. Both experimental settings were preceded by a 30 min control period and followed by a 30 min recovery period during which a PEEP of 0.2 kPa was maintained. Pao₂ and pulmonary compliance deteriorated significantly in the NEEP group during the experimental period and compared to ventilation with PEEP. Partial restoration of lung mechanics and blood gases was achieved during the recovery period. After an alveolar recruitment manoeuvre, this recovery was complete. Lung clearance studied by depositing an aerosol of technetium-99m-labelled diethylenetriamine pentaacetate (^99mTc-DTPA) in the alveoli, was significantly faster during ventilation with NEEP compared to the PEEP group ( P =0.0002) as well as the control period ( P = 0.0029). It did not recover completely during the recovery period but remained significantly faster. light microscopic histology was normal in both groups with no evidence of inflammation or epithelial disruption. We conclude that previously healthy rabbit lungs show only a transient disturbance of lung mechanics and blood gases with repetitive collapse and re-expansion. The integrity of the alveolar rnicrostructure is preserved. The disturbance in the alveolo-capillary permeability persists and may indicate surfactant related alveolo-capillary barrier dysfunction.     

Experimental studies on the comparative infectivity and pathogenicity of Streptococcus suis type 2. II. Porcine and human isolates in laboratory animals

Mice, rats, guinea-pigs and rabbits were inoculated with isolates of Streptococcus suis type 2. An isolate cultured from the tonsils of a healthy pig, produced disease in rabbits after intravenous inoculation but not in mice, rats or guinea-pigs. An isolate of S. suis type 2, that was pathogenic for pigs and had been cultured from a human patient with clinical disease, produced signs of neurological disease in mice, rats and rabbits following intravenous inoculation. There was an apparent dose response in mice with 31% of mice receiving more than 10(6) organisms developing clinical disease, whilst mice receiving less than this did not develop disease. There were no detectable histopathological lesions in the brains or meninges of mice with nervous signs. It is proposed that the disease in mice may mimic that reported in humans and that mice may be a useful indicator species for determining the virulence of isolates cultured from pigs.     

National Alliance for Oral Health Consensus Conference on Medically Necessary Oral Health Care: Legal issues

This paper examines medical malpractice law as it applies to medically necessary oral health care. The basic legal concepts and reported cases involving medically necessary oral health care are reviewed. It is concluded that dental professionals and consumer advocates must advance their educational and legislative advocacy efforts so that health professional colleagues and the public will become aware of the importance of these services and insurers will routinely include coverage of medically necessary oral health care in their medical and dental policies. While failure to provide medically necessary oral health care can be violative of patient rights and legally actionable, medical malpractice litigation should always be the behavior modifier of last resort.