Predictive value of airways hyperresponsiveness and circulating IgE for identifying types of responses to toluene diisocyanate inhalation challenge.

Development of asthma after exposure to toluene diisocyanate (TDI) has been recognized in a variety of occupational settings. However, the pathogenesis of isocyanate-induced asthma remains controversial. In particular, the role of IgE in the development of TDI-induced asthma has remained uncertain. To investigate predictive factors for response to inhalation challenge with TDI, we analyzed data from 63 subjects referred for evaluation of respiratory symptoms thought to be related to TDI sensitization. All subjects underwent interview, routine phlebotomy, spirometry, methacholine challenge, and allergy skin testing prior to TDI challenge. Spirometry and methacholine challenge were repeated 1 day after TDI challenge. The cumulative dose of methacholine needed to produce a 20% decrease in FEV1 (PD20) was determined. A PD20 of 1.4 mg or more was considered normal. Subjects were challenged by exposure to 5 to 10 ppb TDI for up to 30 min in a 9 m3 exposure chamber. A positive response was a 20% or more decrease in FEV1 within 1 h (early) or beyond 1 h (late) after TDI exposure. Thirty-four subjects (54%) had a positive response, of whom 12 (35% of responders) had isolated early responses, 13 (38%) had isolated late responses, and the remainder had dual responses. Thirty-two individuals (51%) had a positive response to methacholine (AR+) prior to TDI challenge. AR+ was strongly associated with a positive TDI challenge: 23 AR+ subjects (72%) had a positive TDI challenge, compared with only 11 AR- subjects (35%) (p < 0.01). AR positivity did not predict the time of onset of TDI response.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen enrichment of bag-valve-mask units during positive-pressure ventilation: a comparison of various techniques.

Bag-mask devices are used frequently to provide patients with positive-pressure-assisted ventilation. To increase the percentage of oxygen delivered (FDO2) from the bag, supplemental oxygen must be provided by way of an oxygen inlet nipple attached to the unit. Using ten medical volunteers and a test lung with oxygen analyzer, we studied the effect of several variables on the FDO2 and determined the most effective reservoir that would provide the highest consistent FDO2 from the ventilating port of the bag. An FDO2 of 1.00 was consistently provided by the 2.5-L bag reservoir and a demand-valve set-up attached to the reservoir port of the ventilating bag. Bag refill time significantly affected the FDO2 when no reservoir or corrugated tube reservoirs were used. Corrugated tube reservoirs were found to be more sensitive to all variations in ventilatory technique and to oxygen flow rates. From our findings we recommend that corrugated tube reservoirs not be used for oxygen supplementation, as they are sensitive to variations in ventilatory technique and cannot alert clinicians to problems with oxygen flow. While both the 2.5-L bag reservoir and demand-valve provide a consistent FDO2 of 1.00, the demand valve has the advantage of audible filling of the ventilating bag as well as being compact and independent of ventilatory technique.

Tracheitis: the 'other' cause of upper airway obstruction.

A 22-year-old woman presented to an ear, nose, and throat clinic with an upper respiratory infection and sudden stridorous respirations. Aerosolized isoethrane therapy was beneficial and fiber-optic nasolaryngoscopy revealed a normal supraglottis and purulent intratracheal secretions. Secretions were cultured and grew Staphylococcus aureus and alpha hemolytic Streptococcus. IV cefazolin was initiated and the patient recovered without sequelae. This case illustrates a rare cause of upper airway obstruction, tracheitis. Tracheitis has been found in the pediatric literature. This is the first adult case reported in the literature.