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D M Denison

Publications and source records attributed to D M Denison.

59 records · Page 4Linked to original sources
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Cold air test: a simplified standard method for airway reactivity.

A simple and standardized test has been developed to measure airway responsiveness to cold dry air. This consists of stepwise increases in ventilation of dry subfreezing air at 10, 20, 40 and 60% of predicted indirect maximum breathing capacity (IMBC). For each step, the inhalation time was 3 min. The optimal time between the steps was 5 min. Exposure ceased when either a fall in forced expiratory volume in one second (FEV1) of more than 20% of baseline occurred or when there was no response after breathing cold air at 60% predicted IMBC. Moderate isocapnic hyperventilation with cold air beyond 3 min induced no further bronchoconstriction. Varying the interval (0, 2 and 5 min) between the steps produced no significant differences in test results. Changing the pattern of breathing had no effect on airway responsiveness, provided that the patient maintained a constant minute-ventilation. This implies that it is not necessary to monitor the rate and depth of respiration continuously in order to achieve a given minute-ventilation, making the technique simpler. In addition, a "CO2 requirement graph" has been constructed at different levels of ventilation. This allows the inspired CO2 concentration to be preset, eliminating the need for elaborate equipment and monitoring of end-tidal CO2 to keep the subject isocapnic during hyperventilation.

Adult↗
PubMedDate not supplied

Reevaluation of the radiographic method for measurement of total lung capacity.

To clarify whether the radiographic estimate of total lung capacity (TLC) using the method of Barnhard et al., as modified by Loyd et al., yields accurate values, we measured TLC in 20 young healthy subjects with the above technique (Vb). We compared it to the more sophisticated radiologic method of Pierce et al. (Vp) and to plethysmographic measurements (Vbox). Plethysmographic results, 7.38 +/- 0.94 l (mean +/- SD) or 101.7% of predicted, were significantly higher than Vb (mean difference 0.53 +/- 0.68 l; p less than 0.005 by paired t test), but were not significantly different from Vp (mean difference 0.13 +/- 0.52 l). Based on these and previous data, we conclude that the Pierce et al. approach yields more accurate results than the Barnhard and Loyd method, although individual data, in both methods, should be interpreted cautiously.

Adult↗