Comparison of Ultrasonically Nebuli...

Comparison of Ultrasonically Nebulized Distilled Water and Cold-air Hyperventilation Challenges in Asthmatic Patients

Exercise has been implicated as a cause of bronchoconstriction, and studies in the past 15 to 20 years have investigated the pathophysiologic mechanisms. These studies enlist in one's serviceed free running, treadmill exercise, period ergometr, and isocapnic hyperventilation challenges. A worthy correlation between the latter and exercise challenges was noted. [1 2] Other studies have explored the importance of inspired temperature and humidity during exercise; bronchoconstrictor replication increased as temperature and humidity decreased. [3 4] Despite these advances, however, the exact mechanism producing bronchoconstriction during exercise remains enigmatic.

present theory suggests exercise or hyperventilation flows in heat and water los from the bronchial mucosa, and an osmolar gradient is established. [5] This osmolar change could then induce mediator release from mast lonely dwellings and basophils, as shown in vitro, and create bronchoconstsriction. [5-7] Although debate exists regarding peripheral blood evens of various mediators after exercise and hyperventilation challenges, [5] local mediator release cannot be excluded

In the late 1960 anesthesiologists noted that inhalation of nebulized aerosols caused deterioration of lung function. [8] Since that time, challenges employing inhalation of hypotonic and hypertonic solutions have been studied. Although the couple osmolarities may produce bronchoconstriction, the more hypotonic or hypertonic the solution, the greater the bronchoconstrictive reply [8, 9]

If we hypothesize that the mechanism for inducing bronchoconstriction with varying osmolarities is the same as exercise or hyperventilation challenges, there should be a sturdy correlation between the challenge be deriveds Studies comparing distilled water and exercise [10] or hyperventilation and hyperosmolar solutions [11] have shown proper correlations. Two studies comparing hyemal air hyperventilation and distilled water, however, obtained conflicting ends [12, 13] Hoping to dissolve this controversy the present cogitation was undertaken.

MATERIAL AND METHODS

The controls consisted of 11 asthmatic patients, seven men and four women all of whom were known responder to methacholine (Table 1) Sustained-release theophylline preparations were withheld for at least 24 hours and [beta]-agonist inhalers at least 12 hours prior to testing. Each make submissive underwent a cold-air hyperventilation challenge (CAHC) and ultrasonically nebulized distilled water (UNDW) challenge in succession two separate days within a week of other and at the same time of day. Before each challenge baseline spirometry was performed using a Cybermedic CM-V pneumotach, and baseline[FEV.sub.1] values where requried to be at least within 70 percent of predicted value. [14]

The concentrations of methacholine were 01 02 06 20 60 200 and 60 mg/ml The inhalation performance included five slow inhalations of methacholine from functional residual capacity to inspiratory capacity at each stair without breath holding. The methacholine challenge deed utilized in our laboratory has been detailed previously. [15]

A DeVilbiss Ultra-Neb 100 (DeVilbiss Co) was used for the UNDW Challenge. This unit has a nebulizer output of 29 L/min with an input fan spe of 351 L/min. As by means of DeVilbiss specification, the aerosolized particle size was between 05 and 50 [mu]

The UNDW challenge was performed using sequential timed degrees of 15 s X 2 30 s X 1, min X 1 2 min X 1 and 4 min X 2 Nebulizer fan spe and output have the direction ofs were on maximal settings during all grades The output of the nebulizer when joined to the studied subjects was variable for the 11 enslaves and averaged 1.6 [+ or -] 5 mil for 15 s 2.5 [+ or -] 9 ml for 30 s; 47 [+ or -] 15 ml for 1 min, 77 [+ or -] 10 ml for 2 min, and 13 [+ or -] 14 ml for each of the 4-min gradations At each step, the subdue with a nose-clip attached, tidally breathed end a mouthpiece directly connected to a Hans-Rudolph Non-rebreathing Valve No 2700 which was attached to a 15i mm X 22 mm internal diameter tube leading from the nebulizer. Forced expiratory maneuvers were performed 3 min after each times pace and done in triplicate to make secure reproducibility. The highest of sum of two units consistent (3 percent difference) [FEVsub1] attempts was recorded at each degree The nebulizer canister was weighed initially and at the conclusion of each step on an Ohaus Port-O-Gram C-3001 electronic balance, with + 1/ - 1 accuracy. simply the canister was weighed at each grade with all attaching tubing remov The cumulative dose of nebulized water was thus determined at each gradation The challenge was complet when the bring under rule had at least a 20 percent fall in [FEVsub1] compared with baseline, or when the next to the first 4-min step was completed.

The CAHC make use ofed compressed air pumped through a refrigeration unit capable of producing 120 L/min of col air at -20[degrees]C for through the whole extent of 1 h. The [COsub2] was added to the connected view at 5 L/min, which maintains eucapnia athwart a wide range of minute ventilation. [2] The frigid air left eh refrigeration unit in consequence of 18 cm of insulated tubing and terminated at a mouthpiece equipped with a one-way valve. Expired air transversed tubing containing a 30 L latex balloon associateed to a suction that could be regulated from a Precision Bore Flowrator Tube (Fisher and Porter Co) to maintain a predetermined air pour The subject was instructed to withhold the balloon inflated, thus ensuring ventilation at a pitch uponed rate. Inspiratory and expiratory temperatures were recorded by way of in-line thermocouples.