Sputum induction: effect of nebulizer output and inhalation time on cell counts and fluid-phase measures.
BACKGROUND
A knowledge of the factors that can affect induced sputum results is essential in order to standardize the procedure.


OBJECTIVE
We investigated the influence of nebulizer output on sputum cell counts and fluid phase measurements at increasing times of sputum induction.


METHODS
Eighteen adults with stable asthma inhaled an aerosol of 3% hypertonic saline to induce sputum after 7, 14 and 21 min on 2 days separated by 48 h. On one day, in random order, the ultrasonic nebulizer used had a relatively low output of 0.87 mL/min (particle size 5.58 microm mass median aerodynamic diameter, MMAD) and, on the other, a higher output of 1.90 mL/min (particle size 4.14 microm MMAD). The sputum was selected from each expectorate and examined blind to the induction procedures.


RESULTS
With both nebulizers, the 14- and 21-min samples were lower in weight, neutrophils, eosinophils, eosinophil cationic protein (ECP) and interleukin (IL)-8 and higher in macrophages. The higher output nebulizer induced sputum with higher cell viability and lower ECP and IL-8.


CONCLUSIONS
The results identify that the volume of hypertonic saline inhaled in sputum induction influences the fluid-phase measurements. The duration of induction does alter the cell counts and suggests that the later expectorated sputum samples originate from more peripheral airways. The results draw attention to the need to standardize the volume and time of nebulization to accurately interpret and compare results.
Belda
J
J
The Asthma Research Group, Department of Medicine and Nuclear Medicine, St Joseph' s Healthcare and McMaster University, Hamilton, Ontario, Canada.
Hussack
P
P
Dolovich
M
M
Efthimiadis
A
A
Hargreave
F E
FE
D000280:Administration, Inhalation; D000328:Adult; D001249:Asthma / Q000188:drug therapy; D001798:Blood Proteins / Q000187:drug effects; D002452:Cell Count / Q000379:methods; D018592:Cross-Over Studies; D003430:Cross-Sectional Studies; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000187:drug effects; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D019570:Inhalation Exposure; D016209:Interleukin-8; D008264:Macrophages / Q000187:drug effects; D008297:Male; D009330:Nebulizers and Vaporizers; D009504:Neutrophils / Q000187:drug effects; D012260:Ribonucleases; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D013183:Sputum / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D013997:Time Factors
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D016209:Interleukin-8; D012462:Saline Solution, Hypertonic; D012260:Ribonucleases