1. Definitions
1.1 Orthophthalaldehyde
A disinfectant with intense bactericidal, virucidal and fungicidal activity.
It acts by attacking nucleic acids and proteins.
Working solutions formulated as high-level disinfectants contain 0.55% of 1,2-benzenedicarboxaldehyde.
It is used for the disinfection of endoscopes, with action times of 12 min at 20°C.
1.2 Attributive Calculation of the Sample Size
The maximum lateral deviation "d" admitted from the central value for a given confidence level "C" is, when the population is finite:
Where:
N: Lot size (or population)
n: Sample size
Solving for "n", the sample size, with the known population size "N" and adopting a Zc, we obtain:
For an infinite "N" it will be:
When (N > 100 * n) the calculation is performed as if the lot size "N" were infinite.
2. Preliminary considerations
Airway stents can remain implanted for 29 days or more; they are in contact with mucous membranes and occasionally with blood, in a non-continuous manner.
They are used under sterile conditions, as a result of their treatment with ethylene oxide. The tests carried out and evaluated here report the results of using an alternative method based on the orthophthalaldehyde solution.
3. Method used
3.1 Determination of the sample size
The stent lot turned out to have a size of 80 individuals, so it is evaluated with the finite-sample method and the sample size is determined to be:
- Size N = 5
- For a confidence level of 99%
- An estimate of defective units in the lot p = 0.1
- And a maximum deviation d = 10% (0.1)
- And an AQLmaximum = 0.8 (Maximum Acceptable Quality Level)
The following table summarizes the calculations performed to determine the sample size:
3.2 Conditioning of the sample
The units selected at random were:
- A subglottic stent identified as SG14-40
- A Roll stent identified as ROLL 9-11
- A Class stent identified as CLASS12-50
- A radiopaque stenotic stent identified as SETX14-12
- A T-tube identified as TM12
The samples were washed with distilled water according to the company procedure identified as PC5.1.1-06 "Washing".
3.3 Test method
The samples were immersed for 20 minutes at a room temperature of 24°C in a 0.55% orthophthalaldehyde OPA solution (CIDEX® brand, lot 25418/118, expiring on 03/31/2020, identified as GTIN10705037000098).
Once the immersion time had elapsed, they were removed using material previously sterilized at a temperature of 121/134°C, and then washed with sterile physiological saline solution for medical use.
In accordance with the U.S.P. pharmacopoeia, 34th edition, the microbiological test included individual incubation in thioglycolate broth for 14 days at 32.5° ± 2.5° and in soybean-casein digest broth for 14 days at 22.5° ± 2.5°.
0.45-micron membranes were used (Hixwer brand, identified as HMNC04GNWS).
3.4 Test result
No negative values were found in the sample. The high-level disinfectant solution used has demonstrated its ability to eliminate bacteria, mycobacteria, lipid and non-lipid viruses, spores and fungi; and although the potential persistence of some sporulated bacterial forms is possible, none was detected in the present test.
The use of the sterilizing solution demonstrates a potential that can be confirmed with larger samples.