Comparative studies for the determination of the diffusion capacity of the lung using CO and NO

Status:

completed 08/2007

Aims:

Evaluation of a new method to analyse the diffusing capacity of the lung on human being, optimizing of concentration of NO inhalation and breathhold time, comparison of the standard CO method with the new method using NO on healthy male nonsmokers.
Aim of these studies:
- Examining of a new method for the determination of the diffusion capacity of the human lung with reduction of the time during which patients have to hold their breath to 50 per cent.
- Comparison of the results from the measurement of the diffusion capacity with the standard method (CO) with the new method (NO) in a collective of healthy test subjects.
- Detection of nitric oxide carried out by a resonance absorption photometer (LIMAS) developed by the Institute of Laser Medicine (ILM).

Activities/Methods:

Spirometry, bodyplethysmography, gas analysis in respiratory air, ultrared spectrometer (URAS), LIMAS, standardization of the diffusing capacity parameter transfer factor of lung for carbon monoxide by single-breath (TLCO)/Transfer factor of lung for carbon monoxide by single-breath (TLNO).
For this purpose a prototype was developed in the ILM, with which it is possible to carry out single-breath measurements of the diffusion capacity of the lung. Here, NO is used as a test gas and the resonance absorption photometer integrated in the gas circulation can continually measure the concentration of nitric oxide.
As NO oxidises to nitric oxides in the presence of oxygen the gas mixture was newly produced before each start of the experiment. For that purpose an inhalation bag from the equipment of the bodyplethysmography measuring station (Master Screen PFT by Jaeger [now: Viasys]) was used, the original function of which was the measurement of the diffusion capacity of the lung
in the Single-Breath-Method.
From the construction plan of the Master Screen PFT, the movement of the gas inside the apparatus was studied, and the gas was led out of the Master Screen PFT into the LIMAS before it could reach the helium analyser. Afterwards it was led back into the system of the MS PFT at the same position. With the aid of the computer programme LabView the LIMAS data were recorded in real time. For the course of the measurement the MS PFT programme was used. To make sure that this is started and ended by the LIMAS values, these values were imported from the LIMAS to the MS PFT system via a switchable cable. In preparating this study, the ILM examined the minimal time patients have to hold their breath (TA = total time of holding breath) and which NO concentrations are necessary to guarantee a valid measurement of the diffusion capacity of the lung. This concentration was then used to carry out a study with a small sample of test subjects (n = 10).

Results:

It can be concluded that the resonance absorption photometry is a serious alternative to the other measurement methods of the NO-diffusion capacity of the lung. In contrast to the measurement of the diffusion capacity of the lung using CO, this method, which is valid also according to our results, has the advantage that it allows a significant shortening of the time patients have to hold their breath. The TA is reduced to now four s, i.e. by 50% while at the same time the previous MAK value of 25 ppm for nitrogen monoxide is maintained, even for the short time of exposure during the examination. This short TA can mean a great relief especially for severely ill patients with an impaired lung function, for whom such measurements are first and foremost relevant. In some cases, it might make such measurements possible in the first place. This does not only hold for diagnostics and the control of the findings of stationary patients and inpatients in the framework of health insurance, but especially for many people in the legal accidence insurance with whom such interstitial diseases of the lung have to be diagnosed and assessed in the context of occupational medical prevention or ascertainment of occupational diseases. In order for this method to become part of the medical every day work, it is necessary to adapt the apparatus to the requirements of daily routine on the one hand and to carry out further examinations both on larger samples of test subjects and on ill patients on the other hand.

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