Infrared spectroscopy on smoke produced by cauterization of animal tissue

The Development of a Novel Headspace O2 Concentration Measurement Sensor for Vials

In the process of manufacture and transportation, vials are prone to breakage and cracks. Oxygen (O₂) in the air entering vials can lead to the deterioration of medicine and a reduction in pesticide effects, threatening the life of patients. Therefore, accurate measurement of the headspace O₂ concentration for vials is crucial to ensure pharmaceutical quality. In this invited paper, a novel headspace oxygen concentration measurement (HOCM) sensor for vials was developed based on tunable diode laser absorption spectroscopy (TDLAS). First, a long-optical-path multi-pass cell was designed by optimizing the original system. Moreover, vials with different O₂ concentrations (0%, 5%, 10%, 15%, 20%, and 25%) were measured with this optimized system in order to study the relationship between the leakage coefficient and O₂ concentration; the root mean square error of the fitting was 0.13. Moreover, the measurement accuracy indicates that the novel HOCM sensor achieved an average percentage error of 1.9%. Sealed vials with different leakage holes (4, 6, 8, and 10 mm) were prepared to investigate the variation in the headspace O₂ concentration with time. The results show that the novel HOCM sensor is non-invasive and has a fast response and high accuracy, with prospects in applications for online quality supervision and management of production lines.

Does diathermy smoke contaminate processed salvaged blood in cardiac surgery?

INTRODUCTION

A cell salvage device is used in cardiac surgery with the aim of reducing allogeneic blood transfusion. Suction of blood from the operating field used for the device is often accompanied by diathermy smoke. There is limited published research to know if this blood is then contaminated with clinically significant levels of harmful chemicals from this smoke. Postoperative cardiac surgery patients are already physiologically vulnerable, making the optimization of salvaged blood worth considering.

METHODS

Ten patients who had cardiac surgery using a cell salvage device from a single institution had samples taken from the processed blood just prior to transfusion. Samples were tested for carbon monoxide (CO), cyanide and benzene. Results were compared to preoperative co-oximetry results and normal adult laboratory reference ranges. Demographic data about the patients was collected, including the type of operation, gender, age, body mass index, smoking status and amount of salvaged blood collected and processed.

RESULTS

Primary surgery was coronary artery bypass grafting (CABG) in three patients, mitral valve repair or replacement in three patients and one each of aortic valve replacement (AVR)/CABG, AVR/plication of the aorta, CABG/external wrapping of the aorta and valve-sparing root replacement. None were smokers. Neither the blood CO level prior to surgery nor in the processed salvaged blood was above the normal limit of 2% for non-smokers. There was no processed blood benzene found. Cyanide levels in the processed blood ranged from 1.8 to 44.1 μmol/l (where <8 μmol/l is considered within the normal adult laboratory limit).

CONCLUSION

Despite the obvious limitations of the current study, it shows that cyanide levels can be found many times the normal level in processed salvaged blood. Whilst the total dose of cyanide is small, the potential impact may be clinically significant due to cyanide's effect on mitochondrial metabolism in the heart and brain.

Direct high-precision measurement of the effective optical path length of multi-pass cell with optical frequency domain reflectometer

Multi-pass cells (MPCs) are commonly used in trace-gas detection and weak spectrum measurement. It is essential to accomplish a high-precision measurement of MPCs' effective optical path length (EOPL). A direct high-precision measuring method of MPCs' EOPL with optical frequency domain reflectometer (OFDR) was reported and demonstrated in this paper. Several important parameters of a MPC, such as EOPL and base length, were derived with high-precision by identifying the complicated signal of OFDR. The MPC's EOPL was also verified with the prevailing absorbance method. The results showed that the MPC's EOPL measured by each of these two methods is highly consistent. However, the relative uncertainty with the OFDR dramatically decreased 2 orders of magnitude (about 0.0085%) than that with the absorbance method. It demonstrated that the OFDR method with fewer measurement links is more conducive to a direct measurement. The performances of beam spread and stray light in the White-cell were also evaluated with the method.

In-vitro investigations on laser-induced smoke generation mimicking the laparoscopic laser surgery purposes

Intraoperative smoke-generation limits the quality of vision during laparoscopic/endoscopic laser-assisted surgeries. The current study aimed at the evaluation of factors affecting this phenomenon. As a first step, a suitable experimental setup and a test tissue model were established for this investigation. The experimental setup is composed of a specific sample container, a laser therapy component suitable for the ablation of model tissue at different treatment wavelengths (λ = 980 nm, 1350 nm, 1470 nm), a suction unit providing continuous smoke extraction, and a detection unit for smoke quantification via detection of light (λ = 633 nm) scattered from smoke particles. The ablation rate (AR) was calculated by dividing the ablated volume by the ablation time (60 sec). The laser-induced scattering signal intensity of the smoke (SI) was determined from time-charts of the signal intensity as a measure for vision, in addition a delay-time tdelay could be derived defining the onset of SI after the laser was switched on. The ratio SI/AR is used as a measure for smoke generation in relation to the ablation rate. Additionally the light transmission of the tissue samples was used to estimate their optical properties. In this set-up, smoke generation using λ = 980 nm as ablation laser wavelength was detected after a delay-time tdelay = (121.6 ± 24.8) sec which is significantly longer compared to the wavelengths λ = 1350 nm with tdelay = (89.8 ± 19.3) sec and λ = 1470 nm with tdelay = (24.7 ± 5.4) sec. Thus, the delay Experimental set-up consisting of sample container, laser therapy component, suction unit and scattered-light detection compartment. time is wavelength-dependent. The SI/AR ratio was significantly different (p < 0.001) for 1470 nm irradiation compared to 980 nm irradiation [SI/AR(1470) = (11.8 ± 2.6) · 10(3) vs. SI/AR(980) = (8.6 ± 2.0) · 10(3) ]. The ablation crater for 980 nm irradiation was comparable with 1470 nm irradiation, but the coagulation rim was thicker in the 980 nm case. In conclusion, it could be shown experimentally that smoke-generation depends on the wavelength used for laser ablation.

Multipass cell based on confocal mirrors for sensitive broadband laser spectroscopy in the near infrared

We report on broadband absorption spectroscopy in the near IR using a multipass cell design based on highly reflecting mirrors in a confocal arrangement having the particular aim of achieving long optical paths. We demonstrate a path length of 314 m in a cell consisting of two sets of highly reflecting mirrors with identical focal length, spaced 0.5 m apart. The multipass cell covers this path length in a relatively small volume of 1.25 l with the light beam sampling the whole volume. In a first application, the absorption spectra of the greenhouse gases CO(2), CH(4), and CO were measured. In these measurements we used a femtosecond fiber laser with a broadband spectral range spanning the near IR from 1.5 to 1.7 μm. The absorption spectra show a high signal-to-noise ratio, from which we derive a sensitivity limit of 6 ppmv for methane observed in a mixture with air.

Development of an optical gas leak sensor for detecting ethylene, dimethyl ether and methane

In this paper, we present an approach to develop an optical gas leak sensor that can be used to measure ethylene, dimethyl ether, and methane. The sensor is designed based on the principles of IR absorption spectrum detection, and comprises two crossed elliptical surfaces with a folded reflection-type optical path. We first analyze the optical path and the use of this structure to design a miniature gas sensor. The proposed sensor includes two detectors (one to acquire the reference signal and the other for the response signal), the light source, and the filter, all of which are integrated in a miniature gold-plated chamber. We also designed a signal detection device to extract the sensor signal and a microprocessor to calculate and control the entire process. The produced sensor prototype had an accuracy of ±0.05%. Experiments which simulate the transportation of hazardous chemicals demonstrated that the developed sensor exhibited a good dynamic response and adequately met technical requirements.

A single-blind controlled study of electrocautery and ultrasonic scalpel smoke plumes in laparoscopic surgery

BACKGROUND

Surgical smoke containing potentially carcinogenic and irritant chemicals is an inevitable consequence of intraoperative energized dissection. Different energized dissection methods have not been compared directly in human laparoscopic surgery or against commonly encountered pollutants. This study undertook an analysis of carcinogenic and irritant volatile hydrocarbon concentrations in electrocautery and ultrasonic scalpel plumes compared with cigarette smoke and urban city air control samples.

METHODS

Once ethical approval was obtained, gas samples were aspirated from the peritoneal cavity after human laparoscopic intraabdominal surgery solely using either electrocautery or ultrasonic scalpels. All were adsorbed in Tenax tubes and concentrations of carcinogenic or irritant volatile hydrocarbons measured by gas chromatography. The results were compared with cigarette smoke and urban city air control samples. The analyzing laboratory was blinded to sample origin.

RESULTS

A total of 10 patients consented to intraoperative gas sampling in which only one method of energized dissection was used. Six carcinogenic or irritant hydrocarbons (benzene, ethylbenzene, styrene, toluene, heptene, and methylpropene) were identified in one or more samples. With the exception of styrene (P = 0.016), a nonsignificant trend toward lower hydrocarbon concentrations was observed with ultrasonic scalpel use. Ultrasonic scalpel plumes had significantly lower hydrocarbon concentrations than cigarette smoke, with the exception of methylpropene (P = 0.332). No significant difference was observed with city air. Electrocautery samples contained significantly lower hydrocarbon concentrations than cigarette smoke, with the exception of toluene (P = 0.117) and methyl propene (P = 0.914). Except for toluene (P = 0.028), city air showed no significant difference.

CONCLUSIONS

Both electrocautery and ultrasonic dissection are associated with significantly lower concentrations of the most commonly detected carcinogenic and irritant hydrocarbons than cigarette smoke. A nonsignificant trend toward lower hydrocarbon concentrations was seen with ultrasonic scalpel dissection compared with diathermy. The contamination levels in city air were largely comparable with those seen after ultrasonic scalpel use. Although hydrocarbon concentrations are low, cumulative exposures may increase health risks. Where concerns arise, ultrasonic scalpel dissection may be preferable.

Automated broad tuning of difference frequency sources for spectroscopic studies

Transmission spectroscopy over large spectral ranges (>100 cm(-1)) generally requires a reference measurement to be taken separately from the sample scan. The ratio of the two measurements (i.e., the transmittance) is therefore susceptible to baseline changes that occur between the recording of the two spectra. The origins of relatively strong baseline changes (≫1%) of a difference-frequency-generation-based laser spectrometer (tuning range 2900-3144 cm(-1), 150 μW average power) were investigated and a method for minimizing them by improving reproducibility and reducing measurement time is presented. The new method was tested for a gas mixture and the sensitivity for broad absorption features was determined as 5×10(-3) minimum measurable absorbance for a total scan duration of 70 min.