Diaphragm Pacing without Tracheostomy in Congenital Central Hypoventilation Syndrome Patients.

BACKGROUND: Congenital central hypoventilation syndrome (CCHS) is a rare disorder affecting central control of breathing. Thus, patients require lifelong assisted ventilation. Diaphragm pacing (DP) may permit decannulation in those who are ventilator dependent only during sleep. OBJECTIVE: The purpose of this study is to determine if patients with CCHS can be successfully ventilated by DP without tracheostomy. METHODS: We reviewed the records of 18 CCHS patients (mean age 19.5 ± 10.1 years; 44% female) who were ventilated by DP only during sleep. RESULTS: Prior to diaphragm pacer implantation surgery, 14 CCHS patients had been using home portable positive pressure ventilation (PPV) via tracheostomy, 1 had been on PPV via endotracheal tube, and 3 had been using noninvasive PPV (NPPV). Of the patients with tracheostomy prior to DP (n = 15), 11 (73%) were decannulated and ventilated successfully by DP without tracheostomy. Of all the patients reviewed (n = 18), 13 (72%) were successfully ventilated by DP without tracheostomy. Obesity prevented successful DP without tracheostomy in 1 patient, and upper airway obstruction prevented success in another patient. Snoring and/or obstructive apneas were present in some patients, but they were improved by diaphragm pacer changes, adenotonsillectomy, and/or use of nasal steroids. CONCLUSIONS: DP without tracheostomy can be successfully achieved in patients with CCHS. Snoring and obstructive apneas, when present, can be managed by diaphragm pacer changes and medical therapies. Obesity can pose a challenge to successful DP.

Simultaneous high-temperature gas chromatography with flame ionization and mass spectrometric analysis of monocarboxylic acids and acylglycerols in biofuels and biofuel intermediate products.

Triacyl-, diacyl- and monoacylglycerols (TAGs, DAGs, MAGs) along with monocarboxylic acids (MCAs) are intermediate products in many triacylglycerol oil-to-biofuel conversion pathways. Accumulation of these compounds leads to poor biofuel characteristics and may result in fuel system damage. We developed a method for simultaneous identification and quantification of a wide range of MCAs (C4-C18), MAGs, DAGs, and TAGs. The method is based on trimethylsilylation followed by high temperature GC with programmed temperature vaporizer (PTV) injection coupled to parallel FID and MS detectors (HTGC-FID/MS). To minimize the discrimination of both low and high molecular weight species typically occurring on the injector, we optimized injection conditions using a central composite design. The critical variables were the time at initial temperature (40 °C), splitless time, and the interaction between these two parameters. Among three tested electron ionization source/quadrupole analyzer temperatures, a 350/200 °C setting provided the highest response and signal-to-noise ratio for TAGs and did not have an effect on MAGs and DAGs. Similar results were obtained when quantifying target analytes in intermediate products of soybean oil cracking with FID and MS (using specific acylglycerol fragmentation ions). The instrumental FID limits of detection (LODs) were 0.07-0.27 ng for most of the target analytes. Selected ion monitoring (SIM) LODs were 0.01-0.05 ng for MCAs and 0.03-0.14 ng for acylglycerols. For the total ion current (TIC), LODs observed increased with acyl chain length and degree of unsaturation, resulting in an increase from 0.05 to 0.18 ng for MCAs (C5 to C18) and from 0.03 to 1.8 ng for acylglycerols (TAGs C8 to C22). Deviations in the repeatability of sample preparation, intra- and inter-day analyses, including sample stability over an eight-day time period, did not exceed 10% variance. These results demonstrate that the developed method is accurate and robust for the determination of acylglycerols and MCAs produced during the processing of TAGs into biofuels.

Obstructive Sleep Apnea in Patients With Congenital Central Hypoventilation Syndrome Ventilated by Diaphragm Pacing Without Tracheostomy.

STUDY OBJECTIVES: To determine presence of obstructive sleep apnea (OSA) in patients with congenital central hypoventilation syndrome (CCHS) ventilated by diaphragm pacing (DP) without tracheostomy, and to determine if OSA can be improved by DP setting changes. METHODS: We reviewed polysomnography (PSG) results of 15 patients with CCHS from October 2001 to April 2014, age 15.4 ± 7.8 years, body mass index 22.0 ± 6.0 kg/m2, and 60% female. RESULTS: Of the 22 PSG results obtained for the 15 patients with CCHS, 9 were performed with tracheostomy capped, and 13 were performed after patients underwent decannulation. OSA was present on 6 of 9 tests in patients with tracheostomy capped, including 3 patients with immediate, severe OSA necessitating that the studies be completed with tracheostomy uncapped. OSA was present on 2 of 13 tests in patients in whom decannulation had been performed. Hypoventilation was seen on only one test without OSA. On 2 of 5 tests showing OSA, OSA improved by decreasing DP amplitude settings; apnea-hypopnea index decreased from 11.1 ± 2.5 to 1.8 ± 2.5 events/h; PETCO2 decreased from 57.5 ± 3.5 to 38.5 ± 0.7 torr; SpO2 increased from 76.5 ± 0.7% to 93.0 ± 7.1%. OSA improved in one patient with slight increase in respiratory rate. Settings were manipulated in 4 tests showing OSA; no changes were attempted in the remaining study. One patient was placed on bilevel positive airway pressure with temporary suspension of DP. Age (P < .119), previous adenotonsillectomy (P < .211), and body mass index (P < .112) did not significantly contribute to OSA. CONCLUSIONS: OSA occurs in patients with CCHS ventilated by DP. However, decreasing DP amplitude settings can lessen upper airway obstruction without compromising gas exchange.

Limits of detection for the determination of mono- and dicarboxylic acids using gas and liquid chromatographic methods coupled with mass spectrometry.

The chromatographic separation and instrumental limits of detection (LODs) were obtained for a broad range of C(1)-C(18) monocarboxylic (MCAs) and C(2)-C(14) dicarboxylic acids (DCAs) employing either chemical derivatization followed by gas chromatography-mass spectrometry and flame ionization detection (GC-MS/FID) or direct analysis with liquid chromatography high resolution MS and tandem MS (LC-MS). Suitability, efficiency and stability of reaction products for several derivatization agents used for esterification (BF(3)/butanol), and trimethysilylation, including trimethylsilyl-N-N-dimethylcarbamate (TMSDMC) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were evaluated. The lowest limits of detection for the majority of compounds below 10 pg (with the exception of acetic acid) were obtained for derivatization with BF(3)/butanol followed by GC-MS in the total ion current (TIC) mode. Further improvements were achieved when applying either selected ion monitoring (SIM), which decreased the LODs to 1-4 pg or a combination of SIM and TIC (SITI) (2-5 pg). GC-FID provided LODs comparable to those obtained by GC-MS TIC. Both trimethylsilylation (followed by GC-MS) and direct LC-MS/MS analysis yielded LODs of 5-40 pg for most of the acids. For volatile acids the LODs were higher, e.g., 25 and 590 ng for TMSDMC and BSTFA derivatized formic acid, respectively, whereas the LC-MS methods did not allow for the analysis of formic acid at all.