Precise manometric pressure, volume, and temperature (P-V-T) measurements of carbon in samples, standards, and blanks are critical for radiocarbon studies. While P and T uncertainties depend on instrument choice and environmental stability, V uncertainties depend on their method of measurement and are often overlooked. We used numerical simulations and error propagation to find optimum procedures for measuring “cold-finger” volumes equipped with capacitance diaphragm gauges (CDGs) by two common application of Boyle’s Law: cryogenic transfers and serial gas expansions with a reference flask of known volume. Minimum relative uncertainties of cold-finger volumes are comparable for these two methods (∼0.002), but the serial gas expansion method is preferred due to its convenience. Serial gas expansions can be performed to high precision by using dry air, an initial pressure ∼76% full-scale (e.g., 760 Torr), and a reference flask with an optimal volume based on preliminary estimates of cold-finger volumes and an empirical power function. The volumes of cold-fingers ≥ 12 cm3 can be determined with minimum achievable relative uncertainties of 0.0021 to 0.0023. This limit translates to minimum achievable relative uncertainties of 0.0026 to 0.0027 for P-V-T measurements of moles of gas simulated here.

The tracheal mucosa is very a delicate structure, and pressure–ischaemia problems following the use of cuffed tracheostomy tubes are well documented. Iatrogenic tracheal stenosis is one of the consequences of mucosal ischaemia and is very difficult to treat. In this study the accuracy of finger-tip tested tracheostomy tube cuff inflation pressure, as judged by consultants and non-consultants, was assessed by comparison with manometric pressure readings. The estimated pressure readings from the consultant group were more accurate than those from the non-consultant group, but a high standard deviation and very big difference between low and high readings in both these groups showed the real extent of the problem. Participants who performed 10 or more tracheostomies a year obtained more accurate results. No definite correlation was observed between the readings and the experience of the participants in otolaryngology or the size of the tube used. The authors recommend that instrumental monitoring of cuff pressure be considered good practice among junior otolaryngologists.

Abnormal tone in the pharyngo-oesophageal (PO) segment may lead to failure in developing oesophageal speech. Videofluoroscopy may give a qualitative assessment of the PO segment but is expensive, time consuming and lacks quantification. A custom built PO segment manometer was therefore assessed as a means of predicting eventual oesophageal speech outcome. Two groups of patientswere studied. In group 1(18 patients) the PO segment pressures were compared to their videofluoroscopy findings. Videofluoroscopy categorized the patients into four groups. The PO pressurescorresponded to this grouping, pressures above 20 mmHg being associated with voice failure. Ingroup 2 (12 patients) the PO pressures in the early post-operative period were compared to their eventual speech outcome. In all cases the pressures predicted the eventual speech outcome. The pressure manometer is a simple, cheap and portable device which is a reliable screening testto predict the potential for oesophageal speech.