Effect of cricoid force on airway calibre in children: a bronchoscopic assessment.

BACKGROUND: Cricoid pressure or to be more exact cricoid force (CF) can cause airway obstruction and subsequent difficulty with airway management during an emergency induction. METHODS: We studied 30 children with an age range of 3 months to 15 yr who presented for routine bronchoscopy or other surgical procedures requiring tracheal intubation. We looked at the effect of CF on the calibre of the subglottic airway and objectively measured the force which caused 50% or greater distortion/compression of the subglottic airway. RESULTS: There was a linear relationship between both age and weight and CF. No patient suffered any adverse effects. Overall, the mean force required to compress the airway was 10.5 N. However, this force could be as low as 5 N in children <1 yr of age, and up to between 15 and 25 N in teenagers. CONCLUSIONS: Forces well below the recommended value of 30 N will cause significant compression/distortion of the airway in a child.

Fixity of ports to the abdominal wall during laparoscopic surgery: a randomized comparison of cutting versus blunt trocars.

BACKGROUND: Dislodgement of ports from the abdominal wall is a common problem during laparoscopic surgery. The aim of this study was to evaluate port stability using either cutting or blunt-tipped trocars. METHODS: Patients undergoing laparoscopic surgery were randomized to have the secondary ports inserted using either cutting or blunt-tipped trocars. The fixity of ports to the abdominal wall was evaluated at the start and completion of surgery by measuring the total traction force required to displace the ports. Similarly, the friction forces required to displace instruments within the ports were measured. RESULTS: Thirty patients were randomized into two groups (15 patients in each group), and a total of 114 ports (cutting, n = 51; blunt, n = 63) were evaluated. The groups were comparable in age, gender, body mass index, and operating time. The total traction forces needed to displace the 5-mm and 10-mm ports were significantly lower when cutting trocars were used at both the beginning (2.6 vs. 11.8 N, p < 0.001, and 6.3 vs. 15.5 N, p = 0.014, respectively) and completion of surgery (1.3 vs. 6.7 N, p < 0.001, and 1.1 vs. 12.0 N, p = 0.001, respectively). The declines in the total traction forces from the start to the completion of surgery were significant for the 5-mm and 10-mm cutting-trocar ports (p = 0.031 and p = 0.043, respectively) but not for the blunt-trocar ports (p = 0.088 and p = 0.152, respectively). While no significant differences between the instruments' friction forces and the traction forces of the cutting-trocar ports were observed, the former were significantly lower than the traction force needed to displace the blunt-trocar ports. This explains the significantly greater frequency of spontaneous port dislodgements when cutting ports were employed (25.5% vs. 1.6%, p < 0.001). Port-site bleeding was encountered only in patients (n = 2, 13%) where cutting trocars were used. CONCLUSIONS: Port fixity to the abdominal wall during laparoscopic surgery declines with time. The insertion of ports using a blunt-tipped trocar is associated with significantly greater stability and fixity of the port to the abdominal wall. The use of blunt-tipped trocars is recommended for routine practice in laparoscopic surgery.

The classification of oesophageal 24 h pH measurements using a Kohonen self-organizing feature map.

Analysis of 24 h oesophageal pH studies can be problematic with many patients asymptomatic during the investigation, despite observations of reflux. The aim of this study was to carry out a cluster analysis of ambulatory pH studies to determine any underlying patterns and classes within the data. The results of 900 24 h pH studies were investigated using the Kohonen self-organizing feature map (SOFM), a neural network that can be used to identify clusters within multidimensional data. The clinical features were presented to the network and the main classes identified. The SOFM-based analysis showed that patients clinically assessed as having symptomatic reflux during the study could be described by four major classifications. The results also showed that the probability of identifying a correlation between symptoms and reflux during an investigation varies from 0.49 to 0.78 for the classes identified. The developed network may be a useful tool in the classification of pH data. The cluster-based technique may offer an alternative to standard statistical techniques for high-dimensional gastrointestinal data and form the basis of an expert system for the automated analysis of pH data.

A pH-mucosa area unit of measure to consider morphology of the oesophagus when evaluating oesophagitis.

Gastro-oesophageal pH measurements are routinely carried out to quantify and determine if levels of acid reflux are responsible for symptoms. Although considered the 'gold standard', evidence suggests that pH measurements do not correlate well with the degree of oesophagitis seen during endoscopy. In this study the current measure of pH was critically examined taking into account both the effects of changes in luminal diameter and endoscopy observations. The oesophageal lumen diameter was investigated using a barium swallow for 25 patients presenting with oesophageal disorders. For each subject the widest luminal diameter was measured for a series of five controlled swallows. The results showed that the lumen diameter varied widely from 0.9 to 3.8 cm. An alternative approach to the current measurement of pH was explored. In this approach the exposure not only included the luminal pH and time exposed but also the area of mucosa exposed as a result of differing luminal diameters. Although it is currently not possible to assess the diameter or morphology of the oesophageal lumen during a pH study, the analysis highlighted that the current measure of pH exposure time does not include the area of mucosa exposed. These results may explain, to some extent, the poor correlation between pH measurements and degree of oesophagitis seen during endoscopy.

An investigation into the spatial relationship between complexity and motility within the oesophagus.

Nonlinear analysis techniques have recently been used in the characterization of complex physiological signals seen in pathological disorders such as epilepsy and cardiac fibrillation. In this study a series of controlled swallows from an asymptomatic demonstration group was investigated using oesophageal manometry. The nonlinear measure of complexity, largest Lyapunov exponents and phase portraits were then used to explore the complexity of motility patterns at different points within the oesophagus. Results indicate greater complexity within the region of the striated muscle in the upper oesophagus than that observed within the region of smooth muscle in the lower oesophagus. Phase portraits showed that manometry patterns within the asymptomatic demonstration group could be quite different, highlighting the problems in clinical diagnosis. The characterization of motility disorders associated with complex manometry patterns such as diffuse oesophageal spasm (DOS) and nonspecific motility disorder (NOMD) still represents a diagnostic challenge. The use of nonlinear techniques enabling the quantitative and qualitative measurement of oesophageal complexity is considered in the classification of such disorders.

Technical report: The introduction of a new synchronized oesophageal manometry and digital video-fluoroscopy (fluoromanometry) system into the radiology suite.

Following the development of a new fluoromanometry system enabling synchronous oesophageal manometry and barium swallow video-fluoroscopy, both the equipment and examination method have been successfully introduced into the radiology suite. The application of the system which uses a PC with video capture and a portable manometry recorder is described together with details of its implementation and the examination technique used.

Synchronous recording and review of oesophageal manometry and video fluoroscopy using a portable manometry recorder and PC with integrated digital video acquisition.

We present the technical details of a new system for the synchronous recording and review of a combined oesophageal manometry and video fluoroscopic barium swallow examination. The system developed uses a portable manometry recorder and personal computer (PC) with an integrated digital video acquisition system. These are controlled using software to enable the real time capture of digital video and manometric data throughout the combined examination. The recorded pressure waveforms can then be synchronously displayed on a screen with the recorded digital video of the fluoroscopic barium swallow. This new tool enables both comparative measurement and detailed analysis of the relationship between visualized bolus transport and pressure measurements. It provides for a deeper understanding and improved clinical assessment of complex motility disorders over those obtained when these two modalities are applied separately. The system is easily incorporated into a clinical radiology suite and it is both user and patient friendly. It uses readily available computer hardware together with multimedia software and is a comparatively economical addition to the radiology suite with the manometry analysis available fulfilling the criteria laid down by the Clinical Associates Group of the British Society of Gastroenterology.