Assessing the agreement between the pneumatic and the flow-centrifuge method for estimating xylem safety in temperate diffuse-porous tree species.

The increasing frequency of global change-type droughts has created a need for fast, accurate and widely applicable techniques for estimating xylem embolism resistance to improve forecasts of future forest changes. We used data from 12 diffuse-porous temperate tree species covering a wide range of xylem safety to compare the pneumatic and flow-centrifuge method, two rapid methods used for constructing xylem vulnerability curves. We evaluated the agreement between parameters estimated with both methods and the sensitivity of pneumatic measurements to the duration of air discharge (AD) measurements. There was close agreement between xylem water potentials at 50% air discharged (PAD), estimated with the Pneumatron, and 50% loss of hydraulic conductivity (PLC), estimated with the flow-centrifuge method (mean signed deviation: 0.12 MPa, Pearson correlation: 0.96 after 15 s of gas extraction). However, the relationship between the estimated slopes was more variable, resulting in lower agreement in the xylem water potential at 12% and 88% PAD/PLC. The agreement between the two methods was not affected by species-specific vessel length distributions. All pneumatic parameters were sensitive to AD time. Overall agreement was highest at relatively short AD times, with an optimum at 16 s. Our results highlight the value of the Pneumatron as an easy and reliable tool to estimate 50% embolism thresholds for a wide range of diffuse-porous temperate angiosperms. Further, our study provides a set of useful metrics for methodological comparisons of vulnerability curves in terms of systematic and random deviations, as well as overall agreement.

Anesthesia in a pediatric patient with ROHADD syndrome. / Anestesia en paciente pediátrico con síndrome de Rohhad.

Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD) syndrome is a rare entity that is characterised by its onset in healthy children at 2-4 years of age. It is a complex syndrome that includes, among other symptoms, rapid weight gain with hyperphagia, hypothalamic dysfunction, central hypoventilation, and autonomic dysregulation. The case is presented of a 10-year-old boy with a diagnosis of ROHHAD syndrome undergoing insertion of a port-a-cath under general anaesthesia, who developed complications during the anaesthetic procedure related to his illness. The peri-operative management of these patients represents a challenge for the anaesthetist, given the involvement of multiple systems and the frequent respiratory comorbidities associated with them. A summary is presented of some of the implications and anaesthetic considerations that must be taken into account in the management of these patients.