Leaf decomposition and flammability are largely decoupled across species in a tropical swamp forest despite sharing some predictive leaf functional traits

Decomposition and fire are major carbon pathways in many ecosystems, yet potential linkages between these processes are poorly understood. We test whether variability in decomposability and flammability across species are related to each other and to key plant functional traits in tropical swamp forests, where habitat degradation is elevating decomposition and fire regimes. Using senesced and fresh leaves of 22 swamp tree species in Singapore, we conducted an in situ decomposition experiment and a laboratory flammability experiment. We analysed 16 leaf physical and biochemical traits as predictors of decomposability and components of flammability: combustibility, ignitability and sustainability. Decomposability and flammability were largely decoupled across species, despite some shared predictive traits such as specific leaf area (SLA). Physical traits predicted that thicker leaves with a smaller SLA and volume decomposed faster, while various cation concentrations predicted flammability components, particularly ignitability. We show that flammability and decomposability of swamp forest leaves are decoupled because flammability is mostly driven by biochemical traits, while decomposition is driven by physical traits. Our approach identifies species that are slow to decompose and burn (e.g. Calophyllum tetrapterum and Xanthophyllum flavescens), which could be planted to mitigate carbon losses in tropical swamp reforestation.

Patients with gastro-oesophageal reflux disease and cough have impaired laryngopharyngeal mechanosensitivity

BACKGROUND

Laryngopharyngeal sensitivity (LPS) is important in preventing pulmonary aspiration and may be impaired by anaesthesia and stroke. It has been suggested that gastro-oesophageal reflux disease (GORD) may also impair LPS, although the underlying mechanism is unclear. The aim of this study was to compare LPS in patients with chronic cough and GORD with healthy subjects and to determine the effect of laryngopharyngeal infusions of both acid and normal saline on LPS.

METHODS

Fifteen patients with chronic cough and GORD and 10 healthy subjects without GORD underwent LPS testing using the fibreoptic endoscopic evaluation of swallowing with sensory testing (FEESST) technique. LPS, as measured by the lowest air pressure required to elicit the laryngeal adductor reflex (LAR), was determined both before and after laryngopharyngeal infusions of normal saline and 0.1 N hydrochloric acid performed on separate days.

RESULTS

The mean baseline LAR threshold of the patient group was significantly higher (9.5 mm Hg, range 6.0-10.0) than in normal subjects (3.68 mm Hg, range 2.5-5.0; p<0.01). Retest thresholds were not significantly different. In normal subjects LAR thresholds were significantly raised after acid but not after saline infusion (p = 0.005). There were no complications associated with the procedure.

CONCLUSIONS

Patients with cough and GORD have significantly reduced LPS to air stimuli compared with healthy subjects which could potentially result in an increased risk of aspiration. Exposure to small amounts of acid significantly impaired the sensory integrity of the laryngopharynx.

Accuracy of bedside clinical methods compared with fiberoptic endoscopic examination of swallowing (FEES) in determining the risk of aspiration in acute stroke patients

This prospective study was undertaken to determine the accuracy of bedside clinical methods compared with fiberoptic endoscopic examination of swallowing (FEES) for detecting aspiration in acute stroke patients. Fifty patients underwent an examination of their ability to swallow 50 ml of water in 10-ml aliquots. Later their oxygen saturation levels before and after swallowing 10 ml of water were measured using a pulse oximeter. Oxygen desaturation of more than 2%, was considered to be clinically significant. All patients then underwent a FEES assessment by a speech therapist and were followed up during their inpatient stay for evidence of aspiration pneumonia. The oxygen desaturation test had a sensitivity of 76.9% and specificity of 83.3% (chi2 = 18.154, p = 0.00002), while the 50-ml water swallow test had a sensitivity of 84.6% and specificity of 75.0% (chi2 = 18.001, p = 0.00002). However, when these two tests were combined into one test called "bedside aspiration," the sensitivity rose to 100% with a specificity of 70.8% (chi2 = 27.9, p = 0.000001). Five (10%) patients developed pneumonia during their inpatient stay. The relative risk (RR) of developing pneumonia, if there was evidence of aspiration on FEES, was 1.24 (1.03 < RR < 1.49). We conclude that the oxygen desaturation test combined with the 50-ml water swallow test is suitable as a screening test to identify all acute stroke patients at risk of aspiration for further evaluation and management.

Bedside assessment of swallowing: a useful screening tool for dysphagia in an acute geriatric ward

AIM

Dysphagia is common in the elderly and is associated with increased morbidity and mortality. We undertook a prospective study to determine the usefulness of a simple bedside swallowing test in terms of (1) detecting previously undiagnosed dysphagia, (2) agreement of the doctor's assessment with that of the speech therapist, (3) impact on subsequent feeding modality, (4) predicting risk of subsequent pneumonia.

METHOD

Patients in an acute geriatric ward who had no contra-indications to oral feeding were subjected to a bedside swallowing assessment by a geriatrician within 24 hours of admission. All patients found to be dysphagic were subsequently re-assessed by a speech therapist within 48 hours. In addition, every fifth patient deemed to have normal swallowing by the doctor was assessed by the speech therapist.

RESULTS

Sixty-five patients were studied. The doctor's assessment was in very good agreement with the assessment of the speech therapist (kappa = 0.87). Patients found to have dysphagia using the doctor's assessment protocol had an increased risk of developing pneumonia during their hospitalization (relative risk R.R.: 9.9 confidence interval C.I.: 1.2-81.2). Cough on swallowing and delayed swallowing were both found to be associated with an increased risk of developing pneumonia during the period of hospitalization (R.R.: 4.2, C.I.: 1.2-14.4; R.R.: 5.3, C.I.: 1.1-26.3 respectively).

CONCLUSION

A simple bedside swallowing test can be used as an effective screening tool in detecting hitherto undiagnosed dysphagia. The validity of this tool in the diagnosis of aspiration requires further investigation.

Swallowing impairment and feeding dependency in the hospitalised elderly

A prospective study was carried out to determine the prevalence of swallowing impairment and feeding dependency in an acute geriatric medicine unit in Singapore and the co-morbidity associated with it. A total of 211 patients were assessed over a 3-month period. Only 7.1% of patients gave a history of swallowing impairment prior to hospitalisation. We found that 29.4% of patients on admission and 28.2% on discharge had swallowing impairment, with a mortality of 8.1%. The prevalence of feeding dependency, as defined by the need for feeding assistance or tube feeding, was 26.5% before admission and 27.8% on discharge. The mode of feeding between the time of admission and discharge was changed in 14.9% of patients in response to the evolving medical condition. Swallowing impairment was significantly associated with the presence of dehydration (RR = 2.82, CI = 1.74-4.57), chest infection on admission (RR = 2.85, CI = 1.85-4.41), development of nosocomial chest infection (RR = 6.75, CI = 2.60-17.5), discharge to institutional care (RR = 2.8, CI = 1.51-3.47) and increased mortality (RR = 3.77, CI = 1.45-9.70). We concluded that swallowing impairment and feeding dependency are common in the elderly admitted to an acute geriatric unit. As elderly patients seldom inform clinicians of any underlying swallowing impairment and in view of the increased morbidity and mortality associated with this disability, it is important to screen for swallowing impairment. The high prevalence of feeding dependency adds to the burden of care in the ill elderly.