Effect of altitude on spirometric parameters and the performance of peak flow meters

BACKGROUND

Portable peak flow meters are used in clinical practice for measurement of peak expiratory flow (PEF) at many different altitudes throughout the world. Some PEF meters are affected by gas density. This study was undertaken to establish which type of meter is best for use above sea level and to determine changes in spirometric measurements at altitude.

METHODS

The variable orifice mini-Wright peak flow meter was compared with the fixed orifice Micro Medical Microplus turbine microspirometer at sea level and at Everest Base Camp (5300 m). Fifty one members of the 1994 British Mount Everest Medical Expedition were studied (age range, 19-55).

RESULTS

Mean forced vital capacity (FVC) fell by 5% and PEF rose by 25.5%. However, PEF recorded with the mini-Wright peak flow meter underestimated PEF by 31%, giving readings 6.6% below sea level values. FVC was lowest in the mornings and did not improve significantly with acclimatisation. Lower PEF values were observed on morning readings and were associated with higher acute mountain sickness scores, although the latter may reflect decreased effort in those with acute mountain sickness. There was no change in forced expiratory volume in one second (FEV1) at altitude when measured with the turbine microspirometer.

CONCLUSIONS

The cause of the fall in FVC at 5300 m is unknown but may be attributed to changes in lung blood volume, interstitial lung oedema, or early airways closure. Variable orifice peak flow meters grossly underestimate PEF at altitude and fixed orifice devices are therefore preferable where accurate PEF measurements are required above sea level.

ECG and echocardiographic diagnosis of pulmonary thromboembolism associated with central venous lines

The aim was to establish the prevalence of pulmonary embolism in 21 children (median age 12 months; range 5-132 months) with central venous lines in situ > 3 months (median 10 months; range 3-47). Twelve-lead electrocardiograms (ECGs) and echocardiograms were analysed in a retrospective study using ECG and echocardiographic criteria for pulmonary embolism-previously established and validated in adult patients- and standard paediatric ECG values as control data. Patients were scored as having definite (n = 7), probable (n = 5), or no pulmonary embolism (n = 9). Overall 57% of ECGs showed abnormalities compatible with pulmonary embolism. In two patients, serial ECGs obtained during an acute cardiorespiratory illness showed cumulative changes diagnostic of pulmonary embolism. Eight of 12 patients with abnormal ECGs had echocardiography; in seven of these (88%) the right ventricular end diastolic diameter was > 2SD above the mean value for age. Twelve of the patients included in this study have died; two died following an acute respiratory illness. There was postmortem evidence of pulmonary thromboembolism in both of the two children for whom necropsy information was available. The data suggest that pulmonary embolism is common in children who have central venous lines in situ for > 3 months. Serial studies are of value in some patients. Pulmonary embolism may compromise the long term survival of children with small bowel failure and preclude consideration for liver and small bowel transplantation.

Case report: pulmonary calcification after liver transplantation in children

Pulmonary calcification following liver transplantation is a recognized phenomenon in adults but has not been previously described in children. We describe two children who developed pulmonary calcification after liver transplantation. Pulmonary calcification should be considered after liver transplantation when radiographic changes fail to resolve with appropriate treatment.

Auditory localizing acuity during acute exposure to altitude

We have investigated the effects of hypoxia in an altitude chamber on auditory localization. Ten volunteers were tested at 18,000 ft (5,486 m), and through 12,000, 8,000, and 5,000 ft (3,657, 2,438, and 1,524 m) with directional sounds recorded via a dummy head microphone and presented binaurally. The sequence encompassed the horizontal plane. We found large intersubject variation in the response to altitude but absolute error (unsigned error) was always increased: at 18,000 ft the mean effect for the group was highly significant (p < 0.00001). The effect persisted during descent (p < 0.001 at 12,000 ft). Directional bias (mean signed error) was also substantially affected in four subjects, in that sounds originally presented in the lateral quadrants were mislocated further to the rear (p < 0.05). The incidence of front/behind confusion was not affected by altitude. We discuss these findings in relation to the proposed use of directional sounds for flight navigation and warning systems.

Different subtypes of pseudohypoparathyroidism in the same family with an unusual psychiatric presentation of the index case

A 13 year old Asian girl presenting with apparent hysterical paralysis and subsequent rapid cycling bipolar mood disorder was found to have biochemical evidence of pseudohypoparathyroidism type II. The mood disorder responded to treatment of the pseudohypoparathyroidism with a vitamin D analogue. Investigation of her parents and siblings showed phenotypes consistent with two distinct types of pseudohypoparathyroidism (type I and type II) in different family members.

Altitude-dependent changes of directional hearing in mountaineers

This study demonstrates apparent deterioration in the ability to localize sound associated with acute exposure to high altitude in ten subjects on three mountaineering expeditions. Furthermore, the auditory localization errors improved to sea level values after a period of acclimatization. Occurring at altitudes where overt neurological symptoms are not usually seen, impairment of sensory perception may explain the increase in accidental deaths associated with altitude exposure due to disorientation and misjudgment but before hypoxia is evident.

Neonatal hepatitis induced by alpha 1-antitrypsin: a transgenic mouse model

Transgenic mouse lineages were established that carry the normal (M) or mutant (Z) alleles of the human alpha 1-antitrypsin (alpha 1-Pi) gene. All of the alpha 1-Pi transgenic mice expressed the human protein in the liver, cartilage, gut, kidneys, lymphoid macrophages, and thymus. The human M-allele protein was secreted normally into the serum. However, the human Z-allele protein accumulated in several cell types, but particularly in hepatocytes, and was found in serum in tenfold lower concentrations than the M-allele protein. Mice in one lineage carrying the mutant Z allele expressed high levels of human alpha 1-Pi RNA and displayed significant runting (50% of normal weight) in the neonatal period. This lineage was found to have alpha 1-Pi-induced liver pathology in the neonatal period, concomitant with the accumulation of human Z protein in diastase-resistant cytoplasmic globules that could be revealed in the Periodic acid-Schiff reaction (PAS). The phenotype of mice in the strain expressing high levels of the Z allele is remarkably similar to human neonatal hepatitis, and this strain may prove to be a useful animal model for studying this disease.

Nephroptosis: a cause of renal pain and a potential cause of inaccurate split renal function determination

We present 3 cases of nephroptosis encountered in young females over a 6-month period which posed diagnostic difficulties and gave inaccurate split renal function determinations until the true situation was disclosed. A syndrome is described of clinical presentation with right upper quadrant pain, erect hippuran renography showing an apparently small right kidney and reduced function but with normal time to peak and elimination phase on the curve (the "miniaturised" renogram) and erect and supine DMSA scintigraphy which confirms the diagnosis of abnormal renal mobility. Guidelines are suggested by which nephroptosis can be recognised and assessed in urological and nuclear medicine practice.

Accuracy and reproducibility of a new contrast clearance method for the determination of glomerular filtration rate

A new method for determining the glomerular filtration rate was analysed prospectively. The method uses an x ray fluorescence technique to measure disappearance from the plasma of injected non-ionic iodinated contrast media. Eighty seven patients were studied. Fifty four had an intravenous dose of 100 ml iohexol (Omnipaque) and 33 had 50 ml iohexol. Clearances of chromium-51 labelled edetic acid (51Cr-EDTA) were measured simultaneously. In the patients given 100 ml iohexol there was excellent correlation with 51Cr-EDTA clearance (r = 0.90). The correlation using 50 ml iohexol was also good (r = 0.85). Correlation between creatinine clearance and clearance of 51Cr-EDTA in 33 patients was less satisfactory (r = 0.69). There were no adverse reactions to the contrast media. The equipment used for measuring contrast clearance was robust and simple to operate. Freezing plasma samples in 10 studies and re-examining them weekly for six weeks showed no significant variation in results; hence reproducibility was good. This new and accurate method for determining the glomerular filtration rate merits further study and might find a useful place in routine clinical practice.

Rotavirus and its Genotype Distribution among Children Less than Three Years Presenting with Acute Watery Diarrhoea to a General Hospital in Urban Nepal

Introduction: Viruses are the most common cause for diarrhoea in infants and small children. Rotavirus is the most frequent viral etiology, causing 125 million episodes of infantile diarrhoea and over 600,000 deaths per year. Materials and methods: A cross sectional study between January and March 2008 was conducted at Patan Hospital, Kathmandu to find out the prevalence of rotavirus among children < 3 years with watery diarrhoea and to identify common strains of rotavirus in the study population. Testing for rotavirus was undertaken by using Rota/Adeno screen Dipstick M583CE. Rotavirus strain identification was done at Nagasaki University Japan. Data was analyzed using SPSS® for Windows V 15.0 software. Results: 119 children with acute watery diarrhoea were enrolled. Rotavirus antigen was found in 63 cases (53%). The highest percentage of rotavirus infection was found in the second six months of life. Among the children with positive rotavirus antigen, the median age was 10 months (IRQ 8.00). The most predominant strain of rotavirus identified was G12 followed by G9 and G1. Most predominant G and P combination was G9 P[8] followed by G12P[6]. Conclusion: The study has shown the prevalence of unusual serotypes of rotavirus. Though rotavirus vaccine has been studied, used widely and found to be very effective, none of the vaccine efficacy studies have included common serotypes identified in Nepal. Level of protection conferred by infant immunization with the current rotavirus vaccines against the strains circulating in Nepal is unknown and careful surveillance through vaccine implementation is needed. Key words: Diarrhoea; Nepal; rotavirus; rotavirus genotypes; vaccine DOI: 10.3126/jnps.v31i2.4641 J Nep Paedtr Soc 2010;31(2):110-115