Lung gas transfer in children with sickle cell anaemia.

The impact of sickle cell anaemia (SCA) on respiratory function of children must be determined if their management is to be optimised. Pulmonary diffusing capacity (DL(CO)), corrected for haemoglobin (DL(COc)), therefore was assessed in 24 children with SCA and 24 ethnic matched controls, mean age 11 (range 7-16) years. To determine if any differences found correlated with other measures of lung function, spirometry was undertaken and lung volumes assessed. The SCA children compared to the controls had lower weight (p=0.01), body mass index (p=0.002), DL(CO) (p<0.0001), K(CO) (p=0.003), V(CSB) (p=0.01), FEV(1) (p<0.0001) and FVC (p<0.0001), but greater K(COc) (p=0.001). K(COc) results correlated significantly with PEF (r=-0.58, p=0.02), but not TLC(pleth) (p=0.36), FEV(1) (0.39) or FVC (p=0.36). In conclusion, when corrected for haemoglobin levels, the SCA children compared to controls of similar age had elevated gas transfer per unit lung volume results. Our results suggest this abnormality is independent of other lung function abnormalities.

Airway hyperresponsiveness and acute chest syndrome in children with sickle cell anemia.

To determine the occurrence and magnitude of airway hyperresponsiveness (AHR) in children with sickle cell anemia (SCA) who had or had not had acute chest syndrome (ACS) episodes. A subsidiary aim was to determine whether cold air and exercise challenge testing gave similar results in children with SCA. AHR would be greater in SCA children who had had an ACS episode compared to those who had not. Prospective observational study. Forty-two SCA children (median age of 11.5 [range 6.1-16.8] years); 12 children had been previously hospitalized for an ACS episode. AHR was assessed by the change in forced expiratory volume in 1 sec (FEV1) to a cold air challenge and in a subset of the children to an exercise challenge. A positive result to either challenge was deemed to have occurred if the FEV1 fell by at least 10% from the pre-challenge baseline. The magnitude of change in FEV1 following the cold air challenge was similar in children who had or had not had an ACS episode. Six children had a positive response to the cold air challenge (AHR); none had had an ACS hospitalization. Similar proportions of children responded to the cold air and exercise challenge and the magnitude of response to the two tests was similar. Some children, however, responded only to a cold air challenge and others only to an exercise challenge. SCA children who had had an ACS hospitalization episode compared to those who had not were not more likely to respond to a cold air challenge. Importantly, if AHR is to be correctly diagnosed, some SCA children will require to undergo both cold air and exercise challenge testing.

Temporal relationship of asthma to acute chest syndrome in sickle cell disease.

Acute chest syndrome (ACS) is an important cause of mortality and morbidity in children with sickle cell disease (SCD). An association between asthma and ACS has been reported. Our aims were to determine whether asthma was more common in SCD children than controls and the relationship of the timing of the SCD children's first ACS episode to a diagnosis of asthma. One hundred and sixty-five SCD children median age 8.2 (range 0.3-17.3) years and 151 similar ethnic origin and aged controls were prospectively recruited into the study and a detailed history was taken from all of the children to determine if they were taking anti-asthma medication. The medical records of the SCD children were examined to assess whether they had an ACS episode, the age this episode occurred and when any diagnosis of asthma had been made. A similar proportion of the SCD children and controls were taking anti-asthma medication (7% and 9%). Thirty-three SCD children had at least one ACS episode. More of the children who had an ACS compared to those who had not were taking anti-asthma medication (P = 0.02). The ACS children had been diagnosed as asthmatic at a median of 3.5 (range 0.5-7) years prior to their first ACS episode. In conclusion, these results suggest asthma exacerbations may predispose to ACS episodes.

Impact of acute chest syndrome on lung function of children with sickle cell disease.

OBJECTIVE: To test the hypothesis that children with sickle cell disease (SCD) who experienced an acute chest syndrome (ACS) hospitalization episode would have worse lung function than children with SCD without ACS episodes. STUDY DESIGN: Forced expiratory volume in 1 second (FEV(1)); forced vital capacity (FVC); FEV(1)/FVC ratio; peak expiratory flow (PEF); forced expiratory flow at 25% (FEF(25)), 50% (FEF(50)), and 75% (FEF(75)) of FVC; airway resistance (Raw); and lung volumes were compared in 20 children with ACS and 20 aged-matched children without ACS (median age, 11 years; range, 6 to 16 years). Fourteen age-matched pairs were assessed before and after bronchodilator use. RESULTS: The mean Raw (P = .03), TLC (P = .01), and RV (P = .003) were significantly higher in the group with ACS than in the group without ACS. There were no significant differences in the changes in lung function test results in response to bronchodilator administration between the 2 groups, but the children with ACS had a lower FEF(25) (P = .04) and FEF(75) (P = .03) pre-bronchodilator use and a lower mean FEV(1)/FVC ratio (P = .03) and FEF(75) (P = .03) post-bronchodilator use. CONCLUSIONS: Children with SCD who experienced an ACS hospitalization episode had significant differences in lung function compared with those who did not experience ACS episodes. Our results are compatible with the hypothesis that ACS episodes predispose children to increased airway obstruction.

Lung volumes in healthy Afro-Caribbean children aged 4-17 years.

Lung volumes in healthy children differ according to their ethnic origin. We wished to determine if any differences in the lung volumes of Afro-Caribbean (AC) children from those predicted by Caucasian reference values disappeared if the results were related to sitting height or to 90% or 77% of lung volumes predicted for height from Caucasian reference values based on standing height. We took, as our working hypothesis, that it is inappropriate to use Caucasian reference values to interpret data from Afro-Caribbean children, and that ethnic-specific reference values are required. This was a prospective, observational study. Subjects included 80 AC children with a median age of 9 (range, 4.3-17.8) years. Standing and sitting height were measured. Lung volumes were measured by body plethysmography (total lung capacity, TLC(pleth); functional residual capacity, FRC(pleth); and vital capacity, VC(pleth)), helium gas dilution (functional residual capacity, (FRC(He)), spirometry (forced expiratory volume in 1 sec, FEV(1)), and forced vital capacity (FVC). The lung volumes of AC children correlated significantly with standing height, but differed significantly from values predicted from Caucasian reference values based on standing height (P < 0.05). Significant differences remained for TLC(pleth), FRC(pleth), FRC(He), RV(pleth), VC(pleth), FEV(1), and FVC when the results were related to sitting height or 90% or 77% of values predicted from Caucasian reference values based on height (P < 0.05). Lung volumes in Afro-Caribbean children should be compared to ethnic-specific reference values.

Exhaled carbon monoxide levels in children with sickle cell disease.

UNLABELLED: It is important to measure the rate of haemolysis in patients with sickle cell disease (SCD) to identify aplastic crises and indirectly assess the rate of vaso-occlusion and sequestration. The aim of this study was to assess whether end-tidal carbon monoxide (ETCOc) levels in children with sickle cell disease (SCD) could be measured reproducibly, reflected haemolysis and whether they were elevated compared to those of similarly aged, ethnic matched children without SCD (controls). ETCOc levels were measured non-invasively in 87 SCD children (age range 2.3-17.6 years) and 26 age and ethnic origin matched healthy controls using an electro-chemical sensor. The within- and between- occasion reproducibilities were assessed in ten and 15 SCD children respectively. ETCOc levels of 15 SCD children undergoing regular transfusions were related to carboxyhaemoglobin, haemoglobin and bilirubin levels. The within and between occasions' mean intrasubject coefficients of reproducibility were 5% and 18% respectively. Positive correlations were found between the ETCOc and carboxyhaemoglobin ( P =0.007) and bilirubin ( P =0.02) levels, and a significant negative correlation between the ETCOc and haemoglobin ( P =0.0002) levels. The mean and SD ETCOc levels of the SCD children (4.9 ppm; SD 1.7 ppm) were significantly higher than that of the controls (mean 1.3 ppm; SD 0.4 ppm) (difference between means 3.60; 95% C.I. 2.93-4.28; P <0.0001). CONCLUSION: These results suggest that measurement of end-tidal carbon monoxide levels is a reliable and useful method to monitor haemolysis in children with sickle cell disease.