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Oximetry and peak expiratory flow in assessment of acute childhood asthma
CLINICAL AND LABORATORY OBSERVATIONS
Oximetry and peak expiratory flow in assessment of acute childhood asthma G a r y C. G e e l h o e d , MBBS,FRACP, Louis I. Landau, MD, FRACP, a n d Peter N. LeSou~f, MD, FRACP From the Department of RespiratoryMedicine, Princess Margaret Hospital for Children, Perth, Western Australia, Australia
Measurements made during forced expiration, such as peak expiratory flow and forced expiratory volume in 1 second, are currently accepted as being most useful in the assessment of airway obstruction in patients with acute asthma. I Recently we showed that arterial oxygen saturation is also a useful, objective measure of the severity of acute asthma in children coming to an emergency department, because Saoz measurement can predict which children will require admission to the hospital and which will need further medical care if sent home. 2 In this study, we compared the accuracy with which PEF and Sao2 values indicated the severity of symptoms and predicted relapse in children' with acute asthma who sought medical care in an emergency department.
METHODS Subjects. Children who came to the emergency department of Princess Margaret Hospital for Children with acute asthma and could perform adequately a PEF maneuver were included in the study. One hundred ten children, with a mean age 9.2 years (range 4.8 to 14.5 years), were studied: 65 children were receiving episodic treatment only; 45 were receiving regular treatment that included inhaled sodium cromog!ycate or beclomethasone or both; and 8 were taking oral doses of steroids regularly. Protocol, Measurements of Sao2 and PEF were made for all subjects when they arrived in the emergency department. Sao2 was measured by means of a finger probe connected to a model N-100 pulse oximeter (Nellcor Inc., Hayward, Calif.). The PEF value was recorded as the best of three forced expirations by means of a mini-Wright peak flow Supported in part (Dr. Geelhoed) by Asthma Foundation of Western Australia and T.V.W. Telethon Foundation. ' Submitted for publication May 5, 1989; accepted July t9, 1990. Reprint requests: G. C. Geelhoed, MBBS, FRACP, Princess Margaret Hospital for Children, Box D184 GPO, Perth, Western Australia 6001, Australia. 9/22/23875
meter (Clement Clarke International Ltd., London, England) and expressed as the percentage of predicted of normal values for height and sex) The children were then assessed and managed by emergency department staff unaware of the results of these measurements. Assessment may have included an independent measurement of PEF, but not of Sao2 in some children. For 73 of the children, Sao2 and PEF values were also recorded 30 minutes after the start of salbutamol nebulization (0.03 ml/kg of 0.5% solution up to 1 ml maximum, made up to 2 ml with 0.9% saline solution). Details of the present asthma attack and of the subject's past history of asthma were obtained at the time of the study. Consent was sought from the parents of all children considered suitable for inclusion in the study. No parent refused consent. Parents of the 110 children were contacted by telephone 10 days later and asked about the course of the acute epiFEVI PEF Sao2
I [
Forcedexpiratory volume in 1 second Peak expiratory flow Arterial oxygen saturation
r
sode--specifically whether their child had received medical care for ongoing asthma during the intervening time. Statistical analysis used an unpaired Student t test, chi-square analysis, and stepwise regression. Results are expressed as mean +_ SD.
RESULTS Seventy-nine children were sent home from the emergency department and 31 were admitted to the hospital. The admitted children's Sao2 and PEF values were lower than were the values of those sent home (p <0.001) (Table). Of the 79 subjects sent home, 15 children required additional medical care for ongoing asthma. The initial Sao2 at the original visit was lower for the children who required additional care than for those who did not (Table) (p <0.001). The PEF of those who returned to the hospital did not differ significantly from that of children who did not (Table)
907
908
Clinical and laboratory observations
The Journal of Pediatrics December 1990
T a b l e . Sao2, PEF, and asthmatic history of 110 children with acute asthma Sent h o m e
Sao2 (%) PEF (% predicted) Age (yr) Age at diagnosis (mo) Symptoms (hr) Past admissions Episodic treatment (yes/no)?
Admitted to hospital (n = 31)
Sent home (n = 79)
p*
Returned 15
Did not return 64
p*
93.0 _+ 2.7 43.3 _+ 23.1 9.1 _+ 2.9 27 _+ 26 67 _+ 87 9.7 + 10.8 14/17
95.0 _+ 2.2 63.5 _+ 25.2 9.0 _+ 2.4 30 _+ 25 75 _+ 88 5,2 _+ 8.2 51/28
<0.05 <0.05 NS NS NS <0.02 NS
93.1 _+ 2.6 59.1 _+ 15.3 8.8 _+ 2.5 30 _+ 26 66 + 88 4.7 _+ 5.6 9/6
95.4 _+ 1.9 64.6 -+ 27.0 9.1 -+ 2.4 31 _+25 77 _+ 88 5.3 -+ 8.8 42/22
<0.05 NS NS NS NS NS NS
NS, Not significant. Values (exceptp values and those for episodictreatment) are expressed as mean _+SD. *Significanceis based on differencesbetweengroups. tChi-square test.
(p = 0.46). Children with a lower Sao2 tended to be admitted to the hospital, or to seek additional care if sent home from the emergency department. These children also had a low PEF, but so did manY children who were sent home and did not return. PEF was therefore less discriminatory than a low Sao2. For postbronchodilator measurements, Sao2 and PEF were each lower for the 26 children who were admitted (mean Sao2 93.6% [SD 2.2%] and PEF 48.0% predicted [SD 20.5%], respectively) than for the 47 sent home (mean Sao2 95.6% [SD 2.1%] and PEF 80.5% predicted [SD 23.2%] ). For these 47 children, the postbronchodilator Sao2 level was lower in the 11 children who returned for care than the 36 who did not (mean Sao2 94.3% [SD 2.8%] vs 96.0% [SD 1.7%]), respectively (p <0.05), whereas corresponding PEF values were not different (79.9% predicted [SD 24.7%] vs 82.6% predicted [SD 18.6%]). There were no differences in duration of symptoms, age at diagnosis, current age, and prior treatment between those admitted and those sent home, and between those sent home who returned for care and those sent home who did not. Subjects admitted had more past admissions than those sent home (p <0.02), but there was no difference in the number of past admissions between those sent home who returned and those sent home who did not (Table). Stepwise regression by means of Statview 512 software used on an Apple Macintosh computer showed Sao2, PEF, and number of past admissions to be related to the likelihood of admission, but only Sao2 was related to return for medical care. DISCUSSION Assessment of severity and outcome of acute childhood asthma is difficult because there is no recognized objective "gold standard." PEF and FEVl have been advocated as the best objective measurements for assessing acute asthma in the emergency department, 1 but in asthma, all physiologic
disturbance is more indicative of severity and outcome than is just major airway obstruction. In our study the PEF value was lower in the group of children admitted to the hospital than in those sent home but in the latter group did not differ between those who returned for medical care and those who did not. In contrast, the Sao2 value was lower both in those admitted than those sent home and in those who returned for care than those who did not. These data suggest that both PEF and Sao2 can be useful in judging the severity of acute asthma, but Sao2 has greater potential to predict outcome in those not admitted. In previous studies, PEF and FEVI were disappointing in predicting relapse: initial PEF and FEVb either alone or as a part of more complex scoring system, failed to predict relapse in patients sent home after receiving treatment for acute asthma. 46 The Sao2 measurement, on the other hand, not only predicts relapse but also has practical advantages over spirometry. Tests involving forced expiration cannot be employed in patients who are too young or too ill to cooperate, whereas oximetry can be used for patients of all ages because it requires minimal cooperation from the subject. Why should oximetry be more accurate than PEF measurement in predicting children who will return to the hospital? First, hypoxia may impair a child's ability to perform a Peak flow maneuver but will not interfere with the measurement of Sao2. Second, the Sao2 values have a narrow normal range that applies to all ages. In contrast, the PEF values must be related to a wide normal range in younger children because of the homoscedastic relationship of its variability to age. 3 Third, and perhaps more likely, the Sao2 value may more accurately reflect the end result of the many pathologic changes that occur in acute asthma, including airway obstruction at all levels of the bronchial tree and ventilation-perfusion inequality. The PEF value predominantly reflects major airway obstruction. Roca et al. 7 recently showed that airway obstruction and ventilation-
Volume 117 Number 6
Clinical and ~
perfusion inequality follow different time courses during an acute attack of asthma; PEF values improve well before Sa02 values. This prolonged depression in Sa02 and its superiority in predicting relapse suggest that oximetry may reflect a more fundamental physiologic aspect of the asthmatic process, such as the extent and inhomogeneity of airway narrowing caused by inflammation.
4. 5.
6.
REFERENCES 7.
1. Acute asthma [Editorial]. Lancet 1986;t:13l-2. 2. Geelhoed GC, Landau LI, Le Sou~f PN. Predictive value of oxygen saturation in emergency evatuaton of asthmatic children. Br Med J 1988;295:297-8. 3. Godfrey S, KamburoffPL, Nairn JR. Spirometry, lung volume
observations
909
and airway resistance in normal children aged 5 to 18 years. Br J Dis Chest 1970;64:15-24. Centor RM, Yarbrough B, Wood JP. Inability to predict relapse in acute asthma. N Engl J Mcd 1984;310:577-80. Rose CC, Murphy JG, Schwartz JS. Performance of an index predicting the responseof patients with acute bronchial asthma to intensive emergency department treatment. N Engl J Med 1984;310:573-7. Kelsen SG, Kelsen DP, Fleegler BF, Jones RC, Rodman T. Emergency room assessment and treatment of patients with acute asthma. Am J Med 1978;64:622-8. Roca J, Ramis LI, Rodriguez-RolsinR, Ballester E, Montserrat JM, Wagner PD. Serial relationships between ventilationperfusion inequality and spirometry in acute severe asthma requiring hospitalization.Am Rev Respir Dis 1988;137:1055-61.
Association between prenatal cocaine exposure and sudden infant death syndrome D a v i d J. Durand, MD, A l e x M. Espinoza, MD, a n d Bruce G. Nickerson, MD From the Divisionsof Neonatology and Pediatric Pulmonology, Children'sHospital, and the Department of Pediatrics, Highland General Hospital, Oakland, California
Since Chasnoff et al. 1 first described abnormalities in infants who were exposed to cocaine in utero, the problem of prenatal cocaine exposure has become widely recognized. We, as well as many others, have described multiple abnormalities in cocaine-exposed infants, including intrauterine growth retardation, microcephaly, and abnormal behavior. 2-s There are conflicting data on the relationship between prenatal cocaine exposure and the risk of sudden infant death syndrome. Chasnoff et al. 6 reported a SIDS incidence of 15% (150/1000) among 66 infants who were cocaine exposed. However, in a study of 275 cocaine-exposed infants, Bauchner et al. 7 found a SIDS incidence of 5.6/1000, compared with an incidence of 4.9/1000 among nonexposed infants, a difference that was not significant. We reviewed our experience with cocaine-exposed infants in a large metropolitan county hospital to determine whether SlDS was more likely to occur in this group of infants.
Submitted for publication May l, 1990; accepted Sept. 10, 1990. Reprint requests: David J. Durand, MD, Divisionof Neonatology, Children's Hospital, 747 52nd St., Oakland, CA 94609. 9/22/25395
METHODS In 1986 we began aggressively screening for cocaine in mothers and infants delivered at Highland General Hospital, which is located in Oakland, Calif., and is the county hospital for Alameda County. All women admitted to the delivery service were questioned about drug use, before and during pregnancy, by both obstetric and pediatric staff who were experienced in taking drug histories. Urine drug tests [
SIDS
Sudden infant death syndrome
[
See related articles, pp. 876 and 904. were performed on both mother and infant if any of the following were present: history of drug use before pregnancy, history of drug use during pregnancy, evidence of drug use or withdrawal on maternal examination, or evidence of drug exposure in the infant. The Alameda County Health Care Services Agency maintains a registry of all infants who died of SIDS in the county. All SIDS deaths were confirmed by autopsy. By cross-referencing the infants who were listed in the registry with the list of infants delivered at Highland General Hospital, we were able to obtain an estimate of the incidence of
Oximetry and peak expiratory flow in assessment of acute childhood asthma G a r y C. G e e l h o e d , MBBS,FRACP, Louis I. Landau, MD, FRACP, a n d Peter N. LeSou~f, MD, FRACP From the Department of RespiratoryMedicine, Princess Margaret Hospital for Children, Perth, Western Australia, Australia
Measurements made during forced expiration, such as peak expiratory flow and forced expiratory volume in 1 second, are currently accepted as being most useful in the assessment of airway obstruction in patients with acute asthma. I Recently we showed that arterial oxygen saturation is also a useful, objective measure of the severity of acute asthma in children coming to an emergency department, because Saoz measurement can predict which children will require admission to the hospital and which will need further medical care if sent home. 2 In this study, we compared the accuracy with which PEF and Sao2 values indicated the severity of symptoms and predicted relapse in children' with acute asthma who sought medical care in an emergency department.
METHODS Subjects. Children who came to the emergency department of Princess Margaret Hospital for Children with acute asthma and could perform adequately a PEF maneuver were included in the study. One hundred ten children, with a mean age 9.2 years (range 4.8 to 14.5 years), were studied: 65 children were receiving episodic treatment only; 45 were receiving regular treatment that included inhaled sodium cromog!ycate or beclomethasone or both; and 8 were taking oral doses of steroids regularly. Protocol, Measurements of Sao2 and PEF were made for all subjects when they arrived in the emergency department. Sao2 was measured by means of a finger probe connected to a model N-100 pulse oximeter (Nellcor Inc., Hayward, Calif.). The PEF value was recorded as the best of three forced expirations by means of a mini-Wright peak flow Supported in part (Dr. Geelhoed) by Asthma Foundation of Western Australia and T.V.W. Telethon Foundation. ' Submitted for publication May 5, 1989; accepted July t9, 1990. Reprint requests: G. C. Geelhoed, MBBS, FRACP, Princess Margaret Hospital for Children, Box D184 GPO, Perth, Western Australia 6001, Australia. 9/22/23875
meter (Clement Clarke International Ltd., London, England) and expressed as the percentage of predicted of normal values for height and sex) The children were then assessed and managed by emergency department staff unaware of the results of these measurements. Assessment may have included an independent measurement of PEF, but not of Sao2 in some children. For 73 of the children, Sao2 and PEF values were also recorded 30 minutes after the start of salbutamol nebulization (0.03 ml/kg of 0.5% solution up to 1 ml maximum, made up to 2 ml with 0.9% saline solution). Details of the present asthma attack and of the subject's past history of asthma were obtained at the time of the study. Consent was sought from the parents of all children considered suitable for inclusion in the study. No parent refused consent. Parents of the 110 children were contacted by telephone 10 days later and asked about the course of the acute epiFEVI PEF Sao2
I [
Forcedexpiratory volume in 1 second Peak expiratory flow Arterial oxygen saturation
r
sode--specifically whether their child had received medical care for ongoing asthma during the intervening time. Statistical analysis used an unpaired Student t test, chi-square analysis, and stepwise regression. Results are expressed as mean +_ SD.
RESULTS Seventy-nine children were sent home from the emergency department and 31 were admitted to the hospital. The admitted children's Sao2 and PEF values were lower than were the values of those sent home (p <0.001) (Table). Of the 79 subjects sent home, 15 children required additional medical care for ongoing asthma. The initial Sao2 at the original visit was lower for the children who required additional care than for those who did not (Table) (p <0.001). The PEF of those who returned to the hospital did not differ significantly from that of children who did not (Table)
907
908
Clinical and laboratory observations
The Journal of Pediatrics December 1990
T a b l e . Sao2, PEF, and asthmatic history of 110 children with acute asthma Sent h o m e
Sao2 (%) PEF (% predicted) Age (yr) Age at diagnosis (mo) Symptoms (hr) Past admissions Episodic treatment (yes/no)?
Admitted to hospital (n = 31)
Sent home (n = 79)
p*
Returned 15
Did not return 64
p*
93.0 _+ 2.7 43.3 _+ 23.1 9.1 _+ 2.9 27 _+ 26 67 _+ 87 9.7 + 10.8 14/17
95.0 _+ 2.2 63.5 _+ 25.2 9.0 _+ 2.4 30 _+ 25 75 _+ 88 5,2 _+ 8.2 51/28
<0.05 <0.05 NS NS NS <0.02 NS
93.1 _+ 2.6 59.1 _+ 15.3 8.8 _+ 2.5 30 _+ 26 66 + 88 4.7 _+ 5.6 9/6
95.4 _+ 1.9 64.6 -+ 27.0 9.1 -+ 2.4 31 _+25 77 _+ 88 5.3 -+ 8.8 42/22
<0.05 NS NS NS NS NS NS
NS, Not significant. Values (exceptp values and those for episodictreatment) are expressed as mean _+SD. *Significanceis based on differencesbetweengroups. tChi-square test.
(p = 0.46). Children with a lower Sao2 tended to be admitted to the hospital, or to seek additional care if sent home from the emergency department. These children also had a low PEF, but so did manY children who were sent home and did not return. PEF was therefore less discriminatory than a low Sao2. For postbronchodilator measurements, Sao2 and PEF were each lower for the 26 children who were admitted (mean Sao2 93.6% [SD 2.2%] and PEF 48.0% predicted [SD 20.5%], respectively) than for the 47 sent home (mean Sao2 95.6% [SD 2.1%] and PEF 80.5% predicted [SD 23.2%] ). For these 47 children, the postbronchodilator Sao2 level was lower in the 11 children who returned for care than the 36 who did not (mean Sao2 94.3% [SD 2.8%] vs 96.0% [SD 1.7%]), respectively (p <0.05), whereas corresponding PEF values were not different (79.9% predicted [SD 24.7%] vs 82.6% predicted [SD 18.6%]). There were no differences in duration of symptoms, age at diagnosis, current age, and prior treatment between those admitted and those sent home, and between those sent home who returned for care and those sent home who did not. Subjects admitted had more past admissions than those sent home (p <0.02), but there was no difference in the number of past admissions between those sent home who returned and those sent home who did not (Table). Stepwise regression by means of Statview 512 software used on an Apple Macintosh computer showed Sao2, PEF, and number of past admissions to be related to the likelihood of admission, but only Sao2 was related to return for medical care. DISCUSSION Assessment of severity and outcome of acute childhood asthma is difficult because there is no recognized objective "gold standard." PEF and FEVl have been advocated as the best objective measurements for assessing acute asthma in the emergency department, 1 but in asthma, all physiologic
disturbance is more indicative of severity and outcome than is just major airway obstruction. In our study the PEF value was lower in the group of children admitted to the hospital than in those sent home but in the latter group did not differ between those who returned for medical care and those who did not. In contrast, the Sao2 value was lower both in those admitted than those sent home and in those who returned for care than those who did not. These data suggest that both PEF and Sao2 can be useful in judging the severity of acute asthma, but Sao2 has greater potential to predict outcome in those not admitted. In previous studies, PEF and FEVI were disappointing in predicting relapse: initial PEF and FEVb either alone or as a part of more complex scoring system, failed to predict relapse in patients sent home after receiving treatment for acute asthma. 46 The Sao2 measurement, on the other hand, not only predicts relapse but also has practical advantages over spirometry. Tests involving forced expiration cannot be employed in patients who are too young or too ill to cooperate, whereas oximetry can be used for patients of all ages because it requires minimal cooperation from the subject. Why should oximetry be more accurate than PEF measurement in predicting children who will return to the hospital? First, hypoxia may impair a child's ability to perform a Peak flow maneuver but will not interfere with the measurement of Sao2. Second, the Sao2 values have a narrow normal range that applies to all ages. In contrast, the PEF values must be related to a wide normal range in younger children because of the homoscedastic relationship of its variability to age. 3 Third, and perhaps more likely, the Sao2 value may more accurately reflect the end result of the many pathologic changes that occur in acute asthma, including airway obstruction at all levels of the bronchial tree and ventilation-perfusion inequality. The PEF value predominantly reflects major airway obstruction. Roca et al. 7 recently showed that airway obstruction and ventilation-
Volume 117 Number 6
Clinical and ~
perfusion inequality follow different time courses during an acute attack of asthma; PEF values improve well before Sa02 values. This prolonged depression in Sa02 and its superiority in predicting relapse suggest that oximetry may reflect a more fundamental physiologic aspect of the asthmatic process, such as the extent and inhomogeneity of airway narrowing caused by inflammation.
4. 5.
6.
REFERENCES 7.
1. Acute asthma [Editorial]. Lancet 1986;t:13l-2. 2. Geelhoed GC, Landau LI, Le Sou~f PN. Predictive value of oxygen saturation in emergency evatuaton of asthmatic children. Br Med J 1988;295:297-8. 3. Godfrey S, KamburoffPL, Nairn JR. Spirometry, lung volume
observations
909
and airway resistance in normal children aged 5 to 18 years. Br J Dis Chest 1970;64:15-24. Centor RM, Yarbrough B, Wood JP. Inability to predict relapse in acute asthma. N Engl J Mcd 1984;310:577-80. Rose CC, Murphy JG, Schwartz JS. Performance of an index predicting the responseof patients with acute bronchial asthma to intensive emergency department treatment. N Engl J Med 1984;310:573-7. Kelsen SG, Kelsen DP, Fleegler BF, Jones RC, Rodman T. Emergency room assessment and treatment of patients with acute asthma. Am J Med 1978;64:622-8. Roca J, Ramis LI, Rodriguez-RolsinR, Ballester E, Montserrat JM, Wagner PD. Serial relationships between ventilationperfusion inequality and spirometry in acute severe asthma requiring hospitalization.Am Rev Respir Dis 1988;137:1055-61.
Association between prenatal cocaine exposure and sudden infant death syndrome D a v i d J. Durand, MD, A l e x M. Espinoza, MD, a n d Bruce G. Nickerson, MD From the Divisionsof Neonatology and Pediatric Pulmonology, Children'sHospital, and the Department of Pediatrics, Highland General Hospital, Oakland, California
Since Chasnoff et al. 1 first described abnormalities in infants who were exposed to cocaine in utero, the problem of prenatal cocaine exposure has become widely recognized. We, as well as many others, have described multiple abnormalities in cocaine-exposed infants, including intrauterine growth retardation, microcephaly, and abnormal behavior. 2-s There are conflicting data on the relationship between prenatal cocaine exposure and the risk of sudden infant death syndrome. Chasnoff et al. 6 reported a SIDS incidence of 15% (150/1000) among 66 infants who were cocaine exposed. However, in a study of 275 cocaine-exposed infants, Bauchner et al. 7 found a SIDS incidence of 5.6/1000, compared with an incidence of 4.9/1000 among nonexposed infants, a difference that was not significant. We reviewed our experience with cocaine-exposed infants in a large metropolitan county hospital to determine whether SlDS was more likely to occur in this group of infants.
Submitted for publication May l, 1990; accepted Sept. 10, 1990. Reprint requests: David J. Durand, MD, Divisionof Neonatology, Children's Hospital, 747 52nd St., Oakland, CA 94609. 9/22/25395
METHODS In 1986 we began aggressively screening for cocaine in mothers and infants delivered at Highland General Hospital, which is located in Oakland, Calif., and is the county hospital for Alameda County. All women admitted to the delivery service were questioned about drug use, before and during pregnancy, by both obstetric and pediatric staff who were experienced in taking drug histories. Urine drug tests [
SIDS
Sudden infant death syndrome
[
See related articles, pp. 876 and 904. were performed on both mother and infant if any of the following were present: history of drug use before pregnancy, history of drug use during pregnancy, evidence of drug use or withdrawal on maternal examination, or evidence of drug exposure in the infant. The Alameda County Health Care Services Agency maintains a registry of all infants who died of SIDS in the county. All SIDS deaths were confirmed by autopsy. By cross-referencing the infants who were listed in the registry with the list of infants delivered at Highland General Hospital, we were able to obtain an estimate of the incidence of