ClinicalRadiology (1981) 32, 281-282 0009-9260/81/00620281502.00 © 1981 Royal CoUege of Radiologists

Value of Chest Radiographs in Severe Acute Asthma IAN S. PETHERAM*, I. H. KERR and J. V. COLLINS

Brompton Hospital, Fulham Road, London

Chest radiographs were obtained in 117 adults admitted with severe acute asthma. In 10 (9%) patients abnor- malities were seen that affected management and in nine the presence of pulmonary collapse or consolidation was shown which was not detected by clinical examinations. Over-inflation Was common and correlated signifi- cantly with tachycardia, pulsus paradoxus and decrease in FEV1. Bronchial wall thickening was common and prominence of hilar vessels was also noted in a few patients. Chest radiography is strongly recommended in severe exacerbations of asthma and antero-posterior views are adequate for interpretation.

Radiological abnormalities have been reported in about a fifth of children who have acute exacer- bations of asthma (Eggleston, et al., 1974) but the frequency and importance of such abnormalities has not previously been assessed in adults. Chest radio- graphs taken at the time of admission of adults with severe acute asthma were examined for this purpose.

METHODS

Chest radiographs were obtained in 117 consecu- tive adults admitted with severe acute asthma. Of these four were standard postero-anterior views taken in the radiology department. The remainder were antero-posterior views taken on the ward with a mobile X-ray unit. Routine postero-anterior views were taken in the radiology department in 69 patients after their recovery. Patients with chronic bronchitis, emphysema, bronchiectasis or bronchopulmonary aspergillosis were excluded. On admission any previous data regarding asthma, tachycardia, pulsus paradoxus and peak flow rate (PFR) were recorded. Arterial blood gas tensions were measured in 114. Forced expiratory volume in 1 s (FEV1)and forced vital capacity (FVC) were obtained in 70 patients. The radiographs were assessed in random order by a single observer (I.H.K.) without knowledge of the clinical details. Pulmonary over-inflation was considered present if two of the following criteria were observed:

(i) Lung height equal to or greater than lung width measured as described by Simon et al. (1972).

(ii) Right hemidiaphragm at or below sixth inter- space anteriorly.

*Present appointment: Consultant Physician, Newport Chest Clinic, 129 Stow Hill, Newport, Gwent.

(iii) Cardiac diameter less than 11.5 cm (Simon et al., 1973).

(iv) The ratio of lung height to width reduced on the follow-up radiograph, compared with that on the admission radiograph.

Bronchial wall thickening, prominence of hllar vessels, consolidation or collapse and pneumothorax or pneumomediastinum were specifically looked for and any other abnormalities were noted. Prominence of hilar vessels and bronchial wall thickening are subjective assessments and were classified as definite, possible or absent. Differences in clinical measure- ments between patients with and without over- inflation were investigated by examining the distri- bution of severity by X 2 test.

RESULTS

The mean age of the patients was 41 years (range 13-75); 40 were men and 77 were women. Values of clinical measurelnents made on admission are shown in Table 1. Ninety-two (70%) of the admis- sion radiographs were abnormal (Table 2). Patients with radiographic signs of over-inflation had more severe pulsus paradoxus (P< 0.01 X2), faster heart rates (P< 0.025 X 2) and lower FEV1 (P< 0.025 X2). The presence af over-inflation was not related to age, sex, atopic status, PFR, FVC or arterial blood gas tensions. Definite bronchial wall thickening was present on follow-up in a third of patients who had this sign on admission but prominent hilar vessels were not seen after recovery. Over-inflation, bronchial wall thickening, prominence of hilar vessels and pulmonary collapse or consolidation showed no significant relationship to the total duration of asthma or to the duration of the acute episode.

282 CLINICAL RADIOLOGY

Table 1 - Results of measurements made on admission (mean values -+ s.d.)

Heart rate Pulsus PEFR FE V 1 FVC PaO 2 PaCO 2 (per min) paradoxus (litre/min) (litre) (litre) (kPal mmHg) (kPa i mmHg)

(mmHg)

105.4 ± 18.8 16.4 ± 14.2 105 ± 41.3 0.7 ± 0.3 1.4 -+ 0.6 8.12 ± 1.7 4.85 ± 1.03 61.2 ± 12.6 36.4 ± 7.7

Table 2 - Incidence o f radiographieal abnormalities found on admission and after recovery

Number Over- Bronchial wall Prominence o f hilar Consolidation Pneumo- (%) inflation ° thickening vessels collapse mediastinum

Definite Possible Definite Possible

Admission 117 45 (39) 42 (36) 15 (13) 5 (4) 4 (3) 9 (8) 1 (0.9) Remission 69 13 (19) 14 (20) 2 (3) 0 0 0 0

D I S C U S S I O N

From this s tudy we suggest that a chest radio- graph should be obtained in every severe exacerbation of asthma because of the surprisingly high incidence o f unsuspected pulmonary collapse or consolidation and the potential danger of an undiagnosed pneumo- thorax or pneumomediast inum. The chest radio- graphs of 10 patients taken on admission showed abnormalities which influenced their management. In the nine in whom consolidation or collapse was detected radiologically, this was not recognised on clinical examination. In the one pat ient who had a pneumomediast inum, this was suspected clinically because of subcutaneous emphysema in the neck. Pneumothorax and pneumomediast inum are fortu- nately uncommon complications o f severe asthma but if small are difficult to detect by clinical exami- nation. Recognition of their presence is essential since they may lead to dangerous respiratory embarrass- ment, especially if mechanical ventilation becomes necessary. Over-inflation, bronchial wall thickening and prominence of hilar vessels were common findings but this was expected from the physiological and pathological derangements which occur in severe asthma (Houston et al., 1953). In some patients radiological over-inflation and bronchial wall thicken- ing persisted despite clinical and physiological improvement. These abnormalities are probably related to the residual venti latory defects that have been demonstrated in asthmatics in remission (Palmer and Kelman, 1975).

Satisfactory radiographs can be obtained in very breathless patients using short exposure techniques with modern mobile X-ray units. The radiographs will be obtained at or near full inspiration because asthmatic patients tend to breathe at high lung volumes during exacerbations (Pride, 1977). Antero- posterior chest radiographs of patients in bed would, if anything, underest imate the degree of over- inflation using the criteria we have employed.

REFERENCES

Eggleston, P. A., Ward, B. H., Pierson, W. E. & Bierman, C. W. (1974). Radiographic abnormalities in acute asthma in children. Paediatrics, 54, 442- 449.

Houston, J. C., DeNavasquez, S. & Trounce, J. R. (1953). A clinical and pathological study of fatal cases of status asthmaticus. Thorax. 8, 207-213.

Palmer, K. N. V. & Kelman, G. R. (1975). Pulmonary func- tion in asthmatic patients in remission. British Medical Journal, 1,485-486.

Pride, N. B. (1977). Asthma, ed. Clark, T. J. H. & Godfrey, S., pp. 11-55. Chapman and Hall, London.

Simon, G., Reid, L., Tanner, J. M. Goldstein, H. & Benjamin, B. (1972). Growth of radiologically determined heart diameter, lung width and lung length from 5-19 years with standards for clinical use. Archives o f Disease in Childhood, 47, 373-381,

Simon, G., Connolly, N., Littlejohns, D. W. & McAllen, M. (1973). Radiologieal abnormalities in children with asthma and their relation to the clinical findings and some respiratory function tests. Thorax, 28, 115-123.