Study objective: There is considerable uncertainty about the clinical
features, respiratory physiology, and optimal management of patients w
ith asthma requiring mechanical ventilation. Furthermore, the ventilat
ory and pharmacologic management of asthma requiring mechanical ventil
ation remain controversial. We hypothesized (1) that there are clinica
lly identifiable and pathophysiologically different subgroups presenti
ng with asthma requiring ventilation; (2) that lower dose steroid ther
apy (< 400 mg/d intravenous hydrocortisone) is adequate; (3) that perm
issive hypercapnia is safe; (4) that prolonged paralysis is generally
unnecessary; and (5) that clinical outcome would be favorable in patie
nts treated with this approach. Design: Review of medical records and
intensive care charts and statistical analysis of findings. Setting: I
CU of tertiary institution. Patients: Thirty-five consecutive cases of
life-threatening asthma requiring mechanic ventilation. Results: Thre
e clinical subgroups of ventilation-requiring asthmatics could be iden
tified. Those presenting with steady deterioration (10), those with un
stable asthma followed by a sudden ''dip'' (16), and those with a sudd
en unexpected dip (9). Patients in the first group had a significantly
lower PaCO2 (p<0.01) at presentation, but required ventilation for lo
nger periods. Those in the second group had a significantly higher PaC
O2 (p < 0.01) and required ventilation for a shorter period. Those in
the third group had an intermediate PaCO2 level before intubation and
the shortest period (p < 0.01) of mechanical ventilation. Five patient
s experienced their sudden dip after ingesting aspirin. Ten cases rece
ived ''high'' dose hydrocortisone therapy (mean: 980 mg/24 h), and 25
received lower dose hydrocortisone (mean: 341 mg/24 h). No differences
in illness severity at presentation or outome could be detected betwe
en these two groups. Mean duration of ventilatory support was 36 h and
mean duration of the ICU stay 52.1 h. Muscle relaxation was used in 1
2 patients for a mean period of 11.1 h. One patient was brain dead on
arrival. All others survived. Conclusions: Life threatening asthma is
an endpoint for several different clinical patterns of disease. No maj
or clinical advantage could be found in our group of patients when hig
h-dose steroids were used. Longterm use of muscle relaxants and prolon
ged mechanic ventilation are rarely needed in the management of patien
ts with life-threatening asthma and excellent results can be achieved
with a relatively simple management strategy.