To determine the incidence of pulmonary dysfunction in comatose patients with severe traumatic brain injury and to evaluate the effect of respiratory failure on neurological outcome.

A retrospective study of 68 trauma patients, 18 females (26.47%) and 50 males (73.53%), admitted to the ICU from July 1998 to July 2003 with isolated brain injury and a Glasgow Coma Score (GCS) of 9 or less, all under sedation and mechanical ventilation on admission. Patients enrolled in the study were aged from 16 to 83 years, with a mean age of 40.28 ± 20.73 years. Pulmonary function was evaluated at the latest by the fourth day of hospitalization, using the Lung Injury Score (LIS) with the following components: chest radiographic findings, PaO₂/FiO₂ and positive end expiratory pressure. A LIS of zero was defined as normal pulmonary function, a LIS of 0.1–2.5 as mild to moderate dysfunction, while a LIS of more than 2.5 as severe pulmonary dysfunction. The maximum LIS was taken in consideration for statistical analysis. The patients' brain computerised tomography (CT) scan on admission was graded using the Marshall CT scoring system. The Glasgow Outcome Scale (GOS) was used after a 30-day follow-up of the population, as good recovery (1), moderate disability (2), severe disability (3), vegetative state (4), death (5) – considering good outcome as (1) and (2) and bad outcome as (3), (4) and (5). The mean value ± SD was calculated for all data. The correlation of all variables was assessed and the outcome was evaluated.

The GCS on admission was 6.47 ± 1.89. The maximum LIS was recorded before the fourth day of hospitalization (3 ± 1) with a mean value of 3.34 ± 0.86. Six patients (8.8%) had normal pulmonary function, while 59 (89.7%) had mild to moderate dysfunction and one patient (1.47%) had severe pulmonary dysfunction. Based on the GOS 47.1% (32/68) had good outcome and mortality reached 25% (17/68). Moderate statistical correlation was found between the LIS and GCS (correlation coefficient r = -0.51), and also between the LIS and GOS (r = 0.52), while the GCS and GOS were inversely related (r = -0.78). Sixty-one patients (89.7%) presented a relation between LIS and CT score (r = 0.64). The remaining nine patients (13.23%) did not show a relation between LIS and CT score, as aspiration prior to intubation, atelectasies and mechanical ventilation with overdistension of the lung aggravated pulmonary function directly and independently from the neurological status.

Although in clinical practice we experience a strong relation between LIS and CT scan findings for patients with severe traumatic brain injury, this was evident in 89.7% of the population studied. Pulmonary dysfunction was not an isolated complication in patients with brain injury showing poor prognosis, but rather represented the first manifestation of a systemic disease. A broader study should be performed in order to assert these findings.