Determination of inhalation injury
Respiratory tract injury caused by smoke inhalation is the most common early cause of death in thermal injury. Inhalation injury is most commonly assessed on the basis of clinical data, blood gas analysis, and bronchoscopy. Cardiopulmonary responses in the immediate post-injury phase of smoke inhalation have not been well delineated. A study of the responses to inhalation injury was undertaken to determine whether selected cardiopulmonary parameters including spirometry, flow-volume loops, single-breath nitrogen analysis, lung volumes, cardiac output, and blood gas analysis were of diagnostic, prognostic, or therapeutic significance in the nursing assessment of inhalation injury. These parameters were evaluated in an attempt to: (1) identify a simple pulmonary function measurement which could be used in the bedside nursing assessment of inhalation injury, (2) to determine the site of injury associated with smoke inhalation, (3) to ascertain if inter-relationships exist among the parameters studied, and (4) to evaluate the accuracy of present methods used in assessing inhalation injury. Five male patients with a mean surface area burn of 4.3 percent meeting criteria for inhalation injury were compared to a control group of five male patients with a mean surface area burn of 33 percent without physical or historical evidence of inhalation injury. Patients were studied at mean time intervals of 10 hours, 20 hours, 31 hours, 54 hours, 11 days and 31 days after injury. When compared with the control group, the inhalation group was found to have clinically and statistically significant differences in FVC, FEV₀.₅, FEV₁.₀, FEV₂₅.₇₅, flow rates at low lung volumes, CV, CC, AP, OAC, and RV. Flow-volume loops before and after helium inhalation and the single-breath nitrogen analysis demonstrated that the observed differences were caused by obstruction in small airways. These functions improved but remained abnormal one month after injury. Clinical criteria including closed space injury, noxious fumes, carbonaceous sputum, and elevation of carboxyhemoglobin level were the most useful clinical parameters in defining inhalation injury. Fluid resuscitation in the burn or control group caused clinically insignificant small airways obstruction. It is concluded that measurement of both simple and sophisticated pulmonary functions is a sensitive and accurate method of assessing inhalation injury. Further it is recommended that simple spirometry should be used in the bedside nursing assessment of patients with clinical criteria of inhalation injury. The parameters of pulmonary function assessed by this measurement correlated significantly with all of the more difficult and sophisticated tests and thus have been validated as a test of inhalation injury.