Management of lung contusion.

One hundred and thirty-two consecutive patients with lung contusion were admitted during the three-year period of 1972 through 1974. All were treated with early intubation and mechanical ventilation with positive and-expiratory pressure with the postulate that such management would minimize the progression of interstitial edema, and intra-alveolar hemorrhage. If progressive increase in the alveolar/arterial oxygen tension gradient was not observed over the ensuing 24 hours, and in the absence of other non-thoracic indications of continuance of mechanical ventilation, patients were extubated and removed from the ventilator. All other patients were further ventilated and followed by daily chest roentgenograms and blood gas studies. Mean ventilation time was 6.2 days. Progressive hypoxemia and deterioration of pulmonary function were not seen. The incidence of pneumonia and tension pneumothorax was low. Overall mortality was 10.6 per cent. The most common cause of death was brain death. No deaths were the result of hypoxemia.

PEEP: its use in young patients with apparently normal lungs.

PEEP has been advocated for use in patients with the acute respiratory distress syndrome characterized by a marked reduction in FRC. It has not been advocated for patients with apparently normal lungs requiring prolonged mechanical ventilation. We have done inert gas washouts on five young patients comparing no PEEP to 10 cm H2O PEEP. Four of the five showed a significant improvement in PaO2, a decrease in AaDO2 and Qs/Qt, the fifth a slight improvement on PEEP. Arterial washouts were significantly faster on PEEP in all patients suggesting a decrease in intrapulmonary shunting. Airway washouts in the initial phase were faster off PEEP suggesting an increase in lung volume and FRC with PEEP. Later portions of the curve were faster on PEEP suggesting improved distribution of ventilation. These findings suggest that PEEP might be of significant value in treatment of patients requiring prolonged mechanical ventilation for reasons other than lung abnormalities.

Optimal flow pattern for mechanical ventilation of the lungs. 2. The effect of a sine versus square wave flow pattern with and without an end-inspiratory pause on patients.

In four series of patients, the efficiency of ventilation of a sine wave without an end-inspiratory pause was compared to a square wave without a pause, a sine wave with a pause to a square wave with a pause, a sine wave to a sine wave with a pause, and a sine wave with a long pause to one with a short pause. The primary mode of evaluation was through simultaneous airway and arterial argon washout curves. Additional cardiopulmonary measurements were made. Results indicate: (1) a statistically significant improvement in ventilation with a sine wave with a pause; (2) a statistically significant improvement with the longer pause as compared to the short pause.

Chest physiotherapy: the effect on arterial oxygenation.

A prospective study of 47 patients during mechanical ventilation with positive end-expiratory pressure was undertaken to evaluate changes in Pao2 following chest physiotherapy. In contrast to other studies, we found no significant change in Pao2 following chest physiotherapy (p greater than 0.05). Different technics for physiotherapy and ventilation may have accounted for the absence of hypoxemia reported by others. Possible reasons for failure to improve Pao2 were suggested. Chest X-ray before and within 24 hours of physiotherapy showed improvement in 68 percent of patients. Chest physiotherapy was most effective in the treatment of unilobar densities and produced dramatic improvement in atelectasis of acute onset.

Selection of the source of mixed venous blood samples in severely traumatized patients.

The technic of balloon flotation catheterization represents a significant advance in providing an additional aid to diagnosis, clinical assessment, and management of the critically ill. The fact that such patients are admitted to an intensive care unit (ICU) invariably presumes that their management will include close and accurate monitoring of the cardiovascular and respiratory systems. In a prospective study of 51 patients, not in clinical shock, in an ICU, the authors demonstrated that superior vena cava samples are not a reliable index of mixed venous blood saturation in the critically injured patient, and that a pulmonary arterial catheter is essential for obtaining true mixed venous samples for valid estimations of intrapulmonary shunts and arteriovenous O2 content differences.

Pitfalls of Swan-Ganz catheterization.

In 60 patients in whom Swan-Ganz catheters apparently had been positioned correctly, the balloon was visualized by inflation with radiopaque contrast medium. Sixteen were located peripherrally; in 15 of these 16, the balloon inflated eccentrically and in each of these instances, an accurate wedge pressure could not be obtained. One patient in this group had an episode of hemoptysis immediately prior to detection of the peripheral location and eccentric inflation of the balloon. The correct placement and safe use of the Swan-Ganz catheter demand that the catheter tip be located in a large pulmonary artery and that redundant loops of catheter be avoided to prevent subsequent peripheral migration. Identification of peripheral placement and eccentric inflation should be suspected if a pulmonary wedge pressure is obtained with a significantly smaller volume of air than the balloon capacity. The use of a continuous flush system will provide an additional alert by a steady rise in the pseudowedge pressure on attempted balloon inflation.

Optimal flow pattern for mechanical ventilation of the lungs. Evaluation with a model lung.

The major components entering into the inspiratory pattern of various respirators were tested on a model lung which had an abnormally high airway resistance on one side. The tests consisted of simultaneous nitrogen washout curves from each lung separately utilizing two mass spectrometers. The components tested included a constant versus accelerating wave form and the presence, duration or absence of an end-inspiratory pause. Respirators tested included the Bennett MA1. Engström 300 and the Elema Schonander Servo tventilator 900. The results demonstrated the importance of an end inspiratory pause in improving gas distribution and efficiency of washout. No difference was found between a constant or accelerating air flow. Preliminary results in man appear to confirm the importance of an end inspiratory pause.

Automated respiratory gas monitoring of critically injured patients.

Since 1971, we have used a mass spectrometer system for automatic hourly sampling of airway gases on a 24-hour basis in our 12 bed Critical Care Unit. Used in conjunction with arterial and mixed-venous blood samples, the availability of end-tidal O2 and CO2 values allows early identification of increasing AaDO2 and aADCO2 gradients. The ability to monitor end-tidal CO2 allows the monitoring of the adequacy of alveolar ventilation both in patients on and following removal from mechanical ventilation. Continuous information of the end-tidal PCO2 is of particular value in the management of patients with severe head injury.

Tracking respiratory therapy in the trauma patient.

The respiratory index (RI), P(AaDO2)/PaO2, was investigated in a retrospective study of 177 intubated patients treated at the Maryland Institute for Emergency Medicine. An RI of 0.1 to 0.37 is normal. Patients with an RI of 2 or greater were intubated. Those patients who reached an RI of 6 or more had an associated 12 per cent probability of survival. The RI reflects the presence of pulmonary shunting in a variety of circumstances including atelectasis, pulmonary contusion, and pulmonary emboli. A nomogram that allows the course of the patient with respiratory problems to be followed is described. Movement along the same isobars or between isobars can be followed by plotting the PaO2 against the FI0-2. Thus, the rationale and effect of respiratory therapeutic manipulations may be recorded graphically.