in Flail Chest Control of Respiratory Therapy Frank Lewis, Jr., M.D., Arthur N. Thomas, M.D., and Richard M. Schlobohm, M.D.

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1 Control of Respiratory Therapy in Flail Chest Frank Lewis, Jr., M.D., Arthur N. Thomas, M.D., and Richard M. Schlobohm, M.D. ABSTRACT Pulmonary mechanics and oxygenation were measured in 24 consecutive patients with posttraumatic flail chest requiring continuous mechanical ventilation. The mean duration of mechanical ventilation was fourteen days. Mortality was 38% for all patients, 29% if deaths from head injury are excluded. Pneumonia occurred in 4 patients (17%) and pneumothorax in 1 (4%). Vital capacity and maximal inspiratory force measurements were useful in assessing chest wall stabilization. Total lung compliance correlated negatively with fatal outcome from respiratory failure. The alveolararterial oxygen gradient was not useful in assessing chest wall stabilization. C ontinuous mechanical ventilation (CMV) for the treatment of flail chest has become common since Avery and associates [2] described it in Continuous mechanical ventilation is defined as positivepressure ventilation through a tracheostomy or endotracheal tube, using a volumecycled ventilator with or without endexpiratory pressure. Mortality is still 2 to 7%, depending on the extent and severity of associated injuries, particularly pulmonary and myocardial contusion, head injury, abdominal injury, and skeletal fractures [ 1,3,57,9]. In patients with severe respiratory impairment, CMV provides internal stabilization for the fracture sites, which facilitates healing and provides adequate ventilatory volumes for gas exchange. In the contused lung it may also minimize interstitial edema, hemorrhage, and atelectasis [8]. Patients with flail chest require CMV for different durations depending upon the type and extent of injury. The number and location of rib fractures, associated injuries, age, and body habitus affect treatment requirements. This paper discusses guidelines for determining the optimal time to discontinue CMV in patients with flail chest. No objective data are available for assessing chest wall stabilization. Subjective clinical evaluations alone often prove inadequate. We will discuss the usefulness of four objective indicators of respiratory function in the assessment of chest wall stabilization in patients with flail chest. These are: vital capacity, maximal inspiratory force, alveolararterial oxygen tension difference, and static lung compliance. From the Departments of Surgery and Anesthesiology, University of California at San Francisco General Hospital, San Francisco, Calif. Supported in part by National Institutes of Health Grant no Presented at the Eleventh Annual Meeting of The Society of Thoracic Surgeons, Montreal, Que., Canada, Jan. 222, Address reprint requests to Dr. Lewis, Department of Surgery, 13 Solarium, San Francisco General Hospital, 11 Potrero Ave., San Francisco, Calif THE ANNALS OF THORACIC SURGERY

2 Respiratory Therapr in Flail Chest Clinical Material Twentyfour consecutive patients with severe flail chest admitted to San Francisco General Hospital between January, 1972, andjune, 1974, were studied retrospectively. All had paradoxical movement of the chest wall and severe respiratory distress requiring tracheal intubation and CMV. Injury in 2 1 patients resulted from motor vehicle accidents. The mean age of the patients was 54 years, with a range from 27 to 84. Mean hospital stay was twentyfive days. Associated injuries in these patients included other fractures in 19, pneumothorax in 9, pulmonary contusion in 12, ruptured spleen in 7, and liver laceration in 3. Only 3 patients had no other injury. Pulmonary contusion was judged to be present if an infiltrate was seen on the initial chest roentgenogram prior to fluid resuscitation and remained after adequate ventilation was established. The average number of rib fractures was six in survivors and eleven among patients who died. The presence of shock on admission to the hospital was noted in 2% of patients who survived and 44% of those who died. Average blood replacement in survivors was 2. liters, and in those who died, 4.3 liters. Electrocardiographic abnormalities consistent with myocardial contusion were present in 14 patients. Methods VENTILATORY MANAGEMENT Controlled CMV using a volume ventilator* was maintained in all patients until death or until chest wall stabilization was evident and vital capacity exceeded 1 ml per kilogram of body weight. Weaning patients from controlled CMV consisted of brief periods of spontaneous ventilation alternating with mechanical ventilation. Criteria to determine inadequacy of a patient s spontaneous ventilation were a respiratory rate greater than 4 per minute, arterial PCO~ greater than 45 torr, or respiratory distress. Patients who did not tolerate short periods of spontaneous ventilation were returned to CMV and retested periodically. If patients appeared to do well for 3 minutes or more, progressively longer periods of spontaneous ventilation were provided, and when mechanical ventilation was no longer necessary they were extubated. Mechanical ventilation was utilized for an average of fourteen days in all 24 patients. Nineteen patients were maintained on an endotracheal tube for the entire period of CMV, and 5 patients required tracheostomy. Indications for tracheostomy were mechanical ventilation longer than three weeks duration, facial injury with compromise of the upper airway, or the patient s intolerance of the endotracheal tube. Intubation was accomplished with a soft cuffed, controlledpressure endotracheal tube (Lanz). The nasotracheal route was preferred and was well tolerated for extended periods by the majority of patients. *Ohio 56, Bennett MA1, or Searle ventilator. VOL. 2, NO. 2, AUGUST,

3 LEWIS, THOMAS, AND SCHLOBOHM PULMONARY FUNCTION MEASUREMENTS The four pulmonary function measurements evaluated were vital capacity (VC), maximal inspiratory force (MIF), alveolararterial oxygen gradient (AaDo,), and total static lung compliance (Cts). These were measured on a regular basis during mechanical ventilation, daily for the AaDOz and every one to three days for the remainder, based on clinical progress. Vital capacity was determined with the patient in a sitting or semirecumbent position usinga Wright or Draeger spirometer. In the patient unable to cooperate, the PCO~ was allowed to rise until spontaneous breathing occurred. Tidal volume was then measured after a 15second period of airway occlusion and was considered equivalent to vital capacity. MIF is the maximum negative airway pressure achievable during brief occlusion of the endotracheal tube following normal expiration. Verbal encouragement of the patient during determination of VC and MIF is essential in order to obtain the maximal effort. In patients unable to cooperate, the same technique is used to obtain MIF as for VC. Arterial blood gas determinations were made with the patient ventilated with 1% oxygen for 15 minutes or more, and the AaDO, was calculated by subtracting arterial PO,, arterial Pco,, and saturated water vapor pressure from inspired oxygen partial pressure. Static lung compliance was calculated by dividing the expired tidal volume by the difference between the static endinspiratory ( plateau ) pressure and the endexpiratory pressure. Results MORTALITY AND MORBIDITY Nine deaths occurred in the series, an incidence of 38%. Three patients died of severe, irreversible cerebral injury one, six, and seven days after admission, respectively. Ifthey are excluded, the mortality rate is 29%. Six patients died from pulmonary causes. Three of these 6 developed progressive bilateral pulmonary infiltrates, decreasing lung compliance, and a large righttoleft pulmonary shunt, features of the adult respiratory distress syndrome. One patient died from combined cardiac and pulmonary failure, 1 from aspiration pneumonia, and 1 from late massive pulmonary embolism. Pulmonary complications included pneumonia in 4 patients, pneumothorax occurring as a result of mechanical ventilation in 1 patient, and lung herniation in 1 patient. The incidence of pneumonia (17%) was lower in this series than in other reports of flail chest injuries [6,7,9]. Our criteria for the diagnosis of pneumonia are fever, the typical roentgenographic infiltrate, a single predominant organism on sputum smear, and confirmatory culture. Prophylactic antibiotics were not used. Nonpulmonary complications included acute renal failure requiring dialysis in 3 patients and gangrenous cholecystitis in 1 patient. Tracheoesophageal fistula and tracheal stenosis did not occur in the series despite the protracted periods of tracheal intubation. In view of previous experi 172 THE ANNALS OF THORACIC SURGERY

4 Respiratory Therapy in Flail Chest FIG. 1. Static lung compliance as a function of clinical outcome. lot Ll 1 I I ADMISSION MINIMUM FINAL 1 ICU COMPLlANCf COMPLIANCE ence [ 11, we believe the use of a controlledpressure soft cuff on the endotracheal tube is the single most important factor in preventing tracheoesophageal fistula. PULMONARY FUNCTION MEASUREMENTS Vital capacity was consistently low on admission to the hospital, with a mean value of 5? 3 cc per kilogram of body weight. It remained static or declined slightly for the next two to four days, then typically began a steady and progressive increase that paralleled clinical stabilization. In surviving patients the mean value of VC at extubation was 18 f 5 cc per kilogram, and none of the patients was successfully weaned with a VC less than 14 cc per kilogram. Maximal inspiratory force followed a similar pattern, but the relative change was not as great. Mean value on admission was 23 f 9 cm HzO, and mean value at extubation in surviving patients was 41 f 9 cm HzO. MIF appeared to be less consistent than VC on serial determinations, probably due to variability in patient cooperation. The alveolararterial oxygen gradient showed no consistent trends and was not of value in following the progress of chest stabilization. In patients who died from adult respiratory distress syndrome, the AaDo, increased progressively as pulmonary function deteriorated and was in excess of 5 torr in all patients in this group shortly before death. The mean value of AaDoz in surviving patients at the time of extubation was torr. Total lung compliance did not correlate with chest stabilization but did provide a prognostic index in 6 patients who died from pulmonary causes (Fig. 1). Nonsurviving patients had a compliance of 41 & 7 mvcm HzO on admission, which steadily deteriorated until the mean shortly before death was 19? 7 mvcm HzO. In surviving patients the value on admission was 47 f 9 mvcm HzO. This subsequently declined to a mean minimum value of 32? 6 mvcm HzO, then rose to 5? 6 mvcm HzO at the time of extubation. VOL. 2, NO. 2, AUGUST,

5 LEWIS, THOMAS, AND SCHLOBOHM Comment Vital capacity and maximal inspiratory force provided consistent and reliable indices of chest wall stabilization in this group of patients. When normalized to the patient's weight, VC was useful as a predictive index for weaning from the ventilator. Figure 2 shows typical time patterns of VC and MIF in 4 patients. The patient whose values are shown in Figure 2A was 62 years of age and had eight broken ribs with a unilateral flail segment. He was extubated on the eleventh hospital day with a VC of 15 mvkg and MIF of 43 cm H2. Figure 2B represents a 58yearold patient with five ribs fractured on the right and three on the left. He progressed slowly the first week, then rapidly stabilized and was extubated with a VC of 3 mllkg and MIF of 6 cm H2. Figure 2C shows the values for a 52yearold patient whose small left anterior flail was not noted on admission to the hospital. On the fifth hospital day she developed severe respiratory decompensation and 5 4 A MIF 3 2 VITAL CAPACITY loo B HOSPITAL DAYS FIG. 2. Vital caficity and maximal inspiratory force as a function of hospital days in (A) a 62yearold man with unilateraljai1 chest, (B) a 58yearold man with unilateral Jail chest and bilateral rib fractures. 174 THE ANNALS OF THORACIC SURGERY

6 Respiratory Therapy in Flail Chat was belatedly treated with mechanical ventilation. Subsequent progress was rapid, and she was extubated with a VC of 14 mvkg and MIF of 4 cm H2. The measurements shown in Figure 2D are from a 27yearold patient who had bilateral rib fractures involving twelve ribs and a sternal flail segment. CMV was initially stopped when the VC was 15 mvkg, but during the subsequent three days respiratory decompensation recurred and he required reintubation. At the time of reintubation his VC had declined to nearly its original value. The values of VC and MIF which we have found adequate for cessation of CMV in patients with flail chest are 5% greater than those utilized in patients mechanically ventilated for other reasons. The patient without flail who is treated with CMV can often be weaned when the VC approaches 15% of predicted normalvalues, or about 1 ml per kilogram ofbody weight. In flail chest, however, we found success at weaning from CMV when VC was greater than 25% of the predicted normal values, or about 18 ml per kilogram. Perhaps this is because chest wall stabilization is not yet complete at the time of weaning. C VITAL CAPACITY MIF 1 1 ' I ' I ' I " " ' I HOSPITAL DAYS e m 'Ijs/.'J, CAPACITY VITAL j 2 J P //.".J O MIF 2 1 VOL. 2, NO. 2, AUGUST,

7 LEWIS, THOMAS, AND SCHLOBOHM The AaDo2 was not of value in monitoring chest wall stabilization but did provide an index to the severity of underlying pulmonary parenchymal disease. Pulmonary compliance also reflected parenchymal disease, as has been noted by others [4], and in addition appeared to offer a prognostic index in these patients. Compliance decreased initially in all patients but then returned to normal in survivors, while a progressive decline continued in those who died. References 1. Ashbaugh, D. G., Peters, G. N., Halgrimson, C. G., Owens, J. C., and Waddell, W. R. Chest trauma: Analysis of 685 patients. Arch Surg 95:546, Avery, E. E., March, E. T., and Benson, D. W. Critically crushed chests: A new method of treatment with continuous mechanical hyperventilation to produce alkalotic apnea and internal pneumatic stabilization. J Thoruc Surg 32:291, Blaisdell, F. W., and Schlobohm, R. M. The respiratory distress syndrome: A review. Surgery 74:251, Fleming, W. H., Bowen, J. C., and Petty, C. The use of respiratory compliance as a guide to respiratory therapy. Surg Gynecol Obstet 134:291, Howell, J. F., Crawford, E. S., and Jordan, G. L. The flail chest: An analysis of 1 patients Am J Surg 16:628, Perry, J. F., and Galway, C. F. Factors influencing survival after flail chest injuries. Arch Surg 91:216, Relihan, M., and Litwin, M. S. Morbidity and mortality associated with flail chest injury: A review of 85 cases. J Trauma 13:663, Roscher, R., Bittner, R., and Stockmann, LJ. Pulmonary contusion: Clinical experience. Arch Surg 19:58, Sankaran, S., and Wilson, R. F. Factorsaffecting prognosisin patients with flailchest. J Thoruc Cardiovasc Surg 6:42, Thomas, A. N. The diagnosis and treatment of tracheoesophageal fistula caused by cuffed tracheal tubes. J Thorac Cardiovasc Surg 65:612, Discussion DR. THOMAS D. BARTLEY (Gainesville, Fla.): In patients requiring ventilatory support with flail chest, for the last two years we have been using what is called intermittent mandatory ventilation. This has worked so well that we have not felt right about doing a controlled or doubleblind study including all our patients. Intermittent mandatory ventilation certainly does make it easier to get these patients off the ventilator. One simply reduces the driven respirations progressively from 8 to 6 to 4 some machines can go down to 2 and then the patient is ready to go on the Ttube and finally have the tube removed altogether. DR. LEWIS: Thank you for your comments, Dr. Bartley. We would agree that intermittent mandatory ventilation or intermittent assisted ventilation is of value in selected patients in shortening the weaning time. Although we reviewed only 327 patientdays of positivepressure ventilation in this group of patients, we have a larger experience now of about 6, patientdays using the Lanz tube, and in that experience we have not seen any tracheoesophageal fistulas or late tracheal stenosis. We therefore believe it is of major benefit in preventing that complication. 176 THE ANNALS OF THORACIC SURGERY