Needs assessment can guide creation of a "resident-optimized clinic" in surgery.

BACKGROUND: There is limited data on deliberate teaching of residents in the clinic setting; we sought to investigate the clinic experience at our institution and improve education through creation of a novel "Resident-Optimized Clinic" (ROC). METHODS: An online survey was sent separately to residents and faculty. Based on the results of this survey a modified ROC was developed to try to improve the obstacles to learning in clinic. RESULTS: Qualitative analysis revealed the barriers in clinic were inconsistencies in expectations, lack of autonomy, time, and facility limitations. The modified ROC was rated positively with 100% of participants expressing they had sufficient time and autonomy; and 90% felt the environment was optimized for teaching. CONCLUSIONS: Multiple themes have been identified as problematic for the clinic education experience. The ROC was rated positively by trainees suggesting thoughtful intervention to improve clinic results in a better clinic experience and more educational gain from the clinic environment.

Refining the Definitions of Biochemical and Clinical Cure for Primary Aldosteronism Using the Primary Aldosteronism Surgical Outcome (PASO) Classification System.

INTRODUCTION: Determination of outcomes after adrenalectomy for primary aldosteronism (PA) is limited by the lack of standardized definitions of cure. The Primary Aldosteronism Surgical Outcomes (PASO) group recently established new consensus definitions for biochemical and clinical cure of PA. We hypothesize that utilization of PASO definitions will better stratify patient outcomes after surgery compared to original and current criteria utilized to document cure. MATERIALS AND METHODS: Patients undergoing adrenalectomy for PA from 1996 to 2016 were studied. Clinical data were reviewed. Three different sets of criteria (original, current, and PASO) were evaluated for differences in documentation of cure. Demographic data were reported as median (range). Comparisons were made using the Mann-Whitney U test; p < 0.05 is significant. RESULTS: A total of 314 patients with PA were identified. Ninety patients (60 males) elected to proceed with surgery. In Group 1 (35 patients), 30 patients had clinical follow-up and 29 (97%) were cured using original criteria. In Group 2 (55 patients), cure was recorded in 98% when original criteria for cure were applied, 89% cured applying current criteria, and 6% had complete biochemical and clinical cure by PASO criteria. Aldosterone rose 3.6 ng/dL (0.1-34.8) in five patients during extended follow-up, with two patients changing from complete to partial or missing biochemical success. CONCLUSION: Significant heterogeneity exists in outcomes criteria utilized to document cure or clinical improvement after adrenalectomy for primary aldosteronism. Aldosterone levels change over time after adrenalectomy. PASO definitions of cure appear to allow for improved stratification of short- and long-term outcomes.

Laparoscopic resection is inappropriate in patients with known or suspected adrenocortical carcinoma.

BACKGROUND: Complete surgical resection is the mainstay of treatment for patients with adrenocortical cancer (ACC). Use of laparoscopy has been questioned in patients with ACC. This study compares the outcomes of patients undergoing laparoscopic versus open resection (OR) for ACC. METHODS: A retrospective review (2003-2008) of patients with ACC was performed. Data were collected for demographics, operative and pathologic data, adjuvant therapy, and outcome. Chi-square analysis was performed. RESULTS: Eighty-eight patients (66% women; median age, 47 (range, 18-81) years) were identified. Seventeen patients underwent laparoscopic adrenalectomy (LA). Median tumor size of those who underwent LA was 7.0 (range, 4-14) cm versus 12.3 (range, 5-27) cm for OR. Recurrent disease in the laparoscopic group occurred in 63% versus 65% in the open group. Mean time to first recurrence for those who underwent LA was 9.6 months (+/-14) versus 19.2 months (+/-37.5) in the open group (p < 0.005). Fifty percent of patients who underwent LA had positive margins or notation of intraoperative tumor spill versus 18% of those who underwent OR (p = 0.01). Local recurrence occurred in 25% of the laparoscopic group versus 20% in the open group (p = 0.23). Mean follow-up was 36.5 months (+/-43.6). CONCLUSIONS: ACC continues to be a deadly disease, and little to no progress has been made from a treatment standpoint in the past 20 years. Careful and complete surgical resection is of the utmost importance. Although feasible in many cases and tempting, laparoscopic resection should not be attempted in patients with tumors suspicious for or known to be adrenocortical carcinoma.

The role of PET in the surgical approach to adrenal disease.

BACKGROUND: Appropriate surgical approach to diseases of the adrenal requires a diagnosis sufficient to determine the biochemical status of adrenal dysfunction and anatomic evaluation sufficient to differentiate unilateral from bilateral disease, intra-adrenal from extra-adrenal neoplasm, adrenal tumor recurrence or adrenal metastases. High resolution computed tomography (CT) and magnetic resonance have been the primary imaging modalities for the evaluation of anatomy, while scintigraphic studies have played a secondary role in diagnosis. The recent availability of functional imaging provided by positron emission tomography (PET) with radiopharmaceuticals designed to depict substrate precursor uptake, cellular metabolism or receptor binding in neoplasms and CT as a single modality, hybrid PET/CT, to directly correlate function and anatomy has had a significant impact upon the diagnostic and therapeutic approach to many cancers and has been applied to adrenal disease with some early success that we describe in this review. METHODS: In addition to the authors' experience, a search of Medline and PubMed databases was performed using search terms: 'adrenal scintigraphy', 'positron tomography', 'computed tomography', 'adrenal surgery', 'adrenal mass', '(18)F-fluorodeoxyglucose', 'adrenal carcinoma', 'adrenal medulla' and 'pheochromocytoma'. CONCLUSIONS: Present PET radiopharmaceuticals and their use in hybrid PET/CT have demonstrated efficacy in the preoperative and follow-up evaluation of neoplasms of the adrenal cortex and medulla that hopefully will continue to improve with the development of newer tracers that continue to exploit unusual characteristics of the adrenals.

Management of patients with adrenal cancer: recommendations of an international consensus conference.

Adrenocortical carcinomas are rare, highly malignant tumors that account for only 0.2% of deaths due to cancer. Given the limited number of patients seen in most medical centers with this diagnosis, series usually reported are small and clinical trials not randomized or blinded. In an attempt to answer important questions concerning the management of patients with adrenal cancer, a consensus conference was organized and held at the University of Michigan in Ann Arbor, MI, 11-13 September 2003, with the participation of an international group of physicians who had reported on the largest series of patients with this disease and who had recognized basic and clinical research expertise in adrenal cortical cancer. Totally 43 questions were addressed by the presenters and recommendations discussed in plenary and breakout sessions. Evidence for the recommendations of this conference was at the 2-4+ level and based on available literature and participants' experience. In addition to setting up guidelines in specific areas of the diagnosis and treatment of adrenal cancer, the conference recommended and initiated the planning of an international prospective trial for treatment of patients with adrenal cancer in stages III and IV. In terms of new therapies, first trials of dendritic cell therapy in human subjects with adrenal cancer have been started, but it is too early to comment on efficacy. Different strategies of immunotherapy, including DNA vaccination are currently being tried in animal models. There are no clinical gene therapy trials for human adrenal cortical cancer. The adrenals are a preferred target for adenovirus and the results of gene therapy in preclinical studies are promising. In addition, there is evidence that histone deacetylase inhibitors can further enhance the rate of adenoviral infectivity in human adrenal cancer cells. Testing of retroviral vectors, non-viral vectors, small interfering RNA technology, and combined approaches could be performed in various laboratories. Anti-angiogenic substances have only been applied in preclinical studies. The use of these and other agents in the treatment of adrenal cancer should be hypothesis-driven and based on a thorough analysis of tumor biology.

Role of endoscopic ultrasonography in screening and treatment of pancreatic endocrine tumours in asymptomatic patients with multiple endocrine neoplasia type 1.

BACKGROUND: Patients with multiple endocrine neoplasia (MEN) type 1 risk premature death from pancreatic endocrine tumours (PETs). Endoscopic ultrasonography (EUS) is the most sensitive imaging modality for small PETs. A screening and therapeutic approach for asymptomatic patients is delineated in which EUS plays a pivotal role. METHODS: This was a retrospective study of 15 patients with MEN-1 but with no symptoms of a PET. All patients underwent serum hormone measurement, including gastrin, and EUS. The findings were used to facilitate operative treatment. RESULTS: Six of 15 patients had a normal basal gastrin level and nine had a raised level. EUS demonstrated PETs in 14 patients and identified multiple lesions in 12. There was no predictive relationship between age or gastrin level and the number or size of PETs discovered. Thirteen patients have undergone enucleation or resection of PETs and two remain under observation. Nine of the 13 patients underwent transduodenal exploration to excise gastrinoma(s). One patient had lymph node metastases found at operation. There was no death. Self-limiting pancreatic fistula in five patients and biliary fistula in one. CONCLUSION: Early and aggressive screening using EUS identifies PETs in asymptomatic patients with MEN-1. Detection of tumours at an early stage, before the development of symptoms, lymph node metastases or liver metastases, may facilitate prompt surgical intervention and improve prognosis.

Inflammatory cytokine regulation of TRAIL-mediated apoptosis in thyroid epithelial cells.

Death receptor-mediated apoptosis has been implicated in target organ destruction in chronic autoimmune thyroiditis. Depending on the circumstances, inflammatory cytokines such as IL-1, TNF and IFNgamma have been shown to contribute to either the induction, progression or inhibition of this disease. Here we demonstrate that the death ligand TRAIL can induce apoptosis in primary, normal, thyroid epithelial cells under physiologically relevant conditions, specifically, treatment with the combination of inflammatory cytokines IL-1beta and TNFalpha. In contrast, IFNgamma is capable of blocking TRAIL-induced apoptosis in these cells. This regulation of TRAIL-mediated apoptosis by inflammatory cytokines appears to be due to alterations of cell surface expression of TRAIL receptor DR5 and not DR4. We also show the in vivo presence of TRAIL and TRAIL receptors DR5 and DcR1 in both normal and inflamed thyroids. Our data suggests TRAIL-mediated apoptosis may contribute to target organ destruction in chronic autoimmune thyroiditis.

Intraoperative parathyroid hormone monitoring fails to detect double parathyroid adenomas: a 2-institution experience.

BACKGROUND: We hypothesized that intraoperative parathyroid hormone monitoring (IOPTH) reliably would detect double parathyroid adenomas. METHODS: This was a retrospective study of 20 patients undergoing conventional parathyroidectomy with resection of exactly 2 abnormal glands. Full exploration was performed regardless of IOPTH values, which were measured after anesthetic induction and 5 and 10 minutes following removal of the first abnormal parathyroid gland. Failure to fall below 50% of baseline value by 10 minutes following resection of the first gland indicated the presence of multiglandular disease. RESULTS: All patients were cured. All excised glands were hypercellular on histology. Mean IOPTH values in 9 of the 20 patients with true negative results (noncurative decrease, another gland present) were 66% +/- 7% at 5 minutes and 83% +/- 15% at 10 minutes. The IOPTH values in 11 of the 20 patients with false positive results (curative decrease, another gland present) were 28% +/- 4% at 5 minutes and 18% +/- 2% at 10 minutes. The false positive rate of IOPTH was 55%. CONCLUSIONS: We found that IOPTH failed to reliably detect the presence of double parathyroid adenomas. These data suggest that caution should be exercised when terminating limited parathyroid exploration based on a curative fall in IOPTH values.

Endocrine tumours of the pancreas: review and recent advances.

Pancreatic endocrine tumours (PET) are rare but nonetheless important to recognize and treat in a timely fashion. Significant morbidity occurs due to excess secretion of hormones, with all of the PET having some degree of malignant potential. Surgeons must plan directed operative strategies to deal with these tumours and be prepared to undertake aggressive palliative debulking resections if indicated. Somatostatin receptor scintigraphy and endoscopic ultrasound have been particularly helpful in both localizing and staging patients with PET. Other important advances in management include the use of long-acting somatostatin analogues to inhibit hormonal secretion and tumour growth. The possibility of multiple endocrine neoplasia type 1 (MEN-1) should be considered in any patient with a PET. The present article will review the various classes of PET, describe MEN-1 in relation to PET and examine advances in imaging and localization. The role of surgery for PET is also discussed in the present review.

Early surgical intervention and strategy in patients with multiple endocrine neoplasia type 1.

Patients with multiple endocrine neoplasia type 1 (MEN-1) are an unusual challenge to the endocrine surgeon. Pituitary disease is often treated without surgery, but nearly all patients will require parathyroidectomy for parathyroid hyperplasia. Subtotal parathyroidectomy can be accomplished with a very low rate of permanent hypoparathyroidism and an acceptable rate of recurrent hyperparathyroidism. The treatment of pancreaticoduodenal disease is quite controversial. Even when associated with the Zollinger-Ellison syndrome, early and aggressive surgical treatment should be considered to influence the hormonal syndrome as well as to address the malignant potential of both pancreatic and duodenal tumours. This includes distal pancreatectomy, enucleation of pancreatic head lesions, and duodenotomy with the resection of gastrinomas. Many patients may be completely cured of the manifestations of their disease. As MEN-1 is an uncommon entity, there are very few prospective, randomized data upon which to base surgical judgements.

Incidence and importance of the tubercle of Zuckerkandl in thyroid surgery.

OBJECTIVE: To define the incidence of a distinct tubercle of Zuckerkandl (TZ) and confirm its anatomical relationships with the recurrent laryngeal nerve and the superior parathyroid gland. DESIGN: Two prospective series. SETTING: University teaching hospital, Australia. SUBJECTS: 200 patients who required thyroidectomy. INTERVENTIONS: Anatomical and clinical observations in two series of patients (n = 100 in each). The first defined the incidence of a TZ and preoperative symptoms; the second delineated the relationship of the TZ to the recurrent laryngeal nerve and the superior parathyroid gland. MAIN OUTCOME MEASURES: Anatomical relationships. RESULTS: A TZ was identified in 63% of patients and was > 1 cm in 45%. In 93% of patients with an enlarged TZ, the recurrent laryngeal nerve lay medial to it and the nerve was found lateral to the TZ in 7% of cases. The superior parathyroid gland was usually cranial to the TZ and posterior to the recurrent laryngeal nerve. The size and position of the TZ did not correlate clearly with symptoms. CONCLUSIONS: The TZ is a distinct feature of the thyroid gland that can be recognised during most thyroidectomies. The size and the position of the TZ have no constant relationship to preoperative symptoms. An understanding of the consistent anatomical relationship between the TZ and recurrent laryngeal nerve and superior parathyroid gland is crucial for safe thyroidectomy.

Routine parathyroid autotransplantation during total thyroidectomy: the influence of technique.

OBJECTIVE: To find out whether injecting a suspension of finely minced parathyroid tissue into the muscle bed had any adverse outcomes as it is simpler and potentially safer than implanting parathyroid tissue into muscle pockets. DESIGN: Prospective, randomised, controlled clinical trial. SETTING: University hospital, Australia. PATIENTS: 50 patients who were to have total thyroidectomy and routine parathyroid autotransplantation. INTERVENTIONS: Patients were randomised to either the injection technique or the implantation technique. MAIN OUTCOME MEASURES: Clinical assessment; corrected serum calcium and intact parathyroid hormone concentrations (PTH) measured immediately before, and at 1 day, 2 weeks, and 3 months after operation. RESULTS: Calcium was reduced significantly in both groups immediately after thyroidectomy. Although mean PTH concentrations decreased immediately after thyroidectomy and parathyroid autotransplantation in both groups, these changes were significant only in the implantation group. By 2 weeks and again by 3 months, calcium and intact parathyroid hormone concentrations had returned to baseline in both groups. At 3 months, 2 patients in each group still required some form of calcium supplement. At 6 months, no patients in the injection group required supplement. CONCLUSIONS: Injection of a suspension of parathyroid tissue is a simple, safe, and rapid technique for parathyroid autotransplantation during total thyroidectomy and is not associated with any more adverse outcome than is the standard technique.

Surgeon's approach to the thyroid gland: surgical anatomy and the importance of technique.

The cornerstone of safe and effective thyroid surgery is thorough training in and understanding of thyroid anatomy and pathology. With appropriate techniques, total thyroid lobectomy and total thyroidectomy (which should be considered simply as a bilateral total thyroid lobectomy performed during the same operation) can be undertaken with minimal risk of damage to the recurrent laryngeal nerves, the external branches of the superior laryngeal nerves, and the parathyroid glands. Safe surgery requires a specific operative plan, progressing in a series of logical, orderly, anatomically based steps. Exposure of the thyroid gland is followed by careful dissection of the superior pole, utilizing the avascular plane between the superior pole and the cricothyroid muscle to identify and preserve the external branch of the superior laryngeal nerve. Medial retraction of the gland then allows dissection of the lateral aspect of the thyroid lobe. Protection of the recurrent laryngeal nerves and preservation of the blood supply to the parathyroid glands is best achieved by "capsular dissection," ligating the tertiary branches of the inferior thyroid artery on the gland surface. If a parathyroid gland cannot be preserved or becomes ischemic after dissection of its vascular pedicle, it should be immediately minced and autotransplanted into the ipsilateral sternocleidomastoid muscle. The current evolution of outpatient or short-stay thyroidectomy emphasizes the need to avoid complications by utilizing meticulous surgical technique. Minimally invasive thyroidectomy utilizing endoscopic techniques may also affect the practice of thyroid surgery. Even so, understanding the surgical anatomy of the thyroid gland and its possible variations is paramount to safe and effective surgery.

Endoscopically assisted, minimally invasive parathyroidectomy.

BACKGROUND: Despite the success of open parathyroid exploration, minimally invasive alternatives have been emerging. This study reports an experience with endoscopically assisted, minimally invasive parathyroidectomy and evaluates its current role in patients undergoing surgery for hyperparathyroidism. METHODS: One hundred consecutive patients requiring surgery for hyperparathyroidism were evaluated. Endoscopic parathyroidectomy was offered based on the absence of coexisting nodular thyroid disease, previous neck surgery or irradiation, suspicion of parathyroid hyperplasia, or other anatomical or medical contraindications. Some 24 of 100 patients fulfilled the criteria and underwent endoscopic parathyroidectomy. Unequivocal localization to a single site by a technetium-99m-radiolabelled sestamibi scan allowed removal of the adenoma through a 25-mm suprasternal incision while being guided by a surgical telescope. RESULTS: There were no statistically significant differences in operating time or the mean size of resected adenomas between patients undergoing endoscopic and open parathyroidectomy. Four patients required conversion to an open procedure. Two patients developed temporary recurrent laryngeal nerve paresis and one had persistent hyperparathyroidism. CONCLUSION: Although endoscopic parathyroidectomy is technically feasible, its applicability is limited to a minority of patients undergoing operation for hyperparathyroidism. The potential for higher complication and failure rates makes optimism for the procedure appropriately guarded.

The spectrum of emergency admissions for thyroidectomy.

Emergency physicians frequently encounter patients with thyroid disease. However, it is unusual for these thyroid disorders to create acute, life-threatening situations. Critical airway compression attributable to benign or malignant thyroid enlargement may occur suddenly. Similarly, venous obstruction from thyroid tumors or severe physiological compromise from thyrotoxicosis may require urgent treatment. We reviewed a group of patients who were evaluated by emergency physicians for acute thyroid pathology and subsequently admitted for urgent thyroidectomy. Over a 7-year period, 13 patients had acute airway compressive symptoms, and 1 had acute venous compressive symptoms. Six patients had thyrotoxicosis with physiological compromise. Common airway management techniques were successfully used. Nineteen patients underwent thyroidectomy. One patient suffered a cardiopulmonary arrest before thyroidectomy could be performed. Surgical morbidity may be increased for patients undergoing thyroidectomy for urgent indications.

Intraoperative decision making in follicular lesions of the thyroid: is tumor size important?

BACKGROUND: Intraoperative decision making in treating follicular lesions of the thyroid remains controversial because there are no reliable preoperative or intraoperative factors predictive of malignancy. This study was undertaken to determine whether lesion size is a reliable factor that can be used to predict a final pathologic diagnosis of follicular carcinoma. STUDY DESIGN: This was a retrospective, case-matched control study. One hundred consecutive patients with follicular carcinoma were matched by gender, age, and date of operation with 100 patients with follicular adenomas. Seventy-nine matched pairs had pure follicular lesions and 21 matched pairs had oxyphilic variants of follicular lesions. After confirming adequate matching, lesion size was compared between groups. RESULTS: Regardless of whether all follicular lesions were analyzed or whether only pure follicular or oxyphilic variant lesions were compared, there was no significant difference in lesion size between the carcinoma and adenoma groups. The mean size of all follicular carcinomas was 31.5 +/- 1.7 mm and the mean size of all follicular adenomas was 30.8 +/- 1.5 mm (p = NS). When the proportions of the carcinoma and adenoma groups were indexed by five different size intervals and compared, there was again no significant difference in any category. CONCLUSIONS: On the basis of this case-matched control study, the size of a follicular lesion cannot be used to predict a final diagnosis of follicular carcinoma and is of no value when making intraoperative decisions about the extent of thyroid resection.

Partial liquid ventilation improves gas exchange and increases EELV in acute lung injury.

Gas exchange is improved during partial liquid ventilation with perfluorocarbon in animal models of acute lung injury. The specific mechanisms are unproved. We measured end-expiratory lung volume (EELV) by null-point body plethysmography in anesthetized sheep. Measurements of gas exchange and EELV were made before and after acute lung injury was induced with intravenous oleic acid to decrease EELV and worsen gas exchange. Measurements of gas exchange and EELV were again performed after partial liquid ventilation with 30 ml/kg of perfluorocarbon and compared with gas-ventilated controls. Oxygenation was significantly improved during partial liquid ventilation, and EELV (composite of gas and liquid) was significantly increased, compared with preliquid ventilation values and gas-ventilated controls. We conclude that partial liquid ventilation may directly recruit consolidated alveoli in the lung-injured sheep and that this may be one mechanism whereby gas exchange is improved.

Distribution of pulmonary blood flow and total lung water during partial liquid ventilation in acute lung injury.

BACKGROUND: Gas exchange is improved during partial liquid ventilation (PLV) with perfluorocarbon in animal models of acute lung injury. The mechanisms are not fully defined. We hypothesize that redistribution of pulmonary blood flow (PBF) along with redistribution of, and decrease in, total lung water (TLW) during PLV may improve oxygenation. METHODS: We characterized PBF and TLW in anesthetized adult dogs by using positron emission tomography with H2(15)O. Measurements of gas exchange, PBF, and TLW were made before and after acute lung injury was induced with intravenous oleic acid. The same measurements were made during PLV (with 30 ml/kg perfluorocarbon) and compared with gas ventilated (GV) controls. RESULTS: Oxygenation was significantly improved during PLV. PBF redistributed from the dependent zone of the lung to the nondependent zones, thus potentially improving ventilation/perfusion relationships. However, a similar pattern of PBF redistribution was observed during GV such that there was no significant difference between groups. TLW redistributed in a similar pattern during PLV. By quantitative measurements, PLV ameliorated the continued accumulation of TLW compared with GV animals. CONCLUSIONS: We conclude that PBF and TLW redistribution and attenuation of increases in TLW may contribute to the improvement in gas exchange during PLV in the setting of acute lung injury.

Partial liquid ventilation in a child on extracorporeal life support.

A 14 month old child was referred for management of acute respiratory distress syndrome after aspiration of paraffin lamp oil. Initial management with conventional ventilation and subsequent management with high frequency oscillatory ventilation produced pulmonary air leaks, further compromising clinical management. After initiating extracorporeal life support and low pressure ventilation, pulmonary air leaks subsided. The patient was then successfully managed by a protocol including partial liquid ventilation with perfluorocarbon. This case report details the authors' experience with the first child with respiratory failure to be managed with partial liquid ventilation while on extracorporeal life support.

Measuring functional residual capacity in normal and oleic acid-injured lungs.

Functional residual capacity (FRC) is an important oxygen reserve that is often depleted in acute respiratory failure. Recent interest in the mechanisms of liquid ventilation and limited experience in measuring FRC in paralyzed, mechanically ventilated, normal and lung-injured animal models have mandated development of accurate laboratory techniques. Eight sheep, from 17 to 27 kg, were anesthetized and instrumented to provide a tracheostomy, a pulmonary artery catheter, and carotid arterial line. They were randomized to two groups, one of which received 0.07 ml/kg of intravenous oleic acid to induce lung injury. Gas ventilation of both groups was identical except for respiratory rate, which was adjusted to normalize PaCO2. FRC was measured in duplicate by both helium dilution (HD) and body plethysmography (BP). When measurements were completed, the animals were euthanized and their endotracheal tubes clamped at end expiration. The lungs were then removed and their water displacement (WD) FRC values were measured. FRC was the difference between WD and tissue weight assuming 1 ml = 1g. Pearson's correlation coefficient (R(2)) was calculated. During in vitro measurement of test lungs, HD had an R(2) value of 0.99 and BP had an R(2) value of 0.98. When compared to WD, in vivo measurement of FRC by HD had an R(2) value of 0.94 while the value for BP was 0.97. In conclusion, both HD and BP are accurate methods of determining FRC in an uninjured and injured lung model when compared to postmortem WD. Documenting changes in FRC will aid in elucidating the mechanisms of alternative ventilatory techniques.