Bowel Preparation for Elective Hartmann Operation: Analysis of the National Surgical Quality Improvement Program Database.

Background: Use of pre-operative bowel preparation in colorectal resection has not been examined solely in patients who have had colorectal resection with primary colostomy (Hartmann procedure). We aimed to evaluate the association of bowel preparations with short-term outcomes after non-emergent Hartmann procedure. Patients and Methods: The National Surgical Quality Improvement Program Participant Use File colectomy database was queried for patients who had elective open or laparoscopic Hartmann operation. Patients were grouped by pre-operative bowel preparation: no bowel preparation, oral antibiotic agents, mechanical preparation, or both mechanical and oral antibiotic agent preparation (combined). Propensity analysis was performed, and outcomes were compared by type of pre-operative bowel preparation. The primary outcome was rate of any surgical site infection (SSI). Secondary outcomes included overall complication, re-operation, re-admission, Clostridioides difficile colitis, and length of stay. Results: Of the 4,331 records analyzed, 2,040 (47.1%) patients received no preparation, 251 (4.4%) received oral antibiotic preparation, 1,035 (23.9%) received mechanical bowel preparation, and 1,005 (23.2%) received combined oral antibiotic and mechanical bowel preparation. After propensity adjustment, rates of any SSI, overall complication, and length of hospital stay varied significantly between pre-operative bowel regimens (p < 0.005). The use of combined bowel preparation was associated with decreased rate of SSI, overall complication, and length of stay. No difference in rate of re-operation or post-operative Clostridioides difficile infection was observed based on bowel preparation. Conclusions: Compared with no pre-operative bowel preparation, any bowel preparation was associated with reduced rate of SSI, but not rate of re-operation or post-operative Clostridioides difficile infection.

Effect of preoperative versus postoperative use of transversus abdominis plane block with plain 0.25 % bupivacaine on postoperative opioid use: a retrospective study.

BACKGROUND: Enhanced recovery protocols optimize pain control via multimodal approaches that include transversus abdominis plane (TAP) block. The aim of this study was to evaluate the effect of preoperative vs. postoperative plain 0.25 % bupivacaine TAP block on postoperative opioid use after colorectal surgery. METHODS: A retrospective cohort study comparing postoperative opioid use in patients who received preoperative (n = 240) vs. postoperative (n = 22) plain 0.25 % bupivacaine TAP blocks. The study was conducted in a single tertiary care institution and included patients who underwent colorectal resections between August 2018 and January 2020. The primary outcome of the study was postoperative opioid use. Secondary outcomes included operative details, length of stay, reoperation, and readmission rates. RESULTS: Patients who received postoperative plain 0.25 % bupivacaine TAP blocks were less likely to require postoperative patient-controlled analgesia (PCA) (59.1 % vs. 83.3 %; p = 0.012) and opioid medications on discharge (6.4 % vs. 16.9 %; p = 0.004) relative to patients who received preoperative TAP. When needed, a significantly smaller amount of opioid was prescribed to the postoperative group (84.5 vs. 32.0 mg, p = 0.047). No significant differences were noted in the duration of postoperative PCA use, amount of oral opioid use, and length of stay. CONCLUSIONS: Plain 0.25 % bupivacaine TAP block administered postoperatively was associated with significantly lower need for postoperative PCA and discharge opioid medications. The overall hospital length of stay was not affected by the timing of TAP block. Because of the limited sample size in this study, conclusions cannot be generalized, and more research will be required.

Safety of Transrectal or Transvaginal Drainage of Pelvic Abscesses / Segurança da drenagem transretal ou transvaginal de abscessos pélvicos

Abstract Objective The literature on the safety and long-term sequelae of transrectal and transvaginal drainage of pelvic abscesses is limited. We evaluated the outcomes and safety of pelvic abscess drainage by interventional radiology at our institution. Methods After obtaining institutional review board approval, we retrospectively evaluated the outcomes of transrectal and transvaginal pelvic abscesses drainage using computed tomography, endorectal ultrasound, and or fluoroscopy. Results The study included 26 patients, with an age range of 24 to 88 years old, out of whom 53.8% were men. A total of 46.1% of the participants were African Americans and 26.9% were Caucasians. The average body mass index was 28.4 (range: 15.6 to 41.9). The most common etiology was penetrating abdominal injury (27%), followed by appendectomy (23%), diverticular disease (11.5%), anastomotic leak (11.5%), and disorders of gynecological causes (11.5%). The mean abscess diameter was 6.3 cm (range: 3.3 to 10.0 cm). Transrectal drainage was performed in all except one patient who had a transvaginal drainage. Transrectal ultrasound was used for drainage in 92.3% cases, and fluoroscopy was used as an additional imaging modality in 75% of the cases. An 8- or 10-Fr pigtail catheter was used in>80% of the patients. Drains were removed between 2 and 7 days in 92.3% of the cases. The average follow-up was 30.4 months (range: 1 to 107 months), and no long-term complications were reported. Only one patient required subsequent operative intervention for an anastomotic leak. Conclusions Pelvic abscess drainage by transrectal route using radiological guidance is a safe and effective procedure.

Resumo Objetivo A literatura sobre a segurança e as sequelas no longo prazo da drenagem transretal e transvaginal do abscesso pélvico é limitada. Avaliamos os resultados e a segurança da drenagem do abscesso pélvico por radiologia intervencionista em nossa instituição. Métodos Após obter a aprovação do conselho de revisão institucional, avaliamos retrospectivamente os resultados da drenagem de abscessos pélvicos transretais e transvaginais por meio de tomografia computadorizada, ultrassom endorretal, e/ou fluoroscopia. Resultados Participaram do estudo 26 pacientes, com faixa etária de 24 a 88 anos, dos quais 53,8% eram homens. Um total de 46,1% eram afro-descendentes, e 26,9% eram brancos. O índice de massa corporal médio foi de 28,4 (gama: 15,6 a 41,9). A etiologia mais comum foi lesão abdominal penetrante (27%), seguida de apendicectomia (23%), doença diverticular (11,5%), fístula anastomótica (11,5%) e distúrbios de causas ginecológicas (11,5%). O diâmetro médio do abscesso foi de 6,3 cm(gama: 3,3 a 10,0 cm). A drenagem transretal foi realizada em todos os pacientes, com exceção de uma, que foi submetida a uma drenagem transvaginal. A ultrassonografia transretal foi utilizada para drenagem em 92,3% dos casos, e a fluoroscopia como modalidade adicional de imagem, em 75% dos casos. Um catéter duplo J de 8 ou 10 Fr foi usado em>80% dos pacientes. Os drenos foram retirados entre 2 e 7 dias em 92,3% dos casos. O acompanhamentomédio foi de 30,4meses (gama: 1 a 107 meses), e nenhuma complicação de longo prazo foi relatada. Apenas um paciente necessitou de intervenção cirúrgica subsequente para um vazamento anastomótico. Conclusão A drenagem do abscesso pélvico por via transretal com orientação radiológica é um procedimento seguro e eficaz.

Extraperineal enterocele in male: A case report and literature review.

INTRODUCTION: Enterocele is a herniation of the small bowel through the cul-de-sac. It is uncommon and most often seen in elder females. Large enterocele manifesting as rectal prolapse is exceedingly rare and only few cases are reported previously. Due to it rarity, the best surgical treatment is not yet established especially in male patients. We present a case of enterocele causing rectal prolapse in a male patient that was treated surgically. PRESENTATION OF CASE: A 47-year-old African American male with chronic constipation and straining presented with manually reducible rectal prolapse. A defecography revealed a large enterocele prolapsing through the anterior rectal wall. The patient underwent an open posterior suture rectopexy with peritoneoplasty. His symptoms completely resolved after surgery, and repeat defecography three months after the procedure showed no sign of recurrence. DISCUSSION & CONCLUSION: Extraperineal enterocele in male is a rare disease. Rectopexy with peritoneoplasty can provide a great symptom relieve and improvement on defecography. Long-term outcome should be evaluated.

Surgical Wound Misclassification to Clean From Clean-Contaminated in Common Abdominal Operations.

BACKGROUND: Wound classification helps predict wound-related complications and is useful in stratifying surgical site infection reporting. We sought to evaluate misclassification among commonly performed surgeries that are at least clean-contaminated. MATERIALS AND METHODS: The National Surgical Quality Improvement Program database was queried from 2005 to 2016 by Current Procedural Terminology codes identifying common surgeries that are, by definition, not clean: colectomy, cholecystectomy, hysterectomy, and appendectomy. Univariate analysis and multivariate logistic regression were performed. RESULTS: Of the 1,208,544 operative cases reviewed, 22,925 (1.90%) were misclassified as clean. Hysterectomy was the most commonly misclassified operation (3.11%), and colectomy the least (0.82%). Misclassification was higher in laparoscopic cases (1.92% versus 1.82%; P < 0.01). Misclassification increased from 2005 to 2016 (0.22% versus 3.11%; P < 0.01). Misclassified patients were younger (46.7 versus 47.7 y; P < 0.01); had lower rates of hypertension, chronic obstructive pulmonary disease, smoking history, and steroid use (P < 0.01); and had shorter length of stay (2.2 versus 3.2 d; P < 0.01), lower 30-d readmission rates (3.7% versus 5.0%; P < 0.01), and less surgical site infections (1.7% versus 3.4%; P < 0.01). Open hysterectomy was the most significant positive predictor for misclassification (odds ratio 3.34; P < 0.01). Open appendectomy was the most significant negative predictor (odds ratio 0.20; P < 0.01). CONCLUSIONS: There is an increasing trend of misclassifying wounds as clean. Misclassified patients have better outcomes, and misclassification may be affected by patient characteristics, operative approach, and type of procedure rather than reflecting the true infectious burden. Further research is warranted.

Medical Management of Diverticular Disease.

This article reviews the current literature supporting the non-surgical options for treatment in acute uncomplicated diverticulitis, complicated diverticulitis, and options for prevention of recurrent diverticulitis.

The value proposition of simulation.

BACKGROUND: Simulation has been shown to improve trainee performance at the bedside and in the operating room. As the use of simulation-based training is expanded to address a host of health care challenges, its added value needs to be clearly demonstrated. Demonstrable improvements will support the expansion of infrastructure, staff, and programs within existing simulation facilities as well as the establishment of new facilities to meet growing needs and demands. Thus, organizational and institutional leaders, faculty members, and other stakeholders can be assured of the best use of existing resources and can be persuaded to make greater investments in simulation-based training for the future. METHODS: A multidisciplinary panel was convened during the 8th Annual Meeting of the Consortium of the American College of Surgeons-Accredited Education Institutes (Simulation Centers) in March 2015 to discuss the added value of simulation-based training. Panelists shared the ways in which the value of simulation was demonstrated at their institutions. CONCLUSION: The value of simulation-based training was considered and described in terms of educational impact, patient care outcomes, and costs.

Accuracy of national surgery quality improvement program models in predicting postoperative morbidity in patients undergoing colectomy.

BACKGROUND: The National Surgery Quality Improvement Program (NSQIP) is the standard for assessment of acuity-adjusted outcomes in surgery. The validity of NSQIP has not been well established in colorectal surgery. Technical and process variables, which NSQIP may not consider, affect morbidity rate. OBJECTIVE: A retrospective observational study was undertaken to determine the accuracy of NSQIP models in predicting morbidity for patients undergoing laparoscopic or open colectomy. METHODS: NSQIP participant use files for 2005 to 2008 were obtained. Data were selected using Current Procedural Terminology coding for open or laparoscopic colectomy. NSQIP-generated predicted morbidities were used to create area under the receiver operator curves (AUROCs). RESULTS: AUROCs demonstrated an accurate predictive model if the value was above 0.8 and indicated a marginal predictor mode if below 0.7. The AUROC for the general NSQIP model was 0.817 (confidence interval [CI] = 0.815-0.819, p < 0.001). AUROC for the combined laparoscopic and open colectomy group was 0.703 (CI = 0.698-0.709, p value < 0.001). AUROCs for the individual laparoscopic and open colectomy groups were 0.627 (CI = 0.615-0.640, p < 0.001) and 0.701 (CI = 0.695-0.707, p < 0.001). CONCLUSION: This study demonstrates that although NSQIP-generated morbidities used to create AUROCs are accurate for patients in an overall surgical model, predictive models for morbidity are marginal for laparoscopic and open abdominal colectomies. NSQIP risk models tend to emphasize comorbidities rather than intraoperative details or technical aspects of colonic resections.

Predictors of critical care-related complications in colectomy patients using the National Surgical Quality Improvement Program: exploring frailty and aggressive laparoscopic approaches.

BACKGROUND: Colectomy patients experience a broad set of adverse outcomes. Complications requiring critical care support are common in this group. We hypothesized that as frailty increases, the risk of Clavien class IV and V complications will increase in colectomy patients. METHODS: Using the National Surgical Quality Improvement Program (NSQIP) participant use files for 2005-2009, we identified patients who underwent laparoscopic and open colectomies by Current Procedural Terminology code. Using the Clavien classification for postoperative complications, we identified NSQIP data points most consistent with Clavien class IV requiring intensive care unit (ICU) care or class V complications (death). We used a modified frailty index with 11 variables based on mapping the Canadian Study of Health and Aging Frailty Index and existing NSQIP variables. Logistic regression was performed to acuity adjust the findings. RESULTS: A total of 58,448 colectomies were identified. As frailty index increased from 0 to 0.55, the proportion of those experiencing Clavien class IV or V complications increased from 3.2% at baseline to 56.3%. Variables found to be significant by logistic regression (odds ratio) were frailty index (14.4; p = 0.001), open procedure (2.35; p < 0.001), and American Society of Anesthesiologists class 4 (3.2; p = 0.038) or 5 (7.1; p = 0.001) while emergency operation and wound classification 3 or 4 were not. CONCLUSIONS: Complications requiring ICU care represent a significant morbidity in the colectomy patient population. Frailty index seems to be an important predictor of ICU-level complications and death, and laparoscopy seems to be protective.

Clostridium difficile of the ileum following total abdominal colectomy, with or without proctectomy: who is at risk?

BACKGROUND: Clostridium difficile enteritis is considered a rare entity, although recent data suggest a significant increase in prevalence and incidence. There is paucity of data evaluating risk factors of C difficile enteritis following total colectomy. OBJECTIVE: The aim of this study was to determine the incidence and risk factors of C difficile enteritis for patients who had undergone total abdominal colectomy with or without proctectomy. DESIGN: This study involves a retrospective chart review of 310 patients. Univariate analysis was performed on potential risk factors (p ≤ 0.05) with the use of a logistic regression model, and a Fisher exact test was used for variables that had no occurrences of C difficile. These groups of variables were then examined in a multiple variate setting with stepwise logistic regression analysis. SETTINGS: This study was conducted at a tertiary referral center. PATIENTS: A data analysis was performed on patients who had undergone total abdominal colectomy with or without proctectomy who were tested for C difficile of the ileum. RESULTS: Twenty-two of 137 patients that were tested (16%) were positive for C difficile of the ileum. Univariate analysis of known risk factors for C difficile demonstrated that black race was a protective factor against C difficile (p = 0.016). The multivariate analysis demonstrated that emergency surgery (p = 0.035), race (p = 0.003), and increasing age by decade (p = 0.033) were risk factors for C difficile. LIMITATIONS: This study was limited by the small patient sample, and it was not a randomized trial. CONCLUSIONS: Black race is protective, and whites are 4 times more likely to acquire C difficile of the ileum after undergoing a total abdominal colectomy with or without proctectomy. The data also demonstrated that an increased age by a decade and emergency surgery are risk factors for C difficile enteritis, whereas the described risk factors of C difficile of the colon and type of colon surgery do not appear to influence the risk of C difficile of the ileum.

Effect of the new standards for case logging on resident operative volume: doing better cases or better numbers?

OBJECTIVES: The Accreditation Council for Graduate Medical Education (ACGME) modified the designation of major (index) operative cases to include those previously considered "minor." This study assessed the potential effect of these changes on resident operative experience. METHODS: With Institutional Review Board approval, we analyzed National Surgical Quality Improvement Program participant use files for 2005-2008 for general and vascular surgery cases. Primary CPT case coding was mapped to the ACGME major case category using both the old and new classification schemes. The variables were analyzed using χ(2) analysis in SPSS IBM 19 (IBM, Armonk, New York). RESULTS: A total of 576,019 cases were reviewed. Major cases as defined by the new classification represented an increasing proportion of the cases each year, rising from 88.3% in 2005 to 95% by 2008 (p < 0.001). Major cases as defined by the old scheme decreased from 71% in 2005 to 62% by 2008 (p < 0.001). The cases covered by a resident dropped from 82% in 2005 to 61% in 2008 (p < 0.001). When comparing the new to the old scheme, 364,366 (63.3%) cases were considered major and 30,587 (5.3%) were minor by both standards; 7089 (1.2%) cases previously classified as major were changed to minor, whereas 173,977 (30.2%) (p < 0.001) previously classified as minor were now major. This latter group showed top procedures to include excision of breast lesion (22,175 [12.7%]), laparoscopic gastric bypass (18,825 [10.8%]), ventral hernia repair (14,732 [8.5%]), and appendectomy (10,190 [5.9%]). Of these newly designated major cases, the proportion not covered by residents increased from 22% in 2005 to 44% in 2007 and 2008 (p < 0.001). CONCLUSIONS: Although some operative cases newly classified as major are technically advanced procedures (eg, Roux-en-Y gastric bypass), other cases are not (eg, breast lesion excision), which raises the issue as to whether the major case category has been diluted by less demanding case types. The implications of these findings may suggest preservation of case volumes at the expense of case quality.

Laparoscopic colectomy significantly decreases length of stay compared with open operation.

INTRODUCTION: Current literature tends not to adjust for biases in patient selection attributable to comorbidities that could provide alternate explanations for length of stay differences in laparoscopic versus open colectomy. We hypothesized that utilizing the National Surgical Quality Improvement Program (NSQIP) dataset and acuity adjustment methods would demonstrate an independent improvement in length of stay for laparoscopic colectomy. METHODS: We used CPT coding to select all colectomies in NSQIP public use files from 2005-2009. Outlier status for surgical length of stay (SLOS) was defined as >75th percentile. Logistic regression analysis was used to predict this outlier status and linear regression to directly predict SLOS. Acuity adjustment was performed by using the most prevalent variables from multiple NSQIP annual reports. This work was done under the approval of our institutional review board and the data use agreement of the American College of Surgeons. Data were analyzed by using SPSS(®). RESULTS: A total of 45,645 colectomies were reviewed, of which 12,455 (27.3%) were laparoscopic. The 75th percentile for SLOS was 11 days. This implied that 9,249 (27.9%) of the open colectomies were outliers, whereas only 1,152 (9.2%) of laparoscopic colectomies were outliers (p < 0.001). When optimizing a simple linear regression to predict SLOS, using common acuity adjustors (i.e., age, functional status, wound category, etc.), the variable marking open procedures consistently had a coefficient of 1.8, implying that open procedures increased SLOS by 1.8 days (p < 0.001). Utilizing logistic regression to predict outlier status, open colectomies were associated with an odds ratio of 3.79 for outlier status (p < 0.001), thus implying an independent effect on SLOS. CONCLUSIONS: These results indicate that laparoscopic colectomy independently decreases SLOS compared with open colectomy. This study is unique in using statistical methods to control for selection bias of patients who might be more "surgically fit."

Using National Surgical Quality Improvement Program (NSQIP) data for risk adjustment to compare Clavien 4 and 5 complications in open and laparoscopic colectomy.

BACKGROUND: Laparoscopic colectomy has been associated with fewer postoperative complications than open colectomy. However, it is unclear whether this is true for the most severe complications typically requiring treatment in an intensive care unit (ICU). The authors hypothesized that laparoscopic colectomy patients have fewer of the most severe complications even after adjustment for comorbidity risk. METHODS: Using the National Surgical Quality Improvement Program (NSQIP) public use files for 2005-2008, the authors identified all laparoscopic (n = 12,455) and open (n = 33,190) colectomies by current procedural terminology (CPT) code. Using the Clavien classification for postoperative complications, they identified NSQIP data points most consistent with Clavien grade 4 complications requiring ICU care (postoperative septic shock, postoperative dialysis, pulmonary embolism, myocardial infarction, cardiac arrest, prolonged ventilatory requirements, need for reintubation) or grade 5 complication (mortality). Statistical analysis was performed using SPSS software. Odds ratios were calculated to compare laparoscopic and open colectomy regarding the probability of having any Clavien class 4 or 5 complication. Logistic regression was performed to account for the effect of preoperative conditions (American Society of Anesthesiology class, wound class, gender, preoperative functional status, preoperative albumin level, azotemia, thrombocytopenia, emergency case, and age >70 years) on complications. RESULTS: The univariate odds ratio showed a 2.27- to 5.52-fold greater likelihood that a patient would have a complication requiring ICU admission if open rather than laparoscopic surgery was performed (p < 0.001). Multivariate logistic regression accounting for preoperative comorbidities that might affect outcome showed persistence of an increase in complications, with an odds ratio range of 1.63 to 2.21. CONCLUSION: Evaluation of the NSQIP database demonstrated that laparoscopic colectomy confers an independent protective effect on the frequency of ICU-level (Clavien grade 4) complications and mortality. The protective effect remained evident after correction for preoperative conditions that might have affected outcome.

Developing a scoring rubric for resident research presentations: a pilot study.

BACKGROUND: A requirement for all Accreditation Council for Graduate Medical Education (ACGME) approved residencies is the provision of "an opportunity for residents to participate in research." To comply with this requirement, most training programs encourage their residents to conduct research and to report their results. Few guidelines exist, however, for assessing the efficacy of the presentations. The goal of this pilot study was to develop a valid, one-page scoring rubric to be used during oral resident research presentations. Such a scoring rubric will facilitate acceptable agreement among faculty raters. METHODS: Content validity was addressed by adhering to the Standards for Educational and Psychological Testing. A one-page, five-domain, behaviorally worded scoring rubric was developed. Inter-rater reliability was derived and three ACGME General Competencies were also addressed within the rubric. RESULTS: The initial scoring rubric was tested with 11 resident oral presentations. The inter-rater reliability was 0.56 using Cronbach's alpha. The rubric was modified and the scale restricted to a 3-point scale. It was then tested with 17 additional presentations, which were independently rated by two general surgery faculty members. Cronbach's Alpha increased to 0.61. CONCLUSIONS: An objective method to evaluate a resident's oral research presentation has been successfully piloted. This content valid rubric possesses good inter-rater reliability according to established guidelines. Clearly defined behaviors have been outlined within the rubric. Program directors will have psychometrically sound evidence for the ACGME. Future research will address generalizability and concurrent validity using other types of resident assessment data.

Local recurrence, distant recurrence and survival of rectal cancer.

PURPOSE: To assess our institution's ability to minimize local and distant recurrence with a preference for sphincter preserving surgery in the management of rectal cancer. METHODS: A retrospective analysis of all patients treated between 1982 and 1998. Patients with Stage 0 (AJCC) disease and those treated for palliation were not included. Clinical and pathologic stage, operation type, adjuvant therapy, recurrence, and survival were compared. Kaplan-Meier analysis was also performed. RESULTS: Rectal cancer was identified in 332 patients (mean follow-up: 5.5 years). One hundred and seventy-three patients (52.1%) underwent low anterior resection, while 107 patients (32.2%) required abdominoperineal resection, 6 patients (1.8%) required exenteration to control disease, and 46 (13.9%) patients were treated with local excision. Of the 332 patients, 63 (19.0%) received adjuvant radiotherapy alone, 85 (25.6%) received combination chemoradiotherapy, and 4 (1.2%) received chemotherapy. Sphincter preserving procedures were used more frequently in the later half of the experience. Local/regional recurrences occurred in 5 patients (3.3%) treated with adjuvant therapy, and in 16 patients (8.9% of total) who did not receive adjuvant therapy (p=0.02, Chi-square test) although the total risk of recurrence (local and/or distant) was not different (30.2% vs. 27.7%, p=0.54). The actuarial rate of local recurrence (regardless of adjuvant therapy) for all stages was 7% at 5 years, and the risk of any recurrence (local or distant) was 21.1% at 5 years. Cancer specific 5-year survival was 77% overall. CONCLUSIONS: In rectal cancer, the therapeutic objectives are to control disease, limit recurrence, and preserve sphincter function; these goals were met for many patients at this institution. These data compare favorably with the current literature. Careful surgical technique and adjuvant therapy can allow successful treatment, even of advanced rectal cancers.

Expiratory flow limitation during gravitational drainage of perfluorocarbons from liquid-filled lungs.

Flow limitation during pressure-driven expiration in liquid-filled lungs was examined in intact, euthanized New Zealand white rabbits. The aim of this study was to further characterize expiratory flow limitation during gravitational drainage of perfluorocarbon liquids from the lungs, and to study the effect of perfluorocarbon type and negative mouth pressure on this phenomenon. Four different perfluorocarbons (PP4, perfluorodecalin, perfluoro-octyl-bromide, and FC-77) were used to examine the effects of density and kinematic viscosity on volume recovered and maximum expiratory flow. It was demonstrated that flow limitation occurs during gravitational drainage when the airway pressure is < or = -15 cm H(2)O, and that this critical value of pressure did not depend on mouth pressure or perfluorocarbon type. The perfluorocarbon properties affect the volume recovered, maximum expiratory flow, and the time to drain, with the most viscous perfluorocarbon (perfluorodecalin) taking the longest time to drain and resulting in lowest maximum expiratory flow. Perfluoro-octyl-bromide resulted in the highest recovered volume. The findings of this study are relevant to the selection of perfluorocarbons to reduce the occurrence of flow limitation and provide adequate minute ventilation during total liquid ventilation.