Acute pulmonary edema and airway hemorrhage in a goat during sevoflurane anesthesia

A goat was scheduled for experimental surgery under general anesthesia. The first attempt of performing endotracheal intubation failed and provoked laryngeal spasm. After repeated succesful intubation of inhalation anesthesia was delivered in high concentrations of sevoflurane. Suddenly hypertension and tachycardia were observed, followed by foamy airway secretion and then severe airway hemorrhage. The authors hypothesize that laryngeal spasm provoked respiratory distress and pulmonary edema. The delivered high concentrations of sevoflurane probably enhanced a hyperadrenergic response, predisposing to the development of airway hemorrhage.

[Intrathoracic esophageal perforation of unknown cause in four horses] Intrathorakale Oesophagusperforation ungeklärter Genese bei vier Pferden

Three horses (age 17 - 23 years) were referred to the equine clinic of the University of Berne due to colic, fever, tachycardia and tachypnea. All horses showed pleural effusion. Clinical findings in 2 of the horses were highly suggestive of an intra-thoracic esophageal perforation. Severe septic pleuropneumonia without suspicion of an esophageal lesion was diagnosed in the 3rd horse. In addition, an 11 year old stallion was referred to the equine clinic for treatment of a presumptive large colon impaction. The horse was given laxatives after nasogastric intubation. Subsequent dramatic clinical deterioration and signs consistent with severe pleuropneumonia suggest that esophageal perforation had occurred when passing the nasogastric tube. All 4 horses were euthanized due to a poor prognosis. Esophageal perforation was diagnosed or confirmed post mortem in all cases. A hypertrophy of the tunica muscularis of the intra-thoracic esophagus was found in 3 of 4 horses.

Pediatric severe asthma is characterized by eosinophilia and remodeling without T(H)2 cytokines

BACKGROUND: The pathology of pediatric severe therapy-resistant asthma (STRA) is little understood. OBJECTIVES: We hypothesized that STRA in children is characterized by airway eosinophilia and mast cell inflammation and is driven by the T(H)2 cytokines IL-4, IL-5, and IL-13. METHODS: Sixty-nine children (mean age, 11.8 years; interquartile range, 5.6-17.3 years; patients with STRA, n = 53; control subjects, n = 16) underwent fiberoptic bronchoscopy, bronchoalveolar lavage (BAL), and endobronchial biopsy. Airway inflammation, remodeling, and BAL fluid and biopsy specimen T(H)2 cytokines were quantified. Children with STRA also underwent symptom assessment (Asthma Control Test), spirometry, exhaled nitric oxide and induced sputum evaluation. RESULTS: Children with STRA had significantly increased BAL fluid and biopsy specimen eosinophil counts compared with those found in control subjects (BAL fluid, P < .001; biopsy specimen, P < .01); within the STRA group, there was marked between-patient variability in eosinophilia. Submucosal mast cell, neutrophil, and lymphocyte counts were similar in both groups. Reticular basement membrane thickness and airway smooth muscle were increased in patients with STRA compared with those found in control subjects (P < .0001 and P < .001, respectively). There was no increase in BAL fluid IL-4, IL-5, or IL-13 levels in patients with STRA compared with control subjects, and these cytokines were rarely detected in induced sputum. Biopsy IL-5(+) and IL-13(+) cell counts were also not higher in patients with STRA compared with those seen in control subjects. The subgroup (n = 15) of children with STRA with detectable BAL fluid T(H)2 cytokines had significantly lower lung function than those with undetectable BAL fluid T(H)2 cytokines. CONCLUSIONS: STRA in children was characterized by remodeling and variable airway eosinophil counts. However, unlike in adults, there was no neutrophilia, and despite the wide range in eosinophil counts, the T(H)2 mediators that are thought to drive allergic asthma were mostly absent.

Accidental entrapment of an endo-bronchial blocker tip by a surgical stapler during selective ventilation for lung lobectomy in a dog

OBJECTIVE: To describe the use of an endobronchial blocker (EBB) and to perform selective ventilation during pulmonary lobe resection via thoracotomy in a dog and report its accidental stapling in the resection site. STUDY DESIGN: Clinical case report. ANIMAL: One female dog with a suspected abscess or neoplasia of the right caudal pulmonary lobe. METHODS: One-lung ventilation was performed using a wire-guided EBB to seal the contaminated parenchyma and facilitate surgical access. The affected lung parenchyma was resected and the resection site was closed with staples. RESULTS: Lobar resection was performed successfully, but the loop of the EBB guide wire was inadvertently entrapped in the staple line of the lobectomy. Staples were removed to release the wire loop, and the resulting air leak caused loss of ventilation control until the parenchyma was re-sealed. CONCLUSIONS: We recommend removing the wire guide associate with the EBB after successful lung separation to avoid accidents that could have life-threatening consequences if not recognized. CLINICAL RELEVANCE: One-lung ventilation is useful to isolate healthy parenchyma from diseased parenchyma during lobectomy. Anesthesiologists and surgeons need to be aware of the potential complications associated with use of EBB.

Closed-loop control of mean arterial blood pressure during surgery with alfentanil: clinical evaluation of a novel model-based predictive controller

BACKGROUND: In contrast to hypnosis, there is no surrogate parameter for analgesia in anesthetized patients. Opioids are titrated to suppress blood pressure response to noxious stimulation. The authors evaluated a novel model predictive controller for closed-loop administration of alfentanil using mean arterial blood pressure and predicted plasma alfentanil concentration (Cp Alf) as input parameters. METHODS: The authors studied 13 healthy patients scheduled to undergo minor lumbar and cervical spine surgery. After induction with propofol, alfentanil, and mivacurium and tracheal intubation, isoflurane was titrated to maintain the Bispectral Index at 55 (+/- 5), and the alfentanil administration was switched from manual to closed-loop control. The controller adjusted the alfentanil infusion rate to maintain the mean arterial blood pressure near the set-point (70 mmHg) while minimizing the Cp Alf toward the set-point plasma alfentanil concentration (Cp Alfref) (100 ng/ml). RESULTS: Two patients were excluded because of loss of arterial pressure signal and protocol violation. The alfentanil infusion was closed-loop controlled for a mean (SD) of 98.9 (1.5)% of presurgery time and 95.5 (4.3)% of surgery time. The mean (SD) end-tidal isoflurane concentrations were 0.78 (0.1) and 0.86 (0.1) vol%, the Cp Alf values were 122 (35) and 181 (58) ng/ml, and the Bispectral Index values were 51 (9) and 52 (4) before surgery and during surgery, respectively. The mean (SD) absolute deviations of mean arterial blood pressure were 7.6 (2.6) and 10.0 (4.2) mmHg (P = 0.262), and the median performance error, median absolute performance error, and wobble were 4.2 (6.2) and 8.8 (9.4)% (P = 0.002), 7.9 (3.8) and 11.8 (6.3)% (P = 0.129), and 14.5 (8.4) and 5.7 (1.2)% (P = 0.002) before surgery and during surgery, respectively. A post hoc simulation showed that the Cp Alfref decreased the predicted Cp Alf compared with mean arterial blood pressure alone. CONCLUSION: The authors' controller has a similar set-point precision as previous hypnotic controllers and provides adequate alfentanil dosing during surgery. It may help to standardize opioid dosing in research and may be a further step toward a multiple input-multiple output controller.

Model-based control of neuromuscular block using mivacurium: design and clinical verification

BACKGROUND: Short-acting agents for neuromuscular block (NMB) require frequent dosing adjustments for individual patient's needs. In this study, we verified a new closed-loop controller for mivacurium dosing in clinical trials. METHODS: Fifteen patients were studied. T1% measured with electromyography was used as input signal for the model-based controller. After induction of propofol/opiate anaesthesia, stabilization of baseline electromyography signal was awaited and a bolus of 0.3 mg kg-1 mivacurium was then administered to facilitate endotracheal intubation. Closed-loop infusion was started thereafter, targeting a neuromuscular block of 90%. Setpoint deviation, the number of manual interventions and surgeon's complaints were recorded. Drug use and its variability between and within patients were evaluated. RESULTS: Median time of closed-loop control for the 11 patients included in the data processing was 135 [89-336] min (median [range]). Four patients had to be excluded because of sensor problems. Mean absolute deviation from setpoint was 1.8 +/- 0.9 T1%. Neither manual interventions nor complaints from the surgeons were recorded. Mean necessary mivacurium infusion rate was 7.0 +/- 2.2 microg kg-1 min-1. Intrapatient variability of mean infusion rates over 30-min interval showed high differences up to a factor of 1.8 between highest and lowest requirement in the same patient. CONCLUSIONS: Neuromuscular block can precisely be controlled with mivacurium using our model-based controller. The amount of mivacurium needed to maintain T1% at defined constant levels differed largely between and within patients. Closed-loop control seems therefore advantageous to automatically maintain neuromuscular block at constant levels.

Airway remodelling in children with cystic fibrosis

BACKGROUND: The relationship between airway structural changes and inflammation is unclear in early cystic fibrosis (CF) lung disease. A study was undertaken to determine changes in airway remodelling in children with CF compared with appropriate disease and healthy controls. METHODS: Bronchoalveolar lavage and endobronchial biopsy were performed in a cross-sectional study of 43 children with CF (aged 0.3-16.8 years), 7 children with primary ciliary dyskinesia (PCD), 26 with chronic respiratory symptoms (CRS) investigated for recurrent infection and/or cough and 7 control children with no lower airway symptoms. Inflammatory cells, cytokines, proteases and matrix constituents were measured in bronchoalveolar lavage fluid (BALF). Reticular basement membrane (RBM) thickness was measured on biopsy specimens using light microscopy. RESULTS: Increased concentrations of elastin, glycosaminoglycans and collagen were found in BALF from children with CF compared with the CRS group and controls, each correlating positively with age, neutrophil count and proteases (elastase activity and matrix metalloproteinase-9 (MMP-9) concentration). There were significant negative correlations between certain of these and pulmonary function (forced expiratory volume in 1 s) in the CF group (elastin: r = -0.45, p<0.05; MMP-9:TIMP-1 ratio: r = -0.47, p<0.05). Median RBM thickness was greater in the CF group than in the controls (5.9 microm vs 4.0 microm, p<0.01) and correlated positively with levels of transforming growth factor-beta(1) (TGF-beta(1); r = 0.53, p = 0.01), although not with other inflammatory markers or pulmonary function. CONCLUSIONS: This study provides evidence for two forms of airway remodelling in children with CF: (1) matrix breakdown, related to inflammation, proteolysis and impaired pulmonary function, and (2) RBM thickening, related to TGF-beta(1) concentration but independent of other markers of inflammation.

Non-invasive neurally adjusted ventilatory assist in rabbits with acute lung injury

OBJECTIVE: Neurally adjusted ventilatory assist uses the electrical activity of the diaphragm (EAdi)-a pneumatically-independent signal-to control the timing and pressure of the ventilation delivered, and should not be affected by leaks. The aim of this study was to evaluate whether NAVA can deliver assist in synchrony and proportionally to EAdi after extubation, with a leaky non-invasive interface. DESIGN AND SETTING: Prospective, controlled experimental study in an animal laboratory. ANIMALS: Ten rabbits, anesthetized, mechanically ventilated. INTERVENTIONS: Following lung injury, the following was performed in sequential order: (1) NAVA delivered via oral endotracheal tube with PEEP; (2) same as (1) without PEEP; (3) non-invasive NAVA at unchanged NAVA level and no PEEP via a single nasal prong; (4) no assist; (5) non-invasive NAVA at progressively increasing NAVA levels. MEASUREMENTS AND RESULTS: EAdi, esophageal pressure, blood gases and hemodynamics were measured during each condition. For the same NAVA level, the mean delivered pressure above PEEP increased from 3.9[Symbol: see text]+/-[Symbol: see text]1.4[Symbol: see text]cmH(2)O (intubated) to 7.5[Symbol: see text]+/-[Symbol: see text]3.8[Symbol: see text]cmH(2)O (non-invasive) (p[Symbol: see text]<[Symbol: see text]0.05) because of increased EAdi. No changes were observed in PaO(2) and PaCO(2). Increasing the NAVA level fourfold during non-invasive NAVA restored EAdi and esophageal pressure swings to pre-extubation levels. Triggering (106[Symbol: see text]+/-[Symbol: see text]20[Symbol: see text]ms) and cycling-off delays (40[Symbol: see text]+/-[Symbol: see text]21[Symbol: see text]ms) during intubation were minimal and not worsened by the leak (95[Symbol: see text]+/-[Symbol: see text]13[Symbol: see text]ms and 33[Symbol: see text]+/-[Symbol: see text]9[Symbol: see text]ms, respectively). CONCLUSION: NAVA can be effective in delivering non-invasive ventilation even when the interface with the patient is excessively leaky, and can unload the respiratory muscles while maintaining synchrony with the subject's demand.

Electroencephalographic changes after pediatric cardiac surgery with cardiopulmonary bypass: is slow wave activity unfavorable?

Pediatric cardiac surgery with cardiopulmonary bypass (CPB) is frequently associated with neurologic deficits. We describe the postoperative EEG changes, assess their possible causes, and evaluate their relevance to neurologic outcome. Thirty-one children and five neonates with congenital heart disease were included. EEG recording started after intubation and continued until 22-96 h after CPB. In addition to conventional analysis, spectral analysis was performed for occipital and frontal electrodes, and differences between pre- and postoperative delta power (delta-deltaP) were calculated. Maximum values of occipital delta-deltaP that occurred within 48 h after CPB were correlated with clinical variables and with perioperative markers of oxidative stress and inflammation. Occipital delta-deltaP correlated with frontal delta-deltaP, and maximum delta-deltaP correlated with conventional rating. Distinct rise of deltaP was detected in 18 of 21 children without any acute or long-term neurologic deficits but only in five of 10 children with temporary or permanent neurologic deficits. Furthermore, maximally registered delta-deltaP was inversely associated with duration of CPB and postoperative ventilation. Maximal delta-deltaP was also inversely associated with the loss of plasma ascorbate (as an index of oxidative stress) and plasma levels of IL-6 and IL-8. Slow wave activity frequently occurs within 48 h after CPB. However, our data do not support the notion that EEG slowing is associated with adverse neurologic outcome. This is supported by the fact that EEG slowing was associated with less oxido-inflammatory stress.

Heart rate variability does not discriminate between different levels of haemodynamic responsiveness during surgical anaesthesia

BACKGROUND: Hypnotic depth but not haemodynamic responsiveness is measured with EEG-based monitors. In this study we compared heart rate variability (HRV) in unstimulated patients and stimulation-induced HRV at different levels of anaesthesia. METHODS: A total of 95 ASA I or II patients were randomly assigned to five groups (Group 1: BIS 45(5), remifentanil 1 ng ml(-1); Group 2: BIS 45(5), remifentanil 2 ng ml(-1); Group 3: BIS 45(5), remifentanil 4 ng ml(-1); Group 4: BIS 30(5), remifentanil 2 ng ml(-1); Group 5: BIS 60(5), remifentanil 2 ng ml(-1)). A time- and frequency-domain analysis of the RR interval (RRI) from the electrocardiogram was performed. HRV before induction, before and after a 5 s tetanic stimulus of the ulnar nerve, and before and after tracheal intubation was compared between groups, between stimuli, and between responders to intubation [systolic arterial pressure (SAP) increase >20 mm Hg, a maximal heart rate (HR) after intubation >90 min(-1) or both] and non-responders (anova). RESULTS: Induction of anaesthesia significantly lowered HR and HRV. Mean RRI before stimulation was higher in G3 than in G1, G2, and G4 (P < 0.001), whereas the other HRV parameters were similar. Intubation induced a greater HRV response than tetanic stimulation. The mean RRI after intubation was lower in G3 compared with the other groups and the sd of the RRI after tetanic stimulation was lower in G3 compared with G5. Otherwise, unstimulated HRV and stimulation-induced HRV were similar in responders and non-responders. CONCLUSION: HRV parameters discriminate between awake and general anaesthesia, are different after tracheal intubation and a 5 s ulnar nerve stimulation, but do not discriminate between different levels of haemodynamic responsiveness during surgical anaesthesia.

Increased airway smooth muscle mass in children with asthma, cystic fibrosis, and non-cystic fibrosis bronchiectasis

RATIONALE: Structural alterations to airway smooth muscle (ASM) are a feature of asthma and cystic fibrosis (CF) in adults. OBJECTIVES: We investigated whether increase in ASM mass is already present in children with chronic inflammatory lung disease. METHODS: Fiberoptic bronchoscopy was performed in 78 children (median age [IQR], 11.3 [8.5-13.8] yr): 24 with asthma, 27 with CF, 16 with non-CF bronchiectasis (BX), and 11 control children without lower respiratory tract disease. Endobronchial biopsy ASM content and myocyte number and size were quantified using stereology. MEASUREMENTS AND MAIN RESULTS: The median (IQR) volume fraction of subepithelial tissue occupied by ASM was increased in the children with asthma (0.27 [0.12-0.49]; P < 0.0001), CF (0.12 [0.06-0.21]; P < 0.01), and BX (0.16 [0.04-0.21]; P < 0.01) compared with control subjects (0.04 [0.02-0.05]). ASM content was related to bronchodilator responsiveness in the asthmatic group (r = 0.66, P < 0.01). Median (IQR) myocyte number (cells per mm(2) of reticular basement membrane) was 8,204 (5,270-11,749; P < 0.05) in children with asthma, 4,504 (2,838-8,962; not significant) in children with CF, 4,971 (3,476-10,057; not significant) in children with BX, and 1,944 (1,596-6,318) in control subjects. Mean (SD) myocyte size (mum(3)) was 3,344 (801; P < 0.01) in children with asthma, 3,264 (809; P < 0.01) in children with CF, 3,177 (873; P < 0.05) in children with BX, and 1,927 (386) in control subjects. In all disease groups, the volume fraction of ASM in subepithelial tissue was related to myocyte number (asthma: r = 0.84, P < 0.001; CF: r = 0.81, P < 0.01; BX: r = 0.95, P < 0.001), but not to myocyte size. CONCLUSIONS: Increases in ASM (both number and size) occur in children with chronic inflammatory lung diseases that include CF, asthma, and BX.

Bronchial and bronchovascular sleeve resection for treatment of central lung tumors

BACKGROUND: To improve postoperative pulmonary reserve, we have employed parenchyma-sparing resections for central lung tumors irrespective of pulmonary function. The results of lobectomy, pneumonectomy, and sleeve resection were analyzed retrospectively. METHODS: From October 1995 to June 1999, 422 typical lung resections were performed for lung cancer. Of these, 301 were lobectomies (group I), 81 were sleeve resections (group II), and 40 were pneumonectomies (group III). RESULTS: Operative mortality was 2% in group I, 1.2% in group II, and 7.5% in group III (group I and II vs. group III, p<0.03). Mean time of intubation was 1.0+/-4.1 days in group I, 0.9+/-1.3 days in group II, and 3.6+/-11.2 days in group III (groups I and II vs. group III, p<0.01). The incidence of bronchial complications was 1.3% in group I, none in group II, and 7.5% in group III (group I and II vs group III, p<0.001). After 2 years, survival was 64% in group I, 61.9% in group II, and 56.1% in group III (p = NS). Freedom from local disease recurrence was 92.1% in group I, 95.7% in group II, and 90.9% in group III after 2 years (p = NS). CONCLUSIONS: Sleeve resection is a useful surgical option for the treatment of central lung tumors, thus avoiding pneumonectomy with its associated risks. Morbidity, early mortality, long-term survival, and recurrence of disease after sleeve resection are similar to those seen after lobectomy.

Late results after percutaneous closure of patent foramen ovale for secondary prevention of paradoxical embolism using the amplatzer PFO occluder without intraprocedural echocardiography: effect of device size

OBJECTIVES: We sought to assess the safety and clinical efficacy of patent foramen ovale (PFO) closure under fluoroscopic guidance only, without intraprocedural echocardiography. BACKGROUND: Percutaneous PFO closure has been shown to be safe and feasible using several devices. It is generally performed using simultaneously fluoroscopic and transesophageal or intracardiac echocardiographic guidance. Transesophageal echocardiography requires sedation or general anesthesia and intubation to avoid aspiration. Intracardiac echocardiography is costly and has inherent risks. Both lengthen the procedure. The Amplatzer PFO Occluder (AGA Medical Corporation, Golden Valley, Minnesota) can be safely implanted without echocardiographic guidance. METHODS: A total of 620 patients (51 +/- 12 years; 66% male) underwent PFO closure using the Amplatzer PFO Occluder for secondary prevention of presumed paradoxical embolism. Based on size and mobility of the PFO and the interatrial septum, an 18-mm device was used in 50 patients, a 25-mm device in 492, and a 35-mm device in 78. RESULTS: All procedures were successful, with 5 procedural complications (0.8%): 4 arteriovenous fistulae requiring elective surgical correction, and 1 transient ischemic attack. Contrast transesophageal echocardiography at 6 months showed complete closure in 91% of patients, whereas a minimal, moderate, or large residual shunt persisted in 6%, 2%, and 1%, respectively. During a mean follow-up period of 3.0 +/- 1.9 years (median: 2.6 years; total patient-years: 1,871), 5 ischemic strokes, 8 transient ischemic attacks, and no peripheral emboli were reported. Freedom from recurrent ischemic stroke, transient ischemic attack, or peripheral embolism was 99% at 1 year, 99% at 2 years, and 97% at 5 years. CONCLUSIONS: The Amplatzer PFO Occluder affords excellent safety and long-term clinical efficacy of percutaneous PFO closure without intraprocedural echocardiography.

Anaesthesia with medetomidine, midazolam and ketamine in six gorillas after premedication with oral zuclopenthixol dihydrochloride

OBJECTIVE To evaluate the effects of medetomidine, midazolam and ketamine (MMK) in captive gorillas after premedication with oral zuclopenthixol. STUDY DESIGN Case series. ANIMALS Six gorillas, two males and four females, aged 9-52 years and weighing 63-155 kg. METHODS The gorillas were given zuclopenthixol dihydrochloride 0.2 ± 0.05 mg kg(-1) per os twice daily for 3 days for premedication. On the day of anaesthesia the dose of zuclopenthixol was increased to 0.27 mg kg(-1) and given once early in the morning. Anaesthesia was induced with medetomidine 0.04 ± 0.004 mg kg(-1) , midazolam 0.048 ± 0.003 mg kg(-1) and ketamine 4.9 ± 0.4 mg kg(-1) intramuscularly (IM). Upon recumbency, the trachea was intubated and anaesthesia was maintained on 1-2% isoflurane in oxygen. Physiological parameters were monitored every 10 minutes and arterial blood gas analysis was performed once 30-50 minutes after initial darting. At the end of the procedure, 42-115 minutes after initial darting, immobilisation was antagonized with atipamezole 0.21 ± 0.03 mg kg(-1) and sarmazenil 5 ± 0.4 μg kg(-1) IM. RESULTS Recumbency was reached within 10 minutes in five out of six animals. One animal required two additional darts before intubation was feasible. Heart rate ranged from 60 to 85 beats minute(-1) , respiratory rate from 17 to 46 breaths minute(-1) and temperature from 36.9 to 38.3 °C. No spontaneous recoveries were observed and anaesthetic level was stable. Blood gas analyses revealed mild respiratory acidosis, and mean PaO(2) was 24.87 ± 17.16 kPa (187 ± 129 mmHg) with all values being above 13.4 kPa (101 mmHg). Recovery was smooth and gorillas were sitting within 25 minutes. CONCLUSION AND CLINICAL RELEVANCE The drug combination proved to be effective in anaesthetizing captive gorillas of various ages and both sexes, with minimal cardio-respiratory changes.

Effect of continuous gastric enteral feeding on tonometric measurement of gastric intramucosal carbon dioxide levels in healthy volunteers

Purpose. The aim of this research was to evaluate the effect of enteral feeding on tonometric measurement of gastric regional carbon dioxide levels (PrCO2) in normal healthy volunteers. Design and methods. The sample included 12 healthy volunteers recruited by the University Clinical Research Center (UCRC). An air tonometry system monitored PrCO2 levels using a tonometer placed in the lumen of the stomach via orogastric intubation. PrCO2 was automatically measured and recorded every 10 minutes throughout the five hour study period. An oral dose of famotidine 40 mg was self-administered the evening prior to and the morning of the study. Instillation of Isocal® High Nitrogen (HN) was used for enteral feeding in hourly escalating doses of 0, 40, 60, and 80 ml/hr with no feeding during the fifth hour. Results . PrCO2 measurements at time 0 and 10 minutes (41.4 ± 6.5 and 41.8 ± 5.7, respectively) demonstrated biologic precision (Levene's Test statistic = 0.085, p-value 0.774). Biologic precision was lost between T130 and T140 40 when compared to baseline TO (Levene's Test statistic = 1.70, p-value 0.205; and 3.205, p-value 0.042, respectively) and returned to non-significant levels between T270 and T280 (Levene's Test statistic = 3.083, p-value 0.043; and 2.307, p-value 0.143, respectively). Isocal® HN significantly affected the biologic accuracy of PrCO2 measurements (repeated measures ANOVA F 4.91, p-value <0.001). After 20 minutes of enteral feeding at 40 ml/hr, PrCO2 significantly increased (41.4 ± 6.5 to 46.6 ± 4.25, F = 5.4, p-value 0.029). Maximum variance from baseline (41.4 ± 6.5 to 61.3 ± 15.2, F = 17.22, p-value <0.001) was noted after 30 minutes of Isocal® HN at 80 ml/hr or 210 minutes from baseline. The significant elevations in PrCO2 continued throughout the study. Sixty minutes after discontinuation of enteral feeding, PrCO2 remained significantly elevated from baseline (41.4 ± 6.5 to 51.8 ± 9.2, F = 10.15, p-value 0.004). Conclusion. Enteral feeding with Isocal® HN significantly affects the precision and accuracy of PrCO2 measurements in healthy volunteers. ^