Cancellation of Elective Cases in a Recently Opened, Tertiary/Quaternary-Level Hospital in the Middle East.

Case cancellations have a negative financial impact due to revenue loss and the potential costs of underutilized time. The goals of this study at a recently opened hospital in the Middle East were to measure the cancellation rates for elective surgical or endoscopic cases and to identify the reasons for cancellation. During the 1-month study period, 170 (22.4%) of the 760 scheduled cases were cancelled. Cultural norms and patient no-shows on the day of surgery accounted for the majority of case cancellations. Understanding local factors on hospital functions may be vital for organizations expanding into new geographic areas.

"Ventilatory alternans": a left-right alternation of inspiratory airflow in humans.

In a study visualizing ventilation with hyperpolarized (3)He magnetic resonance imaging (MRI) in elite breath hold divers, the dynamic MRI images in one subject exhibited an apparent alternation of the image intensity between left and right lung. We hypothesized that the alternation resulted from alternating variations in inspiratory flow rate to left and right lungs. Analysis showed that the alternation was not due to random uncorrelated temporal fluctuations of intensity (p<0.001). The frequency of alternation was approximately 56 min(-1), suggesting a cardiac origin. Similar alternation of ventilation was confirmed retrospectively in 4 of 6 additional subjects. These observations are consistent with previous studies showing cardiogenic mixing of gas in the lung. We speculate that cardiogenic pendelluft, possibly from ballistic lateral motion of the beating heart, could cause alternating variations of inspiratory flow to the lungs.

Static inflation and deflation pressure-volume curves from excised lungs of marine mammals.

Excised lungs from eight marine mammal species [harp seal (Pagophilus groenlandicus), harbor seal (Phoca vitulina), gray seal (Halichoerus grypush), Atlantic white-sided dolphin (Lagenorhynchus acutus), common dolphin (Delphinus delphis), Risso's dolphin (Grampus griseus), long-finned pilot whale (Globicephala melas) and harbor porpoise (Phocoena phocoena)] were used to determine the minimum air volume of the relaxed lung (MAV, N=15), the elastic properties (pressure-volume curves, N=24) of the respiratory system and the total lung capacity (TLC). Our data indicate that mass-specific TLC (sTLC, l kg(-1)) does not differ between species or groups (odontocete vs phocid) and agree with that estimated (TLC(est)) from body mass (M(b)) by applying the equation: TLC(est)=0.135 M(b)(0.92). Measured MAV was on average 7% of TLC, with a range from 0 to 16%. The pressure-volume curves were similar among species on inflation but diverged during deflation in phocids in comparison with odontocetes. These differences provide a structural basis for observed species differences in the depth at which lungs collapse and gas exchange ceases.

Inhalation heterogeneity from subresidual volumes in elite divers.

Punctate reopening of the lung from subresidual volumes (sub-RV) is commonly observed in excised lung preparations, either degassed or collapsed to zero transpulmonary pressure, and in the course of reinflation of human lungs when the chest is open, secondary to traumatic or surgical pneumothoraxes. In the course of physiological studies on two elite breath-hold divers, who are able to achieve lung volumes well below traditional RV with glossopharyngeal exsufflation, we used MRI lung imaging with inhaled hyperpolarized (129)Xe to visualize ventilatory patterns. We observed strikingly inhomogeneous inhalation patterns with small inhalation volumes from sub-RV, consistent with reopening of frankly closed airways. On the other hand, two age-matched and two older controls, inhaling from just above RV, showed a much more homogeneous pattern. Our results demonstrate the concept of frank airway closure below RV in young healthy adults with an intact chest wall.

Extending submarine crew survival by reducing CO2 production with quickly reversible sedation.

INTRODUCTION: CO2 accumulation may limit crew survival in a disabled submarine. Reversible sedation using diazepam and flumazenil was proposed to reduce CO2 production. METHODS: Two groups of three resting subjects were studied during a 48-h placebo phase with diazepam and flumazenil placebos, followed by a 48-h drug phase with oral diazepam to induce sedation and intranasal flumazenil to reverse it. CO2 exchange was measured every 2.5 h; twice a day, cognitive testing and meals were preceded by placebo or flumazenil. Return to sedated state was produced with either placebo or diazepam. In the drug phase, initial diazepam doses (10 to 40 mg) were followed by maintenance doses to achieve sedation corresponding to Alertness Scores of 3 or 4. RESULTS: In the drug phase, subjects received a total of 360-495 mg of diazepam (with doses of 5-40 mg), average alertness score was 3.75, and mean Vco2 was 14% less than in the placebo phase (0.212 vs. 0.248 L x min(-)). Subjects were 21-36% less active when sedated with diazepam. The mean flumazenil dose to restore full alertness was 0.36 mg, with subjects being conversant and oriented within 5 min, performing cognitive tasks at 86-97% of their baseline. Subjects could follow instructions and ambulate independently, though unsteadily 6 h after final flumazenil dose; at 72 h they exhibited normal cognitive and physical functions. DISCUSSION: Reversible sedation to lower crew metabolism in a disabled submarine may be effective, safe, and practical.

Expansion of postoperative pneumothorax and pneumomediastinum: determining when it is safe to fly.

INTRODUCTION: The possibility of expansion of pneumothorax (PTX) and/or pneumomediastinum (PMED) during commercial flights makes air travel after thoracic surgery particularly worrisome. Guidelines from the Aerospace Medical Association (AsMA) suggest delaying air travel 2 to 3 wk following uncomplicated thoracic surgery and 1 wk following radiographic resolution of PTX; they also state that PTX is an "absolute contraindication" to air travel. However, both AsMA guidelines and thoracic surgeons' recommendations for postoperative air travel require further examination. METHODS: We reviewed the literature looking for evidence supporting official guidelines and conducted a survey of U.S. thoracic surgeons about their recommendations for air travel by patients with postoperative PTX and/or PMED. RESULTS: We found no experimental evidence supporting the AsMA guidelines. Of the 68 thoracic surgeons who returned our questionnaire, 44% recommended that patients wait variable periods of time of up to 42 d (13.8 +/- 11.6 d) following complete resolution of PTX prior to air travel, while 46% of them allowed their patients to fly with some degree of PTX. Following mediastinoscopy, 76.9% of the surgeons allowed their patients to fly without delay, even with PMED. The only adverse in-flight event reported was a case of thoracic pain during ascent. DISCUSSION: A wide variability exists among thoracic surgeons regarding their recommendations for air travel by patients with postoperative PTX and/or PMED. Both AsMA guidelines and surgeons' recommendations should rely more on scientific evidence. Studies of PTX and PMED expansion during simulated flight are needed to develop better guidelines.

Early healing of transcolonic and transgastric natural orifice transluminal endoscopic surgery access sites.

BACKGROUND: Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a developing, minimally invasive surgical approach whose potential benefits are being investigated. Little is known about secure access site closure and early healing kinetics of transvisceral access. STUDY DESIGN: Transvisceral access incisions were created in the colon (C-NOTES, n = 8) and stomach (G-NOTES, n = 8) for peritoneal exploration. Incisions were closed primarily with endoloops, endoclips, or t-tags. Macroscopic and histologic analyses performed on postoperative day 7 assessed gross appearance, granulation tissue, inflammation, ulceration, and complications. RESULTS: Macroscopically, incisions appeared closed without intraperitoneal spillage. Incisions closed by endoloop and t-tags showed intense granulation tissue fill of defect despite partial (G-NOTES, n = 3) and transmural ulceration (C-NOTES, n = 8; G-NOTES, n = 3). Of the 30 t-tags applied, 40% broke or deployed into the peritoneal cavity. Endoclip closures (C-NOTES, n = 1; G-NOTES, n = 1) did not show histologic mucosal continuity. Healing complications included transmural necrosis (C-NOTES, n = 1; G-NOTES, n = 1), foreign body material (C-NOTES, n = 3; G-NOTES, n = 2), and microabscesses (G-NOTES, n = 1). CONCLUSIONS: This study provides a reproducible model to assess noninvasive repair of planned visceral perforations. Of investigated technologies, endoloop closure was favored for transcolonic incisions, and t-tags with omental patch for transgastric incisions, although these have significant limitations. Endoclips were inadequate for primary closure, but may be useful as an adjunctive closure modality. Additional studies are needed to examine visceral repair at later time points, as they will help determine the quality and kinetics of repair of a variety of incision closure strategies. This study demonstrates the need for improved technologies to more reliably close visceral transluminal defects.

Marked pericardial inhomogeneity of specific ventilation at total lung capacity and beyond.

We measured regional ventilation at 1l above functional residual capacity (FRC+1L) and total lung capacity (TLC) in three normal subjects and four elite breath-hold divers, and above TLC after glossopharyngeal insufflation (TLC+GI) in the divers. Hyperpolarized (3)He MRI was used to map the local ventilation per unit volume over the entire lung. At TLC and above, there was markedly increased regional ventilation of the lungs in the pericardial region compared with the relatively uniform ventilation throughout the rest of the lung. The distribution of fractional ventilation regionally was relatively uniform at FRC+1L, with a small non-gravitational cephalocaudal gradient of specific ventilation in the supine posture. Our observations at high lung volumes are consistent with the effect of high pleural tension in the concave pericardial region, which promotes expansion of the subjacent lung, leading to a higher local effective compliance and a higher specific ventilation.

A fluoroscopic and laryngoscopic study of glossopharyngeal insufflation and exsufflation.

Glossopharyngeal breathing, frequently performed by elite breath-hold divers, relies on muscles of the mouth and pharynx to move air into (glossopharyngeal insufflation, GI) and out of the lungs (glossopharyngeal exsufflation, GE). GI has also been used by patients with weak respiratory muscles. Fluoroscopic and endoscopic examinations were performed on four divers (three of whom were world record holders) during both GI and GE maneuvers. A detailed pictorial description of both GI and GE, with online video material that includes external, endoscopic and fluoroscopic examinations, is provided in this publication. Both GI and GE are accomplished with a coordinated series of contractions by glossopharyngeal muscles and they rely on a piston pump-like action of the larynx. In particular, the larynx moves extensively and repeatedly up and down, to either inject air into (GI) or extract it from the lungs (GE), with the vocal cords functioning as a valve. During both maneuvers, when the larynx is in its highest position, the epiglottis does not fold back, unlike what happens during swallowing.

Estimates of N2 narcosis and O2 toxicity during submarine escapes from 600 to 1,000 fsw.

The U.S. Navy recommends submarine escape for depths down to 600 fsw, with deeper escapes entailing the risks of decompression sickness, nitrogen (N2) narcosis and CNS oxygen (O2) toxicity. However, the escape equipment, including the submarine escape and immersion equipment and the escape trunk, could probably function even at 1,000 fsw. Here we report a theoretical analysis of the risks of both N2 narcosis and CNS O2 toxicity for different escape profiles from 600 to 1,000 fsw. The effect of N2 narcosis, calculated as a function of N2 pressure in the brain using Gas Man software, was expressed as equivalent narcosis depth (END), corresponding to the depth at which the same pressure of N2 would be produced in the brain after five minutes of scuba diving with air. The risk of O2-induced convulsions was estimated using the model developed by Arieli et al. Different dwell times (DTs) at maximal pressure in the escape trunk (from 0 to 60 s) and lungs-to-brain circulation times (10 to 30 s) were included in our analysis. When DT in the escape trunk is very short (e.g., 10 s), the risk of either incapacitating N2 narcosis and/or O2-induced convulsions occurring in the trunk is low, even during escapes from 1,000 fsw.

The air hunger response of four elite breath-hold divers.

Normal subjects terminate breath-holds due to intolerable 'air hunger'. We hypothesize that competitive breath-hold divers might have increased tolerance of air hunger. We tested the air hunger (AH) response of four divers who could hold their breath for 6-9 min. Tidal volume and respiratory rate were controlled by mechanical ventilation (ventilation approximately 0.16 L min(-1) kg(-1)). AH was induced by raising PCO2 and rated using a visual analog scale whose maximum was defined as intolerable. SpO2 was maintained at >97%. Three divers reported the same uncomfortable urge to breathe as normal subjects; the slopes of their responses were within normal range. Both resting CO2 and AH threshold were shifted to higher CO2 in some divers. Diver 3 was unique amongst neurologically intact subjects we have studied: he denied feeling an urge to breathe, and denied discomfort. We conclude that elite divers' strategies to tolerate intense air hunger are a minor factor in their ability to tolerate long breath-holds.

Utilization of arterial blood gas measurements in a large tertiary care hospital.

We describe the patterns of utilization of arterial blood gas (ABG) tests in a large tertiary care hospital. To our knowledge, no hospital-wide analysis of ABG test utilization has been published. We analyzed 491 ABG tests performed during 24 two-hour intervals, representative of different staff shifts throughout the 7-day week. The clinician ordering each ABG test was asked to fill out a utilization survey. The most common reasons for requesting an ABG test were changes in ventilator settings (27.6%), respiratory events (26.4%), and routine (25.7%). Of the results, approximately 79% were expected, and a change in patient management (eg, a change in ventilator settings) occurred in 42% of cases. Many ABG tests were ordered as part of a clinical routine or to monitor parameters that can be assessed clinically or through less invasive testing. Implementation of practice guidelines may prove useful in controlling test utilization and in decreasing costs.

Transpulmonary pressures and lung mechanics with glossopharyngeal insufflation and exsufflation beyond normal lung volumes in competitive breath-hold divers.

Throughout life, most mammals breathe between maximal and minimal lung volumes determined by respiratory mechanics and muscle strength. In contrast, competitive breath-hold divers exceed these limits when they employ glossopharyngeal insufflation (GI) before a dive to increase lung gas volume (providing additional oxygen and intrapulmonary gas to prevent dangerous chest compression at depths recently greater than 100 m) and glossopharyngeal exsufflation (GE) during descent to draw air from compressed lungs into the pharynx for middle ear pressure equalization. To explore the mechanical effects of these maneuvers on the respiratory system, we measured lung volumes by helium dilution with spirometry and computed tomography and estimated transpulmonary pressures using an esophageal balloon after GI and GE in four competitive breath-hold divers. Maximal lung volume was increased after GI by 0.13-2.84 liters, resulting in volumes 1.5-7.9 SD above predicted values. The amount of gas in the lungs after GI increased by 0.59-4.16 liters, largely due to elevated intrapulmonary pressures of 52-109 cmH(2)O. The transpulmonary pressures increased after GI to values ranging from 43 to 80 cmH(2)O, 1.6-2.9 times the expected values at total lung capacity. After GE, lung volumes were reduced by 0.09-0.44 liters, and the corresponding transpulmonary pressures decreased to -15 to -31 cmH(2)O, suggesting closure of intrapulmonary airways. We conclude that the lungs of some healthy individuals are able to withstand repeated inflation to transpulmonary pressures far greater than those to which they would normally be exposed.

Short-term noninvasive ventilation in the postanesthesia care unit: a case series.

Eight patients suffering various causes of transient postoperative respiratory failure in the postanesthesia care unit were treated with short-term noninvasive pressure-support ventilation administered through a tight-fitting face mask. Intubation was avoided in all of them, and no complications were observed, as assessed by the treating anesthesiologist and from review of their charts. Indications and advantages of noninvasive ventilation in the early postoperative period are discussed.