Large Dead Space Research Articles

Pseudocyst formation after abdominoplasty – extravasations of Morel-Lavallée

SUMMARY. A soft tissue injury can lead to the formation of a pseudocyst in the subcutaneous adipose tissue, due to a seroma, haematoma or fat necrosis. These cysts were first described in 1853 by the French physician Morel-Lavallée.1He observed the phenomenon in the lower limb in women after a tangential trauma with separation of the fatty layers. A similar condition can occur following surgery of the abdomen, when performing liposuction and subcutaneous dissection with a large dead space. In this report we present two cases with large pseudocysts in the abdominal wall, which were seen in long term follow-up after an abdominoplasty performed elsewhere. The pathogenesis, the treatment and the literature are discussed.

Effects of equipment dead space and pediatric breathing patterns on inhaled mass of nebulized budesonide.

Inhaled mass, the quantity of aerosolized drug actually inhaled by a patient, can be estimated in vitro by using a piston pump and an inhaled mass filter in a manner that simulates in vivo aerosol delivery. For pediatric patients, measurement with an inhaled mass filter with a large equipment dead space (VDEQ) in relation to a small tidal volume (VT) may underestimate the inhaled mass. The present study investigated the impact of VDEQ on the accuracy of in vitro measured inhaled mass of budesonide suspension for nebulization using Spira Module 1 jet nebulizers (Respiratory Care Center, Hämeenlinna, Finland), inhaled mass filters, VDEQs of different sizes, and pediatric breathing patterns. The VDEQ varied between 14 and 108 mL, and the breathing patterns corresponded to a VT between 50 and 500 mL, to breathing frequencies of 40 to 12 per min-1, to a duty cycle of 0.5 for all breathing patterns, and to a nebulization time of 2 minutes. The results showed that the inhaled mass was a function of the VDEQ for each breathing pattern as defined by the inspiratory minute volume (VI). For a large VT, a small VDEQ affected the inhaled mass of budesonide only marginally, but as the VDEQ increased, the measured inhaled mass decreased to the point that for a VDEQ larger than the VT, the inhaled mass was zero. When the inhaled mass was expressed as a function of an effective volume (VEFF) (i.e., VI corrected for VDEQ), the results showed a linear correlation (R2 = 0.921) between the volume of aerosol inhaled through the nebulizer and the inhaled mass of budesonide. The results of the study indicate that VDEQ has a critical effect on the measurement of inhaled mass in vitro for conventional jet nebulizers using pediatric breathing patterns. This means that the in vitro measured inhaled mass of drug can seriously underestimate the in vivo value. When pediatric breathing patterns are used in vitro, a correction of the VT by the VDEQ should be made in order to more accurately reflect the in vivo inhaled mass of drug.

Osteochondral Allografts With an Intramedullary Muscle Flap in Rabbits

A model for hemijoint reconstruction using partially demineralized and lyophilized osteochondral allografts combined with an intramedullary muscle flap is described. The proximal 2/3 of the humerus was resected in 10 rabbits. The remaining defect was reconstructed with either a control lyophilized osteochondral allograft or a lyophilized allograft with a muscle flap filling the marrow cavity. Graft healing was followed by serial radiographs and magnetic resonance imaging. The grafts were harvested at 5 weeks for histologic analysis. By 5 weeks, 4 of 5 control allografts had fractured. In contrast, only 1 allograft with an intramedullary muscle flap showed evidence of a cortical break. Magnetic resonance imaging of control allografts showed a persistent large dead space within the marrow cavity and callus formation only at the outer cortical surface. Magnetic resonance imaging of allografts with an intramedullary muscle flap showed muscle obliterating the marrow cavity and areas of callus formation at both the outer and inner cortical surfaces. Histologically, graft incorporation was occurring at the outer cortical surface of the control allografts. In contrast, graft incorporation was occurring at both the outer and inner cortical surfaces of the allografts with an intramedullary muscle flap. The articular surface of the control allografts was severely degenerated. In allografts with an intramedullary muscle flap, the articular surface was smoother. Joints reconstructed with allografts with an intramedullary muscle flap had a significantly better range of motion at 5 weeks compared with control allografts. These results suggest that an intramedullary muscle flap can improve the functional results of joints reconstructed with partially demineralized and lyophilized osteochondral allografts by providing both vascularity and an increased population of mesenchymal stem cells capable of responding to bone morphogenetic proteins that reside in the partially demineralized allograft.

Drains in Thyroid and Parathyroid Surgery: Are They Necessary?

To assess the postoperative complications in patients who underwent elective thyroid or parathyroid surgery without postoperative drainage. During a 6-year period all patients who met study criteria were prospectively evaluated. General community and tertiary referral center. Fifty-seven patients undergoing thyroid surgery and eight patients undergoing parathyroid surgery were evaluated. Twenty-four patients were excluded because drains were placed postoperatively. Reasons for exclusion included presence of a large dead space, substernal goiter, extensive neck dissection for malignant neoplasm, and large goiters. Major complications consisted of a hematoma requiring reexploration in one patient, and a recurrent nerve palsy in one patient. Minor complications consisted of temporary hypocalcemia (three), seroma (one), and superior flap edema that resolved in 3 months (20). Routine prophylactic drainage in a select patient population is unnecessary after uncomplicated thyroid or parathyroid surgery.

A Note of Caution About the Continuous Use of Colorimetric End-Tidal CO2 Detectors in Children

Colorimetric end-tidal CO2 (ETCO2) detectors (Easy Cap, Nellcor Inc, Hayward, CA) are extremely useful in determining the position of the endotracheal tube (ETT) in the airway and have been validated in animals, children, and adults.1-6 They have not been labelled for use in children weighing 15 kg because of their large dead space of 38 mL.1-3 We have demonstrated in numerous studies that the ETCO2 detector accurately verifies the ETT position in infants weighing >2 kg with spontaneous circulation.1-3

Use of the omentum in the management of sternal wound infection after cardiac transplantation.

Seven patients with deep sternal wound infection after orthotopic cardiac transplantation were treated at the Medical College of Virginia-McGuire Veterans Administration Hospitals over a 3-year period. Six patients had mediastinitis with pericardial abscess, and one patient had only sternal osteomyelitis. All patients underwent prompt sternal debridement. In the six patients with mediastinitis, the transplanted heart was surrounded by a large dead space after debridement. This space appeared to result from a size mismatch between the remaining enlarged pericardial sac and the new normal-sized transplanted heart. Wound closure was done at the time of debridement in all patients except one who was closed 3 days later. A pedicled omental flap based on the right gastroepiploic artery was used in five of the six patients with mediastinitis, and these five patients healed their wounds and resolved their infection. Three of these patients are alive and well and two died of later complications other than sternal infection. The patient with only sternal osteomyelitis healed uneventfully. When mediastinitis and intrapericardial infection is present after cardiac transplantation, the omentum appears to provide adequate bulk for obliteration of the large dead space that remains after debridement. This surgery, combined with antibiotic therapy and temporary reduction of immunosuppression, can treat sternal wound infection successfully after cardiac transplantation. Mortality from other complications can occur, however, and not all patients survive.

ＭＲＳＡ関節炎に対する筋皮弁形成術

The incidence of Methicillin-resistant Staphylococcus aureus (MRSA) infections of the joints or bones has increased in recent years. MRSA is less sensitibe to many types of antibiotics, making it a very difficult infection to treat. We treated two patients who had arthritis caused by MRSA, one in the shoulder joint and the other in the hip joint. The patient with arthritis of the shoulder joint had curettage five times followed by surgical treatment with a musculocutaneous flap of Latissimus dorsi. Another patient with paralysis from the spinal level Th7, developed a decubitus MRSA infection of the sacral region and left sided coxarthritis caused by MRSA. In this patient, the decubitus ulcer was treated using a rotation flap, and the coxarthritis was treated with a muscle flap of Rectus Femoris and Vastus Lateralis after three courses of curettage. Recurrence of MRSA infection has not been noted in these two patients for at least one year since their last operation.Musculocutaneous flaps are a good method for treating large dead spaces caused by MRSA infections around joints or over bones.

A remote insertion technique for intracerebral microinjections in freely moving animals

This report describes two improvements to the typical double-cannula microinjection technique. (1) Intracerebral microinjections usually require holding the animal during the insertion of an injector through an implanted guide cannula; however, this is not necessary with the technique described. The injector is made of a long piece of fused silica capillary tubing (145 mm outer diameter × 21.2 cm) which is so small and flexible that it slips through a PE-20 tube (20 cm) that guides it into the implanted guide cannula and down to the desired brain site where it stops. (2) Connection to a microliter syringe is usually done with PE tubing which is leaky, expandable and represents a relatively large dead space that makes it difficult to deliver small, accurate volumes. This problem is avoided by making connection to the syringe via another piece of silica glass capillary tubing. Thus both the injector and its connection to the syringe are made of glass. With these modifications the injector can be inserted without touching the animal, and accurate volumes in the low nanoliter range can be delivered.

The effect of instrumental dead space on measurement of breathing pattern and pulmonary mechanics in the newborn

The effect of the instrumental dead space on breathing pattern and the values of pulmonary mechanics was evaluated because of concern about the relatively large dead space of 26 mL in a commercially available system. Sixty-three healthy newborn infants were studied with a system as commercially supplied, and with the dead space eliminated using a 2 L/min biased flow. This led to a significant reduction in mean (+/- SD) values of respiratory rate from 56.8 (+/- 11.7) to 48.2 (+/- 11.7) breath/min (P < 0.0001), tidal volume from 5.2 (+/- 1.3) to 4.9 (+/- 0.9) mL/kg (P < 0.05), minute volume from 284 (+/- 68) to 220 (+/- 63) mL/min/kg (P < 0.0001), and work of breathing from 13.7 (+/- 6.6) to 11.8 (+/- 7.6) g.cm/kg (P < 0.02). There was a significant increase in dynamic lung compliance from 5.2 (+/- 1.5) to 5.6 (+/- 1.2) mL/cm H2O (P < 0.01) but no difference for total pulmonary resistance 39.6 (+/- 22.8) and 38.8 (+/- 22.2) cm H2O/L/sec. This shows that the instrumental dead space prevents measurement of the basal breathing patterns and alters the values of pulmonary mechanics. It is, therefore, important to use equipment with low dead space or make efforts to remove it by using a biased flow system such as we describe when measuring breathing patterns and pulmonary mechanics in the newborn.

Cause of regional ventilation-perfusion mismatching in patients with idiopathic pulmonary fibrosis: a combined CT and scintigraphic study.

Regional ventilation and perfusion were studied in patients with idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) to seek an explanation for the mismatched ventilation/perfusion (V/Q) seen on scintigrams, which may suggest pulmonary embolic disease. Eight patients with idiopathic pulmonary fibrosis were examined with inspiratory and expiratory CT scans. Planar and tomographic (single-photon emission computed tomography, SPECT) scintigraphy, using inhalation of krypton-81m gas (ventilation) and IV injection of 99mTc-albumin macroaggregates (perfusion), also was performed. The lungs were divided into quadrants (cranial, caudal, right, left) for analysis. Cystic air spaces with a "honeycomb" appearance occupied more than 33% of the cross-sectional area in 75% of all lung quadrants (n = 16), more than 66% of the area in 44% of quadrants, and less than 33% of the area in the remaining 25% of quadrants. On expiratory CT scans, the cross-sectional area of the cystic spaces diminished significantly (unlike emphysematous spaces). Sixty-seven percent of lung quadrants, corresponding to those with marked or moderate involvement with cystic spaces, showed a mismatched V/Q pattern on scintigrams (absent perfusion, normal ventilation); 27% of quadrants had matched V/Q defects, and 6% did not show defects. Two patients had, in addition, large cystic spaces typical of emphysema, but the coexistent fibrosis prevented the gross air trapping seen in bullous emphysema. The cystic air spaces that are often seen on CT scans of patients with idiopathic pulmonary fibrosis are unperfused (probably due to vascular obliteration) but are usually normally ventilated. This V/Q mismatch on scintigrams explains the large physiologic dead space seen at rest and on exercise and could suggest pulmonary embolism unless a CT scan is obtained. Conversely, the larger cystic spaces might be mistaken for emphysema unless V/Q scintigraphy is done.

Selective use of drains in thyroid surgery.

In the past, it was generally advised that every patient undergoing thyroid surgery have a drain placed because of the fear of post-operative hematoma. In the past 9 years, we have performed 400 thyroidectomies. For the first 6 years, we drained the operative site in most of thyroid procedures. However, it was apparent from our experience that drains had very little effect on the prevention of post-operative hematoma or of seroma. As a matter of fact, all four patients who required re-exploration in our initial series had drains in place. As a result of this experience over the past 3 years, during which time we have performed 150 thyroidectomies, we have used drains selectively. The indications for draining the thyroid bed have been the presence of a large dead space, operation for a large substernal goiter, and subtotal thyroidectomy for either large, multinodular goiter or for Graves' disease. Thus, among 150 recent thyroidectomies, we have drained only 35, and avoided drains in 115 patients. Though this is not a prospective study, we found no difference in the overall outcome whether drains were employed or not. Most patients who had no drains were ready for discharge within 24-48 hours of surgery. Since it may be difficult to perform a randomized prospective trial examining the use of drains in thyroid surgery, we propose that drains should be utilized only selectively for thyroid surgery.

Potentiation of exercise ventilatory response by airway CO2 and dead space loading.

We examined the effects of different modes of airway CO2 load on the ventilation-CO2 output (VE-VCO2) relationship during mild to moderate exercise. Four young and three older male subjects underwent incremental steady-state treadmill exercise while breathing a mixture of CO2 in O2 (CO2 loading) or 100% O2 with and without a large external dead space [DS loading and control (C), respectively]. During DS loading, the elevated arterial PCO2 (PaCO2) remained constant from rest to mild exercise and began to increase only at higher work rates. To achieve similar chemical drive, the same PaCO2 levels were established during CO2 loading by external PCO2 forcing. In the young group, CO2 loading resulted in a steepening of the VE-VCO2 relationship compared with C, whereas in the older group the reverse pattern was found. DS loading resulted in a consistent increase in the VE-VCO2 slope compared with C and CO2 loading [39.1 +/- 5.6 (mean +/- SD) vs. 24.9 +/- 5.0 and 26.7 +/- 4.4, respectively] in all subjects. The difference in potentiation of VE-VCO2 by CO2 and DS loading was not due to differences in mean chemical drive or changes in breathing pattern. Thus changes in the profile of airway CO2 influx may have an independent influence on ventilatory CO2-exercise interaction. Peripheral chemoreceptors mediation, although important, is not obligatory for this behavior.

Drug delivery from holding chambers with attached facemask.

There is much interest in the use of holding chambers with an attached facemask to deliver aerosols from metered dose inhalers to infants. In order to study the influence of various design factors on the dose inhaled at different tidal volumes, a model was constructed in which a Starling ventilator was used to generate an inspiratory/expiratory cycle across a filter. Sodium cromoglycate was administered via a Nebuhaler and mask, Aerochamber and mask, and a coffee cup using tidal volumes of 25, 50, and 150 ml and the dose deposited upon the filter after six breaths was assayed using an ultraviolet spectrophotometric method. At the lowest tidal volume the high aerosol concentration in the smaller chamber enhanced drug delivery while at the highest tidal volume delivery was greatest from the larger chamber reflecting the larger dose available. Multiple breaths ensured that the dose inhaled per kilogram from each chamber was relatively large and also permitted significant drug delivery despite the introduction of a relatively large dead space between valve and filter. The dose delivered was increased by increasing the dose introduced into the chamber though not proportionately. These devices appear likely to deliver significant quantities of aerosol to infants, though drug delivery may be enhanced by the use of an appropriate valve.

Pulmonary function and resting breathing pattern in myotonic dystrophy.

In 17 patients with myotonic dystrophy, spirometric, flow-volume, and maximal mouth occlusion variables were obtained and compared with 8 normal subjects. Ventilatory CO2 response was measured by the estimation of the steady-state effect of a sufficiently large serial dead space. Variability of resting breathing pattern was expressed by the variation coefficients of respiratory cycle time and tidal volume. The group means of the total lung capacity (TLC), vital capacity (VC), forced expiratory volume in 1 sec (FEV)1 and forced inspiratory volume in 1 sec (FIV)1 showed a restrictive pattern. Only maximal static mouth pressure (Pi,max), measured at residual volume (RV) level, showed a significant positive correlation with both VC (p = 0.03) and FIV1 (p = 0.02), suggesting inspiratory muscle weakness as a determinant of the restriction. Although the differences were just not significant, both variation coefficients of the respiratory cycle time and tidal volume were larger in the group with a CO2 sensitivity below the lower limit of normal compared to those with a normal ventilatory response to CO2. In 3 patients, fluctuations in FRC were also present. We hypothesize that, in addition to the already documented FRC fluctuations by uncoordinated spontaneous intercostal muscle action, a defect of integration of afferent neural input and chemical drive in the medullary region may also be present in these patients.

A Minimal-flow System for Xenon Anesthesia

We described a minimal-flow system for xenon anesthesia during controlled ventilation. A computer maintained oxygen concentration in the anesthesia circle within +/- 2% of the value set by the anesthesiologist. The ventilator and the circle were connected via a large dead space, through which oxygen from the ventilator entered the circle but which prevented xenon from escaping. This arrangement simplified the computer program. The system was tested on a lung model and in six pigs (37-39 kg). The xenon expenditure and the amount of xenon washed out from the pigs after the anesthetic were measured. Additional experiments with nitrous oxide were made in three pigs. The xenon expenditure during 2 h of xenon anesthesia was 7.6 +/- 0.8 l (mean +/- 1 standard deviation). The corresponding expenditure of nitrous oxide was 16.5 +/- 2.7 l. About 75% of the xenon expenditure was in the 1st h of anesthesia; thereafter 20-40 ml.min-1 was needed to maintain oxygen concentration at 30%. Nitrogen concentration in the circle increased to 12-16% during the xenon anesthetic, although it was preceded by a 20 min denitrogenation period. During the washout phase after the xenon anesthesia, mean expired xenon concentration decreased to below 2% within 4 min. Subsequently, washout was slower and the expired concentration remained above 0.1% for more than 90 min. The estimated total amount of xenon washed out from the lungs and body tissues during 4 h of oxygen breathing was about 4 l. We conclude that xenon anesthesia via a fully automated minimal-flow system is feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical ventilation during low‐flow anaesthesia. Experience with an alternative to the bag‐in‐bottle

Clinical experience with low-flow anaesthesia during controlled ventilation of the lungs is described. The anaesthesia circle is separated by a corrugated hose that serves as a large deadspace. This open connexion has no bellows or overflow valve and therefore the risk of mechanical dysfunction is small. No mixing of circle and ventilator gas occurs during normal operation. Major decreases in the oxygen concentration in the system are unlikely even if the fresh gas flow is interrupted or significant leaks from the circle occur because 100% oxygen is delivered by the ventilator. A hose volume larger than 1650 ml prevented gas mixing at tidal volumes of 380-1170 ml. There was no system-related mishap in over 600 patients, who comprised about 40% of the neurosurgical patients anaesthetised during that period. The cost of isoflurane was reduced to about 33% of that incurred during previous periods.

Operative treatment of substernal goiters.

This report describes the operative experience in 72 patients with substernal goiters treated over the past 5.5 years. Even though the incidence of multinodular goiter has decreased in the United States due to the routine use of iodized salt, we continue to see a large number of patients with massive goiters, predominantly from Caribbean Islands. The diagnosis of substernal goiter was made on clinical examination augmented by such radiologic studies, as chest x-ray, barium esophagograms, airway films, and CT scans. Computed tomographic (CT) scanning was particularly helpful in evaluating the extent of substernal extension. Confirmation of the extent of disease was made at the time of operation. Ninety percent of the patients had tracheal deviation and 85% were symptomatic from airway compression. Esophageal compression was noted in 60% of the patients. All patients had a long history of goiter with recent onset of pressure symptoms. Flow-volume-loop studies were performed in 44% of the patients and were useful in the evaluation of pressure symptoms. However, the decision for operation was made primarily based on clinical evaluation of signs and symptoms. Sixteen patients in this group were admitted with acute airway distress requiring airway intubation or semi-emergency decompression. Only 1 patient required mediastinal splitting, while all others were operated by the cervical approach. The decision as to the extent of thyroidectomy was made at the time of operation. Drains were routinely used because of the large dead space. One patient developed a hematoma in the recovery room and required re-exploration.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise and Cystic Fibrosis: A Review.

Cystic fibrosis (CF) results in chronic obstructive pulmonary disease with progressive increases in areas of the lung with poor gas exchange (dead space). The pulmonary response to exercise is characterized by a higher than expected minute ventilation (V̇E). In some patients the elevated V̇Eis inadequate to overcome the large dead space, resulting in decreases in arterial oxygen and/or increases in arterial carbon dioxide levels during exercise. Chronic lung hyperinflation in patients with severe disease limits the ability to increase tidal volume, and therefore V̇E, during exercise. Most patients can exercise without decreases in arterial oxygen and should be encouraged to participate in regular activity. Oxygen supplementation during exercise allows many patients with severe lung dysfunction to participate in some form of activity. Regular exercise has been shown to be of some benefit and should be encouraged on an individual basis in patients with CF.

Resting oxygen consumption and ventilation in cystic fibrosis.

Resting oxygen consumption (VO2) and minute ventilation (VE) were measured on nine control subjects and 13 patients with cystic fibrosis (CF). In patients with CF, VO2 was 20% higher (P less than 0.01) when expressed per m2 and 47% higher (P less than 0.001) when expressed per kg body weight, and VE was 58% higher when expressed per m2 and 94% higher when expressed per kg body weight (P less than 0.001) than in control subjects. Repeated measures of VO2 and VE were highly reproducible over 2 hours (within-subject coefficients of variation: in controls, VO2 = 5.5%, VE = 7.4%; in CF, VO2 = 3.1%, VE = 5.1%). Since the increases in VE were greater than those in VO2, the ventilatory equivalent (VE/VO2) was 32% higher in CF than in controls. We conclude that size-corrected total energy expenditures and VE at rest are higher in patients with CF than in control subjects. Ventilation appears mechanically inefficient but necessary to keep arterial PCO2 from rising and oxygen saturation from falling at rest. Our results are consistent with observations that these patients have an abnormally large physiological dead space (Featherby et al.: Ann Rev Respir Dis 1969; 102:737).

Physiological responses to exercise at 47 and 66 ATA.

Five male volunteers served as subjects for exercise studies during three dives to pressures of 47 and 66 ATA while breathing gases containing 0.5 ATA PO2 and varying amounts of N2 and He. The inspired gas density ranged from 1.1 g/l (BTPS) at the surface to 17.1 g/l at the highest pressure. Dyspnea at rest and during exercise was evident in all divers and was predominantly inspiratory in nature. Despite the dyspnea, divers were able to perform work requiring an O2 consumption larger than 2 l/min STPD at each depth. Compared with surface measurements, moderate work at depth was associated with alveolar hypoventilation, arterial hypercapnia, very large physiological dead space, and higher levels of arterial lactate and signs of simultaneous respiratory and metabolic acidosis. The increase of ventilation that accompanies the onset of acidemia at the surface was not present at depth. Acidemia at depth was more severe, and its onset occurred at lesser work rates than at 1 ATA. No large differences could be ascertained when a variety of responses obtained with inspired gas having a density of 7.9 g/l at 47 ATA were compared with those obtained with an inspired gas density of 17.1 g/l at 66 ATA. It appears that the major impact of the environment on the physiological responses to work was almost fully manifested at a pressure of 47 ATA with a He-O2 gas mixture. It is cautioned that maximum work tolerance may be an insufficient assessment of the physiological condition of a diver exposed to these high pressures.