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PubMed1993

Dynamic measurement of gas composition in the middle ear. II: Steady state values.

On-line measurement of ME gas composition in normal middle ears of 5 anesthetized guinea pigs at an established steady state was performed by mass spectrometry. The mean values for the gas composition of the middle ear were found to be: PN2: 82.4%, PO2: 7.6% and PCO2: 10.0%. This composition is very different from that of atmospheric air, and very similar to the gas composition of mixed venous blood. Our conclusions are that the gas composition is basically controlled by interchange with gases present in the blood and not by introduction of air through the eustachian tube. It is therefore proposed that middle ear gas deficiency is secondary not to eustachian tube input failure but to excess loss of middle ear gas due to enhanced diffusion into the blood. This situation exists especially under inflammatory conditions when there is an enlarged number of blood vessels promoting increased gas diffusion into them. Under ordinary conditions this middle ear gas deficiency will probably cause no significant underpressure because the mastoid pneumatization will act as a pressure buffer. When mastoid pneumatization is lacking, as happens in the otitis media syndrome, a pathological negative pressure will ensue.

Animals↗
PubMed1996

Gas composition of the human nose and nasopharyngeal space.

Since it was established that middle ear (ME) gas composition is closer to venous gas composition than to air, the question arose regarding the composition of gas which enters the ME from the nasopharynx. Using a mass spectrometer, gaseous partial pressure was measured at three locations in the nose and nasopharynx of 6 volunteers. All three locations showed similar gas composition (O2 = 15.7%, CO2 = 4.5%, N2 + Ar = 79.8%) which is similar to expired air. The gas that enters the ME via the Eustachian tube is a mixture closer to the final ME gas equilibrium than is air. This minimizes the changes in steady state ME gas composition incurred by gas influx into the ME.

Air↗
PubMed1999

Avoiding hyperoxemia at the start of cardiopulmonary bypass while optimizing gas flow and temperature.

There seems to be a wide range of practice in relation to the optimum oxygen setting before, and at the start of, cardiopulmonary bypass. Even manufacturers of blood oxygenators vary in their suggestions for this phase of extracorporeal circulation. Most of these suggestions are based on peak performance, Association for the Advancement of Medical Instrumentation (AAMI) standards, experience, and legal considerations. Therefore, suggested gas:blood flow ratios will vary from no gas flow at the start of bypass, to a ratio setting of 1:1. On the other hand, suggested inspired oxygen concentrations will generally vary between 0.80 to 1.0 at the start of cardiopulmonary bypass. In regard to perfusate temperatures before going on bypass, there are no clearly defined standards other than those of clinical preference. The manufacturer of the oxygenator used in this study clearly states in the operating instructions that gas flow should be proportional to blood flow at the start of bypass, and gas flow should be turned off when there is no fluid flow through the oxygenator. The presence of hyperoxic perfusates and wide patient/perfusate temperature gradients at the start of bypass has been suspected in the appearance of gaseous microemboli during this critical period. Hyperoxemia during the bypass period is also implicated in the introduction of oxygen free radicals and nitric oxide into the hypoxic myocardium during cardioplegia delivery. Presented here are the results of a randomized clinical study involving 39 adult patients undergoing cardiopulmonary bypass for the surgical treatment of coronary artery disease. All patients were randomly selected into five groupings. The first group had 1 L of gas flow through the perfusate before bypass, and bypass was then started with an FIO2 of 0.80. The second two groups had no gas flow through the perfusate prior to bypass and a starting FIO2 of 0.21. Groups 4 and 5 had 1 L of gas flowing through the perfusate and a starting FIO2 of 0.21. Results indicate that gas flow through Normosol R/Albumin perfusates will prevent the acidosis that is found in this solution when the system is previously flushed with carbon dioxide. Also, suggested high FIO2 settings will produce hyperoxic perfusates at the start of cardiopulmonary bypass. However, the use of an FIO2 of 0.21 at the start of bypass will produce normoxemic conditions that are both safe and reliable for the conduct of initiating cardiopulmonary bypass.

Adult↗
PubMedDate not supplied

Innovative gas injection technique for closed-hollow obturator.

PURPOSE: The purpose of this study was to determine the proper prerequisite conditions for gas injection and the steps for applying gas injection for obturator fabrication. MATERIALS AND METHODS: Optimal prerequisite conditions were investigated by using thermocoupling to verify exothermic changes in the resin during polymerization. Three experimental groups were designated: in the control group (C), resin was packed into the mold without argon gas injection; in the gas injection group (GI), after resin packing, gas was injected into the resin bulb in the mold; and in the plunger/gas injection group (PGI), after resin packing, the syringe plunger was drawn out before gas injection. RESULTS: The 55 degrees C mold temperature and addition of 0.3% DMPT to the monomer liquid caused differences in exothermic temperature increase in various parts of the resin. Without gas injection and plunger drawing, porosity was observed in the thick bulbs of groups C and PGI. In group PGI, a balloon-like elliptic hollow was observed. Compared to group C, the weight reduction in group PGI was approximately 10%. CONCLUSION: Proper mold temperature with secondary venting and the addition of DMPT were required before the injection of gas. The resulting prosthesis could be fabricated in one step and required no resin seal.

Argon↗
PubMed2004

Risk of gas embolism in hand-assisted versus total laparoscopic hepatic resection.

Laparoscopic hepatic resection represents an alternative to open surgery in patients with advanced underlying hepatic disease. Management of haemorrhage and the risk of gas embolism are the major problems in laparoscopic liver surgery. In this study, safety and efficacy of liver dissection using ultrasonic energy was investigated in hand-assisted versus total laparoscopic surgery. The study had a special emphasis on evaluating the risk of gas embolism during both procedures. Female pigs were divided into two groups for A) total laparoscopic (n=7), and B) hand-assisted laparoscopic (n=7) hepatic resection. For tissue dissection, an ultrasound aspirator (CUSA) was used in both groups. Laparoscopic procedure was performed under a CO2 pneumoperitoneum (intraperitoneal pressure: 12 mmHg). Before dissection, a Pringle manoeuver was carried out. The anaesthetized pigs were monitored haemodynamically by an arterial line and Swan-Ganz catheter. Transoesophageal echocardiography (TEE) was performed with special attention to the right atrium and ventricle. Gas emboli were graded according to size and correlated with haemodynamic and blood-gas data. In both groups, the ultrasound-aspirator enabled an effective tissue dissection. In total laparoscopic hepatic resection, TEE monitoring disclosed gas embolism in 5/7 (71%) animals. In 3/7 (42%) animals, gas embolism was accompanied by a sequence of cardiac arrhythmia. No direct correlation was noted between episodes of embolism and blood-gas variables. None of the pigs died after episodes of embolization. In hand-assisted liver resection, no air embolism was noted. The internal hand impressively facilitated organ exposure and provided an immediate and efficient haemorrhage control. The use of an ultrasound aspirator system enables an effective laparoscopic hepatic dissection. Total laparoscopic liver dissection is at increased risk for gas embolism, whereas hand-assisted laparoscopic procedure appears to reduce this risk. Due to tactile response and facilitated retraction of the liver parenchyma, the hand-assisted procedure shows impressive advantages in laparoscopic liver surgery.

Animals↗
PubMed1991

A simple radiologic method to estimate the quantity of bowel gas.

Patients with functional bowel disorders frequently complain of bloating and abdominal pain, but no practical method is available to measure intestinal gas objectively. To evaluate a new technique, we evaluated 54 abdominal radiographs from 19 patients. A gastroenterologist and a radiologist independently outlined the intestinal gas bubbles in these films. Areas of gas bubbles were measured with a computer digitizing board. Bowel gas was also measured in 24 healthy controls, and in five emergency room patients, supine and erect radiographs were compared to evaluate the effects of position on bowel gas patterns. The two evaluators agreed well on the measured areas of bowel gas (r = 0.96), showing that this is a reliable method. Bowel gas was significantly greater in patients than in controls but did not correlate with symptoms. Bowel gas was significantly greater in supine than upright films, showing that the position of the patient must be standardized.

Adult↗
PubMed1990

[Fresh gas flow and artificial respiration in anesthesia. Technical requirements for the adequate use of rebreathing systems].

The majority of modern anaesthetic machines is designed for the rebreathing method. But frequently high fresh gas flows are employed, thus minimising the rebreathing fraction of expiratory gases. However, only by reducing the fresh gas flow substantially, the advantages of the rebreathing technique can be obtained. To evaluate the practicability of flow reduction, minimal flow anaesthesia was carried out with four different anaesthetic machines: AV 1 (Drägerwerk AG, Lübeck), ELSA (Gambro Engström AB, Bromma, Sweden), SULLA 808 V (Drägerwerk AG, Lübeck) und VIVOLEC (Hoyer Medizintechnik, Bremen). Fresh gas flow was reduced to 0.5 l/min after an initial phase of 15-20 min, during which the fresh gas flow was kept at a high level of 4.4 l/min. The minute volumes before and after fresh gas flow reduction were compared. The minute volume decreased markedly and significantly in the SULLA 808 group, whereas it remained nearly unchanged in the AV 1, the ELSA, and the VIVOLEC groups. The differences result from different modes of fresh gas delivery into the breathing circuit. If anaesthetic apparatus that maintain their tidal volume with different fresh gas flow rates are employed, rebreathing systems may be used judiciously by changing the fresh gas flow according to the individual uptake or any particular clinical requirement.

Adult↗
PubMed1993

[Endoscopic argon gas coagulation--initial clinical experiences].

Argon-gas-coagulation represents a new method of contact free electrocoagulation, where RF-energy is applied to the tissue by means of ionized argon-gas. In the operative field argon-gas-coagulation has been used with success for hemostasis in several parenchymatous organs and for devitalization of various tissues. Experimental studies have shown the superiority of argon-gas-coagulation over standard electrocoagulation and surgical techniques due to its high efficiency and limited tissue traumatization. Having developed and designed special endoscopic probes and after in-vitro-studies we could utilize the method in flexible endoscopy as well. From June 1991 to September 1992, 102 patients were treated in 189 sessions with argon-gas-coagulation in the upper and lower gastrointestinal tract as well as respiratory system. The indications were: malignant and benign tumors, diffuse hemorrhages of various origins and of various sites, tissue overgrowth after stent-implantation, remaining tissue after endoscopic adenomectomy and conditioning of fistulas prior to fibrin sealing. In all cases argon-gas-coagulation in flexible endoscopy has been shown to be a very effective and easy to perform technique with advantages in comparison to standard electrocoagulation. Problems and complications have not been observed. The limited depth of tissue penetration (2-3 mm) coincident with efficient tissue coagulation allows the application even in critical areas such as the duodenum or colon. In many indications argon-gas-coagulation has replaced the former widely used Nd-YAG-laser in our unit. Except vaporisation of extended tumors, the argon-gas-coagulator shows remarkable advantages for nearly all applications.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenomatous Polyposis Coli↗
PubMedDate not supplied

[The prenatal mechanisms of gas homeostasis].

This article discusses the physiological mechanisms of blood gas homeostasis in the prenatal period. Support of gas homeostasis is one of the most important systems providing for normal growth and development of an embryo. In the first period, the gas homeostasis of an embryo is provided by mother's organism. However, later this function is transferred to fetus. The satisfactory results depend, above all, on the adaptive changes in blood circulation. Simultaneously, the second chain of the functional systems is developing. After birth it is generally used in the form of the respiratory and general movements in response to breathing motivation. It can also appear in the prenatal period in case of deviation of the internal environment parameters to the extent when the adaptive changes in blood circulation are inadequate to compensate for gas deficit. In a fetus the breathing motivation is in most cases expressed in patterns or successive series of movements. Movement patterns have no direct adaptive role, because the result of the actions is evaluated and directed not by reverse afferentation accompanying the movement, but by its possible result modified by the humoral system. Formation of the second part of functional system supporting gas homeostasis, is significantly impacted by the situation and the starting stimulus. This is clear from the fetus response to contact with air. In this situation the adaptive behavior provides the successful birth of an organism. Under the impact of breathing motivation, the fetus demonstrates the ability to afferent synthesis of inner irritation with autostimulus, which comes from external environment (perception of gravitation, locomotion of swimming and walking, negative reaction to water, defensive reaction, etc.). Nasal contact with air produces the breathing movements typical for a newborn. The paper discusses the steps of maturation of the components of the functional system supporting gas homeostasis, the central elements of the process, the role of respiration movements after gas exchange is maintained by lungs, the role of the lung gas exchange in displays of the functional system in question, and other regularities of systemogenesis.

Animals↗
PubMed2006

Does gas exchange response to prone position predict mortality in hypoxemic acute respiratory failure?

OBJECTIVE: To determine whether gas exchange response to a first prone position session can predict patient outcome in hypoxemic acute respiratory failure. METHODS: Data from a previous multicenter randomized controlled trial were retrospectively analyzed for relationship between PaO(2)/FIO(2) ratio and PaCO(2) changes during the first 8-h prone position session to day 28 mortality rate; 370 prone position sessions were analyzed. Arterial blood gas was measured in supine position before proning and in prone position at the end of the session. Gas exchange improvement was defined as increase in the PaO(2)/FIO(2) ratio of more than 20% (PaO(2)R) or decrease in PaCO(2) of more than 1 mmHg (PaCO(2)R). MAIN RESULTS: The 28-day mortality rate was 26.5% in PaO(2)R-PaCO(2)R, 31.7% in PaO(2)R-PaCO(2)NR, 38.9% in PaO(2)NR-PaCO(2)R, and 43% in PaO(2)NR-PaCO(2)NR (log-rank 14.02, p = 0.003). In a Cox proportional hazards model the gas exchange response was a significant predictor to patient outcome with a 82.5% increase in risk of death in the case of PaO(2)NR-PaCO(2)R or PaO(2)NR-PaCO(2)NR, relative to the gas exchange improvement response (odds ratio 1.825). However, after adjusting for the difference in oxygenation between day 2 and day 1 the gas exchange response does no longer reach significance. CONCLUSION: In patients with hypoxemic acute respiratory failure initial improvement in gas exchange in the first PP session was associated with a better outcome, but this association disappeared when the change in oxygenation from day 1 to day 2 was taken into account, suggesting that underlying illness was the most important predictor of mortality in this patient population.

Blood Gas Analysis↗
PubMed1985

Influence of G-suit abdominal bladder inflation on gas exchange during +GZ stress.

Available data relating duration of +GZ stress to blood gas exchange status is limited. Furthermore, studies focusing on pulmonary gas exchange during +GZ stress when abdominal restriction is imposed have yielded conflicting results. To examine the time course of blood gas changes occurring during exposure to +GZ stress in dogs and the influence of G-suit abdominal bladder inflation on this time course, seven spontaneously breathing pentobarbital-anesthetized adult mongrel dogs were exposed to 60 s of up to +5 GZ stress with and without G-suit abdominal bladder inflation. Arterial and mixed venous blood were sampled for blood gas analysis during the first and last 20 s of the exposure and at 3 min postexposure. Little change in blood gas status was seen at +3 GZ regardless of G-suit status. However, with G-suit inflation, arterial PO2 fell by a mean of 14.7 Torr during the first 20 s at +4 Gz (P less than 0.01, t test) and 20.6 Torr at +5 GZ (P less than 0.01). It continued to fall an additional 10 Torr during the next 40 s at both +4 and +5 GZ. Arterial PO2 was still 5-10 Torr below control values (P less than 0.05) 3 min postexposure. A second series of experiments paralleling the first focused on blood gas status during repeated exposure to acceleration. Blood gas status was assessed in five dogs during the late 20 s of two 60-s exposures separated by 3 min at 0 GZ. No significant differences between the initial and repeated exposures were detected. The data indicate that G-suit abdominal bladder inflation promotes increased venous admixture.

Acceleration↗
PubMed2002

Assessment of the respiratory exchange ratio in mechanically ventilated patients by a standard anaesthetic gas analyser.

BACKGROUND: The respiratory exchange ratio (R) is the CO2 production divided with O2 consumption. R is an essential factor included in several formulas during routine blood gas analysis. Instant and individual measurement of R may be of particular interest to improve the evaluation of each single patient. A standard anaesthetic gas analyser has been recommended for measurement of R among spontaneously breathing healthy subjects, but there is no experience using this method among mechanically ventilated critically ill patients. This study validates the assessment of R by a Brüel & Kjaer gas analyser (B & K) during positive pressure ventilation of intensive care patients. METHODS: The B & K sampled gas from 11 mechanically ventilated patients over a period of 5 min. The recordings of end-tidal values of O2 and CO2 based on fractions (RF) allowed for calculation of RF by the alveolar equation solved for R. The continuous recordings of corresponding values were depicted into an O2-CO2 diagram. A developed computer program calculated estimates of R as the slope of the regression lines related to the full cycle (Rfull) and the expiratory phase only (Rexp). Corrected values of the full respiratory cycle (Rfull*) were also calculated assuming changes of CO2 and O2 volumes during gas exchange. The different estimates of R were compared with simultaneous measurement of a Deltatrac indirect calorimeter (Rdelta). RESULTS: Ten values of RF were within the expected interval of 0.72 < R < 1.00. For the full respiratory cycles, the mean R-value was 0.94 +/- 0.07 and for the expiratory phase the mean R-value was 0.82 +/- 0.08. The O2-CO2 diagram appeared as a convexo-convex loop during each cycle. The agreement of Rexp and Rdelta (Rexp-Rdelta: 0.01 +/- 0.13) were good. CONCLUSION: This study demonstrates that gas measurements by a standard anaesthetic gas monitor can be used for determination of R, and thereby we present an alternative to R calculation made by the Deltatrac monitor.

Adult↗
PubMed1984

Mechanisms of abnormal gas exchange during anesthesia.

A review of the literature and of our recent data (obtained by computer-based analysis of multiple inert gas elimination) re-emphasizes the significant gas exchange disturbances found to occur during general anesthesia which develop for probably several reasons. In this report we suggest firstly that the reduction in functional residual capacity (FRC) may well be an effect of anesthesia just as is abnormal gas exchange. In other words, the reduction in FRC is not per se the cause of gas exchange disturbances, but rather occurs alongside them. Secondly, the causes of abnormal gas exchange may have more to do with local ventilatory reserve in lung regions, be that reserve via the existence of collateral ventilation as in dogs or via acute or chronic airway pathology in disease. Thus, species without adequate collateral ventilation or with some degree of airway disease would seem to be at greatest risk of developing highly significant gas exchange disturbances during general anesthesia. We speculate that this vulnerability is probably due to multiple factors that change as a result of the particular anesthetic agents used. Such factors include altered hypoxic vasoconstriction, a change in airway secretions and clearance of those secretions, changes in bronchomotor tone, changes in surfactant activity, and alveolar volume loss due to rapid uptake of soluble anesthetic gases like nitrous oxide. To qualitatively and quantitatively distinguish amongst these various potential factors will require experimental protocols and techniques of a highly controlled and accurate nature. That in 1983 we still do not understand the basic mechanisms behind abnormal gas exchange during anesthesia attests to the difficulty of mounting such an experiment.

Adult↗
PubMed1996

Intra-arterial blood gas monitoring system: more accurate values can be obtained.

OBJECTIVE: To compare values measured by a continuous intra-arterial blood gas monitoring system with those measured by conventional blood gas analyzer for the assessment of the clinical performance of a new device for measurement of PaO2, PaCO2, and arterial pH. METHODS: Forty-six patients undergoing cardiopulmonary bypass were enrolled in this study. All patients had a continuous intra-arterial sensor (PB 3300) placed into the radial artery through a 20-gauge catheter. A total of 319 arterial blood gas and pH values were obtained for comparison with a conventional blood gas analyzer. The measurements were performed every 12 hrs after the initial in vitro calibration of the sensor for each patient. RESULTS: Measurements were made over a range of 12 to 192 hrs. The overall bias and precision determined by the two methods were 4.5 and 17.1 mmHg for PaO2; 4.5 and 6.2 mmHg for PaCO2; and 0.009 and 0.035 for pH, respectively. For the range of PO2 less than 150 mmHg, the bias and precision improved to 4.2 and 9.5 mmHg. The sensor-derived PCO2 value, PCO2 (IABG), increased significantly more than the conventional blood gas analysis value, PCO2(ABG), even within 72 hrs (2.8 and 4.1 mmHg). The relationship between the two measurements can be described as: PCO2(IABG)/PCO2(ABG) = 1 + 0.0026.t where t is the time period of use (in hours). By correcting the PCO2(IABG) value using this formula, the overall bias and precision of the values measured by two methods decreases to -0.4 and 3.6 mmHg. CONCLUSIONS: The PO2 and pH values derived from an intra-arterial blood gas monitoring system agreed well with the values measured by a conventional blood gas analyzer. However, the PCO2 value must be corrected due to an increase of drift, especially with extended use for more than 72 hours.

Blood Gas Analysis↗
PubMed2001

New perspectives in breath-by-breath determination of alveolar gas exchange in humans.

Alveolar gas transfer over a given breath (i) was determined in ten subjects at rest and during steady-state cycling at 60, 90 or 120 W as the sum of volume of gas transferred at the mouth plus the changes of the alveolar gas stores. This is given by the gas fraction (FA) change at constant volume plus the volume change (deltaVAi) at constant fraction i.e. VAi-1(FAi-FAi-1)+FAi x deltaVAi, where VAi-1 is the end-expiratory volume at the beginning of the breath. These quantities, except for VAi-1, can be measured on a single-breath (breath-by-breath) basis and VAi-1 set equal to the subject's functional residual capacity (FRC, Auchincloss model). Alternatively, the respiratory cycle can be defined as the interval elapsing between two equal expiratory gas fractions in two successive breaths (Grønlund model G). In this case, Ft1 = Ft2 and thus the term VAi-1 (FAi-FAi-1) vanishes. In the present study, average alveolar O2 uptake (VO2,A) and CO2 output (VCO2,A) were equal in both approaches whereby the mean signal-to-noise ratio (S/N) was 40% larger in G. Other approaches yield steady state S/N values equal to that obtained in G, although they are based on the questionable assumption that the inter-breath variability of alveolar gas transfer is minimal. It is concluded that the only promising approach for assessing "true" single-breath alveolar gas transfer is that originally proposed by Grønlund.

Adult↗
PubMed1994

Improved method for mutagenicity testing of gaseous compounds by using a gas sampling bag.

A simple and safety gas exposure method was developed using a gas sampling bag as an exposure vessel and a preparation vessel of diluted gas. The gas exposure conditions such as amount of S9 in the plate, volume of gas for the plate, amount of top agar, exposure period and exposure temperature were examined by mutagenicity testing of 1,3-butadiene using the gas sampling bag. Mutagenicity tests of 14 compounds and 1,3-butadiene on S. typhimurium TA98, TA100, TA1535 and TA1537, and E. coli WP2 uvrA were also examined by the developed gas exposure method. 1,3-Butadiene, propyne (methyl acetylene), monochlorodifluoromethane, ethylchloride, diborane and silane were mutagenic. 1-Butene, 2-butene, 2-methylpropene, methyl vinyl ether, trichlorofluoromethane, dichlorodifluoromethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 1,1-difluoroethane and phosphine were not mutagenic on S. typhimurium TA98, TA100, TA1535 and TA1537, and E. coli WP2 uvrA with or without metabolic activation. These results were compatible with a previous report, and this developed method has the advantage that it can be tested easily and safely for combustible and self-combustible substances such as 1,3-butadiene and silane.

Animals↗
PubMedDate not supplied

Effect of pulsatile flow on gas exchange in the fish gill: theory and experimental data.

A model for gas exchange in the fish gill allowing for time-varying water and blood flow is presented. An analysis based on this mathematical model shows that pulsatile water and blood flow potentially may reduce the efficiency of gas exchange significantly. The degree of inefficiency imposed on gas exchange is, however, determined by the physical dimensions of the gill and the gas capacitance coefficients of water and blood. Using anatomical and physiological data it is shown to be likely that for a large group of fishes, including the salmonids, pulsatility of water and blood flow affects gas exchange efficiency only marginally. A close coupling between cardiac and respiratory rhythms is therefore only of marginal advantage to gas exchange efficiency. Due to their exceptional gill dimensions tunas, and to a lesser extent mackerels, are susceptible to the negative effect of pulsatility on gas exchange, which may be one of the factors favouring ram ventilation in these species.

Animals↗
PubMed1988

Gas exchange at a given degree of volume restriction is different in sarcoidosis and idiopathic pulmonary fibrosis.

PURPOSE: It is likely that the relationship between lung volume changes and gas exchange in patients with idiopathic pulmonary fibrosis (IPF) and patients with sarcoidosis is different since the two conditions vary widely in histopathology and prognosis. Few studies, however, have examined this relationship. The goal of this investigation was to measure diffusing capacity and gas exchange in patients with IPF and sarcoidosis in whom the reduction of lung volume was equivalent. PATIENTS AND METHODS: In 21 patients with IPF and 20 patients with pulmonary sarcoidosis with comparable reductions in lung volume, the single breath diffusing capacity for carbon monoxide and gas exchange at rest and during exercise were compared. RESULTS: The relationship between lung volume and gas transfer differed in the two groups of patients. Resting and exercise gas exchange tended to be relatively normal and the diffusing capacity was higher in patients with sarcoidosis than in those with IPF. These differences could not be attributed to disparities in race, age, smoking habits, or the radiographic stage of sarcoidosis. CONCLUSION: The preservation of gas exchange in sarcoidosis as opposed to IPF, despite equivalent degrees of volume restriction, suggests that different pathophysiologic mechanism underlie the volume loss and gas exchange defects seen in these disorders. Furthermore, these findings suggest that diffusing capacity may not be a sensitive indicator of pulmonary pathology in sarcoidosis since lung volume can be altered independently of abnormalities in the diffusing capacity.

Adult↗