Tracheal Pressure Measurements Research Articles

Continuous Telemetric In Utero Tracheal Pressure Measurements in Fetal Lambs.

Normal in utero lung development and growth rely upon the expansion of airspaces and the controlled efflux of lung liquid into the amniotic space. Infants with congenital diaphragmatic hernia (CDH) also have lung hypoplasia due to occupation of the chest cavity by the stomach and bowel and, in the most severe cases, the liver. Balloon tracheal occlusion reduces the severity of lung hypoplasia in fetuses with CDH but increases the risk of premature birth. Understanding the optimal occlusion pressure and duration required to improve lung hypoplasia with tracheal occlusion is essential to improving in utero corrective treatments for CDH. The study reports a new method for continuous measurement of the intratracheal and amniotic pressures in an unoccluded and occluded fetal lamb surgical model of CDH. Time-pregnant Merino ewes underwent two recovery hysterotomies: the first at ~80 days of gestation to create the CDH, and the second at ~101 days of gestation to occlude the fetal trachea and implant an intratracheal and amniotic pressure measurement device. Lambs were delivered at ~142 days, and the pressure measurement device was removed and cleaned. The data were downloaded and filtered using a 6 h window. Transrespiratory pressure was calculated.

Measurement of tracheal tube cuff pressure and the incidence of postoperative sore throat

Measurement of tracheal tube cuff pressure and the incidence of postoperative sore throat

Tracheo-oesophageal fistula - A disastrous complication of endotracheal intubation!

A 28-year old man required invasive mechanical ventilation in view of organophosphorus poisoning in a peripheral hospital. His trachea was extubated ten days later following which he presented with dysphagia, voice change, burping, fever and cough. He was referred to our hospital for further management. His barium swallow radiograph showed a large tracheo-oesophageal fistula. Therefore, he was scheduled for oesophageal transection and colonic transposition. Following induction of anaesthesia, despite easy laryngoscopy view (Cormack Lehane grade 1), the tracheal intubation was found to be difficult as the tube tended to pass through the fistula into the oesophagus repeatedly as confirmed by absence of capnogram trace. Attempts to bypass the fistula using a fibreoptic scope and even a double lumen tube also failed. Identification of oesophageal intubation would have been missed or possibly detected late in this case with disastrous consequences but for absence of capnogram. Finally, the tracheal tube was successfully negotiated beyond the fistula with the help of a gum elastic bougie directed anteriorly into the trachea and a good capnogram was obtained. The surgery was uneventful and the trachea was extubated 24 h later in the intensive care unit following which the patient developed stridor requiring permanent tracheostomy. This case report illustrates the novel use for gum elastic bougie during tracheal intubation. This also highlights the importance of repeated measurement of tracheal cuff pressure in patients especially those receiving long duration mechanical ventilation.

Individualised flow-controlled ventilation versus pressure-controlled ventilation in a porcine model of thoracic surgery requiring one-lung ventilation: A laboratory study.

Flow-controlled ventilation (FCV) enables precise determination of dynamic compliance due to a continuous flow coupled with direct tracheal pressure measurement. Thus, pressure settings can be adjusted accordingly in an individualised approach. The aim of this study was to compare gas exchange of individualised FCV to pressure-controlled ventilation (PCV) in a porcine model of simulated thoracic surgery requiring one-lung ventilation (OLV). Controlled interventional trial conducted on 16 domestic pigs. Animal operating facility at the Medical University of Innsbruck. Thoracic surgery was simulated with left-sided thoracotomy and subsequent collapse of the lung over a period of three hours. When using FCV, ventilation was performed with compliance-guided pressure settings. When using PCV, end-expiratory pressure was adapted to achieve best compliance with peak pressure adjusted to achieve a tidal volume of 6 ml kg -1 during OLV. Gas exchange was assessed by the Horowitz index (= P aO 2 /FIO 2 ) and CO 2 removal by the P aCO 2 value in relation to required respiratory minute volume. In the FCV group ( n = 8) normocapnia could be maintained throughout the OLV trial despite a significantly lower respiratory minute volume compared to the PCV group ( n = 8) (8.0 vs. 11.6, 95% confidence interval, CI -4.5 to -2.7 l min -1 ; P < 0.001), whereas permissive hypercapnia had to be accepted in PCV ( P aCO 2 5.68 vs. 6.89, 95% CI -1.7 to -0.7 kPa; P < 0.001). The Horowitz index was comparable in both groups but calculated mechanical power was significantly lower in FCV (7.5 vs. 22.0, 95% CI -17.2 to -11.8 J min -1 ; P < 0.001). In this porcine study FCV maintained normocapnia during OLV, whereas permissive hypercapnia had to be accepted in PCV despite a substantially higher minute volume. Reducing exposure of the lungs to mechanical power applied by the ventilator in FCV offers a possible advantage for this mode of ventilation in terms of lung protection.

A comparison of endotracheal tube compensation techniques for the measurement of respiratory mechanical impedance at low frequencies.

Measurement of respiratory impedance ([Formula: see text]) in intubated patients requires accurate compensation for pressure losses across the endotracheal tube (ETT). In this study, we compared time-domain (TD), frequency-domain (FD) and combined time-/frequency-domain (FT) methods for ETT compensation. We measured total impedance ([Formula: see text]) of a test lung in series with three different ETT sizes, as well as in three intubated porcine subjects. Pressure measurement at the distal end of the ETT was used to determine the true [Formula: see text]. For TD compensation, pressure distal to the ETT was obtained based on its resistive and inertial properties, and the corresponding [Formula: see text] was estimated. For FD compensation, impedance of the isolated ETT was obtained from oscillatory flow and pressure waveforms, and then subtracted from [Formula: see text]. For TF compensation, the nonlinear resistive properties of the ETT were subtracted from the proximal pressure measurement, from which the linear resistive and inertial ETT properties were removed in the frequency-domain to obtain [Formula: see text]. The relative root mean square error between the actual and estimated [Formula: see text] ([Formula: see text]) showed that TD compensation yielded the least accurate estimates of [Formula: see text] for the in vitro experiments, with small deviations observed at higher frequencies. The FD and TF compensations yielded estimates of [Formula: see text] with similar accuracies. For the porcine subjects, no significant differences were observed in [Formula: see text] across compensation methods. FD and TF compensation of the ETT may allow for accurate oscillometric estimates of [Formula: see text] in intubated subjects, while avoiding the difficulties associated with direct tracheal pressure measurement.

Horses are Obligate Nasal Breathers: But does this Obligation Still Apply when a Horses ‘Nasopharyngeal Air Supply’ and with this its ‘Defence through Flight’, is Compromised

It had been suggested that obligate nasal breathing had evolved to enhance a horses ability to detect predator scents whilst grazing. The singular opening of the vomeronasal organ into the nasal cavity had certainly developed in a manner that supported this form of breathing and thence theory. A horses ability to carry feed in its mouth, without this being drawn into the airway during flight, was another theory put forward to explain this obligation. The horse as a species is heavily reliant on flight as a means of defence and thence survival. Any reduction in nasopharyngeal patency would logically compromise a horses ability to maintain acceleration and thence its ability to evade a predator. The likelihood that a horse would elect to supplement a compromised nasal air supply with orally inspired air whilst fleeing a predator, seemed logical. Nasopharyngeal and upper tracheal intraluminal pressure measurements recorded during periods of intermittent dorsal displacement of the soft and experimentally induced palatal instability indicated that air was being acquired orally in these situations. Keywords: Palatal instability, mouth breathing, oropharyngeal seal, palatal instability, dorsal displacement of the soft palate. Read more →

Individualized flow-controlled ventilation compared to best clinical practice pressure-controlled ventilation: a prospective randomized porcine study

BackgroundFlow-controlled ventilation is a novel ventilation method which allows to individualize ventilation according to dynamic lung mechanic limits based on direct tracheal pressure measurement at a stable constant gas flow during inspiration and expiration. The aim of this porcine study was to compare individualized flow-controlled ventilation (FCV) and current guideline-conform pressure-controlled ventilation (PCV) in long-term ventilation.MethodsAnesthetized pigs were ventilated with either FCV or PCV over a period of 10 h with a fixed FiO2 of 0.3. FCV settings were individualized by compliance-guided positive end-expiratory pressure (PEEP) and peak pressure (Ppeak) titration. Flow was adjusted to maintain normocapnia and the inspiration to expiration ratio (I:E ratio) was set at 1:1. PCV was performed with a PEEP of 5 cm H2O and Ppeak was set to achieve a tidal volume (VT) of 7 ml/kg. The respiratory rate was adjusted to maintain normocapnia and the I:E ratio was set at 1:1.5. Repeated measurements during observation period were assessed by linear mixed-effects model.ResultsIn FCV (n = 6), respiratory minute volume was significantly reduced (6.0 vs 12.7, MD − 6.8 (− 8.2 to − 5.4) l/min; p < 0.001) as compared to PCV (n = 6). Oxygenation was improved in the FCV group (paO2 119.8 vs 96.6, MD 23.2 (9.0 to 37.5) Torr; 15.97 vs 12.87, MD 3.10 (1.19 to 5.00) kPa; p = 0.010) and CO2 removal was more efficient (paCO2 40.1 vs 44.9, MD − 4.7 (− 7.4 to − 2.0) Torr; 5.35 vs 5.98, MD − 0.63 (− 0.99 to − 0.27) kPa; p = 0.006). Ppeak and driving pressure were comparable in both groups, whereas PEEP was significantly lower in FCV (p = 0.002). Computed tomography revealed a significant reduction in non-aerated lung tissue in individualized FCV (p = 0.026) and no significant difference in overdistended lung tissue, although a significantly higher VT was applied (8.2 vs 7.6, MD 0.7 (0.2 to 1.2) ml/kg; p = 0.025).ConclusionOur long-term ventilation study demonstrates the applicability of a compliance-guided individualization of FCV settings, which resulted in significantly improved gas exchange and lung tissue aeration without signs of overinflation as compared to best clinical practice PCV.

A bitless bridle does not limit or prevent dynamic laryngeal collapse.

Bits have often been incriminated as a cause of upper respiratory tract obstruction in horses; however, no scientific studies are available to confirm or refute these allegations. Clinical signs of dynamic laryngeal collapse associated with poll flexion (DLC) are induced when susceptible horses are ridden or driven into the bit. To determine whether use of Dr Cook's™ Bitless Bridle, instead of a conventional snaffle bit bridle, would reduce the severity of DLC in affected horses measured objectively using inspiratory tracheal pressures. Intervention study using each horse as its own control in a block randomised order. Nine Norwegian Swedish Coldblooded trotters previously diagnosed with DLC were exercised on two consecutive days using a standardised high-speed treadmill protocol with either a conventional bridle with a snaffle bit, or Dr Cook's™ Bitless Bridle. Head and neck position, rein tension, inspiratory tracheal pressure measurements, and laryngeal videoendoscopy recordings were obtained. A heart rate greater than 200bpm, and similar degrees of poll flexion/head height, had to be achieved in both bridles for the individual horse's data to be included for comparison. Seven horses' data met the inclusion criteria. The change in mean inspiratory tracheal pressure between free and flexion phases in the bitless bridle (-15.2±12.3cmH2 O) was significantly greater (P<.001) than in the snaffle bit bridle (-9.8±7.9cmH2 O). Mean inspiratory pressure during the free phase was significantly (P<.001) more negative with the snaffle bit bridle (-32.3±6.3cmH2 O), vs the bitless bridle (-28.5±6.9cmH2 O). Mean pressures in flexion phase, snaffle bridle (-42.1±10.8cmH2 O), vs bitless bridle (-43.7±15.6cmH2 O) where not significantly different between bridles (P=.2). Small sample size due to difficulty recruiting suitable clinical cases. This study could not provide any clear evidence that the effect of a snaffle bit in a horse's mouth influences the development or severity of DLC. Instead, head and neck angles induced by rein tension seem to be the key event in provoking DLC in susceptible horses.

Comparison of tracheal tube cuff pressure with two technique: fixed volume and minimal leak test techniques.

Introduction: There is a correlation between endotracheal cuff pressure and airway complication; therefore, cuff pressure measurement is of an essential importance. The gold standard technique is measuring the cuff pressure by a calibrated manometer. However, there are several methods that injects air into balloon pilot and measures the cuff pressure. The aim of this study is to compare the tracheal cuff pressure measurement by two methods: fixed volume and minimal leak test (MLT). Methods: This descriptive study was performed at the emergency department on 110 patients. Patients were randomized into two groups. For one group, fixed volume technique and for the other group MLT was used. Results: Mean cuff pressure was 46.07±23.54 cmH2O in the fixed volume group and 33.72±9.14 cmH2O in the MLT group (P=0.05) which is significantly higher in the fixed volume group (P=0.028). In addition, 56.4% and 78.2% of the subjects had normal cuff pressure in the fixed volume group and MLT group, respectively; indicating a significantly higher rate in MLT group (P=0.025). Conclusion: Both techniques cause above normal intracuff pressure; however, MLT produces more acceptable pressure than fixed volume. It seems that the volume of 10 cc produces high pressures; therefore, fixed values may yield more appropriate results in lower volumes.

An In Vitro Study to Assess Determinant Features Associated With Fluid Sealing in the Design of Endotracheal Tube Cuffs and Exerted Tracheal Pressures*

To assess the structural characteristics involved in the design of high-volume low-pressure endotracheal tube cuffs that are associated with fluid sealing effectiveness and to determine the extent of transmitted tracheal pressures upon cuff inflation. In vitro study. Pneumology laboratories. Eight high-volume low-pressure cuffs of cylindrical or tapered shape, made of polyvinylchloride or polyurethane, were studied. Cuffs were tested within a tracheal model, oriented 30° above horizontal to assess 1 hr leakage of oropharyngeal secretions simulant at cuff internal pressures of 15-30 cm H2O. The four best performing cuffs were evaluated for 24 hrs using an internal pressure of 30 cm H2O. The extent of transmitted tracheal wall pressure throughout the cuff-trachea contact area was determined using an internal pressure sensor within a tracheal model upon cuff inflation up to 30 cm H2O. Outer diameter, length, and compliance of each cuff were assessed. Multivariate regression analysis was performed to identify the main determinants of simulant leakage rate. The cuff-trachea contact area and the percentage of tracheal wall pressure measurements greater than 50 cm H2O were computed. Cuff design characteristics significantly differ among tubes. The cuffs made of polyurethane showed the best short- and long-term sealing efficacy. Nevertheless, in the multivariate analysis, the cuff outer diameter (n: 288, p = 0.003) and length (n: 288, p < 0.001), along with the internal pressure (n: 288, p < 0.001), were the only predictors of simulant leakage rate. The tapered cuffs showed the lowest tracheal wall contact area (n: 96, p < 0.001). The tracheal wall pressure distribution pattern was heterogeneous, and the percentage of high tracheal wall pressure significantly differs among the cuffs (n: 96, p < 0.001). The high-volume low-pressure cuffs' outer diameter, length, material, and internal pressure are the main determinants of sealing efficacy. Despite internal pressure within the safe range, transmitted tracheal pressure is extremely heterogeneous and differs among cuffs, occasionally reaching localized, very high, unsafe levels.

Patients with cardiac arrest are ventilated two times faster than guidelines recommend: An observational prehospital study using tracheal pressure measurement

AimTo measure ventilation rate using tracheal airway pressures in prehospitally intubated patients with and without cardiac arrest. MethodsProspective observational study. In 98 patients (57 with and 41 without cardiac arrest) an air-filled catheter was inserted into the endotracheal tube and connected to a custom-made portable device allowing tracheal airway pressure recording and subsequent calculation of ventilation rate. ResultsIn manually ventilated patients with cardiac arrest 39/43 (90%) had median ventilation rates higher than 10/min (overall median 20, min 4, max 74). During mechanical ventilation, 35/38 (92%) had ventilation rates higher than 10/min. The ventilation rate in patients with cardiac arrest was higher than in patients without cardiac arrest, both for manual and mechanical ventilation. Subanalysis comparing episodes with and without compression in cardiac arrest patients showed no clinically significant difference in ventilation rate after compressions were terminated. ConclusionCardiac arrest patients were ventilated two times faster than recommended by the guidelines. Tracheal airway pressure measurement is feasible during resuscitation and may be developed further to provide real-time feedback on airway pressure and ventilation rate during resuscitation.

Compensating for Endotracheal Tube Resistance

To the Editor: Uchiyama et al.1 presented a method to compensate for endotracheal tube (ETT) resistance during spontaneous exhalation. The authors confirm that expiratory ETT compensation can prevent dynamic hyperinflation as we have recently demonstrated during controlled mechanical ventilation2 using automatic tube compensation (ATC).3 We have several concerns with their approach. Exhalation is not entirely passive during spontaneous breathing as with mechanical ventilation. As a result, the flow/time and volume/time curves do not share the same exponential character of the exhalation during mechanical ventilation as assumed by Uchiyama et al. Application of a power function-shaped flow during spontaneous exhalation results in overcompensation at the beginning and undercompensation at the end of exhalation. Furthermore, in the tracheally intubated patient, direct measurement of tracheal pressure would be required to exclude generation of negative intratracheal pressure during the described technique. ATC, introduced in 1994, was developed to fully compensate for the flow-dependent ETT resistance during inspiration and exhalation independent of ETT size.4 From a methodological point of view, there is a considerable difference between ATC and the approach by Uchiyama et al. In the latter approach, a fixed volume is aspirated during exhalation, which may cause negative tracheal pressure and, consequently, atelectasis. In contrast, the ATC control algorithm calculates the actual flow-dependent pressure decrease across the ETT to compensate for ETT resistance by a real-time feedback controller. Thus, negative tracheal pressure can never occur because the degree of compensation is directly related to flow, which automatically approximates 0 at the end of each breathing phase and changes direction with the leading sign of the pressure difference between the proximal and distal end of the ETT. Taken together, the statement by Uchiyama et al. that the “[ATC] prototype ventilator was developed to assist spontaneous breathing through an ordinary-sized ETT” and, therefore, “was inadequate for mechanical ventilation using a smaller-sized ETT” is not justified because appropriate compensation fully counteracts the resistance of ETT independent of its size. Stefan Schumann, PhD Division for Experimental Anesthesiology University Medical Center of Freiburg Freiburg, Germany [email protected] Christoph Haberthuer, MD Intensive Care Unit Department of Anesthesiology Kantonsspital Lucerne, Switzerland Josef Guttmann, PhD Division for Experimental Anesthesiology University Medical Center of Freiburg Freiburg, Germany

Role of the hypoglossal nerve in equine nasopharyngeal stability

The equine upper airway is highly adapted to provide the extremely high oxygen demand associated with strenuous aerobic exercise in this species. The tongue musculature, innervated by the hypoglossal nerve, plays an important role in airway stability in humans who also have a highly adapted upper airway to allow speech. The role of the hypoglossal nerve in stabilizing the equine upper airway has not been established. Isolated tongues from eight mature horses were dissected to determine the distal anatomy and branching of the equine hypoglossal nerve. Using this information, a peripheral nerve location technique was used to perform bilateral block of the common trunk of the hypoglossal nerve in 10 horses. Each horse was subjected to two trials with bilateral hypoglossal nerve block and two control trials (unblocked). Upper airway stability at exercise was determined using videoendoscopy and measurement of tracheal and pharyngeal pressure. Three main nerve branches were identified, medial and lateral branches and a discrete branch that innervated the geniohyoid muscle alone. Bilateral hypoglossal block induced nasopharyngeal instability in 10/19 trials, and none of the control trials (0/18) resulted in instability (P<0.001). Mean treadmill speed (+/-SD) at the onset of instability was 10.8+/-2.5 m/s. Following its onset, nasopharyngeal instability persisted until the end of the treadmill test. This instability, induced by hypoglossal nerve block, produced an expiratory obstruction similar to that seen in a naturally occurring equine disease (dorsal displacement of the soft palate, DDSP) with reduced inspiratory and expiratory pharyngeal pressure and increased expiratory tracheal pressure. These data suggest that stability of the equine upper airway at exercise may be mediated through the hypoglossal nerve. Naturally occurring DDSP in the horse shares a number of anatomic similarities with obstructive sleep apnea. Study of species with extreme respiratory adaptation, such as the horse, may provide insight into respiratory functioning in humans.

The nucleus retroambiguus control of respiration.

The role of the nucleus retroambiguus (NRA) in the context of respiration control has been subject of debate for considerable time. To solve this problem, we chemically (using d, l-homocysteic acid) stimulated the NRA in unanesthetized precollicularly decerebrated cats and studied the respiratory effect via simultaneous measurement of tracheal pressure and electromyograms of diaphragm, internal intercostal (IIC), cricothyroid (CT), and external oblique abdominal (EO) muscles. NRA-stimulation 0-1 mm caudal to the obex resulted in recruitment of IIC muscle and reduction in respiratory frequency. NRA-stimulation 1-3 mm caudal to the obex produced vocalization along with CT activation and slight increase in tracheal pressure, but no change in respiratory frequency. NRA-stimulation 3-5 mm caudal to the obex produced CT muscle activation and an increase in respiratory frequency, but no vocalization. NRA-stimulation 5-8 mm caudal to the obex produced EO muscle activation and reduction in respiratory frequency. A change to the inspiratory effort was never observed, regardless of which NRA part was stimulated. The results demonstrate that NRA does not control eupneic inspiration but consists of topographically separate groups of premotor interneurons each producing detailed motor actions. These motor activities have in common that they require changes to eupneic breathing. Different combination of activation of these premotor neurons determines the final outcome, e.g., vocalization, vomiting, coughing, sneezing, mating posture, or child delivery. Higher brainstem regions such as the midbrain periaqueductal gray (PAG) decides which combination of NRA neurons are excited. In simple terms, the NRA is the piano, the PAG one of the piano players.

D1/D2-dopamine receptor agonist dihydrexidine stimulates inspiratory motor output and depresses medullary expiratory neurons

It is now accepted that dopamine plays an important neuromodulatory role in the central nervous control of respiration. D1, D2, and D4 subtypes of the receptor seem to be important players, but the assignment of various respiratory tasks to specific subtypes of the dopamine receptor is a work in progress. In the present investigation, dihydrexidine (DHD), a full dopamine receptor agonist with affinity for both D1- and D2-subtypes of receptor, was tested for its effects on inspiratory neurons and motor output and on membrane potential properties of medullary bulbospinal expiratory augmenting expiratory neurons in the pentobarbital anesthetized adult cat. The effects of DHD were compared with those of the highly selective D1-dopamine receptor (D1R) agonists SKF-38393 and 6-chloro-APB. DHD increased the intensity and duration of inspiratory motor output. Phrenic nerve discharge intensity was increased and prolonged, contributing to elevated inspiratory effort and duration when spontaneous breathing was monitored with tracheal pressure measurements. Intracellular recording from rostral medullary inspiratory neurons revealed that DHD, like SKF-38393, increases and prolongs inspiratory phase membrane depolarization, resulting in a longer and more intense discharge of action potentials. Remarkably, DHD had opposite effects on Aug-E neurons. Membrane potential was hyperpolarized, and action potential discharges were suppressed or abolished. In association with reduction of discharge intensity, action potential half width was reduced and after-hyperpolarization increased. The stimulatory action of DHD on inspiratory motor output is attributed to D1R effects, while the depression of Aug-E neurons seems to be linked to D2R actions on the postsynaptic membrane.

Effect of poll flexion and dynamic laryngeal collapse on tracheal pressure in Norwegian Coldblooded Trotter racehorses

Dynamic laryngeal collapse (DLC) associated with poll flexion is a newly diagnosed upper respiratory tract obstructive disorder that causes poor racing performance. To determine if Norwegian Coldblooded Trotters (NCTs) affected with DLC associated with poll flexion differ from normal, elite NCTs based on simple airway mechanics measurements. Five normal elite NCTs and 6 NCTs diagnosed previously with DLC underwent treadmill videoendoscopy while tracheal pressures were measured continuously. Alternating head positions were used such that horses were exercised with free head carriage and induced poll flexion at heart rates >200 beats/min. Peak inspiratory tracheal pressures were significantly more negative for horses with DLC compared to the elite horses. This difference was only significant during the exercise phases when the poll region was flexed, P = 0.0015. Head position significantly affected peak inspiratory pressure for both elite and affected horses, P < 0.0001. Induced poll flexion significantly affected peak inspiratory pressure (PIP) in all horses; however, PIPs were significantly more negative in those affected with DLC. Based upon the tracheal pressure measurements recorded in this study, DLC in NCTs is a severe obstructive upper respiratory tract disorder that is induced by poll flexion.

Oesophageal function in tracheoesophageal fistula speakers after laryngectomy

Patients who have undergone tracheoesophageal puncture for surgical voice restoration often use unnaturally high oesophageal air pressures during speech. This study examined the effect of high oesophageal air pressure on oesophageal body motility, lower oesophageal sphincter function and dyspeptic symptoms. Cross-sectional study using several investigative tests of oesophageal function. Sixteen patients who used tracheoesophageal fistula speech underwent several investigations, including: oesophageal manometry, videofluoroscopy, barium swallow, and tracheal pressure measurements during speech. The patients were also asked to complete a dyspepsia questionnaire. We demonstrated that more than 50 per cent of these patients had subjective or objective disordered oesophageal function. Videofluoroscopy and manometry identified oesophageal dysmotility in the same patients. Oesophageal function appears to be altered by tracheoesophageal fistula speech. However, our study showed that there is no contraindication to proceeding with tracheoesophageal fistula voicing even in patients with a history of oesophageal dysfunction.

Measurement of tracheal wall pressure: a comparison of three different in vitro techniques

We compared three different tracheal wall pressure measuring techniques in vitro. Using a high-volume, low-pressure, cuffed tracheal tube with an internal diameter of 7.5 mm and a model trachea, the pressure difference technique, the wall pressure membrane technique and the microchip sensor probe technique with and without lubrication were studied. Wall pressures were measured after sequential injections of 0.5 ml of air into the cuff at cuff pressures ranging from 0 to 50 mmHg. The coefficient of variance was largest for the microchip sensor probe technique with lubrication (29%) and without lubrication (214%), and was lower for the wall pressure membrane technique (22%) and the pressure difference technique (19%). The wall pressure membrane and pressure difference techniques provided comparable results. The microchip sensor probe technique considerably underestimated wall pressure. These findings have an impact on the interpretation of published data on tracheal or pharyngeal wall pressure using the microchip sensor probe technique.

A Key Role for CC Chemokine Receptor 1 in T-Cell-Mediated Respiratory Inflammation

CC chemokine receptor 1 (CCR1) is found on a variety of cells in the immune system and has been shown to play an important role in the host response to pathogens. These studies used a murine model of virus-induced exacerbation of allergic airway disease to examine the role of CCR1 on T cells associated with immune responses taking place in the lung. Lungs of virally exacerbated allergic animals contained elevated levels of interferon-gamma and interleukin-13 and increased levels of CCR1 ligands CCL3 and CCL5. CCR1 expression on T cells was increased in virally exacerbated allergic animals over the level observed in mice sensitized to allergen or exposed to viral infection alone. Using mice deficient for CCR1, we observed decreased airway hyperreactivity and Th2 cytokine production from CD4(+) T cells when this receptor was absent. Transfer studies demonstrated that neither CD4(+) nor CD8(+) T cells from CCR1(-/-) mice migrated to the lymph node as efficiently as wild-type T cells. Intracellular cytokine staining in wild-type mice revealed that CCR1(+) CD4(+) and CD8(+) T cells are associated with interleukin-13 production. Thus, these studies identify CCR1 as a potential target for alleviating T-cell accumulation during exacerbation of asthmatic disease.

Detection of tracheal malpositioning of nasogastric tubes using endotracheal cuff pressure measurement

Insertion of a gastric tube (GT) in anaesthetized, paralyzed and intubated patients may be difficult. Tracheobronchial malposition of a GT may result in deleterious consequences. The purpose of this study was to determine the reliability of tracheal cuff pressure measurement to detect endobronchial malposition of GTs. We compared this new method with the measurement of exhaled CO(2) through the GT. Thirty patients under general anesthesia and orotracheal intubation were analysed. First, the cuff pressure of the low-volume endotracheal tube (ET; ID 7.0-8.5 mm) was increased to 40 cmH(2)O. Then, in a randomized fashion, the GT (18 Charrière) was inserted consecutively into the trachea and oesophagus or vice versa. Cuff pressure was monitored continuously while advancing the GT. Furthermore, a capnograph was connected to the gastric tube and the aspirated PCO(2) was monitored. Advancement of the gastric tube into the oesophagus increased ET cuff pressure by 1 +/- 1 cmH(2)O, while endotracheal placement of the GT increased cuff pressure by 28 +/- 8 cmH(2)O (P < 0.001). Using an increase of >10 cmH(2)O in cuff pressure detected endotracheal malpositioning of the GT with 100% sensitivity and specificity. In 28 out of 30 cases, PCO(2) increased by more than 2.6 kPa. Thus, the PCO(2) approach failed to detect tracheal malpositioning in two cases resulting in a sensitivity of 93.3%. In intubated patients, cuff pressure measurement during insertion of a gastric tube is a new, simple and reliable bedside method to detect endotracheal malpositioning of a GT.