T-piece System Research Articles

Effective ventilation and chest compressions during neonatal resuscitation – the role of the respiratory device

Background The success of cardiopulmonary resuscitation (CPR) in newborns largely depends on effective lung ventilation; however, a direct randomized comparison using different available devices has not yet been performed. Methods Thirty-six professionals were exposed to a realistic newborn CPR scenario. Ventilation with either a bag-valve mask (BVM), T-piece, or ventilator was applied in a randomized manner during CPR using a Laerdal manikin. The primary outcome was the number of unimpaired inflations, defined as the peak of the inflation occurring after chest compression and lasting at least 0.35 s before the following chest compression takes place. The secondary outcomes were tidal volume delivered and heart compression rate. To simulate potential distractions, the entire scenario was performed with or without a quiz. Statistically, a mixed model assessing fixed effects for experience, profession, device, and distraction was used to analyze the data. For direct comparison, one-way ANOVA with Bonferroni‘s correction was applied. Results The number of unimpaired inflations was highest in health care professionals using the BVM with a mean ± standard deviation of 12.8 ± 2.8 (target: 15 within 30 s). However, the tidal volumes were too large in this group with a tidal volume of 42.5 ± 10.9 ml (target: 25–30 ml). The number of unimpaired breaths with the mechanical ventilator and the T-piece system were 11.6 (±3.6) and 10.1 (±3.7), respectively. Distraction did not change these outcomes, except for the significantly lower tidal volumes with the T-piece during the quiz. Conclusions In summary, for our health care professionals, ventilation using the mechanical ventilator seemed to provide the best approach during CPR, especially in a population of preterm infants prone to volutrauma.

The effect of imposed resistance in neonatal resuscitators on pressure stability and peak flows: a bench test.

The importance of neonatal resuscitator resistance is currently unknown. In this study we investigated peak flows and pressure stability resulting from differences in imposed resistance during positive pressure ventilation(PPV) and simulated spontaneous breathing (SSB) between the r-PAP, low-resistance resuscitator, and Neopuff™, high-resistance resuscitator. In a bench test, 20 inflations during PPV and 20 breaths during SSB were analysed on breath-by-breath basis to determine peak flow and pressure stability using the Neopuff™ with bias gas flow of 8, 12 or 15 L/min and the r-PAP with total gas flow of 15 L/min. Imposed resistance of the Neopuff™ was significantly reduced when the bias gas flow was increased from 8 to 15 L/min, which resulted in higher peak flows during PPV and SSB. Peak flows in the r-PAP were, however, significantly higher and fluctuations in CPAP during SSB were significantly smaller in the r-PAP compared to the Neopuff™ for all bias gas flow levels. During PPV, a pressure overshoot of 3.2 cmH2O was observed in the r-PAP. The r-PAP seemed to have a lower resistance than the Neopuff™ even when bias gas flows were increased. This resulted in more stable CPAP pressures with higher peak flows when using the r-PAP. The traditional T-piece system (Neopuff™) has a higher imposed resistance compared to a new neonatal resuscitator (r-PAP). This study shows that reducing imposed resistance leads to smaller CPAP fluctuations and higher inspiratory and expiratory peak flows. High peak flows might negatively affect lung function and/or cause lung injury in preterm infants at birth. This study will form the rationale for further studies investigating these effects. A possible compromise might be to use the traditional T-piece system with a higher bias gas flow (12 L/min), thereby reducing the imposed resistance and generating more stable PEEP/CPAP pressures, while limiting potentially harmful peak flows.

Transition of Extremely Preterm Infants from Birth to Stable Breathing: A Secondary Analysis of the CORSAD Trial

Objective: Exploratory secondary analysis of the CORSAD trial compared a new resuscitation system (rPAP) to the standard T-piece system. This analysis focused on the subgroup of infants who were not intubated in the delivery room. The aim was to compare the use of noninvasive positive pressure ventilation (PPV), oxygen saturation, and Apgar scores for the two resuscitation systems during the 30-min intervention period. Methods: This is secondary analysis of CORSAD trial using data from the intervention period in the delivery room. Infants in the original randomized system groups were divided into intubated and nonintubated groups. For nonintubated breathing infants, we compared demographics, the use of PPV, Apgar scores, and oxygen saturation at 5 and 10 min after birth. Generalized linear models were applied to calculate the risk difference and odds ratio with 95% CI between the two groups. Results: Among nonintubated infants, the use of PPV repeatedly (defined as PPV with at least 1 min of spontaneous breathing between PPV cycles) was less frequent in the rPAP group (26.8% vs. 43.3%, %RD −16.5, 95% CI [−31.7 to −1.1], p 0.04). The use of PPV after 5 min of age was also less common in the rPAP group (23.2% vs. 38.8%, %RD −15.6, 95% CI [−30.7 to −0.8], p 0.04). There were no statistically significant differences in Apgar scores or oxygen saturation levels between the groups. Conclusion: In the CORSAD trial, less PPV was needed to establish stable breathing in extremely preterm infants using the rPAP compared to using the standard T-piece without significant difference in Apgar scores or oxygenation.

Comparison of Respiratory Support After Delivery in Infants Born Before 28 Weeks’ Gestational Age

Establishing stable breathing is a key event for preterm infants after birth. Delivery of pressure-stable continuous positive airway pressure and avoiding face mask use could be of importance in the delivery room. To determine whether using a new respiratory support system with low imposed work of breathing and short binasal prongs decreases delivery room intubations or death compared with a standard T-piece system with a face mask. In this unblinded randomized clinical trial, mothers threatening preterm delivery before week 28 of gestation were screened. A total of 365 mothers were enrolled, and 250 infants were randomized before birth and 246 liveborn infants were treated. The trial was conducted in 7 neonatal intensive care units in 5 European countries from March 2016 to May 2020. The follow-up period was 72 hours after intervention. Infants were randomized to either the new respiratory support system with short binasal prongs (n = 124 infants) or the standard T-piece system with face mask (n = 122 infants). The intervention was providing continuous positive airway pressure for 10 to 30 minutes and positive pressure ventilation, if needed, with the randomized system. The primary outcome was delivery room intubation or death within 30 minutes of birth. Secondary outcomes included respiratory and safety variables. Of 246 liveborn infants treated, the mean (SD) gestational age was 25.9 (1.3) weeks, and 127 (51.6%) were female. A total of 41 infants (33.1%) receiving the new respiratory support system were intubated or died in the delivery room compared with 55 infants (45.1%) receiving standard care. The adjusted odds ratio was statistically significant after adjusting for stratification variables (adjusted odds ratio, 0.53; 95% CI, 0.30-0.94; P = .03). No significant differences were seen in secondary outcomes or safety variables. In this study, using the new respiratory support system reduced delivery room intubation in extremely preterm infants. Stabilizing preterm infants with a system that has low imposed work of breathing and binasal prongs as interface is safe and feasible. ClinicalTrials.gov Identifier: NCT02563717.

Comparing the Quality of Cardiopulmonary Resuscitation Performed at the Over-the-Head Position and Lateral Position of Neonatal Manikin.

Background: Recent neonatal resuscitation guidelines suggest to perform chest compression (CC) at over-the-head (OTH) position instead of lateral position when further interventions including umbilical venous access are needed. Little information is available regarding the quality of cardiopulmonary resuscitation at different positions. Our study compared the quality of CC and ventilation at OTH position vs. lateral position in simulated neonatal resuscitation.Methods: Thirty-nine neonatal practitioners who attended the NRP®-based Provider renewal course workshop participated this study. Laerdal QCPR infant model were used to collect the data (2-miutes continuous recording) on quality of CC and ventilation of all participants at OTH position and lateral position in randomized order, both coordinated with mask ventilation or endotracheal ventilation through a Neopuff© T-piece system. The quality of CC and ventilation were compared. Participants also reported their demographics and opinions in anonymous questionnaires after the session.Results: The quality of CC and ventilation was not different when CPR was performed at OTH position and lateral position, in both mask and endotracheal ventilation. When CPR was performed with endotracheal ventilation, there were small faster frequencies of CC and ventilation at OTH position, compared with those at lateral position (p = 0.004). Most participants (87%) liked the CC performed at OTH position and had no adverse feedback.Conclusions: Performing CC at OTH position was generally well-received in simulated resuscitation; the quality of CC and ventilation at OTH position was not significantly different from that at lateral position, irrespective of mask or endotracheal ventilation.

Tidal Volume Delivery during the Anesthetic Management of Neonates Is Variable

To describe expiratory tidal volume (VT) during routine anesthetic management of neonates at a single tertiary neonatal surgical center, as well as the proportion of VT values within the range of 4.0-8.0 mL/kg. A total of 26 neonates needing surgery under general anesthesia were studied, of whom 18 were intubated postoperatively. VT was measured continuously during normal clinical care using a dedicated neonatal respiratory function monitor (RFM), with clinicians blinded to values. VT, pressure, and cardiorespiratory variables were recorded regularly while intubated intraoperatively, during postoperative transport, and for 15 minutes after returning to the neonatal intensive care unit (NICU). In addition, paired VT values from the anesthetic machine were documented intraoperatively. A total of 2597 VT measures were recorded from 26 neonates. Intraoperative and postoperative transport expiratory VT values were highly variable compared with the NICU VT (P < .0001, Kruskal-Wallis test), with 51% of inflations outside the 4.0-8.0 mL/kg range (35% and 38% of VT >8.0 mL/kg, respectively), compared with 29% in the NICU (P < .001, χ2 test). The use of a flow-inflating bag resulted in a median (range) VT of 8.5 mL/kg (range, 5.3-11.4 mL/kg) vs 5.6 ml/kg (range, 4.3-7.9 mL/kg) using a Neopuff T-piece system (P < .0001, Mann-Whitney U test). The mean anesthetic machine expiratory VT was 3.2 mL/kg (95% CI, -4.5 to 10.8 mL/kg) above RFM. VT is highly variable during the anesthetic care of neonates, and potentially injurious VT is frequently delivered; thus, we suggest close VT monitoring using a dedicated neonatal RFM.

Evolution of apnoea test in brain death diagnostics.

The concept of brain death (BD) was initially described in 1959 and subsequently became widely accepted in the majority of countries. Nevertheless, the diagnostic guidelines for BD markedly differ, especially regarding the apnoea test (AT), a crucial element of clinical BD confirmation. The current basic guidelines recommend preoxygenation rather than disconnection from the ventilator and insertion of an oxygen insufflation catheter into the endotracheal tube. Although a properly prepared and conducted AT is relatively safe, it has to be aborted in cases of serious disturbances, such as severe cardiac arrhythmia, cardiac arrest, hypotension, hypercarbia, desaturation and tension pneumothorax. These complications may be more frequent in patients with previously existing risk factors, such as poor oxygenation, severe acidosis, hypotension and cardiac rhythm disturbances. Airway injuries can occur if the insufflation catheter is placed too deep or catheter-related obstruction of the intubation tube occurs. It is widely accepted that AT should be performed as the very last BD diagnostic procedure due to its possible lethal consequences. Reports concerning the possible pitfalls of AT and confounding situations have inspired attempts to determine the most effective and safe method of AT. The use of CPAP with oxygen supplementation is becoming highly popular. CPAP can be generated in three manners: directly by the ventilator; through the use of a CPAP valve with a reservoir; and through the use of a highly traditional T-piece system with a reservoir bag connected to distal tubing immersed in water.

G202(P) Identifying latent risks through in situ simulation training to improve patient safety

IntroductionIn situ simulation training is acknowledged as a very effective way of identifying latent risks in organisations and thus improving patient safety.1,2,3 Within Yorkshire and the Humber deanery, we have...

Comparison of Two Strategies for Surfactant Prophylaxis in Premature Infants: Preliminary Data of a Randomized Trial

Objective: The purpose of this study is to determine whether the immediate bolus strategy combined with early nasal CPAP treatment can decrease the need of subsequent invasive ventilation compared with the administration of surfactant prophylaxis at 15 minutes after birth with early nasal CPAP application. Methods: Infants born either before 28 weeks' or at 29-30 weeks' who did not receive antenatal steroids were randomized before delivery. Infants randomized to group-1 were intubated immediately after birth and administered 100 mg/kg surfactant and then initiated standard CPR as indicated. Infants randomized to the group-2 were intubated electively at 15 minutes after birth and received 100 mg/kg surfactant after resuscitation and initial stabilization. T-piece system was used during these interventions. After surfactant treatment, all infants were extubated to nCPAP. Infants possesing predefined criteria were intubated for mechanical ventilation (MV). Results: Group-1 (n=15) and group-2 (n=10) had similar demographic and clinical characteristics. In each group there was an infant who could not be extubated and another one who needed MV. Median hours on nCPAP were 10 (1-93) in group-1 and 14 (2-96) in group-2 (p=0.64). There were no significant differences between the groups with respect to mortality, hospital stay, and the secondary outcomes; pneumothorax, pulmonary hemorrhage, PDA, NEC, ROP, IVH, use of systemic postnatal corticosteroids, and oxygen requirement at postnatal 28 days of life. Conclusion: Our preliminary data, demonstrates that immediate bolus strategy of surfactant prophylaxis is not superior to administration of surfactant prophylaxis at 15 minutes after birth combined with early nasal CPAP.

A novel paediatric anaesthetic breathing system

Introduction: This paper describes a lightweight, valveless, coaxial anaesthetic breathing system which enables the convenient scavenging of exhaust/waste anaesthetic gases in theatre. It is essentially a modification of the Jackson-Rees T-piece system,[1] which utilises a specially designed reservoir bag and coaxial tubing to conduct waste anaesthetic gases to an active scavenging system sited on the anaesthetic machine. Background: In the conventional Jackson-Rees system, a length of anaesthetic tubing delivers the anaesthetic gas mixture to a T-junction sited close to the patient's mouth. A second arm of the T acts as patient connector while a third connects to a reservoir tube which conducts a mixture of fresh and expired gases to an opened tailed reservoir bag, from which the gases are vented to the operating theatre environment. Epidemiological studies suggest that exposure to these gases may adversely affect the health of theatre staff [2] and this problem has recently been the subject of a campaign by the National Association of Theatre Nurses. Successful attempts to scavenge these gases have mainly involved the introduction of an expiratory valve into the Jackson Rees system, which makes the system bulky and less convenient to use. The proposed system is shown in Figure 1. Results and Conclusions: In preliminary bench tests, a professionally made prototype of the proposed system was found to impose about the same degree of expiratory resistance as a Bain system [3] with a fully opened expiratory valve, which was considered acceptable. The system was also rated highly when assessed by a sample of consultant anaesthetists performing manual ventilation on a dummy lung. While the system's primary application will be in paediatric anaesthesia, it could also find application as an induction system for adult anaesthesia. (1) [ Diagram of proposed breathing system. The inner tube arrangement is similar to that of a conventional Jackson-Rees T-piece system (4,2,5). However, in place of the open-tailed reservoir bag of the latter, the new system has a custom made bag (6) which incorporates an outer tube (8) to collect the waste anaesthetic gases via a vent situated between the outer tube and the tail section of the reservoir bag (9). This tube conducts the waste gases into the annular space between the tubes 4, 5 and 10, 11, from where they are ultimately discharged into an active scavenging system via port 13. ]

Efficacy of a T-piece system and a continuous positive airway pressure system for apnea testing in the diagnosis of brain death

Efficacy of a T-piece system and a continuous positive airway pressure system for apnea testing in the diagnosis of brain death

Efficacy of a T-piece system and a continuous positive airway pressure system for apnea testing in the diagnosis of brain death*

To prospectively compare three methods of apnea testing for the confirmation of brain death. Prospective, randomized, crossover study. Intensive care unit of a tertiary care university hospital. Twenty adult patients requiring apnea testing for confirmation of brain death. Ten minute apnea testing was repeated in random order for every patient with the three oxygenation systems: oxygen catheter inserted through the endotracheal tube (oxygen 6 L/min), T-piece system (oxygen 12 L/min), and continuous positive airway pressure (CPAP) system 10 cm H2O (oxygen 12 L/min). Arterial blood was drawn at 0, 2, 5, and 10 mins of each test. Compared with baseline, Paco2 increased by 30.6 +/- 7.4, 30.0 +/- 7.3 and 30.2 +/- 7.5 mm Hg during the apnea period (p = .96), reaching 73.3 +/- 8.3, 71.6 +/- 11.1, and 72.7 +/- 9.0 mm Hg at the end of the apnea test (p = .73) for the oxygen catheter, the T-piece, and the CPAP, respectively. Pao2 decreased less with the CPAP compared with the oxygen catheter or the T-piece (-22.4 +/- 76, -99.1 +/- 158, and -91.6 +/- 133 mm Hg, respectively, p < .01). In two patients, apnea testing could not be completed with the oxygen catheter and the T-piece because of desaturation, although it could be completed with the CPAP. The T-piece and the CPAP systems are effective alternatives to the standard oxygen catheter technique for apnea testing. Oxygenation was best maintained with the CPAP system, which can be useful in some patients.

Is nitric oxide in exhaled air produced at airway or alveolar level?

The aim of this study was to determine whether the nitric oxide (NO) measured in exhaled air is produced at airway or alveolar level. Exhaled NO was measured using a chemiluminescence analyser, and carbon dioxide (CO2 concentration using a Morgan capnograph in single exhalations in 12 healthy subjects (mean age 32 yrs; 6 males and 6 females). For each subject, five exhalations were made directly into the NO analyser and five were made through a T-piece system, which allowed measurement of expiratory flow rate. The peak NO levels measured via the T-piece system were 41.2 (SEM 10.8) parts per billion (ppb), significantly lower than direct levels 84.8 (14.0) ppb (p<0.001). The levels of NO tended to rise to an early peak and plateau, while the CO2 levels continued to rise to peak late in the exhalation. The mean times to reach peak NO levels were 32.2 s (direct) and 23.1 s (T-piece), which were significantly different from that of peak CO2 levels 50.5 s (direct) and 51.4 s (T-piece) (p<0.001). At peak NO level, the simultaneous CO2 level mean 4.9% (SEM 0.14)%, was significantly lower than the peak CO2 reached, 5.8 (0.21)% (p<0.001). We conclude that peak nitric oxide levels are dependent on measurement conditions. There are significant differences between the time to peak of carbon dioxide and nitric oxide. Therefore, most nitric oxide, unlike carbon dioxide, is produced in airways and not at alveolar level.

Emergency transtracheal ventilation: assessment of breathing systems chosen by anaesthetists.

The choice of equipment for emergency transtracheal ventilation and the time taken to assemble it were surveyed in 39 anaesthetists. Thirty seven (95%) assembled a system in a median time of 104 s (interquartile range 54 s to 120 s). Systems specially constructed from oxygen tubing and connectors took longest to put together (p < 0.05). Consultants and senior registrars performed no better than senior house officers and registrars (p > 0.05). In the second part of the study we tested four anaesthetic systems which the survey revealed might be chosen for emergency transtracheal ventilation. These were: a simple length of oxygen tubing; a T-piece system; a Bain system; a jet injector. All had the appropriate connectors. The oxygen flow was measured through a 14 G venous "transtracheal' cannula on depression of the oxygen flush device on a standard Boyle's M anaesthetic machine. The jet injector was connected to the high pressure outlet. This device delivered the highest flow, 43 l.min-1 and was the only system capable of ventilating a trachea/lung model. The T-piece system, and the one constructed from oxygen tubing, delivered flows of 12.7 and 12.0 l.min-1, respectively, whereas the Bain system delivered only 4.7 l.min-1. We conclude that, except for jet ventilation, none of the systems chosen, using equipment available in the anaesthetic room, would be likely to achieve effective CO2 elimination; at best they would provide oxygenation.

Another antipollution device for the Jackson‐Rees modification of Ayre's T‐piece system

AnaesthesiaVolume 46, Issue 12 p. 1094-1094 Free Access Another antipollution device for the Jackson-Rees modification of Ayre's T-piece system C.M. Kumar, C.M. KumarSearch for more papers by this author C.M. Kumar, C.M. KumarSearch for more papers by this author First published: December 1991 https://doi.org/10.1111/j.1365-2044.1991.tb09959.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume46, Issue12December 1991Pages 1094-1094 RelatedInformation

USE OF CONTINUOUS POSITIVE AIRWAY PRESSURE IN PAEDIATRIC DENTAL EXTRACTION UNDER GENERAL ANAESTHESIA

In a controlled prospective study, we studied 150 grade ASA I children undergoing outpatient dental extraction under inhalation anaesthesia with a T-piece system allocated to three equal groups: a control group (0 cm H2O CPAP), and two study groups receiving 2.5 or 5 cm H2O of CPAP via a nasal mask. We found that the incidence and severity of oxygen desaturation were reduced significantly in the 5-cm H2O CPAP group.

Accuracy of end-tidal PCO2 measurements using a sidestream capnometer in infants and children ventilated with the Sechrist infant ventilator

To determine the accuracy of end-tidal PCO2 (PETCO2) measurements analyzed with a sidestream capnometer in infants and children whose lungs were ventilated with a Sechrist infant ventilator and an Ayre's t-piece, we compared PETCO2 measurements obtained from the proximal (PETCO2-p) and distal (PETCO2-d) ends of the tracheal tube to arterial PCO2 (PaCO2) in 37 healthy infants and children between 1.3 and 24.5 kg. Both PETCO2-p and PETCO2-d accurately approximated PaCO2, however, the mean (+/- SD) arterial to end-tidal PCO2 difference (delta(a-ET)PCO2) was significantly greater with proximal (1.27 +/- 1.54 mmHg) than with distal sampling (0.64 +/- 1.64 mmHg) (P less than 0.01). In the subgroup of patients who weighted less than 12 kg, the delta(a-ET)PCO2 using proximal gas sampling (1.94 +/- 1.29 mmHg) was also significantly greater than it was using distal sampling (0.74 +/- 1.31 mmHg) (P less than 0.001). We conclude that although statistically different, both proximal and distal estimates of PETCO2 provide acceptable estimates of PaCO2 in healthy infants and children who are ventilated with a Sechrist infant ventilator and an Ayre's t-piece system.

FLOW REQUIREMENTS AND REBREATHING DURING MECHANICALLY CONTROLLED VENTILATION IN A T-PIECE (MAPLESON E) SYSTEM

The influence of fresh gas flow (FGF) setting on rebreathing was investigated in 15 infants and children (weight 3.5-21.8 kg) during balanced anaesthesia with mechanically controlled ventilation using a T-piece (Mapleson E) system and a Nuffield ventilator 200. Tidal volume (VT), minute volume (VE), maximal inspired (PICO2) and end-tidal (PE'CO2) carbon dioxide tensions and airway pressure were measured. VE, set to produce a PE'CO2 of about 4.5 kPa and measured at a high FGF (minimal rebreathing), was unchanged throughout the study and the regression equation for VE and weight was: VE (ml min-1) = 146 x kg + 482, r = 0.92. Measurements were then repeated at FGF:VE ratios reduced to 1.5 and 1.0. To achieve minimal rebreathing (PICO2 less than 0.5 kPa), FGF:VE ratios greater than 1.8 (range 1.8-4.9) had to be used. At FGF:VE ratios of 1.5, some alveolar rebreathing occurred, indicated by increased inspired (P less than 0.001) and end-tidal (P less than 0.001) carbon dioxide tensions. At FGF:VE ratios equal to 1.0, alveolar rebreathing was more pronounced and hypercapnoea occurred with a PE'CO2 (mean +/- 1 SD) of 5.89 +/- 0.53 kPa. At this FGF setting, change in I:E ratio from 1:2 to 1:1 did not influence the level of alveolar rebreathing. A minimal FGF (ml min-1) setting of 1.5 x VE (that is, 1.5 (146 x kg + 482), approximated to the expression (200 x kg + 1000) is recommended for controlled ventilation to avoid hypercapnoea when using the T-piece system in children weighing less than 20 kg.

An evaluation of six disposable heat and moisture exchangers.

Six disposable heat and moisture exchangers were tested on patients undergoing anaesthesia requiring mechanical ventilation. Inspiratory humidity and temperature were monitored to find the steady-state values reached with each device together with the times taken for these to be achieved. The exchangers were tested in a non-rebreathing T-piece circuit and in a conventional circle system with a fresh gas flow of 6 l/min: the Siemens 150 provided 28 and 32 mg of water/litre of inspired gas (at about 30 degrees C) in 10 and 5 min respectively, but is rather heavy and bulky. The Portex Humidvent provided 25 and 30 mg/l, and although taking longer to reach steady state (27 and 15 min respectively) is small, light and cheap. The Siemens 151 provided 25 and 27 mg/l in 18 and 10 min respectively, but is heavier than the Portex exchanger. The performances of these three devices were not significantly different from each other in either study (P less than 0.05). For the T-piece system the Pall and Engstrom exchangers were the next most efficient. The Pall device provided 18 and 23 mg/l (in 18 and 8 min respectively) and the Engstrom provided 20 and 23 mg/l (in 19 and 10 min respectively). In the circle system, there were no significant differences between the performances of the Portex, Siemens 151, Pall and Engstrom exchangers. The Pall is also a very effective bacterial filter and has been found to be satisfactory in the intensive care setting. The Terumo appeared to perform no better than a circle system with catheter mount (13 mg/l at 27 degrees C). It would seem that more complex humidification equipment is not necessary during anaesthesia if an efficient heat and moisture exchanger is used.

CO2 rebreathing of T-piece system in patients during recovery phase from acute respiratory failure

Eight respiratory parameters which might affect the amount of carbon dioxide rebreathing were assessed in seven patients who were breathing spontaneously from large-bore T tube system during the recovery phase from acute respiratory failure. With multivariate regression analysis, the absolute amount of rebreathed CO2 at the connector of endotracheal tube (VINSPCO2) were approximately estimated by using relatively small number of parameters, including minute volume (VEXP), fresh gas inflow to T piece system (VFGI) and preferably by additional parameters concerning CO2 output of the patients.CO2 rebreathing ratio, VINSPCO2 divided by gross outward flux of CO2 at the connector (VEXPCO2), was predicted with simple regression equation by using (VEXP/VFGI) as follows,(VINSPCO2)/(VEXPCO2) = 0.405 + 0.33 x ln (VEXP/VFGI)The maximum (VEXP/VFGI) ratio to prevent rebreathing of CO2 at the connector was 0.30, whereas the ratio to prevent CO2 accumulation due to rebreathing was 0.45.