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Plotnikow GA, Accoce M, Navarro E, Tiribelli N. Humidification and heating of inhaled gas in patients with artificial airway. A narrative review. Rev Bras Ter Intensiva 2018; 30:86-97. [PMID: 29742220 PMCID: PMC5885236 DOI: 10.5935/0103-507x.20180015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 08/30/2017] [Indexed: 01/15/2023] Open
Abstract
Instrumentation of the airways in critical patients (endotracheal tube or
tracheostomy cannula) prevents them from performing their function of humidify
and heating the inhaled gas. In addition, the administration of cold and dry
medical gases and the high flows that patients experience during invasive and
non-invasive mechanical ventilation generate an even worse condition. For this
reason, a device for gas conditioning is needed, even in short-term treatments,
to avoid potential damage to the structure and function of the respiratory
epithelium. In the field of intensive therapy, the use of heat and moisture
exchangers is common for this purpose, as is the use of active humidification
systems. Acquiring knowledge about technical specifications and the advantages
and disadvantages of each device is needed for proper use since the conditioning
of inspired gases is a key intervention in patients with artificial airway and
has become routine care. Incorrect selection or inappropriate configuration of a
device can have a negative impact on clinical outcomes. The members of the
Capítulo de Kinesiología Intensivista of the
Sociedad Argentina de Terapia Intensiva conducted a
narrative review aiming to show the available evidence regarding conditioning of
inhaled gas in patients with artificial airways, going into detail on concepts
related to the working principles of each one.
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Affiliation(s)
- Gustavo Adrián Plotnikow
- Capítulo de Kinesiología Intensivista, Sociedad Argentina de Terapia Intensiva, Buenos Aires, Argentina
| | - Matias Accoce
- Capítulo de Kinesiología Intensivista, Sociedad Argentina de Terapia Intensiva, Buenos Aires, Argentina
| | - Emiliano Navarro
- Capítulo de Kinesiología Intensivista, Sociedad Argentina de Terapia Intensiva, Buenos Aires, Argentina
| | - Norberto Tiribelli
- Capítulo de Kinesiología Intensivista, Sociedad Argentina de Terapia Intensiva, Buenos Aires, Argentina
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Lellouche F. Quelle technique d’humidification pour la ventilation invasive et non invasive ? MEDECINE INTENSIVE REANIMATION 2015. [DOI: 10.1007/s13546-015-1131-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Humidification during mechanical ventilation in the adult patient. BIOMED RESEARCH INTERNATIONAL 2014; 2014:715434. [PMID: 25089275 PMCID: PMC4096064 DOI: 10.1155/2014/715434] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/19/2014] [Accepted: 05/27/2014] [Indexed: 12/17/2022]
Abstract
Humidification of inhaled gases has been standard of care in mechanical ventilation for a long period of time. More than a century ago, a variety of reports described important airway damage by applying dry gases during artificial ventilation. Consequently, respiratory care providers have been utilizing external humidifiers to compensate for the lack of natural humidification mechanisms when the upper airway is bypassed. Particularly, active and passive humidification devices have rapidly evolved. Sophisticated systems composed of reservoirs, wires, heating devices, and other elements have become part of our usual armamentarium in the intensive care unit. Therefore, basic knowledge of the mechanisms of action of each of these devices, as well as their advantages and disadvantages, becomes a necessity for the respiratory care and intensive care practitioner. In this paper, we review current methods of airway humidification during invasive mechanical ventilation of adult patients. We describe a variety of devices and describe the eventual applications according to specific clinical conditions.
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Sammour T, Kahokehr A, Hill AG. Independent testing of the Fisher & Paykel Healthcare MR860 Laparoscopic Humidification System. MINIM INVASIV THER 2010; 19:219-23. [DOI: 10.3109/13645701003644475] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Schumann S, Stahl CA, Möller K, Priebe HJ, Guttmann J. Moisturizing and mechanical characteristics of a new counter-flow type heated humidifier. Br J Anaesth 2007; 98:531-8. [PMID: 17327253 DOI: 10.1093/bja/aem006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND During mechanical ventilation effective conditioning of inspired air is important. In this respect, conventional humidifiers do not perform optimally. By design, a counter-flow-type humidifier should improve humidification and heating, but may increase resistance. METHODS We investigated mechanical impedance and work of breathing (using pressure-flow characteristics and additional pressure-time product) of a new counter-flow-type humidifier, a conventional heated humidifier, and a passive heat and moisture exchanger (HME) in physical models of the respiratory system. We investigated moisturizing performance (amount of vaporized water at different air flows and ventilatory frequencies) of the two heated humidifiers. Ease of breathing through both heated humidifiers was investigated in 12 healthy volunteers blinded to the type of humidifier. RESULTS Moisturizing performance of the conventional heated humidifier was flow-independent (approximately 32.5 mg vaporized water per breath at inspiratory flow rates of 30-120 litre min (- 1); P > 0.05) but decreased (10%; P < 0.0001) with increasing ventilatory rates (12-20 min (- 1)). In contrast, moisturizing performance of the counter-flow-type humidifier (approximately 33.5 mg vaporized water per breath) was both flow- and rate-independent (P = 0.75). In addition, the counter-flow humidifier caused less physical work (approximately 25%) and resistance (approximately 50%) (both P < 0.05) than the other two devices. The passive HME displayed the least favourable mechanical characteristics. Ten of 12 volunteers felt breathing through the counter-flow humidifier easier than through the heated humidifier (P < 0.05). CONCLUSION Compared with a conventional humidifier, the new counter-flow-type humidifier displayed improved air conditioning and mechanical characteristics. Its lower resistance, particularly at low airflows, should be of clinical benefit during spontaneous breathing and triggered assisted ventilation.
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Affiliation(s)
- S Schumann
- Department of Anaesthesiology and Intensive Care, Section for Experimental Anaesthesiology, University Hospital Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany.
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Ricard JD, Le Mière E, Markowicz P, Lasry S, Saumon G, Djedaïni K, Coste F, Dreyfuss D. Efficiency and safety of mechanical ventilation with a heat and moisture exchanger changed only once a week. Am J Respir Crit Care Med 2000; 161:104-9. [PMID: 10619805 DOI: 10.1164/ajrccm.161.1.9902062] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The cost of mechanical ventilation (MV) is high. Efforts to reduce this cost, as long as they are not detrimental for the patients, are needed. MV with heat and moisture exchangers (HME) changed every 48 h is safe, efficient, and cost-effective. Preliminary reports suggest that the life span of these filters may be prolonged. We determined prospectively whether a hygroscopic and hydrophobic HME (Hygrobac-Dar; Mallinckrodt) provided safe and efficient heating and humidification of the inspired gases when changed only once a week. Patients who were considered to require mechanical ventilation for more than 48 h were included in the study. HMEs were initially set for 7 d. Efficient airway heating and humidification were assessed by clinical parameters (number of tracheal suctionings and instillations required, peak airway pressures) and hygrometric measurements performed by psychrometry. Resistance was measured from Day 0 to Day 7. Bacterial colonization of circuits and HMEs was studied. A total of 377 days of mechanical ventilation with 60 HMEs was studied. Clinical parameters and hygrometric measurements did not change between Day 0 and Day 7. Mean absolute humidity was 30.3 +/- 1.3 mg H(2)O/L on Day 0 and 30.8 +/- 1.5 mg H(2)O/L on Day 7 (p = 0.7). Endotracheal tube occlusion never occurred. Three HMEs were replaced prematurely because of insufficient absolute humidity. This rare event occurred only in patients with COPD and after the third day of use. In addition, the absolute humidity delivered by the HMEs was significantly lower in patients with COPD than in the rest of the population. Resistance did not change from Day 0 to Day 7 (2.4 +/- 0.3 versus 2.7 +/- 0.3 cm H(2)O/L/s; p = 0.4). Bacterial samples of both circuits and ventilator sides of HMEs were sterile in most cases. We conclude that mechanical ventilation can be safely conducted in non-COPD patients using an HME changed only once a week, leading to substantial cost savings (about $110,000 per year if these findings were applied to the university-affiliated hospitals in Paris).
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Affiliation(s)
- J D Ricard
- Service de Réanimation Médicale et de Bactériologie, Hôpital Louis Mourier (Assistance Publique-Hôpitaux de Paris), Colombes, France
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Abstract
Weaning patients from mechanical ventilation in the intensive care unit can be difficult. In patients requiring prolonged ventilatory support it has been demonstrated that conventional weaning criteria are frequently incorrect. In this group measurement of respiratory work may be of benefit. Until recently, estimation of the work of breathing in patients receiving mechanical ventilation was logistically difficult. The availability of a computerized bedside monitoring device potentially allows easier estimation of the work of breathing at the bedside. The results of preliminary studies utilizing such monitoring are provocative: they highlight the phenomenon of nosocomial respiratory failure and challenge our clinical ability to determine patient workloads and timing of extubation. The potential benefits of work of breathing measurement, in particular the avoidance of respiratory muscle fatigue, earlier extubation, reduced duration of mechanical ventilation, reduction in ICU and hospital length of stay, and most importantly, a reduction in patient morbidity are yet to be demonstrated and concerns still exist about the monitor's accuracy.
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Affiliation(s)
- C J French
- Division of Anaesthesia, Western Hospital, Melbourne, Victoria, Australia
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Ricard JD, Markowicz P, Djedaini K, Mier L, Coste F, Dreyfuss D. Bedside evaluation of efficient airway humidification during mechanical ventilation of the critically ill. Chest 1999; 115:1646-52. [PMID: 10378563 DOI: 10.1378/chest.115.6.1646] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
STUDY OBJECTIVE To determine the correlation between simple rating of condensation seen in the flex-tube connecting the heating and humidifying device used with the endotracheal tube and hygrometric parameters (absolute and relative humidity and tracheal temperature) measured by psychrometry. DESIGN Prospective randomized clinical trial. SETTING Medical ICU of Louis Mourier Hospital, Colombes, France, a university-affiliated teaching hospital. PATIENTS Forty-five consecutive mechanically ventilated critically ill patients. INTERVENTIONS Patients undergoing mechanical ventilation were randomly assigned to receive humidification with one of the four heat and moisture exchangers (HMEs) tested or with a conventional heated humidifier. MEASUREMENTS The hygrometric performances of four HMEs (BB2215, BB50, and BB100 from Pall Biomedical, Saint-Germaine-en-Laye, France; and Hygrobac-Dar from Mallinckrodt, Mirandola, Italy) and a heated humidifier (Fisher & Paykel; Auckland, New Zealand) were studied after 3 h and also after 48 h of use for the Hygrobac-Dar and correlated to a clinical visual inspection rating the amount of condensation in the flex-tube of the endotracheal tube. RESULTS A total of 95 measurements in 45 patients were performed. The best hygrometric parameters were obtained with the heated humidifier (p < 0.001). The Hygrobac-Dar yielded significantly higher values for both humidities and tracheal temperature than the other three HMEs (p < 0.001). The performance of Hygrobac-Dar was unchanged after 48 h of use. There was a significant correlation between the condensation seen in the flex-tube and the hygrometric parameters measured by psychrometry (absolute humidity, rho = 0.7; relative humidity, rho = 0.7; tracheal temperature, rho = 0.5, p < 0.0001). CONCLUSION In mechanically ventilated ICU patients, visual evaluation of the condensation in the flex-tube provides an estimation of the heating and humidifying efficacy of the heating and humidifying device used, thus allowing the clinician bedside monitoring of airway humidification.
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Affiliation(s)
- J D Ricard
- Service de Réanimation Médicale, Hôpital Louis Mourier (Assistance Publique-Hopitaux de Paris), Colombes, France
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Iotti GA, Olivei MC, Braschi A. Mechanical effects of heat-moisture exchangers in ventilated patients. Crit Care 1999; 3:R77-82. [PMID: 11094485 PMCID: PMC137236 DOI: 10.1186/cc361] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/1999] [Revised: 09/06/1999] [Accepted: 09/08/1999] [Indexed: 12/05/2022] Open
Abstract
Although they represent a valuable alternative to heated humidifiers, artificial noses have unfavourable mechanical effects. Most important of these is the increase in dead space, with consequent increase in the ventilation requirement. Also, artificial noses increase the inspiratory and expiratory resistance of the apparatus, and may mildly increase intrinsic positive end-expiratory pressure. The significance of these effects depends on the design and function of the artificial nose. The pure humidifying function results in just a moderate increase in dead space and resistance of the apparatus, whereas the combination of a filtering function with the humidifying function may critically increase the volume and the resistance of the artificial nose, especially when a mechanical filter is used. The increase in the inspiratory load of ventilation that is imposed by artificial noses, which is particularly significant for the combined heat-moisture exchanger filters, should be compensated for by an increase either in ventilator output or in patient's work of breathing. Although both approaches can be tolerated by most patients, some exceptions should be considered. The increased pressure and volume that are required to compensate for the artificial nose application increase the risk of barotrauma and volutrauma in those patients who have the most severe alterations in respiratory mechanics. Moreover, those patients who have very limited respiratory reserve may not be able to compensate for the inspiratory work imposed by an artificial nose. When we choose an artificial nose, we should take into account the volume and resistance of the available devices. We should also consider the mechanical effects of the artificial noses when setting mechanical ventilation and when assessing a patient's ability to breathe spontaneously.
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Affiliation(s)
- G A Iotti
- Servizio di Anestesia e Rianimazione 1, IRCCS Policlinico S. Matteo, Pavia, Italy.
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Subayi L, Chergui K, Beydon L. [Heat and moisture exchanging filters for conditioning of inspired gases in adult anesthesia and resuscitation]. ANNALES FRANCAISES D'ANESTHESIE ET DE REANIMATION 1998; 17:699-708. [PMID: 9750808 DOI: 10.1016/s0750-7658(98)80107-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Heat and moisture-exchanging filters (HMEFs) are increasingly used in clinical practice. At the same time, new scientific data are available which clarify the benefits of these devices. DATA SOURCES We searched in the Medline database for all papers written in English or French, without limiting date of publication, using the following key-words separately or in combination: humidity, temperature, mechanical ventilation, equipment. STUDY SELECTION From the 200 articles provided by Medline, we selected those directly concerning HMEFs. Some older studies and those on HMEFs no longer available were excluded. DATA EXTRACTION Principle data available from the literature were analysed. DATA SYNTHESIS Humidification and warming of the inspired gas mixture is mandatory during mechanical ventilation. There is a direct link between HMEF performance and the characteristics of tracheal secretions. This justified the recommendation for the use of HMEFs with a humidity output above 30 mg of water per litre of gas mixture. In this case, HMEFs are as efficient as conventional heated humidifiers. HMEFs seem to decrease the rate of nosocomial pneumonia in comparison with heated humidifiers. HMEFs induce a slight increase of dead space which should be taken into consideration during weaning from mechanical ventilation. There are demonstrable data in the literature suggesting the possibility of cross viral infection via the anaesthetic machine when an HMEF is not used. There are no data which suggest a specific type of HMEF regarding viral filtration. CONCLUSION According to the literature data, using an HMEF is essential in anaesthesia and is highly recommended in intensive care.
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Affiliation(s)
- L Subayi
- Département d'anesthésie-réanimation, CHU d'Angers, France
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Tan IK, Bhatt SB, Tam YH, Buckley TA, Oh TE. Superimposed inspiratory work of the Siemens Servo 300 ventilator during continuous positive airway pressure. Intensive Care Med 1995; 21:1023-6. [PMID: 8750128 DOI: 10.1007/bf01700665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To compare the superimposed inspired work of breathing (SIW) of the Siemens Servo 300 ventilator with the Siemens Servo 900 C ventilator. DESIGN Comparisons made at continuous positive airway pressure (CPAP) levels of 0, 4, and 8 cmH2O, and at trigger sensitivities of -1 and -2 cmH2O, and flow triggering. SETTING General intensive care unit in a University teaching hospital. PATIENTS 7 patients receiving CPAP. At all levels of CPAP, the SIW was significantly less with the Siemens Servo 300 ventilator as compared to the Siemens Servo 900 C ventilator despite similar trigger sensitivities. No significant difference was found in the SIW of the Servo 300 ventilator when comparing trigger sensitivities of -1 cmH2O, -2 cmH2O, and flow triggering. Different levels of CPAP had no effect on SIW. CONCLUSIONS The Siemens Servo 300 ventilator entails less superimposed inspiratory work of breathing than the Siemens Servo 900 C ventilator.
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Affiliation(s)
- I K Tan
- Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT
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Johnson PA, Raper RF, Fisher MM. The impact of heat and moisture exchanging humidifiers on work of breathing. Anaesth Intensive Care 1995; 23:697-701. [PMID: 8669603 DOI: 10.1177/0310057x9502300607] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this study the resistive work or breathing (WOB) associated with eleven commercially available heat and moisture exchangers (HMEs) was evaluated for gas flow rates of 20 to 60 l.min-1. The Gibeck Humid-Vent 2S Flex was also assessed after 24 hours patient usage (n = 50). The WOB associated with these devices was compared with that of standard endotracheal tubes and standard humidifying circuits with flex-tube connectors. The range of work imposed by the eleven HMEs approximated the range shown by water bath circuitry when used with two different commonly used flex-tube connectors. The excess WOB attributed to the HMEs was significantly less than that imposed by standard endotracheal tubes. After 24 hours of patient use, 96% of the Gibeck HMEs tested demonstrated a resistive WOB within the range of the two flex-tube connectors. To assess the clinical significance of this circuit-related WOB, we compared respiratory variables in 40 patients breathing on either CPAP or pressure support ventilation, using a variation in flex-tube resistance which imposed a range of WOB comparable to that shown by the HMEs. A small but statistically significant reduction was found for both the peak flow (48 +/- 1.4 vs 45 +/- 1.1 l.min-1, P < 0.0005) and the minute volume (8.6 +/- 0.35 vs 7.9 +/- 0.31, l, P < 0.0005). These data suggest that the range of resistive work imposed by commercially available HMEs has a small but potentially significant effect on clinical respiratory parameters.
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Affiliation(s)
- P A Johnson
- Royal North Shore Hospital, St Leonards, N.S.W
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Criner GJ, Tzouanakis A, Kreimer DT. Overview of Improving Tolerance of Long-Term Mechanical Ventilation. Crit Care Clin 1994. [DOI: 10.1016/s0749-0704(18)30110-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Oh TE, Bhatt S, Tam YH. Bedside measurement of work of breathing. INTERNATIONAL JOURNAL OF CLINICAL MONITORING AND COMPUTING 1993; 10:127-129. [PMID: 8366313 DOI: 10.1007/bf01142283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
This paper describes the technique of measuring work of breathing, presented at the 13th International Symposium on Computers in Clinical Medicine and Anaesthesiology, Rotterdam, June 1992. Measuring work of breathing has clinical uses in the Intensive Care Unit. Oxygen consumption does not truly reflect work of breathing. Mechanical work of breathing can be measured by recording continuous pressure and flow and integrating the resultant power. This method is facilitated at the bedside with the use of a PC computer and a spreadsheet program. It is further simplified by software to measure the area under the inspiratory pressure: volume loop.
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Affiliation(s)
- T E Oh
- Department of Anaesthesia & Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital
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Bersten AD, Rutten AJ, Vedig AE. Efficacy of pressure support in compensating for apparatus work. Anaesth Intensive Care 1993; 21:67-71. [PMID: 8447610 DOI: 10.1177/0310057x9302100116] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Breathing through an endotracheal tube, connector, and ventilator demand valve imposes an added load on the respiratory muscles. As respiratory muscle fatigue is thought to be a frequent cause of ventilator dependence, we sought to examine the efficacy of five different ventilators in reducing this imposed work through the application of pressure support ventilation. Using a model of spontaneous breathing, we examined the apparatus work imposed by the Servo 900-C, Puritan Bennett 7200a, Engstrom Erica, Drager EV-A or Hamilton Veolar ventilators, a size 7.0 and 8.0 mm endotracheal tube, and inspiratory flow rates of 40 and 60 l/min. Pressure support of 0, 5, 10, 15, 20 and 30 cm H2O was tested at each experimental condition. Apparatus work was greater with increased inspiratory flow rate and decreased endotracheal tube size, and was lowest for the Servo 900-C and Puritan Bennett 7200a ventilators. Apparatus work fell in a curvilinear fashion when pressure support was applied, with no major difference noted between the five ventilators tested. At an inspiratory flow rate of 40 l/min, a pressure support of 5 and 8 cm H2O compensated for apparatus work through size 8.0 and 7.0 endotracheal tubes and the Servo 900-C and Puritan Bennett 7200a ventilators. However, the maximum negative pressure was greater for the Servo 900-C. The added work of breathing through endotracheal tubes and ventilator demand valves may be compensated for by the application of pressure support. The level of pressure support required depends on inspiratory flow rate, endotracheal tube size, and type of ventilator.
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Affiliation(s)
- A D Bersten
- Department of Anaesthesia and Intensive Care, Flinders Medical Centre, Adelaide, South Australia
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Bhatt SB, Kendall AP, Lin ES, Oh TE. Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes. Anaesthesia 1992; 47:343-7. [PMID: 1519690 DOI: 10.1111/j.1365-2044.1992.tb02179.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.
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Affiliation(s)
- S B Bhatt
- Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, N.T
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18
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Abstract
The inspiratory work (WI) imposed by three commonly used demand valve ventilator circuits was studied using a lung model to simulate spontaneous ventilation. The CPU-1 and Engstrom Erica circuits recorded WI of 379 mJ/l and 190 mJ/l respectively. A negative WI of -32 mJ/l was recorded for the Servo 900C, denoting that the circuit performed work on the lung. The demand valves recorded a time delay between inspiratory effort and onset of gas flow, of 300 ms (CPU-1), 190 ms (Servo 900c) and 160 ms (Engstrom Erica). Both the Servo 900C and Engstrom Erica demand valves were able to generate a high inspiratory gas flow response, but the CPU-1 lacked such a flow compensation. Expiratory work was also greatest with the CPU-1 (156 mJ/l) with 141 mJ/l and 90 mJ/l recorded for the Servo 900C and Engstrom Erica. Of the three ventilators studied, the Servo 900C appears to be the ventilator circuit of choice for spontaneous ventilation.
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Affiliation(s)
- T E Oh
- Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin
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