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Endotracheal suction for adult, non-head-injured, patients. A review of the literature
Intensive and Cri~.tal Care Nursing (1993) 9, 274-278
(~ Longman Group UK Ltd 1993
Endotracheal suction for adult, non-headinjured, patients. A review of the literature A. Odell, A. Allder, R. Bayne, C. Everett, S. Scott, B. Still and S. West
T h e p r o c e d u r e for endotracheal suctioning was perceived as a problem by the m e m b e r s o f a quality circle in the intensive care unit (ICU). Endotracheal suction, w h e n p e r f o r m e d in the unit, a p p e a r e d to be carried out according to the nurses' experience and expertise, and had no formal research backing. A n extensive literature search was u n d e r t a k e n , and a f r a m e w o r k for endotracheal suction was formulated based on the available evidence. Some o f the aspects o f endotracheal suction r e p r e s e n t e d in the research evidence a p p e a r contradictory, and nurses must make a professional j u d g e m e n t about their suction technique based on the individual circumstances o f patients. T h e wealth o f evidence available r e g a r d i n g endotracheal suctioning allows nurses to m a k e an i n f o r m e d decision about care.
INTRODUCTION The muco-ciliary system in the airways, fully humidified and heated to 37°C, sweeps and traps inhaled particles that may harm the lungs (Guyton 1971). Endotracheal intubation forms an artificial airway that by-passes these normal processes, and inhibits the cough reflex. The respiratory tract is vulnerable to opportunist organisms, mucus secretion is often increased, and pneumocytes and surfactant are reduced (Ackerman 1985, Bostick & Wendelglass 1987). Patients with an endotracheal/tracheostomy
A. Odell, A. AIIder, R. Bsyne, C. Everett, S. Scott, B. Still, S. West Intensive Care Unit, Royal Berkshire Hospital, London Road, Reading, Berkshire RG1 5AN, UK (Requests for offprints to AO) Manuscript accepted 30 May 1993
274
tube in situ will require periodic endotracheal suctioning to help clear secretions, and prevent atelectasis (Bostick & Wendelglass 1987, Kuzenski 1978). Suctioning is a potentially hazardous procedure (Young 1984). Severe mucosal damage can result from tracheo-bronchial suctioning. Damage occurs by passing the catheter alone (Amikan et al 1972, Plum & Dunning 1956, Jung & Gottlieb 1976, Kuzenski 1978, Rux & Powaser 1979). Associated haemodynamic complications include; arterial hypoxaemia, cardiac arrythmias, hypotension and death (Walsh et al 1989, Boutros 1970, Gunderson et al 1991, Rosan & Hillard 1962, Clark et al 1990, Demers & Saklad 1973, Deppe et al 1990, Stone et al 1991). No consistency of endotracheal suction technique is found in ICUs nationwide. There is a lack of uniformity in suctioning procedures, and confusion over what constitutes proper technique (Bostick & Wendelglass 1987).
INTENSIVE AND CRITICAL CARE NURSING
Endotracheal suctioning should only be performed when necessary, and not as routine (Young 1984, Rosan & Hillard 1962). The patient should be assessed by the nurse prior to each suction, and one or more of the following found: rise in ventilator peak inspiratory pressure; secretions heard or visible during respiration; diminished breath sounds on auscultation; crepitations on auscultation. The following information from literature provides some basis for deciding on procedures for airway clearance.
275
Whistle tip and tri-flo catheters are not licensed in the UK. Single-hole catheters produce more trauma than multiple-hole catheters (Sackner et al 1973, Link et al 1976). The damage caused by multiple-hole catheters is due to the insertion of the catheter alone, and not by mucosal grabbing when suction is applied (Link et al 1976). Catheters should have a built-in valve to prevent a vacuum being applied to the trachea on insertion (Young 1984, Rosan & Hillard 1962).
Use of gloves STANDARD SUCTION PROCEDURE The catheter The catheter should be inserted gently into the trachea. The more vigorous the insertion, the more damage occurs 0 u n g et al 1976). The catheter should occlude no more than one half of the diameter of the endotracheal tube, to permit an inflow of oxygen during removal of alveolar gas while suctioning (Young 1984, Rosan et al 1962). A formula for calculating suction catheter size with endotracheal tubes greater than size 6Ch is: endotracheal tube size - 2 x 2. There are many types of suction catheter available on the market today (Young 1984), including the following types: Characterised by two triangular side-holes offset from the centre line and close to the bevelled catheter tip. - - aero-flo (bead tip) Four small round sideholes near the expanded tip. Bead tip catheters cause less damage but have less effective suctioning (Link et al 1976, Sackner et al 1973). Gentle-fit Four oval side-holes close to the tip. - - D u a l side hole Two large side-holes somewhat removed from the tip. - - Whistle tip Single side-hole. These catheters produce measurable mucosal damage beyond that related to catheter insertion (Link et al 1976).
--Tri-flo
-
Endotracheal suction should be performed under aseptic technique to reduce bacteriologic colonization and cross contamination in the trachea (Link et al 1976). There appears to be no evidence available on the wearing of gloves, either sterile or unsterile. Hospitals appear to vary in their policy from wearing unsterile gloves to double gloving. Wearing gloves is more effective than washing hands (Newsom & Rowland 1989).
The vacuum The higher the negative pressure applied through the catheter the greater the degree of ulceration, hypoxaemia, airway collapse and atelectasis (Rosan et al 1962, Plum & Dunning 1956, Sackner et al 1973, Brundstater & Muallem 1969, Thambrian & Ripley 1966, Rux & Powaser 1979). Higher negative pressures do not directly relate to the quantities of mucus extracted (Regan 1988). A negative pressure of 70-100mmHg (9.313.3kPa) is suggested (Thambrian & Ripley 1966, Kuzenski 1978), although clinically this may not be enough to extract secretions, therefore negative pressures up to 200mmHg (27kPa) may be needed.
-
Duration and continuity of suction The longer the duration of suctioning, the more mucosal damage and hypoxia occurs (Sackner et al 1973, Thambrian & Ripley 1966, Rosan & Hillard 1962, Brandstater & Muallem 1969, Boutros 1970).
276
INTENSIVE AND CRITICAL CARE NURSING
The duration of suctioning should last no more than 30sec, but ideally 15sec (Young 1984). Intermittent vacuum pressure causes less mucosal damage (Young 1984).
SUPPLEMENTARY SUCTION PROCEDURES The use of saline The common practice of instilling up to 10 ml of normal saline into the trachea, prior to suctioning, is abnormal (Ackerman 1985), and appears to have minimal or no benefit for clearing secretions (Ackerman 1985, Demers & Saklad 1973, Hanley et al 1978). Some studies suggest that a significantly greater amount of material is aspirated with the instillation of saline (Gray et al 1990), but this could be due to the cough elicited by this procedure. Instillation of saline down the endotracheal tube could interfere with alveolar capillary oxygen exchange, and give the patient the sensation of drowning (Wade 1982, Bostock & Wendelglass 1987). Hanley et al (1978), only recovered 10-20% of normal saline instilled into the trachea. Mucus and water are immiscible and occupy separate phases in vitro (Demers & Saklad 1973). However the instillation of saline produces a cough (Demers & Saklad 1973, Bostick & Wendelglass 1987, Downs 1989). To maintain a patent airway, the patient must firstly be adequately hydrated (Ackerman 1985). The u s e of heat and humidity should almost eliminate dried and tenacious secretions (Ackerman 1985, Hanley et al 1978, Shapiro et al 1983, Khan 1983). The practice of instilling bolus saline should be substituted for nebulised saline if secretions require loosening (Demers & Saklad 1973).
Hyperinflation/hyperventilation (Bag squeezing) Hyperinflation (bagging) is a way to provide artificial or hand ventilation to an intubated
patient to improve lung expansion, by using a Waters bag connected to an oxygen supply. Hyperventilation is performed by rhythmically squeezing the bag (MacKenzie 1981), while continually adjusting the rate, tidal volume and pressure in response to changes in the patient's lung compliance (Oh TE 1990). These breaths of unknown pressure and volume mimic sighing and yawning which helps expand the alveoli and prevent atetectasis by dislodging secretions. But hyperventilation with a rebreathing bag can cause the patient to feel dyspnoeic and uncomfortable (Lookinland & Appel 1991). High airway pressures during hyperventilation can result in hypotension, decrease in cardiac output and barotrauma. Hyperinflation with the rebreathing bag can help to prevent hypoxia by preventing atelectasis caused during suction (Boutrous 1970), therefore hyperventilation before and after endotracheal suction is recommended in certain instances (Lookinland & Appe11991, MacKenzie et al 1981). Hyperinflation of the lungs with 100% oxygen must be carried out with care, as rapid acid-base changes in the blood may affect the stability of severely ill patients. It should be attempted only by experienced staff (Young 1984). Where it is necessary to hyperventilate a patient, a pressure manometer should be used in the breathing circuit. The pressure produced by the bag should mimic the patients' ventilator peak inspiratory pressure.
Pre-oxygenation Hyperoxygenation is an increase in the concentration of inspired oxygen used to relieve hypoxaemia induced by endotracheal suctioning. Endotracheal suctioning causes a decrease in oxygen saturation by 25-30%, followed by a slow rise back to baseline over a 3 rain period. Oxygen consumption rises significantly after the open method of endotracheal suctioning (Walsh et al 1989). The oxygen supply/demand mismatch results in a drop in mixed venous oxygen content (Clark et al 1990). Bradycardias associated with endotracheal suction are not related to hypoxaemia, but are
I N T E N S I V E AND C R I T I C A L (;ARE N U R S I N G
Fig. 1 Closed auction system.
due to mechanical and neural stimulation which is vagally mediated (Gunderson et al 1991). Hyperoxygenation, in conjunction with hyperventilation at 100% oxygen, before, during and after suction causes arterial oxygen saturation to remain elevated (Lookinland & Appel 1991, Chulay & Graeber 1988). As a reliable measure of oxygen delivery, transcutaneous oximetry is especially valuable during procedures that may cause an abrupt change in PaO2. Although oxygen saturation measurements do not necessarily reflect large decreases in mixed venous oxygen content (Walsh et al 1989). Where possible, mixed venous saturation should be monitored.
Closed suction system T h e r e is now a closed suction system which is connected to the endotracheal tube o f a patient on mechanical ventilation, and can be left in place for 24h. Suctioning does not require disconnection from the ventilator, thus maintaining oxygen delivery and PEEP (positive end expiratory pressure). Closed suction systems improve oxygen saturation, decrease clinical signs of hypoxaemia and maintain levels o f positive end expiratory pressure (Demajo unpublished, Ritz et al 1986, Wilhelm et al, unpublished). T h e r e was no difference in oxygen saturation and oxygen tension between patients with the closed suction system and those with a conventional system where PEEP was below 10mmHg.
277
Where patients were on higher levels of PEEP, saturation was maintained with the closed suction system, but not the conventional method (Graziano et al 1987). Closed suction systems reduce the risk of environmental and cross-contamination, and do not expose the patient to increased risk of auto contamination (Cobley 1991). Scott et al (1990), found that colonisation of the trachea was significantly higher in the closed system of suction as opposed to the open system. However there was no significant difference in the incidence of nosocomial pneumonia between the two systems. Ritz et al 1986, found no significant difference in colonisation between the two methods.
CONCLUSION T h e r e is a great deal of published work that attempts to address the problems associated with endotracheal suction, and much o f it is contradictory. Nurses, who are accountable for their care, and therefore the suction that they perform, must disseminate the available information, and make an informed decision about how they will perform endotracheal suction. This decision must take into account the individuality of the patient concerned and his/her specific circumstances and condition. T o produce a rigid protocol for nurses does not allow them the flexibility to treat their patients as individuals. However each nurse providing intensive care must have the information to support the decisions that she or he makes.
References Ackerman M H 1985 The use of bolus normal saline instillations in artificial airways: is it useful or necessary? Heart and Lung 14 (5): 505-506 Amikan B, Landa J, WestJ, Sackner M 1972 Bronchofiberscopic observations of the tracheabronchial tree during intubation. American Review of Respiratory Disease 105:747-55 Bostick J, Wendelglass S T 1987 Normal saline instillation as part of the suctioning procedure: effects on PaO and amount of secretions. Heart and Lung 16 (5): 532-537
278
INTENSIVEAND CRITICALCARE NURSING
Boutros A R 1970 Arterial blood oxygenation during and after endotracheal suctioning in the apnoeic patient. Anaesthesiology 32:114-118 Brundstater B, Muallem M 1969 Atelectasis following tracheal suctioning in infants. Anaesthesiology 31: 468-473 Clark A P, Winslow E H, Tyler D O, White K M 1990 Effects of endotracheal suctioning on mixed venous oxygen saturation and heart rate in critically ill adults, Heart and Lung 19 (5): 552-557 Chulay M, Graeber G M 1988 Efficacy of a hyperventilation and hyperoxygenation suctioning intervention. Heart and Lung 17:15-22 Cobley M, Atkins M,Jones P L 1991 Environmental contamination during tracheal suction. Anaesthesia 46:957-961 Demajo W. Effects of suctioning patients without interruption of ventilation. Surgical Intensive Care Unit. Toronto General Hospital. (Unpublished) Demers R S, Saklad M 1973 Minimizing the harmful effects of mechanical aspiration. Heart and Lung 2: 542 Deppe S A, Kelly J w, Thoi L L, Chudy J H, Longfield R N, Ducey J P, Truwit C L, Antropol M R 1990 Incidence of colonisation, nosocomial pneumonia, and mortality in critically ill patients using a Trach Care closed-suction system versus an open-suction system:Prospective randomised study. Critical Care Medicine 18 (12): 1389-1393 Downs J 1989 A method of tracheal washout. Physiotherapy 75 (8) (August): 454 GrayJ E, MacIntyre N R, Kronenberger W G 1990 The effects of bolus normal-saline instillation in conjunction with endotracheal suctioning. Respiratory Care 35 (8) (August): 785-790 Graziano C C, Fox S J, Ackerman NJ 1987 Evaluation of a dosed suction system. Critical Care Medicine 15 (5): 522-525 Gunderson L P, Stone K S, Hamlin R L 1991 Endotracheal suctioning-induced heart rate alterations. Nursing Research 40 (3) (May/June): 139142 Hanley M V, Rudd T, Butler J 1978 What happens to intratracheal saline instillations. American Review of Respiratory Disease 117:124 Jung R C, Gottlieb L S 1976 Comparison of tracheobronchial suction catheters in humans. Chest 64:179-181 Khan R C 1983 Humidification of the airways: adequate for function and integrity. Chest 84:510 Kuzenski B M 1978 Effect of negative pressure on tracheobronchial trauma. Nursing Research 27: 260263 Link W J, Spaeth E E, Wahle W M, Penny W, Glover J L 1976 The influence of suction catheter tip design on tracheobronchial trauma and fluid aspiration efficiency. Anaesthetics and Analgesia 55:290-297
Lookinland S, Appel P L 1991 Haemodynamic and oxygen transport changes following endotracheal suctioning in trauma patients. Nursing Research 40 (3) (May/June): 133-138 MacKenzie C F (ed), Cielsa N, Imle P C, Klemic N 1981 Chest physiotherapy in the Intensive Care Unit. Ch5. Williams and Witkins, Baltimore Newsom S W B, Rowland C 1989 Application of the hygienic hand disinfection test to the gloved hand. The Journal of Hospital Infection 14 (3) (October); 245-247 Plum F, Dunning M F 1956 Technics for minimizing trauma to the tracheobronchial tree after tracheostomy. New England Journal of Medicine 254: 193-200 Regan M 1988 Tracheal mucosal injury - the nurse's role. Nursing 29:1064-1066 Ritz R, Scott L R, Coyle M B, Pierson DJ 1986 Contamination of a multiple use suction catheter in a closed circuit system compared to contamination of a disposable single use suction catheter. Respiratory Care 31 (11) (November): 1086-1091 Rosan M, Hitlard E K 1962 The effects of negative pressure during tracheal suctioning. Anaesthetics and Analgesia 41:50-57 Rux M I, Powaser M M 1979 Effect of apnoea and three levels of negative pressure on the fall in arterial oxygen tension produced by endotracheal suctioning in dogs. American Review of Respiratory Disease 119: 193 Sackner M A, Landa J, Greeneltch N, RobinsonJ 1973 Pathogenesis and prevention of tracheobronchial damage with suction procedures. Chest 64:284-290 Shapiro B, Harrison R, Trout C 1979 Humidity and aerosol therapy in clinical application of respiratory therapy. Year Book Publishers Inc, Chicago, 164 Stone K S, Bell S D, Preusser B A 1991 The effect of repeated endotracheal suctioning on arterial blood pressure. Applied Nursing Research 4 (4): 152-158 Thambrian A K, Ripley S H 1966 Observations on tracheal trauma following suction. An experimental study. British Journal of Anaesthesia 38:459-462 Wade J F 1982 Comprehensive respiratory care: physiology and technique, 3rd edn. The CV Mosby Co, St Louis Walsh J M, Vanderwart B S, Hoscheit D, Fahey PJ 1989 Unsuspected hemodynamic alterations during endotracheal suctioning. Chest 95 (1): 163-165 Wilhelm D, Doran J, Adams A, Indihar F. Prevention of endotracheal suction induced arterial desaturation with closed airway system catheter, Bethesda Lutheran Medical Center, Minnesota. (Unpublished) Young C 1984 Recommended guidelines for suction. Physiotherapy 70 (3) (March): 106-108.
(~ Longman Group UK Ltd 1993
Endotracheal suction for adult, non-headinjured, patients. A review of the literature A. Odell, A. Allder, R. Bayne, C. Everett, S. Scott, B. Still and S. West
T h e p r o c e d u r e for endotracheal suctioning was perceived as a problem by the m e m b e r s o f a quality circle in the intensive care unit (ICU). Endotracheal suction, w h e n p e r f o r m e d in the unit, a p p e a r e d to be carried out according to the nurses' experience and expertise, and had no formal research backing. A n extensive literature search was u n d e r t a k e n , and a f r a m e w o r k for endotracheal suction was formulated based on the available evidence. Some o f the aspects o f endotracheal suction r e p r e s e n t e d in the research evidence a p p e a r contradictory, and nurses must make a professional j u d g e m e n t about their suction technique based on the individual circumstances o f patients. T h e wealth o f evidence available r e g a r d i n g endotracheal suctioning allows nurses to m a k e an i n f o r m e d decision about care.
INTRODUCTION The muco-ciliary system in the airways, fully humidified and heated to 37°C, sweeps and traps inhaled particles that may harm the lungs (Guyton 1971). Endotracheal intubation forms an artificial airway that by-passes these normal processes, and inhibits the cough reflex. The respiratory tract is vulnerable to opportunist organisms, mucus secretion is often increased, and pneumocytes and surfactant are reduced (Ackerman 1985, Bostick & Wendelglass 1987). Patients with an endotracheal/tracheostomy
A. Odell, A. AIIder, R. Bsyne, C. Everett, S. Scott, B. Still, S. West Intensive Care Unit, Royal Berkshire Hospital, London Road, Reading, Berkshire RG1 5AN, UK (Requests for offprints to AO) Manuscript accepted 30 May 1993
274
tube in situ will require periodic endotracheal suctioning to help clear secretions, and prevent atelectasis (Bostick & Wendelglass 1987, Kuzenski 1978). Suctioning is a potentially hazardous procedure (Young 1984). Severe mucosal damage can result from tracheo-bronchial suctioning. Damage occurs by passing the catheter alone (Amikan et al 1972, Plum & Dunning 1956, Jung & Gottlieb 1976, Kuzenski 1978, Rux & Powaser 1979). Associated haemodynamic complications include; arterial hypoxaemia, cardiac arrythmias, hypotension and death (Walsh et al 1989, Boutros 1970, Gunderson et al 1991, Rosan & Hillard 1962, Clark et al 1990, Demers & Saklad 1973, Deppe et al 1990, Stone et al 1991). No consistency of endotracheal suction technique is found in ICUs nationwide. There is a lack of uniformity in suctioning procedures, and confusion over what constitutes proper technique (Bostick & Wendelglass 1987).
INTENSIVE AND CRITICAL CARE NURSING
Endotracheal suctioning should only be performed when necessary, and not as routine (Young 1984, Rosan & Hillard 1962). The patient should be assessed by the nurse prior to each suction, and one or more of the following found: rise in ventilator peak inspiratory pressure; secretions heard or visible during respiration; diminished breath sounds on auscultation; crepitations on auscultation. The following information from literature provides some basis for deciding on procedures for airway clearance.
275
Whistle tip and tri-flo catheters are not licensed in the UK. Single-hole catheters produce more trauma than multiple-hole catheters (Sackner et al 1973, Link et al 1976). The damage caused by multiple-hole catheters is due to the insertion of the catheter alone, and not by mucosal grabbing when suction is applied (Link et al 1976). Catheters should have a built-in valve to prevent a vacuum being applied to the trachea on insertion (Young 1984, Rosan & Hillard 1962).
Use of gloves STANDARD SUCTION PROCEDURE The catheter The catheter should be inserted gently into the trachea. The more vigorous the insertion, the more damage occurs 0 u n g et al 1976). The catheter should occlude no more than one half of the diameter of the endotracheal tube, to permit an inflow of oxygen during removal of alveolar gas while suctioning (Young 1984, Rosan et al 1962). A formula for calculating suction catheter size with endotracheal tubes greater than size 6Ch is: endotracheal tube size - 2 x 2. There are many types of suction catheter available on the market today (Young 1984), including the following types: Characterised by two triangular side-holes offset from the centre line and close to the bevelled catheter tip. - - aero-flo (bead tip) Four small round sideholes near the expanded tip. Bead tip catheters cause less damage but have less effective suctioning (Link et al 1976, Sackner et al 1973). Gentle-fit Four oval side-holes close to the tip. - - D u a l side hole Two large side-holes somewhat removed from the tip. - - Whistle tip Single side-hole. These catheters produce measurable mucosal damage beyond that related to catheter insertion (Link et al 1976).
--Tri-flo
-
Endotracheal suction should be performed under aseptic technique to reduce bacteriologic colonization and cross contamination in the trachea (Link et al 1976). There appears to be no evidence available on the wearing of gloves, either sterile or unsterile. Hospitals appear to vary in their policy from wearing unsterile gloves to double gloving. Wearing gloves is more effective than washing hands (Newsom & Rowland 1989).
The vacuum The higher the negative pressure applied through the catheter the greater the degree of ulceration, hypoxaemia, airway collapse and atelectasis (Rosan et al 1962, Plum & Dunning 1956, Sackner et al 1973, Brundstater & Muallem 1969, Thambrian & Ripley 1966, Rux & Powaser 1979). Higher negative pressures do not directly relate to the quantities of mucus extracted (Regan 1988). A negative pressure of 70-100mmHg (9.313.3kPa) is suggested (Thambrian & Ripley 1966, Kuzenski 1978), although clinically this may not be enough to extract secretions, therefore negative pressures up to 200mmHg (27kPa) may be needed.
-
Duration and continuity of suction The longer the duration of suctioning, the more mucosal damage and hypoxia occurs (Sackner et al 1973, Thambrian & Ripley 1966, Rosan & Hillard 1962, Brandstater & Muallem 1969, Boutros 1970).
276
INTENSIVE AND CRITICAL CARE NURSING
The duration of suctioning should last no more than 30sec, but ideally 15sec (Young 1984). Intermittent vacuum pressure causes less mucosal damage (Young 1984).
SUPPLEMENTARY SUCTION PROCEDURES The use of saline The common practice of instilling up to 10 ml of normal saline into the trachea, prior to suctioning, is abnormal (Ackerman 1985), and appears to have minimal or no benefit for clearing secretions (Ackerman 1985, Demers & Saklad 1973, Hanley et al 1978). Some studies suggest that a significantly greater amount of material is aspirated with the instillation of saline (Gray et al 1990), but this could be due to the cough elicited by this procedure. Instillation of saline down the endotracheal tube could interfere with alveolar capillary oxygen exchange, and give the patient the sensation of drowning (Wade 1982, Bostock & Wendelglass 1987). Hanley et al (1978), only recovered 10-20% of normal saline instilled into the trachea. Mucus and water are immiscible and occupy separate phases in vitro (Demers & Saklad 1973). However the instillation of saline produces a cough (Demers & Saklad 1973, Bostick & Wendelglass 1987, Downs 1989). To maintain a patent airway, the patient must firstly be adequately hydrated (Ackerman 1985). The u s e of heat and humidity should almost eliminate dried and tenacious secretions (Ackerman 1985, Hanley et al 1978, Shapiro et al 1983, Khan 1983). The practice of instilling bolus saline should be substituted for nebulised saline if secretions require loosening (Demers & Saklad 1973).
Hyperinflation/hyperventilation (Bag squeezing) Hyperinflation (bagging) is a way to provide artificial or hand ventilation to an intubated
patient to improve lung expansion, by using a Waters bag connected to an oxygen supply. Hyperventilation is performed by rhythmically squeezing the bag (MacKenzie 1981), while continually adjusting the rate, tidal volume and pressure in response to changes in the patient's lung compliance (Oh TE 1990). These breaths of unknown pressure and volume mimic sighing and yawning which helps expand the alveoli and prevent atetectasis by dislodging secretions. But hyperventilation with a rebreathing bag can cause the patient to feel dyspnoeic and uncomfortable (Lookinland & Appel 1991). High airway pressures during hyperventilation can result in hypotension, decrease in cardiac output and barotrauma. Hyperinflation with the rebreathing bag can help to prevent hypoxia by preventing atelectasis caused during suction (Boutrous 1970), therefore hyperventilation before and after endotracheal suction is recommended in certain instances (Lookinland & Appe11991, MacKenzie et al 1981). Hyperinflation of the lungs with 100% oxygen must be carried out with care, as rapid acid-base changes in the blood may affect the stability of severely ill patients. It should be attempted only by experienced staff (Young 1984). Where it is necessary to hyperventilate a patient, a pressure manometer should be used in the breathing circuit. The pressure produced by the bag should mimic the patients' ventilator peak inspiratory pressure.
Pre-oxygenation Hyperoxygenation is an increase in the concentration of inspired oxygen used to relieve hypoxaemia induced by endotracheal suctioning. Endotracheal suctioning causes a decrease in oxygen saturation by 25-30%, followed by a slow rise back to baseline over a 3 rain period. Oxygen consumption rises significantly after the open method of endotracheal suctioning (Walsh et al 1989). The oxygen supply/demand mismatch results in a drop in mixed venous oxygen content (Clark et al 1990). Bradycardias associated with endotracheal suction are not related to hypoxaemia, but are
I N T E N S I V E AND C R I T I C A L (;ARE N U R S I N G
Fig. 1 Closed auction system.
due to mechanical and neural stimulation which is vagally mediated (Gunderson et al 1991). Hyperoxygenation, in conjunction with hyperventilation at 100% oxygen, before, during and after suction causes arterial oxygen saturation to remain elevated (Lookinland & Appel 1991, Chulay & Graeber 1988). As a reliable measure of oxygen delivery, transcutaneous oximetry is especially valuable during procedures that may cause an abrupt change in PaO2. Although oxygen saturation measurements do not necessarily reflect large decreases in mixed venous oxygen content (Walsh et al 1989). Where possible, mixed venous saturation should be monitored.
Closed suction system T h e r e is now a closed suction system which is connected to the endotracheal tube o f a patient on mechanical ventilation, and can be left in place for 24h. Suctioning does not require disconnection from the ventilator, thus maintaining oxygen delivery and PEEP (positive end expiratory pressure). Closed suction systems improve oxygen saturation, decrease clinical signs of hypoxaemia and maintain levels o f positive end expiratory pressure (Demajo unpublished, Ritz et al 1986, Wilhelm et al, unpublished). T h e r e was no difference in oxygen saturation and oxygen tension between patients with the closed suction system and those with a conventional system where PEEP was below 10mmHg.
277
Where patients were on higher levels of PEEP, saturation was maintained with the closed suction system, but not the conventional method (Graziano et al 1987). Closed suction systems reduce the risk of environmental and cross-contamination, and do not expose the patient to increased risk of auto contamination (Cobley 1991). Scott et al (1990), found that colonisation of the trachea was significantly higher in the closed system of suction as opposed to the open system. However there was no significant difference in the incidence of nosocomial pneumonia between the two systems. Ritz et al 1986, found no significant difference in colonisation between the two methods.
CONCLUSION T h e r e is a great deal of published work that attempts to address the problems associated with endotracheal suction, and much o f it is contradictory. Nurses, who are accountable for their care, and therefore the suction that they perform, must disseminate the available information, and make an informed decision about how they will perform endotracheal suction. This decision must take into account the individuality of the patient concerned and his/her specific circumstances and condition. T o produce a rigid protocol for nurses does not allow them the flexibility to treat their patients as individuals. However each nurse providing intensive care must have the information to support the decisions that she or he makes.
References Ackerman M H 1985 The use of bolus normal saline instillations in artificial airways: is it useful or necessary? Heart and Lung 14 (5): 505-506 Amikan B, Landa J, WestJ, Sackner M 1972 Bronchofiberscopic observations of the tracheabronchial tree during intubation. American Review of Respiratory Disease 105:747-55 Bostick J, Wendelglass S T 1987 Normal saline instillation as part of the suctioning procedure: effects on PaO and amount of secretions. Heart and Lung 16 (5): 532-537
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