AMBUBAGGING AS A THERAPEUTIC TECHNIQUE: CLINICAL GUIDELINES M Barker BSc (Physiotherapy) Lecturer, Physiotherapy Department, U niversity o f the W itwatersrand C J Eales M Sc (Physiotherapy) Senior Lecturer, Physiotherapy Department, U niversity o f the W itwatersrand INTRODUCTION DEFINITION OF TERMS Compliance is measured in a mechani­ cally ventilated patient by recording tidal volume, airway pressure and positive end expiratory pressure (PEEP) and applying the formula of C = TV / Air Press - PEEP. Compliance may be described as either static or dynamic compliance. This distinc­ tion is made according to the particular airway pressure that is measured and used in the calculation of compliance. Using peak inspiratory airway pressure (PIA P) d yn am ic co m p lia n ce is given which reflects the resistance offered to lung inflation by both the airways and the elastic recoil of the lungs and chest wall. If plateau pressure is used then static compli­ ance would be calculated. The term "effec- • tive" is used when estimates of lung stiff­ ness are made with these calculations1. The technique of ambubagging, or sim­ ply bagging, involves the use of a manu­ ally operated self-inflating bag for artificial ventilation via a face mask, endo-tracheal tube or tracheostomy tube. This technique of manual hyperinfla­ tion was used initially in cardio-pulmo- nary resuscitation and for offering tempo­ rary v en tila tio n to intubated patients where mechanical ventilation was inter- .. j 2,11rupted Physiotherapists then became aware of the ambubag as a manual technique which could hyperinflate the lungs of intubated patients with the assumption that non­ functioning lung units could be recruited. Ambubagging gradually became an ac­ cepted physiotherapeutic technique and was extensively used in the treatment of ventilated patients. The continued use of this technique was based more on clinical experience than on scientific fact. During the period 1980 to 1992 a num­ ber of studies were conducted investigat­ r ing a scientific basis for the therapeutic use of ambubagging. This direction in the re­ search was necessary as previous studies on "bagging" had looked merely at the technique of using the bag during resusci­ tation and the physical properties of the manual resuscitation bag. PAST RESEARCH: RESULTS AND DISCUSSION The earliest of these studies (Hack I, Katz A, Eales C, 1980) investigated the airway pressure changes which take place during "bag squeezing"3. Using a pressure transducer attached to the patients cathe­ ter mount, the researchers took a very small sample (n=5) of intubated adult pa­ tients and graphically represented the pressure traces obtained during controlled ventilation versus those during bagging. From the graph paper, peak pressures of both controlled ventilation and bagging were interpreted as percentages by which the one mode was judged greater than the other. The greatest increase in airway pres­ sure occurred during bagging. From this the researchers concluded that by using the am bubag, higher inspiratory rates were achieved followed by greater expira­ tory flow rates and these mechanisms were comparable with those of an effective cough. This conclusion, however, cannot be m ade from the reported data. The authors were assuming that higher inspi­ ratory pressures would simulate a cough and lead to more effective secretion clear­ ance. Perhaps these high pressures re­ flected only the low pulmonary compli­ ance of their sample. Hack et al also dis­ cussed the indications and contra-indica- tions for the use of the ambubag . In 1982, research was conducted by physiotherapy students and staff mem­ bers of the University of the Witwaters­ rand to ascertain whether bagging had any effect on increasing the total static compli­ ance of ventilated patients4. The project was designed so that one group would be suctioned only and returned to the venti­ lator between insertions of the suction catheter and the other group would be bagged between suctions. When patients were bagged between insertions of the catheter, static lung compliance improved in 43% of cases. This increase reached its peak one hour after treatment. This sus­ tained increase in compliance was not demonstrated in the group who were suc- — SUMMARY A review of the literature relating to a m b u b a g g in g was undertaken. During the period 1980-1992, sev­ eral studies that were done investi­ gated a scientific basis for the use of b a g g in g and co nflicting evi­ dence was found. This may have been due to discrepancies in the measuring tools used as well as the divergence of the research designs by the investigators. Guidelines for the effective use of am bubagging as a therapeutic technique are set out. ■ tioned only. A continued interest in the therapeutics of the bag was now vested in the Depart­ ment of Physiotherapy at the University of the W itwatersrand. Further research ensued in 1986 by Coker et al who also used lung compliance as an indicator of the effect of bagging versus hyperinflation of the lungs by in­ creasing the tidal volume delivered from the ventilator5. Compliance improved in both groups with no significant difference shown between the two groups. This sug­ gests that it may be simply the hyperinfla­ tion that occurs which enables secretions to be mobilised rather than the high airway pressures or high flow rates achieved dur­ ing bagging. This was contrary to the belief which Hack and colleagues held after their research was published in 19803. Eales, in 1989, then set out to determine the effects of endotracheal suctioning and ambubagging on the arterial oxygen and carbon dioxide tensions6. Two experimen­ tal groups were used. Both groups were subjected to standard suctioning and bag­ ging protocols except that group 1 (n=18) were suctioned until clinically clear of se­ cretions and group 2 (n=12) were suc­ tioned six times only. Having taken arte­ rial blood gas samples before and fifteen minutes after treatment it was found that arterial oxygen tension (PaCh) dropped in both groups. This drop was more signifi­ cant in group 1 and related to the pro­ longed suctioning procedure. From this it was concluded that suctioning a patient six times only was optimal for the prevention of significant swings in PaC>2 levels. A r te r ia l c a r b o n d io x id e te n s io n s (PaCCh) were not significantly effected at all. This was an interesting observation, as Hack et al had postulated that bagging may create a drop in PaCC>2 levels. If the technique of ambubagging is per­ formed by clinicians skilled in its use, and if rate and depth of bagging are taken into consideration, PaCCh levels need not be affected and the hypoxic effects of suction­ ing can be minimised. Fisioterapie, Mei 1994 Deel 50 no 2 R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. ) Although ambubagging on a fractional inspired oxygen percentage of 1.0 can min­ imise the hypcxic effects of suctioning, Imle (1989) has stated that it is not the most effective way7. The preferred method to achieve this is suctioning through the catheter port without disconnecting the patient from the ventilator. The sampling procedures in most of the previous research on am bubagging in­ volved taking consecutive patients admit­ ted to a general ICU. This resulted in a sample which was not homogenous. Only recently have researchers in the field started to consider the effects of this tech­ nique on specific patient populations with the same pathologies. This was the case in a project conducted by Eales, Barker and Cubberley (1991) in the Cardio-thoracic ICU of the Johannes­ burg General hospital8. Here the effects of routinely bagging post-operative cardiac surgery patients was investigated. Having taken the effective lung compliance and full arterial blood gas profiles of each pa­ tient before and for ten minute intervals - up to one hour - post treatment, neither of the indices showed any benefit to this group o f patients. Contrasting this study is a project by Jones et al (1992) who again took 20 con­ secutive patients in a general ICU and bagged them to see how compliance and arterial saturations would be affected9. A broad division of the patient sample was made which states that ten patients had lung pathology and ten did not have lung pathology. Compliance increased in both of these groups with ambubagging and remained significantly so, up to two hours post treatment. Arterial saturations were not significantly affected by this treatment. CONCLUSIONS W hile providing arguments for and against the use of ambubagging, current research also appears to show discrepan­ cies in the measuring tools which were used with specific reference to compliance. The disagreement among the authors may also be related to the divergence of their research designs. This is seen in the lack o f stand ard isatio n of the patient populations which were used. Many pro­ jects have overlooked the value that posi­ tioning has on lung clearance and there­ fore its role in treating ventilated patients. Where positioning has been included in the research design, patients have demon­ strated marked im provements in static compliance10. Perhaps it is the combina­ tion of bagging and positioning in these studies which has a more favourable out­ come than each used in isolation. What is disconcerting is that despite the trends dem onstrated in the literature, clinical practice is still guided more by history and tradition. When considering the indications for bagging a patient, the physiotherapist should ask the following question: Can I satisfactorily match the ventilatory require­ ments o f the patient with the bag in terms o f respiratory rate , PEEP, FIO2 and tidal vol­ ume? Surely this question could be compe­ tently answered only once a thorough as­ sessment has been performed and once more information is available on the tech­ nique. GUIDELINES FOR AMBUBAGGING • As mechanical ventilation is known to cause p rogressive alveolar collapse mainly due to uneven gas distribution, the bag may be indicated to increase tidal breaths and to recruit atalectatic lung units. • In patients with thick, inspissated secre­ tions, the bag can drive warmed saline down the tracheo-bronchial tree and by creating turbulence in the airways, secre­ tions are better mobilised for endo-tra- cheal suctioning. • The bag can be used to facilitate or mimic a cough in sedated or paralysed patients and so promote movement and clearance of secretions. • Hypoxic effects of suctioning can be min­ imised with the bag. • The bag is also useful in offering tempo­ rary ventilation to patients who require moving or transport. In babies who are intubated with non-cuffed tubes, manipu­ lating a bag while moving the patient eg. for positioning becomes easier than deal­ ing with the heavy elephant tubing of the ventilator. • When weaning patients from long-term ventilation, the bag can be used as a "res­ piratory muscle endurance exerciser". Since the respiratory muscles lose a great proportion of their oxidative metabolism after only 72 hours of mechanical ventila­ tion, the physiotherapist can contract with the patient that for every two patient gen­ erated breaths he/she will receive an as­ sisted breath. This procedure can then re­ gain the endurance which these muscles have lost and which will be needed for successful extubation. • The bag had its origins in and is still used for resuscitation. Physiotherapists have failed to see that ambubagging is a technique with value when it is indicated. CONTRA-INDICATIONS • The patient who presents with very low pulmonary compliance and who is on pressure control ventilation. In these cases the ventilatory requirements can sel- domly be matched. • P a tie n ts w ith undrained pneum ot­ horaces, with a clamped inter costal drain or those with broncho-pleural fistulae are at risk of baro-trauma to the lungs because the operator is unaware of the inspiratory pressures created. • Haemodynamically unstable patients are also at risk for the use of this technique due to the cardio-vascular side effects of the bag. By creating a positive intra-tho- racic pressure, venous return decreases resulting in a decreased cardiac output. • When there is malfunctioning of the appa­ ratus i.e. the bag or the oxygen flow meter, there would be a risk of "under bagging" the patient creating hypoxaemia and other complications. All apparatus should be thoroughly checked before use. Ambubagging should not be regarded as an "all or none" technique which is routinely applicable but rather as a modality with its own set of indications, contra-indications and precautions for its use. These elements the literature has striven to highlight bu t only with limited success. Future research should concentrate strongly on investigating these specific aspects of ambubagging. REFERENCES 1. Comroe JH. Mechanics of breathing. In Com- roe JH, Forster RE, Dubois AB et al eds. The Lung. Chicago: Year Book Medical publish­ ers, 1974:162-163. 2. Eaton JM : Adult manual resuscitators. Br J Hosp Med 1984:31;67-70. 3. Hack I, Katz A, Eales C: Airway pressure changes during"bagsqueezing!'. S/1 J Physio­ therapy 1980:36(4)97-99. 4. Gamsu B, Stewart G. A comparative study of the effects of suction with bagging and suc­ tion only on secretion clearance. Unpub­ lished B.Sc.(physiotherapy) D issertation, University of the W itwatersrand, 1982. 5. C o k e r B L , G a r d e n F M . A c o m p a ri- son:Changes in lung compliance of mechani- cally ventilated patients follow ing chest physiotherapy, in which either the tidal vol­ ume of the ventilator was increased, or the "b a g g in g " technique w as used. U npub­ lished B .Sc.(P h ysioth erap y) d issertation, University of the W itwatersrand, 1986. 6. Eales CJ. The effects of suctioning and am­ bubagging on the partial pressure of oxygen and carbon dioxide in arterial blood. SA J Physiotherapy, 1980:45(2);53-55. 7. Imle PC, Klemic N. Methods of airway clear­ ance: Coughing and Suctioning. In: Macken­ zie CF, Imle PC, Ciesla N. Chest physiotherapy in the Intensive Care Unit. 2nd Edition Balti­ more, Williams and Wilkins 1989:170-178. 8. Eales CJ, Barker M, Cubberley NJ. An evalu­ ation of routine chest physiotherapy on post­ operative mechanically ventilated cardiac surgery patients. In press. 9. Jones AY, Hutchinson RC, Oh TE. Effects of bagging and percussion on total static com­ pliance of respiratory system. Physiotherapy; 1992:78(9)661-666. 10. Mackenzie CF, Shin B, Hadi F et al. Changes in total lung/thorax compliance following chest physiotherapy. Anesthesia and Analge­ sics 1980;59:207-210. 11. Ambu-Intemational. Scope and application of the Am bu Ruben Resuscitator Model C o m p a c t M ark II. S o n d re R in g v ej 49, D.K.2600 Glastrop, Copenhagen, Denmark. R ep ro du ce d by S ab in et G at ew ay u nd er li ce nc e gr an te d by th e P ub lis he r (d at ed 2 01 3. )