Citation for published version (APA): Leur, J. P. V. D. (2005). Clearance of bronchial secretions after major surgery Groningen: s.n.

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1 University of Groningen Clearance of bronchial secretions after major surgery Leur, Johannes Peter van de IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2005 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Leur, J. P. V. D. (2005). Clearance of bronchial secretions after major surgery Groningen: s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Chapter 2 Endotracheal suctioning versus minimally invasive airway suctioning in intubated patients: a prospective randomised controlled trial Johannes P. van de Leur 1, Jan Harm Zwaveling 2, Bert G. Loef 3, Cees P. van der Schans 1, 4. 1 Center for Rehabilitation, University Medical Center Groningen, The Netherlands 2 Department of General Surgery and Intensive Care, University Medical Center Groningen, The Netherlands 3 Department of Cardio-Thoracic Surgery and Intensive Care, University Medical Center Groningen, The Netherlands 4 University for Professional Education, Hanzehogeschool, Groningen, The Netherlands Published in: Intensive Care Medicine: 2003, 29, 3,

3 RES versus MIAS Abstract Study Objective: Endotracheal suctioning in intubated patients is routinely applied in most ICUs but may have negative side effects. We hypothesized that on-demand minimally invasive suctioning would have fewer side effects than routine deep endotracheal suctioning, and would be comparable in duration of intubation, length of stay in the ICU, and ICU mortality. Design: Randomised prospective clinical trial. Setting: Two ICUs at the University Medical Center Groningen, the Netherlands. Patients: Three hundred and eighty-three patients requiring endotracheal intubation for more than 24 hours. Interventions: Routine endotracheal suctioning (n=197) using a 49 cm suction catheter was compared with ondemand minimally invasive airway suctioning (n=186) using a suction catheter only 29 cm long. Measurements and results: No differences were found between the routine endotracheal suctioning group and the minimally invasive airway suctioning group in duration of intubation [median (range) 4 (1-75) versus 5 (1-101) days], ICU-stay [median (range) 8 (1-133) versus 7 (1-221) days], ICU mortality (15% versus 17%), and incidence of pulmonary infections (14% versus 13%). Suction-related adverse events occurred more frequently with RES interventions than with MIAS interventions; decreased saturation: 2.7% versus 2.0% (P=0.010); increased systolic blood pressure 24.5% versus 16.8% (P<0.001); increased pulse pressure rate 1.4% versus 0.9% (P=0.007); blood in mucus 3.3% versus 0.9% (P<0.001). Conclusions: This study demonstrated that minimally invasive airway suctioning in intubated ICU-patients had fewer side effects than routine deep endotracheal suctioning, without being inferior in terms of duration on intubation, length of stay, and mortality. Keywords: Airway suctioning - Mechanical ventilation Complications - Costs 32

4 Chapter 2 Introduction Endotracheal suctioning is an intervention to remove accumulated mucus from the endotracheal tube, trachea, and lower airways in patients who require intubation for mechanical ventilation. Intubation and mechanical ventilation impair the transport of mucus in the airways, and interfere with effective expectoration by coughing since the glottis cannot be closed. This has been the rationale behind the practice of applying routine endotracheal suctioning to these patients. Traditionally, endotracheal suctioning consists of disconnecting the patient from the ventilator, applying manual hyperinflation ( bagging ), inserting a suction catheter into the endotracheal tube and airways, and applying negative pressure to remove accumulated mucus. Between suction cycles, saline may be instilled to stimulate cough reflexes and dilute secretions [1]. It is assumed that routine endotracheal suctioning is beneficial. Prevention of pulmonary infections and the maintenance of airway patency are cited as possible benefits. However, there are few clinical trials to support these assumptions. On the other hand, routine endotracheal suctioning may have undesired adverse effects: cardiac arrhythmia was observed by Stone [2] during suctioning in 26 patients post-cardiac surgery. Aldkofer [3] reported a decrease in oxygen tension of 20 mmhg in 64 patients post-cardiac surgery. Eales [4] found a decrease in oxygen tension after suctioning of 12 mmhg. Brown [5] described an oxygen desaturation of more than 4% in a medical population of 22 patients. These adverse effects may be prevented by limiting the mechanical stimulant. Minimally invasive airway suctioning was developed as a suction procedure that was as non-invasive as possible, i.e., the suction catheter did not reach the trachea, no saline was instilled, no manual hyperinflation was applied, and suctioning was only performed when clinically indicated. We hypothesized that on-demand minimally invasive airway suctioning would be similar in ICU outcome as compared to routine endotracheal suctioning without its undesirable side effects. In this study we compared both suctioning protocols in a prospective randomised clinical trial looking for possible differences in duration of 33

5 RES versus MIAS intubation, ICU mortality, pulmonary infection incidence, duration of stay in the ICU, and the occurrence of suction-related adverse events. Materials and methods Over a 22-month period, all adult patients admitted with an endotracheal tube to a cardio-thoracic or a general surgical intensive care unit in our university hospital were considered for randomisation. Patients were not randomised if they: 1) had been intubated in a different institution; 2) required a closed suctioning system; 3) had undergone a lung transplant; or 4) had been given a non-regular endotracheal tube (double lumen, tracheostomy, wired tube). Group allocation to either routine endotracheal suctioning (RES) or minimally invasive airway suctioning (MIAS) was obtained by block randomisation with sealed envelopes. The Medical Ethics Committee of the hospital approved the study protocol and waived informed consent. Twenty-four hours after randomisation, all patients no longer requiring intubation, or who presented contra-indications or specific indications for endotracheal suction, including pulmonary oedema, pulmonary haemorrhage or atelectasis, were withdrawn from the study. All other patients were included in the final phase of the trial and were kept in the treatment arm they had been allocated to 24 hours earlier for the entire period that they required intubation. According to their clinical requirements, patients received sedation and partial ventilatory support with a heated humidifier. A proper level of sedation was achieved with a continuous infusion of midazolam (range 1-4 mg/h) and fentanil (range μg/h). Patients body positions were routinely changed by nurses. The RES and MIAS procedures were performed supine, and both are sterile procedures. RES was defined according to the American Association Respiratory Care guideline [1]. With a minimum frequency of three times a day, the patient was disconnected from the ventilator after a short course of pre-oxygenation with 100% oxygen. Manual hyperinflation was performed before a 49-cm (19.3-inch) CH12 catheter (Maersk Medical, Denmark) was introduced into the endotracheal tube and the airway. Then negative pressure ( mmhg) was applied for a maximum duration of 3 seconds. Manual hyperinflation was 34

6 Chapter 2 applied between suctioning cycles and sterile normal saline (10 ml) was instilled into the endotracheal tube if considered necessary by the nurse. After three cycles of hyperinflation, saline, and suctioning, the patient was reconnected to the ventilator. The nurse decided whether additional (i.e., in excess of three times a day) RES was needed on clinical grounds (audible or visible mucus retention in the tube, when mucus induced repetitive coughing, or in case of an acute decrease of oxygen saturation (below 90%)). MIAS was defined as follows; when considered clinically indicated (audible or visible retention of mucus in the endotracheal tube, repetitive coughing, or otherwise unexplained decreased oxygen saturation), the patient was disconnected from the ventilator without pre-oxygenation with 100% oxygen. Subsequently, a 29-cm (11.4-inch) CH12 suction catheter (Maersk Medical) was introduced into the endotracheal tube to which a negative pressure ( mmhg) was applied for a maximum duration of 3 seconds. Manual hyperinflation was avoided. No saline was instilled. The length of the catheter was chosen to exclude the possibility of the airway being touched by the catheter: it was too short to pass beyond the tip of the endotracheal tube. The suctioning procedure could be repeated if necessary, after which the patient was reconnected to the ventilator. RES and MIAS groups were compared for possible differences in the primary outcome parameter: duration of intubation. The secondary outcome parameters of the study were mortality, length of stay in the ICU, incidence of pulmonary infection, and incidence of suction-related adverse events. Pulmonary infection was defined using the Clinical Pulmonary Infection Score as described by Pugin [6]. A score 7 was considered as proof of pulmonary infection. The CPIS score included body temperature, leucocytes, X-ray findings, aspect of the mucus, and microbiological findings. The total score range was between Suction-related adverse events were defined as any of the following occurring within 10 minutes after suctioning: 1) a decrease in oxygen saturation measured by transcutaneous pulse-oxymetry of 5% or greater; 2) bradycardia of 40 beats per minute or less; 3) the occurrence of any new sustained cardiac arrhythmia; 4) the occurrence of more than 3 premature beats per minute; 5) a rise in systolic blood pressure of 10% or more above 35

7 RES versus MIAS baseline level; 6) an increase in pulse pressure rate (mean arterial blood pressure times heart rate) of 30% or more above baseline level; 7) the visual presence of new blood in the aspirated mucus. Data for the registration of adverse events were collected from the Marquette Medical Systems monitor using version 9A software. Vital signs (oxygen saturation, heart rate, systolic blood pressure, mean blood pressure) were measured at 1-minute intervals from the 2-minute period preceding the suctioning intervention until 10 minute after. To evaluate cost effectiveness, the net cost of the materials used in the two suctioning protocols and the mean time invested in carrying out one intervention for each protocol was calculated for 45 treatments for each of the interventions. The costs were extrapolated to the total number of interventions and to an annual basis. Patients allocated to MIAS were permitted treatment with RES if one of the following conditions was present after clinical observation by nurses and confirmation by medical staff: 1) an acute and persistent (> 1 minute) decrease in oxygen saturation below 90% for which no other cause than mucus retention could be found; 2) unilateral hypoventilation indicating unilateral bronchus obstruction; 3) persistent coughing causing asynchronised breathing on the ventilator and evident distress. RES in MIAS-allocated patients had to be approved by the physician on call. The patient was kept in the same treatment arm and MIAS was restarted after the event. All events were recorded and retrospectively analyzed. All protocol deviations (too low treatment frequency in the RES group and RES treatment in MIAS-allocated patients) were recorded. Statistical analysis Sample size calculation was based upon the assumption of bio-equivalence between both treatment arms, duration of intubation being the primary outcome parameter. We have used duration of intubation data from the 2 years previous to the start of the study. Because the distribution of the mean number of days with intubation was skewed to the right, a log transformation was performed to calculate sample size. A difference of 2 days or less was considered to be acceptable for bio-equivalence. The alpha was set at 0.05 and 36

8 Chapter 2 the beta at The minimum number of patients per group required to fulfil these criteria was 166. Data in the RES and MIAS groups were compared with chi-square tests for proportions, with the Students t-test for continuous data, and with a Mann- Whitney U-test for ordinal variables and in case of skewed distribution of the data. All analyses were performed on an intention-to-treat as well as a perprotocol basis. Results During the study period (September 1998-July 2000), 2,795 patients were admitted to the ICUs participating in the study. Of these patients, 2,254 were randomised to receive either RES or MIAS on admission. Finally, 383 patients (197 receiving RES and 186 receiving MIAS) could be included into the study since they still needed intubation 24 hours after admission and had no other reasons for exclusion. The reasons for non-randomisation and exclusion are listed in table 1. Table 1. Reasons for exclusion. Patient selection Admitted 2795 Not randomised < 18 years Not intubated Intubated at other hospital Non-regular tube type Closed suction system Lung transplant Missed randomisation within 24 hours Died before randomisation Other reasons Randomised 2254 Not included 1871 Intubation < 24 hours 1857 Pulmonary oedema 7 Atelectasis as admission diagnosis 7 Pulmonary haemorrhage 0 Included Patient characteristics and demographic data are presented in table 2. No significant differences between the patients in RES and MIAS groups were found. The median (min-max) number of suctioning treatments per patient in the RES group was 9 (0-453) and in the MIAS group 11 (0-638) (P=0.405). 37

9 RES versus MIAS Table 2. Patient characteristics and demographic data. RES MIAS P value Number of patients Gender % m / f 72 / / Age in years, mean (SD) 61 (16) 62 (16) Apache II score, median (min - max.) 12 (2-29) 13 (2-30) Smoking history, 60 / 7 / / 10 / (non / ex / smoker in % ) Previous history of pulmonary disease 82 / 14 / 4 80 / 18 / (none / moderate / severe in %) Emergency admission in % Trauma patients in % (n) 11.1 (22) 9.1 (17) Medical patients % (n) 7.1 (14) 4.8 (9) Surgical patients % (n) 81.8 (161) 86.1 (160) When data were analysed on an intention-to-treat basis, no differences were found between the patients in RES and MIAS in the primary outcome variable: duration of intubation [a median (range) of 4 (1-75) days and 5 (1-101) days, respectively]. Mortality (15% and 17%, respectively), length of stay in the ICU [median (range) of 8 (1-133) days and 7 (1-221) days, respectively], and incidence of pulmonary infections (14.2% and 12.9%, respectively) were also not significantly different between the two groups (table 3). We also calculated the number of pulmonary infections that occurred after 48 hours. There were 22 episodes in both groups, (incidence of 11.2% in RES and of 11.8% in MIAS). The incidence density was also comparable in both groups (8.20 in the RES group and 8.58 in the MIAS group). The number of reintubations was 24 in the RES group (12.2%) and 22 in the MIAS group (11.8%) (RES vs. MIAS P=0.915). 38

10 Chapter 2 Table 3. Results by intention-to-treat analysis of primary and secondary outcome parameters. RES (n=197) MIAS (n=186) P value Intubation duration in days, 4 (1-75) 5 (1-101) median (min-max) Mortality, % (n) 15.2 (30) 17.2 (32) ICU stay in days, median (min-max) 8 (1-133) 7 (1-221) Hospital stay in days, median (min-max) 23 (3-249) 24 (3-239) Infection, % (n) 14.2 (28) 12.9 (24) First day of infection, median (min-max) 8 (1-52) 6.5 (1-34) Suction-related adverse events were significantly less in the MIAS group: there were fewer episodes with desaturation, rise in systolic blood pressure, and rise in pulse pressure rate. Blood was also found significantly less frequently in mucus obtained with MIAS (table 4). Table 4. Results by intention-to-treat analysis of suction related adverse events per intervention. RES MIAS P value Number of interventions Decreased saturation (%) Bradycardia (%) Arrhythmia (%) Increased systolic blood pressure (%) <0.001 Increased pulse pressure rate (%) Blood in mucus (%) <0.001 Arrhythmia was seen more frequently in the group receiving MIAS; arrhythmia was limited to the occurrence of premature beats: no sustained arrhythmia was observed. Bradycardia had a low incidence and was not significantly different between the group receiving routine endotracheal suctioning and the group receiving minimally invasive airway suctioning. Treatment was withheld from some RES patients. The main reason for not administering RES to RES-allocated patients a minimum of 3 times a day was the perceived absence of a clinical indication for suctioning by the nursing staff. In RES, those patients (n=63) who had been under-treated with regard to frequency of treatment had a significantly higher median duration of intubation (3 vs 11 days; P<0.001), a higher mortality (10% vs 25%; P=0.006), 39

11 RES versus MIAS and had a higher incidence of infections (9% vs 24%; P=0.008). A substantial number of patients allocated to MIAS were given incidental RES treatment: according to the nurse, mucus could not be removed effectively with MIAS alone. In MIAS, the patients (n=105) who incidentally underwent RES treatment had a significantly higher median duration of intubation (2 vs 6 days; P<0.001), and had a higher incidence of pulmonary infection (6% vs 18%; P=0.016). In both treatment arms, deviations from protocol tended to occur in patients with higher median intubation duration. There was no difference in the APACHE II scores between patients with protocol deviations and patients without protocol deviations [median (range) 13 (4-29) vs 12 (2-28) in the RES group (P= 0.058) nor in the MIAS group 14 (2-30) vs 13 (2-29) (P=0.586)]. The number of deviations in the MIAS group was 728 of the total number of 7,395 interventions. The reasons for deviations (under-treatment) in RES were as follows: no indication for intervention (94%), stressed patient (3%), other or no reason given (2%), and decreased saturation (1%). The reasons for deviations (RES procedures in MIAS) were: signs of mucus retention (69%), other or no reason given (18%), decreased saturation (12%), and stressed patient (1%). MIAS intervention was a less time-consuming intervention with less material being used, although the custom-made catheter was more expensive. The average time investment was 8 minutes and 42 seconds for a RES intervention and 3 minutes and 55 seconds for a MIAS intervention. The average cost for materials (sterile cover, facemask, sterile gloves, saline, connecting tube, suction catheter, syringe) used per treatment in routine endotracheal suctioning was 3.43 and in minimally invasive airway suctioning was Even after a sensitivity analysis of 20% of the costs involved, MIAS remained less expensive than RES. When compared to the RES protocol the MIAS protocol could provide a cost saving of 1.63 per intervention. The total difference in cost in favour of the MIAS protocol amounted to 14,914 per year based on 9,150 endotracheal suction procedures per year in our study population. 40

12 Chapter 2 Table 5. Results by per-protocol analysis of primary and secondary outcome parameters. Patients correctly Patients correctly P value treated according to the RES protocol (n=134) treated according to the MIAS protocol (n=81) Intubation duration in days, 3 (1-43) 2 (1-33) median (min-max) Mortality, % (n) 9.1 (11) 9.5 (7) ICU stay in days, 5 (1-50) 4 (1-33) median (min-max) Hospital stay in days, 20 (4-201) 17.5 (3-239) median (min-max) Infection, % (n) 8.3 (10) 5.4 (4) When patients were analysed on a per-protocol basis (table 5), the median duration of intubation was significantly less in patients in the MIAS group who were correctly treated according to the MIAS protocol as compared to patients correctly treated in the RES group [a median (range) of 2 (1-33) days versus a median (range) of 3 (1-43) days in the RES group] (P=0.018). No difference in mortality was apparent. Patients correctly treated with MIAS had a significantly shorter stay in the ICU than patients correctly treated with RES [a median (range) of 4 (1-33) days versus a median (range) of 5 (1-50) days] (P=0.011). No differences in the incidence of pulmonary infection were found. In addition, in the per-protocol analysis comparing the actually performed procedures, desaturation, rise in systolic blood pressure, and rise in pulse pressure rate were significantly less frequent in interventions effectively performed according to the MIAS protocol as compared to interventions performed according to the RES protocol. The presence of blood in the mucus was again less frequent in interventions according to the MIAS protocol as compared to interventions according to the RES protocol (Table 6). As in the intention-to-treat analysis, premature beats were more frequent in interventions performed according to minimally invasive airway suctioning as compared to interventions performed according to routine endotracheal suctioning. 41

13 RES versus MIAS Table 6. Results by per-protocol analysis of suction-related adverse events per type of intervention actually performed. Interventions performed according to RES protocol Interventions performed according to MIAS protocol P value Total number of interventions 8555* 6631# Decreased saturation (%) <0.001 Bradycardia (%) Arrhythmia (%) <0.001 Increased systolic blood pressure (%) <0.001 Increased pulse pressure rate (%) Blood in mucus (%) <0.001 * The number of interventions is higher in the RES group in the per-protocol analysis (8555) as compared to the intention-to-treat analysis (7827) because some interventions in the MIAS-allocated patients were actually performed according to the RES protocol. # For the same reason the number of interventions in the MIAS group is lower in the per-protocol analysis (6631) as compared to the intention to treat analysis (7395). Discussion The results of our study show that MIAS was associated with fewer suctionrelated adverse events and at least was equal in terms of duration of intubation, mortality and pulmonary infection incidence compared with RES. The pathophysiologic mechanism underlying suction related adverse events was probably multifactorial. Hypoxia based on alveolar derecruitment may had been a common denominator. Oxygen desaturation would have been most prominent in patients with low functional residual capacities, elevated mean airway pressures, and high levels of PEEP. The use of large-bore suction catheters and high levels of negative pressure applied to the airway would have increased the likelihood of oxygen desaturation. Mucosal bleeding may have been the effect of direct damage due to catheter introduced into the airway, but could have been also related to the negative pressure applied and to the technique of suctioning. The MIAS procedure which we evaluated in this study was likely to be less effective in removing secretions from the lower airways as compared to the standard procedure. This was supported by the fact that the main reasons for treating MIAS-allocated patients with suctioning according to RES protocol were signs of mucus retention and decreased saturation. However, this 42

14 Chapter 2 appeared to have no effect on mortality, duration of intubation, and ICU stay. This suggested that, in general, the minimally invasive procedure is sufficient. However, in specific patients with large amounts of secretions in the lower airways the more rigorous conventional procedure may still be required. The incidence of most suction-related adverse events in the MIAS group is lower than in the RES group. RES is a more invasive procedure and may induce stress, which may contribute to increased systolic blood pressure and pulse pressure rates, which indeed occurred more frequently in the RES group than in the MIAS group. Previously, smaller studies found circumstantial evidence for induced stress due to suctioning [2,7]. Suctioning in the lower airways probably also explained the higher incidence of clinically detected blood in aspirated mucus in the conventional RES group than in the MIAS group. Although we had no indication that systematic differences in negative pressure between both suctioning procedures occurred, this may theoretically explain the differences in the incidence of blood in the aspirated mucus. Unlike all other suction-related adverse events, the incidence of suctionrelated arrhythmia was higher in the MIAS group than in the conventional RES group. Our study does not offer any clues whythis should be so. Suction-related adverse events appeared to have no effect on duration of intubation, ICU mortality, ICU stay, hospital stay, and first day of pulmonary infection, as there was no difference between the two groups in the intentionto-treat analysis. Suction-related adverse events could therefore be less detrimental for the patient than expected; alternatively the incidence of suction-related adverse events may have been too low to have measurable long-term effects. In the per-protocol analysis differences were found in other parameters: duration of intubation and ICU stay were longer in the RES group than in the MIAS group. Differences in outcome between the per-protocol analysis and the intention-to-treat analysis were probably due to selection bias. The number of patients in whom a protocol deviation occurred, and who, consequently, were excluded from the per-protocol analysis, was much higher in the MIAS group than in the RES group. Since both groups excluded patients with a longer duration of intubation and ICU stay, selection bias would explain why the 43

15 RES versus MIAS duration of intubation and ICU stay was significantly higher in the RES group than in the MIAS group. No difference in incidence of pulmonary infection between the two groups was found, although our study was not primarily designed to investigate the difference in pulmonary infection between RES and MIAS. LeFrock [8] found in a group of 68 patients that 12% developed bacteraemia after endotracheal suctioning. This was probably caused by transport of bacteria from the upper to the lower airways. Hagler [9] confirms transport of bacteria due to suctioning. In an in vitro study, this author found that insertion of a suction catheter in an endotracheal tube and instillation of normal saline dislodges considerable amounts of viable bacterial colonies from endotracheal tubes that could potentially be transported to the lower airways. Suctioning according to the RES procedure, but not the MIAS procedure, included deep suctioning and instillation of saline. Since we found no difference in the incidence of pulmonary infections between the groups, the clinical relevance of Hagler s and LeFrock s findings was probably limited. Cost effectiveness was in favour of the MIAS intervention because fewer sterile-paper covers and less saline was used and less time was invested by nursing staff and/or respiratory physiotherapists. Cost savings when using the MIAS intervention are limited due to the small difference in materials used and time invested. Additional expenses (antibiotics and use of hospital resources) were not taken into account due to the fact that there were no differences in infection rates, duration of ventilation, ICU stay or hospital stay. The incidence of suction-related adverse events in the group receiving RES was lower than we expected. Many publications have focused on adverse effects related to endotracheal suctioning and suggested that adverse events arise frequently. Previous studies [3-5, 10-12] described suction-related decreases of oxygen tension and desaturation. However, the incidence of desaturation was not reported in these studies. The results of our study showed for the first time that the incidence of suction-related decreased saturation was low (2.7% in the RES group and 2% in the MIAS group). The incidence of oxygen desaturation was significantly lower in the MIAS groups as compared to the RES group. This difference could be explained by the fact that the minimal number of cycles 44

16 Chapter 2 during suctioning according to RES was three cycles while in case of MIAS this was only one. The whole minimally invasive airway suctioning procedure was therefore shorter as compared to the routine endotracheal suctioning procedure. However, the incidence difference of oxygen desaturation was only 0.7%. We considered this difference as less clinically relevant. The incidence of suction-related arrhythmia, 6.6% in our study, was much lower than in a previous study by Stone et al. [13], who reported an incidence of arrhythmia of 81% in patients after open-heart surgery. It must be noted that Stone s study included only 26 patients and that the estimation of the incidence of arrhythmia was therefore less reliable than ours, which was based on 197 patients and 7,800 RES interventions. Obviously, the results of our study can only be applied to the type of patients included (i.e., without ARDS or atelectasis as admission diagnosis). The reason for excluding patients with ARDS was that we considered that these patients require a constant positive pressure from the mechanical ventilator to maintain adequate oxygenation. It was therefore considered unfavourable to disconnect these patients from the mechanical ventilator for suctioning (either RES or MIAS). Patients with an atelectasis, at the time of admission, were excluded because in our opinion they required selective deep suctioning in order to remove accumulated mucus. We believed that inclusion in this study would have denied these patients optimal treatment for their disease or condition. We were well aware of the fact that exclusion of this type of patient may have reduced the number of suction-related adverse events in our study population, underestimating the general risk of this procedure. It should be formally mentioned that for our study a modified (i.e., nonstandard) catheter was used for the MIAS group, which by itself precludes immediate general adoption of a minimally invasive airway suctioning strategy. A further potential limitation of our study was the substantial number of protocol deviations. One or more protocol deviations occurred in 32% of the patients in the RES group and in 56.5% of the patients in the MIAS group. However, the number of protocol deviations per patient was low: in 68.3% of the patients in the MIAS group, less than 10% of the interventions were contrary to the protocol. To summarise, protocol deviations were common on a patient 45

17 RES versus MIAS level, but the number of deviations per patient was low. In the conventional RES group this proportion was 81.2%. The most frequently reported reason (94%) for a protocol deviation in the RES group was no indication for suctioning. The minimum suctioning frequency of three times per day was not met in these patients. The most important reason (69%) for protocol deviations in the MIAS group was visible or audible presence of mucus. In these cases RES was used instead of the prescribed MIAS. It appeared that the nursing staff considered MIAS as inadequate and preferred the RES intervention. MIAS could have resulted in a greater accumulation of secretions if it had been applied without deviations (RES instead of MIAS). Potentially, this accumulation of secretions could have resulted in a higher incidence of pulmonary infections in the MIAS group. However, this is not supported by the per protocol analysis. In contrast, it has also been suggested that deep suctioning, like in case of RES, is a risk factor for the development of infections. This could theoretically have contributed to a higher incidence of pulmonary infections in case of suctioning according to RES than according to MIAS, but no differences were found. The results of our study suggest that the use of minimally invasive airway suctioning instead of routine endotracheal deep suctioning in patients with a ventilation duration of more than 24 hours, caused a lower incidence of suctionrelated adverse events, and was equivalent in terms of duration of intubation, ICU mortality, pulmonary infection incidence, duration of ICU stay, and hospital stay. However, suction-related adverse events were generally mild, even with deep suctioning, if proper precautions were taken. As a consequence, our data do not support the general adoption of a MIAS strategy for mechanically ventilated ICU-patients; they merely question the added benefit of repeated deep suctioning. Further studies are needed to investigate whether the reduction of the duration of intubation and stay in the ICU, observed in the MIAS group with a per-protocol analysis, is borne out in a proper intention-to treat format. 46

18 Chapter 2 Reference list 1 Branson RD, Campbell RS, Chatburn RL, Covington J: Endotracheal suctioning of mechanically ventilated adults and children with artificial airways. American Association Respiratory Care Clinical Practice Guideline. Respiratory Care (1993) 38: Stone KS, Talaganis SA, Preusser B, Gonyon DS: Effect of lung hyperinflation and endotracheal suctioning on heart rate and rhythm in patients after coronary artery bypass graft surgery. Heart and Lung (1991) 20: Adlkofer RM, Powaser M: The effect of endotracheal suctioning on arterial blood gases in patients after cardiac surgery. Heart and Lung (1978) 7: Eales CJ. The effects of suctioning and ambubagging on the partial pressure of oxygen and carbon dioxide in arterial blood. South African Journal of Physiotherapy (1989) 45: Brown SE, Stansbury DW, Merrill EJ: Prevention of suctioning-related arterial oxygen desaturation. Comparison of off-ventilator and on-ventilator suctioning. Chest (1983) 83: Pugin J, Auckenthaler R, Mili N, Janssens JP, Daniel P, Sutter P: Diagnosis of ventilator associated pneumonia by bacteriologic analysis of bronchoscopic and nonbronchoscopic "blind" bronchoalveolar lavage fluid. American Review of Respiratory Disease (1991) 143: Clark AP, Winslow EH, Tyler DO, White KM: Effects of endotracheal suctioning on mixed venous oxygen saturation and heart rate in critically ill adults. Heart and Lung (1990) 19: LeFrock JL, Klainer AS, Wu WH, Turndorf H: Transient bacteremia associated with nasotracheal suctioning. Journal of American Medical Association (1976) 236: Hagler DA, Traver GA: Endotracheal saline and suction catheters: sources of lower airway contamination. American Journal of Critical Care (1994) 3: Boutros AR: Arterial blood oxygenation during and after endotracheal suctioning in the apneic patient. Anesthesiology (1970) 32: Berman IR, Stahl WM: Prevention of hypoxic complications during endotracheal suctioning. Surgery (1968) 63: Ritz R: Hypoxemia and arrhythmias due to endotracheal suction. Schweizerische Medizinische Wochenschrift (1973) 103: Stone KS, Bell SD, Preusser BA: The effect of repeated endotracheal suctioning on arterial blood pressure. Applied Nursing Research (1991) 4:

19 RES versus MIAS 48