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Background: Mitral valve disease patients have reduced lung compliance due to the pathology of disease. In addition to it anesthesia, cardiopulmonary bypass and mechanical ventilation further reduces lung compliance. Endotracheal suctioning has been reported to produce decreased lung compliance and it is still widely practiced. Therefore, aim of our study is to investigate the effect of endotracheal suctioning and manual hyperinflation (MHI) on dynamic lung compliance (Cdyn) in mechanically ventilated mitral valve replacement surgery patients.
Design: prospective, pre test post test control group, interventional, randomized, single blinded study.
Intervention: four set of eight compression of MHI procedure at 10-12 breaths/min with 2:1 ratio at 40 cmH2O. Tracheal suctioning in experimental group was performed for maximum of 15 sec after every eight compression of MHI.
Measurement: Cdyn, heart rate (HR), PCO2, PaO2 and SaO2 were measured in thirty mechanically ventilated patients at five minutes before, 1 minute (immediately) after and 30 min after (for experimental group only) an intervention.
Result: No significant (p>0.05) difference was observed in the between group analyses for Cdyn (p=0.841), HR (p=0.846), PCO2 (p=0.324), PaO2 (p=0.450) and SaO2 (p=0.718) immediately after intervention. Within group analyses showed a non significant increase in Cdyn (p=0.174) and SaO2 (p=0.859) and non significant decrease in PCO2 (p=0.7) and PaO2 (p=1.0) immediately after intervention in experimental group whereas, a significant increase in Cdyn (p=0.001), HR (p=0.0001) and PaO2 (p=0.031) was noted in control group immediately after intervention and a non significant increase in SaO2 (p=0.358) and non significant decrease in PCO2 (p= 0.348) immediately after intervention.
Conclusion: Manual hyperinflation when performed with and without suction with a PIP of 40 cmH2O on group of post mitral valve replacement surgery patients, no deleterious effect on arterial blood gas value and dynamic lung compliance were found. Therefore, this study suggests that endotracheal suctioning in conjunction with manual hyperinflation does not produce any deleterious changes in dynamic lung compliance and oxygenation in mechanically ventilated mitral valve replacement surgery patients.
Mitral valve disease is frequently associated with various pathological changes of respiratory function such as decreased lung volumes, diffusing capacity and decreased static and dynamic lung compliance.1
Chronic disease is especially associated with increased pulmonary vascular pressure, resulting in development of pulmonary artery hypertension (PAH) which invariable reduces the lung compliance and increases airway resistance.2,3 During cardiac surgery, the use of general anesthesia and muscle paralysis, mechanical ventilation, thoracotomy and cardiopulmonary bypass further substantially influence lung function.1 General anesthesia has been reported to cause depression of mucociliary functioning resulting in decreased mucus clearance in perioperative period.4 Cardiopulmonary bypass has also been reported to produce a significant decrease in dynamic and static lung compliance during perioperative and postoperative period.5,6 Moreover, mechanically ventilated patients are incapable of removing secretion from their airway as the glottis cannot be closed for an effective cough. This has been the rationale behind the practice of applying routine endotracheal suctioning to these patients.7 All the above factors substantially decrease the lung compliance. Although endotracheal suctioning has been reported to have many adverse effect it is still widely practiced in intubated patients. The disconnection of patient from the ventilator during open endotracheal suctioning allows airway pressure to fall to atmospheric pressure7,8 which invariably reduces lung volume resulting in further decreased lung compliance.9 In mechanically ventilated patients suction is always performed after chest physiotherapy session and/or after manual hyperinflation so as to clear larger amount of secretion from airways. Both manual hyperinflation and suctioning produces an alteration in respiratory mechanics in addition to the effects of cardiopulmonary bypass and anesthesia in mechanically ventilated patients. The combined effects of both the techniques on static lung compliance have been well documented in mechanically ventilated patients. Some studies suggest a decrease in static lung compliance after performing endotracheal suctioning8,10 and manual hyperinflation12 while others suggests an increase in static lung compliance.4,11 In contrast to static lung compliance very less studies can be found on dynamic lung compliance. Most of the studies on dynamic lung compliance have been conducted on pediatric population.10,12 Studies suggest that there is decrease in dynamic lung compliance after suctioning in pediatric population.10,13 Only few studies have been reported on the effect of suctioning on dynamic lung compliance in adults and even lesser studies are found on combined effect of manual hyperinflation and endotracheal suction. There is almost no study can be found on effect of endotracheal suction and manual hyperinflation on mitral valve replacement surgery patients. Therefore, the questions which storms our brain is whether, suction and manual hyperinflation improves or detiorates the lung compliance in patient with mitral valve disease who is already having reduced lung compliance due to disease, which is further reduced during anesthesia, cardiopulmonary bypass and mechanical ventilation? Therefore, the aim of the study is to determine the effect of endotracheal suctioning on dynamic lung compliance after manual hyperinflation in mitral valve replacement surgery patients.
MATERIALS AND METHOD
Approval for the study was obtained from the Institutional Review Board of the respective university. A total sample of 30 subjects of mitral valve replacement surgery patients were selected for the study. They were selected on the basis of inclusion and exclusion criteria. The inclusion criterion consists of post mitral valve replacement surgery patients, Intubated and mechanically ventilated patient with continuous mandatory ventilation (CMV) mode, Age group 20-50 years. Subjects with arterial oxygen saturation ≤ 90%, associated lung pathology e.g. COPD and acute respiratory distress syndrome (ARDS)11, Unstable blood pressure11 (MAP < 75 mmHg), requiring high respiratory support11 (FiO2 ≥0.7 and PEEP >10cmH2O), Air leakage14, Severe bronchospasm.14 were excluded. A day before the surgery patient was approached and participants were explained about the purpose and nature of the study and an informed consent was obtained. All the patients recruited in the study were ventilated with SEIMEN servo ventilator 300 on volume control mode with FiO2 of 50% after surgery.
The study was a prospective, pre test post test control group, interventional, randomized, single blinded study.
Informed consent was obtained preoperatively from a population of patients scheduled for mitral valve replacement surgery (MVR). 3-4 hrs after a standardized surgical procedure a detailed evaluation was performed on the mechanically ventilated mitral valve replacement surgery patients. Then the subjects were selected according to inclusion and exclusion criteria. The selected patients were then randomized into two groups, group-A (MHI+Suctioning) or Group-B (MHI), equally. On the day of measurement each patient were positioned in supine and undisturbed for 15 minutes prior to data collection. All sterile measures were taken care before touching the patient. Five minutes before the intervention the first data (baseline) was collected. At the end of five minutes relevant intervention, according to the group assigned, was delivered to the patient. Group-A patients were delivered manual hyperinflation along with suctioning according to standard protocol using two litre sterile ShineBall® (Taiwan) self inflating resuscitator bag and sterile FG-12 suction catheter respectively. The suction pressure was set to -150 mmHg. Each pass of suction catheter was limited to maximum of 15 seconds. Group-B patients only received manual hyperinflation using two litre sterile resuscitator bag as an intervention. After delivering eight compression patient was reconnected to ventilator for one minute then again eight compression was delivered. This was repeated for four times. Second data was collected One minute after the completion of respective intervention. After collecting the second data control group (Group-B) patients were performed endotracheal suctioning to remove the collected secretion in trachea. The third data was collected 30 minutes after the intervention in experimental group only. Third data (30 minutes after intervention) cannot be collected for group-B patients as the sample got contaminated due to the suctioning procedure performed after collecting second data (1 minute after intervention).
Group A: Manual Hyperinflation and Endotracheal Suctioning
Four sets of eight bag compressions, connected to 100% oxygen (15 L/min), with both hands were delivered during each manual hyperinflation session. The rate of inflation was 10-12 breaths/minute with inspiratory:expiratory ratio of 2:1. A pressure manometer was attached with the self inflating resuscitator bag and each compression was delivered to a peak airway pressure of 40 cmH2O, aiming to maximize lung volume and followed by a two second inspiratory pause and then a quick release of the bag to enhance the expiratory flow rate. Tracheal suctioning was applied after delivery of eight manual hyperinflation breaths. The duration of each pass of suction was limited to 15 seconds. Tracheal suctioning was performed once per set of eight bag compression.
Group B: Manual Hyperinflation
Four sets of eight bag compressions, connected to 100% oxygen (15 L/min), with both hands were delivered during each manual hyperinflation session. The rate of inflation was 10-12 breaths/minute with inspiratory:expiratory ratio of 2:1. A pressure manometer was attached with the self inflating resuscitator bag and each compression was delivered to a peak airway pressure of 40 cmH2O, aiming to maximize lung volume and followed by a two second inspiratory pause and then a quick release of the bag to enhance the expiratory flow rate. Patient was reconnected to ventilator after every eight bag compression.
The entire data was collected during the evening hours of the zero post operative day of surgery. The complete data collection was done by a study blinded person. Data was recorded 5 minutes before, 1 minute after, and 30 minutes after (for experimental group only) the standard intervention protocol.
The complete data was analyzed using SPSS 15.0 for windows® software. First a detailed description was obtained using descriptive statistics and then the data was analyzed to find any baseline differences. An Independent t-Test was used to analyze the between group differences. A repeated measure ANOVA was performed for analysis of within subject differences. The repeated measure of time was baseline, one minute after and 30 min post intervention. The repeated measure test was applied only for experimental group as their was no post 30 min data for control group. Bonferroni's correction was applied for multiple comparisons. The paired t-test was used for analysis of within subject changes between baseline and one minute post (immediately) intervention in control group.
A total sample of thirty subjects (n=30) with age group between 20-50 years with mitral valve replacement surgery was enrolled in the study.
Table Demographic data.
Mean ± Std. Deviation (SD)
MHI + Suction
29.73 ± 9.38
31.07 ± 10.33
28.40 ± 8.47
1.58 ± 0.06
58.67 ± 5.86
157.53 ± 5.70
43.30 ± 7.3
42.40 ± 5.88
44.20 ± 8.64
17.275 ± 2.46
3.80 ± 0.49
3.68 ± 0.63
Cardiopulmonary bypass time (minutes)
82.10 ± 28.04
88.67 ± 31.55
75.53 ± 23.26
The demographic data and baseline difference in the data for all the subjects are mentioned in table1 below. There were no statistically significant differences found between the baseline data of two groups. The sample contain more number of women 66.67% (n=20) than men 33.33% (n=10). Out of total subjects 36.67% (n=11) of patients were replaced with bioprosthetic mitral valve and remaining 63.33% (n=19) of subjects were replaced with mechanical mitral valve.
Between group comparisons showed no statistically significant (p>0.05) difference between the variables of two groups (MHI+Suctioning and MHI group). The dynamic compliance showed a non significant (p=0.841) improvement immediately (1 minute) after intervention (p=0.841). Heart rate (p=0.85), PCO2 (p=0.32), PaO2 (p=0.45) and SaO2 (p=0.71) also showed non significant (p>0.05) change in between group analyses in the immediate post intervention.
In experimental group (MHI + Suctioning), within group analysis showed a non-significant (p= 0.174) Increase (4.97%) in dynamic lung compliance from baseline (25.575 ± 4.873) (Mean ±SD) to 1 min post (26.842 ±5.582) intervention data. 1 min post intervention data compared with 30 min post (26.59 ±4.839) intervention data, it also resulted in non-significant (p=1.0) decrease (0.93%) in dynamic lung compliance. Similarly baseline data with 30 min post intervention data also showed non significant (p=0.063) improvement (3.989%) in dynamic lung compliance. Control group (MHI), showed a significant (p=0.001) increase (5.1%) in dynamic lung compliance from baseline (25.962 ± 6.250) to 1 minute post (27.286 ± 6.379) intervention.
Table Between group comparison
Mean ± SD
Mean ± SD
Table Within group comparison of experimental ( MHI+Suctioning) group
Post hoc significance (p)
BL to 1 min
1 min to 30m
BL to 30 min
25.575 ± 4.87
26.842 ± 5.58
26.59 ± 4.84
34.17 ± 5.72
33.167 ± 4.59
32.99 ± 4.45
99.41 ± 0.52
99.553 ± 0.35
99.43 ± 0.58
Heart rate showed a significant (p=0.0001) increase (8.018%) from baseline (108.53 ±18.197) to 1 mim post intervention (117.20 ±18.895) in experimental (MHI + suctioning) group. baseline data with 30 min post (106.60 ±17.484) intervention data, resulted in non-significant (p=0.427) decrease (1.75%) in heart rate. similarly 1 minute post intervention data with 30 min post intervention data resulted in significant (p=0.000) decrease (9.04%) in heart rate. Control (MHI) group showed significant (p=0.000) increase 6.03%) in heart rate.
In the experimental (MHI + suctioning) group, within group analysis, showed a non-significant (p=0.70) decrease (2.926%) in PCO2 between baseline (34.167 ± 5.717) to 1 min post intervention (33.167 ± 4.596) data. 1 min post intervention data compared with 30 min post intervention (32.99 ± 4.448) data, also showed a non-significant (p=0.467) decrease (3.436%) in PCO2. Where as comparison between baseline data with 30 min post intervention data also resulted in non-significant (p=1.0) decrease (0.525%) in PCO2. Control (MHI) group also showed non-significant (p=0.348) decrease (1.4%) in PCO2 between baseline (34.16 ± 5.717) and 1 min post (33.167 ± 4.596 ) intervention data.
A non-significant (p=0.70) decrease (2.93%) in PCO2 was found between baseline (34.167 ± 5.717) to 1 min post intervention (33.167 ± 4.596) data in experimental group. 1 min post intervention data compared with 30 min post intervention (32.99 ± 4.448) data also showed a non-significant (p=0.467) decrease (3.45%) in PCO2. Comparison between baseline data and 30 min post intervention data also resulted in non-significant (p=1.0) decrease (0.52%) in PCO2.
Table Within group comparison of control (MHI) group
Figure Comparison of dynamic lung compliance
In control (MHI) group comparison between baseline and 1 min post intervention data resulted in non-significant (p=0.348) decrease(1.4%) in PCO2 from 34.16 ± 5.717 to 33.167 ± 4.596 was found respectively.
Figure Comparison of heart rate
Experimental group in within group analysis, showed a non-significant (p=1.0) decrease (1.51%) in PaO2 baseline (217.53 ± 24.462) to 1 min post intervention (214.20 ± 36.848) data. 1 min post intervention data compared with 30 min post(219.47 ± 29.63) intervention data also resulted in non-significant (p=0.803) increase (2.4%) in PaO2. Similarly baseline compared with 30 min post intervention data also resulted in non-significant (p=1.0) increase (0.92%) in PaO2. Control group showed a significant (p=0.031) increase (4.22%) in PaO2 from baseline (215.71 ± 47.47) to 1 min post (224.80 ± 38.84) intervention data.
Figure Comparison of PCO2
Figure Comparison of SaO2
SaO2 showed a non-significant (p=0.859) increase (0.15%) from baseline (99.407 ± .518) to 1 min post intervention (99.553 ± .354) data in experimental group. 1 min post intervention data compared with 30 min post (99.43 ± .58) intervention data it resulted in non-significant (p=1.0) decrease in SaO2. The decrease was 0.12%. Comparison between baseline data and 30 min post intervention data also shows a non-significant (p=1.0) increase (0.03%) in SaO2. In control group the comparison resulted in non-significant (p=0.358) increase (0.17%) in SaO2 from baseline (99.300 ± 1.118) to 1 minute post (99.473 ± 0.770) intervention.
Figure Comparison of PaO2
To our knowledge this is the first study to investigate the effect of ET suctioning and MHI on dynamic lung compliance in sedated, paralyzed mitral valve replacement surgery patients during volume control mode of ventilation on zero post operative day.
Both the group showed increase in dynamic lung compliance from the baseline value. Between group comparison of dynamic lung compliance showed a non significant change in immediate post intervention. This shows that suction along with MHI does not produced any adverse effects on pulmonary function and produced a similar change in dynamic lung compliance as is produced by manual hyperinflation alone. The probable reason for this might be the dominating effect of manual hyperinflation on the suctioning. Since the suction catheter was passed only for once per eight bag compression the adverse effect of suctioning would have been less on pulmonary function and the application of manual hyperinflation with a larger than normal tidal volume breath together with an inspiratory pause adopted in this study may have facilitated collateral ventilation and effective recruitment of alveoli, thereby preventing the adverse effect of suctioning and resulted in increased dynamic lung compliance.11
Within group comparison of experimental group showed an improvement of 4.97% in dynamic lung compliance which was statistically non significant in immediately post intervention duration. The result of the present study was comparable with the study by Morrow et al, in 2007 12 where, when recruitment maneuver was performed after ET suction a non significant increase in dynamic lung compliance was observed immediately after intervention. They have performed MHI five minute after ET suctioning procedure in paediatric patients. They have explained that the decrease in dynamic lung compliance from suctioning resolved spontaneously with unchanged ventilator setting. In the present study MHI was given immediately in conjunction with suctioning. Therefore the effect produced was not due to ventilator settings. The present study is also in support with the study by Blattner et a,l in 2008 4 where, when MHI was applied following suctioning a significant increase in static lung compliance was reported in fifty five myocardial revascularization patients. In another similar study by Siu-Ping et al in 2005 11 when manual hyperinflation and suction was applied on fifteen adult mechanically ventilated pneumonia patients a significant increase (22%) in static lung compliance was observed. In another study by Patman et al in 2000,15 when, manual hyperinflation alone was administered to mechanically ventilated CABG patients they showed a significant increase (15%) in static lung compliance. All the above study showed an increase in lung compliance. In contrast to the above studies some studies have reported a decrease in dynamic lung compliance after the application of intervention. A study by Morrow et al, in 2006, 13 where when, suction alone was administered to mechanically ventilated seventy eight pediatric patients a significant decrease in dynamic lung compliance was reported. In an animal study by Almgren et al, in 2004,8 when suction alone was administered to subjects with pressure controlled and volume controlled ventilation, a significant decrease in dynamic lung compliance was reported. The suction procedure in the present study might have caused a decrease in lung compliance in the ventilated patients. Since the suction catheter was introduced only once per eight bag compression the fall in lung compliance might have been less and effect of manual hyperinflation might have overcome the adverse effect of suctioning, therefore the immediate improvement in dynamic lung compliance which occurred in the present study might have been caused by manual hyperinflation procedure. Furthermore, none of the patients in the present study produced large amount of secretions and, only minimal amounts of secretions were removed during the manual hyperinflation and suction interventions. This minimal change in the airway clearance and the additive effect of manual hyperinflation might have be the additional probable reason for non significant improvement in dynamic lung compliance in 1min post intervention (immediately).In the post 30 min period the dynamic lung compliance demonstrated a fall of 0.93% from 1 minute post intervention to 30 min post intervention in the experimental group. This fall in dynamic lung compliance is also statistically non significant. The probable cause of fall in the lung compliance in the post 30 minute period may be due to a cascade fall in number of reinflated alveoli and the supine position.
Heart rate also showed a non significant change when compared for between group analysis. Both the group showed increase in heart rate from the baseline but the difference between the groups was non significant. Within group comparison of experimental group showed a significant increase (8.02%) in heart rate in immediate post intervention duration. The result of present can be comparable to the study by Lee et al, in 2001 where, they reported a significant increase in heart immediately after first pass and second pass of open suctioning procedure in fourteen adult ventilated patients. 16 The result of the present study is also in support with the study by Stone et al, in 1991 where a statistically significant increase in heart rate was observed from baseline after the three lung hyperinflation-suctioning sequence in CABG patients.17 This indicates that suctioning along with manual hyperinflation increases heart rate. The probable cause for increase in heart rate in the present study may be the activation of sympathetic receptors present in large airways and the discomfort occurred due to the suctioning procedure.18 At the 30 min post intervention heart rate reduced (9.04%) significantly returning to baseline value in experimental group. The probably reason for reduction in the heart in the present study may be due to the relief from suction discomfort. Involvement of parasympathetic activity, vagal stimulation, may be the other valid cause of decrease in heart rate.19,20
Between group analysis of PCO2 resulted in a non significant change in the immediate post intervention period. This indicates that both the group results in similar amount of CO2 washout in immediate post intervention duration. The PCO2 value did not alter significantly after either intervention, indicating that minute ventilation remained adequate.21 Within group comparison of experimental group also resulted in a non significant decrease (2.93%) in PCO2 at 1 min post intervention and 30 min post intervention (3.43%). Since the number of breath for MHI was kept constant (10-12breath/min), the minute might have remained adequate. This is agreement with the attempts made to maintain alveolar ventilation by decreasing the respiratory rate and increasing the tidal volume for hyperinflation. Maintained ventilation of the alveoli during hyperinflation may have prevented a marked washout of CO2 from the blood. The present finding is supported by Paratz et al. where PCO2 did not alter post MHI as alveolar ventilation was maintained.22
PaO2 also showed a non significant difference between the groups at 1 min post intervention. Although the difference in PaO2 is non significant but the improvement was found to be greater in control (MHI) group. This may be due to the fact that MHI might have recruited the atelectatic lung units and might have created a better room for gaseous exchange. (23) Between group comparison also showed a non significant increase in PaO2 in experimental group at 1 min post (1.52%) and at 30 min post (2.47%) intervention. This indicates that suction did not produced any adverse effect on PaO2 value rather, PaO2 value increased 30 minute after intervention in experimental. Studies have suggested that suction when applied in mechanically ventilated patients produces a significant decrease in PaO2 levels in the blood.8, 20,24 In the present study decrease in PaO2 was non significant which mean, the fall in PaO2 was less which indicate that lung function has mot much detiorated after suctioning procedure. The application of MH may utilize intercommunicating channels, or collateral ventilation within the lungs, to facilitate the mobilization of secretions and the recruitment of atelectatic lung units, thereby improving FRC.25 This might be the cause for better gaseous exchange. Since both suctioning and manual hyperinflation were used in the present study, the manual hyperinflation might have masked the adverse effect of suctioning by opening the collateral channel in the lungs and improving the alveolar recruitment and gaseous exchange.
No statistically significant difference in SaO2 was found between the two groups. Within group comparison of SaO2 also showed a non significant increase at 1 min post (0.15%) and at 30 min post intervention (0.12%). Under normal condition the value of PaO2 is ≥ 95 mmHg and value of SaO2 is ≥ 97%. The maximum value of saturation under normal condition is 100%. In the present study all the patient has saturation value above 97% therefore the change observed in patients was very small and it was clinically insignificant. Since the value of PaO2 affects the saturation a non significant change in PaO2 maybe the other probable cause for non significant change in SaO2.
Limitation of the study includes the inability to use a more accurate method of measuring dynamic lung compliance in mechanically ventilated patients. The 30 minute post intervention data could not be collected in control group as suctioning was required to be done immediately after intervention in order to remove collected mucus in central airway. Another limitation includes the lack of fixed dosimetry for suctioning procedure.
Further study is required to be done in various group of population including double valve replacement surgery patients. The sample size used in the study was insufficient to generalize the result therefore a study with a larger sample size is need to be done. Further more, study with different protocol of manual hyperinflation and suctioning are required to be done. This study have found the short term effects of manual hyperinflation and suction on dynamic lung compliance, long term effect of the same is required to be done in future.
In conclusion, our result show that manual hyperinflation when performed with and without suction with a PIP of 40 cmH2O on group of post mitral valve replacement surgery patients no deleterious effect on arterial blood gas value and dynamic lung compliance was found. Therefore, this study suggests that endotracheal suctioning in conjunction with manual hyperinflation does not produce any deleterious changes in dynamic lung compliance and oxygenation in mechanically ventilated mitral valve replacement surgery patients.