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Ventilator versus manual hyperinflation in clearing sputum in ventilated intensive care unit patients.

Hyperinflation in the artificially ventilated intensive care unit (ICU) patient aims to increase lung oxygenation, reverse lung collapse and clear lung secretions, and has been routinely used by physiotherapists since the early 1970s (1). Historically, hyperventilation has been delivered manually (MHI) using a resuscitation reservoir bag. There is extensive literature supporting its efficacy and the consistency of its implementation by physiotherapists (2). Hyperventilation utilising a ventilator (VHI) is, by comparison, a relatively new technique. VHI was first described in the literature in 2002 (3) and then again in 2006 (4) when it was compared to MHI. More recently, its efficacy was compared to positioning alone (5). Despite the limited published evidence, a recent survey has established that almost 40% of Australian tertiary ICUs are utilising VHI in some form or other (6). Implementation is currently based on the individual's clinical judgement and experience with 60% following specific protocols, although only 20% of these are formally documented (6).

The purpose of this study was to determine whether or not VHI was as effective as MHI in clearing sputum secretions from patients receiving mechanical ventilation in ICUs at an acute tertiary ICU. The research team developed a protocol for VHI based on their extensive experience in advanced ventilation and the protocols currently in use across Australia which, although anecdotally sound, are based on limited published evidence.

MATERIALS AND METHODS

Inclusions/exclusions

All patients admitted to the ICU at Sir Charles Gairdner Hospital (SCGH) who were receiving mechanical ventilation and who demonstrated atelectasis or consolidation on chest X-ray were considered for inclusion. Patients with any of the well-documented and accepted contraindications to hyperinflation were excluded (Table 1). Those ventilated using airway pressure release ventilation were also excluded as this ventilation mode precludes circuit disconnection for MHI.

The SCGH Ethics Committee approved this trial (approval number 2010-039) and a waiver of patient consent was granted on the premise that VHI has been demonstrated to be part of routine clinical management of ventilated patients in other comparable Australian ICU facilities and has widespread acceptance (6).

Process

The study was a non-inferiority cross-over trial comparing VHI and MHI. As per usual clinical practice, the attending intensive care physician and physiotherapist decided which patients required physiotherapy intervention on the morning ward round, and these patients were considered for inclusion in the trial.

Utilising the Evita XL[R] ventilator (Drager Medical, Lubeck, Germany) all patients received two physiotherapy treatments (one utilising MHI, the other VHI) by the same physiotherapist on the day of measurement, one in the morning and one in the afternoon, with a minimum of three hours between treatments (Figure 1). Using cards in unmarked envelopes, patients were randomly allocated to receive either MHI or VHI treatment first. Before treatment, ventilation mode, fraction of inspired oxygen (Fi[O.sub.2]), positive end-expiratory pressure (PEEP), tidal volume ([V.sub.t]), airway pressure (Paw), dynamic lung compliance ([C.sub.L]), heart rate, systolic blood pressure and mean arterial blood pressure, respiratory rate and arterial blood gases were recorded. In addition, intracranial pressure and cerebral perfusion pressure was also recorded when relevant.

Patient positioning during treatment

As per the current management, where possible during this trial, patients were positioned in side-lying with 20 to 30[degrees] whole bed upward tilt for physiotherapy treatment. If lung pathology was unilateral on the chest X-ray, the affected side was uppermost. Positioning was the same for both morning and afternoon treatments.

MHI treatment

MHI treatment was as follows: one physiotherapist delivered the MHI breaths while the other physiotherapist delivered manual vibrations on the chest wall and suction. Using a standard Laerdal resuscitation bag, the MHI circuit delivered 15 l/minute of oxygen as per current clinical practice, and a manometer was included in the circuit so that the peak airway pressure delivered was 40 cm[H.sub.2]O. Breath-hold of no less than two seconds was maintained at the end of the inspiratory phase. Expiration was passive and the same PEEP was applied during expiration as that which was applied via the patient's ventilator. There were four sets of eight breaths per set. Airway suctioning was carried out during treatment if indicated or immediately after treatment. An open suction system was used and sputum was collected in a sputum trap connected to the suction catheter. On completion of the suction passes, 10 ml of sterile saline was flushed through the suction tubing to the trap to clear any secretions in the catheter. The wet weight of the sputum was calculated using a two decimal digital scale and subtracting the weight of the trap and the saline from the total weight of the trap and its contents.

[FIGURE 1 OMITTED]

VHI treatment

We used synchronised intermittent mandatory ventilation to deliver VHI. Alarms were adjusted so that Paw alarm was 45 cm[H.sub.2]O and [V.sub.t] alarm was 250% of initial [V.sub.t]. Fi[O.sub.2] was increased to 1.0 for the duration of treatment. PEEP remained unchanged. Inspiratory time was adjusted to three to five seconds, respiratory rate to six to eight breaths and [V.sub.t] to deliver hyperinflation breaths that were 15 ml/kg as calculated using lean body weight. VHI was initially implemented by incrementally increasing [V.sub.t] by 150 ml at a time until target volume or Paw limit of 40 cm[H.sub.2]O was reached. In subsequent sets increments were usually larger depending on initial clinical response. There were four sets of eight VHI breaths delivered at each treatment. Suctioning was carried out as per MHI treatment and sputum was collected and measured in the same manner.

Outcome measures

Hyperinflation improves sputum clearance without compromising cardiovascular stability or gas exchange (7). The efficacy of the hyperinflation mode was therefore measured by the amount of sputum cleared. This approach is consistent with other physiotherapy trials investigating sputum clearance (7,8). A difference in sputum levels in the morning compared with the afternoon was accounted for in the sample size calculation and by randomising the order of treatment. Secondary outcome measures collected both immediately and 30 minutes after treatment included cardiovascular observations, [C.sub.L] and Paw. Arterial blood gases were also sampled and recorded before and 30 minutes after treatment, and the [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio was calculated.

Data analysis

Mixed model regression analysis was used to assess the data (in both univariate and multivariate form), including patient as the random effect to assess the relationship between the above mentioned explanatory variables and the responses. Variables that were significant at a 5% significance level were retained in the final model. Summary means and standard errors are also provided. All statistical analyses were performed with R software version 2.11.1 (R Foundation for Statistical Computing, Vienna, Germany).

RESULTS

Treatment was undertaken in a 23-bed Level 3 ICU at a metropolitan tertiary hospital. A total of 48 patients were recruited into the study over two separate month-long study periods in 2010 and 2011. Two patients were withdrawn from the study when they received paralysing agents after the first physiotherapy treatment in order to undergo medical investigation or procedure. Characteristics of the cohort are presented in Table 2. The mean age of the patients was 57 years and they were mostly male (72%). Patient admission category, diagnosis and source were diverse, but all patients had documented changes on the chest X-ray and were productive of sputum. Patients were positioned right (46%) or left (43%) side-lying or upright (11%) and were receiving synchronised intermittent mandatory ventilation with auto-flow (57%), pressure support ventilation (39%) or pressure control ventilation (4%).

There was no significant difference in sputum wet weight between MHI and VHI treatments (P=0.989). The mean (95% confidence interval) was 3.215 g (2.365 g, 4.065 g) after MHI and 3.210 g (2.543 g, 3.878 g) after VHI. Multivariate analysis found that increased pre-treatment tidal volume (P=0.009) and decreased pre-treatment [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio (P=0.008) predicted higher sputum wet weight.

A summary of the means and standard errors of secondary variables is shown in Table 3. There were no significant differences between techniques across all variables on univariate analysis except for Paw, which showed an increase with MHI compared to VHI (P=0.002, Figure 2). There were significant differences between time points on univariate analysis across [V.sub.t] (P=0.019, Figure 3), Sp[O.sub.2] (P <0.0001) and mean arterial blood pressure (P <0.0001). After adjusting for potential confounders there was a significant interaction between technique and time for [P.sub.a][O.sub.2] (P=0.014) and [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio (P=0.024, Figure 4).

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

DISCUSSION

The important findings of this study are: first, that there was no difference in sputum wet weights following physiotherapy treatment utilising MHI or VHI; second, that MHI resulted in higher Paw than VHI; third, that pre-treatment [V.sub.t] and [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio predicted wet weight sputum; and fourth, that there was an interaction between technique and time in the [P.sub.a][O.sub.2] analysis such that over time, [P.sub.a][O.sub.2] decreased when MHI was being used and increased when VHI was being used. The same interaction and trend were seen in the [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio analysis.

This study has shown that during physiotherapy, when VHI is applied in such a way as to mimic MHI, both techniques were equally effective in sputum clearance. Further, the only significant difference in secondary measures was a decrease in Paw with VHI compared with MHI. This decrease was not clinically significant (1 cm[H.sub.2]O) but may indicate a trend whereby patients with higher Paw pre-treatment may have less likelihood of increasing Paw following treatment with VHI versus MHI. Importantly, there was no significant difference between techniques in all other measures of gas exchange and respiratory and haemodynamic status. Mean arterial blood pressure and Sp[O.sub.2] increased in a response to either treatment, but returned to the same level at 30 minutes post-treatment. This indicates that VHI is equally as safe as MHI when applied using the study protocol.

Lung collapse or consolidation on the chest X-ray was selected as an entry criteria as it is a common clinical indicator for physiotherapy (7). Other studies looking at MHI have utilised static rather than dynamic [C.sub.L] (1,4,5,7,9). This measurement is taken during the cessation of airflow, when elastic recoil is independent of airway resistance. This study measured dynamic [C.sub.L] because patients were ventilated on pressure support ventilation, pressure control ventilation or synchronised intermittent mandatory ventilation autoflow and that is what the ventilator calculates in these modes. The increase in [V.sub.t] and decrease in Paw seen over time in this study reflects improved static [C.sub.L], consistent with the findings of other MHI studies (1,4,5,7,9).

A novel finding of this study was that higher sputum wet weight was predicted by higher pretreatment [V.sub.t]. The higher [V.sub.t] may be a surrogate for obstructive lung disease, however the highest pretreatment Paw within the cohort was 32 mmHg (mean 20 mmHg). Another explanation for this could be that a higher [V.sub.t] results in increased inspiratory flow rate that enhances sputum clearance. The use of high volumes to mobilise secretions during physiotherapy is therefore also supported.

Another interesting finding in this study is the decrease in [P.sub.a][O.sub.2] and [P.sub.a][O.sub.2]:Fi[O.sub.2] ratio over time following MHI compared to VHI. This finding supports the eligibility criteria of the study, whereby patients with high PEEP and high Fi[O.sub.2] requirements were excluded because their level of support precluded the circuit disconnection required for MHI. We postulate that circuit disconnection results in a loss of PEEP that may be detrimental to gas exchange. This 'de-recruitment' effect may be persistent (still present at 30 minutes after MHI ended in our study). The opposite trend demonstrated with VHI suggests that patients in whom it is hard to maintain adequate gas exchange with or without high PEEP and Fi[O.sub.2] may both tolerate and benefit from physiotherapy treatment using VHI. Future studies are needed to look at physiotherapy techniques combined with VHI for the purpose of recruitment, in conjunction with studies of stepwise progression of hyperventilation for rescue (10).

Other advantages of VHI over MHI are that it may prevent infection transmission due to circuit disconnection to both patient and attending staff and it requires only one person to administer, which has both direct and indirect cost-saving implications in terms of scheduling and the co-ordination of staff.

A limitation of the study was the consistency of MHI compared to real clinical practice. During the study, MHI was delivered using the same person (a physiotherapist) with consistent technique including measurement of Paw (40 cm[H.sub.2]O, with manometer in the circuit) with every breath delivered, a standard number of repetitions and a two-second breath-hold at end of inspiration. This may or may reflect normal clinical practice, which in this unit utilises the bed-space nurse to deliver MHI. Published studies have questioned the quality of nursing-delivered MHI for the purpose of physiotherapy (11,12). In this way, the efficacy of the clinical practice of MHI may be overstated in this study.

CONCLUSION

This study has demonstrated VHI to be as safe and as effective in clearing sputum during physiotherapy as MHI if it is applied with the same parameters and precautions. There are potential advantages of VHI over MHI, the biggest of which is the fact that unlike MHI, there is no ventilator circuit disconnection required using VHI. This research describes a VHI protocol that will serve as a platform for continued discussion, research and development of its application in ventilated patients.

ACKNOWLEDGEMENTS

Our study was funded by the SCGH Research Advisory Committee and supported by the SCGH Research Foundation. We thank Professor P. Vernon van Heerden for his review of the manuscript and the nursing staff of the SCGH ICU for their cooperation during data collection.

REFERENCES

(1.) Patman S, Jenkins S, Stiller K. Manual hyperinflation--effects on respiratory parameters. Physiother Res Int 2000; 5:157-171.

(2.) Hodgson C, Carroll S, Denehy L. A survey of manual hyperinflation in Australian hospitals. Aust J Physiother 1999; 45:185-193.

(3.) Berney S, Denehy L. A comparison of the effects of manual and ventilator hyperinflation on static lung compliance and sputum production in intubated and ventilated intensive care patients. Physiother Res Int 2002; 7:100-108.

(4.) Savian C, Paratz J, Davies A. Comparison of the effectiveness of manual and ventilator hyperinflation at different levels of positive end-expiratory pressure in artificially ventilated and intubated intensive care patients. Heart Lung 2006; 35:334-341.

(5.) Lemes DA, Zin WA, Guimaraes FS. Hyperinflation using pressure support ventilation improves secretion clearance and respiratory mechanics in ventilated patients with pulmonary infection: a randomised crossover trial. Aust J Physiother 2009; 55:249-254.

(6.) Dennis DM, Jacob WJ, Samuel FD. A survey of the use of ventilator hyperinflation in Australian tertairy intensive care units. Crit Care Resusc 2010; 12:262-268.

(7.) Hodgson C, Denehy L, Ntoumenopoulos G, Santamaria J, Carroll S. An investigation of the early effects of manual lung hyperinflation in critically ill patients. Anaesth Intensive Care 2000; 28:255-261.

(8.) Hodgson C, Ntoumenopoulos G, Dawson H, Paratz J. The Mapleson C circuit clears more secretions than the Laerdal circuit during manual hyperinflation in mechanically-ventilated patients: a randomised cross-over trial. Aust J Physiother 2007; 53:33-38.

(9.) Choi JS, Jones AY. Effects of manual hyperinflation and suctioning in respiratory mechanics in mechanically ventilated patients with ventilator-associated pneumonia. Aust J Physiother 2005; 51:25-30.

(10.) Hodgson CL, Tuxen DV, Davies AR, Bailey MJ, Higgins AM, Holland AE et al. A randomised controlled trial of an open lung strategy with staircase recruitment, titrated PEEP and targeted low airway pressures in patients with acute respiratory distress syndrome. Crit Care 2011; 15:R133.

(11.) Paulus F, Binnekade JM, Middelhoek P, Schuitz MJ, Vroom MB. Manual hyperinflation of intubated and mechanically ventilated patients in Dutch intensive care units--a survey into current practice and knowledge. Intensive Crit Care Nurs 2009; 25:199-207.

(12.) Paulus F, Binnekade JM, Middelhoek P, Vroom MB, Schultz MJ. Performance of manual hyperinflation: a skills lab study among trained intensive care unit nurses. Med Sci Monit 2009; 15:CR418-242.

D. DENNIS *, W. JACOB *, C. BUDGEON ([dagger])

Intensive Care Unit, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia

* BAppSc (Physiotherapy), Senior Physiotherapist.

([dagger]) BSc (Hons) Applied Statistics, Statistician, University of Western Australia Centre for Applied Statistics, Department of Research and Development.

Address for correspondence: Mrs D. Dennis, Intensive Care Unit, Sir Charles Gairdner Hospital, Hospital Avenue, Nedlands, WA 6009. Email: Diane.Dennis@health.wa.gov.au

Accepted for publication on October 24, 2011.
Table 1
Contraindications to VHI or MHI

Conditions Acute pulmonary oedemas

 Severe bronchospasm
 Haemoptysis

 Documented cystic lung
 changes (bullae or blebs)

 Subcutaneous emphysema

 Undrained pneumothoraces
 or intercostal catheter with air
 leak

 Obstructing airway tumour or
 lung tumour

 Bronchopleural fistula

 Patients requiring nitric oxide
 or prostaglandins infusions

 Coagulopathic conditions

Physiological parameters

Respiratory PEEP (>10 cm[H.sub.2]O)

 Fraction of inspired oxygen
 (Fi[O.sub.2]) >0.7

 Paw >33 cm[H.sub.2]O
 (30-40 cm[H.sub.2]O)

 Increased respiratory rate in
 agitated patient

Cardiovascular instability MAP <60 mmHg

 Inotrope requirement
 equivalent to >15 ml/h total of
 adrenaline and noradrenalin
 (dilution 3 mg/50 ml)

 Patients requiring ECMO

Neurological instability ICP >20 mmHg

VHI=ventilated hyperventilation, MHI=manual hyperventilation,
PEEP=positive end expiratory pressure, MAP=mean arterial
pressure, ECMO=extracorporeal membrane oxygenation,
ICP=intracranial pressure.

Table 2
Baseline demographic data (n=46)

Age, y 57 (18.93) *
Gender, M, n (%) 33 (72)
ICU LOS, d 4 (1-13) **
APACHE II score 18.5 (5-42) **
BMI 28.9 (5.3)
Admission category, n (%)
 Medical 24 (52)
 Elective surgical 2 (4)
 Trauma (including non-elective surgical) 19 (41)
 Other 1 (2)
Admission diagnosis, n (%)
 Cardiac
 Pulmonary 9 (19)
 Neurological 15 (33)
 Septic 5 (11)
 Other 12 (26)
Admission source, n (%)
 Emergency department 7 (15)
 Operating theatres 18 (39)
 Other SCGH wards 5 (11)

M=male, ICU=intensive care unit, LOS=length of stay,
BMI=body mass index, SCGH= Sir Charles Gairdner Hospital.
* Mean (SD). ** Median (range).

Table 3
Summary of means (SD) for all variables

 MHI

Variable Before Immediately 30 minutes
 after after

Gas exchange
 [P.sub.a]C[O.sub.2], mmHg 37.4 (6.35) 37.3 (6.43)
 [S.sub.a][O.sub.2], % 97.5 (1.44) 97.5 (1.3)
 [P.sub.a][O.sub.2]/ 273 (85.41) 265 (74.1)
 Fi[O.sub.2]
Respiratory observations
 Tidal volume, ml 587 (133.76) 610 (204.23) 601 (172.65)
 PEEP, cm[H.sub.2]O 7 (2.09) 7 (2.11) 7 (2.11)
 Sp[O.sub.2], % 97.3 (1.97) 98.2 (1.64) 97.3 (1.8)
 Respiratory rate 17 (6.43) 18 (8.07) 17 (6.43)
 Airway pressure, 21.0 (4.3) 20.3 (4.6) 20.9 (4.66)
 cm[H.sub.2]O
 Dynamic compliance, 61.3 (32.13) 63.5 (32.4) 61.9 (36.47)
 ml/cm[H.sub.2]O
Cardiovascular observations
 MAP, mmHg 86 (18.35) 92 (19.66) 87 (18.2)
 Heart rate, bpm 80 (18.84) 81 (19.18) 82 (18.28)
Neurological observations
 Intracranial pressure, mmHg 11 (5.34) 12 (5.07) 10 (5.5)
 Cerebral perfusion 86 (13.13) 91 (12.89) 89 (23.37)
 pressure, mmHg

 VHI

Variable Before Immediately 30 minutes
 after after

Gas exchange
 [P.sub.a]C[O.sub.2], mmHg 37.9 (6.21) 37.1 (5.71)
 [S.sub.a][O.sub.2], % 97.4 (1.55) 97.6 (1.61)
 [P.sub.a][O.sub.2]/ 268 (85) 278 (85.55)
 Fi[O.sub.2]
Respiratory observations
 Tidal volume, ml 551 (125.75) 614 (215.6) 592 (177.94)
 PEEP, cm[H.sub.2]O 7 (2.09) 7 (2.29) 7 (2.06)
 Sp[O.sub.2], % 97.2 (2.34) 99.0 (1.07) 97.5 (2)
 Respiratory rate 18 (7.26) 17 (6.69) 17 (6.17)
 Airway pressure, 20.4 (4.78) 19.9 (4.56) 19.8 (4.44)
 cm[H.sub.2]O
 Dynamic compliance, 59.3 (28.35) 64.0 (30.01) 62.2 (28.08)
 ml/cm[H.sub.2]O
Cardiovascular observations
 MAP, mmHg 87 (15.9) 91 (17.08) 86 (16.46)
 Heart rate, bpm 80 (17.52) 80 (17) 81 (16.92)
Neurological observations
 Intracranial pressure, mmHg 11 (6.19) 9 (6.62) 12 (5.02)
 Cerebral perfusion 83 (14.14) 92 (17.58) 80 (11.85)
 pressure, mmHg

 P value

Variable Technique Time Interaction
 (technique
 x time)
Gas exchange
 [P.sub.a]C[O.sub.2], mmHg 0.663 0.176 0.105
 [S.sub.a][O.sub.2], % 0.884 0.457 0.473
 [P.sub.a][O.sub.2]/ 0.394 0.839 0.044
 Fi[O.sub.2]
Respiratory observations
 Tidal volume, ml 0.219 0.019 0.403
 PEEP, cm[H.sub.2]O 0.235 0.683 0.551
 Sp[O.sub.2], % 0.063 <0.0001 0.049
 Respiratory rate 0.929 0.723 0.201
 Airway pressure, 0.002 0.135 0.459
 cm[H.sub.2]O
 Dynamic compliance, 0.823 0.286 0.748
 ml/cm[H.sub.2]O
Cardiovascular observations
 MAP, mmHg 0.593 <0.0001 0.725
 Heart rate, bpm 0.579 0.413 0.764
Neurological observations
 Intracranial pressure, mmHg 0.576 0.717 0.188
 Cerebral perfusion 0.648 0.104 0.276
 pressure, mmHg

MHI=manual hyperventilation, VHI=ventilated hyperventilation,
PEEP=positive end expiratory pressure, MAP=mean arterial pressure.
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Author:Dennis, D.; Jacob, W.; Budgeon, C.
Publication:Anaesthesia and Intensive Care
Article Type:Report
Geographic Code:8AUST
Date:Jan 1, 2012
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