physiologic impact of closed-system endotracheal suctioning in

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Physiologic Impact of Closed-System Endotracheal Suctioning in Spontaneously Breathing Patients Receiving Mechanical Ventilation Christopher W Seymour MD, Brian J Cross MD, Colin R Cooke MD MSc, Robert L Gallop PhD, and Barry D Fuchs MD BACKGROUND: Endotracheal suctioning is required but can have adverse effects, and could affect cardiorespiratory variables that are used to predict whether the patient is ready for extu- bation. METHODS: In a prospective cohort study in a university hospital’s medical intensive care unit, we measured the impact of closed-system suctioning on cardiopulmonary variables in spon- taneously breathing patients weaning from mechanical ventilation. All spontaneously breathing, mechanically ventilated patients were screened for enrollment at the initiation of weaning from mechanical ventilation. Before, during, and after standardized closed-system endotracheal suction- ing we measured minute volume, heart rate, arterial oxygen saturation, mean arterial pressure, respiratory frequency, oxygen saturation, and tidal volume. RESULTS: Twenty-nine patients were enrolled after a median of 5 (interquartile range [IQR] 3–9) ventilator days. Twenty-five patients (86%) were spontaneously breathing on pressure-support ventilation when suctioned. The median post-suctioning recovery time was > 5 min for minute volume, tidal volume, respiratory rate, and ratio of respiratory rate to tidal volume. The post-suctioning median values of the maximum deviations in the ventilatory variables were clinically important: minute volume –2.4 (IQR 1.6 – 3.7) L/min, respiratory rate 8 (IQR 2–14) breaths/min, tidal volume 175 (108 –220) mL. Heart rate, mean arterial pressure, and oxygen saturation increased after suctioning (P < .05), but the increases were not clinically important. CONCLUSIONS: Post-suctioning changes in the measured variables persisted longer in these spontaneously breathing patients weaning from mechanical ventilation than in patients who are sedated and paralyzed. The effects of suctioning on cardiopul- monary function should be considered in practice and during the design of future studies on weaning and extubation prediction variables. Key words: endotracheal suctioning, cardiopulmonary, spontaneous breathing, weaning, mechanical ventilation, extubation, respiration, sputum, sedation. [Respir Care 2009;54(3):367–374. © 2009 Daedalus Enterprises] Introduction In mechanically ventilated patients, endotracheal suc- tioning is frequently required to clear secretions. Suction- ing is generally considered safe, but can cause arterial hypoxemia, altered mean arterial pressure, and cardiac ar- rhythmia; can increase the risk of nosocomial pneumonia; can increase intracranial pressure; and can even cause car- diac arrest. 1-6 Closed suctioning systems are used more frequently than open systems, in part because adverse ef- fects on cardiopulmonary function are thought to be less common, although evidence is lacking. 7 In adult mechanically ventilated patients who are se- dated and paralyzed, closed-system suctioning has mini- At the time of this research, Christopher W Seymour MD was affiliated with Hospital of the University of Pennsylvania, Philadelphia, Pennsyl- vania. Brian J Cross MD is affiliated with the Division of Cardiology, Tufts Medical Center, Boston, Massachusetts. Colin R Cooke MD MSc is affiliated with the Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, Washington. Robert L Gallop PhD is affiliated with the Applied Statistics Program, Department of Mathemat- ics, West Chester University, West Chester, Pennsylvania. Barry D Fuchs MD is affiliated with the Division of Pulmonary, Allergy, and Critical Care Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania. The authors declare no conflicts of interest. Correspondence: E-mail: [email protected]. RESPIRATORY CARE MARCH 2009 VOL 54 NO 3 367

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Page 1: Physiologic Impact of Closed-System Endotracheal Suctioning in

Physiologic Impact of Closed-System Endotracheal Suctioning inSpontaneously Breathing Patients Receiving Mechanical Ventilation

Christopher W Seymour MD, Brian J Cross MD, Colin R Cooke MD MSc,Robert L Gallop PhD, and Barry D Fuchs MD

BACKGROUND: Endotracheal suctioning is required but can have adverse effects, and couldaffect cardiorespiratory variables that are used to predict whether the patient is ready for extu-bation. METHODS: In a prospective cohort study in a university hospital’s medical intensive careunit, we measured the impact of closed-system suctioning on cardiopulmonary variables in spon-taneously breathing patients weaning from mechanical ventilation. All spontaneously breathing,mechanically ventilated patients were screened for enrollment at the initiation of weaning frommechanical ventilation. Before, during, and after standardized closed-system endotracheal suction-ing we measured minute volume, heart rate, arterial oxygen saturation, mean arterial pressure,respiratory frequency, oxygen saturation, and tidal volume. RESULTS: Twenty-nine patients wereenrolled after a median of 5 (interquartile range [IQR] 3–9) ventilator days. Twenty-five patients(86%) were spontaneously breathing on pressure-support ventilation when suctioned. The medianpost-suctioning recovery time was > 5 min for minute volume, tidal volume, respiratory rate, andratio of respiratory rate to tidal volume. The post-suctioning median values of the maximumdeviations in the ventilatory variables were clinically important: minute volume –2.4 (IQR 1.6–3.7) L/min, respiratory rate 8 (IQR 2–14) breaths/min, tidal volume �175 (108–220) mL. Heartrate, mean arterial pressure, and oxygen saturation increased after suctioning (P < .05), but theincreases were not clinically important. CONCLUSIONS: Post-suctioning changes in the measuredvariables persisted longer in these spontaneously breathing patients weaning from mechanicalventilation than in patients who are sedated and paralyzed. The effects of suctioning on cardiopul-monary function should be considered in practice and during the design of future studies onweaning and extubation prediction variables. Key words: endotracheal suctioning, cardiopulmonary,spontaneous breathing, weaning, mechanical ventilation, extubation, respiration, sputum, sedation.[Respir Care 2009;54(3):367–374. © 2009 Daedalus Enterprises]

Introduction

In mechanically ventilated patients, endotracheal suc-tioning is frequently required to clear secretions. Suction-

ing is generally considered safe, but can cause arterialhypoxemia, altered mean arterial pressure, and cardiac ar-rhythmia; can increase the risk of nosocomial pneumonia;can increase intracranial pressure; and can even cause car-diac arrest.1-6 Closed suctioning systems are used morefrequently than open systems, in part because adverse ef-fects on cardiopulmonary function are thought to be lesscommon, although evidence is lacking.7

In adult mechanically ventilated patients who are se-dated and paralyzed, closed-system suctioning has mini-

At the time of this research, Christopher W Seymour MD was affiliatedwith Hospital of the University of Pennsylvania, Philadelphia, Pennsyl-vania. Brian J Cross MD is affiliated with the Division of Cardiology,Tufts Medical Center, Boston, Massachusetts. Colin R Cooke MD MScis affiliated with the Division of Pulmonary and Critical Care Medicine,University of Washington, Seattle, Washington. Robert L Gallop PhD isaffiliated with the Applied Statistics Program, Department of Mathemat-ics, West Chester University, West Chester, Pennsylvania. Barry D FuchsMD is affiliated with the Division of Pulmonary, Allergy, and CriticalCare Medicine, Hospital of the University of Pennsylvania, Philadelphia,Pennsylvania.

The authors declare no conflicts of interest.

Correspondence: E-mail: [email protected].

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mal effects on heart rate, respiratory rate, tidal volume(VT), airway pressure, and arterial oxygen saturation mea-sured via pulse oximetry (SpO2

).8-10 However, little is knownabout the impact of closed-system suctioning on the car-diopulmonary functioning of spontaneously breathing pa-tients.11 In the absence of sedation and paralysis, whenreflexive or reactive responses are not suppressed and ven-tilation is not fixed, we hypothesized that suctioning mightcause substantial and sustained changes in respiratory pat-tern, volumes, and other variables that are important inassessing a patient’s readiness for discontinuation of ven-tilatory support.12-14

We prospectively measured the magnitude and durationof changes in cardiopulmonary variables and spontaneousrespiratory pattern and volumes during after closed-systemendotracheal suctioning in spontaneously breathing, me-chanically ventilated patients.

Methods

This prospective study was performed in the medicalintensive care unit (ICU) of the Hospital of the Universityof Pennsylvania, between October 2004 and March 2005,and the hospital’s institutional review board approved theresearch protocol and waived the requirement for writteninformed consent.

Patient Population

All mechanically ventilated patients were screened foreligibility on consecutive days, by staff during morningrounds. Patients were eligible if they were � 18 years old,endotracheally intubated, on volume controlled continuousmandatory ventilation, volume controlled intermittent man-datory ventilation, or pressure-support ventilation (PSV),required a fraction of inspired oxygen (FIO2

) � 0.55, pos-itive end-expiratory pressure (PEEP) � 5 cm H2O, andmaking spontaneous respiratory efforts. Patients were ex-cluded if there were any clinical events or practitionerinterventions within 15 min prior to study enrollment (eg,a change in ventilator settings, hemodynamic instabilitythat required vasopressors, administration of neuromuscu-lar blockade, or if previously enrolled in this study).

Suctioning

At the time of enrollment, the closed-system endotra-cheal suctioning technique recommended by the AmericanAssociation for Respiratory Care (AARC) was reviewedwith the nurses and respiratory therapists.15 The AARCguidelines recommend: pre-oxygenation with 100% oxy-gen for at least 30 s prior to suctioning; universal precau-tions; duration of suctioning 10–15 s with catheter with-drawal and with the minimum negative pressure needed

(� 200 mm Hg); and hyperoxygenation with 100% oxy-gen for 1 min following the suctioning. Data-collectionoccurred at the first necessary suctioning after study en-rollment, and was performed by a nurse or respiratorytherapist. The study staff documented their adherence tothe AARC suctioning guidelines. Data collection occurredduring one suctioning episode per patient, and no system-atic suctioning schedule was employed after enrollment. Inall patients, suctioning was performed with a 14 French(4.6 mm inner diameter, 30.5 cm long) suction catheter(Ballard Medical Products, Draper, Utah). No hyperinfla-tion or recruitment maneuvers were employed during orafter suctioning.9 We used a closed suctioning system, sothere no was interruption of the ventilator circuit duringsuctioning.

Data Collection

We measured minute volume (VE), VT, respiratory rate,mean arterial pressure, SpO2

, frequency (f), and heart rate.Values were collected every minute for 15 min prior to,during, and for 30 min after suctioning. For every mea-sured variable, the baseline value was defined as the me-dian value during the 15-min pre-suctioning period (Fig. 1).During the post-suctioning period, recovery was definedas having 2 consecutive values fall within the 10–90%range surrounding the median baseline value. Time to re-covery was defined as the duration from time zero aftersuctioning to the first minute of the 10–90% range win-dow. If there was a biphasic response (ie, both positive andnegative deflections from the median baseline), we reportthe maximum deviation (positive or negative) from base-line prior to recovery.

Respiratory rate, VT, and VE were recorded with a data-collection device (VueLink, Philips Medical Systems,Bothell, Washington) that collects data from multiple de-vices. VE and VT were measured as expired volumes. TheVueLink interfaced with the ventilator (either a 7200 or an840, Puritan Bennett, Pleasanton, California) and with thecardiac monitor (M1097A, Philips Medical Systems, Both-ell, Washington), which allowed one trending of data points.One-minute averages were automatically calculated fromdata sampled every 12 s. f/VT was calculated post hoc atall time points, irrespective of ventilator settings. SpO2

wasrecorded by the cardiac monitor. Mean arterial pressurewas measured via a radial artery catheter (20G, ArrowInternational, Reading, Pennsylvania).

Because interventions and other clinical events can alterrespiratory pattern and volumes, during the pre-suctioningbaseline observation period all ventilator changes, medi-cal/nursing interventions, and other clinical events and en-vironmental stimuli (eg, additional non-protocol endotra-cheal suctioning; physical patient contact by a physician,nurse, or respiratory therapist; oral suctioning; or airway

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manipulation) were recorded by the study staff, and pa-tients who had such pre-suctioning events were excludedfrom the study. If such an event occurred after the suc-tioning episode, the data from after the event were cen-sored. Minor, unimportant events (eg, blood draws fromexisting arterial or central lines; presence of family, nurse,or physician in the room without patient interaction oragitation; or administration of intravenous medications)were recorded but did not result in patient exclusion ordata censoring.

Other data recorded included the time of suctioning, thereason for ICU admission and intubation, ventilator days,endotracheal tube (ETT) size, ventilation mode, presenceof intrinsic PEEP, most recent Richmond Agitation-Seda-tion Scale score, most recent arterial blood gas values, andnumber of suctioning episodes in the preceding 8 hours.Effect of suctioning on serial measurements of RichmondAgitation-Sedation Scale was not studied. Practitionerswere directly observed during the suctioning episode torecord whether the patient was appropriately pre-oxygen-ated, the number of suctioning passes, and the negativepressure employed.

Statistical Analysis

Baseline values, time to recovery, and maximum posi-tive or negative deviation of each variable are expressed asmedian and interquartile range (IQR), as assessed by theShapiro-Wilk test. The post-suctioning median values werecompared to the baseline values via the 2-sided, pairedStudent’s t test or the Wilcoxon rank-sum test, as appro-priate. We used univariate regression analysis to determinethe association between other patient and suctioning pro-cedure variables and the time to variable recovery. Differ-

ences were considered statistically significant whenP � .05.

We considered a variable change clinically important ifthe value reached a published threshold that could impactclinical decisions and/or a � 15% change from baseline.Because volume-controlled ventilation influences post-suctioning VT and VE, we conducted a sensitivity analysis,in which we excluded patients on volume-controlled ven-tilation, to determine its influence on the results. All anal-yses were performed using statistical software (NCSS 2000,NCSS, Kaysville, Utah).

Results

Of the 115 patients screened during the 5-month enroll-ment period, 50 met the inclusion criteria (Fig. 2). The

Fig. 1. Upper panel: Minute volume (VE) before, during, and aftersuctioning. The recovery period was defined as recovery of eachmeasured variable (by 2 consecutive measurements) to within the10–90% range around the median baseline value. Lower panel:Sequence of pre-suctioning oxygenation, suctioning procedure,and post-suctioning oxygenation.

Fig. 2. Screening, exclusion, and inclusion of study subjects. ICU �intensive care unit. FIO2

� fraction of inspired oxygen.

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primary reason for exclusion was extubation prior to data-collection (36%). One patient was excluded after enroll-ment because he was suctioned during the baseline period.There were 29 evaluable patients. Some post-suctioningdata from some patients were censored because of clinicalevents prior to complete recovery of the measured vari-ables. The censored data were: VE, 1 patient; respiratoryrate, 2 patients; mean arterial pressure, 1 patient; heartrate, 1 patient.

Table 1 describes the study subjects. The median dura-tion of ventilation prior to enrollment was 5 days. At thetime of data-collection, 25 (86%) of the 29 subjects wereon PSV, with minimal PEEP and FIO2

, and large ETTs(median and interquartile-range inner diameter 8.0 (IQR7.6–8.0) mm). Their median pre-suctioning Richmond Ag-itation-Sedation Scale score was –1 (drowsy but could stayawake in response to verbal stimuli).16 Sixty-five percentof the suctionings were performed by nurses. Fifty-twopercent of the suctioning episodes had 2 suctioning passes.The median suction pressure was 200 mm Hg. The medianpre-suctioning PaCO2

was 38 (IQR 28–41) mm Hg.Table 2 shows the recovery times and magnitudes of

deviation from baseline, before and after exclusion of the4 patients who were on volume-controlled ventilation. Fig-

ure 3 shows the recovery-time data standardized by thebaseline values. VT decreased significantly for 2 min, andfull recovery required a median 5 min. Respiratory rateincreased by a median 8 breaths/min, and full recoveryrequired 5 min. VE increased and decreased; the maximumnegative deviation was 2.4 L/min, and full recovery re-quired 7 min. f/VT significantly increased for 5 min. Fig-ure 4 shows the change in non-normalized f/VT values.

Though the change in SpO2and heart rate was less dra-

matic, both remained significantly different from baselinefor up to 5 min. In the sensitivity analysis, after excludingthe 4 patients on volume-controlled ventilation, there wereno significant differences in recovery time or duration ofpost-suctioning differences in the PSV cohort.

None of the recovery times of any of the variables wereunivariately associated with the number of suction-cathe-ter passes, the number of suctioning episodes in the 8 hoursprior to the data-collection period, the negative pressureemployed, the occurrence of directly observed minor stim-uli, or the Richmond Agitation-Sedation Scale score(P � .05).

Discussion

In spontaneously breathing mechanically ventilated pa-tients, standardized closed-system suctioning resulted instatistically significant and clinically important changes inthe measured cardiac variables and respiratory pattern andvolumes, and the changes persisted longer than has beenreported in heavily sedated and paralyzed patients. To our

Table 1. Subject Characteristics

Male (n, %) 16 (55)Median (IQR) ventilation days prior to suctioning 5 (3–9)Median (IQR) suctioning passes in the 8 h before

enrollment3 (1–3)

Median (IQR) Richmond Agitation-SedationScale score

–1 (–3 to 0)

Diagnostic category (n, %)*Pulmonary 6 (21)Cardiac 2 (7)Gastrointestinal 5 (17)Infectious disease 7 (24)Other 9 (31)

Number of suctioning passes 2 (1–2)Nurse performed suctioning (n, %) 19 (65)Pre-oxygenation (n, %) 29 (100)Median (IQR) suctioning pressure (mm Hg) 200 (150–200)Median (IQR) endotracheal tube diameter (mm) 8 (7.6–8.0)Median (IQR) pressure-support (cm H2O) 7 (7–11)Median (IQR) FIO2

0.40 (0.40–0.40)Median (IQR) PEEP (mm Hg) 5 (5–5)

* Pulmonary category included pneumonia, chronic obstructive pulmonary disease, asthma,acute respiratory distress syndrome, pulmonary embolus, and hemoptysis. Cardiac categoryincluded congestive heart failure, cardiogenic shock, acute myocardial infarction, andarrhythmia. Gastrointestinal category included hepatic failure, cirrhosis, gastrointestinal bleed.Infectious disease category included sepsis, human immunodeficiency virus, acquired immunedeficiency syndrome. Other included endocrine or metabolic disorder, seizure, and alteredmental status.IQR � interquartile rangeFIO2 � fraction of inspired oxygenPEEP � positive end-expiratory pressure

Table 2. Post-Suctioning Recovery Time and Maximum DeviationsFrom Baseline

Recovery Time(median, IQR min)

WholeCohort

(n � 29)

PSVCohort

(n � 25)

Maximum DeviationFrom Baselinemedian (IQR)*

VE 7 (3–12) 7 (3–14) –2.4 (�1.6 to �3.7) L/minf 5 (2–8) 6 (2–8) 8 (2–14) breaths/minVT 5 (3–8) 5 (3–8) –175 (�108 to �220) mLf/VT 6 (3–15) 6 (3–17) 58 (30–110)Oxygen

saturation1 (1–8) 1 (1–9) 1 (0–2)%

Mean arterialpressure

4 (1–12) 5 (2–13) 4 (–2 to 12) mm Hg

Heart rate 4 (1–8) 4 (1–10) 6 (1–9.5) beats/min

* If both positive and negative deflections occurred, the reported value is in the direction ofthe largest deviation.IQR � interquartile rangePSV � pressure-support ventilationVE � minute volumef � frequencyVT � tidal volume

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knowledge this is the first report to describe changes inVT, VE, and f/VT after closed-system suctioning in spon-taneously breathing patients. The post-suctioning changesin mean arterial pressure, SpO2

, and heart rate were statis-tically significant but not clinically important.

Several studies have examined the physiologic effectsof suctioning, in both animals and humans.8-11,17-19 Al-though suctioning has had long-lasting adverse effects inanimal models,20,21 descriptions of the effects of suction-ing on cardiopulmonary variables in human subjects havebeen limited to the period immediately following suction-ing, and only in patients who were heavily sedated orparalyzed. The immediate effects observed were due to themagnitude of the loss in airway volume, the use of pre-oxygenation, and changes in airway pressure during thesuctioning episode. In the present study we evaluated thesustained cardiopulmonary responses to suctioning.

During closed-system suctioning the immediate loss oflung volume relates both to technical factors (eg, ETTdiameter, negative pressure applied, suction catheter di-ameter, and ventilator settings) and to patient-related fac-tors (eg, presence of reactive airways disease, and degreeof lung injury).9 In sedated and paralyzed patients withacute lung injury, with comparable suction catheters andnegative pressure, the suctioning-induced decrease in end-expiratory lung volume ranged from 100 mL to 500 mL.8-10

That inter-subject variability may be explained by differ-ences in respiratory mechanics; patients with less compli-ant lungs are more predisposed to alveolar de-recruitment.22

Although our patients required minimal FIO2and PEEP,

we found similar variability, but the changes lasted longer.That difference may be due to the level of sedation and theventilator settings. In heavily sedated subjects the post-suctioning recovery of lung volume occurs within 1 min.9,10

This was also found in sedated animals, although thoseprolonged post-suctioning VT decreases were in animalsventilated with pressure-controlled ventilation, not volume-controlled ventilation.21 This suggests that the longer VT

recovery time in the present study may relate to the pre-dominant use of PSV. Deep sedation also depresses bothlaryngeal and tracheal reflexes,23,24 which suggests thatour less sedated patients may have had larger and longerchanges due to stimulation by the suction catheter. In theonly comparable trial of awake patients, Lee et al alsofound that respiratory rate increased for 5 min after closed-system suctioning, but the magnitude of the change(2 breaths/min) was less than we observed.11 RichmondAgitation-Sedation Scale scores were not reported in thatstudy, and differences in sedation probably account for thedifference in respiratory rate.

Suctioning also altered VE and f/VT for up to 7 min inour cohort. Specifically, VE tracked with the decrease inVT before increasing to above the baseline value, drivenby post-suctioning tachypnea. We did not perform serialPaCO2

measurements, but the absence of baseline hyper-carbia implies that out patients were not underventilatedprior to suctioning. The observed changes in f/VT and VE

may impact clinical decisions, because these changes ex-ceeded published threshold values for guiding decisionsabout discontinuing mechanical ventilation (f/VT � 105,

Fig. 3. Median values standardized by baseline values. The error bars represent the upper and lower quartiles. * � P � .05 compared tomedian baseline values for each patient. VE � minute volume. SpO2

� arterial oxygen saturation measured via pulse oximetry. f � frequency(respiratory rate). VT � tidal volume.

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VE recovery time � 5 min) in many patients.12-14 It is alsopossible that the use of PSV during f/VT measurement(albeit not the method used by Yang et al) underestimatedthe effect of suctioning on f/VT.12,25

Although SpO2decrease is common during open-system

suctioning, it is rarely seen with closed-system suction-ing.1,8,18 In fact, the present study and others found thatoxygenation improved.18 In compliance with the AARCguideline,15 all the patients were pre-oxygenated with 100%oxygen (an FIO2

much above their baseline). In our cohort,which did not have substantial lung injury, pre-oxygen-ation maintained normoxemia during and after suctioning.

There were small but statistically significant post-suction-ing changes in heart rate and mean arterial pressure. Oth-ers have reported significant post-suctioning changes inheart rate, which immediately resolved after suctioning,but those studies had a very brief post-suctioning obser-vation period (� 2 min) and the patients were sedated andparalyzed.8,10,19

Limitations

Changes in the ventilator settings can confound the re-lationship between the measured cardiopulmonary vari-ables and the suctioning episode. Our sample size mayalso have limited our power to detect associations betweenrecovery-time and other variables, such as Richmond Ag-itation-Sedation Scale score, number of suctioning passes,and suction pressure. Our methods of measuring the vari-ables were chosen to model behavior in practice. We tookthe expired VT value from the ventilator display, which isderived from direct breath-by-breath measurements, andsuch ventilator-measured VT values are less accurate thancan be obtained with a research pneumotachometer,12 butthe values were automatically recorded, which has beensuccessfully employed in prior studies of weaning indi-ces.26-28 We did not record the ventilator expiratory-flowcycle criterion, and differences in that setting may haveaffected VT.29 Also, we calculated f/VT with a non-stan-dard technique, while the patient was supported with PSV,12

which may have underestimated the true f/VT.25 Continu-ous measurement rather than minute-to-minute changesmight have provided more accurate trends. Measurementof arterial blood gases from arterial blood samples was notfeasible, but might have provided more accurate measure-ments of gas exchange; however, the clinical importanceof post-suctioning PaO2

changes in patients with preservedSpO2

is unknown.To standardize our protocol and encourage uniform suc-

tioning technique by all study staff, we used the AARCsuctioning guideline. Because we instructed the staff in theAARC guidelines, our results might underestimate the ef-fects of different suctioning procedures in routine ICUpractice. To exclude effects from stimulations other thanthe suctioning episode, we monitored the patient and thepatient’s surroundings via direct observation of patient ac-tivity and stimulation before, during, and after the suction-ing episode. Although there were both major and minorepisodes of patient stimulation, and corresponding datawere excluded or truncated, it is possible that we missedsome stimulation events that altered our findings.

The post-suctioning changes and delayed recovery ofcardiorespiratory variables in spontaneously breathing pa-tients may have implications for both routine clinical prac-tice and research studies in the ICU. Because empiricalsuctioning may occur prior to initiating spontaneous breath-

Fig. 4. Baseline versus highest post-suctioning values for the ratioof respiratory rate (f) to tidal volume (VT). The smaller square datapoints and their error bars (to the left and right of the 2 columns ofdata points) represent the medians and interquartile ranges. Atbaseline, all 29 patients had an f/VT � 105. After suctioning, 16patients (55%) had an f/VT � 105 (dotted lines).

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ing trials, suctioning-induced rapid shallow breathing mayconfound measurements that are used to predict the like-lihood of weaning/extubation success.12-14 In addition, suc-tioning could cause unexpected tachypnea and reduced VT

if the patient is suctioned at the time of ETT removal. Priorstudies of weaning/extubation prediction indices have notcontrolled for the potential effects of suctioning, whichmight have impacted the consistency and interpretation oftheir results.12-14,30-32

Conclusions

We observed significant and sustained alterations in car-diac variables and respiratory pattern and volumes afterclosed-system suctioning in spontaneously breathing, me-chanically ventilated patients. The changes lasted longerthan in sedated and paralyzed patients. The clinical im-portance of these findings remains unknown, but the tim-ing of suctioning may need to be considered when assess-ing patient readiness to tolerate weaning or extubation, andmay need standardization in future studies of weaning andextubation prediction variables.

ACKNOWLEDGMENTS

We thank David J Pierson MD FAARC, Division of Pulmonary andCritical Care Medicine, Harborview Medical Center, University of Wash-ington, Seattle, Washington, and Michael A Grippi MD, Pulmonary,Allergy, and Critical Care Division, University of Pennsylvania HealthSystem, Philadelphia, Pennsylvania, for their detailed comments and re-view of this manuscript.

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