Acute effect of the use of cycle ergometer during physical therapy treatment in mechanically ventilated critically ill patients

278 Mailing address: Alexandre Simões Dias – Rua Ramiro Barcelos, 2.350, Santa Cecília – Porto Alegre (RS), Brasil – CEP: 90035-903 – E-mail: simoesdias@terra.com.br – Funding source: Nothing to declare – Conflict of interest: Nothing to declare – Presentation: Oct. 2015 – Accepted for publication: Oct. 2016 – Approved by the Ethics Committee: 415.748; International registration number: RBR-4tdvt9. DOI: 10.1590/1809-2950/15549123032016

ICUs in Brazil and worldwide have been searching for alternative therapies to help assisting patients [19][20][21] .In this context, early mobilization has been more used as a therapeutic choice in treatment centers.Recent studies demonstrated that early mobilization is feasible and safe for mechanically ventilated patients.They also demonstrated that this procedure decreases ICU stay, hospitalization period and of MV 7,22,23 .Moreover, when early mobilization is not practiced in the ICU, there are increased rates of hospital readmission and death within the first year after hospital discharge 24,25 .
The use of a cycle ergometer was a good alternative on early intervention for critically ill patients, increasing functional capacity, self-perception, and quadriceps strength 12 .Therefore, the objective of this study was to compare the intense use of a cycle ergometer in mechanically ventilated critically ill ICU patients regarding hemodynamic effects, respiratory mechanics, and lactate levels before and after it was used.

METHODOLOGY
This is a randomized clinical trial, conducted at the Porto Alegre Teaching Hospital, from May to December 2013.The study population was composed of ICU patients from Porto Alegre Teaching Hospital.We included patients aged 18 years and older, male and female, admitted to the ICU at HCPA with at least 24 hours and not more than 48 hours of invasive mechanical ventilation (IMV).Patients came from emergency department or inpatient unit, with no more than 1 week of hospitalization.This study was approved by the Research Ethics Committee of the Porto Alegre Teaching Hospital, report No. 415.748, and the informed consent form was signed by the person responsible for the patient.
Exclusion criteria include patients with neuromuscular diseases who presented motor deficit, such as cerebrovascular accident, multiple sclerosis, amyotrophic lateral sclerosis, myasthenia gravis, and Guillain-Barré syndrome.Similarly, we excluded patients extubated in less than 48 hours after being included in the study and who had hemodynamic instability (noradrenaline >0.5 mc/kg/min for a mean arterial pressure >60 mmHg), complications during the protocol (pneumothorax, deep vein thrombosis, and pulmonary embolism), Shilley catheter in the femoral vein, need for reintubation, prolonged weaning (3 failed spontaneous breathing trials), body mass index (BMI) >35 kg/m 2 , and development of eschar in the calcaneal during the protocol.
The final sample of 25 individuals had its selected individuals randomly placed in groups of 10 using the website Randomization (www.randomization.com)on intervention group (IG) or conventional group (CG).
Patients from both groups were seen for 30 to 45 minutes and the difference between the groups was the use of the cycle ergometer.The cycle ergometer used was an in-bed simple Cajumoro ® Flexmotor (São Paulo, Brazil).
Physical therapy care protocol for conventional group: 30-minute physiotherapy session.The protocol included upper and lower extremity diagonals from the Proprioceptive Neuromuscular Facilitation method (two series of 10 repetitions for each bilateral diagonal), and bronchial hygiene exercises such as vibrocompression, manual hyperinflation, and aspiration of secretions when necessary.The intervention group underwent the abovementioned physiotherapy and passive cycle ergometer exercises.Patients were submitted to the exercise with 20 cycles per minute for 20 minutes before conventional physiotherapy.The patient was in supine position to use the cycle ergometer and the bed was elevated to 30 degrees.
For hemodynamic evaluation, we used heart rate (HR) and mean arterial pressure (MAP) measures, which were obtained from the ICU multi-parametric monitor (Infinity Kappa, Dräger, Germany).Respiratory variables analyzed were tidal volume (Vt), respiratory frequency (RF), positive end expiratory pressure (PEEP), and fraction of inspired oxygen (FiO 2 ), obtained from the mechanical ventilators monitor (Servo, Maquet, Sweden and Evita-4, Dräger, Germany).We also measured gas exchange using the arterial blood gas test and C-reactive protein and lactate levels.
Statistical analysis was carried out using SPSS 18.0.We used mean and standard deviation to describe continuous data and absolute and percentage values to categorical data.We used Student's t-test or Mann-Whitney test to compare quantitative variables between groups.We adopted a 5% significance level.

RESULTS
During the pre-established period for data collection, 25 patients met the study inclusion criteria.After randomization, 14 patients were included in the intervention group (IG) and 11 in the conventional group (CG).Average age of the patients was 55.21±23.1 (IG) and 61.8±22.6 (CG) years and the percentage of females was 57.1% and 45.4%, respectively.Mean duration of mechanical ventilation was 11.8±8.8(IG) and 12.6±5.1 (CG) days and the average ICU length of stay was 20.1±15.1 and 20.1±9.3 days, respectively.APACHE II, which predicts the risk of death during the first 24 hours of ICU admission, mean scores were 23.6±9.6 (IG) and 27.8±4.9(CG).(Table I).Pre-and post-intervention values regarding respiratory mechanics revealed a statistically significant change for peak pressure, maximum inspiratory pressure (pre=25.1±5.9 and post=21.0±2.7 cmH 2 O; p=0.03 -Table II) in the conventional group.The ABG test revealed a significant difference for bicarbonate (pre: 23.5±4.3 and post: 20.6±3.0;p=0.002 -Table III) in the intervention group.Lactate and C-reactive protein levels revealed no significant difference in both groups when we compared pre-and post-intervention values (Table IV).From total sample, seven patients were diagnosed with sepsis, 3 from the intervention group and 4 from the control group.Demographic data of these patients revealed statistically significant differences for age (IG=61.1±10.5 and CG=81.6±5.1 years -p=0.0001),weight (IG=73.5±15.6 and CG=54.0±17.8kg -p=0.005), and body mass index (BMI) (IG=29.9±7.9 and CG=20.4±5.6 -p=0.002).Duration of mechanical ventilation, period of hospitalization, and ICU length of stay revealed no significant differences, as shown in Table V.
Non-septic patients from both groups showed no significant differences for abovementioned demographic and temporal variables.

DISCUSSION
The main finding of this study is that the use of a protocol for early mobilization and the cycle ergometer did not cause cardiorespiratory changes, neither changed physiological variables in mechanically ventilated patients, however, we did not observe a reduction in ICU length of stay and period of hospitalization when we compared it to the early mobilization protocol without the use of cycle ergometer.The study found a significant decrease in peak pressure pre-and post-intervention in the conventional group.Moreover, we found significant differences between the two groups in age, weight, and BMI of patients who were diagnosed with sepsis.
Critical mechanically ventilated patients usually stayed in the hospital bed, or because of their insecurity, or unpreparedness of healthcare team, both an obstacle to mobility.These patients also suffered with sleep deprivation, social isolation, poor nutritional status, sedation, and other consequences from ICU stay, which affected the functionality of these patients 26 .
Early mobilization, however, has been proving itself beneficial to reduce the duration of mechanical ventilation and to improve the functionality of patients.More recently, early physical activity has been used in critically ill patients with neurological and cardiorespiratory stability 27 .Early mobilization includes progressive therapeutic exercises, e.g., bed exercises, sitting at the edge of bed, orthostatism, transfer from sit to stand, and ambulation 28 .
Dantas et al. 29 administered an early mobilization protocol to 14 mechanically ventilated patients and evaluated its effect on peripheral and respiratory muscles.The authors gathered evidence that inspiratory and peripheral muscles strength increased significantly.
They also analyzed the duration of mechanical ventilation, period of hospitalization, and ICU length of stay.They did not detect significant differences between the two groups, corroborating findings from our study.
Pires-Neto et al. 30 assessed hemodynamic, respiratory, and metabolic effects of early use of the cycle ergometer in critically ill patients.The authors used the equipment in the first 72 hours of mechanical ventilation in 19 patients and did not observe significant changes in the variables analyzed.In this study, however, we observed a significant decrease of bicarbonate in the intervention group arterial blood gas test, comparing pre-and postintervention values.We must point out that there is no clinical explanation for this fact, for there was no significant change in any other arterial blood gas test variable.
APACHE II score predicts the risk of death during the first 24 hours of ICU admission.This score is a severity-of-disease classification system 31 and may influence critical patients prognosis.Soares et al. 32 assessed in a longitudinal study the effects of taking 51 ICU patients from bed.The authors, analyzing APACHE II scores, noted that patients who were removed from hospital bed were in better conditions than patients who were not removed.When the authors analyzed the actual mortality and predicted mortality rates, i.e., what APACHE II score predicted and what was clinically found, they also found statistically significant differences when comparing patients removed from the hospital bed and patients not removed: rates were higher for patients not removed.
In this study there was no significant difference in APACHE II scores between the two groups, therefore, it was not possible to determine how the variables were related.
In an observational study, Gael et al. 11 analyzed the physiological effects of early mobilization on 20 critical patients, who were included because they stayed in ICU for 7 days and received mechanical ventilation for at least 2 days.Exercises included sitting out of bed, standing with assistance of a tilt table, and ambulation.Authors observed significantly decreased heart rate (HR) and respiratory frequency (RF) after sitting out of bed exercises.Aforementioned variables, however, significantly increased during standing with assistance of a tilt table and ambulation, in the latter there was a significant decrease in peripheral oxygen saturation.
Chris et al. 12 used a mobility protocol consisting of respiratory and motor physiotherapy exercises, in which the cycle ergometer was also used (20 minutes every day) in the intervention group.The authors assessed quadriceps muscle strength and functionality state of patients after ICU and hospital discharge.We administered the six-minute walk test after hospital discharge.We did not observe significant differences at ICU discharge comparing the two groups for abovementioned variables.Intervention group, however, presented significantly higher six-minute walk test results at hospital discharge for quadriceps strength and functionality state.

CONCLUSION
The limitations of our study is its small sample size and impossibility of analyzing factors affecting muscle function.On the other hand, the strength of our study is the comparison of two acute physical therapy care protocols using cycle ergometer in mechanically ventilated critically ill patients, which we hope will call healthcare professionals attention to its use, since there was no significant variation regarding variables analyzed in this study.It is also worth mentioning that unmodified outcomes (duration of MV and period of hospitalization) may be related to this study design, which focused on the acute effect of adding the use of cycle ergometer to a physical therapy protocol on intensive care unit patients.
Therefore, results obtained in this study demonstrated that neither does the use of cycle ergometer in a protocol for early mobilization alter hemodynamic and respiratory mechanics, nor does it result in acute physiological responses.

Table 2 .
Comparison of respiratory and hemodynamic variables

Table 3 .
Arterial blood gas test pH: Power of hydrogen; PaO 2 : Partial pressure of oxygen; PaCO 2 : Partial pressure of carbon dioxide; HCO 3 : Bicarbonate

Table 4 .
Comparison of physiological variables CRP: C-reactive protein

Table 5 .
Comparison of demographic variables of septic patients from both groups