Use of a New Isokinetic Device for Inspiratory Muscle Training

Introduction:

It is well established that physical fitness improves muscle performance either in sedentary people or in athletes. In this regard, specific exercises for respiratory muscles can result in better functional performance in hospitalized individuals, especially in critically ill patients in prolonged weaning.

Objectives:

To compare the following variables between intervention and control patients: success in weaning, free time off ventilator on ICU after weaning, and gain of muscle strength with the use of the inspiratory muscle training (IMT).

Patients and methods:

Prospective randomized controlled clinical trial. Only individuals on prolonged weaning will be enrolled. They will undergo IMT or will be managed in a conventional manner. The primary endpoint will be successful weaning. In addition, other variables such as free time off ventilator on ICU after weaning and muscle strength will be measured. In addition, mortality in the ICU, inside the hospital and after discharge will be followed for one year after study entrance.

Expected results:

According to the working hypothesis, it is expected that the performance of patients undergoing IMT will be superior to the conventional treatment. Also, their time to mortality is expected to be longer.

The control group only performed inspiratory muscle training (IMT) with the use of the T-piece. From the first day of prolonged weaning, patients would remain in spontaneous breathing progressing their stay time each day, respecting the criteria already mentioned for interruption and return to mechanical ventilation in support pressure mode.

The intervention group, in addition to the protocol described above, would undergo inspiratory muscle training with the POWER breathe K-5 (UK) device. POWER breathe K-5 will be employed once a day, with an initial loading of 40% of maximal inspiratory strength in a schedule of 30 repetitions. This number of repetitions could be reached in one to 6 sessions depending on the respiratory muscle force of the patient. Most of the times more than one session were required. Typically, subjects performed two to six sessions of 5 to 15 breaths per day, with two minutes rest in ventilation pressure support mode. When the patient was unable to comply with the schedule, the training session was interrupted at a total of 3 minutes. The load was planned to be adjusted weekly with a 5 to 10% increase until 60% of the maximal inspiratory strength was reached with a total time of 10 minutes or 100 breaths. After training with POWER breathe K-5 (UK), the patient would return to mechanical ventilation in support pressure mode for 30-60 minutes, and then follow the conventional T-piece protocol. The IMT was conducted normally between 08h and 10h, Monday through Friday.

All study subjects would be under continuous surveillance through the multi-parameter DX 2010 monitor (Dixtal, São Paulo, SP, Brazil), which records the electrocardiogram, heart rate, peripheral oxygen saturation and systemic arterial pressure. At any sign of instability, the IMT was interrupted and the patient returned to the ventilatory support and/or supplemental oxygen therapy for recovery.

The trial was stopped if at least one of the following intolerance criteria was present: SaO2\<90% or PaO2 \<60 mm Hg with FIO2 \>0.4; PaCO2 \> 50 mm Hg or increased by \> 8 mm Hg; arterial pH \< 7.33 or decreased by 0.07 or more; breathing frequency \> 35 breaths/min or increased by 50% for 5 min or longer; heart rate \> 140 beats/min or a sustained increase or decrease of \> 20%; mean blood pressure \> 130 or \< 70 mm Hg; or presence of agitation, diaphoresis, disorientation, or depressed mental status.

Eligibility Criteria:
Inclusion Criteria:

* Individuals over the age of 18 on mechanical ventilation
* Able to initiate ventilator weaning.

Exclusion Criteria:

* Positive serology for HIV
* Other immunesupressive conditions
* Life expectancy less than 12 months
* Spinal cord injury above T8
* Mechanical ventilation started at another institution
* Body mass index \>35 kg/m2.