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FAQs - Speaking valve option

Artículo

Autor: Simon Franz

Fecha: 16.02.2018

Hamilton Medical offers an optional speaking valve function for the HAMILTON-C1/T1/MR1 ventilators. This function can be activated in the pressure-controlled modes Spont, PCV+ and P-SIMV+.

FAQs - Speaking valve option

Introduction

Prerequisites for use of the speaking valve function are sufficient patency (openness) of the upper airways after unblocking the cuff and a speaking valve approved specifically for use with a ventilator e.g. PMV 007 (Aqua Color) (15 mm I.D. / 22 mm O.D.) from Passy Muir. The PMV is basically a one-way valve that only allows air to flow from the ventilator to the patient. As no air can flow back to the ventilator during expiration, all the tidal volume alarms are based on the inspiratory volume when the speaking valve function is in use. The minute volume and apnea alarms are deactivated.

Below you’ll find answers to some common questions about the speaking valve function. 

What about measured and displayed pressure with a speaking valve?

1. Are pressure and volume measured or just calculated? Is it possible to say how much pressure is in the lungs?

Answer: (Inspiratory) pressure and flow are measured at the proximal flow sensor. The extent to which the values displayed (Ppeak, Pmean, PEEP; TI, TE, I:E; VTI) correspond with the pressure in the lungs is the same with a speaking valve as without. However, the ventilator cannot measure expiratory values, as the PMV is closed in the direction of the ventilator and air can only escape via the upper airways.

What happens to ventilation when the patient talks?

2. When the patient is talking, the vocal cords open and close. How does the ventilator react to this?

The speaking valve function is only available in pressure-controlled modes. The ventilator therefore tries to reach the set pressure. In the case of leakage, it compensates by already increasing the flow during the breath.

Does use of a speaking valve cause decruitment?

3. Is it to be expected that the alveolar space kept open by PEEP will completely collapse when using a speaking valve?

The evidence has shown that this is not the case. “In this cohort of critically ill ventilated patients, SVs did not cause derecruitment of the lungs when used in the ventilator weaning period. Deflating the tracheostomy cuff and restoring the airflow via the upper airway with a one-way valve may facilitate lung recruitment during and after SV use, as indicated by increased EELI” (Sutt AL, Caruana LR, Dunster KR, Cornwell PL, Anstey CM, Fraser JF. Speaking valves in tracheostomised ICU patients weaning off mechanical ventilation--do they facilitate lung recruitment?. Crit Care. 2016;20:91. Published 2016 Apr 1. doi:10.1186/s13054-016-1249-x1​).

What about the pressure support?

4. Does the pressure support remain as set?

The set Psupport is maintained up to the maximum leak compensation.

What indicates there is airtrapping?

5. What is a reliable indicator of airtrapping?

The speaking valve function is only available in pressure-controlled modes and the ventilator therefore tries to reach the set pressure. If the air cannot escape via the upper airways, due to an airway obstruction or accidental inflation of the cuff on the tracheostomy tube, the pressure in the lungs will not increase above the sum of Pcontrol/Psupport and PEEP. In the next breath, the applied inspiratory volume will drop sharply, because the pressure being targeted is already present in the lungs. Therefore, a drop in the inspiratory tidal volume (VTI) is a reliable indicator of situations where airtrapping is starting. As tidal volume alarms are based on inspiratory volumes in the speaking valve mode, this will be recognized. 

Speaking valves in tracheostomised ICU patients weaning off mechanical ventilation--do they facilitate lung recruitment?

Sutt AL, Caruana LR, Dunster KR, Cornwell PL, Anstey CM, Fraser JF. Speaking valves in tracheostomised ICU patients weaning off mechanical ventilation--do they facilitate lung recruitment?. Crit Care. 2016;20:91. Published 2016 Apr 1. doi:10.1186/s13054-016-1249-x



BACKGROUND

Patients who require positive pressure ventilation through a tracheostomy are unable to phonate due to the inflated tracheostomy cuff. Whilst a speaking valve (SV) can be used on a tracheostomy tube, its use in ventilated ICU patients has been inhibited by concerns regarding potential deleterious effects to recovering lungs. The objective of this study was to assess end expiratory lung impedance (EELI) and standard bedside respiratory parameters before, during and after SV use in tracheostomised patients weaning from mechanical ventilation.

METHODS

A prospective observational study was conducted in a cardio-thoracic adult ICU. 20 consecutive tracheostomised patients weaning from mechanical ventilation and using a SV were recruited. Electrical Impedance Tomography (EIT) was used to monitor patients' EELI. Changes in lung impedance and standard bedside respiratory data were analysed pre, during and post SV use.

RESULTS

Use of in-line SVs resulted in significant increase of EELI. This effect grew and was maintained for at least 15 minutes after removal of the SV (p < 0.001). EtCO2 showed a significant drop during SV use (p = 0.01) whilst SpO2 remained unchanged. Respiratory rate (RR (breaths per minute)) decreased whilst the SV was in situ (p <0.001), and heart rate (HR (beats per minute)) was unchanged. All results were similar regardless of the patients' respiratory requirements at time of recruitment.

CONCLUSIONS

In this cohort of critically ill ventilated patients, SVs did not cause derecruitment of the lungs when used in the ventilator weaning period. Deflating the tracheostomy cuff and restoring the airflow via the upper airway with a one-way valve may facilitate lung recruitment during and after SV use, as indicated by increased EELI.

TRIAL REGISTRATION

Anna-Liisa Sutt, Australian New Zealand Clinical Trials Registry (ANZCTR).

ACTRN

ACTRN12615000589583. 4/6/2015.