Apparatus for respiratory support and non-invasive detection of alveolar derecruitment for patients suffering from respiratory failure
Apparatus for respiratory support and non-invasive detection of alveolar recruitment/derecruitment provides air supply to a patient at a base pressure and an additional pressure which can be varied at a frequency of from 5 to 10 Hz and transducers applied to the conduits supplying air to the patient to send electric signals to a computer to obtain a variable positive end-expiratory pressure and a to obtain an end expiratory resistance at varying values of positive end expiratory pressure and defining the state of pulmonary recruitment as the value of the positive end-expiratory pressure which corresponds to a point of maximum expiratory resistance.
1. An apparatus ( 1 ) for respiratory support and non-invasive detection of alveolar recruitment/derecruitment for patients ( 2 ) suffering from respiratory failure, said apparatus ( 1 ) comprising means ( 3 ) for providing a pressure component (P resp ); means ( 15 ) for adding an additional pressure component (P stim ) at a frequency comprised between 5 and 10 Hz with a pressure comprised between 2 and 4 cm H 2 O; conduits ( 5 , 6 , 7 , 20 , 21 ) for the passage of said pressure component (P resp ) and said additional pressure component (P stim ) from and to the airways of a patient ( 2 ); transducers, applied to said conduits, of pressure ( 9 , 10 ) to electric signals; transducers, applied to said conduits, of flow ( 8 ) to electric signals and computing means ( 12 ) for providing a variable positive end-expiratory pressure (PEEP) to said patient ( 2 ); processing said electric signals so as to obtain a value of the end-expiratory reactance (Xee), at the varying of the value of said positive end-expiratory pressure (PEEP), and defining a state of pulmonary recruitment, as the value of the positive end-expiratory pressure (PEEP) which corresponds to a point of maximum end-expiratory reactance (Xee).
2. An apparatus according to claim 1 , wherein said means ( 3 ) for providing a pressure component (P resp ) comprise a mechanical ventilator ( 3 ) allowing imposition of inspiration/expiration functions, and a settable positive end-expiratory pressure (PEEP).
3. An apparatus according to claim 1 , wherein said means ( 15 ) for adding an additional pressure component (P stim ) comprise a high frequency oscillating ventilator allowing imposition of a periodic pressure having a frequency and an amplitude suitable to allow obtaining inspiratory reactance.
4. An apparatus according to claim 1 wherein said computing means ( 12 ) automatically controls the settings of said means ( 3 ) for providing a pressure component (P resp ) allowing carrying out the respiratory functions, said computing means ( 12 ) being provided with algorithms adapted to determine the maximum value of the end-expiratory reactance (Xee).
5. An apparatus according claim 1 wherein said means ( 15 ) for adding an additional pressure component (P stim ) comprise a speaker ( 15 ) fitted to at least one of said conduits ( 5 ).
6. An apparatus according to claim 1 wherein said means ( 15 ) for adding an additional pressure component (P stim ) comprise a modulating valve fitted to at least one of said conduits ( 5 ).
7. An apparatus according to claim 1 wherein said means ( 3 ) for providing a pressure component (P resp ) provide a pressure waveform (ΔP) greater than 30 cmH 2 O or a tidal volume (Vt) greater of 12 ml/kg of body weight; said computing means ( 12 ) provide a progressive decreasing of said pressure waveform (ΔP) or said tidal volume (Vt) in some steps; said computing means ( 12 ) calculates an end-inspiratory reactance (Xei) at each step until the end-inspiratory reactance Xei is higher of a given threshold or until the difference between the end-expiratory reactance (Xee) and the end-inspiratory reactance (Xei) is smaller than a given threshold.