Method and relevant apparatus for nasal ventilation, particularly for flow-synchronised neonatal assisted ventilation
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Publication Number
US-7814906-B2
Publication Date
2010-10-19
Expiration Date
Abstract
In a method for nasal ventilation and relevant apparatus, particularly for flow-synchronized neonatal assisted ventilation, wherein F(t) is a signal proportional to the ventilation flow, the following steps are performed: (a) inspiration, having a time length Ti, during which air is introduced at an inspiration pressure;(b) expiration, having a time length Te, during which the introduction of air is interrupted;(c) return to step (a); with a flow threshold Ftr, during the expiration step (b) the following steps are provided: (b1) a waiting step having a time length γ before activation of computation of the leakages; and(b2) a step of leakage computation, having a time length δ, so that γ+δ=Te, wherein if a normalized signal F′ (t), obtained by a processing by way of an algorithm of the surveyed signal F(t), exceeds the threshold Ftr, a spontaneous respiration activity is detected and the inspiration step (a) is reactivated.
Core Innovation
The invention is a flow-synchronized neonatal assisted ventilation method in which a signal F(t) proportional to ventilation flow is used during inspiration and expiration. An electrovalve is activated for inspiration for a time length Ti to introduce air at an inspiration pressure, then deactivated for expiration for a time length Te to interrupt the introduction of air, and the process returns to activating inspiration. During said expiration step, a waiting step having a non-zero time length γ is provided before activation of computation of leakages in a ventilation circuit configured for a newborn.
After the waiting step, a step of computation of leakages is performed for a time length δ so that γ+δ=Te. A normalized signal F’(t), obtained by processing the detected signal F(t) according to a normalizing algorithm, is used to determine spontaneous respiration activity when the normalized signal exceeds an expiration flow rate threshold Ftr, and the inspiration step is reactivated accordingly. The algorithm provides sampling of F(t), calculation of a variable average M(t) for each sample for Ti+γ<t<Ti+Te, and calculation of the normalized signal according to the formula F’(t)=F(t)−M(t) for each t value.
The variable average M(t) is calculated using a number of samples N, where M(t)=Σ(i=1 to N) F(i)(t)/N for Ti+γ<t<Ti+Te, with i indexing F(t) samples, and calculation is carried out for each sample acquired during the leakages computation step by inserting each new value acquired. In addition to the timed electrovalve control and leakage computation, the normalized signal and threshold-based determination are used within the flow-synchronized control loop to decide whether spontaneous respiration activity is present and to trigger reactivation of inspiration.
Claims Coverage
Three independent claims are present, covering the flow-synchronized neonatal assisted ventilation method, a corresponding apparatus with pneumotachograph and electrovalve control and leakage normalization for reactivation of inspiration, and an apparatus for nasal ventilation configured to be applied to a newborn, including the same electrovalve timing and normalized-signal threshold triggering based on leakage computation. The inventive features are expressed through the expiration interval split, computation of a variable average M(t) and forming a normalized signal F’(t)=F(t)−M(t), and triggering reactivation of inspiration when F’(t) exceeds an expiration flow rate threshold Ftr during a specified window.
Flow-synchronized neonatal assisted ventilation with waiting and leakage normalization triggering
A method, for flow-synchronized neonatal assisted ventilation, wherein F(t) is a signal proportional to the ventilation flow, comprising activating an electrovalve for inspiration for a time length Ti, deactivating the electrovalve for expiration for a time length Te, and returning to activating inspiration, wherein during said expiration step a waiting step having a non-zero time length γ is provided before activation of computation of leakages, and a step of computation of the leakages having a time length δ is provided so that γ+δ=Te, wherein when a normalized signal F’(t), obtained by processing said detected signal F(t) according to a normalizing algorithm, exceeds an expiration flow rate threshold Ftr, a spontaneous respiration activity is determined and the step for inspiration is reactivated, and wherein said algorithm provides sampling of the F(t) signal, calculation of a variable average M(t) for each sample for Ti+γ<t<Ti+Te, and calculation of F’(t) signal according to formula F’(t)=F(t)−M(t) for each t value, with variable average M(t) calculated according to M(t)=Σ(i=1 to N) F(i)(t)/N for Ti+γ<t<Ti+Te.
Apparatus with pneumotachograph-based normalized flow exceeding threshold for reactivating inspiration
An apparatus for carrying out flow-synchronized neonatal assisted ventilation comprising interface means, a circuit for nasal ventilation configured for a newborn, a pneumotachograph connected to said circuit and configured to detect a signal F(t) proportional to the ventilation flow rate and parameters including inspiration time Ti, expiration time Te, expiration flow threshold Ftr and respiration frequency, the circuit including a nose-cannula, an electrovalve connected with said circuit for nasal respiration for activating-deactivating the introduction of air at an inspiration pressure, and a processing and control unit connected to said electrovalve and configured to control activation during inspiration and deactivation during expiration including a waiting step having a non-zero time length γ, wherein the signal F(t) detected by the pneumotachograph is sampled, the processing and control unit controls electrovalve activation for inspiration during Ti and deactivation for expiration during Te, with waiting a time length γ and computation of the leakages having a time length δ so that γ+δ=Te, wherein when a normalized signal F’(t), obtained by processing said detected signal F(t), exceeds said expiration flow rate threshold Ftr, a spontaneous respiration activity is determined and the activation of the electrovalve for inspiration is reactivated, with F’(t) calculated for each sample for Ti+γ<t<Ti+Te according to F’(t)=F(t)−M(t) using a variable average M(t) calculated according to M(t)=Σ(i=1 to N) F(i)(t)/N for Ti+γ<t<Ti+Te.
Nasal ventilation apparatus configured to determine spontaneous respiration by normalized signal exceeding expiration flow threshold
An apparatus for nasal ventilation, for flow-synchronized neonatal assisted ventilation, comprising a circuit for nasal ventilation configured to be applied to a newborn, an electrovalve connected with said circuit for activating-deactivating introduction of air at an inspiration pressure, a pneumotachograph connected to flow tubes and pressure detection tubes and suitable to detect a signal F(t) proportional to ventilation flow rate and parameters including inspiration time Ti, expiration time Te, expiration flow threshold Ftr and respiration frequency, the circuit comprising a nose-cannula connected with said pneumotachograph, and a processing and control unit connected to said electrovalve and said pneumotachograph and configured to activate the electrovalve for inspiration for Ti, deactivate for expiration for Te, and then return to activating inspiration, wherein said (b) includes a wait having a time length γ and a computation of leakages having a time length δ so that γ+δ=Te, and when a normalized signal F’(t) obtained by processing said detected signal F(t) according to a normalizing algorithm exceeds the expiration flow rate threshold Ftr a spontaneous respiration activity is determined and wherein the activation of the electrovalve for inspiration is reactivated, and wherein said normalized signal F’(t) is calculated for each sample for Ti+γ<t<Ti+Te as F’(t)=F(t)−M(t), where M(t) is a variable average calculated according to M(t)=Σ(i=1 to N) F(i)(t)/N for Ti+γ<t<Ti+Te, with i indexing F(t) samples and N being the number of samples used for calculation of leakages.
Across the independent claims, the core claim coverage centers on splitting expiration into a waiting interval γ and a leakage computation interval δ with γ+δ=Te, computing a variable average M(t) over Ti+γ<t<Ti+Te, forming a normalized signal F’(t)=F(t)−M(t), and determining spontaneous respiration activity by checking whether F’(t) exceeds an expiration flow rate threshold Ftr to decide reactivation of inspiration.
Stated Advantages
Improved leakage normalization by using a normalized signal F’(t)=F(t)−M(t) before comparing to an expiration flow rate threshold Ftr.
Enabling nasal cannula use for flow-synchronized ventilation with reactivation of inspiration based on spontaneous respiration activity determined from the normalized signal.
Reduced false activations/hyperventilation risk by detecting spontaneous respiration activity using the normalized signal exceeding Ftr.
Documented Applications
Flow-synchronized neonatal assisted ventilation using a nasal ventilation circuit including a nose-cannula and pneumotachograph, with electrovalve control and leakage computation during expiration to determine spontaneous respiration activity.
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