Measuring lung function and lung disease progression at a lobar/segmental level
View Patent ↗A method for determining lung function in a patient is disclosed, in which a multi-lumen catheter with an expandable occluding element at its end is used to isolate a targeted lung compartment, and respiratory characteristics at the targeted lung compartment are measured over multiple respiratory cycles. The relation between various characteristics of the respiratory cycle is used to determine compliance of lung tissue within the targeted lung compartment.
1. A method for determining elasticity of a portion of a lung in a patient, the method comprising:
introducing a catheter into an airway leading to a targeted lung compartment, the catheter comprising a distal end, a proximal end, and a lumen therebetween, wherein the distal end comprises an expandable occluding element which is configured to sealingly engage the airway, wherein the proximal end comprises an inflation port to expand the occluding element, wherein the lumen is in-line with at least one sensor for measuring pressure in the targeted lung compartment, and wherein a solenoid valve is in-line or within the lumen;
expanding an occluding member disposed on or near a distal end of the catheter to form a seal with an inner wall of the airway to thus isolate the targeted lung compartment;
measuring airflow to and from the targeted lung compartment over multiple inspiratory and expiratory cycles;
determining a tidal flow volume during respiration, wherein the tidal flow volume is determined as an average volume of air breathed over multiple inspiratory and expiratory cycles;
allowing the patient to exhale such that air exhaled from the targeted lung compartment is allowed to pass through a lumen of the catheter;
closing the solenoid valve thereby preventing airflow to or from the targeted lung compartment to create a closed target lung compartment;
measuring pressure in the closed target lung compartment during exhalation using a pressure sensor coupled with the lumen of the catheter;
determining elasticity of the targeted lung compartment based on the tidal flow volume and the measured pressure of the closed target lung compartment; and
determining a disease state based on the elasticity of the target lung compartment.
2. The method of claim 1 , further comprising determining a relationship between the tidal flow volume, the pressure in the targeted lung compartment, and changes in the pressure over multiple inspiratory and expiratory cycles.
3. The method of claim 2 , further comprising determining the relationship between pressure and volume to determine elasticity of the airway.
4. The method of claim 1 , further comprising determining a peak pressure in the closed target lung compartment.
5. The method of claim 4 , further comprising opening the valve after the peak pressure is reached.
6. The method of claim 5 , further comprising determining a rate of recovery of the pressure in the targeted lung compartment from the peak pressure.
7. The method of claim 6 , wherein the disease state of the targeted lung compartment is determined based on the rate of recovery of the pressure in the targeted lung.
8. The method of claim 1 , further comprising generating a pressure-tidal volume curve, wherein the elasticity is determined by calculating a slope of the curve.
9. The method of claim 1 , wherein the measuring pressure in the closed target lung compartment is accomplished at various points in a normal respiratory cycle by opening and closing the valve being closed at various points in the normal respiratory cycle.