336539 – Respiratory Flows and Inhalation Therapy

Course Objectives and Targets

This course discusses (i) the nature of respiratory flows in the lung and (ii) introduces students to the fundamentals of inhalation therapy. We will begin by building an engineering understanding of respiratory flow phenomena, oxygen transport, and the importance of convection and diffusion along the airway tree. In addition, we will discuss the role of surface tension in the lung and analyze dynamics of thin liquid layer flows. Our overall approach relies on analytical tools drawing from fluid mechanics and transport phenomena. Next, we will discuss therapeutic aerosol inhalation in treating airway diseases and infections. Our discussion will based on the governing mechanisms for particle transport and deposition, and looking at interactions between deposited particles and airways. Finally, we will discuss current designs of medical devices for inhalation delivery.

Throughout the course, a strong emphasis will be put on developing physical insight using dimensional analysis, parameter estimations, and order of magnitude assessments. This approach is intended for students to build a tangible and intuitive understanding of the physical mechanisms governing airflow, gas diffusion, as well as particle transport and deposition in the lungs.

Specific objectives

  • To teach students to analyze the lungs as an engineered system with design constraints.
  • To teach students the application of fluid mechanics in understanding pulmonary flows.
  • To teach students the relevance of lumped models to understand respiratory functions.
  • To teach students to manipulate dimensional analysis to grasp respiratory phenomena.
  • To teach students the physical fundamentals of aerosol transport.
  • To teach students the physical mechanisms governing particle deposition in the lungs.
  • To teach students engineering strategies to treat airway diseases via particle inhalation.

Weekly Lecture Topics

PART I: RESPIRATORY FLOWS

Week 1.

Introduction: an engineer’s view of the lungs. We will discuss the lung as a complex gas exchanger: (i) Evolutionary designs of a biological gas exchanger,  (ii) Biological structure and function (iii) Mechanical considerations: lung compliance.

Week 2. Lumped models of respiration. We will describe respiratory flows using:  (i) Linear/non-linear single compartment models(ii) Basics of flow limitation(iii) Two-compartment models.

Week 3. Fundamentals of respiratory fluid mechanics. We will introduce the governing flow parameters in the respiratory tract by  starting from the Navier-Stokes equations and deriving the relevant dimensionless parameters for the lung.

Week 4. Optimal branching structure: design and disease. We will follow our discussion of respiratory flows by looking at flow resistance & pressure drop along the airway tree. We will consider the design of the lung as an optimal branching structure and its consequences for respiratory diseases.

Week 5. Elements of gas transport in the pulmonary acinus. We will discuss the basic equations for oxygen transport including convective-diffusive equations and so-called Taylor dispersion. We will look at diffusional screening phenomenon in the pulmonary acinus.

Week 6. Air-blood interface in the pulmonary acinus. We will describe the physiological design of lung microcriculation and discuss capillary function in relation to oxygen transfer at the wall-interface between alveolar air and blood.

Week 7. Liquid lining layer dynamics. We will introduce the role of mucus and surfactant covering the airways and discuss (i) surface tension & lung elasticity, (ii) surfactant transport, and (iii) thin film dynamics using lubrication approximation.

PART 2: PARTICLE TRANSPORT & INHALATION THERAPY

Week 8. Transport of inhaled particles (I). We will introduce basic concepts for understanding particle mechanics: (i) Particle size distributions, (ii) Particle motion: sedimentation and drag  (Stokes’ law), as well as the influence multiple particles, wall effects, and particulate systems.

Week 9. Transport of inhaled particles (II). We will continue our discussion of particle transport and discuss : (i) role of diffusion, (ii) hygroscopic growth: particle condensation & evaporation, and other forces (Van der Waals, etc.).

Week 10. Particle-lung interactions (I). We will begin with an overview of (i) particle deposition in the respiratory tract and discussing (ii) the roles of anatomy, tidal volume, and breathing frequency.

Week 11. Particle-lung interactions (II). We will continue our discussion of particle-airway interactions by discussing (i) particle-liquid lining layer interactions, and (ii) retention, clearance, and translocation mechanisms.

Week 12. Inhalation Devices: Design & Strategies (I). We will begin by discussing the therapeutic uses of lung aerosols and introduce (ii) medical devices for aerosol delivery & limitations. We will start by analyzing the basics of jet nebulizers.

Week 13. Inhalation Devices: Design & Strategies (II). We continue our discussion on inhalation devices by looking at: (i) basics of dry powder inhalers (DPI) and (ii) basics of propellant-driven metered dose inhalers (pMDI).

Prerequisites

The course is aimed at advanced Bachelor students (e.g. 4th year) and graduate students, with prior exposure to introductory fluid mechanics and calculus (e.g. partial differential equations). Prior exposure to a physiology course is suggested but not mandatory.

  • 104014 Differential and integral calculus 2t (or similar)
  • 104135 Ordinary differential equations/t (or similar)
  • 334009 Biological Fluid Mechanics (or equivalent course from another department: e.g. 084303, 084311, 034013, 056389,014211,016206
  • recommended (not mandatory): 276011 Body Systems physiology for engineers (or similar)

Teaching Staff

Lecturer: Dr. Josue Sznitman
Email: sznitman@bm.technion.ac.il
Telephone: 04-829-5678
Office hours: To be announced, or call to make an appointment
Office: Julius Silver Building, Room 254
 Lectures: Tuesday, 12:30 – 15:30, Ullman Building, Room 213

Teaching assistant: TBD

Student Evaluation

Homeworks  – 30%

Approx. 1 mandatory homework assignment per week.

The homework is to be submitted individually (but working in pairs or groups is encouraged). The homework can be downloaded from the course website. The due date is one week after they are posted. Homework that is submitted late will not be checked.

Midterm Exam – 30%

1 midterm exam at the end of the first part of the course.

The midterm will cover the first part of the course (and the beginning of the second part), focusing principally on respiratory flows, gas (oxygen) diffusion, and dynamics of lung liquids, and fundamentals of particle transport.

Final Project – 40%

A final project to be approved by instructor.

At the semester start, a list of potential projects will be announced (and posted online). Students will be able to pick their preferred project topic. Projects will be performed in pairs.

Contact Hours per Week

Lecture: 2 Hours

Recitation: 1 Hour

2.5 Credits

Reading Material

  • J. Sznitman, Lecture Notes.
  • J. Bates, “Lung Mechanics”, Cambridge University Press, 2009.
  • W.H. Finlay, The mechanics of Inhaled Pharmaceutical Aerosols, Academic Press, 2001.
  • Y.-C. Fung, “Biomechanics: Motion, Flow, Stress, and Growth”, Springer Verlag, 1996.
  • E.R. Weibel, “The Pathway for Oxygen”, Harvard University Press, 1984.