1 December 2009Respiratory Physiology

Lab this week: A case study and measuring lung volumes and

capacities with Powerlab.

Bring calculator and textbook to lab.

About the Final Exam…..

Choice of Tuesday, Wednesday or Friday

Pulmonary arterial blood = low in O2Pulmonary arterial blood = low in O2

Cartilage prevents collapse of airways during expiration.

Figure 22.10

Type I pneumocytes are simple squamous epithelia that comprise the majority of the surface area.

Type II pneumocytes secrete surfactant.

Gas exchange by diffusion based on gradients.

Figure 13.17Who cares? Respiratory Distress Syndrome of the Newborn

Law of LaPlace

Surfactant reduces surface tension which reduces the mechanical effort of ventilation and prevents the collapse of smaller alveoli.

Figure 13.19

At end of normal tidal expiration

Tidal inspiration

V = VT x f

VA = (VT – VDS) x fAnatomic dead space = air remaining in conducting zone (typically 150 ml.)

What is VA if Tidal Volume is 150 ml?

O2 uptake

CO2 production

O2 uptake

CO2 production

= Respiratory Quotient

= 0.8 for proteins= 0.7 for fat= 1.0 for carbohydrates

=0.8 for mixed diet 200 mlCO2/min 250 ml O2/min

Pulmonary Venous blood is equivalent to Systemic Arterial blood.

Alveolar to arterial gradient is due toventilation/perfusion inequality.

Gradient for CO2 is only 6 mmHg;CO2 is more soluble and permeable than O2

Ventilation by Bulk Flow

Gas exchange

Gas exchange

Landmark numbers to memorize.

Matching blood flow (Q, also called “perfusion” ) to ventilation (V) by pulmonary arterioles that constrict in response to low O2 anddilate in response to hi O2

(Note this response to O2 is opposite that of systemic arterioles!)

Thus, poorly ventilated regions of the lung will receive less blood flow.

So…. Q is “matched” to V, but not perfectly.

And low perfusion in a region leads to bronchoconstriction.

Figure 13.27

CO2 and O2 bound to Hb do not contribute to partial pressure (no longer a dissolved gas!)

Table 13.08

Figure 13.31Hb can bindO2, CO2, and H+

Increases in CO2 and H+ decrease the affinity of Hb for O2

FlatSteep

At 40 Torr, more DPG, higher temperature, and greater acidity (all indicative of increased metabolism) shift dissociation curve down (Hb has a lower affinity for O2) and thus more O2 is unloaded into the tissues.

Shifting the Oxyhemoglobin dissociation curve

Notice the main affect is on the steep portion of the curve which means that there is little influence on the loading of O2 onto Hb in the lungs

Table 13.09

Hb is a Buffer

Chloride Shift

carbaminohemoglobin

CA = carbonic anhydrase

Carbon dioxide transport