Physiology of lung

PHYSIOLOGY OF LUNG IN HEALTH

AND ILLNESS

Presented by: Ligi Xavier

Second year MSc nursing

Govt. College Of Nursing, Kottayam

PHYSIOLOGY OF RESPIRATION

inspiration- breathing in..

principle inspiratory muscles- the diaphragm &

external intercostals.

stimulation of diaphragm by the phrenic nerve

diaphragm becomes tenses & flattens

this enlarges the thoracic cavity& reduces its

internal pressure

this force air in to the lungs

other muscles also help-the scalenes fix the first

pair of ribs while the external intercostal muscle lift

the remaining ribs like bucket handles, making

them swing up and out- this also forces air into the

lungs.

deep inspiration – is aided by the pectoralis minor,

sternocleidomastoid, and erector spinae muscles.

expiration- passive process . It is achieved by the

elasticity of the lungs and the thoracic cage- i.e.,

the tendency to return to their original dimensions

when released from tension.

LUNG VOLUMES AND CAPACITIES

Lung volumes and lung capacities refer to

the volume of air associated with different phases

of the respiratory cycle. Lung volumes are directly

measured; Lung capacities are inferred from lung

volumes.

The healthy adult averages 12 respirations a

minute and moves about 6 liters of air into and out

of the lungs while at rest.

CNTD..

tidal volume- the total amount of air moves into and

out of the airways with each inspiration and

expiration during normal quiet breathing.

[vT][500ml]

About 150 mL of it (typically 1 mL per pound of

body weight) fills the conducting division of the

airway. Since this air cannot exchange gases with

the blood, it is called dead air, and the conducting

division is called the anatomic dead space.

Physiologic (total) dead space- is the sum of

anatomic dead space and any pathological alveolar

dead space that may exist. In healthy people, few

alveoli are nonfunctional, and the anatomic and

physiologic dead spaces are identical.

The total volume of air taken in during 1 minute is

called the minute volume of respiration [MVR] or

minute ventilation. It is calculated by multiplying

the tidal volume by the normal breathing rate per

minute.[500×12= 6000ml/mt].

The alveolar ventilation rate [AVR] is the volume

of air per minute that reaches the alveoli.

Inspiratory reserve volume (IRV)[3,000 mL]:-

Amount of air in excess of tidal inspiration that can

be inhaled with maximum effort.

Expiratory reserve volume (ERV)[1,200 mL]:-

Amount of air in excess of tidal expiration that can

be exhaled with maximum effort.

Residual volume (RV)[1,300 mL]:-Amount of air

remaining in the lungs after maximum expiration;

keeps alveoli inflated between breaths and mixes

with fresh air on next inspiration.

Vital capacity (VC)[4,700 mL]:-Amount of air that

can be exhaled with maximum effort after maximum

inspiration (TV + IRV + ERV); used to assess

strength of thoracic muscles as well as pulmonary

function.

Inspiratory capacity (IC)[3,500 mL]:-Maximum

amount of air that can be inhaled after a normal

tidal expiration (TV + IRV).

Functional residual capacity (FRC)[2,500 mL]:-

Amount of air remaining in the lungs after a normal

tidal expiration (RV + ERV)

Total lung capacity (TLC)[6,000 mL]:-Maximum

amount of air the lungs can contain (RV + VC).

PULMONARY FUNCTION TESTS

Pulmonary function tests

Pulmonary function can be measured by having a

subject breathe into a device called a spirometer, which

recaptures the expired breath and records such

variables as the rate and depth of breathing, speed of

expiration, and rate of oxygen consumption. Four

measurements are called respiratory volumes: tidal

volume, inspiratory reserve volume, expiratory

reserve volume, and residual volume. Four others,

called respiratory capacities, are obtained by adding

two or more of the respiratory volumes: vital capacity,

inspiratory capacity, functional residual capacity,

and total lung capacity.

SPIROGRAMS AND FLOW VOLUME CURVES

ALVEOLAR SURFACE TENSION

During breathing, the surface tension must be

overcome to expand the lungs during each

inspiration. It is also the major component of lung

elastic recoil, which acts to decrease the size of

alveoli during expiration.The surface tension of

alveolar fluid is not as great as that of pure water

due to the presence of a detergent-like substance

called surfactant, produced by type 2 alveolar cells.

Surfactant is a complex mixture of phospholipids

and lipoproteins. It lowers the surface tension of

alveolar fluid and thus reduces the tendency of

alveoli to collapse completely.

LUNG COMPLIANCE

It is the measure of the stretchability of lungs

defined as the ratio of change in lung volumes

to change in trans pulmonary pressure.lung

resisting expansion at high volume.

C= V

P

Normal value=200ml/cm of H2o

COMPLIANCE LOOP

it is hysteresis loop in which the inspiratory

compliance is less than that of expiratory

compliance and loop is coming back to the

same point of origin as we trace the compliance

of full one respiration.

RESISTANCE TO AIRFLOW

Flow = change in pressure/resistance (F = AP/R).

Factors affecting

Pulmonary compliance

Diameter of the bronchiloes

VENTILATION PERFUSION RATIO

VA almost equal to 0.8. mismatch usually seen

in pulmonary embolism.

PATTERNS OF BREATHING

Apnea -Temporary cessation of breathing (one or

more skipped breaths).

Dyspnea-Labored, gasping breathing; shortness of

breath.

Eupnoea-Normal, relaxed, quiet breathing; typically

500 mL/breath, 12 to 15 breaths/min.

Hyperpnea -Increased rate and depth of breathing

in response to exercise, pain, or other conditions.

Hyperventilation-Increased pulmonary ventilation in

excess of metabolic demand, frequently associated

with anxiety; expels C02 faster than it is produced,

thus lowering the blood C02 concentration and

raising the pH.

Hypoventilation-Reduced pulmonary ventilation;

leads to an increase in blood C02 concentration if

ventilation is insufficient to expel C02 as fast as it is

produced.

Kussmaul-Deep, rapid breathing often induced by

acidosis, as in diabetes mellitus.

Orthopnea -Dyspnea that occurs when a person is

lying down.

Respiratory arrest-Permanent cessation of

breathing (unless there is medical intervention).

Tachypnea -Accelerated respiration .

GAS EXCHANGE & TRANSPORT

External[pulmonary] respiration-it is the exchange of O2 and CO2 between air in the alveoli of the lungs and blood in pulmonary capillaries. It results in the conversion of deoxygenated blood coming from heart to oxygenated blood.

factors that affect the efficiency of alveolar gas exchange:-

concentration gradient of gases[ie, po2 & pco2]

Solubility of the gases

Membrane area

Ventilation-perfusion coupling.

INTERNAL RESPIRATION

exchange of oxygen and carbon dioxide between

tissue blood capillaries and tissue cells called

internal[tissue]respiration.it results in the conversion

of oxygenated blood into deoxygenated blood.

Oxygenated blood entering tissue capillaries has a

pO2 of 100 mm Hg, where as tissue cells have an

average Po2 of 40 mm of Hg. Because of this

difference , oxygen diffuses from the oxygenated

blood through interstitial fluid and into tissue cells

until the pO2 in the blood decreases to 40 mm of

Hg

While oxygen diffuses from the tissue blood

capillaries to tissue cells, carbon dioxide diffuses in

the opposite direction.

GAS TRANSPORT

1. oxygen- The concentration of oxygen in arterial blood, by volume, is about 20

mL/dL. About 98.5% of this is bound to hemoglobin and 1.5% is dissolved in the blood plasma.

OXYGEN DISSOCIATION CURVE

2. CARBON DIOXIDE-

a] About 90% of the CO2 is hydrated (reacts with water) to form carbonic acid, which then dissociates into bicarbonate and hydrogen ions.

B] About 5% binds to the amino groups of plasma proteins and hemoglobin to form carbamino compounds—chiefly, carbaminohemoglobin (HbCO2).

c] The remaining 5% of the CO2 is carried in the blood as dissolved gas.

ARTERIAL BLOOD GAS ANALYSIS

An arterial blood gas (ABG) test measures the

acidity (pH) and the levels of oxygen and carbon

dioxide in the blood from an artery. This test is used

to check how well lungs are able to move oxygen

into the blood and remove carbon dioxide from the

blood.

ABG VALUES

Partial pressure of oxygen (PaO2):Greater than

80 mm Hg (greater than 10.6 kPa)

Partial pressure of carbon dioxide (PaCO2):35-

45 mm Hg (4.6-5.9 kPa)

pH:7.35-7.45

Bicarbonate (HCO3):23-30 mEq/L (23-30 mmol/L)

Oxygen content (O2CT):15-22 mL per 100 mL of

blood (6.6-9.7 mmol/L)

Oxygen saturation (O2Sat):95%-100% (0.95-

1.00)

PULSE OXIMETRY

A non invasive technolgy to monitor oxygen

saturation of the haemoglobin

wavelength

Extinction

coefficient

660nm 940nm

MetHb

Oxy Hb

Deoxy

HbCOHB

DESIGN OF PULSEOXIMETER

2 Wavelengths-

660nm [red] & 940nm[infra red]

The ratio of absorbencies at these two wavelengths iscalibrated empirically against direct measurements of arterial blood oxygen saturation (SaO2) in volunteers, and the resulting calibration algorithm is stored in a digital microprocessor withinthe pulse oximeter.

Led & photodetector

Newer types of LED is based on aluminium gallium arsenide system

Signal processed in the micro processor

Senses only the pulsatile flow

PaO2 [mmHg] SaO2 [%]

Normal 97 to ≥80 97 to ≥95

Hypoxia < 80 < 95

Mild 60-79 90-94

Moderate 40 – 59 75 – 89

Severe <40 < 75

USES OF PULSEOXIMETRY

Monitoring oxygenation

During anaesthesia

in ICU, PACU

during transport

Monitoring oxygen therapy

Assesment of perfusion

Monitoring vascular volume

Sleep studies -24-h ambulatory recordings of SpO2 isuseful for screening for daytime sleep sequelae associated with the potential risk of this pathology in OSAS during social activities.

DISADVANTAGES

Decrease in PAO2 before fall in SPO2

Due to the shape of ODC

SPO2 94% - PAO2 75%

ADVANTAGES

Simple to use

Non-invasive

Require no warm up time

Especially in African &Asian patients

Cost-effectiveness over ABG

CONTROL OF RESPIRATION

There are four main centers in the brain to regulate

the respiration:

1. Inspiratory center

2. Expiratory center

3. Pneumotaxic center

4. Apneustic center. The first two centers are

present on the medulla oblongata whereas the last

two centers on the Pons region of brain.

DISEASES THAT IMPAIR GAS EXCHANGE

Asthma

Emphysema

Occupational Respiratory Disorders

Tuberculosis

atelectasis.

Adult respiratory distress syndrome (ARDS

Bronchitis

Cystic fibrosis

Lung cancer

Nervous System disorders

Sudden infant death syndrome (SIDS)

Paralysis of the respiratory muscles

Diseases of the Upper Respiratory Tract

Strep throat

Diphtheria

Diseases of the Lower Respiratory Tract

Laryngitis, Whooping cough (pertussis)

pneumonia,influenza

INTERCOSTAL CHEST DRAINAGE

is a flexible plastic tube that is inserted through the

chest wall and into the pleural space or

mediastinum It is used to remove air or fluid

(pleural effusion, blood, chyle), or pus (empyema)

from the intrathoracic space. It is also known as a

Bülau drain

INDICATIONS

Left-sided pneumothorax (right side of image) on CT scan of the chest with chest tube in place.

Pneumothorax: accumulation of air or gas in the pleural space

Pleural effusion: accumulation of fluid in the pleural space

Chylothorax: a collection of lymphatic fluid in the pleural space

Empyema: a pyogenic infection of the pleural space

Hemothorax: accumulation of blood in the pleural space

Hydrothorax: accumulation of serous fluid in the pleural space

Postoperative: for example, thoracotomy, oesophagectomy, cardiac surgery

TECHNIQUE

Tube thoracostomy

The free end of the tube is usually attached to an underwater seal, below the level of the chest. This allows the air or fluid to escape from the pleural space, and prevents anything returning to the chest. Alternatively, the tube can be attached to a flutter valve. This allows patients with pneumothorax to remain more mobile.

British Thoracic Society recommends the tube is inserted in an area described as the "safe zone", a region bordered by: the lateral border of pectoralismajor, a horizontal line inferior to the axilla, the anterior border of latissimus dorsi and a horizontal line superior to the nipple. More specifically, the tube is inserted into the 5th intercostal space slightly anterior to the mid axillary line.

POSTOPERATIVE DRAINAGE

The placement technique for postoperative drainage (e.g. cardiac surgery) differs from the technique used for emergent situations. At the completion of open cardiac procedures, chest tubes are placed through separate stab incisions, typically near the inferior aspect of the sternotomy incision. In some instances multiple drains may be used to evacuate the mediastinal, pericardial, and pleural spaces. The drainage holes are place inside the patient, and the chest tube is passed out through the incision. Once the tube is in place, it is sutured to the skin to prevent movement. The chest tube is then connected to the drainage canister using additional tubing and connectors, and connected to a suction source, typically regulated to -20cm of water.

NURSING MANAGEMENT

Chest drains should not be clamped

Start of shift checks

Patient assessment

Chest drain assessment

Other considerations e.g physiotherapy referral

Patient Assessment

HR, SaO2, BP, RR

Routine vital signs:

Chest tubes are painful as the parietal pleura is very

sensitive. Patients require regular pain relief for comfort,

and to allow them to complete physiotherapy or mobilise

Pain assessment should be conducted frequently and

documented

Observe for signs of infection and inflammation and

document findings

Check dressing is clean and intact

Observe sutures remain intact & secure (particularly long

term drains where sutures may erode over time)

Never lift drain above chest level

The unit and all tubing should be below patients chest level to

facilitate drainage

Tubing should have no kinks or obstructions that may inhibit

drainage

Ensure all connections between chest tubes

and drainage unit are tight and secureSuction is not always required, and may lead to tissue trauma

and prolongation of an air leak in some patients

If suction is required orders should be written by medical staff

Wall suction should be set at >80mmHg or higher

Suction on the Drainage unit should be set to the prescribed

level

Milking of chest drains is only to be done with written

orders from medical staff. Milking drains creates a high

negative pressure that can cause pain, tissue trauma

and bleeding

Volume

Document hourly the amount of fluid in the drainage

chamber on the Fluid Balance Chart

Calculate and document total hourly output if multiple drains

Calculate and document cumulative total output

Notify medical staff if there is a sudden increase in

amount of drainage

greater than 5mls/kg in 1 hour

greater than 3mls/kg consistently for 3 hours

AIR LEAKAGE (BUBBLING)

An air leak will be characterised by intermittent bubbling

in the water seal chamber when the patient with a

pneumothorax exhales or coughs.

The severity of the leak will be indicated by numerical

grading on the UWSD (1-small leak 5-large leak)

Continuous bubbling of this chamber indicates large air

leak between the drain & the patient. Check drain for

disconnection, dislodgement and loose connection, and

assess patient condition. Notify medical staff

immediately if problem cannot be remedied.

Document on Fluid Balance Chart

OSCILLATION (SWING)

The water in the water seal chamber will rise and fall

(swing) with respirations. This will diminish as the

pneumothorax resolves.

Watch for unexpected cessation of swing as this may

indicate the tube is blocked or kinked.

Cardiac surgical patients may have some of their drains

in the mediastinum in which case there will be no swing

in the water seal chamber.

Document on Fluid Balance Chart

Patients who are ambulant post operatively will

have fewer complications and shorter lengths of

stay.

REMOVAL OF THE TUBE

Clinical status is the best indicator of a reaccumulation of air or

fluid. CXR should be performed if patient condition deteriorates

Monitor vital signs closely (HR, SaO2, RR and BP) on removal

and then every hour for 4 hours post removal, and then as per

clinical condition

Document the removal of drain in progress notes and on

patient care record

Remove sutures 5 days post drain removal

Dressing to remain insitu for 24 hours post removal unless

dirty

Complications post drain removal include pneumothorax,

bleeding and infection of the drain site

ASSESSMENT

Client History

Subjective symptoms

Dyspnea with ADLs?

Childhood diseases

Asthma, pneumonia, allergies, croup

Adult illnesses

Pneumonia, sinusitis, TB, HIV, emphysema, DM, HTN,

cardiac disease

Vaccine history

Flu, pneumonia, BCG

ASSESSMENT

Client History

Surgeries of upper or lower respiratory tract

Injuries to upper or lower respiratory tract

Hospitalizations

Date of last

CXR, PPD, PFT

Recent weight loss

Night sweats

PHYSICAL ASSESSMENT

Auscultation

Upright first

Bare chest

Open mouth breathing

Full respiratory cycle

Observe for dizziness

PHYSICAL ASSESSMENT

Lungs and Thorax

Inspection

Palpation

Fremitus

99

Crepitus

Bubble wrap

Chest expansion

Movement

PHYSICAL ASSESSMENT

Lungs and Thorax

Percussion

Pulmonary resonance

Air, fluid, solid masses

Intercostal spaces only

Diagphragmatic excursion

Normal 1 -2 inches

Deep breath / percuss

No breath / percuss

Normally higher on the right (liver)

PHYSICAL ASSESSMENT

Normal breath sounds

Bronchial, bronchovesicular, vesicular

Not heard peripherally

Adventitious breath sounds

Additional sounds superimposed on normal sounds

Indicate pathology

Crackles, wheezes, rhonchi, pleural friction rub

PHYSICAL ASSESSMENT

Skin and Mucous Membranes

Pallor, cyanosis, nail beds

General Appearance

Muscle development, general body build

Muscles of neck, chest

Endurance

How does the client move in 10 – 20 steps?

Speaking exertion

NURSING DIAGNOSES

Ineffective breathing pattern related to:increased rate and decreased depth of respirations associated with fear and anxiety

decreased lung compliance (distensibility) associated with pleural effusion and accumulation of fluid in the pulmonary interstitium and alveoli

diminished lung/chest wall expansion associated with weakness, decreased mobility, and pressure on the diaphragm as a result of peritoneal fluid accumulation (if present)

respiratory depressant and/or stimulant effects of hypoxia, hypercapnia, and diminished cerebral blood flow;

ineffective airway clearance related to:increased airway resistance associated with edema of the bronchial mucosa and pressure on the airways resulting from engorgement of the pulmonary vessels

stasis of secretions associated with decreased mobility and poor cough effort;

impaired gas exchange related to:impaired diffusion of gases associated with accumulation of fluid in the pulmonary interstitiumand alveoli

decreased pulmonary tissue perfusion associated with decreased cardiac output.