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Breathlessness: Clues to look for while making a diagnosis- Dr. YK Amdekar

M3 India Newsdesk Nov 09, 2020

Dr. YK Amdekar delivers practice pearls on ways to approach breathlessness in a patient, stressing majorly on thorough history taking and analysis of causation through minute clues the history may offer.

To read other originals by Dr. YK Amdekar, click here.

Before you begin, take the quiz below to test your knowledge.

Breath refers to air and hence breathlessness is when less air is going into the lungs affecting oxygen delivery to the tissues. Normally, air contains 20% oxygen and volume of air inspired and expired in every breath without extra efforts in a healthy individual at rest amounts to about 6 to 7 ml/kg body weight. It provides adequate oxygen and gets rid of carbon dioxide.

Oxygen concentration is low at high altitudes where even a normal person feels breathless. When oxygen requirements are increased as in the case of physical exercise, a healthy individual can easily compensate to an extent by merely increasing respiratory rate. However, beyond a certain degree, a person has to make extra efforts by using accessory muscles of respiration that normally do not come into play. A time may come when the muscles of respiration get tired and cannot sustain efforts of breathing that may endanger life.

Body’s compensatory mechanisms

Nature has provided mechanisms that can compensate to an extent for increasing needs or disturbed respiratory function. The first step would be to increase respiratory rate. There is a limit to increasing respiratory rate as there has to be enough time to exhale carbon dioxide as well. Normally, expiratory time is 2-3 times of inspiratory time – IE ratio is 1:2 or 1:3. So when respiratory rate cannot be increased any further, nature tries the next step of using accessory muscles of respiration to push in more air at each breath. Intercostal muscles retract in the hope of sucking in air with more power and even smaller muscles contribute to such an effort. It reflects as increased effort at breathing and the person feels uncomfortable and distressed. Concurrently, the heart rate also increases and with increasing respiratory and cardiac activity, oxygen demands also increase resulting in further imbalance.

Increase in heart rate also has limitations as oxygen is supplied to the heart during diastole and there has to be enough time for diastole as well. In normal adults, systolic time is about 60% of diastolic time though in young infants with faster heart rate, systolic and diastolic time may be equal or at times, even systolic time may be more than diastolic time. Initially, by increasing efforts of breathing, oxygen requirements are barely met with, but if disease worsens by then or respiratory muscles get tired, tissues suffer from lack of oxygen and retained carbon dioxide. This stage demands urgent intervention as the body’s available resources have failed.

Effect of lack of oxygen and retained carbon dioxide

Effect of oxygen deficiency and/or retained carbon dioxide are felt by the brain the most, as the brain needs continuous supply of oxygen. Increase in carbon dioxide results in vasodilation of cerebral vessels that causes increase in intracranial pressure and poor cerebral perfusion. It is how the brain gets affected.

The next to suffer is the heart, followed by all other organs. Disturbed gas exchange results in change in pH of blood resulting in acidosis which in turn affects heart function resulting in rhythm disturbances. Heart dysfunction adds to the trouble – typically heart and lungs work together – it is cardiorespiratory system. Disease of one of them affects the other as well.

Common causes of breathlessness

Though diseases of respiratory and cardiac systems predominate in leading to breathlessness, the neurological system also may cause breathlessness as it controls the breathing mechanism. Cardiac disease may originate in the renal system as a result of hypertension and adrenal disease and may also be the cause of hypertension. Similarly, severe anaemia may cause cardiac dysfunction and thus, directly or indirectly, many systems may be involved and the clinician must be aware of it.

It is not uncommon for a patient suffering from acidosis to complain of “breathlessness”. What he really has is simply fast respiratory rate without oxygen deficiency. Acidosis presents as deep and rapid respiration with normal chest findings and oxygen levels. The common respiratory causes include pneumonia, pleural effusion, asthma, chronic bronchitis with emphysema in adults, bronchiolitis in children, interstitial lung disease and upper airway obstruction as in case of laryngitis. Common cardiac diseases in children are congenital heart defects and rheumatic heart disease (less common recently), myocardial diseases more in adults and so also hypertension. Neurological disorders presenting with breathlessness include lower motor neuron diseases such as ascending polyneuritis and polio-like illness. Central nervous disease may affect breathing rate, rhythm and depth but these are not presenting features. Diabetic ketoacidosis present with tachypnea mimicking breathlessness.

Clinical approach

Analysis of detailed history

The first step in the clinical approach is always to define anatomy of the disease- which system is involved? It is often possible to define microanatomy. Thereafter, one should find out pathology, and aetiology is often a guess based on anatomy and pathology.

Age- A young infant in the first three months has a high chance of cardiac disease but in later part of infancy and thereafter, pulmonary diseases are more prevalent.

Origin, duration, progress-

  • Respiratory diseases are often acute with exception of chronic interstitial lung disease
  • Cardiac disorders are chronic with exception of acute myocarditis
  • Asthma is typically episodic and nocturnal

There is a difference between episodic and recurrent. Episode refers to similar presentation at similar time while recurrence may occur at any time.

Accompanying symptoms-

  1. Fever is common in respiratory diseases with the exception of asthma while, cardiac conditions are rarely accompanied with fever.
  2. Cough followed by breathlessness is classical in respiratory disease too, though cough may be absent in bronchiolitis or interstitial lung disease while recurrent cough is feature of heart defect with pulmonary congestion such as left to right shunt in which presence of mild tachypnoea is often overlooked.
  3. Palpitation may be complained by an older child suffering from heart disease and occasionally an observant mother may give a history of rapid precordial movements.
  4. Hypophonia or aphonia in a breathless child suggests paralysis of respiratory muscles.

Often on direct questioning, one can get an idea of abnormal audible respiratory sounds.

  • Stridor, wheeze or grunt denote upper airway inspiratory obstruction, lower airway expiratory obstruction and lung parenchymal disease respectively
  • Hissing sound suggests nasal obstruction

Behavior of the child is an important early indicator of lack of oxygen or retained carbon dioxide. Confusion or irrelevant behavior denotes lack of oxygen while irritability is a feature of hypercarbia.

Physical examination- Nutritional and growth parameters help in differentiating acute from chronic conditions. Degree of breathlessness is evident by presence or absence of chest retractions and accessory muscles in action. Respiratory and heart rate and blood pressure changes offer clue. Generally, a breathless child has tachypnoea and tachycardia, but if tachypnoea is more as compared to tachycardia, it would suggest primary respiratory disease. While, if tachycardia is more as compared to tachypnoea, it denotes cardiac disease.

Hypertension may be due to renal or endocrinal disease and also due to coarctation of the aorta. Behavior change, blood pressure, and pallor if any must be looked for. Chest signs such as restricted movements, change in percussion note, diminished or abnormal breath sounds and foreign sounds denote pulmonary disease while enlarged heart and murmur indicate cardiac disease.

Chest signs may be absent in interstitial lung disease as well as upper respiratory obstruction in laryngitis. Similarly, absence of murmur does not rule out cardiac disease. Cyanosis is a late sign in respiratory diseases while it may be seen in an otherwise comfortable child with cyanotic heart defect.

Paralysis of respiratory muscles are easy to note. Measurement of oxygen concentration by pulse-oximetry is now considered as part of the physical examination as it can detect seriousness early enough to take proper corrective action. In most of the situations, the clinical diagnosis is possible with analysis of detailed history and focused physical examination.


Provisional diagnosis is a must before planning investigations. Tests are only to confirm or rule one or two similar diseases that are considered. Of course, test results must be interpreted in the light of clinical profile. CBC and chest x-ray are useful primary investigations in pulmonary diseases. While chest x-ray and ECG can give some clue to cardiac disease, echocardiogram is much more useful to get accurate information. One may need blood gas analysis in serious situations.


Breathlessness is an emergency where the patient needs hospitalisation, except for an asthmatic who may be relieved of breathlessness in a short time with nebulised drugs. Specific treatment depends on final diagnosis but supportive therapy includes oxygenation, mechanical ventilation and hydration. Cardiac defects need surgical intervention for correction. Neurological disease such as ascending polyneuritis is treated with IV immunoglobulins and may need physiotherapy.

In summary, breathlessness is an emergency requiring immediate resuscitation by oxygenation and further action decided by probable diagnosis. The clinician should be able to pick-up impending breathlessness and plan timely measures so as to avoid worsening. Behavior change is the early manifestation of hypoxemia in acute respiratory diseases. Chronic conditions vulnerable to lead to breathlessness should be closed monitored with timely action.


Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

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