# Alveolar vs Respiratory Notes

The clearest difference is rating: Alveolar at 5.0 against Respiratory Notes's 4.0. Alveolar also leads on in-app purchases (none vs 1) and ads (none vs shown). Respiratory Notes's advantage is ratings volume (4 vs 1). On price, update cadence and device support there is nothing between them.

Both are free to download. Respiratory Notes sells 1 in-app purchase, starting at $39.99 per year. Alveolar asks for nothing beyond the download.

Alveolar holds the better App Store score, 5.0 against 4.0. Both are backed by a comparable volume of ratings — 1 and 4 respectively.

Alveolar ships an update every 4 months, Respiratory Notes every 6 months. The most recent releases landed on October 15, 2026 and September 30, 2026 respectively.

## The numbers

| Metric | Alveolar | Respiratory Notes |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/alveolar-arterial-a-a-gradient/id996385661/reviews)** | [4.0 (4 ratings)](https://appshunter.io/ios/app/respiratory-notes/id6569241898/reviews) |
| Number of ratings | 1 | **4** |
| Positive reviews | 88.9% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 4 months** | Every 6 months |
| Monetization | **Free** | Free with in-app purchases |
| Size | 16 MB | 47 MB |
| Requires iOS | **8.0** | 13.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 17+ | 17+ |
| Developer | [Satish Deopujari](https://appshunter.io/developer/1180072702) | [Skyscape Medpresso Inc](https://appshunter.io/developer/818609416) |

## What reviewers say

### Alveolar

[App page](https://appshunter.io/ios/app/alveolar-arterial-a-a-gradient/id996385661)

This app calculates the alveolar-arterial oxygen gradient (A-a gradient) and the PaO2/FiO2 ratio. It provides formulas and explanations for these important respiratory measurements, useful for medical professionals and students.

**Highlights:** Alveolar-arterial oxygen gradient calculation, PaO2/FiO2 ratio calculation, Formulas for PAO2 and A-a gradient, Educational explanations of respiratory measurements, Supports room air and variable FiO2

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Respiratory Notes

[App page](https://appshunter.io/ios/app/respiratory-notes/id6569241898)

This app provides a comprehensive, procedure-based reference for respiratory therapy information. It includes illustrations, forms, and algorithms to aid in study and practice, with content organized around protocols and new pulmonary disease tabs. An in-app purchase unlocks all content, and a subscription offers continuous updates.

**Highlights:** Procedure-based format, Supporting illustrations and tables, Fill-in-the-blank forms, Algorithms based on AARC Guidelines, SmartSearch technology, Offline content access

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Respiratory Notes | $39.99 | per year |


## Frequently asked questions

### Is Alveolar free?

Alveolar is free to download, with no in-app purchases.

### Is Respiratory Notes free?

Respiratory Notes is free to download, with in-app purchases available.

### Which has better reviews, Alveolar or Respiratory Notes?

Alveolar is rated higher. Alveolar averages 5.0 out of 5 from 1 ratings, while Respiratory Notes averages 4.0 from 4 ratings.

### Do Alveolar or Respiratory Notes have ads?

Respiratory Notes shows ads; Alveolar does not.

### Which is updated more often, Alveolar or Respiratory Notes?

Alveolar ships an update every 4 months, and Respiratory Notes every 6 months. Most recently, Alveolar was updated on October 15, 2026 and Respiratory Notes on September 30, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*